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#1351264 - 03/19/02 04:27 AM Re: Feel free to ask Myles
Chip McDonald Offline
MP Hall of Fame Member

Registered: 01/19/00
Posts: 4792
Loc: Augusta, Ga. USA
Ok, here's a typically Chip off the wall angle:

Is it possible to make X-rays with a rectifier tube?

If so, is it possible to be receiving lose-doses of x-rays when near tube-rectified amps... ?
_________________________
www.chipmcdonald.com
(tagline inlieu of having a representational page of downloadable music for the moment...) / "big ass windbag" - Bruce Swedien

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GP Island
#1351265 - 03/21/02 06:57 AM Re: Feel free to ask Myles
Seegs Offline
Member

Registered: 03/02/02
Posts: 4
Loc: Sulzbach/Ts.,,GERMANY
I just saw this after I started a thread.

Basically I want to know what does it mean when your power tubes start glowing blue?

Should I be concerned as they only have around ten hours on them? They are new GT 5881 NOS's

Seegs

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#1351266 - 03/21/02 11:53 AM Re: Feel free to ask Myles
steve f Offline
Senior Member

Registered: 03/05/02
Posts: 37
Loc: ,,UNITED STATES
Myles, thanks for giving us the benefit of your experience.

I wanted to get your thoughts on the overall quality of Bogner amps (build quality, components used, etc), the Shiva in particular.

I recently looked at a Soldano HotRod 100+ and wasn't overly impressed compared to my Rivera M100. It sounded fine, but boy, the M100 just seems to have much more attention to detail and the quality of components seems higher. I don't won't to invest a lot of time trying to track down a Shiva if it's not going to have the quality built in like my M100.

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#1351267 - 03/21/02 02:29 PM Re: Feel free to ask Myles
dlb Offline
Member

Registered: 03/07/01
Posts: 10
Loc: Newport,NH,UNITED STATES
Quote:
Originally posted by myles111:
Quote:
Thanks for the reply, It is a 2-10 combo in the stock state except for power tubes which I've experimented with. It has the cascading gain. I deally, I would like to achieve more clean head room in channel 1 (past 3 it breaks up quick)and less of the synthetic gain sound on channel 2. I've read of mods to put master volume pots in the reverb slot and moving reverb pot to back of chassis. That interests me. It is a cool amp but hard to harness in a live situation. This little sucker runs hot as well, I have a good PC fan I am going to stick in it.
First off, don't start doing mods to that amp or you will get a lot more noise in the higher gain states. These amps can be noisy enough unless you hand select preamp tubes.

Have your bias checked! If the amp is over or under biased, you will get all sorts of grainy nonsense down in the range you mention.... especially if the amp is overbiased and running too cool. These amps already start to breakup very quickly in the preamp stages, as that is what they were designed to do, so it is even more critical to have a good output stage after the preamp stage. I would bet, after looking at a number of these, that with your volume set to 3-4, that there is a lot of crossover notch distortion if you scope the amp.

To give you more headroom, you need to have somebody look at your first two preamp tubes to see how much above or below 1.2mA they put out with 250 volts on their plates and a -2v bias. If they are the typical Sovtek/Fender tubes, they are probably putting out more than the spec 1.2mA. The 12AX7 has a gain of about 100, so the difference between 1.2 and 1.3 is pretty dramatic.

You need to find a nice 12AX7, perhaps a 12AX7C, that has maybe 1.0mA output. The other thing you can do here is put a JAN 5751 in the V1 position.

Some good places to get either the JAN or a bit lower powered 12AX7 are Watford Valves, Tubeworld, and KCA NOS tubes. All those folks have links on my website. They are the only folks that have the equipment to measure the qualities you need AND have the tubes you'd want if you go the NOS route.

Then, you need to have your output tubes checked. If they are in a midrange, you'd want them to be at a higher range. Something like, if they are a Groove Tubes 4-5 rating, you'd want them to be a rating of 6-7.

Last, your phase inverter, let me know what is currently in there. It is the preamp tube that is closest to the power tubes. Tell me what it says on the tube, what kind it is, and as much as you can tell me about it. This is a critical tube in this amp, especially when you run the amp Class A, as if this is not balanced on the A/B sides, there will be a lot more heat generated than is already done when the amp is in Class A mode.

When you have the bias checked, find somebody uses a scope if they also use a bias probe. Many folks use a bias probe incorrectly. They might use charts or manuals that say what the correct reading for a particular amp should be, and this is often a bit off as different amps have different B+ voltages. Folks that are more technically advanced, try to figure out their real B+ voltage bu pulling one of the output tubes and taking a reading of the plate pin. This is going in the right direction, and is easier than taking the amp apart, but also gives a false reading. When one output tube is removed, the voltage changes a LOT in many amps. In one Marshall I work on, a 50 watter, it goes from about 450v to about 415v when both tubes are in the amp.

To get the proper B+, ESPECIALLY on a Prosonic, you need to pull the chassis and take the reading off the wired side of the socket with all tubes in the amp. Then you can use a bias probe more effectively.

