With the top cover on, the regulator heat sinks run quite a bit hotter. I'd estimate close to 60C, whereas they were only warm without. Since the dissipation per device is only 1.5W, thermal drop from junction to heatsink should be minimal, so I'm not too worried about it. Overall, the chassis remains only slightly warm and electrolytics aren't getting hot at all. I don't think there's any problem, but it's a reminder that there are tradeoffs packaging in a small chassis.
For a balanced configuration, would it be preferable to replace R7 on each or the two circuits for one channel with a 1K resistor between the two J2 gates?
I don't remember previous balanced finished builds shown here to have included suchlike modifications
This would allow each half of the balanced pair to act as a virtual ground to the other which seems like it would improve the balanced operation. This is the way most balanced instrumentation amps are configured.
I think I will give it a try in my build and see how well it works.
I think I will give it a try in my build and see how well it works.
I had made some relevant simulations few years ago I found in my files. If you mean normal BAL connections as at the picture's left vs those at the picture's right (BAL_RR). There is also a summation amp on both types outputs to aid those sims so ignore it. Don't know, maybe the charts are helpful to you, although theoretical.
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Kind of the combination of these two is what I have in mind. Still with balanced inputs as in the first, but with the feedback resistor(s) connected between the pair instead of to ground as in BAL_rr.
Theoretical results look the same, don't know if there is some benefit with practical circuit halves never being 100% the same due to parts little tolerances. BAL_RR was on how to configure for best connecting an SE source to a BAL amp by the way.
...On the other hand linking the two phases circuits feedback return points with a resistor involves widened loop area vs local resistors to ground. Since its about two sizeable discrete preamps, not like with smd op-amp chips to could make a tiny block. Maybe increased chances of picking interference. You will see how it will work and what you will prefer in practice.
Tying the two R7 resistors together of each channel instead of their going to ground produced a hum in my balanced build. At the time Salas had mentioned to cut the common ground between the two halves of the board to see whether that solved the issue but I did not bother to try and reverted back to R7 to ground.
Is your shunt attenuator a 4 section unit or a two section with the shunt between the phases?
nash
The current 1.03 board is pre-cut (but bridgeable) for ground lane between halves so to expand configurations practicality. Thus easier for him to experiment again on that idea and see.
My build will use a four section attenuator, so fully balanced.
I'm using a separate chassis for the transformer, rectifiers and capacitor bank, so the power coming into the main chassis will be fairly heavily filtered.
But it's certainly something to be aware of.
I'm using a separate chassis for the transformer, rectifiers and capacitor bank, so the power coming into the main chassis will be fairly heavily filtered.
But it's certainly something to be aware of.
Small progress... im waiting a few parts RCA -Pot Tocos 20K- Emi filter-knobs-UP68 Im playing with chinise 2sk170 - 12ma very pleased...
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@nokosokey - Looking good. What did parts/values did you use for C6 and C7? These look larger than then GB kit parts.
@bambadoo - sweet build. That's a pretty big heatsink for the DCG3. I'm not planning anything nearly as big and I'm hoping I have enough cooling. What bias are you running and what are your transistor temps? Thanks.