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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Doug Self Preamp from Linear Audio #5
Doug Self Preamp from Linear Audio #5
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Old 12th October 2018, 05:22 PM   #1211
Carl_Huff is offline Carl_Huff  United States
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Originally Posted by Freecrowder View Post
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!
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Old 12th October 2018, 06:48 PM   #1212
batteryman is offline batteryman  United Kingdom
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Doug Self Preamp from Linear Audio #5
Quote:
Originally Posted by Carl_Huff View Post
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!
Never come across this myself either. Must be that particular LDO.
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Old 13th October 2018, 08:32 PM   #1213
redjr is offline redjr  United States
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Doug Self Preamp from Linear Audio #5
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Originally Posted by Carl_Huff View Post
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
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Old 13th October 2018, 09:09 PM   #1214
jwilhelm is offline jwilhelm  Canada
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Originally Posted by redjr View Post
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?
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Old 13th October 2018, 09:23 PM   #1215
redjr is offline redjr  United States
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Doug Self Preamp from Linear Audio #5
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Originally Posted by jwilhelm View Post
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?
Thanks. I'll check with the Canadian site.
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Old 13th October 2018, 09:37 PM   #1216
redjr is offline redjr  United States
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Doug Self Preamp from Linear Audio #5
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Originally Posted by Carl_Huff View Post
Here is a graphic rendering of the power supply PCB. It measures 159mm (6.25 inches) x 63.5mm (2.5 inches).

Click the image to open in full size.

Click the image to open in full size.
Carl,

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

redjr
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Old 13th October 2018, 09:58 PM   #1217
asuslover is offline asuslover  Romania
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Doug Self Preamp from Linear Audio #5
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Originally Posted by redjr View Post
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
True, error with chrome browser, I tried internet explorer, no more quantity/price error.
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Old 14th October 2018, 02:39 PM   #1218
Carl_Huff is offline Carl_Huff  United States
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Originally Posted by redjr View Post
Carl,

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

redjr
Here you go ... Dropbox - DSelf_PwrSupply.zip
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Old 15th October 2018, 02:32 AM   #1219
redjr is offline redjr  United States
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Doug Self Preamp from Linear Audio #5
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Thanks.
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Old 15th October 2018, 07:16 PM   #1220
Freecrowder is offline Freecrowder  United States
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Doug Self Preamp from Linear Audio #5
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.
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