Regards,

Ok, I finally got around to this. The rectifier tube is a Chinese 5AR4 GZ34 (Fender on it).It has sovtek 12ax7wa's throughout with exception of the reverb tube. It came with sovtek 5881WXT 6L6 power tubes. I have more recently installed Audio Classic 6L6WGB matched set at a 10 rating. It made a bit of clarity difference but took away some warmth. What do you think my next steps should be?
Thanks again!

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#1351268 - 03/21/02 08:22 PM Re: Feel free to ask Myles
dlb Offline
Member

Registered: 03/07/01
Posts: 10
Loc: Newport,NH,UNITED STATES
Quote:
Originally posted by steve f:
Myles, thanks for giving us the benefit of your experience.

I wanted to get your thoughts on the overall quality of Bogner amps (build quality, components used, etc), the Shiva in particular.

I recently looked at a Soldano HotRod 100+ and wasn't overly impressed compared to my Rivera M100. It sounded fine, but boy, the M100 just seems to have much more attention to detail and the quality of components seems higher. I don't won't to invest a lot of time trying to track down a Shiva if it's not going to have the quality built in like my M100.
Myles is certainly the more reliable source for your inquiry but I thought I would lend you my oppinion being a Shiva ownwer. I've had mine for about 8 months now and I feel it has re-inspired my aspirations to be a player. It is very consistant and full of character. It does have the dreaded circuit board plunk dab in the middle of all those quality tubes and transformers but I will add that it too is robust and loaded with industrial quality parts.
As far as the chassis, it is like any good amp. You can only go so far before you create a boat anchor. The cabinet is like most as far as joints and material thickness. It is heavy but worth every carry.
I have other good amps and still use them so my oppinion is not Bogner skewed.
Hope this encourages you.

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#1351269 - 03/21/02 08:46 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by Seegs:
I just saw this after I started a thread.

Basically I want to know what does it mean when your power tubes start glowing blue?

Should I be concerned as they only have around ten hours on them? They are new GT 5881 NOS's

Seegs
Seegs....

No concern, enjoy it!

Some tubes with an open plate construction, or more open than most, let you see the "blue glow" when the B+ is on (amp off standby and ready to play). 6L6B tubes are really great for that.

6L6GE's or 6V6's have so much of the structure encased, that you don't see the blue glow.

I usually turn off the lights where I have amps where you can see the tubes, as I like the blue glow. If it starts to get all red outside the plate structure, then you have problems.

You're just fine. If you peek inside and look at the blue off the plates, you can tell a little bit about the purity of the innards of the tube. Solid blue is great, and some red spots in the blue are impurities. Look in some new tubes and there are a lot more red spots these days. Just an issue of quality.

Regards

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#1351270 - 03/21/02 09:04 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by steve f:
Myles, thanks for giving us the benefit of your experience.

I wanted to get your thoughts on the overall quality of Bogner amps (build quality, components used, etc), the Shiva in particular.

I recently looked at a Soldano HotRod 100+ and wasn't overly impressed compared to my Rivera M100. It sounded fine, but boy, the M100 just seems to have much more attention to detail and the quality of components seems higher. I don't won't to invest a lot of time trying to track down a Shiva if it's not going to have the quality built in like my M100.
steve f -

The Bogner's are very well constructed amps. Look at the solder work, PC boards, and other aspects. There is no reason that their amps won't be around for your grandkids to play as the vintage amps of tomorrow.

Rivera amps are a slightly different story, in a manner of speaking, and your M-100 should not be compared to most other amps. Paul Rivera is something of an anal personality. He does not care if his amps are around for the next 50 years, he wants them to be around for the next ice age or something. If you look at his threaded inserts with machine screws for just the cabinet, it only goes to say that the rest of the amp is built to be a piece of gear in some military battle or something. I guess if you say that Bogner and Demeter are "A" construction, and a Fender amp of the past is a C- (yet they stand the test of time), then a Rivera amps has to be given some weird sort of different classification, such as what we used to use when I was in the marine industry .... Lloyds A1 +++ Most amps output transformers are good up to the amps wattage rating, but in the case of Rivera amps, they are at least double of that. I cannot think of ever seeing a transformer failure on a Rivera product.

Soldano is a bit of a different breed. They use a more minimal approach to construction. They are fine amps, but use more of a Mesa approach to build, with a bit of Crate thrown in on the side (such as output tube sockets mounted with pop rivets). At the last NAMM show, I was told the reason for the pop rivets rather than screws and nuts, were that the pop rivets had a lower profile so oversized tube bases would seat all the way. This makes a degree of sense, but even 6550's and KT-66's are now available with tapered bases which fit normally mounted tube sockets.

Tube sockets can fail at times, and I don't like getting out a power drill to fix an amp.

Just as comparason, Mesa uses self tapping sheet metal screws to mount the tube sockets. My Mk I also has self tapping sheet metal screws to mount the transformers. From time to time I go into the amp and tighten up everything when I start to get a buzz here and there, which for me is no big thing. In the case of the Bogner and Rivera amps, you don't have this little added exercise.

I hope I answered this. In closing though, don't compare other amps to your M-100. Its something like comparing a Bentley Turbo R to a Lincoln. Both nice cars, but different attention to the build of the product.

Regards,

Myles

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#1351271 - 03/21/02 09:53 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES

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#1351272 - 03/21/02 10:14 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by dlb:
Quote:
Originally posted by steve f:
Myles, thanks for giving us the benefit of your experience.

