Zen Mod thanks for the info. This time the proper answer is the easier to implement. One day there will be something I know that you need to know......
Evan
Evan
I have a few questions:
1) When putting a volume pot in front of the BA-3, what value should I use...10K, 20K, 50K or 100K?
2) When using a volume pot, leave R1 in place and do not use R2?
3) How do you set the 100 ohm pots without a distortion analyzer?
Thanks...
1) When putting a volume pot in front of the BA-3, what value should I use...10K, 20K, 50K or 100K?
2) When using a volume pot, leave R1 in place and do not use R2?
3) How do you set the 100 ohm pots without a distortion analyzer?
Thanks...
1. ideally 50 to 100x greater then Rout of previous stage ; nothing related with BA3 itself
2.leave them both in place ; handy to be there , so eeny weeny Jfet is knowing where it's placed in the world
3. prior to placing it on pcb , be sure that wiper is in mid position - same resistance from mid to both outer pins ; then solder it on pcb and forget
2.leave them both in place ; handy to be there , so eeny weeny Jfet is knowing where it's placed in the world
3. prior to placing it on pcb , be sure that wiper is in mid position - same resistance from mid to both outer pins ; then solder it on pcb and forget
be sure to have bleeder resistors after output caps ; as drawn , FE is part of amp itself , so they aren't necessary
when stage used/packed standalone , they must be implemented[/QUOTE]
Zen mod could you go further with this. If using the ba3 balanced would resistors go from the + out and the - out to ground? From + out to - out? What value?
You can guess I am having problems with my bba3 front ends when I removed them from the amps and gave them their own power supplies.
Thanks, Evan
when stage used/packed standalone , they must be implemented[/QUOTE]
Zen mod could you go further with this. If using the ba3 balanced would resistors go from the + out and the - out to ground? From + out to - out? What value?
You can guess I am having problems with my bba3 front ends when I removed them from the amps and gave them their own power supplies.
Thanks, Evan
Finished the ba3-pre, but not able to bias it up last .25v across R10..
Do you short the input at the PCB or at the rca jacket? Tried both but same .25v.
P1 and P2 are 500 ohm. Should they be 1k?
Do you short the input at the PCB or at the rca jacket? Tried both but same .25v.
P1 and P2 are 500 ohm. Should they be 1k?
Vdi,
What are you using for mosfets? Fairchilds? They may need 1k pots. Mine required lots of turns to get the bias to come up with a 1k pot. Shorting the inputs either way works. I did it at the pcb. Are your jfets bl grade?
What are you using for mosfets? Fairchilds? They may need 1k pots. Mine required lots of turns to get the bias to come up with a 1k pot. Shorting the inputs either way works. I did it at the pcb. Are your jfets bl grade?
Hi Hikari1,
Yes on both counts. Using the Fairchild mosfets and the Jfets are BL grade.
I have four 1k Vishay trimmers, so should be able to replace them tonight.
Only issue is that the 1k trimmers have off-set legs. I can make them work. 🙂
Are you liking the BA3-pre?
Thanks,
Vince
Yes on both counts. Using the Fairchild mosfets and the Jfets are BL grade.
I have four 1k Vishay trimmers, so should be able to replace them tonight.
Only issue is that the 1k trimmers have off-set legs. I can make them work. 🙂
Are you liking the BA3-pre?
Thanks,
Vince
Hi vdi_nenna,
I have had my running extensively for some 2 month now, and I am very satiesfied.
Fluid, detailed non aggressive are some words that come to mind.
It is running with an F-5, and I have never had anything better.
I used 180R and got exactly 4 times amplification.
The PSU comes from Thel in Germany, and is just a large capacitor bank, with 8 Panasonic 3300 uF FCs pr. side, IXYS hexfreds and a 100 nf filmcap at the output.
I use Linar parts and Fairchilds, and Mundorf white 10 uF speakercaps at the output.
Best regards
Arthur.
I have had my running extensively for some 2 month now, and I am very satiesfied.
Fluid, detailed non aggressive are some words that come to mind.
It is running with an F-5, and I have never had anything better.
I used 180R and got exactly 4 times amplification.
The PSU comes from Thel in Germany, and is just a large capacitor bank, with 8 Panasonic 3300 uF FCs pr. side, IXYS hexfreds and a 100 nf filmcap at the output.
