Tech question: Rebel 6V6 vs EL84 volume difference

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jwdubois

jwdubois

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I don't know if it's an actual volume difference, or just an apparent difference due to the extra "thickness" of the EL84 side, but on my Rebel the EL84 side always seems louder than the 6V6 side. If I go from one side to the other I always have to adjust the Gain and Master to level it out.

Is there an internal adjustment to adjust the ratio, or maybe a resistor mod to adjust the ratio, or is this just an inherent issue with the two tube types that you just have to live with?

JWW
 
You've gotta live with it. Before the tube blend knob, there was just a toggle between the two types of tubes and you always had to adjust the volume and gain.
 
Yeah, this seems to be very normal due to the... I want to say "character" difference between the tubes. I guess that's the best way I can say it as I couldn't explain the "technical" difference between the 2. This really wouldn't be a problem live because it's very unlikely you'll be twisting that knob mid-song. But, I can see how it can be a bit tricky if recording, when you want to keep the volume exactly the same. But then I again, if you were switching amps in order to get different sounds for layered tracks or different parts, you are going to have to do much more tweaking than a simple volume adjustment.
 
It's not that big a deal, I can live with it. OTOH, it seems like a simple mod like changing a resistor or two to adjust the signal balance into the two output tube sections would do it. I wish I could get a schematic for the Rebel, but Egnater seems reluctant to pass these out.

I would also like to tweak the "Bright" and "Tight" circuits. "Bright" is a little too bright for me, and "Tight" cuts a little too much bass for me.

JWW
 
jwdubois":1j0u6uio said:
OTOH, it seems like a simple mod like changing a resistor or two to adjust the signal balance into the two output tube sections would do it. I wish I could get a schematic for the Rebel, but Egnater seems reluctant to pass these out.
Click to expand...
If it were a simple mod like it seems (to you), then why would Egnater release it without changing it? Are you even questioning your logic?
 
Gino":1d2li20e said:
jwdubois":1d2li20e said:
OTOH, it seems like a simple mod like changing a resistor or two to adjust the signal balance into the two output tube sections would do it. I wish I could get a schematic for the Rebel, but Egnater seems reluctant to pass these out.
Click to expand...
If it were a simple mod like it seems (to you), then why would Egnater release it without changing it? Are you even questioning your logic?
Click to expand...

Signal levels in any point in an amplifier are set by resistor ratios (exception: transformer coupled stages, tuned resonant stages, or filter sections such as the tone stack, not the case here). This takes the form of a gain ratio at an active stage or an attenuation ratio at a passive stage. This includes the signal path of the power amp section. I should be able to add a little attenuation in the path leading to the EL84 side to tone it down a little. To answer your question, yes this should be easy, but I would really like to see the schematic. There could be some aspects about the way that Egnater designed the blend control that would make this more difficult.

My logic is that tube guitar amps are about the simplest electronic circuits on the planet. They have been honed and tweaked over the years, but the same basic designs have been used for 50 years. The art involved (outside of manufacturing considerations) is in the component selection.

JWW
 
jwdubois":g9m32esi said:
Gino":g9m32esi said:
If it were a simple mod like it seems (to you), then why would Egnater release it without changing it? Are you even questioning your logic?
Click to expand...
To answer your question, yes this should be easy, but I would really like to see the schematic. There could be some aspects about the way that Egnater designed the blend control that would make this more difficult.
Click to expand...
The question wasn't whether or not it's easy, the question was if it's so easy then why would it be released this way? I'm not saying it's not ok to question designs or look for ways to improve them, but do not think this thing was designed a week before it was released. A lot of R&D has been put into this little bad boy.
 
another possibel scenario:

Is it a volume increase, or a percieved volume increase because of the added midrange from the EL84s?
 
RockStarNick":2kvoquob said:
another possibel scenario:

Is it a volume increase, or a percieved volume increase because of the added midrange from the EL84s?
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No, it's definitely there. No argument about it. When they had the prototype and it was just a toggle switch you could notice it much easier.
 
Gino":sktj4xa2 said:
jwdubois":sktj4xa2 said:
Gino":sktj4xa2 said:
If it were a simple mod like it seems (to you), then why would Egnater release it without changing it? Are you even questioning your logic?
Click to expand...
To answer your question, yes this should be easy, but I would really like to see the schematic. There could be some aspects about the way that Egnater designed the blend control that would make this more difficult.
Click to expand...
The question wasn't whether or not it's easy, the question was if it's so easy then why would it be released this way? I'm not saying it's not ok to question designs or look for ways to improve them, but do not think this thing was designed a week before it was released. A lot of R&D has been put into this little bad boy.
Click to expand...

That's a fair question. Without tearing my Rebel down (since I can't get a schematic) my guess is that Bruce simply set it up to provide maximum available output power from either output pair with the blend pot set to either extreme and it just so happens that the EL84 side is louder.

If I actually went to the trouble to do something about it I would do something like this on the EL84 side:

http://blueguitar.org//new/schem/misc_mod/pi-m-vol.pdf

If you did it with fixed resistors, you would always be limiting the EL84 side power output. Many people would find that unacceptable, but since I don't run WFO it wouldn't be a problem for me.

JWW
 
John Ewing may be of service to you. His contact info can be found in this forum. Egnater is all about people doing what they want in terms of customizing their amps. However, they may be apprehensive to give you the schematic as you could modify the amp and make it sound like ass. I'm not saying that's what you're going to do, but it's a possibility. So there you are playing an amp that sounds like ass with the Egnater name on it and then they look bad. However, since it looks like you know what you're talking about, they may give you the tube blend section of the schematic. This concept may be patented though. Hell, go look for the patent and see if it has any useful info. Post your results if you end up doing anything to the circuit. Just don't make it sound like ass! :thumbsup:
 
What you are hearing is the gain difference between the tube types. Not gain as in distortion, but simply the sensitivity of the power tubes. It takes a bit more to drive the 6V6 tubes so, consequently, the EL84 tubes sound louder. The only thing you could do is to attentuate the input to the EL84 pair which, in turn, would reduce the headroom in that pair. This would not be a desirable thing to do. I suggest leaving it alone.

Bruce Egnater
 
bruce egnater":3a9w7af7 said:
What you are hearing is the gain difference between the tube types. Not gain as in distortion, but simply the sensitivity of the power tubes. It takes a bit more to drive the 6V6 tubes so, consequently, the EL84 tubes sound louder. The only thing you could do is to attentuate the input to the EL84 pair which, in turn, would reduce the headroom in that pair. This would not be a desirable thing to do. I suggest leaving it alone.

Bruce Egnater
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:worship: Bruce Almighty has spoken!!It was good seeing you guys at Namm!!I like the new toys :D
 
bruce egnater":1odjql6c said:
What you are hearing is the gain difference between the tube types. Not gain as in distortion, but simply the sensitivity of the power tubes. It takes a bit more to drive the 6V6 tubes so, consequently, the EL84 tubes sound louder. The only thing you could do is to attentuate the input to the EL84 pair which, in turn, would reduce the headroom in that pair. This would not be a desirable thing to do. I suggest leaving it alone.

Bruce Egnater
Click to expand...

I am going to leave it alone. The whole discussion was "what if", but it's nice to hear that my speculations were correct.

Now if you wanted to suggest a couple of cap values to reduce the effect of the "Bright" and "Tight" switches, I might get out the soldering iron.

JWW
 
In the GC stuff they use GrooveTubes. GrooveTubes basically relabels other brands. In this case they're JJs.
 
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