Feel free to ask Myles

[GTO]

Thanks for the reply Myles. The "still around" comment was an inadvertant leftover paste from the HC forum, please don't be offended. Thanks for the info James and Myles, both of you hit the nail on the head.

[myles_rose]

Originally posted by Gabriel E.:

You need a good switch though, that with switch in a clean way without any spikes. Something like what stereo stores use when the demo speakers, switching from one to another using the same amp.

Thanks for the quick reply Myles. Just to be safe - the jump from 4 ohms to 8 ohms doesn't qualify as a spike?

 

I have a Morley ABY switch. Probably not quiet enough huh?

 

Thanks again,

 

Gabriel

Gabriel ...

 

You can try it, but first make sure it is capable of handling 50 watts at least. Most A/B switches are made to switch voltages of less a volt, and very low current. I'd also recommend a capacity of at least an amp in capacity.

 

You might want to first try it on some low powered effects or something, and when you switch it, see if you can hear a thump or loud click.

 

Regards,

[myles_rose]

Originally posted by GTO:

Thanks for the reply Myles. The "still around" comment was an inadvertant leftover paste from the HC forum, please don't be offended. Thanks for the info James and Myles, both of you hit the nail on the head.

GTO ....

 

You are more than welcome.

 

Regards,

 

Myles

[JamesPeters]

Hey Myles, how goes? Yeah, I tend to ramble sometimes...the typing almost gets ahead of my train of thought! Good thing to clear up the "standby on / standby off"--I remember being confused by the standby switch a few years back. "Turn standby on", someone would say, and I'd be like, "Umm, you mean use 'standby', so that the amp doesn't make any noise?"

 

A little like saying the phrase "Close the lights" (a french-canadian thing you might hear sometimes)--the first thing I think of is "closing the circuit", which means turning the lights on.

 

The amp is doing very well--that's part of the reason I've delayed launching petersamps.com for the last week. I got tweaking again--there goes the week! But I found a touch more subtlety while getting more gain yet...then in the end had to back off the gain somewhat because on its loudest settings it would get feedback. I know that's not the end of the world or anything, but part of the idea behind this amp was that no matter what setting I used on the dials/switches, I'd always find it "useable". I'm glad I spent the time, because I like the amp a lot more now than I did even a couple weeks ago.

 

Some people can't quite put their finger on what's different if I don't crank the gain, but some people on the other hand consider it a drastic improvement.

 

Now, I just have to MP3 the new clips (I have maybe a couple hours before bed tonight yet--long days at work!), paste the updated text, and get a couple pics pages going.

 

Work work work! Talk to you later!

[myles_rose]

Originally posted by JamesPeters:

Hey Myles, how goes? Yeah, I tend to ramble sometimes...the typing almost gets ahead of my train of thought! Good thing to clear up the "standby on / standby off"--I remember being confused by the standby switch a few years back. "Turn standby on", someone would say, and I'd be like, "Umm, you mean use 'standby', so that the amp doesn't make any noise?"

 

A little like saying the phrase "Close the lights" (a french-canadian thing you might hear sometimes)--the first thing I think of is "closing the circuit", which means turning the lights on.

 

The amp is doing very well--that's part of the reason I've delayed launching petersamps.com for the last week. I got tweaking again--there goes the week! But I found a touch more subtlety while getting more gain yet...then in the end had to back off the gain somewhat because on its loudest settings it would get feedback. I know that's not the end of the world or anything, but part of the idea behind this amp was that no matter what setting I used on the dials/switches, I'd always find it "useable". I'm glad I spent the time, because I like the amp a lot more now than I did even a couple weeks ago.

 

Some people can't quite put their finger on what's different if I don't crank the gain, but some people on the other hand consider it a drastic improvement.

 

Now, I just have to MP3 the new clips (I have maybe a couple hours before bed tonight yet--long days at work!), paste the updated text, and get a couple pics pages going.

 

Work work work! Talk to you later!

James,

 

Its going pretty nicely. The amp clinic I held last weekend was a lot of fun and it was pretty busy, but I still had enough time to talk to folks a bit.

 

So, you think you ramble on too much? Look at my posts

 

"Close the lights" .... French / Canadian? Funny... my wife and her family use that all the time, and my wife was born in Burbank CA., and her mom was born in Italy.

