audio-talk

jack wrote: ↑Fri Nov 22, 2019 9:53 pm Interesting. My understanding of NFB is that it relies on a constant180° phase shift, so if the DUT is not phase linear across the working bandwidth (which pretty much no power amp is), distortion will be introduced....

Phase linear amps are very specialised and expensive...

Morgan agreed when I had a good chat about power supplys contaminating the signal through multiple valves connected to it.
we also agreed feed back was similar in effect.. It cancels or alters the original signal.. But by how much is amplifier dependant...So it's not a guide to how good an amp sounds.?

Just thought, the talk of 180 is maybe confusing matters. For feedback to be useful, there needs to be effectively 0 deg phase shift between the input and output in the range of frequencies of interest, the feedback is then compared to the input. Its the act of comparison that gives the illusion of 180 deg being involved. What it actually is is a - sign.

Cressy Snr wrote: ↑Fri Nov 22, 2019 10:35 pm I’ve done a lot more work on the OTL, than I’ve documented in this thread, and a year is the longest I’ve kept my attention on a project.

Hi Steve when you come to rework your 13E1 amp would you be interested in the PCBs I was going to use for mine before I switched back to using 6SN7s? I need to declutter.

I thought they might be interesting to you because they include my (untested, but as per the schematic) clone of the K&K Audio constant current sink - the rest is as per schematics IIRC. The two halves of the input/driver valves can be powered seperately by just removing a wire link so they'll work well with your multi-stage power supply arrangements. If you want the Mundorfs we can work something out otherwise, I'll whip them off and you can have the boards for the cost of the postage?



No problem if they're not of interest - just thought I would ask before recyling them.

Ray

Ray, are those boards 2oz or 1oz?

I only ask as the 13E1 heaters are 5.2A at 6.3V, so for a 1oz board that'd be a minimum of about a 8mm or 310mil trace and half that for 2oz...

It's a lot of current for a PCB... Wire jumpers?

I only ask as the 13E1 heaters are 5.2A at 6.3V

I don't think the output valve heater circuit is on that PCB just the driver stage.

Nick wrote: ↑Sun Jan 12, 2020 9:20 pm

I only ask as the 13E1 heaters are 5.2A at 6.3V

I don't think the output valve heater circuit is on that PCB just the driver stage.

Ah!

Nick is correct Jack, the 13E1 sockets are 'off-board' - the PCBs have the input/driver stages precedng the 13E1 but then also have the output caps and current sinks 'after' the 13E1.

Anyway, 13E1 filaments are 26V @ 1.3A or 13V @ 2.6A. You may be thinking of 6C33Cs, which are 12.6V @ 3A or 6.3V @ 6A?

Ray P wrote: ↑Sun Jan 12, 2020 8:45 pm

Cressy Snr wrote: ↑Fri Nov 22, 2019 10:35 pm I’ve done a lot more work on the OTL, than I’ve documented in this thread, and a year is the longest I’ve kept my attention on a project.

Hi Steve when you come to rework your 13E1 amp would you be interested in the PCBs I was going to use for mine before I switched back to using 6SN7s? I need to declutter.

I thought they might be interesting to you because they include my (untested, but as per the schematic) clone of the K&K Audio constant current sink - the rest is as per schematics IIRC. The two halves of the input/driver valves can be powered seperately by just removing a wire link so they'll work well with your multi-stage power supply arrangements. If you want the Mundorfs we can work something out otherwise, I'll whip them off and you can have the boards for the cost the postage?

No problem if they're not of interest - just thought I would ask before recyling them.

Ray

Hi Ray, You’ve already sent me two of the boards with the K&K CCS clone incorporated, but thanks for the offer.

Ah, forgot that Steve.

These ones are populated (sans Mundorfs). Anyway, I'll see if any one else is interested otherwise they'll go into the box for the recycling centre.

Hi Ray
Is there a link to the circuit anywhere?
They might be just what I need for something I am working on
Cheers
Max

Max N wrote: ↑Mon Jan 13, 2020 8:06 am Hi Ray
Is there a link to the circuit anywhere?
They might be just what I need for something I am working on
Cheers
Max

Hi Max, below is Steve's schematic that I used for setting out the PCB;
Apart from the anode resistors for the 6H30pi halves it doesn't include any power supply parts (my PS was different, lifted straight from my Transcendent 300B SE-OTL) and has the K&K current sink instead of the TL783 (though you could use that if you wanted). Obviously the Septal socket parts are off-board. The tube socket is a teflon type, soldered to the PCB - I designed it as the means of mounting the board and clamping the socket to the chassis top plate. I must emphasise that I've never used/tested the boards, though Steve has been using an earlier version (sans K&K current sink) in his build that this thread is about.

Ray

Thanks Ray, I’m just trying to figure out if I could adapt them a bit.....

Hi Ray
The circuit I want to try is too different so I’ll pass, but thanks for the offer. Hopefully someone else can use them. They’re nice boards. Would be a shame to recycle them.

No problem Max.