GrindingThud

Kewl

I'll need to double check gain values and position and try again. I tried dropping the 200K to 20K to get I think 3:1 (kept the original cap) and it did not seem to change the noise any....so I assumed I dorked something up along the way or have a noisy part somewhere in the front end. I'm assuming weird symmetric noise because it's much much quieter on the balanced output than from either leg to ground. I may try singles for the 2sa1349/2sc3381 before I tear it down too far. What is the recommended singles for those and are they unobtanium too? I'm liking the THAT340 more and more but come this far on this boad and determined to figure it out. I appreciate your help on all these amps and for making them available, I'm having a blast building them up.

As I wait for the enclosure, I tried hooking headphones up and running some sound through it. Seems I may have a problem with noise (hiss)...huge hiss. The hiss is much quieter listening across the balanced output than a single side to ground, but still hissy. When listening to a side, the noise is less if I short the same side input to ground directly. Input grounded through the pot makes no change in noise. Thoughts? One thought I had was that my input sand is crap. I may try to spin a small mezzanine board to drop that340 in place of the jfets and use mpsa in the associated input leg like in the new board.

Ok, I've got power (one board assembled). The smoke did get out the 1st time though. Q22 (BC556B) died on power up and the Negative rail sat at ~-5V. Powerup was in the dual track config. I swapped to the untracked config and changed the transistor and it came up with some mystery smoke but otherwise ok. Then swapped back to tracking config and it still works. I looked all over the board and can't figure out where the mystery smoke came from.....but it did smell transistory. The 1K resistors are not on this board either...should those be spliced in? or only necessary if the current limit transistors are in (not installed now and no plans to put them in). Nice strong +/- 30.0. ---- Edit: had the time and went and did a quick amp board checkout. I don't have full sized heatsinks yet, so these were short tests. I was able to tweak the offset across positive and ground and negative and ground to be symmetric and about 12mV. After I put the servo in it brought it to around 1mV balanced and each side to ground. Very nice. When I went and measured the bias current (voltage across the 10R output resistors) I was getting a pretty consistent match for all N and P devices in the same channel (6mA device to device), but across channels overall (O+ to O-) there is about 150ma difference. Right now one side is 550mA and the other is 400mA. Is there a way (or is it even necessary if output DC is nil) to get the sides the same?

This one? http://gilmore.chem.northwestern.edu/boards/dynahibal9.zip

JB is 300V/mil

I'm a Chesapeake sailor. This is from one of our races earlier in the year:

Yes, JB weld has better conductivity. It does not conduct electricity, it is an insulator. I may use that on the other board...got a bunch of it.

I'm assuming that a little super glue and a shrink wrap blanket is ok for jfets?

I'll post pics as I go.

I did on the other two. Only the amp units had all the holes....I mounted it on the PS board for fit. I'm thinking of putting it in this single chassis: http://www.diyaudio.com/store/amplifier-chassis/full-width-40mm-heatsinks/standard-amplifier-chassis-maximally-vented-4u.html

But it was so much fun. I bought long enough screws to use nuts on the back. I'll fix it prior to assembly.

46 M3 taps later.....I begin to wonder why I wanted offboard sinks (yes it will be on the other side when assembled):

Try this:

Yea, that's what I'll probably do for test until they come in.

Did you have any luck locating a 47uf ceramic? I've been hunting and can't find one greater than 10V.

Cool

//edit// Found the 1N914 above.....never mind. Very cool board, thanks! ------- What are all those little diodes on the board? Jumpers? gt

Thanks! I should have checked for a new version 1st.

What that N channel on the board that drives the relay? http://gilmore.chem.northwestern.edu/protector.jpg http://gilmore.chem.northwestern.edu/protector.pdf http://gilmore.chem.northwestern.edu/dynapower2.jpg

I've got a bunch of BC546B left over from the Dynahi PSU, would that be suitable in this circuit?

Should be plenty of room in the case, I'll need to get one of these built up. . Might try and squeeze one in my dynalo build too. Thanks.

Should I have one of these on the Balanced Dynahi, or is it ok to run without one?

Werd

Woogawooga