 

On the feedback issue, try a few different tubes in V1 and perhaps change a cap value on its socket. Some combinations of preamp and driver can be sensitive to that issue. Maybe don't go for all that much gain as stock, as to me anyway, at a certain point it all turns to fuzz tone sounds. You can get LOTS of vain cascading side A and B of V1, and then for clean just use one side of V1.

 

Keep up the great work. I am looking forward to your release!

 

Regards,

[dlb]

Hello Myles,

I posted about tube configuration for my Fender Prosonic Combo. Per your recommendation, I bought a jan GE 5751 and I also had a few GT 12AT7's then I got a pair of Svetlana 6L6GC's. After a few hours of swaping V1,V2,V3 around I think I have a combination that satisfies me. It took a combination of AX,AT,5751 to get there but it's there.

My last question on this amp is, is there a big bias difference going from 5881's to 6L6GC's?

 

Thanks a million again!....(Bows low only looking at the kings feet and retreats backwards)

[Mr. Dan Licks]

"Close the lights" .... French / Canadian? Funny... my wife and her family use that all the time, and my wife was born in Burbank CA., and her mom was born in Italy.

Deffinitly a French and Italian thing. In the old days when I was living in Paris I was studying with Nadia Boulenger. She would always tell us about something she heard on the radio.."This morning I opened the radio and heard a most beautiful emmision...."

 

Myles,

Ever hear power tubes start to sing all by them selves? Our 6L6 420s do now and again, until I give them a friendly tap. OUT OF TUNE AT THAT! Sort of a flat b flat. Sucks if you are playing a blues in A.

Dan

[myles_rose]

Originally posted by dlb:

Hello Myles,

I posted about tube configuration for my Fender Prosonic Combo. Per your recommendation, I bought a jan GE 5751 and I also had a few GT 12AT7's then I got a pair of Svetlana 6L6GC's. After a few hours of swaping V1,V2,V3 around I think I have a combination that satisfies me. It took a combination of AX,AT,5751 to get there but it's there.

My last question on this amp is, is there a big bias difference going from 5881's to 6L6GC's?

 

Thanks a million again!....(Bows low only looking at the kings feet and retreats backwards)

dlb,

 

Prosonics are tricky amps to get set up right. Without test equipment to measure the tubes so you know what you have, the only way left is to do what you did .... trial and error.

 

The Prosonic has a LOT of gain. It has more gain than my Mesa Mk. 1, by quite a bit. They are pretty terrific amps. Their basic problem, is in cascaded gain mode, they have so much gain possible, that using both volumes at over 3 or 4, makes so much gain that the sound becomes fuzzed out. With the 5751's and 12AT7's you are dropping the gain, where you can now get to about 5-6 on at least one of the volume controls, and then the amp also has more articulation, and they really sing.

 

The bias on 5881's and 6L6GC's is pretty close. Some 5881's are 26 watt tubes, rather than 30 watters as the 6L6GC, and some 5881's generally spec out higher than their 26 watt rating. Both the tubes vary a lot, but Fender typically sets their bias to run the amps pretty hot, but still with a lot of range to slip tubes in and out with some amps. With others, such as the Pro Reverb, the bias is set to draw about 30mA which is really a bit cool at the plate voltage these amps develop. The Prosonic is somewhere in the mid point, and it has a LOT of leeway, as the tube rectifier really drops the plate voltage compared to the solid state rectifier section.

 

Bottom line here, the short answer .... you can use 5881's or 6L6GC's in your amp, and if they are something like Groove Tubes, you can pretty much use anything from a #3 to a #7, and your bias will be pretty fine. If its any of the Fender/GT color coded tubes, these are all pretty close to a #5 range, something like the Mesa color code that translates to GT ratings of 4-6.

 

You're probably just fine, but even if you are running hot, these amps do great even running hot. If the plates are not glowing, you're fine.

 

Regards,

[myles_rose]

Originally posted by Mr. Dan Licks:

"Close the lights" .... French / Canadian? Funny... my wife and her family use that all the time, and my wife was born in Burbank CA., and her mom was born in Italy.

Deffinitly a French and Italian thing. In the old days when I was living in Paris I was studying with Nadia Boulenger. She would always tell us about something she heard on the radio.."This morning I opened the radio and heard a most beautiful emmision...."