I wanted to get your thoughts on the overall quality of Bogner amps (build quality, components used, etc), the Shiva in particular.

I recently looked at a Soldano HotRod 100+ and wasn't overly impressed compared to my Rivera M100. It sounded fine, but boy, the M100 just seems to have much more attention to detail and the quality of components seems higher. I don't won't to invest a lot of time trying to track down a Shiva if it's not going to have the quality built in like my M100.


Myles is certainly the more reliable source for your inquiry but I thought I would lend you my oppinion being a Shiva ownwer. I've had mine for about 8 months now and I feel it has re-inspired my aspirations to be a player. It is very consistant and full of character. It does have the dreaded circuit board plunk dab in the middle of all those quality tubes and transformers but I will add that it too is robust and loaded with industrial quality parts.
As far as the chassis, it is like any good amp. You can only go so far before you create a boat anchor. The cabinet is like most as far as joints and material thickness. It is heavy but worth every carry.
I have other good amps and still use them so my oppinion is not Bogner skewed.
Hope this encourages you.
dlb -

In case I gave a misleading impression, let me try to be a little more specific.

The Riveras are great amps. The Bogners are great amps. I feel they are built with designs and mechanical engineering that will take either amp into the 22nd century.

As far as the "dreaded circuit board" ... with modern composit materials used in PCB's there is no moisture absorbtion as in older tag boards used in amps of the past (they did not have fiberglass). The wiring traces and runs are optimized for the best response and least noise with a PCB. Some people say it is harder to change parts on a PCB, and this to me is nonsense. I guess I use the correct wattage soldering iron. The consistancy of PCBs is always there, while with point to point wiring, you better hope somebody took the time to really check what they were doing, otherwise there are stray grounding noises and inconsistancy.

A well designed and built amp is just that, regardless of a lot of other factors.

The Bogner Shiva is a wonderful piece of work. It is not as complicated as oen of the other models, which may be an issue to some, and a feature to others. The bottom line with the Shiva is, it is a terrific amp that sounds wonderful and is very versitile, and you can actually carry it and a 2x12 cabinet somewhere, or use the combo version, and not kill yourself.

The Rivera M-100 like I said, is something of a unique amp, and you also have to remember, that they did not make a lot of them, and Paul Sr. probably looked at every one of them.

I think it comes down to personal preference for the sound and features. Either of the amps from Bogner or Rivera will bring you a LOT of trouble free sound with great tone, for decades and decades.

Regards,

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#1351273 - 03/22/02 03:05 AM Re: Feel free to ask Myles
dale661 Offline
Member

Registered: 03/03/02
Posts: 2
Loc: Jena,LA,UNITED STATES
Myles, this is dale661 from the harmony-central forum as well. I've asked you a few questions here and there and you've always given me some pretty good advice. So here goes another question for ya man. Could I put some KT66's in my Mesa Boogie Triple Rectifier 3 channel head? What I'm asking you is would you think there would be enough space? Also, would it be all right for them to be in my amp if they could fit? I read somewhere or another that KT66's draw a lot more heater current or something another like that and it could mess some amps up that weren't designed to handle those loads I guess you could say. Also, if all of that is all right...what kind of tonal differences would these KT66's have from say some JJ 6L6GC's. I'm just curious about all of that. I am probably fixing to hop in the bed. Could you please e-mail me @ GibsonMarshall21@aol.com ? I'd appreciate it Myles. Thanks

Dale

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#1351274 - 03/22/02 02:59 PM Re: Feel free to ask Myles
zero interrupt Offline
Member

Registered: 08/11/00
Posts: 23
Loc: Hempstead,NY,UNITED STATES
Myles,
You responded to a post I had earlier about my Rivera Knucklehead 100. I'm writing to now to troubleshoot. I bought the amp used, so I probably need to change the tubes anyway. I've had the amp for about 2 years and so did the previous owner.
I need a sweet jazz tone and a very tight crunch. I'm not really familiar with changing tubes(although I read thru your site) and I also don't have a manual for the amp head. What preliminary steps do you reccomend I take? Or can you reccomend someone who does blueprinting in the NY Metro area? Thanks. I appreciate any help.

Max
_________________________
the murdersuit is coming...

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#1351275 - 03/22/02 04:03 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by dale661:
Myles, this is dale661 from the harmony-central forum as well. I've asked you a few questions here and there and you've always given me some pretty good advice. So here goes another question for ya man. Could I put some KT66's in my Mesa Boogie Triple Rectifier 3 channel head? What I'm asking you is would you think there would be enough space? Also, would it be all right for them to be in my amp if they could fit? I read somewhere or another that KT66's draw a lot more heater current or something another like that and it could mess some amps up that weren't designed to handle those loads I guess you could say. Also, if all of that is all right...what kind of tonal differences would these KT66's have from say some JJ 6L6GC's. I'm just curious about all of that. I am probably fixing to hop in the bed. Could you please e-mail me @ GibsonMarshall21@aol.com ? I'd appreciate it Myles. Thanks

Dale
dale661 ....

Its hard to jump back and forth in email, so in the future if you want an email response, just send me the question in email format.

