Feel free to ask Myles

[myles_rose]

Originally posted by TieDyedDevil:

Originally posted by myles111:

Originally posted by TieDyedDevil:

Myles --

 

Man, this Vibro-King is tough on tubes! I'm having a hard time finding a 12AX7 that can survive the vibration in V2 - the reverb recovery slot. The original GT-labelled Sovtek 12AX7WA and a new Svetlana 12AX7 both went microphonic within a matter of hours.

 

I'm thinking that a JAN 5751 might be a bit more rugged. What do you think? Is there anything else I should try?

TieDyedDevil ...........

 

There is something wrong here, as this is normally not a problem.

 

Is your amp one that uses a 6V6 or EL-84 in the reverb circuit?

 

If it is an EL-84, loose the stock tube and replace it with an EL-84S in a #4 or #5 rating.

 

The Svetlana 12AX7 is perhaps, the most unreliable 12AX7 made today, in any part of any circuit, so the stock tube may have had a problem initially, but the Svet surely added it's own problem.

 

Another 12AX7 of any type, if tested well, will work fine. That is one reason alone to try something like a GT 12AX7C, which works great in this area and is guaranteed to be microphonic free for six months.

OK, I'll lose the Svet and see whether I can get a warranty replacement for the Fender GT 12AX7 that came with the amp. And I'll pick up a spare 12AX7C to keep in the gig bag.

 

This is a new Vibro-King, so it uses the 6V6 reverb driver. The stock driver tube seems reasonably quiet, but I suppose it wouldn't hurt to keep a spare for that one, too.

That tube is normally pretty reliable.

[myles_rose]

Originally posted by Blue Note:

Myles,

 

I finally am getting around to retubing my Marshall, it is a dual channel with reverb JCM 800 model 2210. I would like your preferences on both the pre-amp and power tubes. This amp came from Marshall with 6550's which I had converted to EL-34's back in 1991 at a amp shop in New Jersey. Even though the amp tech disagreed I insisted on using Groove Tube pre-amp GT-12AX7's and GT El-34 power tubes and also using only two power tubes instead of four to lower the overdrive volume of the power tubes. The only new tubes I have is some sovtek EL-34WXT's that I bought about six years ago and the guy sold them to me then at a discount because he said they had them forever. I don't know exactly how old they are but the box they are in is turning yellow and even though I don't have it with me right now I think they both had a sticker on the box with 370 wrote on it so I assume they are a somewhat matched pair. I know this is not a lot of info but do you think these tubes are any good. Also I noticed the "GT-12AX7" is not available any more I think its only GT-12AX7R, or GT-12AX7C. The GT-12AX7's really have not been played a whole lot and thought these may still be better than any new ones available today. But then again these tubes may have not been tested to be a matched Driver tube. The reason I think the amp needs retubed is evidently the amp tech in New Jersey had the amp very much under biased because the GT label paint is burned to the point it has even flaked off and I think this means they have been running to hot. Also I think I remember you suggesting to get a true Marshall sound the amp needs to have just a hint of crossover notch still on the scope. Do I remember correctly?

 

Thank's again for your help and expertise,

 

Blue Note.

Blue Note...

 

On my preferences for preamp and power tubes for the JCM 800, it is pretty easy .... V1-V3 ECC83s with V1 and V2 being 100/108 or so, and V3 being a matched phase inverter.

 

The power tubes, well, there are two routes ... 25 watt tubes as originally (and in that case, I like the Svetlana prior to 2002 date code, or ones that have been tested dynamically ONLY), or NOS if you have the money. Mesa Boogie sells some Siemens NOS EL-34 tubes called the STR 450 I believe, at about $70 a matched pair, a great deal, if they still have them.

 

If you want to go the 30 watt tube route, then there is only one choice, the E34LS, and that tube is done on tooling owned by GT and only sold by GT.

 

If you email me at techsupport@groovetubes.com I will send you a 20 or so page document on tube selection and it is also something of a tube primer with a lot of info. This gives characteristics of most of today's new tubes, and a lot of NOS ones too.

 

Do not do the 1/2 power tube deal on these amps, it does not make the amp into a 50 watt amp, it actually makes the amp cleaner at normal levels. I have info on this on my website.

 

On the GT 12AX7 and EL34 tubes, there are a lot of different ones, so it is hard for me to know which of them you are using.

