Salas DCG3 preamp (line & headphone)

[myleftear]

You probably have read the documentation, as in hificollective ?

pin 1 is input, pin 2 out, C (or 3) GND...
(I don't know about which is 1 or 3, would adhere to the standard, like for the Alps…)
If this is/was not the problem, I'm out of context…

 

[voxxonline]

I did, tried several options too. I will most likely install it in dcg3 and see if it is going to work. Most likely I did something wrong in the first place.

 

[Salas]

What, you connected it on a power output? Inadequate impedance. You also may burn it in that way. Its not a speaker L-Pad attenuator. Or it was a line level output for active speaker?

 

[voxxonline]

Yes at a speaker power output. Fingers crossed it is still working fine

 

[iliverez]

A year later I caught up on DCG3. First power on everything clear, nothing suspicious, measurements ok. After 15mins and VR1 adjustment 0 DC offset without and with the opamp. Temperature inside the heat sink (about 40 minutes powered on is 43C), in open space as in the photo. First impression regarding sound, I could not thank you more!

 

[Cyberpup]

Before you are all done, gently twist together the leads carrying AC. It reduces loop area. The larger the loop area the better the leads radiate signal, which in this case is 50/60Hz hum.

 

[iliverez]

Thanks cyberpup, will do (although I cannot detect any hum with the headphones). This is a temporary connection, to test things. Among others, I have to tidy up cabling a bit, raise the volume pot to fit in the face plate and complete the remote control and VU meters connections. I am concerned a little about the temperature though, maybe I will have to resort to a larger sink.

 

[Salas]

Excellent progress up to now iliverez. Congrats.

 

[Salas]

Yes at a speaker power output. Fingers crossed it is still working fine

 

[voxxonline]

on off switch has led, 24V max. Where can I borrow V to power it?

 

[Salas]

Better not borrow from your DCSTB 17.6V regulated output. Not to mix a potentially interference prone line.
At DCSTB 2200uF C2's pins you will find +V/0V raw DC points to tap. Will almost certainly measure higher than 24V given your mains & transformers.
Put a 10k resistor in series with the switch's red or black thinner wire feed to its LED so to protect it.
Or a 20k trimmer wired like a rheostat (adjustable series resistor) to can control your preferred brightness. Start from midpoint trimmer setting before power on.