carl huff
hi carl do you still have parts for doug self preamp regards. richard woollcott aka ampman..rwoollcott97@gmail.com
hi carl do you still have parts for doug self preamp regards. richard woollcott aka ampman..rwoollcott97@gmail.com
Richard,
Please check your private messages here on this forum and/ or your gmail account. Thanks!
carl huff
Hi carl i seem to have lost 3 pots from my original order so do you 3 you can sell me regards ampman.
Hi carl i seem to have lost 3 pots from my original order so do you 3 you can sell me regards ampman.
Hi Carl, i just plug all the part together for the first time today (PSU, Preamp, I/O, selector) no music yet, just oscilloscope with 1000Kz/150mV at the input.
I noticed after 10 minutes that the PSU is warm at the BD139 (61℃) and BD140 (50℃). I have 200mA (17V+) and 180mA (17V-) with the selector at 1er input (XLR).
With no load @ the PSU, i don't have this issue.
Hmm, did you put a dab of thermal grease under the BD139/BD140 devices and their heatsinks?
It sounds to me that you are not getting a good thermal couple between those transistors and their respective heatsinks.
Please note that some BD139/BD140s have an exposed metal mounting surface that must be electrically isolated from it's respective heatsink using a mica or silicon insulator.
Ha, ha ... Yes! I should proofread what write.
Here is an example: TO-220 Silicone Insulator 10 pcs.
Yes i have silicone between, may be not enough grease..i will put little more.
On youtube there was a test. Silicon has a catastrophic thermal conductivity. Mica is first choice! Moreover a good piece of mica costs 10 cent.
Thermal pads like silpad are a composite of silicone and a good heat conductor as filler. The silicone rubber can conform to the surfaces of device and substrate, the filler particles increase the thermal conductivity. Mica cannot conform to the surface as well, but has a reasonable bulk thermal conductivity. Diamond film would be really good for this, if it was affordable, as it has extreme thermal conductivity (better than metals).
diyralf we are not talking about silicon.
diyralf we are not talking about silicon.
I changed the SK 104-2 ( External Length - Metric 25.4mm) with SK104-6 ( External Length - Metric 63.5mm) heatsinks and the temperature drops of 10℃ on each side. But now i am too hight for my 1U chassis....i am curious to now if they are any other option than to change the heatsinks.. Carl, did you check for any oscillation on your boards ?? Thanks
I have been using this power supply in projects for at least the last six plus years. I cannot remember oscillations ever being a problem. How confident are you that the NE5534s are good?
I guess they are.... i bought them 2 week ago from Digikey...what is the best way to be sure they are good ??
Coming from Digikey I expect they are. What makes you think that you have oscillation? Can you see it on an oscilloscope?
Carl, may be this is the answer....
The NE5534AN (PDIP-8) is obsolete. They sent me the NE5534AP (PDIP-8).
Looking at the datasheet of both, the Operating Supply Voltage range are different:
NE5534AN : From +/- 3 V to +/- 20 V
NE5534AP : From +/- 5 V to +/- 15 V
what is your thought?
i didn't check with an oscilloscope.
The NE5534AN (PDIP-8) is obsolete. They sent me the NE5534AP (PDIP-8).
Looking at the datasheet of both, the Operating Supply Voltage range are different:
NE5534AN : From +/- 3 V to +/- 20 V
NE5534AP : From +/- 5 V to +/- 15 V
what is your thought?
i didn't check with an oscilloscope.
What is the approximate total cost to build one of these preamps? I saw the BOM and looks like quite a few parts.