 

The old GT-12AX7 may have been American or Chinese, I'd need to see the tube to be sure.

 

If the paint on the output tubes is darkened, even if not BROWN, they are running WAY too hot, and your amp is not biased properly.

 

You need some notch, but if you send me your B+ voltage, I will tell you a great range to set the ID in milliamps in for this amp.

[jaycee22]

Hey Myles!

 

First of all thanks a bunch for the prompt email reply and the tube primer. Great stuff! I have a couple more questions about my Deluxe Reverb:

 

-When you say pull V1, you mean to remove the first tube?

 

-What kind of tools would I need to check and set the amp's bias myself?

 

Thanks again, and sorry if the questions seem dumb - I'm new to this...

[myles_rose]

Originally posted by jaycee22:

Hey Myles!

 

First of all thanks a bunch for the prompt email reply and the tube primer. Great stuff! I have a couple more questions about my Deluxe Reverb:

 

-When you say pull V1, you mean to remove the first tube?

 

-What kind of tools would I need to check and set the amp's bias myself?

 

Thanks again, and sorry if the questions seem dumb - I'm new to this...

jaycee22 ...........

 

Don't fret on the questions .... that's how you pick up info

 

V1 in your amp, facing the back, is the right most tube, the tube that is the most FAR from the output tubes, and the one the most close to the first input jack.

 

To bias, these amps are pretty easy. You get a bias tool or bias rite, bias king, bias probe, etc. .... lots of folks make them. I prefer the ones that do not have their own meter, because if the meter fails, the tool is useless. It is also nice to have a meter anyway, as it is needed for other aspects of amp work. The ones without the meter also fit easier in my toolbox.

 

The ones GT makes are all on the page at:

 

http://www.groovetubes.com/groovetoys.cfm?Category_ID=30

 

On your amp, there is an access hole on the underside of the chassis, so to access the bias pot, one does not even need to pull the chassis.

 

Doing a bias adjustment on your amp takes a few minutes.

 

If you get a bias tool, just give me a call if you have any questions when you are ready to adjust. The toll free number here is 1-800-459-5687. It does not matter if you buy a GT tool, or anybody elses, I don't care, and I will still be happy to step you through this on the phone ... although most of these tools have pretty good documentation.

 

Good luck. You have an amp that is one of the classics of all time.

[Blue Note]

Myles,

 

Thanks again for your help, I am trying to locate the tubes you suggested but no luck as of yet. As far as the B+ voltage I'm not real sure where to measure this, is their a certain pin# on the tube socket that would give me this and is this in reference to ground. Also as far as dialing in with milli-amps do I put my meter in series with the bias circuit for each tube? if so can I just unsolder the wire from the tube socket and place meter between wire and socket. I don't have one of the milliamp bias probes but will get one if just placing a meter in series will not work.

 

Thanks again and I plan on contacting you also at GT about the SAG-MHG kit. I am really enjoying the tube report I think it's great you are willing to share what had to take a lot of time and effort with everyone.

 

Later,

Blue Note

[myles_rose]

Originally posted by Blue Note:

Myles,

 

Thanks again for your help, I am trying to locate the tubes you suggested but no luck as of yet. As far as the B+ voltage I'm not real sure where to measure this, is their a certain pin# on the tube socket that would give me this and is this in reference to ground. Also as far as dialing in with milli-amps do I put my meter in series with the bias circuit for each tube? if so can I just unsolder the wire from the tube socket and place meter between wire and socket. I don't have one of the milliamp bias probes but will get one if just placing a meter in series will not work.

 

Thanks again and I plan on contacting you also at GT about the SAG-MHG kit. I am really enjoying the tube report I think it's great you are willing to share what had to take a lot of time and effort with everyone.

 

Later,

Blue Note

Blue Note .........

 

Pin #3 is B+. It is best to measure from the bottom of the socket with all tubes in the amp and running. Pulling a tube to measure B+ from the top of the socket will give a false high reading, in some amps as much as 60 volts.

 

You should not put the meter in series with the bias circuit. USA A BIAS TOOL.

[steve f]

Myles,

 

Any experience with Sovtek 6L6WXTs as far as reliability at higher plate voltages?

 

I was told they're not reliable over 450 volts. I know Peavey ships them in their XXX & 5150 and I know Soldano uses the Sovtek 5881WXT in amps that have plate voltages around 500. I'd think the 6L6WXT would hold up at least as well as the 5881.

