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Old 2nd December 2011, 03:51 PM   #521
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Quote:
Originally Posted by generg View Post
And I pour the wine on the heatsinks of the preamp, I suppose.....?
After a bottle or two or three of wine, you will be seeing quadruplet copies of everything. Adjustment will be no problem and if you spill a little, it will help help cool things off a bit, maybe even present opportunity for new build.
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Old 2nd December 2011, 04:09 PM   #522
generg is offline generg  Germany
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Good friends, devily advices.......
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Old 4th December 2011, 08:36 PM   #523
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Quote:
Originally Posted by kenpeter View Post
Before I realized BA2 front end was already obsoleted by BA3,
I had thrown a few of my zany ideas at the older topology...
Shunt regulated tail, etc etc...
Click the image to open in full size.

I totally goofed the negative end of C207, obviously bootstrap
has to be wired as Nelson originally showed it, driven from off
board. Otherwise, has anyone tried the shunt tail pair trick yet?

The points of merit theoretically are: Twice open loop gain
compared to the series high impedance tail. And automagic
offset cancellation maybe good enough to get rid coupling
cap at C203?

We are holding both halves of Q201 at same current and
drain voltage, one might expect offset to be improved?

----------------------------------

There was some misunderstanding earlier about Q204 as
a high impedance tail, it is a low impedance active tail.
Intended to shunt away all but a constant tail current.

Also improves the gain of Q201b to unity, up from 1/2.
Thats where the doubling of open loop gain comes from...

-----------------------------------

I gotta fix a McIntosh 2100 with almost this same front
end topology. Turned upside down, and BJT's for FET's,
and no bootstrap, but otherwise unmistakably similar.
Tempted to try a BJT-ishy version of the shunt tail.

It too has a 10uF output cap, might be getting rid of...

Last edited by kenpeter; 4th December 2011 at 09:01 PM.
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Old 5th December 2011, 03:05 AM   #524
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Why don't you give it a try and see what you get?

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Old 5th December 2011, 02:14 PM   #525
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Just to update on that grounding debate several pages back. The Salas voltage reg grounds (one for left and one for right) were connected to the star ground of the power board supply (see Nelson's BA-2 design for this). One ground wire is connected from this star ground to the BA-3 ground. One wire also connects this star ground to the -ve loudspeaker output.
No hums, just as quiet as the grave.
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Old 10th December 2011, 03:16 PM   #526
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After reading all the accounts of those out there using BA-3 FE as a stand alone gain stage behind a passive volume knob and in front of an F-4 I got to wondering.......when using my F-5 with speakers of lesser efficiency I have replaced the B-1 with another preamp I have (Audio by Vanalstein Super Pass III) which has gain to get a little more volume out......

....then I wondered if I could just put a BA-3 FE behind the B-1, the have the BA-3 (with all its gain, up to 30 dB I understand) feed into the F-5 solving the gain problem....BUT..I assume there is a reason no one else has mentioned this yet? (Not to mention upcoming F-5 turbo) Any thought on this would be appreciated!!! (Iam building a BA-3 both in a complete amp as well as one of these front end versions for a future F-4 build....for which I am also building Pumpkin....does it ever stop? I hope not.

The setup with B-1. BA-3 FE to F-5 would also give me "P3" adjustment capability without building "R-1" version of F-5 I am hoping...

thanks for any info,

Russellc

Last edited by Russellc; 10th December 2011 at 03:22 PM.
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Old 10th December 2011, 04:03 PM   #527
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Lots of gain happens everyday among some of the biggest names in Audio. That is exactly what Nelson is addressing in his B1 writeup. Its not that its wrong, but often wasted. Why not get rid of some of that gain for more linearity and lower distortion. Using F5 as output may not reveal true character of Ba3 FE. Just guessing though. Hopefully more experienced members will chime in.
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Old 10th December 2011, 04:45 PM   #528
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Quote:
Originally Posted by buzzforb View Post
Lots of gain happens everyday among some of the biggest names in Audio. That is exactly what Nelson is addressing in his B1 writeup. Its not that its wrong, but often wasted. Why not get rid of some of that gain for more linearity and lower distortion. Using F5 as output may not reveal true character of Ba3 FE. Just guessing though. Hopefully more experienced members will chime in.
This is kind of what I thought. But, I am building them and I do have an F-5.........Probably nothing revolutionary but I could try.

There is No wasted gain with the particular set of speakers, about 83-84dB efficiency, it needs more....not 30dB more but that's likely adjustable.

While the F-4's frontend may be more transparent than the F-5, the F-5 is no slouch at letting the character of front ends come through. I understand there is a different relationship with the F-4, which has no gain than it would be with the F-5 which does. but if you look at it in combination with the B-1 it wouldnt be that different from any pre with gain, so I thought it might be interesting to try together with the F-5.

Unless, like Buzzforb says some more experienced member can see a reason NOT to try it, instability, etc?
on so on. Thanks for the response!

Russellc

Last edited by Russellc; 10th December 2011 at 04:47 PM.
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Old 12th December 2011, 02:59 PM   #529
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Does anyone know what the markings mean on the K2013 and J313?

I have a few of these:
K2013 is marked Y 9.0 or Y 1.F.
J313 is marked Y 9.Z or Y 1.F.

Y is I believe Vgs(off) of -1.4~-2.8 but I don't know about the rest.
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Old 12th December 2011, 03:44 PM   #530
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