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BA-3 As Preamp
BA-3 As Preamp
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Old 31st May 2014, 07:23 PM   #641
sheep is offline sheep  Canada
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Can I used power BJTs in a BA-2 configuration? I would just adjust the TL431 for @1.4 volts for biasing into class B and use the BA-3 as the driver.
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Old 31st May 2014, 09:45 PM   #642
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naah ......... for class B bjt you need different biasing methods ; in short - sensing htsnk temperature , to avoid gray smoke
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Old 1st June 2014, 05:49 AM   #643
Hikari1 is offline Hikari1  United States
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Maybe....iam running a little less bias right now too. Iam going to let it play for a couple days...maybe raise the rail voltage and bias. I can take it up to 28v rails and still have 5v of drop out. Right now iam noticing more detail and less slam and bass. But it sounds extremely good, just a bit delicate. Better detail on cymbals and piano sounds more true. But perhaps not as much drive and kick. Could be the bias and rail voltage. But iam going to give it some time before making a judgement.
OK, I've given the superreg 24hrs with the BA-3. Here's what I think:

Superreg has more detail than the LM317/337 psu. This is the most obvious difference. With the volume control maxed out on the BA-3/F5 I could hear a bit of noise from a few feet away from my 91DB efficient speakers. Quiet but there. With the Superreg I have to put my ear up to tweeter to hear anything. So perhaps the noise floor has dropped a bit.

Overall it is an improvement...small but noticeable. Makes the system a little more lively and imaging seems locked in a bit better. It seems to have lost a little tonal density...sounds a little thinner, just a little. This may be due to tighter bass or less bass bloom. "Clean" is the word I would use. Seems like some of the bass and "slam" is returning as it runs in. It seems to be loosening up a little.

Also, I was running 30V rails w/the LM317/337 combo. Now I am running 25V rails due to the greater dropout of the superreg (5V or greater is recommended). I am guessing this is kind of a step backwards (I assume more rail voltage is better) then a step forwards with the superreg.

Should all you guys w/LM317/337 regs on your BA-3 ditch them for the superreg? It's your call. I am happy, glad I did it.
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Old 1st June 2014, 12:46 PM   #644
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shunt is my poison
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Old 1st June 2014, 02:01 PM   #645
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If I swap a transformer from one project to another I could have enough overhead voltage to try a shunt in the BA-3... I wonder, that would be interesting...
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Old 1st June 2014, 02:12 PM   #646
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If ...
http://www.diyaudio.com/forums/pass-...ml#post1466712

while we are there .........

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......

(talking about ........ once I mounted watering can instead of TV antenna on the roof , naturally with antenna cable connected to it ........ just to tease my neighbors .......... they have strange look few days ............ )
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Old 15th June 2014, 06:36 PM   #647
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With preamp off, should I be able to turn P1 P2 resistance to zero?
Negative rail, lowest on trimmer measures 100ohms. I ran into issue, neg rail
On power up measures -24v the becomes -5v. I pulled the board out and going through
All the part vaues and shorts.

P1 and P2 are 1K, Im using fairchild for Q3 Q4
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Old 15th June 2014, 07:20 PM   #648
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Sorry, measured wrong end of resistor

What resistance should I measure at R3 if P3 100ohm is set midway?
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Old 15th June 2014, 07:51 PM   #649
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psu common for both channels ?
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Old 15th June 2014, 08:51 PM   #650
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Sorry, measured wrong end of resistor

What resistance should I measure at R3 if P3 100ohm is set midway?
R3 and r4 should have same resistance across them when p3 is midway.

What are you using for a psu? If you dont have 24v positive and 24v neg out of the psu you have issues. Dont hook it up to the board.
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