 

I'm not really a fan of a lot of the Sovtek tubes, but I've been playing around with a Peavey XXX and these actually sound pretty good to my ears in the XXX.

[myles_rose]

Originally posted by steve f:

Myles,

 

Any experience with Sovtek 6L6WXTs as far as reliability at higher plate voltages?

 

I was told they're not reliable over 450 volts. I know Peavey ships them in their XXX & 5150 and I know Soldano uses the Sovtek 5881WXT in amps that have plate voltages around 500. I'd think the 6L6WXT would hold up at least as well as the 5881.

 

I'm not really a fan of a lot of the Sovtek tubes, but I've been playing around with a Peavey XXX and these actually sound pretty good to my ears in the XXX.

Steve,

 

These tubes hold up well, and are robust. I have seen them run pretty nicely even at 515 B+.

 

Sonically, there are many other tubes I prefer.

 

If you email me at techsupport@groovetubes.com and ask for a copy of my tube primer and section guide, I will be happy to send that as an attacment. It may give you a few additional ideas.

[PBBPaul]

Myles,

 

I just picked up a 1965 AB763 Bandmaster. What do advise for getting the most possible warm, clean headroom out of it? The tubes that came with it were all shot (probably during shipping) so I just put in some that I had laying around and even with those, it sounds amazing. Dead quiet all the way to 10 (after a good cleaning). Anyway, I'd like to replace the '70s Bassman that's the center of my rig now with this amp so I'd like to get the most output possible without sacrificing the tone.

 

Thank you,

 

Paul

[Blue Note]

Myles,

 

I got some of the Siemens STR 450's on the way from Mesa-Boogie for my JCM 800 dual channel with reverb model 2210, the tech service guy said even though they are not sold as matched quads (only duets) that if I ordered them all at the same time they would be matched, sounds kind of questionable but I'll give it a try.

 

About the B+ voltage do I need to measure this with the new STR 450's or could I measure that with the tubes I currently have. They said it would be about a week and a half before I got them.

 

When I order the SAG-MHG kit from GT is it important to get two new tubes for the reverb circuit, if so what do you recommend.

 

I am planning on ordering the bias tool also with my order from GT, I know there are other bias tools available is this the one you would buy?

 

Thanks again for Your help!!!

 

Blue Note

[steve f]

Myles,

 

Just to doublecheck my memory, did you say the Groove Tubes KT66-HP should be biased as a 25 watt tube?

[myles_rose]

Originally posted by PBBPaul:

Myles,

 

I just picked up a 1965 AB763 Bandmaster. What do advise for getting the most possible warm, clean headroom out of it? The tubes that came with it were all shot (probably during shipping) so I just put in some that I had laying around and even with those, it sounds amazing. Dead quiet all the way to 10 (after a good cleaning). Anyway, I'd like to replace the '70s Bassman that's the center of my rig now with this amp so I'd like to get the most output possible without sacrificing the tone.

 

Thank you,

 

Paul

Paul ....

 

If you want was the original tone, and want to use what a lot of folks think is the best current 6L6 tube (see the reviews there), then the USA 6L6GE that we make would fit the bill.

 

For lots of clean headroom, go with a #7 or #8.

 

http://www.groovetubes.com/product.cfm?Product_ID=1713

[myles_rose]

Originally posted by Blue Note:

Myles,

 

I got some of the Siemens STR 450's on the way from Mesa-Boogie for my JCM 800 dual channel with reverb model 2210, the tech service guy said even though they are not sold as matched quads (only duets) that if I ordered them all at the same time they would be matched, sounds kind of questionable but I'll give it a try.

 

About the B+ voltage do I need to measure this with the new STR 450's or could I measure that with the tubes I currently have. They said it would be about a week and a half before I got them.

 

When I order the SAG-MHG kit from GT is it important to get two new tubes for the reverb circuit, if so what do you recommend.

 

I am planning on ordering the bias tool also with my order from GT, I know there are other bias tools available is this the one you would buy?

 

Thanks again for Your help!!!

 

Blue Note

Blue Note....

 

Matched duets can be pretty far from each other, so you may want to have them checked for sure. Hopefully they are close, within 10% in current draw. If not, then you will have less than optimal performance and sustain, as your output section will not be balanced. Be sure to use one duet in the inner pair and the other for the two outmost tubes.

