Rodeodave

With differential measurement - which better corresponds to what the membrane sees if I'm not mistaken - there should be some cancellation, right. Guess I'll be breaking out the analyzer over the holidays again, currently too busy listening when time permits

I have now pulled some numbers from the circuit. And I took more pretty pics, which I‘ll start off with: Now for some numbers: PSU voltages: V_HV_pos=402V, V_HV_neg=-403V V_LV_pos=14.88V, V_LV_neg=14.88V Current sources: Right channel voltage drop over the RN60C 49R9: V_ccs_pos=857mV, I_ccs_pos=17.17mA V_ccs_neg=856mV, I_ccs_pos=17.15mA Left channel voltage drop over the RN60C 49R9: V_ccs_pos=862mV, I_ccs_pos=17.28mA (adjusted to 857mV/17.17mA) V_ccs_neg=856mV, I_ccs_pos=17.15mA On the left side the i

Input and output wiring in place: And I'm happy to report that the amp is working! No smoke, no arching, no shrapnel. After like an hour of warming up and fiddling with offset and balance, I gave it a listen with my 007mk1. Wow. I'm treating pin 1 as analogue ground btw, and circuit ground goes to the chassis earth ground point via a CL60 thermistor. Zero noise, zero hum - with my gear at least. Bias is still around 17mA for all channels, I'll get some more accurate numbers when I set up the optocoupler servo. Not sure if I'll go up to 20mA, this amp

Thanks for the encouragement, y'all. Getting closer now:

HV and LV wiring is now in place: Next up is input and output wiring.

Progress is slow during the week, but thanks to home office I can get some soldering done over the lunch break. For connecting the HV and LV PSUs and the amp boards I'm going with a star ground, held in place by wire wrap and soaked with solder: Here's how the manifold looks like in circuit: There's good clearance too: Although the currents are substantially lower than what I'm used to from solid state, I took care to have equal lengths of fat wire for each of the HV and each of the LV supplies. I hope the grounding scheme is going to be quiet, I passiona

Can you post a pic of the whole PSU so we can see cap and diode orientation and voltage references and so on?

Goop: Bolted down: Fits like a glove: Good clearance: And the full monty:

The amplifier boards are now fully populated, including the front end Jfets, for which I picked pairs of 2sk170bl from the same batch with an Idss of 7.3 and 7.4mA. Using a benchtop PSU supplying 20.00V DC I then set the constant current sources to 17.00mA: It's going to be interesting to see how much this will go up with the full B+.

Okay, moving on. Here's how I wired up the transformer: And here we see the unloaded secondary voltages: Here the PSU boards are mounted to the front plate for heatsinking. The power resistors (500R and 16k) will be used to load the PSU for testing: And finally, the moment of truth: One more view from above: So far, so good.

If I recall correctly, they are Molex Eurostyle Terminal Blocks UL certified for 300VAC, which would mean 425V DC peak. I'm not sure if there are terminal blocks rated for 600V with a 5.08mm pitch. Since I'm using the amplifier boards with a ground plane, i used a couple of layers of Kapton tape at the bottom of the terminals and used very little solder in order to avoid the arching that's been reported with these boards. Edit: I just realized that the terminal blocks aren't the Molex that I thought I had installed. I guess I should replace them, which is not going to b

Here are some more build pics:

Thanks, I'll be adding 10k resistors at the inputs then. I'm making good progress with my build after it lay dormant for over a year:

Want impedance volume pot is everyone using? And those of you who aren't using a volume pot in their amp, are you terminating your inputs to ground with a resistors other than the 500k on the circuit board?

He probably meant yoke, the springy part connecting the two drivers. Looks like you added some clamps to the springs, maybe in order to damp out some resonances?