The Nemesis 813 PP Amplifier

[pre65]

Ah yes, but it will be the best amp in the world.

Just don't tell DTB or our Andrew I.

[izzy wizzy]

A 12V 20A SMPS arrived today. It has adjustable voltazge which is a bonus. I'm betting there will be a load of hash on the output. Any tips on dealing with that at 10A?

Cheers,
Stephen

[IslandPink]

My experience so far is that there's not a lot of hash and it's more or less at 50 to 60kHz with some higher. I think I remember 40mV as a number from one I used. Just try a 'cough big resistor first and see how it goes.

[izzy wizzy]

My experience so far is that there's not a lot of hash and it's more or less at 50 to 60kHz with some higher. I think I remember 40mV as a number from one I used. Just try a 'cough big resistor first and see how it goes.

Well I could just turn the voltage down a bit. Why just a big resistor?

But as you say, I'll just be trying it first anyway. I'm hoping the V adjust will get me to 10v without a resistor. Thinner wiring can do it at these currents

Cheers,
Stephen

[Mike H]

Ah, "the best amplifier in the world"! Forgot about that.

I use a 30A 12v SMPS for each 833a, Chinese off Ebay. (filament 10v @ 10A)

I drop it down to 10v with two resistors and two caps.

For the next iteration I may use two Rod Coleman 10v @ 5A supplies in tandem.

Be warned, I had to have massive heatsinks for the Coleman regs on my 801A/300B SET amp, and that for only 1.2 Amps. Still too hot to touch. Stupid amounts of heat.

[Mike H]

A 12V 20A SMPS arrived today. It has adjustable voltazge which is a bonus. I'm betting there will be a load of hash on the output. Any tips on dealing with that at 10A?

Cheers,
Stephen

Have I mentioned common mode rejection chokes? Or did I just imagine it?

[IslandPink]

Well I could just turn the voltage down a bit. Why just a big resistor?

D'Oh sorry, you did say. Rushed out a comment there without engaging brain properly.

[Mike H]

Quick google - two sources of common mode chokes for 10 Amps - Mouser and Farnell:

https://www.mouser.co.uk/Passive-Compon ... xiZ1z0wqau

https://uk.farnell.com/c/passive-compon ... urrent=10a


HTH

[Mike H]

In case anyone isn't sure what a common/differential choke filter looks like:

common-mode.jpg (23.71 KiB) Viewed 4421 times

HTH

[ed]

shameless commercial intrusion here...

but if anybody is interested in the heavy duty version of the Coleman regs, complete with sinks then look no further...

as seen here

this chassis I beleive is now in the capable hands of Steve C, the heater regs are nearly the last of the components to be disposed of. Maybe £15 each ono.

[pre65]

Hi Ed, what voltage/current are the regs for ?

I could be interested.

[pre65]

Re the SMPS voltage adjuster, I've not needed to adjust mine but I was of the opinion that the adjustment range was small.

Have you a dummy load to play with ?

[ed]

Hi Ed, what voltage/current are the regs for ?

I could be interested.

http://www.vitalstates.org/diy/misc/AN_DHT_TX_V4.pdf

these units were running 6.3v heaters at 4 amps but as you can see are very versatile re config change. They were supplied by 2 x 12v 12A smps.

[Mike H]

That is a SERIOUS heatsink.

[izzy wizzy]

Got the SMPS. Good news is it can be adjusted to 10V. Bad news it won't start up both the fils when cold. It can start one so I think I'll have a delay relay for the 2nd which is a bit irritating. At least the SMPS will be up to power the delay circuit. Unless anyone has some better ideas?

Cheers,
Stephen