Brown Sound - Pulling two tubes for Class A

[EddyLenz]

Hey Guys,

In one of the more recent Brown Sound videos by Jim Gaustad, he talked about pulling two tubes to get even closer to the original tone.

Unlike standard 100W tube pulling, where you'd usually pull the outer or inner two power tubes, he described pulling one of the pairs, in this case, the two power tubes closest to the preamp tubes (V4/5). That changes the power amp from class AB to class A.

After trying this with my 1968 Super Lead with EVH Specs and 6CA7s, I immediately heard what he meant.
The sound gets brighter, more aggressive, with that slightly broker character.
It's an extremely fun sound to play because of how it responds to the guitar.

Since my last Brown Sound video, I got the 6CA7s, which are a clear improvement.
I also put the original Fender bridge back on my custom shop Strat, which now sounds way better for VH tones than my 1972 Strat.
The CS strat is thinner and brighter, which I usually don't like, but it helps keep the cranked Plexi thight and defined in the low end.

Here's a comparison between Class AB and Class A
Let me know what you think!

 

[LP Freak]

Yep, that’s it right there

 

[chumbucket]

Hey Guys,

In one of the more recent Brown Sound videos by Jim Gaustad, he talked about pulling two tubes to get even closer to the original tone.

Unlike standard 100W tube pulling, where you'd usually pull the outer or inner two power tubes, he described pulling one of the pairs, in this case, the two power tubes closest to the preamp tubes (V4/5). That changes the power amp from class AB to class A.

After trying this with my 1968 Super Lead with EVH Specs and 6CA7s, I immediately heard what he meant.
The sound gets brighter, more aggressive, with that slightly broker character.
It's an extremely fun sound to play because of how it responds to the guitar.

Since my last Brown Sound video, I got the 6CA7s, which are a clear improvement.
I also put the original Fender bridge back on my custom shop Strat, which now sounds way better for VH tones than my 1972 Strat.
The CS strat is thinner and brighter, which I usually don't like, but it helps keep the cranked Plexi thight and defined in the low end.

Here's a comparison between Class AB and Class A
Let me know what you think!

Hey Eddy,
Did you change the impedance selector when you pulled two tubes?

 

[EddyLenz]

Hey Eddy,
Did you change the impedance selector when you pulled two tubes?

Yes, I did.

 

[MadAsAHatter]

Did you have to do anything with the bias when you pulled the tubes or just change the impedance?

 

[harddriver]

Thanks for the extended A/B comparisons between the two modes of operation Eddy!

There are times that I like the two tubes pulled and times I like the standard class A/B but there is no denying that when V4 V5 are pulled the amp gets more aggressive, distorts and responds differently as Jim Gaustad described it. I didn't think the differences would be that noticeable but I did notice the difference.

Very cool Eddy! Thanks for taking the time to do such an experiment!

I see you are running JJ 6ca7's which are still power pentodes like EL34's. If you want to try a modern 6CA7 that is a beam forming element tube exactly like the Sylvania 6CA7's the EH 6CA7's are correct and sound quite close to my Sylvania's.

 

[Exo-metal]

Was Ed running class A@2ohms like he said or was that Ed being Ed?

 

[EddyLenz]

Did you have to do anything with the bias when you pulled the tubes or just change the impedance?

I didn't change it. I'll have to do some more testing with different bias though. I'll do that when I'm setting up the rig for captures.

 

[EddyLenz]

Thanks for the extended A/B comparisons between the two modes of operation Eddy!

There are times that I like the two tubes pulled and times I like the standard class A/B but there is no denying that when V4 V5 are pulled the amp gets more aggressive, distorts and responds differently as Jim Gaustad described it. I didn't think the differences would be that noticeable but I did notice the difference.

Very cool Eddy! Thanks for taking the time to do such an experiment!

I see you are running JJ 6ca7's which are still power pentodes like EL34's. If you want to try a modern 6CA7 that is a beam forming element tube exactly like the Sylvania 6CA7's the EH 6CA7's are correct and sound quite close to my Sylvania's.

Yeah, I also wasn't expecting it to make such a difference.
Damn, now I might have to try those EH 6CA7 haha

 

[EddyLenz]

Was Ed running class A@2ohms like he said or was that Ed being Ed?

No idea. Not sure how you would even run it like that.

 

[EddyLenz]

Thanks for the extended A/B comparisons between the two modes of operation Eddy!

