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BA-3 As Preamp
BA-3 As Preamp
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Old 3rd February 2016, 01:19 PM   #1041
Russellc is offline Russellc  United States
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BA-3 As Preamp
Quote:
Originally Posted by KevinHeem View Post
I had a hard time telling them apart at first. I'm starting to get a handle on their differences. I think they are both pretty neutral, really letting the cartridge and Pearl II shine through. I think the Joule is a little more sweet, the BA-3FE a little more transparent. Of course my bias leans towards the one I built. Although I've really enjoyed the Joule preamp, I'll be showing it the way to the door (helping to fund new projects).

Yes, looking forward to seeing how P3 affects the sound. I guess I would start with 1 turn on the 25 turn pot (which is centered now), but in which direction do you think I should start?
There is a post somewhere (this thread maybe?) in regard. I remember that each side turns opposite of each other, one left, one right. The thread referred to "turning towards a resistor" that is on the board.

Others piped in that it wasn't as simple as all that, as they found while measuring it wasn't linear, but the shift from 2nd harmonic to third and vice versa may occur several times. The writer of the thread (who escapes me just now) noted that one way tended to sharpen and draw in the stage, the other blew it up larger but that is got somewhat fuzzier.

I am trying to search for that. I am searching my posts, as I remember inquiring, since I have both BA-3 FE and BA-3 Power amp, which I should start with and so forth, the pre, the amp, or both.

Russellc
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Old 3rd February 2016, 02:02 PM   #1042
Dennis Hui is online now Dennis Hui  Canada
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BA-3 As Preamp
Jim did a P3 adjustment video:

Adjusting P3 - a video

Dennis
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Old 3rd February 2016, 02:46 PM   #1043
Russellc is offline Russellc  United States
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Quote:
Originally Posted by Dennis Hui View Post
Jim did a P3 adjustment video:

Adjusting P3 - a video

Dennis
Yes, and it appears Kevin has equipment to do so. The post I refer to is us that do not...something I need to take care of.

Russellc
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Old 3rd February 2016, 02:53 PM   #1044
starbender is offline starbender
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Is it possible to adjust harmonics with Truerta software?
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Old 3rd February 2016, 02:59 PM   #1045
Hikari1 is offline Hikari1  United States
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Yes. All you need is a sound card or audio interface and the ability to feed a 1kz test tone. just fiddle with p3 and watch the 2nd harmonic go up and down. Make sure to reset bias and offset after...p3 effects the offset.
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Old 3rd February 2016, 03:04 PM   #1046
starbender is offline starbender
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Quote:
Originally Posted by Hikari1 View Post
Yes. All you need is a sound card or audio interface and the ability to feed a 1kz test tone. just fiddle with p3 and watch the 2nd harmonic go up and down. Make sure to reset bias and offset after...p3 effects the offset.
Excellent!
Thanks.
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Old 3rd February 2016, 03:13 PM   #1047
nashbap is offline nashbap  United States
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Quote:
Originally Posted by Salas View Post
9.45dB if I got you right
Yes, thank you.
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Old 3rd February 2016, 03:14 PM   #1048
Hikari1 is offline Hikari1  United States
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Quote:
Originally Posted by Russellc View Post
There is a post somewhere (this thread maybe?) in regard. I remember that each side turns opposite of each other, one left, one right. The thread referred to "turning towards a resistor" that is on the board.

Others piped in that it wasn't as simple as all that, as they found while measuring it wasn't linear, but the shift from 2nd harmonic to third and vice versa may occur several times. The writer of the thread (who escapes me just now) noted that one way tended to sharpen and draw in the stage, the other blew it up larger but that is got somewhat fuzzier.

I am trying to search for that. I am searching my posts, as I remember inquiring, since I have both BA-3 FE and BA-3 Power amp, which I should start with and so forth, the pre, the amp, or both.

Russellc
I think I wrote that thread....and yes, for my the adjustment was not linear. You can't go 5 turns this way on one channel and 5 turns that way on the other to get the same result. Also, midpoint may not be a happy medium. But it depends on your jfets and mosfets and matching,etc. perhaps the best way to set it (assuming the jfets are well matched) without a scope or software is to measure the values of the resistor network effected by p3 and get them even channel to channel. If that makes sense. At least then you have a starting point for measurement and tweaking by ear. I preferred to 2nd and third harmonic about even...not 2nd dominant. Others with different rooms or speakers might disagree.
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Old 3rd February 2016, 03:55 PM   #1049
chatziva is offline chatziva  Greece
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Quote:
Originally Posted by Salas View Post
9.45dB if I got you right
Salas, I was looking for 2SK2013/2SJ313 spice models, can I borrow yours?

Thanks
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Old 3rd February 2016, 04:33 PM   #1050
Salas is offline Salas  Greece
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Sure

.model 2sk2013 VDMOS(nchan Vto=1.94 Kp=.77 Cgdmax=60p Cgdmin=5p Cgs=140p Cjo=0p)
.model 2sj313 VDMOS(pchan Vto=-1.94 Kp=.85 Cgdmax=120p Cgdmin=16p Cgs=165p Cjo=0p)

*I found them in a ZenMod's post
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