 

Myles,

Ever hear power tubes start to sing all by them selves? Our 6L6 420s do now and again, until I give them a friendly tap. OUT OF TUNE AT THAT! Sort of a flat b flat. Sucks if you are playing a blues in A.

Dan

Dan,

 

Yes. If they are Mesa STR-420's, they are Chinese tubes and not too reliable. If they are the Mesa Chinese, then try to replace them as soon as you get the chance.

 

Regards,

[Biz Markie]

Hey Myles! I originally started a new thread with this one, but this is probably a better place for my question. I have a JCM 600 all tube head and cab. It has 2 Svetlana EL34s in the power amp section and 4 ECC83s (12AX7) in the pre-amp stage. It has clean and overdrive channels. I have to replace the power amp tubes as one of them has died. I'm wondering if the power tube section of the amp really plays a crucial role in the tone and if I could change the tone in this area? Also, I've read the some stuff on a link you posted about how the pre-amp tubes can change the tone of an amp. I'm wondering if there are any tubes out there that can make the overdrive channel have more distortion and bite. Or if not, is there a mod that can be made to the amp do this. I'm not fond of the overdrive I'm getting now (well not now as the amp is dead, but when it was working). It sounds too smooth with hardly any bit and the distortion is kinda tame. I usually use the clean channel at just about full volume with a Tube Screamer and a Boss EQ in front. I'd like to have a more dynamic sound as I don't have a "clean" channel as such. Just curious if theres something like a "JCM 600 to JCM 800 mod" sorta like the familiar TS-9/TS-808 mod. Thanks.

[JamesPeters]

Originally posted by Mr. Dan Licks:

"This morning I opened the radio and heard a most beautiful emmision...."

Oh man, I could only imagine someone saying that to me--I think I'd split my sides!

 

Ok, I got a few clips up...I have a couple more hours of stupid noodling to go through before I put the rest up, but I had to get something up--too many people were asking for clips for me to leave it until "I had the time" (which the way it's going this week, may never happen, lol!)

 

Catch you later!

[myles_rose]

Originally posted by Biz Markie:

Hey Myles! I originally started a new thread with this one, but this is probably a better place for my question. I have a JCM 600 all tube head and cab. It has 2 Svetlana EL34s in the power amp section and 4 ECC83s (12AX7) in the pre-amp stage. It has clean and overdrive channels. I have to replace the power amp tubes as one of them has died. I'm wondering if the power tube section of the amp really plays a crucial role in the tone and if I could change the tone in this area? Also, I've read the some stuff on a link you posted about how the pre-amp tubes can change the tone of an amp. I'm wondering if there are any tubes out there that can make the overdrive channel have more distortion and bite. Or if not, is there a mod that can be made to the amp do this. I'm not fond of the overdrive I'm getting now (well not now as the amp is dead, but when it was working). It sounds too smooth with hardly any bit and the distortion is kinda tame. I usually use the clean channel at just about full volume with a Tube Screamer and a Boss EQ in front. I'd like to have a more dynamic sound as I don't have a "clean" channel as such. Just curious if theres something like a "JCM 600 to JCM 800 mod" sorta like the familiar TS-9/TS-808 mod. Thanks.

Markie,

 

The output section can have a big change on your sound too.

 

Adjusting the bias make an amp run cooler or hotter, distorts quicker or later, makes it smoother or more coarse.

 

Outside of bias, the type of tubes you use has an effect too. Svetlana's are full bodied and very well rounded, Mullards are very linear, Siemens are smooth and predictible, and JJ's are very strong in the upper mid and above range, while still as strong in the low end as a Svetlana.

 

This is part of the reason behind what I call "blueprinting", that is, changing tubes and settings for a particular player's tastes and requirements.

 

You can make your output section cleaner or distort quicker by tube selection, even within a specific tube type and maker. This is why folks like Groove Tubes have a range of 1-10 for their tubes.

 

Changing the phase inverter (V4 on your amp) can make the preamp distortion more of a factor if you go in one direction, or the poweramp have more of it's character if you go in the other direction.

 

As far as mods, one of the best folks in the business is Trace over at voodoo amps.

 

Hope this helped.

 

Regards,

[jazzcaster]

A quick question for Myles! I have a new Fender Pro Reverb (Pro Tube Series). I love it. I want to experiment with some tube swaps. My question is....which tubes (ie. function, like tremolo, reverb etc.)correspond to which location on the chassis (ie. V1, V2, V3 etc.). I have the schematic that came with the amp, but I don't know how to read it....it's almost all Greek to me!).