I use Linar parts and Fairchilds, and Mundorf white 10 uF speakercaps at the output.
Best regards
Arthur.
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Hi Arthur,
Thanks for sharing your impressions. My one "fear" if you will, was that it could be aggressive, but with the P3 adjustment and proper test gear, one could adjust it to a certain flavor. I have P3 set to a mid-point.
I'm also using the Mundorf white 10uF cap. Will listen to it with the Mundorf alone, but later by-pass it with a Dayton Foil cap to see if there's any difference.
Thanks,
Vince
Thanks for sharing your impressions. My one "fear" if you will, was that it could be aggressive, but with the P3 adjustment and proper test gear, one could adjust it to a certain flavor. I have P3 set to a mid-point.
I'm also using the Mundorf white 10uF cap. Will listen to it with the Mundorf alone, but later by-pass it with a Dayton Foil cap to see if there's any difference.
Thanks,
Vince
Output caps
I know many think it is crazy, but the caps needs to burn in.
Interesting what you think of the bypassing.
I know many think it is crazy, but the caps needs to burn in.
Interesting what you think of the bypassing.
This is from the second post of this thread.
I set my unit up using 2 sets of +- salas regulators and two transformers to power the balanced ba3 front ends. These front ends have been in service for some time and performing fine.
I set dc offset before the output caps and all seemed OK until I hooked the new preamp up to the amps....Hummmmmm. One channel at a time would sometimes be OK sometimes not. Both channels hum like crazy. Grabbed my volt meter and there is dc offset after the output caps??? I have not the ability to understand this.
Thanks again for the help, Evan
Vince,
I like mine. Compared to the jfet BOZ it has more control and is more extended in bass. Wider soundstage too. It shares the same basic tonality as the Jfet boz...actually, I think they are more similar than different. It's just the BA-3 is "better" in almost every aspect. But they are definitely from the same family.
I was, however, surprised by the lack of gain in my system. Jfet BOZ has far more gain when the BA-3 should have more on paper. Also, I am running mine at 30V 317/337 regulation. Nothing too fancy.
I like mine. Compared to the jfet BOZ it has more control and is more extended in bass. Wider soundstage too. It shares the same basic tonality as the Jfet boz...actually, I think they are more similar than different. It's just the BA-3 is "better" in almost every aspect. But they are definitely from the same family.
I was, however, surprised by the lack of gain in my system. Jfet BOZ has far more gain when the BA-3 should have more on paper. Also, I am running mine at 30V 317/337 regulation. Nothing too fancy.
I have once had a similar problem in a guitar amp. The amp was buzzing and humming very loud sometimes.
I have never seen it before, but the silver mica that was blocking the DC in the tonestack, put pulsating DC through in random patternes.
I changed the cap, and the problem was gone.
I dont know if a larger film cap is able to do the same thing, but it is easy to check.
Else you must be able to trace if the noise is comming from an earlier stage. If you dont have a scope I think you could be able to measure where with a DMM set to AC mV. Most will only measure up to 100 - 300 hz, but much of the noise will probably be in that area.
Best regards
Arthur.
I have never seen it before, but the silver mica that was blocking the DC in the tonestack, put pulsating DC through in random patternes.
I changed the cap, and the problem was gone.
I dont know if a larger film cap is able to do the same thing, but it is easy to check.
Else you must be able to trace if the noise is comming from an earlier stage. If you dont have a scope I think you could be able to measure where with a DMM set to AC mV. Most will only measure up to 100 - 300 hz, but much of the noise will probably be in that area.
Best regards
Arthur.
It is the R13s power resistors.
According to theory we should get a higher amplification factor, but we dont 🙂
According to theory we should get a higher amplification factor, but we dont 🙂
bleeder resistors from output side of caps to GND ; then you'll not measure DC offset ( which isn't there , per se , but you must have those resistors to prevent pops and zaps)
regading hum - everything can be the culprit
each case (chassis) to safety gnd-ed , in every case (chassis) audio gnd NTC-ed to chassis
Was able to set one channel's bias and off set, but the other starts off with 8v+. It starts to drop when adjusting p1 and p2, but the jumps up to 13v and just increases.
I can set the bias voltage across r10 and it stays, but offset is erratic.
Is it a bad pot?
I can set the bias voltage across r10 and it stays, but offset is erratic.
Is it a bad pot?