Between F4 and F5

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timbarnes

timbarnes

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Joined 2004
timandmarina.com
Russellc said:
Making sure I understand here, you are running the BA-3 right into F4, kind of like some have done with SE 45 triode amps?
Russellc
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My configuration is as follows:

  1. First Sound passive "preamp" does source switching and volume
  2. BA-3 with its own power supply is used as preamp gain stage
  3. F-4 unmodified provides current amplification

An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
 
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Russellc

Member
Joined 2003
Paid Member
timbarnes said:
My configuration is as follows:

  1. First Sound passive "preamp" does source switching and volume
  2. BA-3 with its own power supply is used as preamp gain stage
  3. F-4 unmodified provides current amplification

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main.php
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OK, looks like the BA-3 is minus its output stage, and kind of a smaller transformer for its power supply? what are the rcas for on the BA-3?

Russellc
 
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Russellc

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Joined 2003
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Timbarnes,
OK staring at the board pic in the diy store and your pic, I believe the inside set of RCAs are the inputs and the outside set are the outputs? So I figure the passive pre/selector device goes into the inputs and the outputs are feeding F-4, no?

Last questions concern power supply, appears to be some Panasonic caps, assuming 50 volt models, cant make out size in pics resolution. Transformer also appears smaller than would be the case for the BA-3 as a power amp, and it appears you have a board of rectifiers there for rectification.

Could you give some specs on these power supply parts? I assume a less stiff supply is needed when using BA-3 as a preamp sort of capacity. this appears to be a great way to do F-4, driving with a passive pre even!

Since the volume is controlled by the passive unit in front of the BA-3 "pre", I suppose it sits like it does as a "power amp", no volume control on it, only constrained by what is fed to it via the passive's volume pot?

Thanks in advance for any tips on this set up!

Russellc
 
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timbarnes

timbarnes

Member
Joined 2004
timandmarina.com
Russellc said:
Timbarnes,
OK staring at the board pic in the diy store and your pic, I believe the inside set of RCAs are the inputs and the outside set are the outputs? So I figure the passive pre/selector device goes into the inputs and the outputs are feeding F-4, no?
Click to expand...
That's right. I just treat it as a gain stage.
Last questions concern power supply, appears to be some Panasonic caps, assuming 50 volt models, cant make out size in pics resolution. Transformer also appears smaller than would be the case for the BA-3 as a power amp, and it appears you have a board of rectifiers there for rectification.
Click to expand...
Actually the caps are 35V, which isn't quite enough, but no explosions so far...

My understanding of the BA-3 appears to differ from yours a bit: I think of it as a front-end gain stage that can be paired with various output stages, including BA-1, BA-2, or F4. In any case, that's how I'm using it.

Could you give some specs on these power supply parts? I assume a less stiff supply is needed when using BA-3 as a preamp sort of capacity. this appears to be a great way to do F-4, driving with a passive pre even!
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The power transformer is about 50VA, I think at 24V, which is too high really. 18V or maybe 20 would be better. I use a CRC filter as Nelson suggests for his power amps, and I'm sure the caps (22,000uF) are complete overkill. But they were left over from a bulk buy for the F4, so I used what I had.

The rectifier is a leftover board from a gainclone I built ages ago.
Since the volume is controlled by the passive unit in front of the BA-3 "pre", I suppose it sits like it does as a "power amp", no volume control on it, only constrained by what is fed to it via the passive's volume pot?[
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I wouldn't describe it as a "power amp", because it really only provides voltage gain. All the power is provided by the F4. I would describe the BA-3 as the active part of my preamp, where the gain and switching are provided by the passive control unit. In a more "normal" implementation, the BA-3 would be combined with the switching and volume control in a single box with its own power supply - then it would be indistinguishable from a preamp.

I could just as easily connect the output of the BA-3 to any power amp (although I might have too much gain). Before I had the BA-3 I used a JBOZ in the same way, and before that a pair of 5532s.

Tim
 
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