The KT-66 has more low end and low mids than other 6L6 family tubes in most amps. Its a great tube, and as far as space, I don't know if they will fit in your amp as I have never tried that. I believe they are 4 5/8" tall, but may be off on that, as that is from memory. On some amps where the fit is tight, you may have to pull the chassis from the cabinet to get enough room to plug them in and out.

The heater current is more with the KT-66. It is 1.27 amps. On a conventional 6L6 it is .9, and on an EL-34 it is 1.5.

Your Mesa has enough reserve that the heater current will not be an issue.

The issue is, will they fit .... and also, with the Mesa's fixed bias, you will need to be sure KT-66's are biased differently, as they are generally a stronger tube than 6L6's, and generally need a bias adjustment. Mesa also does not offer these tubes, so you'd want to be able to experiment with various ranges to try to get your bias in the ballpark. These tubes like current more than voltage, so shoot for an idle dissapation of no more than 55% if using a bias probe type device, or if adjusting with a scope, I like the crossover notch to just be there a touch when the amp is turned up about 60% of the way, rather than the usual 70% or so.

Regards,

Myles

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#1351276 - 03/22/02 05:00 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by zero interrupt:
Myles,
You responded to a post I had earlier about my Rivera Knucklehead 100. I'm writing to now to troubleshoot. I bought the amp used, so I probably need to change the tubes anyway. I've had the amp for about 2 years and so did the previous owner.
I need a sweet jazz tone and a very tight crunch. I'm not really familiar with changing tubes(although I read thru your site) and I also don't have a manual for the amp head. What preliminary steps do you reccomend I take? Or can you reccomend someone who does blueprinting in the NY Metro area? Thanks. I appreciate any help.

Max
Max,

Your amp has pretty easy tube access.

Are the output tubes the originals as supplied by Rivera? If they are, there should be a sticker on the base, blue and silver, with a number. Le me know the number.

At that point, I can tell you what range of other folks tubes you could use, or you can just call Rivera at 818-833-7066 and they can send you a replacement set. If you get tubes in the same range,
then you would not need to rebias your amp.

If they are not the stock tubes, then let me know what they are. Also, if not original tubes, you should probably have the bias checked just to be sure.

As far as preamp tubes, they are interchangable for the most part without any adjustment required. You may want to check on the Rivera website (www.rivera.com) and go to the ROG (Rivera Owners Group) and look for some of their posts. A lot of folks there have great comments and ideas in regard to preamp tubes.

I'd try a 12AX7C (new Chinese 12AX7) in V1, the first preamp tube position, and see how that sounds.

On the Rivera website, there may also be a user's manual available.

I don't know of anybody in your area that does amp blueprinting. I think I am one of the first that do this outside of some high end amp makers that do this for specific customers, such as Dumble on specific amps. There are a lot of great amp techs in NYC though, check with some of the better vintage music stores.

Regards

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#1351277 - 03/22/02 05:16 PM Re: Feel free to ask Myles
zero interrupt Offline
Member

Registered: 08/11/00
Posts: 23
Loc: Hempstead,NY,UNITED STATES
Quote:
Originally posted by myles111:
Quote:


Are the output tubes the originals as supplied by Rivera? If they are, there should be a sticker on the base, blue and silver, with a number. Le me know the number.

If they are not the stock tubes, then let me know what they are. Also, if not original tubes, you should probably have the bias checked just to be sure.

They don't seem to be the original tubes. No blue sticker. This is what is printed on the side of the tube: SVETLANA ELECTRON DEVICES INC
EL34
MADE IN RUSSIA
9804
There is also a stamp to the right of that: OTH55

I'm not sure if the preamp tubes are stock either:
MARSHALL ECC83 is printed on them.

Thanks

Max
_________________________
the murdersuit is coming...

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#1351278 - 03/22/02 09:44 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by zero interrupt:
Quote:
Originally posted by myles111:
Quote:


Are the output tubes the originals as supplied by Rivera? If they are, there should be a sticker on the base, blue and silver, with a number. Le me know the number.

If they are not the stock tubes, then let me know what they are. Also, if not original tubes, you should probably have the bias checked just to be sure.

They don't seem to be the original tubes. No blue sticker. This is what is printed on the side of the tube: SVETLANA ELECTRON DEVICES INC
EL34
MADE IN RUSSIA
9804
There is also a stamp to the right of that: OTH55

I'm not sure if the preamp tubes are stock either:
MARSHALL ECC83 is printed on them.

Thanks

Max
Max,

The Svetlana's are the way to go on that amp in most cases. Those are the tubes Rivera uses in these amps as standard issue.

The preamp tubes are a different story. The ECC83 may make the amp sound too dark, and it will have less gain then the tubes the amp is supplied with.

I would try some inexpensive Sovtek 12AX7WA tubes for a start in the V1 and V2 position if there are ECC83's in there now. If you have the money, replace all the ECC83's with the Sovteks for now. The front end of this amp was set up to use tubes with this sort of gain structure.

Regards,

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#1351279 - 03/27/02 11:01 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Just bumping this for those that missed it.

