The BA-3 as preamp build guide

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#681
Hikari1 said:
The answer is yes, you can use them but...

The universal psu board is unregulated. Most people making this preamp are using regulated supplies. Even a simple lm317/337 supply will work. The universal psu is designed for power amps so it has much more capacitance than will be needed here. Also, it has no regulation, which is really what's needed here.

Your transformer will make 28-30v rails which is fine. It would be better to have some regulation so you can drop 3-5 volts. But the transformer is massively big for this application. Really you need a 50-100va transformer.

Your transformer and psu board is really for a power amp, not a preamp. I'd save them for a power amp and buy a 100va transformer and appropriate psu...both of which are pretty inexpensive compared to what you have.

But to answer your question, yes you can use what you have but it's not ideal.
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🙁🙁
If I would use the 300va, knowing it is not the best, would this PSU do the trick?:
Linear Dual Power Supply board MJE15034G Low Noise 5V a 24V 2A - Audiophonics
drpro said:
I chose to use Salas shunt regulators. I felt they offer a very quiet and stable power source. My BA3 build has resulted in no discernible noise heard from the speakers. I have built a pair of F4 amps which I feel showcase whatever pre you are using. Currently my fav though I recently completed a Salas headphone/line pre. Also very nice.
All of this to say your 300va would be fine for a BA3 build.
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Thank you, drpro, I'm going to wait a bit for some more advice. The thing is the toroidal was expensive. I bought it by mistake and no possibility to give it back. And I'm no planning on building more amps for the moment, only need this one preamp.

Cheers,
David.
 
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#683
I cannot read French but this one will work if your transformer has dual secondaries (4 secondary wires). If it is center tapped (3 wires for output) it will not.

Linear Power supply Module Double DC LT1083 24V 5A - Audiophonics

What you need to pay attention to is that the regulator can withstand your max input voltage which for you will be around 30V. So the caps and semiconductors need to be rated for at least 30V. 35V safer. The preamp draws around 200ma for both channels and you want to have a supply that is greater than that so anything above 1A or so is fine. 5A, like the regulator referenced above is overkill and may mean the regulation/noise is not as good as something with less current capability but better specs.

If it was me I would choose a LM317/337 supply. Why? They are cheap, plentiful from many vendors and include some protection(overcurrent, etc.) which might be helpful.

I have used 317/337 and a Jung SuperReg in this preamp. The difference is not huge.
 
#684
Hikari1 said:
I cannot read French but this one will work if your transformer has dual secondaries (4 secondary wires). If it is center tapped (3 wires for output) it will not.

Linear Power supply Module Double DC LT1083 24V 5A - Audiophonics

What you need to pay attention to is that the regulator can withstand your max input voltage which for you will be around 30V. So the caps and semiconductors need to be rated for at least 30V. 35V safer. The preamp draws around 200ma for both channels and you want to have a supply that is greater than that so anything above 1A or so is fine. 5A, like the regulator referenced above is overkill and may mean the regulation/noise is not as good as something with less current capability but better specs.

If it was me I would choose a LM317/337 supply. Why? They are cheap, plentiful from many vendors and include some protection(overcurrent, etc.) which might be helpful.

I have used 317/337 and a Jung SuperReg in this preamp. The difference is not huge.
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Thank you so much for your help Hikari, my toroidal has got 2 outputs, and it is supposed to be rated 20 volts per channel. So, do I really need 30/35v caps? Would the LM317/337 support my 300va toroidal?

Thanks.
David.
 
#685
20v rating is AC. To convert to DC multiply by 1.41 (20x1.41= 28.2V). So you need at least 30V caps. 35V would be safer in case the mains voltage fluctuates or is unstable.

The VA rating of the torroid has nothing to do with voltage but rather current capability. It can provide WAY more current than needed which is not necessarily a bad thing in this application but it is probably 10X more than needed. The downside is it is large and will possibly radiate more efi/emi. And if you use a shunt regulator (which you will probably not) it may create more heat. With this transformer I would stay away from shunt regulators.