 

Thanks Myles (or anyone else who can help).

[Mr. Dan Licks]

Hi Myles,

Man, how do you manage to keep your cool? I was just over at HC to see what was going on on the amp forum and fought my way through all the adolescent rantings of squigglewhatshisname. Some nice cats over there, but I like it better here.

You suggested Svets of a Groove Tube #7 rating for our 50 Cal+. I saw somewhere that the Mesa color scale runs from red (warm sound) to blue(cold, hard sound). Is this correct? Now, by putting hotter tubes in a Boogie do we in effect change the bias of the amp? Would the result be more or less the same as setting the bias hotter and using a colder tube? (No, I am NOT planning to put a trim pot on the bias) Just wondering.

What do you think of this setup on the pre tubes? (Suggested by an Aussie on HC who played a 50 Cal for 10 years)

V1-GT 12ax7R2, V2-Mesa 12ax7C, V3-Mesa 12ax7C,V4-(12AT7), V5-Sovtek 12ax7LPS + the 6L6GC Svets you suggested.

Many thanks,

Dan

 

This thread seem to be more of a forum within a forum. Deffinitly cool.

[myles_rose]

Originally posted by jazzcaster:

A quick question for Myles! I have a new Fender Pro Reverb (Pro Tube Series). I love it. I want to experiment with some tube swaps. My question is....which tubes (ie. function, like tremolo, reverb etc.)correspond to which location on the chassis (ie. V1, V2, V3 etc.). I have the schematic that came with the amp, but I don't know how to read it....it's almost all Greek to me!).

 

Thanks Myles (or anyone else who can help).

jazzcaster,

 

I cannot help yet ... I am waiting for the prints from Fender on one of them I am working on currently.

 

I have had the amp for a week from a client. I do know that V1 and V2 are the normal first gain stages, and if you look, you will probably find these two tubes have a small o-ring at the bottom of their heat sheilds (unlike the others), and these two tubes are also wrapped in shrinkwrap to cut down on microphonics. (This is an old trick ... sometimes a rubber band on a first gain stage helps reduce microphonics in an emergency when you don't have other tubes at a gig).

 

In any case, I have been going through the amp, making my own conclusions as I move along.

 

So far this is what I have learned.

 

1. These amps use fairly high B+ voltage ... on the order of 465 volts. VERY nice power supply section.

 

2. The amp is a bit overbiased and cool at its suggested 30mA, but is not at all grainy, and if you raise the bias, you may find the amp even louder than it already is.

 

3. The clean channel is LOUD and CLEAN and if you want the sound and power of a Twin Reverb, this amp has it in spades.

 

4. The gain channel is just plain crazy. This amp is capable of more first gain stage gain than just about anything I have ever seen. Fender seems to have met the clean and ultra gain issue with a very high degree of success.

 

5. V1 and V2 were too hot, and by going to some selected 12AX7's with a bit less output, it allowed the gain and volume on the gain channel to be able to be turned to more than 3 and 3. Prior to that, the gain was more extreme than my Mesa amps.

 

6. The Jensen 12" speaker in there is the definitive speaker choice for this amp ... you can get the classic 60's and 70's sound of the Jefferson Airplane or Quicksilver Messenger Service ... the Byrds or any of the San Francisco rock groups of that era on the clean channel. DO NOT change this speaker.... it is perfect.

 

7. The amp on the gain channel has more articulation and definition of individual notes within a chord than my Mesa amps, my Mesa preamp, or the SLO-100 or Marshalls.

 

As I learn more, I will post it, or drop me an email and we can keep in touch.

 

This amp is something of a change for Fender. Their Prosonic was their first venture into very high gain with a cascaded gain circuit, and they learned a lot with that amp it seems, as its a nice amp with a lot of features such as the rectification, etc.

 

This particular amp is going to be one of their classics in the future, I'd bet on it. There is a LOT of room to work as the chassis is very deep, and the box itself is quite a bit deeper than a Twin Reverb, so even with a single 12", the sound is immense, something like the Single Showman of the past.

 

The amp is built VERY VERY VERY well. Its transformers are really terrific. Its a pretty heavy sucker, but maybe not as bad as a Twin Reverb, and a bit easier to get into a car trunk.