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#1351280 - 03/28/02 09:18 AM Re: Feel free to ask Myles
semperfi666 Offline
Member

Registered: 03/27/02
Posts: 6
Loc: KRistiansund, NORWAY
Hi Myles!
My rig at the moment:
Digitech 2120, Marshall el34 50/50 and 2 marshall 1960A cabs...
I play mostly metal and my trouble is that I can't get rid of that annoying "ooomph" in the bottom! I have tried to changed the preamp section, messed around with the EQ and dynamics but the bottom is not tight at all.(I do want bass in the sound, but it seem to "crack" up when I crank up the volume...)
I havent tried to changed the tubes in the 2120(out of the box...Vostek I think)
Can someone please help me to get a relly tight sound? You know what I want Limp B, Metallica and that kind of music.
I don't have the cash for a Mesa right now, but I belive I got the hardware to do some of the job...Or?hehe
What tubes should I consider?
I know this sound newbie, but hey- thats what I am
Thanks in advance!
Regards
--------------------------------------------------------------------------------

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#1351281 - 03/28/02 04:08 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by semperfi666:
Hi Myles!
My rig at the moment:
Digitech 2120, Marshall el34 50/50 and 2 marshall 1960A cabs...
I play mostly metal and my trouble is that I can't get rid of that annoying "ooomph" in the bottom! I have tried to changed the preamp section, messed around with the EQ and dynamics but the bottom is not tight at all.(I do want bass in the sound, but it seem to "crack" up when I crank up the volume...)
I havent tried to changed the tubes in the 2120(out of the box...Vostek I think)
Can someone please help me to get a relly tight sound? You know what I want Limp B, Metallica and that kind of music.
I don't have the cash for a Mesa right now, but I belive I got the hardware to do some of the job...Or?hehe
What tubes should I consider?
I know this sound newbie, but hey- thats what I am
Thanks in advance!
Regards
--------------------------------------------------------------------------------
semperfi666 ...

Because of the Digitech, you have a tough issue, as
that is nowhere close to a Marshall preamp front
end.

This is one of the issues that face folks using rack
setups of a sort, when they want to get a sound that
was from a conventional head and cabinets, or a
combo amp.

Changing tubes in the Digitech won't help all that
much either, as the tubes are used more for a bit
of compression, and have only a very small part in
the tone shaping. The tone shaping is done in the
digital realm with lots of little silicon devices
which have a different character.

I'm sorry that I cannot help you here, but your
rig has a specific color of tone that is the product
of what it was intended to do.

Its something like when a Marshall owner tells me
he wants more low mids and lows, and a cleaner sound.
I tell him to go buy a Fender Twin Reverb. Then you
have more sonic bases and colors covered.

Sorry and good luck.

Myles

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#1351282 - 03/29/02 02:08 PM Re: Feel free to ask Myles
evets Offline
Senior Member

Registered: 10/19/01
Posts: 204
Loc: Wilmington, NC UNITED STATES
Myles, thanks for offering your time. I have Marshall JCM2000 (DSL50) head which I intend to use to drive a stereo power amp. I'll be taking the output from the preamp out thus disconnecting the output stage. Since the output stage won't be driven, should I worry about loading it, should I remove the tubes, or should I use a dummy load?
Thanks,
Steve
_________________________
-Steve
-----------------------------------
Sometimes ya gotta find out what it ain't, to find out what it is...

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#1351283 - 03/29/02 03:58 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by evets:
Myles, thanks for offering your time. I have Marshall JCM2000 (DSL50) head which I intend to use to drive a stereo power amp. I'll be taking the output from the preamp out thus disconnecting the output stage. Since the output stage won't be driven, should I worry about loading it, should I remove the tubes, or should I use a dummy load?
Thanks,
Steve
Steve,

Some amps like Rivera amps, turn off the B+ and effectively turn off the power amp section by the use of shorting jacks for the speakers. When there is nothing in the jack, the power amp is off. This is more expensive to do, so most folks don't do this.

In your amp, you need to keep a load on the output section unless shorting jacks are used (which I do not know without looking at prints at the moment) or not.

I would use a load such as a THD Hotplate, which is probably the best unit out there at this time, much better than the Marshall Power Brake from the past that was normally what was used for your sort of application, and a lot less expensive. You could even come off of the THD and then also get the true color of the driven output section, which is a lot nicer than just using the preamp section. You also have the benefit of additional EQ and some other features. Then you come off your preamp out, or effects send, or line out to your rig, and off the THD to a monitor cabinet if you'd like, where you can adjust the level from the THD Hotplate.

Regards,

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#1351284 - 03/29/02 04:41 PM Re: Feel free to ask Myles
evets Offline
Senior Member

Registered: 10/19/01
Posts: 204
Loc: Wilmington, NC UNITED STATES
Thank you for the reply, Myles. I have an old Power Soak (Tom Schloz) which I know is a resistive load, rather than inductive as in the Power Brake. (I'm not familiar with the Hot Plate) Do you discourage the use of a resistive load? (Maybe I just need to invest in a Hot PLate!) Thanks again for your time, and have a great weekend!

Steve
_________________________
-Steve
-----------------------------------
Sometimes ya gotta find out what it ain't, to find out what it is...

