Salas DCG3 preamp (line & headphone)

Member
Joined 2018
Paid Member
Attenuate one channel?

Enjoying my dcg3 very much, however due to room constraints I am nearer the left channel than right.

To make right seem louder, is there an R to be altered to attenuate the left channel? Or is this not possible?

If it is possible, any maths to calculate R value for a given DB reduction?

Kind regards
 
diyAudio Chief Moderator
Joined 2002
Paid Member
@Jim

R6/R7 ratio controls the gain. Gx=1+(R6/R7). GdB=logGx*20. But nobody would normally fix some imbalance in the channels themselves. Its not practical for when something changes location even a little. Your position included. Do it with a hardware balance pot or in the audio driver's mixer software with the virtual balance L-R slider if you are mainly listening from a computer/streaming source.
 
Merry X-mas :happy1:

I'am building this 300b SE amp. and just ordred the last parts i need (Toroidy SE with glued airgab OPT's & a main's transformer too + the GH300b tubes themselves)... Uhh €$€$€$ lots of them, glad i already have presents in house now :D...

Wondering if someone ever tried this wonderfull pre. with a SE tubeamp. can't wait to try it out, but it will take some time until i will be there through!

I believe Salas is n'old tubeguy himself :wave2:

Jesper.
 
Hi Salas

My DCG3 has been in storage for around 2 to 3 years and I've read that when not in use the insulation between capacitor plates can break down which may damage the circuit capacitors when full voltage is first applied (after the lengthly down time).
Is it wise to think about reforming the caps by slowly increasing the voltage and can this even be safely done without damaging other components in the DCG3?

Thanks
 
Last edited:
diyAudio Chief Moderator
Joined 2002
Paid Member
2-3 years isn't that long. Does not exceed some new bought caps storage time in warehouses. Better don't power it up slowly though. The voltage specs of the Pana FC's inside are higher than what they will see anyway. Power it up normally without being connected to a system, check inputs and outputs DC offsets, and leave it on for few hours. Then power it down for five minutes and up again, recheck offsets. If all is well it should be good to hook up.
 
Hi All,

i just finished basic testing and settings of the DCG3 And DCSTB.
here are some values after waring up for 30 min and DC offset tunned.

with R10 :7.5 R
volt @ r10 right channel: 1,112v (148mA)
volt @ r10 Left channel: 1,051v (140mA)

temp right channel @ M1: 33°c, M2 :33°c, M3: 32°c, Q1:33°c, Q2:32°c
temp Left channel @ M1: 33°c, M2 :33°c, M3: 31°c, Q1:34°c, Q2:33°c

PSU Sink max 37°c

i found the offset quite steady around ov without OPamp.
OPamp in in place : quite steady too around 0.5mv

Tomorrow , i will connect it to my ACA, then to M2 Clone , if all good and silent i will do final wire arrangment .

Dear experts, if you see anything wrong in these values , please advise .
 

Attachments

  • q1.jpg
    q1.jpg
    818.9 KB · Views: 475
  • q2.jpg
    q2.jpg
    601.2 KB · Views: 419
  • q3.jpg
    q3.jpg
    856 KB · Views: 411
  • q4.jpg
    q4.jpg
    484.6 KB · Views: 407