 

You can measure B+ with any working tubes. You just need to make sure there are tubes in all the sockets, as an EL-34 has load, and it's heater current draw alone is 1.5 amps.

 

No .... reverb tubes are current drivers, and not part of the tone and/or gain stage. If your reverb works and is not noisy, then save your money and take your significant other out to dinner.

 

I prefered the GT bias tool long before I came to GT. It does not have an attached meter, so needs no batteries. The meter cannot fail, as there is none, it is light and compact, fits in any toolbox, and reliable. I always like a seperate meter anyway, as it is used for so many other things. It also costs 1/2 than the versions with the built in meter.

 

In the end, they all work fine and dandy, and in the same manner, so it is personal taste.

[myles_rose]

Originally posted by steve f:

Myles,

 

Just to doublecheck my memory, did you say the Groove Tubes KT66-HP should be biased as a 25 watt tube?

Steve .....

 

Your memory is right on .... I bias them as 25 watters.

[jaycee22]

Hi Myles,

 

Me again! Few more questions regarding getting the most out of my 69 Deluxe Reverb:

 

-You recommended a good NOS 7025 for V2. Did you mean specifically a 7025, or is that a catchall term including 12AX7s?

 

-What do you think of Brimar 6V6GTYs?

 

-I have the original Oxford speaker for this amp but it needs reconing, and I read somewhere that the Oxfords in DRs aren't the best. Is that true?

 

As always, thanks a bunch.

 

PS - I pulled V1 as per your advice and - voila! - richer, more textured overdrive on the second channel. Danke!

[myles_rose]

Originally posted by jaycee22:

Hi Myles,

 

Me again! Few more questions regarding getting the most out of my 69 Deluxe Reverb:

 

-You recommended a good NOS 7025 for V2. Did you mean specifically a 7025, or is that a catchall term including 12AX7s?

 

-What do you think of Brimar 6V6GTYs?

 

-I have the original Oxford speaker for this amp but it needs reconing, and I read somewhere that the Oxfords in DRs aren't the best. Is that true?

 

As always, thanks a bunch.

 

PS - I pulled V1 as per your advice and - voila! - richer, more textured overdrive on the second channel. Danke!

jaycee22 (Danke)....

 

I meant an actual 7025, as they are a different version of a 12AX7 in some cases, but the NOS ones were truly different and the original tubes in this amp. They are bright though, which was something of a Fender trademark.

 

The Brimar 6V6 tubes are really nice. It is more of a personal preference thing really, but they are nice tubes in the DR.

 

I like Oxfords .... The Jensens, CTS, and Utahs were all nice too. I'd try to keep that speaker, just have it reconed. It is a nice speaker and they are getting pricy, even reconed.

 

Pulling V1 is a cool old trick!

[milobender]

Hi Myles,

 

Is establishing the correct bias really as easy as using Ohms Law? ie. (Wattage rating of power tube / plate Voltage = Amperage) * 70%

 

So for example - EL34 = 25 watt tube and my plate voltage reads 430 volts

 

((25/430)= .0581)*.7 = 40.7ma

 

Also I'm trying some NOS 5751s in the TBR-1M V1 and V2... it's hard to be objective... every different combination has it's strengths and weaknesses. It's like having a number of great instruments, not better or worse, just different... but you can only have one at a time!

 

Brian

[myles_rose]

Originally posted by milobender:

Hi Myles,

 

Is establishing the correct bias really as easy as using Ohms Law? ie. (Wattage rating of power tube / plate Voltage = Amperage) * 70%

 

So for example - EL34 = 25 watt tube and my plate voltage reads 430 volts

 

((25/430)= .0581)*.7 = 40.7ma

 

Also I'm trying some NOS 5751s in the TBR-1M V1 and V2... it's hard to be objective... every different combination has it's strengths and weaknesses. It's like having a number of great instruments, not better or worse, just different... but you can only have one at a time!

 

Brian

milobender (Brian)

 

You are totally correct in your calculations .... that is easy if you understand Ohms Law as you do.

 

On your take on different tubes ... yup .... not better or worse, just different! Don't go too nuts here ... it is easy to end up with a half a dozen "V1" tubes for a single amp ... one for this song, one for this room, one for this venue, one for the Strat, one for the Les Paul, and .... then you spend more time swapping tubes than playing!

