SV811-3

[simon]

Just checked, the filaments are only 6.3V but 4A! That's probably a 75VA trafo. Don't think I've got anything suitable in 9V you could try to see if you can hear any difference. Will have a look though just in case.

Cheers Simon.

Well, I do have two 9V 75VA transformers. I'm not sure if they're split bobbin as Rod would recommend but you're welcome to try them to see if you can hear any difference to the toroid.

[simon]

Just to say that a common primary for the filament transformer isn't regarded as ideal, I think its fair to say that Rod would recommend separate trafos for each channel. But it's what ya got and iron isn't cheap. Just thought I'd mention it.

Does he say why he recommends that? Interested what the reason is.

I think he's discussed it more than once on what started out as Guido Tent's thread in around 2004 on DIYAudio. Googling hasn't found it, I could guess but I'm wary that my memory isn't good at the moment and it's best I don't speculate I think.

[ejam]

Regarding the schematic of the Aikido driver stage on Page 1, you also missed the grid connection of the lower 12AU7/ECC82 to the voltage divider network.

[Cressy Snr]

Regarding the schematic of the Aikido driver stage on Page 1, you also missed the grid connection of the lower 12AU7/ECC82 to the voltage divider network.

Thanks ejam,
I always make mistakes on schematics. I need a proof reader, but I don't think my wife would fancy taking on that job.

Corrected (I hope there isn't anything else) schematic:

Corrected Aikido.png (62.61 KiB) Viewed 1360 times

[Cressy Snr]

Of course there's always this option with other valves from my stash:

Option_2.png (52.31 KiB) Viewed 1357 times

[Cressy Snr]

Well, I do have two 9V 75VA transformers. I'm not sure if they're split bobbin as Rod would recommend but you're welcome to try them to see if you can hear any difference to the toroid.

I'll have a think about that Simon.
I may attempt to get it going with the SMPS supplies, then I can sub in a the linear filament supply similar to how Stephen (Izzy) progressed with his GM70pp I've ordered the bits for the linear heater supply anyway, so my options are open.

For now, I'm going to concentrate on a cabinet and how best to split it into modules that can be tested, made sure of, then assembled into the final product.

[simon]

That makes sense

[ejam]

Cressy Snr

Speaking of Aikido, built this years ago and it sounded really good. Forgotten who the designer was, one from the UK I believe. Anyway if your in the mood.....

[Cressy Snr]

Cressy Snr

Speaking of Aikido, built this years ago and it sounded really good. Forgotten who the designer was, one from the UK I believe...

Dave Dove I believe it was.

[IslandPink]

Looks like a James D circuit diagram that Dave built. I believe that one came round to my house. Dave managed to electrocute himself ( slightly ) on the way through the door, from a stray capacitor hanging off one side.

[simon]

It's definitely James' drawing. I can't remember in the depths of time now how much of the pentode Aikido was James' idea and how much was Dave's. I remember musing on an Aikido cathode follower to drive a 300B and James liking the idea, but it must be 16 or 17 years ago now.

[Cressy Snr]

Been doing a little bit of work in PSUD, designing a raw DC supply for the Coleman regs. I had a look at Ale Moglia's Bartola Valves site and got a little bit of useful inspiration there. The result of that and a bit of thinking on my part, using the parts I have is the hybrid choke input 4A supply below. Two of these will supply 12V each to the Coleman regs.

I have a 200VA/20V twin secondary frame transformer with 100VA per output, so modelled that with a Hammond 159ZJ 10mH 5A choke plus two 22000uF caps. Below is what I came up with:

Startup and output

Sv811-3FilSupplyDCbeforeRegs.png (143 KiB) Viewed 1047 times

Ripple on output. About 40mV pk-pk

SV811-3DCSupplyDCRVbeforeRegs.png (145.18 KiB) Viewed 1047 times

Ripple current after choke. I don't think 1A...ish, RMS is bad at all

Sv811-3DCFilSupplyDCRIAftertChoke.png (162.2 KiB) Viewed 1047 times

[Nick]

1. Whats the max voltage the regulator can accept without damage? I would worry about that with something that has choke input aspects
2. Why are you beating yourself up with the supply for a regulator? isn't that why you are using a regulator?
3. Whats wrong with a 9v 80va toroid, 25A bridge and 10mF of caps? Or a 9+9 160va toroid to do both channels.

[Cressy Snr]

1. Whats the max voltage the regulator can accept without damage? I would worry about that with something that has choke input aspects
2. Why are you beating yourself up with the supply for a regulator? isn't that why you are using a regulator?
3. Whats wrong with a 9v 80va toroid, 25A bridge and 10mF of caps? Or a 9+9 160va toroid to do both channels.

The answer to those questions Nick is that I haven’t the foggiest idea what’s required for “good enough” performance and what is overkill. Never have had, so thanks for suggestion no3

[izzy wizzy]

My take on this when coming up against the same thing was copy Rod's design. For the first time, didn't model it in psud. Even went for the same rated traffo just bit more volts coz feeding the lehane dht regs. Wouldn't have a clue what the ripple is in.