digger945
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Posts posted by digger945
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Just now recieved the board. I will mount it to my heatsink tomorrow.
How thick was your L bracket Marc?
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You make my woodworking skills look like a popsicle ashtray made by a kindergartner.
I really get a woody (bonus!) every time I see nice dovetails.
You must share what kinda jig you use. I once owned a Leigh jig but the ex did something with it. Too complicated anyways.
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The Conrad MF30-100 would work great with a Parmetal 12x12x4" enclosure.
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Well, I would recommend helping out the servo somewhat, otherwise it's a bit slow as it has to overcome the fact that the MOSFETs aren't so complimentary, so it would depend on your definition of warm up.
From what I've seen, it looks like 5 minutes is about the minimum for things to really settle down and the bias to drop down from the turn-on peak to steady state. During this first 5 minutes, 200mA extra current isn't all that uncommon (worse case), before the negative tempco of the MOSFETs starts to work its magic. This will also depend on how large your heat sinks are, I'd presume. During the next 5 minutes after that, it will hit the point where it becomes rock solid, only varying around 10mA during this period.
Anyways, I have written down 478R / 518R for one test and 478R / 523R for another. Worse case, just install one pot... I think with 470 / 510 it will work just fine.
That roughly parallels the time you really need for the Dynahi. The frequency of the filter for the opamp integrator is 0.05Hz so yea it's pretty slow to react to input. As you mentioned it would be wise for anyone using this design to allow some time for things to settle in as they warm up.
On a side note, Jacob has stated to me that the Uber controller may have input offset monitoring incorporated into the design.
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That sounds good Marc. I feel confident that, with proper matching as you say, this can be built without the input bias pots, and the opamp can more than handle any small offset after warmup.
Good show, I can't wait to get started.
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I like that better than holding a probe next to a resistor lead and accidentally piercing the solder mask and making contact with the ground plane (as your trying to hold both probes with one hand and adjust with the other). Be nice to have something that diggs in and wont slip. I will be looking for a pair of those R.
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The moskido is close to the 24V Aikido HP amp, same tube input but a different SS output. No board for the moskido that I know of. Aikido kit can be ordered with most everything except tubes and PS, and Donald gave a link to some affordable 6gm8's, antique electronic supply iirc.
I really like the 24v Aikido, it's a very fun amp to listen to and tinker with, without having to worry about HV.
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Have a good one CJ. Wish I could meet you at le tub and see your ugly noggin.
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In light of your budget deficit you could substitute a Gamma 1 full config for the time being.
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True. I have 2" Aavids on mine as opposed to the stock 1.5".
Still they get only warm even when hooked up to the Dynamite via umbilical and having the EHHA tapped directly to the board.
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I put a DMM in series with each of the rail supply lines and measured the current drawn from the sigma. It was about .35A per rail to supply both boards with the heaters on to make sure everything is conducting properly. I let them sit on for about 2 minutes to see if anything would drift.
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I haven't had time to do much with the EHHA lately. I remember adjusting until I had .23V across the output resistors. I can plug it in again and do some measuring if you guys want, can't seem to find a certain pink baggy for another project atm.
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The heaters on the EHHA are on a seperate PS.
For the pair of EHHA boards all plugged in and running I get 350mA per rail (that's 2 boards together).
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I am sure with a large enough transformer, say minimum 100VA, you won't have any problems. I have run both EHHA boards and two Dynahi boards from one Sigma22 with an 80VA transformer with no problems(HP's plugged into both while playing music). The transformer does get moar warm this way but not stinking hot.
What size toroid do you have Smeggy.
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Dude, have a good one.
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DynaPhat, I was thinking QuadraFET.
No, no opposition here, DynaPhat is .... well Phat.
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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
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...unbelievable.
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Unfortunately, that assumes the devices are heatsinked. My rectifiers are running pretty warm at drawing 1A... It would be a huge PITA to have to use an off-board bridge.
What about a dedicated unregulated PS just for the outputs, leaving the S22's to power everything else. I think you know where i'm going.
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OH my bad. I thought you meant 1A per device. You mean 1A total right.
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I mainly meant that I couldn't get the gate voltages down low enough to put the outputs into a somewhat decent bias, like you had originally targeted, somewhere in the 150mA range.
Think I'll wait until you do some more testing and probing with a load on the output to comment further. My little proto was not quite as organized.
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1A is gonna be 30W or the limit of these devices. When I was playing with the one I built it got the toroid pretty hot in a hurry.
What do you have on the gates? I had difficulty getting the gate voltages down with the adjustments and values used. It would be good to change some values around to be able to get the gates down a little, and in a more comfortable adjustment zone. I'll do some tinkering later.
Sexy lookin' board.
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ooo, that looks nice.
Group Build: Dynafet
in Do It Yourself
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Ditto on everything Marc said.
This one of Gilmore's children does not play well with others. It's hot headed for sure, and if left unattended will burn the house down.