luvdunhill Posted June 27, 2009 Author Report Share Posted June 27, 2009 Is Kevin building the prototype as well, or give any input on circuit tuning? 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. Quote Link to comment Share on other sites More sharing options...
digger945 Posted June 27, 2009 Report Share Posted June 27, 2009 Wrt Conrad MF30-75's(@3"x12") I have 16 outputs at 75mA each per HS and it's only just warm. I feel like these could easily handle double the heat. The devices are spread out along 10 of the 12 inches. When cranked to 100mA the devices get a little hotter but it seems to make little difference to the HS's themselves. I guess if I had a temp probe I could give some more useful info. The thermal resistance is .37 C/Watt for 80 Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 27, 2009 Author Report Share Posted June 27, 2009 Wrt Conrad MF30-75's(@3"x12") I have 16 outputs at 75mA each per HS and it's only just warm. I feel like these could easily handle double the heat. The devices are spread out along 10 of the 12 inches. When cranked to 100mA the devices get a little hotter but it seems to make little difference to the HS's themselves. I guess if I had a temp probe I could give some more useful info. The thermal resistance is .37 C/Watt for 80 Quote Link to comment Share on other sites More sharing options...
DigiPete Posted June 27, 2009 Report Share Posted June 27, 2009 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. Ok, here is what I have: two Dynahi PSUs to drive the Dynamite (4-ch) XFMR - two 80VA - 2 x 30VAC(RMS) @ 1.33A each So, first assumption is bias is low enough that I can power the dang DynaFet or DynaPhat (balanced). Now I have toyed with the idea of only populating half the output devices, and I can do that if power consumption will be too high. And this is the original schematic that Kevin posted in Wize. Now as for the heatsinks for the Dynahi: They get rather warm, and I would say there is not a lot of extra capacity for dissipation beyond the standard Dynahi output transistor heat output. There may be some but in my 12x12x3 Parmetal case the Dynamite gets toasty. Quote Link to comment Share on other sites More sharing options...
Icarium Posted June 27, 2009 Report Share Posted June 27, 2009 Haha I like the DynaPhat as the balanced Dynafet's nomenclature. Any opposed? Quote Link to comment Share on other sites More sharing options...
digger945 Posted June 27, 2009 Report Share Posted June 27, 2009 DynaPhat, I was thinking QuadraFET. No, no opposition here, DynaPhat is .... well Phat. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 27, 2009 Author Report Share Posted June 27, 2009 I would say there is not a lot of extra capacity for dissipation beyond the standard Dynahi output transistor heat output what about the PSU heat sinks? If they run hot, is there room to beef them up? Quote Link to comment Share on other sites More sharing options...
DigiPete Posted June 27, 2009 Report Share Posted June 27, 2009 what about the PSU heat sinks? If they run hot, is there room to beef them up? The psu heat sinks are cooler and could take more. I could take temp readings on various parts if that would help? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 27, 2009 Author Report Share Posted June 27, 2009 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. Quote Link to comment Share on other sites More sharing options...
DigiPete Posted June 27, 2009 Report Share Posted June 27, 2009 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. I remember the output transistors being fairly toasty (I want to say this was at 65ma??), so running even more heat would really get them hot Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 28, 2009 Author Report Share Posted June 28, 2009 (edited) 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. Edited June 28, 2009 by luvdunhill Quote Link to comment Share on other sites More sharing options...
DigiPete Posted June 28, 2009 Report Share Posted June 28, 2009 what's the draw per board (each rail) when biased as you mention? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 28, 2009 Author Report Share Posted June 28, 2009 what's the draw per board (each rail) when biased as you mention? 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. Quote Link to comment Share on other sites More sharing options...
DigiPete Posted June 28, 2009 Report Share Posted June 28, 2009 will do Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 28, 2009 Author Report Share Posted June 28, 2009 Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted June 28, 2009 Report Share Posted June 28, 2009 I'm using different fets on the prototype, but if you make the bias pot 100k you should be able to get down to 250ma. Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 28, 2009 Author Report Share Posted June 28, 2009 I'm using different fets on the prototype, but if you make the bias pot 100k you should be able to get down to 250ma. 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. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted June 28, 2009 Report Share Posted June 28, 2009 That also works for me. Sounds sooooooooo nice with hd800's... Wish someone would allow me to buy connectors so that i could go balanced. (hint hint) Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 28, 2009 Author Report Share Posted June 28, 2009 That also works for me. Sounds sooooooooo nice with hd800's... Wish someone would allow me to buy connectors so that i could go balanced. (hint hint) 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? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted June 28, 2009 Author Report Share Posted June 28, 2009 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? Quote Link to comment Share on other sites More sharing options...
Pars Posted June 28, 2009 Report Share Posted June 28, 2009 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. Marc, Don't know as I haven't completed mine yet, or even gotten to the point that I could test it (slow build mode ). I am using a Pesante Dissipante 2U 300 case for an SE build, so should be good heatwise. I will be using a single sigma22 as the PSU, with a 120VA (I think, might be 160?) SumR tranny. Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted June 28, 2009 Report Share Posted June 28, 2009 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? I have a switch that allows me to change between the two. So the answer depends on the day and on the music... And the phase of the moon and the temperature outside And how much booze... Some people really like amplifiers without global feedback. Especially when female voices are involved. (no, not the B&C) Quote Link to comment Share on other sites More sharing options...
justin Posted June 28, 2009 Report Share Posted June 28, 2009 can you actually hear a difference when you flip the switch? Quote Link to comment Share on other sites More sharing options...
DigiPete Posted June 28, 2009 Report Share Posted June 28, 2009 can you actually hear a difference ... heh.... the eternal audio question Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted June 28, 2009 Report Share Posted June 28, 2009 can you actually hear a difference when you flip the switch? Switching with the power on is a gigantically bad idea. Maybe next time i go in there i will add a couple of extra resistors to make sure the switch does not temporarily disconnect all the feedback. Quote Link to comment Share on other sites More sharing options...
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