 

The stock Sovtek 6L6's are pretty fair, but soon I will be trying some Svetlana's, until I can get a duet of the new 6L6GE's from Groove Tubes, as I am out of those or they are in other amps for testing.

 

Bottom line here .... this is one of the most versitile amps I have seen in a very long time. Its just a matter of time until Fender looks at their pricing, as it is more than a Super Reverb as far as useage, and thank goodness it has a 1/4 power setting of 12 1/2 watts .... but then again, even at settings of 1 1/2 on the volumes, it still makes a Rickenbacker 12 string crack and bark on the chords on the chean channel, and will sing forever on the gain channel with the gain at 3 and the volume on 4.

 

You have one of the first great unknown (so far) amps of modern day ... with the blackface flair of the past.

 

Regards,

[myles_rose]

Originally posted by Mr. Dan Licks:

Hi Myles,

Man, how do you manage to keep your cool? I was just over at HC to see what was going on on the amp forum and fought my way through all the adolescent rantings of squigglewhatshisname. Some nice cats over there, but I like it better here.

You suggested Svets of a Groove Tube #7 rating for our 50 Cal+. I saw somewhere that the Mesa color scale runs from red (warm sound) to blue(cold, hard sound). Is this correct? Now, by putting hotter tubes in a Boogie do we in effect change the bias of the amp? Would the result be more or less the same as setting the bias hotter and using a colder tube? (No, I am NOT planning to put a trim pot on the bias) Just wondering.

What do you think of this setup on the pre tubes? (Suggested by an Aussie on HC who played a 50 Cal for 10 years)

V1-GT 12ax7R2, V2-Mesa 12ax7C, V3-Mesa 12ax7C,V4-(12AT7), V5-Sovtek 12ax7LPS + the 6L6GC Svets you suggested.

Many thanks,

Dan

 

This thread seem to be more of a forum within a forum. Deffinitly cool.

Dan,

 

How do I keep my cool? Just realize that some folks speak without thinking, and just let it pass most of the time.

 

I like it more over here too, as it seems at times that I can spend more time as there is less traffic to deal with from some of the folks like the fellow you mentioned earlier. There are great folks on both forums, but I give this forum my first priority.

 

As far as the Mesa scale .... here it is, compared to the Groove Tubes scale:

 

Mesa vs Groove Tubes scale

Red 4

Yellow 4

Green 5

Gray 5

Blue 6

White 6

 

Mesa keeps their tubes in a narrow range. On my Mesa amps, the amps are still a little cold even with the Mesa "white" tubes.

 

Basically, as an example, if your amp is at, lets say, a 38% idle dissapation with a Mesa "green" set of 6L6's, and you go to a "blue", you may go to about 40%-42% on your bias idle dissapation, without adjusting anything.

 

I find Groove Tubes #7 ratings work best in my own Mesa amps, which is a bit outside of the Mesa range, but still just a hair about 50% ID, which is still lower than some folks prefer. This 50% range gives good overall performance and very long tube life.

 

I would pass on the bias control pot, as there are tubes from folks like Watford Valves and Eurotubes, that can pick tubes dialed right in to your particular amp, without having to adjust anything.

 

On the Aussie fellow that have his ideas, I have to agree with him technically, its really a matter of taste. His picks are right on the money, the only issue that plagues some Mesa amps is microphonics in V1 and V2. His choice for V1 is typically a tube that is pretty good in the microphonic rejection department, and this is the weak spot in most any amp, Mesa or non-Mesa.

 

Mesa amps have a high gain structure, so the are more prone to microphonics. Your Caliber 50 has a bit of advantage over a Mark series though, it is physically larger than a Mark, so there is a bit more room between V1 and the back of the speaker. Sometimes its a matter of 1/2 and inch, or in your neck of the woods, 1cm or so, or a slightly different position of the tube in relation to the speaker position. The Caliber and Nomad series from Mesa are a lot nicer in this aspect than the Mark series, until you get to the Mk IV if you opt for the wide chassis.