[milobender]

Originally posted by myles111:

Originally posted by milobender:

Hi Myles,

 

Is establishing the correct bias really as easy as using Ohms Law? ie. (Wattage rating of power tube / plate Voltage = Amperage) * 70%

 

So for example - EL34 = 25 watt tube and my plate voltage reads 430 volts

 

((25/430)= .0581)*.7 = 40.7ma

 

Also I'm trying some NOS 5751s in the TBR-1M V1 and V2... it's hard to be objective... every different combination has it's strengths and weaknesses. It's like having a number of great instruments, not better or worse, just different... but you can only have one at a time!

 

Brian

milobender (Brian)

 

You are totally correct in your calculations .... that is easy if you understand Ohms Law as you do.

 

On your take on different tubes ... yup .... not better or worse, just different! Don't go too nuts here ... it is easy to end up with a half a dozen "V1" tubes for a single amp ... one for this song, one for this room, one for this venue, one for the Strat, one for the Les Paul, and .... then you spend more time swapping tubes than playing!

I know Myles, but it's cheaper than buying multiple amplifiers! (Now that's what I really want, a Univalve, Victorialux, Twin, ...) Actually, I'm just in the learning phase... so I'm going "mildly" nuts though it's true, I have the urge for each different guitar. I'm really close to having the current "sound-in-my-head" realized. It seems to be pretty unconventional from what I've read:

V1 RCA JRC 5751WA , V2 GE JG 5751, V3 Sovtek WB, V4&5 EH, and V6&7 Sylvania JAN 5814A. The volumn suffers a bit, but it really gets close to the sound I'm after! I've just purchased a couple of RCA 12ax7s to try, and I might try a Tung Sol 5751... but then I'm done for the rest of the year.

 

Thanks for your help; the bias business is really simple and straight forward.

 

Brian

[myles_rose]

Originally posted by milobender:

Originally posted by myles111:

Originally posted by milobender:

Hi Myles,

 

Is establishing the correct bias really as easy as using Ohms Law? ie. (Wattage rating of power tube / plate Voltage = Amperage) * 70%

 

So for example - EL34 = 25 watt tube and my plate voltage reads 430 volts

 

((25/430)= .0581)*.7 = 40.7ma

 

Also I'm trying some NOS 5751s in the TBR-1M V1 and V2... it's hard to be objective... every different combination has it's strengths and weaknesses. It's like having a number of great instruments, not better or worse, just different... but you can only have one at a time!

 

Brian

milobender (Brian)

 

You are totally correct in your calculations .... that is easy if you understand Ohms Law as you do.

 

On your take on different tubes ... yup .... not better or worse, just different! Don't go too nuts here ... it is easy to end up with a half a dozen "V1" tubes for a single amp ... one for this song, one for this room, one for this venue, one for the Strat, one for the Les Paul, and .... then you spend more time swapping tubes than playing!

I know Myles, but it's cheaper than buying multiple amplifiers! (Now that's what I really want, a Univalve, Victorialux, Twin, ...) Actually, I'm just in the learning phase... so I'm going "mildly" nuts though it's true, I have the urge for each different guitar. I'm really close to having the current "sound-in-my-head" realized. It seems to be pretty unconventional from what I've read:

V1 RCA JRC 5751WA , V2 GE JG 5751, V3 Sovtek WB, V4&5 EH, and V6&7 Sylvania JAN 5814A. The volumn suffers a bit, but it really gets close to the sound I'm after! I've just purchased a couple of RCA 12ax7s to try, and I might try a Tung Sol 5751... but then I'm done for the rest of the year.

 

Thanks for your help; the bias business is really simple and straight forward.

 

Brian

Brian,

 

You are more than welcome.

[Shawners]

Whats up Miles,

I've been reading your post for over a year and really appreciate your passion and time you put into your post and replies.

I have a MESA NOMAD 45 4X10 combo.I really love my amp.A little over a year ago I had Bob at Eurotubes( what a awesome guy) pick out new power tubes and preamp tubes w/ a balanced PI.I told him I wanted a 80's metal sound w/ great grind , sustain , more useable gain that didn't turn to mud, harmonics to leep off the fret board and better/tighter bass.Since Mesa's have a fixed biased , he choose tubes that were matched and would raise my bias.It was a really nice improvement , not drastic like i was hoping, but still a noticeable improvement.The JJ's did darken the tone..not bad , just different.I was hoping you might have some good advise and expierience with this amp.It is using 4x el84s' , and 5x 12ax7s' (now JJ's 83s's).I did change v1 after the JJ went microphonic with Grove 12ax7. That helped brighten the sound a little.I'm ready to swap out all my tubes again , my power tubes are difently starting to act -up , and my pre amp tubes are starting to get microphonic and noisey.

