Hello guys, I still read here and there but it's been a while since i post. I was just wondering if anybody could help me out.
I recently picked up a YBA-2B, the kind that uses 6V6's. The amp is not as loud as I think it should be. I'm guessing it should be at least at loud as a Princeton Reverb, even more since I got a 15" speaker.
The amp is only using one half of V1, so I was thinking about wiring up the unused triode so my question here is could it be done this way? by shorting pin 1 to pin 7, moving the wire that comes from my board to pin 1 to pin 6, adding and grounding a cap and a resistor with the same value as the first half of the triode to the cathode on the second?
Does that make sense and would it work? Thx for your input.
This amp might not have as much GAIN as you'd like, but it should be plenty LOUD. There might be something wrong if the volume isn't enough to rattle windows. Is the circuit voiced OK for guitar? I mean the highs aren't rolled off?
The amp sounds good it just isn't very loud. I do get some of the low frequencies that shake the ceiling lights a bit but I play guitar through it. I've played the el84 version and it was incredibly loud. Mind you it was the 45 watt version. This one is around 22, but still... It should be louder I think.
I don't see a grid leak (to ground) resistor on the input section. If the input jacks are switched to ground when empty, the open one acts as the ground connection for a 50% voltage divider/attenuator before the grid of the 1st stage. If that's what you have I would re-wire to eliminate that attenuation. Not a huge difference but why have it standing in your way.
Not sure if the proposed change would work or not. It appears to be a triode in series topology but no attentuation in between and no second triode plate load resistor if I am interpreting it correctly.
Putting them in parallel is a no-brainer though. Do the cathode as you suggest, jumper pin 2 to pin 7 (grid to grid) and pin 1 to pin 6 (plate to plate) and give it a whirl!
ampgeek wrote:Not sure if the proposed change would work or not. It appears to be a triode in series topology but no attentuation in between and no second triode plate load resistor if I am interpreting it correctly.
Putting them in parallel is a no-brainer though. Do the cathode as you suggest, jumper pin 2 to pin 7 (grid to grid) and pin 1 to pin 6 (plate to plate) and give it a whirl!
Good luck!
Dave O.
Would I need to half the plate and cathode resistor values?
Not for the first shot at it. Single plate load resistor and replicate the cathode condition of the first triode.
In essence you will be pulling ~2X the current of a single triode through the same plate load resistor with the parallel plan. This will give something less than a ~2X increase in amplitude of the signal going off to the next stage.
Can't do the math in my head right now but IIRC you will get something like a 50% to 75% increase in gain. Not huge...but...definitely noticeable.
Play it for a while and keep tabs on the PT temperature. While you will only be increasing the load by a couple of mAs (at max), it could push an already marginal PT over the edge.
If this were mine I would put the normal channel from a black face Deluxe Reverb in this chassis. I don't know what kind of PI is in this circuit but I am sure a long-tail-pair would drive the 6V6s harder. Use both halves of V1 ala Fender DR - You can use the existing front panel for the volume treble- bass. Rewire the Pi to match the same circuit. Keep the cathode bias or go fixed.
Thx guys, will do as you suggest Dave. I wont get to mess with it until I get some parts tho' but I will report back. I don't think the PT will have any issues but will keep an eye on the temperature.
This change will not make your amp louder. It will just have more gain. I would change all the tubes as a weak tube can have give a low volume characteristic... Try this and report back...
Personal preference really. I find that with 25'ish uf cathode bypass and doubling up the triodes the tone gets a little "flubby" to my ear. I typically voice the other one with a more Marshall'y plan (0.68 to 5.0 uf) to balance it out.
As you know, halve the cathode resistor if you don't split them and you are good to go!
I fully agree that you should be chasing volume problems at the other end as suggested. But...if you are shaking lamps...it can't be too anemic.
Fire it up and measure the voltage drop across the cathode resistor. Divide by the resistor value (250 ohm/10w) to get mA. Look for..maybe..40 to 60 (?).
