Vox ac30cc2 mod volume loss

[guitarlos]

Hi,
I completed the modification that many folks recommended and my amp lost a lot of volume-here's what I did: From L. Cadwell. After these changes the amp sound great but I lost a lot of volume. Which of these changes could have caused this? If I undo one or more of the mods do you think I'll get the volume back up? I am using JJ power tube and rec. tube and 3 12ax7 tubes. Please let me know what I should do. Any thoughts and suggested would be greatly appreciated. I did not put a cap in C13 I left it without a cap. The toggle switch for brilliant on the normal channel was broken. I replaced it with spdt 5A 125VAC switch. The original switch was 6A 125VAC. Would this cause a big loss in volume?
Can a be a bad solder that I did?
1 - R6 and R7 are the plate resistors for V1 (Top Boost and Normal channels). In the Custom Classic they are 100K resistors. Change these to 220K resistors.

2 - there is a 120pf bright cap (C13) across the Top Boost volume knob. The "vintage" spec for this cap was 100pf, but to sound more like a 40 year old AC30 with 40 year old speakers I find that 68pf is a more pleasing value.

3 - Vox went with a 56pf treble cap in the tone stack (C16). Changing this to the "vintage" 47pf value very slightly reduces the treble.

4 - they have made the Normal channel fairly useless in tone (way too dark or way too bright) and limited its max gain. Jumper the 330K resistor ahead of the Normal volume pot (R49), change the 220pf bright cap (C12) to a 100pf cap, and then put a 68pf cap across lugs 1 and 2 of the Normal volume pot. This will allow the Normal channel to have more gain and go from a warmer but not too dark sound to a brighter but not too bright sound.

5- I put put a 4.7uf cap in C109 of the effects loop.


THANKS!

[guitarlos]

I wanted to point out that I have to turn the volume on all three volumes all the way up just to get about 1/4 of what it used to be like. I can't play live because it's not loud enough now...bummed.

I tried different power tubes and it was still very low volume. I have Weber copper rectifier and tried it out and still low volume. Could the higher value plate resistors cause a big drop in volume?


Thanks

[alvarezh]

Hi Guitarlos, first of all it would be good to publish the schematic, it makes it easier for us.

Check the operating voltages, if ok, I would suspect you could of messed up something aroud the effect loop. Normally, effect loops interrupt the signal coming out of the pre and into the power section (have not seen your amp's schematic), if for some reason the effect loop jacks are not making good contact you loose all or part of the signal into the power section, hence the low volume.

Warning! this is just a guess, ok?

All the best.

[M Fowler]

jumper the 330K resistor ahead of the Normal volume pot (R49)

This mod sounds suspect to me. Or it's a ground problem chopstick around to try isolate problem.

Mark

[guitarlos]

Hello,

Thank you for responding to this. I have played guitar for 38 years or so but the tube amp interest just began a few years ago. I always had someone do the work for me because I had no time...too much guitar!

I check the voltage and it's fine...I'll look at what I did in the effects loop. Which was I removed the yellow box value 220 and replaced it with a 4.7uf cap. I went back to double check and re-solder the other parts but not the effects loop.

Thank you very much!

Schematic: https://docs.google.com/viewer?url=http ... 2_CC2X.pdf

[guitarlos]

Could the value of the cap that I change in the effects loop cause a drop in volume? I re-soldered the cap and even put the second just case cap that I got and it is still missing a lot of volume.

Thanks

[guitarlos]

I will have to take the amp in to an expert....

Thanks

[guitarlos]

I used 1 watt carbon film 220k resistors. I've read to use 1/2 watt...could this result in volume loss?

Thanks

[guitarlos]

Hi,

It was the resistors that I put in there first...wrong ones. Now the amp works and I can use it for work now too! It's great...loud, thick, clean, unique!

Thanks you guys for your suggestions.

[M Fowler]

Which resistors?

[guitarlos]

R6 and R7 are the plate resistors for V1 (Top Boost and Normal channels). I had put a 1 watt resistor in in each of those spots. I went to radio shack and got 1/2 watt 220k resistors and it came back to life! It's really an amazing sounding amp now. I still don't know a whole lot about working on amps...but it's enjoyable. Gotta be very safe though!

Thanks

[xtian]

Well, you fixed something, but it wasn't because you replaced 1w resistors with 1/2w resistors of the same value. You can just as well put 10w resistors in the same place, and the amp will work just as well.

[guitarlos]

Maybe it was soldering that was bad there? When I put the different resistors I got it right? I don't know but the amp is doing very well. I have to learn more about electricity.

Thank you.

[M Fowler]

It's called cold solder joint.

[alvarezh]

A good lesson to learn from this experience is to do one mode at a time and check it, then go to the next. Never five mods at once, it's harder to find an error.

Enjoy.