 

I'd go along with your Aussie friend's post, he's right on the money, and NOS tubes in a modern amp like yours might sound pretty or nicer to some folks, might sound worse to others, but in the end, your amp will sound pretty darn great they way it is. The WEAK area in Mesa amps that use 6L6's is when they are supplied with the Mesa STR-420 tubes, which are Chinese. Any other designation from Mesa is a vast improvement. Their STR-454's are Svetlana tubes, and Mesa sells those for less than a lot of other folks sell Svetlana tubes.

 

Regards,

 

Myles

[jazzcaster]

Myles,

 

Thanks so much for your great info on the new Pro Reverb. I will keep in touch and hope to hear more after you've had a chance to delve further into the amp you have. As a note (hey...I can actually offer "you" some info!), I swapped out the stock Sovtek 6L6 Groove tubes (I had no real problem with them, I'm just a tinkerer at heart) and replaced them with som Svetlana's. WOW! Did I say Wow?! I've heard many good things about this 6L6, and now I know why. My clean channel sounds....well....cleaner, if thats possible. I guess "more sparkle" is how to describe it in cliche terms. But the real treat is the overdrive. It is buttery smooth compared to the stock Groove Tubes. (I play a Strat with Van Zandt Blues pups). I adjusted the bias to the Fender spec of 30mv. I had also adjusted the bias on the stock tubes when I first got the amp (they were slightly "cold", if thats the term (26mv). Once I figure out the pre-amp tubes, I'll start a bit of swapping to feed my curiosity. My God this amp has me jazzed!!!

[myles_rose]

Originally posted by jazzcaster:

Myles,

 

Thanks so much for your great info on the new Pro Reverb. I will keep in touch and hope to hear more after you've had a chance to delve further into the amp you have. As a note (hey...I can actually offer "you" some info!), I swapped out the stock Sovtek 6L6 Groove tubes (I had no real problem with them, I'm just a tinkerer at heart) and replaced them with som Svetlana's. WOW! Did I say Wow?! I've heard many good things about this 6L6, and now I know why. My clean channel sounds....well....cleaner, if thats possible. I guess "more sparkle" is how to describe it in cliche terms. But the real treat is the overdrive. It is buttery smooth compared to the stock Groove Tubes. (I play a Strat with Van Zandt Blues pups). I adjusted the bias to the Fender spec of 30mv. I had also adjusted the bias on the stock tubes when I first got the amp (they were slightly "cold", if thats the term (26mv). Once I figure out the pre-amp tubes, I'll start a bit of swapping to feed my curiosity. My God this amp has me jazzed!!!

jazzcaster,

 

The amp I am in the process of still doing on and off had the stock tubes in V1 and V2 changed right at the start too.

 

I am trying to get a duet of the new GE tubes to put in there (I have a post on them in here somewhere), and then we will proceed.

 

I have a lot of the Svets around, and generally prefer them for just about anything, but still want to try the new GE's, as in a Vibroverb they made than amp come to life even more than with the Svets that were in there.

 

Regards,

[Rai168]

Hi Myles. I am running GE6550A's in my VHT Ultralead. I know these are a high output tube. What's a good bias to run it at? I think my tech may have them a lil cold...I was originally running the Sovtek KT88's and he had to turn the bias down for the GE6550A's. Just looking for a recommendation as I play hi-gain stuff. Thanks -

 

Rai

www.CalyxinRuin.com

[Mr. Dan Licks]

Myles,

Well, things are beginning to make some sense to me, thanks to you old pros out there!

One short follow-up:

Just in principal, if you go from a #5 to a #7, what would be the general, overall change in the sound? In other words, cold tubes = ?????, hot tubes =?????.

Yesterday my son went to practice with his friends and his teacher and "had to" play through a Marshall. When he came home, first thing he said was, "I like my Boogie better!" Can't wait to trash the 420s....

Dan

[aeon]

Myles:

 

I have a couple of questions about that Fender Pro Reverb you are working on. With the fairly high B+ voltage it uses, it is able to derive ~50 watts from a duet of 6L6 valves. How does the Pro Reverb make the switch to 12.5 watts? Does it only use one of the 6L6s and also drop the B+ voltage, or does it continue to use both valves with a more severe drop of the B+ voltage?

 

A pair of THD Yellowjackets will usually drop a 50 watt amp to 20 watts as it moves from 6L6 to EL84. Do you think the Pro Reverb quarter-power mode would still function with EL84s, giving an output of ~5 watts?

 

The Pro Reverb had already caught my attention, but your praise of it has heightened my interest further. Thanks in advance!

