Doug Self Preamp from Linear Audio #5

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Thanks!

I'm finding several parts, like the aluminum electrolytic capacitors (UES1V101MPM), to be out of stock at mouser and digikey. I found a few on arrow.com, but not all of them and it seems like many are back-ordered until Feb 2019. :( Looks like I'll be waiting a while.
look at TME
They dispatch in New Zealand
 
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Thanks HADIHF for the I/O schematic. Very Nice. Needed for troubleshooting. Can anyone take a quick measurement of the output of the 12v reg on their boards and report your voltage? Mine measures 17vout with 19vdc input. I expect the 19 in that is what the power supply is. I checked for orientation and then replaced it but still the same. Everything works okay but it's just bugging me.
BTW build your own cables everything can be purchased from Amazon. Much cheaper in the long run.
 
Thanks HADIHF for the I/O schematic. Very Nice. Needed for troubleshooting. Can anyone take a quick measurement of the output of the 12v reg on their boards and report your voltage? Mine measures 17vout with 19vdc input. I expect the 19 in that is what the power supply is. I checked for orientation and then replaced it but still the same. Everything works okay but it's just bugging me.
BTW build your own cables everything can be purchased from Amazon. Much cheaper in the long run.

Reg output should be 12VDC and input should be 17VDC
 
Thanks HADIHF for the I/O schematic. Very Nice. Needed for troubleshooting. Can anyone take a quick measurement of the output of the 12v reg on their boards and report your voltage? Mine measures 17vout with 19vdc input. I expect the 19 in that is what the power supply is. I checked for orientation and then replaced it but still the same. Everything works okay but it's just bugging me.
BTW build your own cables everything can be purchased from Amazon. Much cheaper in the long run.

Hi Freecrowder - some reports of regulator oscillation in thread #1058 and onwards. This results in the o/p voltage sitting ~2 V below the i/p voltage, which sounds like what you are seeing. Suggested fixes were additional capacitance - one user suggested soldering SMD caps directly on the regulator pins, on the underside of the board.
 
Just an update. A 22uF tantalum directly across output to common solved the problem. I also notice that both pass transistors on the DC PS run much cooler now. You couldn't hold your fingers on them for more than 5 seconds before.

Hmm ...

I've never experienced this problem. Perhaps some 12v LDO parts are more susceptible to oscillation than others. In any case it is a reasonable thing and I will add a part pad to the IO PCB. Thank you for sharing!
 
MadInventor,

I was toying with the idea of using a pair of the Amgis #L01-6354 transformers shown here at Digikey:

L01-6354 Amgis, LLC | TE2254-ND | DigiKey

With each of the transformer secondaries wired in parallel to get the needed current.

Incidentally, what part number is the Q2 device??

Anyone have a secondary source for this xformer? Seems DigiKey is either offline, or they have an error on the quantity available. Equivalent Mouser part # ?

redjr
 
Anyone have a secondary source for this xformer? Seems DigiKey is either offline, or they have an error on the quantity available. Equivalent Mouser part # ?

redjr

Mouser isn't a dealer for those transformers. As far as I'm aware Digikey is the only dealer in North America for them. I just bought on from their Canadian website this week and can still order more of them. Maybe there's a glitch in the US site right now?
 
Here is a graphic rendering of the power supply PCB. It measures 159mm (6.25 inches) x 63.5mm (2.5 inches).

DSELF_PWR_SUPPLY_PIC.jpg


DSELF_PWR_SUPPLY_01.jpg

Carl,

Could you point me to the latest BOM for the original project PSU board pictured above? Thx.

redjr
 
I have been listening to this pre off and on now for about a week. I'm comparing to a broskie Aikito with 6sn7's. Was very impressed with the overall sound very smooth on upper frequencies. It does present a problem though in my system which uses some older Maggies. When I use this pre my speakers bottom out in the bass range at a lower volume than my Aikito. It doesn't really sound like the bass extends down any deeper but I'm assuming it must. Even when I turn on the tone controls with bass gain turned all the way down the speakers bottom out sooner. May look at using sub with the maggies.