I'm interested in building a BA-3 for a line stage preamp but though I have been reading about it now for several days I just can't track down a BOM , the one on the Store doesn't work for me as it seems to be an update but is missing the main original list and several of the links at the beginning of this thread now get an error message.
So I would be very grateful if someone has the list please.
Also I'm thinking of running it with my Aleph J. Is this a good idea or would it be better with the F4?
Lastly can I use the power supply to run both the Aleph and this BA-3 board or will I need to make a new PSU? If I can use the same PSU maybe I can even fit this in the same box and have an integrated amp, though I think it might be a bit crowded and too hot that way. Instead it would probably be better to take the power out to a separate box and have the Aleph and the BA in together. Does that make sense?
Thanks guys.
So I would be very grateful if someone has the list please.
Also I'm thinking of running it with my Aleph J. Is this a good idea or would it be better with the F4?
Lastly can I use the power supply to run both the Aleph and this BA-3 board or will I need to make a new PSU? If I can use the same PSU maybe I can even fit this in the same box and have an integrated amp, though I think it might be a bit crowded and too hot that way. Instead it would probably be better to take the power out to a separate box and have the Aleph and the BA in together. Does that make sense?
Thanks guys.
Here's a BOM. I thought about building an integrated but decided to build standalone for flexibility to use multiple power amps and easier resale down the road if necessary.
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Thanks Mark, I can see that BOM clearly.
The other one that I downloaded does not show what you can see Greg, probably because it's in xl and mine is open office, though that usually translates quite well.
Yes I've read Nelson's article and understood some of it, particularly about the way the bias works, which illustrates why it's a two steps forward and one step back process at the beginning.
Yes the build guide is very clear as well.
I see what you are saying Mark about flexibility but still wondering if I'm going to need a complete new PSU or whether the one I have can drive both units?
The other one that I downloaded does not show what you can see Greg, probably because it's in xl and mine is open office, though that usually translates quite well.
Yes I've read Nelson's article and understood some of it, particularly about the way the bias works, which illustrates why it's a two steps forward and one step back process at the beginning.
Yes the build guide is very clear as well.
I see what you are saying Mark about flexibility but still wondering if I'm going to need a complete new PSU or whether the one I have can drive both units?
I don't know what your PSU looks like, the BA-3 needs a regulated one at the correct voltage. They are cheap on Ebay.
My PSU is the standard one from the DIY shop, the universal one that will apparently be good for all Pass amps. So I know I could use it to power the BA-3 if it were a separate unit. It runs a dual 18volt per side Antek 400Volt transformer.
What I don't know is whether it can be used to power both the Aleph-J and the BA3 at once, or if I have to make a new power supply for the BA-3?
Please someone must know this.
What I don't know is whether it can be used to power both the Aleph-J and the BA3 at once, or if I have to make a new power supply for the BA-3?
Please someone must know this.
You could also use a regulator to feed just the BA3 board, connected to the main PSU for the DC source -- the load of the preamp stage would present a insignificant load to the power amp's PSU.
The BA-3 gainstage does not need a regulated supply, but it doesn't hurt.
The BA-3 gainstage does not need a regulated supply, but it doesn't hurt.
Thanks Jim, I was hoping that might be the case. Which mosfet do you use to regulate the power? And what amperage should be run there?
Just wondering if I could use the IOM45S ?
Just wondering if I could use the IOM45S ?
Keep in mind you will drop volts in the regulator which will decrease your voltage to the preamp below the pass-specified 24v. If your rails sag to 22v then you drop 3 volts in the reg you will only end up with 19v or so. Which probably effect voltage swing of the preamp. Not a big deal but I wouldn’t go below 18v.
Not familiar with that regulator you mentioned. You need a bipolar supply (+ and -). A good example is a lm317/337 supply which is very common.
Not familiar with that regulator you mentioned. You need a bipolar supply (+ and -). A good example is a lm317/337 supply which is very common.
Well I attempted my first power-up of this amp. PS is putting out 24v + -, P1 and P2 are set to zero ohms as measured between V in and the minus side of C1 and C2. I can't see anything wrong with the build but I'm getting 21v across R10 and R11.
I only left it on for a second and there is no heat or smoke from the mosfets. Any ideas here?
I only left it on for a second and there is no heat or smoke from the mosfets. Any ideas here?
OK looks like the mosfets are reversed. Q4 is N channel and Q3 is P channel correct?
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Thanks, any advice on desoldering? So far I managed to scorch the PCB and destroy the mosfets, but the pins are still in the holes. Back to Mouser...
add solder to all pins from bottom side , heat all 3 pins together , pull them
suck or wick solder from holes later
suck or wick solder from holes later
If you don't have one, make sure you pick up an ESD-safe desoldering pump at Mouser. Sometimes you want the wick, but I find myself using a pump 95% of the time.
Attachments
Now one step closer…...PSUs are ready and now also the BA-3 pre PCB. I noticed that you has the pot screw to the left while I have it to the right. I am quite sure I have mounted the Bourns pots according to schematic with CW and wiper connected to each other. CW is pin 3 (left on picture) on a 3296 (102) Bourns pot. I use Fairchild mosfet so 1k pots. Jfets are a Toshiba quad which I got from the ebay seller with the "funny" name…...