LM317/337 has a max input voltage of 40V I think. like I said before the caps need to be appropriate rated as well. The regulator doesn't care about the VA rating of the transformer. It cares about the input voltage and the current draw. The current draw of your preamp will be approx. 200ma. Well under LM317/337's 1.5A rating.

The LM series regulators are not hi-end or state of the art. If you want the best I would Salas' shunt or a Jung SuperReg or some sort of exotic cap multiplier. But 317/337 work well and are easy to use and it's my belief that this circuit doesn't care about regulator performance as much as some others.

Here are some other regulators I would consider although I haven't used any of them:

Kubota low noise regulator full blown version kit !! | eBay

LM317/337 dual rail regulator kit for preamplifier/headphone amp (red) ! | eBay
 
#686
Hikari1 said:
20v rating is AC. To convert to DC multiply by 1.41 (20x1.41= 28.2V). So you need at least 30V caps. 35V would be safer in case the mains voltage fluctuates or is unstable.

The VA rating of the torroid has nothing to do with voltage but rather current capability. It can provide WAY more current than needed which is not necessarily a bad thing in this application but it is probably 10X more than needed. The downside is it is large and will possibly radiate more efi/emi. And if you use a shunt regulator (which you will probably not) it may create more heat. With this transformer I would stay away from shunt regulators.

LM317/337 has a max input voltage of 40V I think. like I said before the caps need to be appropriate rated as well. The regulator doesn't care about the VA rating of the transformer. It cares about the input voltage and the current draw. The current draw of your preamp will be approx. 200ma. Well under LM317/337's 1.5A rating.

The LM series regulators are not hi-end or state of the art. If you want the best I would Salas' shunt or a Jung SuperReg or some sort of exotic cap multiplier. But 317/337 work well and are easy to use and it's my belief that this circuit doesn't care about regulator performance as much as some others.

Here are some other regulators I would consider although I haven't used any of them:

Kubota low noise regulator full blown version kit !! | eBay

LM317/337 dual rail regulator kit for preamplifier/headphone amp (red) ! | eBay
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wow, I'm going to digest all that. I'm sorry I'm really ignorant in terms of electronics, so I ask and ask as much as I can, before taking any step forward. Really appreciated.
 
#687
Yes, ask if you have questions. No problem.

It might be easier to look at it this way:

You want 24V-ish as the target:

Transformer (20V AC = 28V DC) ------>

Regulator (28V minus 3-5V DC = 24V), uses 3-5V for regulation, needs to be rated for at least 28V but output will be 24V-ish. 3-5V loss is dissipated as heat. ------>

BA3 board (will only see 24V at all times).
 
#689
Hikari1 said:
Yes, ask if you have questions. No problem.

It might be easier to look at it this way:

You want 24V-ish as the target:

Transformer (20V AC = 28V DC) ------>

Regulator (28V minus 3-5V DC = 24V), uses 3-5V for regulation, needs to be rated for at least 28V but output will be 24V-ish. 3-5V loss is dissipated as heat. ------>

BA3 board (will only see 24V at all times).
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Really, much appreciated, I will be having a look at it thoroughly.

6L6 said:
The BA-3 amplifier is my favorite amp of all the Firstwatt, I would build that with your transformer and PSU.


😀 😀 😀 😀 😀
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Well, I'm in the middle of an F6 construction, and my marriage is already at risk. I can't just say sorry all the time. Once I will get beaten badly. And I don't want that on your conscience.

😉
 
#693
Silas - The Toshiba are great if you can get them, but I've built one with the Fairchild and find them to be excellent as well.

The Mosfet do not need to be matched. The Jfet do. Use the Jfet pairs from the diyAudio store and things will work wonderfully!
 
#696
BA3 FE is really at its best when mated with BA3 OS , so working in full gain/swing mode

when adjusted to work as line preamp , it's somewhat constipated

so , it's really best to make it as part of power amp , then use anything simple as line stage - even just decent pot or pot plus buffer will work as charm
 
#700
the carriage and import taxes are twice over by buying from the USA.
It should be cheaper to buy direct within the EU.

I think Modushop will make available the same kit of bits as DIYaudio stock.
I don't know what info you need to include in your order to get access to those kits.
 
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