I talked w/ a Mesa Tech and he said he had great success w/ the Harma power tubes from WATFORD, whats your take on these.Is there a good American supplier for these tubes.

Any comments / suggestions from your expertise will be most appreciated.....Thanks again Miles.

Your friend Shawners

[myles_rose]

Originally posted by Shawners:

Whats up Miles,

I've been reading your post for over a year and really appreciate your passion and time you put into your post and replies.

I have a MESA NOMAD 45 4X10 combo.I really love my amp.A little over a year ago I had Bob at Eurotubes( what a awesome guy) pick out new power tubes and preamp tubes w/ a balanced PI.I told him I wanted a 80's metal sound w/ great grind , sustain , more useable gain that didn't turn to mud, harmonics to leep off the fret board and better/tighter bass.Since Mesa's have a fixed biased , he choose tubes that were matched and would raise my bias.It was a really nice improvement , not drastic like i was hoping, but still a noticeable improvement.The JJ's did darken the tone..not bad , just different.I was hoping you might have some good advise and expierience with this amp.It is using 4x el84s' , and 5x 12ax7s' (now JJ's 83s's).I did change v1 after the JJ went microphonic with Grove 12ax7. That helped brighten the sound a little.I'm ready to swap out all my tubes again , my power tubes are difently starting to act -up , and my pre amp tubes are starting to get microphonic and noisey.

I talked w/ a Mesa Tech and he said he had great success w/ the Harma power tubes from WATFORD, whats your take on these.Is there a good American supplier for these tubes.

Any comments / suggestions from your expertise will be most appreciated.....Thanks again Miles.

Your friend Shawners

Shawners ......

 

Your amp is a really nice one, and Bob at Eurotubes knows Mesa amps very well, so I am not too surprised that you are happy.

 

Mesa amps are typically overbiased, and tend to run a bit on the cold side. Bob also knows this, so he specifically selects tubes in a current range that improves (at least to my thinking) the tone of Mesa amps ... any of them.

 

The JJ's can be a bit darker in tone in some amps. Many of my own clients use 12AX7R3 tubes for a bit more brightness. They are not as bright as an R2, but a bit more bright than an ECC83.

 

The JJ tubes can go microphonic, as the Mesa amps use pretty high plate voltages on the preamp tubes. This makes them run hot, and each turn on and turn off of these amps, is a heating and cooling cycle, that compresses the mica spacers, making them more loose with each cycle. It takes some pretty sophisticated stuff to try to guarantee against this sort of thing. These Mesa amps can be very hard on preamp tubes, so this is not really a fault of the tube, or of Eurotubes ... just one of those things that happen. You could use another ECC83 as an example, and have the problem sooner, or never ... it is a roll of the dice. If you get tubes from a vendor that has at least a 90 day warranty that INCLUDES not just tube failure, but failure from tubes becomming ... and I repeat ... BECOMMING noisy or microphonic, then you are in good company.

 

The HARMA tubes from Watford are nice, but they are really just very closely selected tubes that have better specs and a lower noise floor.

 

Without trying to push our own products here, I will point out that GT has an extensive line of all these tubes, and carry a six month full warranty. If you email me at techsupport@groovetubes.com ... I will send you a 20+ page tube document I wrote, showing how all these compare sonically and quality wise.

[Shawners]

Thanx for the quick reply. What have some of your blueprinting customers w/ the nomad series liked or do you have any personal preferences?

Does the GT site just sell GT's or can I order NOS tubes also ?Thanx again miles...Shawners

[Altered Fifth]

Hi Myles,

Two questions, the first is more generic:

When swapping tubes in an amp to compare tones, is it necessary to always turn off the amp before pulling or replacing the tube? Can you safely do a "hot swap?" If the amp has a standby switch would this help?

