DC5b volume mod...with pics!

[FLYING V 83]

So my amp's been ear-blasting loud at gigs with the Global Master just barely on at 1, and same with both channel volumes.
Decided to do the volume mod and pop a 12AT7 in v1 to tame the gain channel, and the results are amazing!
It's a much more user-friendly amp now, and the gain channel is smoother and less gritty.
Now I'm running the Global Master volume on 5!!
Wound up with these settings and couldn't be happier:
Clean channel: gain 7.5 pushed in, treble 6, mids 2, bass 2, presence 2, reverb 5, volume 3
Gain channel: gain 3, treble 10, mids 2, bass 2, presence 5, reverb 5, volume 3

Sounds like a blanket was taken off the speaker, and all my pedals sound better too!
So, on to the pics....

Removed the 4 top screws, disconnected the speaker & reverb leads and pulled the chassis

Found the resistor, measured at 180kohms (supposed to be 220k) and snipped it off

Put the 12AT7 in v1 and put it all back together.
Whole job took about 1/2 hour start to finish.

 

[dodger916]

Here's what I did to tame the gain on my DC-3 lead channel, which has the same preamp tube assignment as the DC-5. I installed a JJs ECC823 in V1. The 823 has a 12ax7 in the first triode (1st Rhy gain stage) and a 12at7 in the 2nd triode (1st lead gain stage). It worked very well to reduce gain, and is recommended by Eurotubes for DCs .

Recently I did a lead channel mod listed on this Board (removed a resistor), and it really opened and smoothed the Lead. Then for grins, I installed a newly-acquired vintage Mesa SPAX (12ax7) on V1 and blammo: liquid lead like Mark IV. I literally cannot believe my ears, the sound is so fluid and forever-sustain.

 

[BlackBoxy]

Here's what I did to tame the gain on my DC-3 lead channel, which has the same preamp tube assignment as the DC-5. I installed a JJs ECC823 in V1. The 823 has a 12ax7 in the first triode (1st Rhy gain stage) and a 12at7 in the 2nd triode (1st lead gain stage). It worked very well to reduce gain, and is recommended by Eurotubes for DCs .

Recently I did a lead channel mod listed on this Board (removed a resistor), and it really opened and smoothed the Lead. Then for grins, I installed a newly-acquired vintage Mesa SPAX (12ax7) on V1 and blammo: liquid lead like Mark IV. I literally cannot believe my ears, the sound is so fluid and forever-sustain.

second triode is 12au7, can't bear any reissues in V1 or 12at7, it slow the signal , to tame the clean chanel gain, i use CV4004, mullard at7 in V4, and i get great results!

i recently swapped rectifier slow regular diodes to uf5408, and this amp came to life

 

[Don]

Then for grins, I installed a newly-acquired vintage Mesa SPAX (12ax7) on V1 and blammo: liquid lead like Mark IV. I literally cannot believe my ears, the sound is so fluid and forever-sustain.

I have a small collection of vintage 12AX7s that I should try in mine!

 

[Don]

Here's what I did to tame the gain on my DC-3 lead channel, which has the same preamp tube assignment as the DC-5. I installed a JJs ECC823 in V1. The 823 has a 12ax7 in the first triode (1st Rhy gain stage) and a 12at7 in the 2nd triode (1st lead gain stage).

BlackBoxy is correct- the second triode in the ECC823 is closer to a 12AU7 than a 12AT7. It does work to tame the amp.

 

[dodger916]

Here's what I did to tame the gain on my DC-3 lead channel, which has the same preamp tube assignment as the DC-5. I installed a JJs ECC823 in V1. The 823 has a 12ax7 in the first triode (1st Rhy gain stage) and a 12at7 in the 2nd triode (1st lead gain stage).

BlackBoxy is correct- the second triode in the ECC823 is closer to a 12AU7 than a 12AT7. It does work to tame the amp.

Thanks, guys. My mistake.

And yes, in V1 OR V2 it tames only the lead channel nicely!

 

[dodger916]

Then for grins, I installed a newly-acquired vintage Mesa SPAX (12ax7) on V1 and blammo: liquid lead like Mark IV. I literally cannot believe my ears, the sound is so fluid and forever-sustain.

I have a small collection of vintage 12AX7s that I should try in mine!

Don: I learned something useful: the vintage SPAX7 I installed is a Tungsram made in Hungary from the 70s or 80s. I've since bought a couple more, and they have really improved both my DC-3 and my C+.

Tube Monger sells them: http://www.tubemonger.com/12AX7_ECC...=Y&sort=9&cat=6&show=10&page=1&brand=Tungsram