GrindingThud

I was just going to swap pin 2 and 3....easy trace cut. Need to wait til Friday for the mod...too much work during the week.

Input pot 10k (shorted for now). I have an interesting issue. I jumpered pin3 to ground (left the offset pins float) on the servo opamp. The output of the amp drifts to just under 2v offset (opamp pin 6 drifts to -19v). Or I can flip it if I drive the output the other way with a battery. -2V offset and 19V pin 6. Is the polarity of the feedback correct?

http://www.mouser.com/Search/ProductDetail.aspx?R=RDEC71E476MWK1C03Bvirtualkey64800000virtualkey81-RDEC71E476MWK1C3B http://www.mouser.com/Search/ProductDetail.aspx?R=FK20X7S1H475Kvirtualkey52130000virtualkey810-FK20X7S1H475K

It lives! Without the servo (still need to add the jumper) it's only got a few mV offset and is dead quiet with cheesy iems Now I've got to figure out the bias....oh, I think I've got it. 150mA across the 1 ohm. Now I've got to get the second channel built. I think this one may be a winner. I'm observing interesting behavior...seems the bias current changes with input pot position. May be because the servo is out, or could be my input wiring. Driving my headphones in mono it sounds great!

Soldering under way. Possible error on board. In the schematic, the positive input of the opa445 is grounded. On the board, pin3 is not connected to anything. Pins 1, 3, 5, 8 are floating. I plan to run a short jumper from pin3 to the nearby .1uf cap ground if it needs it.

Looks like a project weekend! Boards are in. I plan to do one set as throughole and one as SMD. Question...will it mind being run off the KSA 21V supply? My other alternative is the 30V from the Dynahi without modding it.

^^ like he said.... I use these: http://www.mouser.com/ProductDetail/ON-Semiconductor/MPSA56RLRMG/?qs=sGAEpiMZZMshyDBzk1%2fWi%2fPUgtclNldl2ZkToUCMhk0%3d

Mmmm, bacon Oreo:

Like this: http://gilmore.chem.northwestern.edu/kgdynalobalssproduction.pdf

Chambord oxidizes pretty quickly after being open and will eventually turn a nasty brown. Cognac will oxidize also. Scotch is somewhere around 6 months or so after opening. Unopened they last indefinitely.

Its running happily in my SuSy Dynalo with no issues that I've noticed. Provides a nice little startup delay and cuts out if I induce DC on the output.

Doh...I Must have been dazed by staring at purple on purple for too long.

Better batteries than lipstick, Chapstick, or that God forsaken silly putty. Nothing effing worse than silly putty in the dryer! The batteries won't hurt anything, even if they leaked all over, just throw them away even if they work. The could leak later on. If it makes you feel better, wash them again (the sheets not the batteries).

Hand traced and it looks ok to me. Subtle differences in the schematic vs the board: C2 is 100uf in schematic vs 47uf on board. C1 is 4uf in schematic vs 4.7uf on board. The top two tiers of the triple darlington emitter resistors float in the schematic and are output referenced on the board. Also noticed the ground in and out connections, the 100uf and .1uf cap grounds don't have thermals...not sure if you typically use them there or not. What's the gain set to on this one? I having trouble figuring that out. I plan to get a proto board spun when I have time...much more compact than the KSA5.

I have those for my pinball machine boards. I might try those on my next build.

Have the files been posted for this one yet?

Foo! Mistakenly swapped +/- on one of my boards... Fortunately I caught it quick and only the opamp and 7915 smoked. Was a slow day so I decided to do some chassis work and biasing.

Still have not finished installing the balanced input jacks, but the protector circuit fits nicely in there.

Ready for test. 1st install will be in my SuSy Dynalo.

Bummed I missed it live...thanks for the link. Would not want to miss a really good one.

As a kid in New England, once a year everyone would put "large stuff" at the edge of the road by their driveway for the town to pick up and bring to the dump. We'd run around before the town would do pickup and rummage through everything and grab what we thought was the good stuff. Tubes, speakers, and tube amps were my favorites. I'd pull every tube out of everything I could find. What makes me sad now is how many desireable tubes we popped with BB guns. For a long time as a kid I had the coolest Leslie 251 organ amplifiers and cabinet speaker.....they had the schematic on the side and I learned how to solder while fixing them up. Why my parents put up with it, I'll never know.

Aphex Twin posted a bunch of previously unreleased and demo material....been listening to this all day: http://104.236.16.63 https://soundcloud.com/user48736353001

Did more testing today and built up the second board, but used MPSA and the THAT on perfboard instead of the Chinese fooo I have in the other. Board came up ok and tweaked easily to a couple mV all around prior to installing the servo. This was a little easier to troubleshoot on the big heatsinks. Seems the balanced output is dead quiet with low gain (20K feedback) and either SE or balanced input, but SE output hisses loudly between either side and ground regardless of input. I think I'm missing something obvious.....where's captain obvious when you need him. Anyone have any ideas or experience using the amp with single ended output?

No, but now I plan to!

Get a cheap one from Amazon with a USB port: http://www.amazon.com/Sony-PS-LX300USB-Stereo-Turntable-Black/dp/B0015HOFZI/ref=sr_1_1?s=electronics&ie=UTF8&qid=1422485763&sr=1-1&keywords=usb+turntable http://www.amazon.com/PLTTB3U-Turntable-Recording-Digital-Software/dp/B002PF4YKU/ref=sr_1_7?s=electronics&ie=UTF8&qid=1422485906&sr=1-7&keywords=usb+turntable