 

The second question is more specific:

I play straight-ahead jazz and have recently purchased a Fender Blues Jr., which I am looking to upgrade. Rather than the standard Polytone jazz sound, I'm after a tone more like a cross between Kenny Burrell and SRV. I play a PRS Archtop with the volume down between 4-6 and the tone rolled down to between 2-5. The guitar also has a piezo which I add in on about 1.5 for a touch of high end. I play direct into the amp - no pedals.

I'm looking for more clean headroom and to get rid of the slight mid-range nasal tone this amp has.

After reading you Tube Primer, I plan to replace V1 with the GT 12AX7C and V3 with a 12AT7MPI (A, Y or C?). I was planning to replace the output tubes with EL84S (JJs) 8-10 GT rating, but your description of this as a higher output power tube does not match GT's product description of this (low volume). I have no idea what to do with V2. Your advice would be greatly appreciated.

[myles_rose]

Originally posted by Shawners:

Thanx for the quick reply. What have some of your blueprinting customers w/ the nomad series liked or do you have any personal preferences?

Does the GT site just sell GT's or can I order NOS tubes also ?Thanx again miles...Shawners

Shawners....

 

On the Nomads, it depend on whether they are the EL84 based amp or the 6L6 based amps.

 

Personal preferences for the EL-84 amps are the EL-84S ( http://www.groovetubes.com/product.cfm?Product_ID=1687 ) in a #5 rating. Yes, these can be purchased off the website, actually from the link in this paragraph.

 

For V1 and V2, either the 12AX7C ( http://www.groovetubes.com/product.cfm?Product_ID=1158 ) or the ECC83S ( http://www.groovetubes.com/product.cfm?Product_ID=1587 ) depending on how you use the amp and your style.

 

For the 6L6 based amps - KT66HP in the 50 watt amps, in a #4 rating ( http://www.groovetubes.com/product.cfm?Product_ID=1692 )

 

For the 6L6 100 watt amps, 6L6GE in a #6 rating ( http://www.groovetubes.com/product.cfm?Product_ID=1714 )

 

In all amps, a matched phase inverter - ( http://www.groovetubes.com/product.cfm?Product_ID=1723 )

 

For NOS stuff, we do have some, but not on the website. For most NOS stuff, I send my clients to Mike at KCA NOS ( http://www.kcanostubes.com ) who is great and has great stock and great prices.

 

In V1 of the Nomads, for a bit more "ooommph" than stock, and less grain, most of my clients have picked the 12AX7C in a SAG tube at 92-116 on each side. This is about 12% mimimum additional output current drive than the stock average tube supplied in these amps, or the stock 12AX7s of today. I also go for a gain of between 82-88%, as this gives a bit more clean headroom when you want it, and less buzzy nature. The SAG stuff can be specified at http://www.groovetubes.com/product.cfm?Product_ID=1773

[myles_rose]

Originally posted by Altered Fifth:

Hi Myles,

Two questions, the first is more generic:

When swapping tubes in an amp to compare tones, is it necessary to always turn off the amp before pulling or replacing the tube? Can you safely do a "hot swap?" If the amp has a standby switch would this help?

 

The second question is more specific:

I play straight-ahead jazz and have recently purchased a Fender Blues Jr., which I am looking to upgrade. Rather than the standard Polytone jazz sound, I'm after a tone more like a cross between Kenny Burrell and SRV. I play a PRS Archtop with the volume down between 4-6 and the tone rolled down to between 2-5. The guitar also has a piezo which I add in on about 1.5 for a touch of high end. I play direct into the amp - no pedals.

I'm looking for more clean headroom and to get rid of the slight mid-range nasal tone this amp has.

After reading you Tube Primer, I plan to replace V1 with the GT 12AX7C and V3 with a 12AT7MPI (A, Y or C?). I was planning to replace the output tubes with EL84S (JJs) 8-10 GT rating, but your description of this as a higher output power tube does not match GT's product description of this (low volume). I have no idea what to do with V2. Your advice would be greatly appreciated.

Altered Fifth ......

 

You do not have the amp off for preamp tubes, but turn it way down, or put in standby, otherwise a big POP can damage the speaker. On power tubes, turn off the amp, and wait ... they are HOT.

 

On more clean headroom, make sure your output set is of a rating of 7-9 or so, bias the amp properly, but NOT on the too hot side (65% ID would be good in many amps).

 

A 12AT7 phase inverter in amps that have stock a 12AX7 will yield more headroom. A 12AU7 will yield even more.

