There are several DIYA
Several by Mark Johnson are available in this thread and as kits on the DIYA store.
A design by Aksa called the “Aksa Lender” is also available and was designed specifically to generate 40Vpp with low distortion while using minimal number of discrete components for SE Class A operation.
You can also use balanced line drivers like LME49724 or OPA1637 on +/-15v rails which can drive up to 52Vpp in balanced out mode. DIY boards with these are also available if you look. These will be transparent low distortion so the sonic signature of the F4 will come through.
With regards to your question about using Edcor autoformer. The ones used by many members on amps like M2 etc have 5x voltage gain. So all you need is an input stage capable of driving 8Vpp into a 600ohm load. The Bulwark on DIYA store can do this I believe.
There are several DIYA open design high swinging preamplifiers capable of 40Vpp needed to deliver 25w into 8ohms.
Several by Mark Johnson are available in this thread and as kits on the DIYA store.
A design by Aksa called the “Aksa Lender” is also available and was designed specifically to generate 40Vpp with low distortion while using minimal number of discrete components for SE Class A operation.
You can also use balanced line drivers like LME49724 or OPA1637 on +/-15v rails which can drive up to 52Vpp in balanced out mode. DIY boards with these are also available if you look. These will be transparent low distortion so the sonic signature of the F4 will come through.
With regards to your question about using Edcor autoformer. The ones used by many members on amps like M2 etc have 5x voltage gain. So all you need is an input stage capable of driving 8Vpp into a 600ohm load. The Bulwark on DIYA store can do this I believe.
Last edited:
Thanks, but that still doesn't answer what I would like to do... I would like to take an SE output and create a balanced output with voltage gain... meaning, for example, given a 1:5 voltage amplification on the transformer, if I have 2 Vpp on the input, I'd like to see +/- 10 Vpp on the balanced output. I would guess the input would be wired to one input (+) and center tap and the output would be wired to (+), (-) and center tap.
I think that I explained that in PM
with 600:15K Edcor, which is 1:5 voltage wise, wired as SE in, Bal out - you get 2V in, 10V out
be it Vpp or Vrms
and it is straight Vin, Vout ......... no need to write one without and other with "+/-"; if you use that without need or proper implementation, you're just confusing sissybrains, as mine certainly is
so, in short :
SE/Bal (so pure xformer connection/arrangement), you have 2V in, 10V out; simple as that
with 600:15K Edcor, which is 1:5 voltage wise, wired as SE in, Bal out - you get 2V in, 10V out
be it Vpp or Vrms
and it is straight Vin, Vout ......... no need to write one without and other with "+/-"; if you use that without need or proper implementation, you're just confusing sissybrains, as mine certainly is
so, in short :
SE/Bal (so pure xformer connection/arrangement), you have 2V in, 10V out; simple as that
I think if you look at the Scourge input stage, you will see that it takes SE input and makes balanced output with gain using the transformer. Note that the Edcor takes a lot of current to drive and hence, 4 actives are needed to do this. You can’t just connect the transformer to the SE signal from the source (at least not without risk of highly distorting your input signal).
ZM
... OK, I get it now. When I read the PM I was looking more into the autoformer wiring. Thanks.
Continuing my wanderings through the DIY ampliverse I've decided I'm going to build an F4. I notice that the Panasonic ERX-3FJR47 source resistors are obsolete and out of stock. I don't really want to shell out many many quids for Mills 5W. DIY is getting expensive...! Other MOX's generally have a high tempco, doesn't feel good... but I had a thought... why not use a couple of 2W thick film SMD current sense resistors like Vishay-Dale RCWE2512R910FKEA in parallel? I could solder the pair side by side on some leads 🏁 washing line syle, hopefully they wont toast. Good tempco, good price, low inductance and good tolerance. Good idea? Bad idea?
Brief OT aside: I recently picked up an old S100 at a good price. I wouldn’t be surprised if its the only example in the UK.