[myles_rose]

Originally posted by Rai168:

Hi Myles. I am running GE6550A's in my VHT Ultralead. I know these are a high output tube. What's a good bias to run it at? I think my tech may have them a lil cold...I was originally running the Sovtek KT88's and he had to turn the bias down for the GE6550A's. Just looking for a recommendation as I play hi-gain stuff. Thanks -

 

Rai

www.CalyxinRuin.com

Rai168,

 

The bias for a KT-88 and 6550A is different, but I would not be able to give you a figure until I know your B+ voltage.

 

That would get us in the ballpark, but to really dial it in, would involve some knowledge of your playing style, and I'd possibly fine tune the bias using a scope so I could set it more closely to where you keep your volume and master controls set to give you some playing dynamics which is tricky with 6550A's, as they are so clean

 

Get back to me with your B+ voltage and we'll continue.

 

Regards,

[myles_rose]

Originally posted by Mr. Dan Licks:

Myles,

Well, things are beginning to make some sense to me, thanks to you old pros out there!

One short follow-up:

Just in principal, if you go from a #5 to a #7, what would be the general, overall change in the sound? In other words, cold tubes = ?????, hot tubes =?????.

Yesterday my son went to practice with his friends and his teacher and "had to" play through a Marshall. When he came home, first thing he said was, "I like my Boogie better!" Can't wait to trash the 420s....

Dan

Dan,

 

As a simple example, but still pretty complete actually .... if you had a set of #5's in an amp and you saw that when you turned the volume control to say, "5" and your guitar to "10", that when you played heavy, you got output tube distortion, and then changed to a #7 set of tubes, you would then see the amp would be cleaner at the same settings, and you'd maybe have to turn the amp to a higher setting to get back that same amount of distortion.

 

With the 7's, the amp would be cleaner at a given setting, and a bit louder too at the same setting as with the 5's.

 

Most players like mid range tubes, as they are plenty loud enough when clean, and then when they play harder, it distorts more as your playing attack is harder. So in essence, you keep the guitar and amp settings in a range so you have a lot of feel and dynamics ... play more on the lighter side and its clean, and dig in harder and it gets dirty.

 

As far as your son prefering his amp to a Marshall, that is not too much of a surprise. Marshall amps have a particular sound, and they have a lot more midrange boost as designed in their design when compared to a Fender amp. I have a section on my webpage on this subject with graphs of the response curves of both of these amps. What Marshalls do, they do great, and there are two kinds of Marshall owners/users .... those which live by the Marshall sound alone and would not play anything else ... and those that have a Marshall in their "inventory" to use when they want the Marshall sound.

 

There are a lot of amps that imply they can sound like a Marshall, and the word of attention here is "LIKE", .... which is not the SAME. Marshall amps have a simple circuit with very little in the signal path. The four input and early Marshalls have no reverb, or effects loops, so there is little to alter the signal path. Marshall amps also have crossover notch distortion in their design as part of their sound. This is one reason that these amps do not sound their best when biased using the current draw method. They also have the feedback loop coming off the 16 ohm tap of their output transformer, rather than off the 2 ohm tap as on a tweed Fender Bassman, which some folks think are the same circuit. Where the tone controls are in a Marshall vs. a Fender, post gain / pre gain, is yet another difference.

 

Your son's Mesa is an amp a lot more versitile than a Marshall, so unless he fell in love with the Marshall sound, I could see his viewpoint.

 

Also, Marshall amps have their magic come into play when turned up near or at their max. This is why folks like Jeff Beck use 50 watt heads rather than 100 watt heads. They get to their max at a more rational level.

 

Regards,

[Mr. Dan Licks]

Gotcha.

So it boils down to finding a balance between pre tube distortion and power tube distortion. We find that with the volume knob set at 4, the sound has plenty of distortion, any highter and it is too much. Now, how can you tell the difference between what is being distorted in the pre section, and what is being distorted in the power section. There must be a significant difference.

Thanks, Dan

[myles_rose]

Originally posted by aeon:

Myles:

 

I have a couple of questions about that Fender Pro Reverb you are working on. With the fairly high B+ voltage it uses, it is able to derive ~50 watts from a duet of 6L6 valves. How does the Pro Reverb make the switch to 12.5 watts? Does it only use one of the 6L6s and also drop the B+ voltage, or does it continue to use both valves with a more severe drop of the B+ voltage?

