There are plenty of threads on the burning amps, but none on just the BA-1 FE as a stand alone preamp that I was able to locate. Starting this in the hopes it is needed....if not, ohhhh welllll 
I have spare Antek AS-1220 and AS-1228 transformers, as well as multiple unbuilt Salas BiB kits and a few original peter daniel PS boards.
Here's my questions, to start:
Lightly ( LM317 ) regulated or shunt regulated power supply? ( I haven't built a shunt regulated PS yet )
How much gain will the BA-1FE make?
Can the BA-1 FE gain be easily adjusted?
Would a certain value of volume pot would be preferred? I have alps blue velvet 20K and 100K on hand already.
If this thread doesn't get deleted I fully intend to use it to ask a large amount of stupid questions that other people will greatly benefit from.
I have spare Antek AS-1220 and AS-1228 transformers, as well as multiple unbuilt Salas BiB kits and a few original peter daniel PS boards.
Here's my questions, to start:
Lightly ( LM317 ) regulated or shunt regulated power supply? ( I haven't built a shunt regulated PS yet )
How much gain will the BA-1FE make?
Can the BA-1 FE gain be easily adjusted?
Would a certain value of volume pot would be preferred? I have alps blue velvet 20K and 100K on hand already.
If this thread doesn't get deleted I fully intend to use it to ask a large amount of stupid questions that other people will greatly benefit from.
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-reg whichever you prefer ; I always prefer shunt
- find resistors around input gates, marked 10K and 47K ; their ratio si gain of stage
-yeah , easily
-say that 20K pot is better, having input impedance of BA1 stage in account ...... and it's dominated by value of 10K resistor , already mentioned
- find resistors around input gates, marked 10K and 47K ; their ratio si gain of stage
-yeah , easily
-say that 20K pot is better, having input impedance of BA1 stage in account ...... and it's dominated by value of 10K resistor , already mentioned
An externally hosted image should be here but it was not working when we last tested it.
I made the FE once but never listened. BA-3 came in between.
Jfets are removable!
I found this in the article, on gain, but I'm not sure which parts to omit for stand-alone preamp use:
R201 through 204 form the balanced inputs networks. R201 = R203 and R202 = R204, and
the gain is R203/R201. Compensation capacitors C201 and C202 form the high frequency
roll-off for the gain, and while C201 is not strictly essential, it helps to retain the balanced input
common mode rejection figure at high frequencies. If you are interested in higher gain
figures, adjusting the values of R201 and R202 is a good place, as it minimally disturbs the
frequency compensation.
Thank you for the help
R201 through 204 form the balanced inputs networks. R201 = R203 and R202 = R204, and
the gain is R203/R201. Compensation capacitors C201 and C202 form the high frequency
roll-off for the gain, and while C201 is not strictly essential, it helps to retain the balanced input
common mode rejection figure at high frequencies. If you are interested in higher gain
figures, adjusting the values of R201 and R202 is a good place, as it minimally disturbs the
frequency compensation.
Thank you for the help
Attachments
+D is your output
you don't need C207 (that;s node to connect out of amp , for bootstrapping ; if you don't know what bootstrapping is , just ignore it
also , put bleeder resistor from output side of C203 (where D is ) to GND , to ensure that cap is always discharged , important not to zap amp when fiddling with interconnection
10 to 100K will do the job
you don't need C207 (that;s node to connect out of amp , for bootstrapping ; if you don't know what bootstrapping is , just ignore it
also , put bleeder resistor from output side of C203 (where D is ) to GND , to ensure that cap is always discharged , important not to zap amp when fiddling with interconnection
10 to 100K will do the job
Hahaa, they are the same both front ends
I received a few weeks ago, two PCB's from the store. Wanting to explore this classic circuit better and maybe put a 2SK79 in it as the output stage instead of the 610.
I'd like to echo what Zen Mod has already said, on the BA-1 Front-end board, the pad "+D" is the signal output, and the "out" is for biasing a power amp stage later.
Also the addition of a bleeder on the output capacitor is an extremely good idea.
In a perfect world the K170 would have an Idss of about 8ma, as it's acting as a CCS, but a couple ma in either direction isn't going to hurt anything.
I'd use the 610 in the output to begin with, I recently used 610/9610 in the output of the Whammy and am very pleased with the performance. Get the circuit working with pedestrian parts first and then change things out.
Also the addition of a bleeder on the output capacitor is an extremely good idea.
In a perfect world the K170 would have an Idss of about 8ma, as it's acting as a CCS, but a couple ma in either direction isn't going to hurt anything.
I'd use the 610 in the output to begin with, I recently used 610/9610 in the output of the Whammy and am very pleased with the performance. Get the circuit working with pedestrian parts first and then change things out.
Well that's good, I'm back in...it's all in an envelope labeled BA2....When BA3 came out I never looked back.Hahaa, they are the same both front ends
I received a few weeks ago, two PCB's from the store. Wanting to explore this classic circuit better and maybe put a 2SK79 in it as the output stage instead of the 610.
Russellc
Case secured
Dug the depths of my storage closet and located the first case I ever made. A keen eye will note that I have made a number of things from the same recycled bamboo flooring
Somewhere in my garage is a really nice piece of stainless that I intend to fashion into a faceplate. My only worry with this case is the depth. The trafo ( AS-1220, shielded ) will be pretty close to the input selector switch.
Pictures:
https://1drv.ms/f/s!AtUqSzQhRd9X8xb7ELPZb-Gz9d7n
Dug the depths of my storage closet and located the first case I ever made. A keen eye will note that I have made a number of things from the same recycled bamboo flooring
Somewhere in my garage is a really nice piece of stainless that I intend to fashion into a faceplate. My only worry with this case is the depth. The trafo ( AS-1220, shielded ) will be pretty close to the input selector switch.
Pictures:
https://1drv.ms/f/s!AtUqSzQhRd9X8xb7ELPZb-Gz9d7n
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Dug through my jfets and it seems I'm out of loose K170's. I did find a matched pair K170/J74 that came from the tech-diy store long ago...but I don't know the idss on them. Would be orphaning a pair of J74's to use them.
Also found Fairchild FQP3P20/3N30 and Toshiba J313/K2013 in the parts bin, but no IRF610. I'll have to order some in.
Also found Fairchild FQP3P20/3N30 and Toshiba J313/K2013 in the parts bin, but no IRF610. I'll have to order some in.
The jfets were part of an F5 kit I never built. Did an F4 and BA-3, and also didn't look back...until I built the vfet amp. Now I have an itch to try different preamps. I like how the ba-3 sounds with it, but feel like I have a whole lot of stuff in front of the vfet amp that could be simpler. Already had most of what I needed for the BA1FE on hand, so it seemed a good place to start.
The mosfets in my vfet amp were also from the tech-diy F5 kit
The mosfets in my vfet amp were also from the tech-diy F5 kit