DC5b volume mod...with pics!

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FLYING V 83
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DC5b volume mod...with pics!

Post by FLYING V 83 » Tue Aug 26, 2014 11:32 am

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
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Image

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

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

dodger916
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Re: DC5b volume mod...with pics!

Post by dodger916 » Sun Aug 31, 2014 4:15 pm

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.

Mk IIA->C+ DRGX head "Cold Sweat" in GTS shell
1966 Fender Pro Reverb
DC-3 head
Orange Dual Terror
EVM loaded Thiele; MS-12 1/2 back
71 SG; 72 Tele; 76 White Strat; 77 LP Custom; 81 Goldtop; 05 Am Dlx Strat; 11 G0 plaintop

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BlackBoxy
Mark III
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Re: DC5b volume mod...with pics!

Post by BlackBoxy » Thu Oct 09, 2014 5:09 am

dodger916 wrote: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

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Don
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Re: DC5b volume mod...with pics!

Post by Don » Thu Oct 09, 2014 6:54 am

dodger916 wrote: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!

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Don
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Re: DC5b volume mod...with pics!

Post by Don » Thu Oct 09, 2014 6:57 am

dodger916 wrote: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
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Re: DC5b volume mod...with pics!

Post by dodger916 » Thu Oct 09, 2014 7:07 am

Don wrote:
dodger916 wrote: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. :oops:

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

Mk IIA->C+ DRGX head "Cold Sweat" in GTS shell
1966 Fender Pro Reverb
DC-3 head
Orange Dual Terror
EVM loaded Thiele; MS-12 1/2 back
71 SG; 72 Tele; 76 White Strat; 77 LP Custom; 81 Goldtop; 05 Am Dlx Strat; 11 G0 plaintop

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dodger916
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Location: Ithaca, NY...10 sq miles surrounded by reality!

Re: DC5b volume mod...with pics!

Post by dodger916 » Thu Oct 09, 2014 7:15 am

Don wrote:
dodger916 wrote: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_ECC83_E ... d=Tungsram

Mk IIA->C+ DRGX head "Cold Sweat" in GTS shell
1966 Fender Pro Reverb
DC-3 head
Orange Dual Terror
EVM loaded Thiele; MS-12 1/2 back
71 SG; 72 Tele; 76 White Strat; 77 LP Custom; 81 Goldtop; 05 Am Dlx Strat; 11 G0 plaintop

Image

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