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#1351285 - 03/29/02 09:45 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by evets:
Thank you for the reply, Myles. I have an old Power Soak (Tom Schloz) which I know is a resistive load, rather than inductive as in the Power Brake. (I'm not familiar with the Hot Plate) Do you discourage the use of a resistive load? (Maybe I just need to invest in a Hot PLate!) Thanks again for your time, and have a great weekend!

Steve
Steve,

That will work just fine. Eight ohm speakers, as an example have a nominal value of eight ohms at certain frequencies, but will have higher resistance at other frequencies. As long as the amp is working into a load, rather reactive or inductive, it will make no difference, as all you need to do is keep the amp working into a load.

So, if you are not trying to play quietly with your amp running full bore, then the Hot Plate is not needed as what you have will work fine for your application.

Regards

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#1351286 - 03/31/02 08:50 AM Re: Feel free to ask Myles
JamesPeters Offline
Senior Member

Registered: 03/07/02
Posts: 39
Loc: Calgary, Canada
Hey Myles. I just finished my first "production" (non-prototype, professional looking) amp a few days ago. Just figured I'd stop by here to let you know you can check out pics on my site if you like. Later!
_________________________
http://petersamps.com
Handmade tube guitar amps

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#1351287 - 03/31/02 01:28 PM Re: Feel free to ask Myles
Lance-a-not Offline
Member

Registered: 03/03/02
Posts: 12
Loc: Woodstock,GA,UNITED STATES
That looks sweet James, now when can we hear it ?? Very nice!!

Lance

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#1351288 - 03/31/02 03:51 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by JamesPeters:
Hey Myles. I just finished my first "production" (non-prototype, professional looking) amp a few days ago. Just figured I'd stop by here to let you know you can check out pics on my site if you like. Later!
James....

It looks very nice.

What sort of voltage are you running on the B+?

What output tube is the output transformer optimized for?

The only suggestion I have, is tack down some of the wiring with high temp silicone after you figure the best routing for the minimum noise. That way when the amp travels, it will stay quieter when it gets to its destination.

I know point to point wiring is in vogue, but this amp would be a good candidate for a mil-spec circuit board. The trace routing could be developed on computer circuit simulation software which is used by the PCB houses, and you'll end up with a quieter amp that also is consitant from amp to amp once you go into larger scale production. Heavy mil-spec traces which are available from a lot of PCB folks are so thick that they carry more current than most of the wire used today in botique amps.

In any case, it is a very pretty package, and when you look how backordered amps such as the THD items are, there is sure a market for lower powered great sounding amps!

Keep me in the loop, and if you want to send me an email and some text info, I'd be more than happy to put you on my website, as your product is not "middle of the road", is nicely done, and is right in line with the sort of things I like personally.

Once again .... very nicely done.

Now ... what about pricing?

Regards,

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#1351289 - 03/31/02 04:03 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by JamesPeters:
Hey Myles. I just finished my first "production" (non-prototype, professional looking) amp a few days ago. Just figured I'd stop by here to let you know you can check out pics on my site if you like. Later!
James ...

One more thing here.

I looked at your webite at the FAQ's.

There is a point you might want to make, when folks ask about gain with only two preamp tubes. Most amps like a Marshall, have only two stages of gain in reality.

V1 is split into two parts, the A and B side. Same with a Fender amp. Side A is used for one of the inputs, and Side B for the other. It is one stage of gain.

In Fender, V2 is used for the vibrato channel, one side of the tube for each input.

Now, if you run one side of a preamp tube into the other side, what you have is cascaded gain, like a Mesa Boogie Mk. 1 as the originator of that idea. Then you multiply the gain by over 100 depending on the circuit.

Modern amps don't use that same form of gain cascading, it is more of changing the plate voltage from the older Fenderish values of 150v-180v, to higher plate voltages and different bias voltages.

In essence here, the bottom line, is even if your amp only had one preamp tube, depending on the design, you could have more front end gain than any current Mesa Rectifier, Marshall whatever, or most other things.

and .... I still think you are on a great track here, keep up the good work!

Myles

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#1351290 - 03/31/02 08:04 PM Re: Feel free to ask Myles
JamesPeters Offline
Senior Member

Registered: 03/07/02
Posts: 39
Loc: Calgary, Canada
Thanks Myles! Yeah about the preamp tube thing--I just wanted to clear up a basic misconception that was going around, that my amp (in the pictures) couldn't possibly be getting that amount of pregain. I'm going to avoid a more technical explanation, for the sake of not hurting people's brains! \:\)

So, silicone the wires down, you say? Got lots of silicone, no problem there!

As for the board--I don't have any problem leaving it as-is. As it is, the layout is pretty high gain and low-noise (higher gain and lower noise than I had before), and a fair number of components are wired right to the sockets to help keep the noise down. The board itself doesn't take me that long to make; more of the time is spent wiring things to and from it to be honest. Thanks for the suggestion though, because if I ever do get into any kind of steady production I may have to look into that (everything that can save me time will be helpful). I'm also trying not to incur any additional costs at this point, since I have very few orders at this point and I'm dead broke from buying parts (and other things happening in my life right now). With any luck that'll change soon enough; I'm optimistic. \:D

The 3CP1 I'm selling for $480 USD (plus shipping of course), and that's without tubes though. Being that I've had tubes break in shipping before, I'd rather not ship them with the amp. That, and I get no deals whatsoever on tubes, and truth be told it seems that most places in the US seem to sell them for cheaper than here in Canada anyway.