 

The 12AT7MPI tubes are made from the 12AT7C.

 

Keep in mind, EL-84 amps typically have little clean headroom in many amps. They start off compressed right from the get-go. In cathode biased amps, some run way too hot with 8-10's and will have extreme tube wear. Stay at maybe 7 at the most, unless we talk about this on the phone.

 

85% of your tone and front end gain come from V1. Get that fixed first, prior to worrying about v2.

[jaycee22]

Hey Myles,

 

I'm baaa-aaack! My Deluxe Reverb is now outfitted with a NOS RCA 7025 in V2 and a true MPI in the last socket. I was going to go for the Brimar 6V6s, but I found some NOS Tung-Sol 6V6s at a store near me and they sound great. The V2 swap made a HUGE difference to these ears.

 

Anyhow, my question - I've been playing lately with a friend who plays a Twin Reverb and find myself wanting more clean headroom to compete. Since I was thinking of changing my speaker anyway, is there a speaker that could help me with this? Or any other tricks you might know?

 

As always, thanks a million!

[James-Italy]

Myles, I posted this in the "Tube Primer" thread since it was continuing my discussion with Guitplayer. I posted it here also because it's a true Ask Myles post!

 

Armed with Myles's Tube Primer in hand I was able to discuss tubes with the guitar-shop guy like I knew what I was talking about! Guitplayer, I followed your advice and bought what we said yesterday.

 

GT6V6"NOS"

12AX7 (EH?) for the V1

12AT7 (EH?) for the V2

 

Myles, do you think I need to run the Univalve in LoV as Guitplayer suggested? Is it gonna hurt if I run it in HiV?

I read in your primer that the 6V6 holds up well to 450+ volts on the plate. The Univalve manual states that HiV applies @450-470v (depending on the tube) and @300-320v on LoV.

 

Photo of the tubes

 

Edit: When I installed them today the Univalve has written on it the warning (like Guitplayer said) to only run 6V6 in LoV. So that settles that. There's more than enough crunch with LoV I found.

 

Instead I have another question. On the Univalve the Pre-amp tubes are labeled Input and Drive. Which is V1 and which is V2? I installed the AX7 in Input and the AT7 in drive. Is that good?

[michael saulnier]

James,

 

Myles hasn't gotten to this yet, so I'll take a stab at your questions.

 

First, I have the AX7 in the input and the AT7 in the drive... I do believe they are V1 and V2 as you guessed. At least they ACT like it...

 

If you run your 6V6 on HiV, you'll quickly burn it up if I understand it correctly. I recall Myles saying somewhere that he DOES run a 6V6 sometimes on HiV, but then he has a pretty easy availability to replacement tubes compared to us!

 

One other comment, I assume ALL of our tubes wear a bit more on HiV, and I personally LIKE the "spongier" sound of LoV with my tube set... However just from a "sound" standpoint, you should try your HiV capable ones on both settings and see and hear the differences for yourself.

 

guitplayer

[myles_rose]

Originally posted by jaycee22:

Hey Myles,

 

I'm baaa-aaack! My Deluxe Reverb is now outfitted with a NOS RCA 7025 in V2 and a true MPI in the last socket. I was going to go for the Brimar 6V6s, but I found some NOS Tung-Sol 6V6s at a store near me and they sound great. The V2 swap made a HUGE difference to these ears.

 

Anyhow, my question - I've been playing lately with a friend who plays a Twin Reverb and find myself wanting more clean headroom to compete. Since I was thinking of changing my speaker anyway, is there a speaker that could help me with this? Or any other tricks you might know?

 

As always, thanks a million!

jaycee22....

 

The RCA 7025 was the stock tube in the amps when most were made a lot of the time, and to me anyway, the best tube for the original sound.

 

I prefer Tung-Sols over most tubes in 6V6's, they are my favorite. In the 6L6 arena, I love the Tung-Sol 5881s.

 

For more headroom (though competing with a twin reverb is pretty much impossible), you can go to a Jensen C12N speaker, or an extension cab with something line an old JBL!

 

Other than that, it would be a hard "race".

 

You can go with higher and cleaner 6V6 tubes, but then you'd loose the magic of the amp.

 

Let your friend play your amp a while, with it's touch sensitive aspects, and soon he will be trying to make his amp sound like yours .... unless he is a pedal steel player.