There are times that I like the two tubes pulled and times I like the standard class A/B but there is no denying that when V4 V5 are pulled the amp gets more aggressive, distorts and responds differently as Jim Gaustad described it. I didn't think the differences would be that noticeable but I did notice the difference.

Very cool Eddy! Thanks for taking the time to do such an experiment!

I see you are running JJ 6ca7's which are still power pentodes like EL34's. If you want to try a modern 6CA7 that is a beam forming element tube exactly like the Sylvania 6CA7's the EH 6CA7's are correct and sound quite close to my Sylvania's.

I just looked it up because I thought I read it when I bought them... The JJ 6CA7 are Beam-Power-Tetrode

 

[harddriver]

I just looked it up because I thought I read it when I bought them... The JJ 6CA7 are Beam-Power-Tetrode

Unless JJ changed something recently I think that description is a play on words Eddy as far as I know they have been power pentodes since their inception. Don't get me wrong you clips sounded good with them. If JJ did change them to a beam forming element like the Sylvania that would indeed be exactly like the Sylvania 6CA7's. I've seen the same description as tetrodes for the JJ 6ca7's looking around as well so that further confuses the issue.

From Eurotubes site:

Description
The JJ Big Bottle 6CA7 is a modern Beam Pentode replacement for all EL34 and classic 6CA7 applications. These tubes have extended lows and a distinct emphasis in the low mids (rather than the upper mid push traditional EL34’s are Known for). That combined with very round and natural highs makes this tube very thick and round sounding. About as close as you can get to mixing an EL34 with a 6L6GC.

From Tubedepot:

Electro-Harmonix 6CA7 EH Power Vacuum Tube​

Designed to the exacting specifications of the Phillips 6CA7, this classic tetrode returns to life in a big bottle design. The 6CA7EH is built to withstand today's high-gain amps while still retaining the detailed tone and component integrity of the original. A direct replacement, with military reliability, for any EL34.

 

[EddyLenz]

Unless JJ changed something recently I think that description is a play on words Eddy as far as I know they have been power pentodes since their inception. Don't get me wrong you clips sounded good with them. If JJ did change them to a beam forming element like the Sylvania that would indeed be exactly like the Sylvania 6CA7's. I've seen the same description as tetrodes for the JJ 6ca7's looking around as well so that further confuses the issue.

From Eurotubes site:

Description
The JJ Big Bottle 6CA7 is a modern Beam Pentode replacement for all EL34 and classic 6CA7 applications. These tubes have extended lows and a distinct emphasis in the low mids (rather than the upper mid push traditional EL34’s are Known for). That combined with very round and natural highs makes this tube very thick and round sounding. About as close as you can get to mixing an EL34 with a 6L6GC.

From Tubedepot:

Electro-Harmonix 6CA7 EH Power Vacuum Tube​

Designed to the exacting specifications of the Phillips 6CA7, this classic tetrode returns to life in a big bottle design. The 6CA7EH is built to withstand today's high-gain amps while still retaining the detailed tone and component integrity of the original. A direct replacement, with military reliability, for any EL34.

Then it looks like my store made a mistake, because this is what they say.

 

[thegame]

No idea. Not sure how you would even run it like that.

Was Ed running class A@2ohms like he said or was that Ed being Ed?

Wire up a 16 ohm cabinet to all parallel, which results in a 4 ohm load. Use two of those cabs together if the amp wants to see 2 ohms.

 

[EddyLenz]

Wire up a 16 ohm cabinet to all parallel, which results in a 4 ohm load. Use two of those cabs together if the amp wants to see 2 ohms.

Yeah, but I don't know why anyone would want that. There's no case in which the amp would want to see 2 ohms.

 

[MGL AmpWorks]

Eddy, None of the modern tubes labeled 6CA7 are remotely the same as the original US tubes that Ed used. I’ve got a bunch of originals. If you want to pay for the shipping back and forth, I’d send you a pair to try.

 

[Dan Gleesak]

not really Class A, it’s just taking the load away from half the transformer…. But I’m sure it’ll sound killer for a little while at least

 

[EddyLenz]

Eddy, None of the modern tubes labeled 6CA7 are remotely the same as the original US tubes that Ed used. I’ve got a bunch of originals. If you want to pay for the shipping back and forth, I’d send you a pair to try.

Thanks, but I don't want to risk anything with them. Pete Thorn did a video comparing tubes and there were Sylvania and EH 6CA7 in there. Really hard to hear a difference at all there.

 

[Techdeth]

Awesome af

 

[Cless357]

Is it possible to even use only one power tube ?