That price, I'm trying to keep that low for the first while anyway. I can forsee the price increasing somewhat (especially if I let a distributor carry it, then I'll have to raise prices to allow their "cut"). I'm going to try to do all the sales myself though, through the Internet or word of mouth...or advertising etc.--I'd really like to be able to offer an amp like this at a very reasonable price.

The output section is honestly optimized for all three tube types--EL34, 6L6/5881, and 6V6. Since I'm using the Hammond 125DSE, I can run 2500 or 5000 ohms on the primary depending on the tap and the secondary load, which works out perfectly for designing the amp around tube data sheet "typical operating conditions" examples. So, with the EL34 or 6L6/5881, I'm using 2500 on the primary, and with 6V6 I'm using 5000 on the primary. The 6L6/5881 also works right within "typical operating conditions" at 5000 ohms on the primary as it turns out, making it the "wild card" tube in this design--it'll work at 4, 8 or 16 ohms whereas the EL34 is only 4/8 ohms, and the 6V6 is only 8/16 ohms. The 6L6 is actually starting to become my favorite tube in this amp.

The bias points for the power tubes are dead-on what's considered to be the "normal operating conditions" for single-ended class A at the B+ the amp runs at (which is 250V), right from tube data sheet examples. The plate voltages are slightly lower when using a 6L6 or EL34 (like maybe 240 or so), and with a 6V6 it runs at an even 250V. I messed around with cathode resistor values to hear what it would sound like biased hotter or colder, and honestly it sounds best for all three tubes right where it is now anyway.

If I run the 6550 in there, it would be really biased cold, but it would run with only a marginal mismatch of the primary impedance compared to "typical operating conditions" mentioned in the datasheet examples (2500 ohms primary instead of the 1500 ohms recommended for that B+). The bias current would be really low, but I know a guy using an AX84 high octane (which I helped him build) who says his is running fine, not drawing more than 65mA plate current (well within spec of the 125DSE), and sounds really neat. I plan to try that out soon too.

Hey, feel free to ask any more questions if you like, or email me directly. I'll get to you later on in the next day or two with stuff for a link from your site--thanks for the offer! I'll link you back too. ;\)
_________________________
http://petersamps.com
Handmade tube guitar amps

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#1351291 - 03/31/02 09:13 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by JamesPeters:
Thanks Myles! Yeah about the preamp tube thing--I just wanted to clear up a basic misconception that was going around, that my amp (in the pictures) couldn't possibly be getting that amount of pregain. I'm going to avoid a more technical explanation, for the sake of not hurting people's brains! \:\)

So, silicone the wires down, you say? Got lots of silicone, no problem there!

As for the board--I don't have any problem leaving it as-is. As it is, the layout is pretty high gain and low-noise (higher gain and lower noise than I had before), and a fair number of components are wired right to the sockets to help keep the noise down. The board itself doesn't take me that long to make; more of the time is spent wiring things to and from it to be honest. Thanks for the suggestion though, because if I ever do get into any kind of steady production I may have to look into that (everything that can save me time will be helpful). I'm also trying not to incur any additional costs at this point, since I have very few orders at this point and I'm dead broke from buying parts (and other things happening in my life right now). With any luck that'll change soon enough; I'm optimistic. \:D

The 3CP1 I'm selling for $480 USD (plus shipping of course), and that's without tubes though. Being that I've had tubes break in shipping before, I'd rather not ship them with the amp. That, and I get no deals whatsoever on tubes, and truth be told it seems that most places in the US seem to sell them for cheaper than here in Canada anyway.

That price, I'm trying to keep that low for the first while anyway. I can forsee the price increasing somewhat (especially if I let a distributor carry it, then I'll have to raise prices to allow their "cut"). I'm going to try to do all the sales myself though, through the Internet or word of mouth...or advertising etc.--I'd really like to be able to offer an amp like this at a very reasonable price.

The output section is honestly optimized for all three tube types--EL34, 6L6/5881, and 6V6. Since I'm using the Hammond 125DSE, I can run 2500 or 5000 ohms on the primary depending on the tap and the secondary load, which works out perfectly for designing the amp around tube data sheet "typical operating conditions" examples. So, with the EL34 or 6L6/5881, I'm using 2500 on the primary, and with 6V6 I'm using 5000 on the primary. The 6L6/5881 also works right within "typical operating conditions" at 5000 ohms on the primary as it turns out, making it the "wild card" tube in this design--it'll work at 4, 8 or 16 ohms whereas the EL34 is only 4/8 ohms, and the 6V6 is only 8/16 ohms. The 6L6 is actually starting to become my favorite tube in this amp.

The bias points for the power tubes are dead-on what's considered to be the "normal operating conditions" for single-ended class A at the B+ the amp runs at (which is 250V), right from tube data sheet examples. The plate voltages are slightly lower when using a 6L6 or EL34 (like maybe 240 or so), and with a 6V6 it runs at an even 250V. I messed around with cathode resistor values to hear what it would sound like biased hotter or colder, and honestly it sounds best for all three tubes right where it is now anyway.

