luvdunhill

come on Dusty, you can do better than that.. that typo almost does the work for you!

Ditto on Fry's. Guess I need to find something online. So, lowered the output resistors to 1 ohm and everything was stable. With the Dynahi current level, the current was shared exactly the same. Just for reference, the variance is 2mV on one side and 5mV on the other. With the insane output current setting (400mA per FET) things tightened up from a 17mV spread on one side, to 4mV and 66mV (my worse-case scenario) to 30mV difference. I think this is just about the limit of how hard I can both push the FETs and my heat sinks. With the 8 FETs, my targets will be 75mA and 200mA, and perform all the same measurements at these points. I gathered the data for dissipation on all the buffer transistors, just need to do some math. They still seem warm to me. Ideally, it would be nice if we could make sure the "faces" of the BJTs point away from each other, as this just exacerbates the heat... I think it would be a worthwhile change, albeit not simple I'd guess.

[ame=http://www.amazon.com/Telemann-Twelve-Fantasias-Gulliver-Violins/dp/B0000007EP/ref=cm_cr_pr_product_top]Amazon.com: Telemann: Twelve Fantasias for Violin Solo; Gulliver Suite for Two Violins: Georg Philipp Telemann, Andrew Manze, Caroline Balding: Music[/ame] The Cleveland Quartet Beethoven Box Set, but particularly the "Razumovsky" Quartets: http://www.concordmusicgroup.com/albums/Beethoven-Quartet-In-B-flat-Major-Quartet-In-F-Maj/

Just had a probe slip and ended in a projectile BJT. That's a first. Just finished replacing the transistors and it's back up and running.

kinda broad question Could you narrow down things to solo, chamber, orchestra, opera, etc? Here's a token recommendation: [ame=http://www.amazon.com/J-S-Bach-Sonatas-Partitas-1001-1006/dp/B00097HE8U/ref=sr_1_3?ie=UTF8&s=music&qid=1246227869&sr=8-3]Amazon.com: J.S. Bach: Sonatas and Partitas for Solo Violin, BWV 1001-1006: Johann Sebastian Bach, Julia Fischer: Music[/ame]

that would be very wise

That would be really cool, could you suggest something simple? I don't mind sacrificing this board once I finish with it to this test I think it would be a worthwhile addition to the boards. I figured a shorting switch would work, but maybe not?

I can. I hesitate to describe the difference as it will be forever recorded in the annals of time and all further impressions will either mirror mine or be polar opposite I'll wait for someone else to take the plunge first.

Cool, all worked out. I'll get with digger945 and see if he can verify (and I'll answer your PM as well Then I'll recalculate the values with 8 output FETs once I get to that point, either way, this won't hold up the board production. Jacob, can we change that bias pot to a pot with series resistor? I think that's the last change to the board. Let's see what you have for changes, and get these boards ordered. Anyone ordering parts from Digikey, or can we tack another $7 onto the R&D budget?

Lead better

nice line of work, switching out LEDs? I can recommend Fitz as an expert LED matcher, if you're ever in the market.

while we have you here ... Seems there are different distortion spectra from the two FB points. Did you compare the two and have a preference? In other words, is the distortion from allowing the diamond buffer and output stage to run open loop "pleasing" in your opinion?

Kevin: You need to also lower the 20K resistors it seems. I cut them in half and raised the pot to 50K. The result is a lot less touchy than raising the pot to 100K, and looks to be a winner.

same as Dynahi, plus the current for the buffers, so 380mA. Could you measure your current draw more exactly for me? Voltage drop across one of the 20 ohm resistors would work.. or measure a few per board and average them.

Think I got it. I'm going to let things warm up for 30 minutes or so, but things look promising. It's kinda hard to measure the gate voltage for digger945 (have to turn the board over and disturb the proper convection of the heat sink), so I'm going to base things on the current draw if this is okay. You'll need another 30mA per board from your PSU compared to the Dynahi, for the buffers, but the output stage will be biased the same, so the heat sinks will be at the same temperature. You should be good to go.

that's good. thanks! no need to grab temperatures. If you don't think the heat sinks for the output stage can take anymore, your instinct is probably right.

what about the PSU heat sinks? If they run hot, is there room to beef them up?

Hey DigiPete and Pars: How much extra heat do you think you can dissipate in your Dyna-? Today's efforts are pretty much geared toward you guys and I'd like some sort of estimate on the lower end bias we need to support. If your heat sinks are pretty much maxed out (cannot hold hand on heat sinks for less than 3 seconds) that's one thing. If they barely get warm, that's another thing.

best damn 1kHz sine wave I've ever heard. Fixing to bump it up to 10kHz, be right back..... bliss...

I can take some measurements for you tomorrow if you'd like, let me know. Now that I've played with the bias, I'm going to recommend to put a series resistor inline with the bias pot. I can calculate the proper value, as there is in fact an upper limit on this value, assuming 4 devices minimum. I replaced the pot with a 50K and still cannot get as low as I'd like (well, as low as *you guys* would like ), so more experimentation is needed. Need to find some 10k resistors, then some desoldering.... then try again, repeat ad nasium.

Using the Squeezebox as source, as I don't have another source with volume control. I'll wire up an attenuator tomorrow. I'm happy with the volume at 50% on the SB. Offset is 0.00mV +- 0.05mV.. unbelievable.

yeah, we've both been staring at amb's beta24 for too long oh, and listening to music now Fostex T50 are driven quite nicely