BA-3 Amplifier illustrated build guide

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#265
BA 3 pre amp for F6

Just finished the F6 build with guidance from both SLS6 and Patrick; works and sounds great. Now am interested in building a pre amp for it- seems like the BA3 might be the way to go?

I recall the F6 has a "preference" for a certain range of output impedance and voltage in order to match well and drive it to the right output levels.

Any suggestions on if the BA3 is a good match and in what configuration is appreciated.

thanks
 
#266
F6 is agnostic to the preamp driving it, it works very nicely with all I’ve tried. :yes: BA-3 will work beautifully, as will Wayne’s BA2018 linestage.

F4 (which has no gain) is the one requiring a special preamp.
 
#267
Hi everybody,

Is the output power of the amp the same with 24Vdc power supply and 0.7A per device or with 32Vdc psu and 0.52A. In both case there is 100W on the dissipator per channel ?

What is the psu limit of the devices ?

Thanks

Damien
 
#268
Output power is ultimately limited by rail voltage, so higher voltage will give more power.

However, the voltage limit on this circuit is the input Jfets, and they are technically rated at 25V, though Papa says you can go a little higher... so increase voltage at your own risk. My example has 31V rails and Toshiba Jfets and I have not had any issues.
 
#270
6L6 said:
Output power is ultimately limited by rail voltage, so higher voltage will give more power.

However, the voltage limit on this circuit is the input Jfets, and they are technically rated at 25V, though Papa says you can go a little higher... so increase voltage at your own risk. My example has 31V rails and Toshiba Jfets and I have not had any issues.
Click to expand...

I built mine exactly as you did, and outlined in the build guide. I've had no problems. I used Toshiba Jfets. Nelson has commented that they break down around 40 volts, mine is 31 volts or so. I have no idea if the LS versions are as tough? Who knows maybe tougher?

Russellc
 
#272
Abx74 said:
Toshibas Jfets in mine too.
I Asked because I got two 300VA 2x18V transformer, or one 500VA 2x25V transformer and with this one I got 33.5Vdc... I think It's a bit high...
Click to expand...

I used a 1000VA 24/24 volt Sumr transformer. I think my rails were 31 or 32ish. I have spares if they roast.

If really worried, you could cascode them. I intended to do this with the parts recommended for Turbo F5.
Never saw the need.

Russellc
 
Last edited:
#273
Another BA3 is born!

Initially started with 0A5 bias with 6 devices per channel. More fun to come.

As always, a heartfelt thank you to Papa, 6L6, ZM and the countless others that have made this possible!

61041312320__DA77483D-F235-48FF-9A62-D0DAF7F306C4.jpg

61041316641__6620A342-F241-4575-A1AD-C4E1B7CCA886.jpg

61041320753__0929AA99-544C-4276-A61F-01D80197CB2A.jpg

I'm still not thrilled with the wire routing. I have a few tidbits to tend to, but it's alive - dead quiet and making music.

#protip - make sure to ground the front end. Ask me how I know... :rofl:
 
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