If I run the 6550 in there, it would be really biased cold, but it would run with only a marginal mismatch of the primary impedance compared to "typical operating conditions" mentioned in the datasheet examples (2500 ohms primary instead of the 1500 ohms recommended for that B+). The bias current would be really low, but I know a guy using an AX84 high octane (which I helped him build) who says his is running fine, not drawing more than 65mA plate current (well within spec of the 125DSE), and sounds really neat. I plan to try that out soon too.

Hey, feel free to ask any more questions if you like, or email me directly. I'll get to you later on in the next day or two with stuff for a link from your site--thanks for the offer! I'll link you back too. ;\)
James....

I think this is turning into one of the longer posts, but its a great subject!

First of all, you are on the right track!

On the silicone issue, its just a fast and effective way of keeping some of the longer runs in place.

On the board .... in a smaller production environment, you'll do fine, but if your amp gets the same sort of attention as I think it might, you might want to think of the circuit board idea down the road in the background.

Your price is right on target, considering a store would mark it up 40% or so, and there are offerings that are similar that are in the $995 range.

As far as not shipping with tubes, in an amp like this, there are so many personal choices that can be made, even in one family such as the 6L6 family, that I think that idea is fine. What Steve Carr does on his EL-34 Hammerhead, is ship the tubes in bubble wrap, not installed in the amp.

As far as you getting no deals on tubes, you should. You are an amp manufacturer. There are a few great amp builders who are very limited production such as Kendrick (Trainwreck) and others, that use Groove Tubes as standard equipment. I would think that the folks at Groove Tubes would be willing to give you manufacturing status. I am not sure, but would sure ask them about it. Considering they carry all the various 6L6, 5881, 6550's, EL-34's and 6V6's, as well as all flavors and makers of preamp tubes, they would be a great source. The way they package their tubes is also a lot better than most vendors, if not all of them. Their packaging holds up in tour use for my clients, so for tubes that move around the country, I always use their stuff.

Maybe on Monday, give them a call at 818-361-4500, and ask to talk to Rick Bensen. Tell him we have been talking and I suggested that as an amp maker, I gave you his number and suggested you call him to see if you could get manufacturer prices. Let me know if you need any help with this, as I'd be happy to call him too.

Your output section .... in a word .... or a few .... very very well done !!!

Too many folks go for high plate voltages. Tubes are devices that like current more than voltage. 250 volts is the standard test reference for the folks that make the tubes, and so many amps sound so much nicer when you get that 400-500 volts back down to half of that, and the current goes up instead.

Your impedience matching is right on the money too, and the Hammond is a great transformer, very pretty and musical.

On 6550's, I prefer the Chinese ones, the 6550C, as they have less power than the 6550A, and you can get them to distort easier. They have a softer vacuum than the USA ones. Running them at low plate voltages makes them really sweet. I like a 6550C in a Univalve on its low voltage setting a lot. I also, by the way prefer 6L6's to most other tubes most of the time ... or 6V6's. Maybe its my blues preferences, or when you want massive thick distortion, the 6L6 has more body then the EL-34, while the EL-34 has better articulation and attack at those sorts of levels.

In any case, keep up the good work, give Rick a call, and I'll talk to you soon.

Regards,

Myles

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#1351292 - 03/31/02 09:42 PM Re: Feel free to ask Myles
JamesPeters Offline
Senior Member

Registered: 03/07/02
Posts: 39
Loc: Calgary, Canada
Thanks for the tip Myles, and for the props! \:\) I'll have to ask about any discounts I can get for tubes...but somehow I doubt I'm going to get any special treatment just yet. Noone really knows me yet, so it's not like I'm some really famous amp guru that they'd already know about. I'll still ask them though--hopefully those discounts won't involve having to buy in large quantities (because I still can't afford to do that, at least not yet).

Yeah, once I heard the amp at 250V B+ I knew that was part of the sound. The higher powered one coming soon (3CP2) will stick to 250V B+, which made my transformer choices a little narrower...but I'm not going any higher in B+ if I can avoid it. I'll do 1500 on the primary parallel class A, which will do: 2 x EL34, 2 x 6L6, or 1 x 6550.

Another bonus of sticking with that low a B+ is that all my components, wires, etc. are much higher rated than what they need to be--part of my concern with the amps was to keep the design "bulletproof", and this helps a lot.
_________________________
http://petersamps.com
Handmade tube guitar amps

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#1351293 - 04/01/02 03:53 PM Re: Feel free to ask Myles
myles_rose Moderator Offline
MP Hall of Fame Member

Registered: 11/28/01
Posts: 5036
Loc: Los Angeles CA, UNITED STATES
Quote:
Originally posted by JamesPeters:
Thanks for the tip Myles, and for the props! \:\) I'll have to ask about any discounts I can get for tubes...but somehow I doubt I'm going to get any special treatment just yet. Noone really knows me yet, so it's not like I'm some really famous amp guru....
JamesPeters...

There are a lot of folks out there that just built a few amps a year (Dumble), or make amazing amps on a very limited scale where their names are not household names (Kendrick) .... so I think you'd still be able to meet their (Groove Tubes) criteria as a manufacturer. I'd give it a try.

Myles

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