 

A pair of THD Yellowjackets will usually drop a 50 watt amp to 20 watts as it moves from 6L6 to EL84. Do you think the Pro Reverb quarter-power mode would still function with EL84s, giving an output of ~5 watts?

 

The Pro Reverb had already caught my attention, but your praise of it has heightened my interest further. Thanks in advance!

aeon,

 

Getting 50 watts from a pair of 6L6's is pretty easy with 465 volts on the plates. A few years back, Fender had an amp called the "75" that pulled 75 watts from a pair with over 500 volts on the plates. Most of the black face 60's Bassman heads I work on produce more than 50 watts, and in some cases, up to 70.

 

How it gets down to its 1/4 power rating, is by lowering the voltage on the B+ as well as a few other places in the circuit, such as bias voltage changes, etc.

 

The Yellow Jackets will work fine at the 1/4 power setting, but the issue with EL-84's is that they tend to get into distortion fairly quickly and have a smooth distortion character. That's why a lot of folks like them a lot.

 

Go play one of them at a Sam Ashe or Guitar Center or any Fender dealer. Compare their clean sound to a Twin Reverb, and then switch to the drive channel. Its a pretty unique and versitile amp. It can sort of go from Jazz/Rhythm/Country/Pedal Steel to the strongest and most sustaining lead tones that would open the eyes of the most die hard Metal/Thrash/Speed players. About the only complaint you might hear, is folks wanting something in the middle, and I think we found that with a few changes here and there, and then turning the gain channel's volume to a higher setting and setting the gain control low, down to about "2", for a nice crunch where chords are still very refined.

 

It seems to do what amps at three times the money do, and at times, a bit more.

 

I'd get one myself, but family finances etc. are one issue, regardless of the cost, and dealing with my wife and "why do you need another amp", is an even more difficult proposal

 

Regards,

[myles_rose]

Originally posted by Mr. Dan Licks:

Gotcha.

So it boils down to finding a balance between pre tube distortion and power tube distortion. We find that with the volume knob set at 4, the sound has plenty of distortion, any highter and it is too much. Now, how can you tell the difference between what is being distorted in the pre section, and what is being distorted in the power section. There must be a significant difference.

Thanks, Dan

Dan,

 

If you want more preamp or front end distortion, turn the master low and the volume/gain high.

 

If you want a blues sound, and nice output distortion, turn the master all the way up, to effectively get it out of the circuit and turn the amp into something of a "non-master-volume" amp, and then use your volume/gain at the very low settings for output tube distortion and less preamp overdrive.

 

Regards,

[Mr. Dan Licks]

Right. So the front end type is more for the screaming leads, and the back end for a warmer, gentler kind. That is the impression we have gotten when we have done just that.

Thanks again for taking the time to answer these "stupid" questions. I hope that the information is also helpful to others. Even though a lot of it is still over my head, I get a lot out of your posts to others.

Dan

[myles_rose]

Originally posted by Mr. Dan Licks:

Right. So the front end type is more for the screaming leads, and the back end for a warmer, gentler kind. That is the impression we have gotten when we have done just that.

Thanks again for taking the time to answer these "stupid" questions. I hope that the information is also helpful to others. Even though a lot of it is still over my head, I get a lot out of your posts to others.

Dan

Dan,

 

You are right on track. Metal and speed players and hard rock folks take the scraming lead route, and blues players take the output crunch road most of the time.

 

Don't worry about whether a question seems "smart" or "stupid", as there are a lot of folks that would like to ask a lot of things, but its people like you that surface the question for the benefit of a lot of people. The less you know on a subject, the more detail is needed in the explanation, and that turns out to be a good thing, as it fills in a lot of blanks for some folks where they may know the answer, but not the reason "why" behind the answer.

 

By the way .... when you get to the states, I'd be happy to trade some graded tubes for some pastry!

 

Regards,

[Mr. Dan Licks]

Mmmmmmmm, sounds good, but pastery doesn't travel well and it is VERY hard for me to resist temptation!

[myles_rose]

Originally posted by Mr. Dan Licks:

Mmmmmmmm, sounds good, but pastery doesn't travel well and it is VERY hard for me to resist temptation!

Dan...

 

Darn it! Its my weakness too.

 

Myles