Brett
> your pre and a nice little PP 2A3. Then later, once you're confident with what you're doing, especially with regards to high voltage, add a 3rd stage to the poweramp being PP 845/ 211/ 813T/ GM70.
> An extra PS would be needed for the output stage, but it's actually easier to build it this way rather than trying to find a single PT that will provide your (say) 300V for the drivers and 1000V for the outputs.
> You could even have both built into the one chassis with the 2A3's OPT being used as anode loads for the 2A3's, then cap coupled to the output stages. When you don't need all the extra juice, don't power up the big tubes and connect your speakers to the 2A3 outputs.
> It does then mean you have to connect your speaker cables via a plug and socket arrangement for convenience, and we all know how anal retentive 'philes can get about them......
That’s a series of really great ideas, except I’d thought of driving the transmitter tube amp (like Cary and others) with something with more grunt eg a 300B.
> trioded EL84s are excellent and will make great drivers for the bigger tubes.
Probably a better idea for the down the track transmitter tube amp.
> I'd go for the Ralph Power/ Stigla 2A3 design (maybe with a CCS in the 2A3 tail) or the Lynn Olson Petit Amity.
* I think that may be best for right now. Will check these out.
** Thoughts which of these would have more punch ?
> Mind you ANY amp, properly built with transmitter type tubes will be big, heavy and expensive. And probably have low WAF.
I’ll start looking out for cost savings ideas, and checking out good chassis design.
Mr tubelab
Thanks for the explanation about the problems with bigger amps.
Thanks again guys
> your pre and a nice little PP 2A3. Then later, once you're confident with what you're doing, especially with regards to high voltage, add a 3rd stage to the poweramp being PP 845/ 211/ 813T/ GM70.
> An extra PS would be needed for the output stage, but it's actually easier to build it this way rather than trying to find a single PT that will provide your (say) 300V for the drivers and 1000V for the outputs.
> You could even have both built into the one chassis with the 2A3's OPT being used as anode loads for the 2A3's, then cap coupled to the output stages. When you don't need all the extra juice, don't power up the big tubes and connect your speakers to the 2A3 outputs.
> It does then mean you have to connect your speaker cables via a plug and socket arrangement for convenience, and we all know how anal retentive 'philes can get about them......
That’s a series of really great ideas, except I’d thought of driving the transmitter tube amp (like Cary and others) with something with more grunt eg a 300B.
> trioded EL84s are excellent and will make great drivers for the bigger tubes.
Probably a better idea for the down the track transmitter tube amp.
> I'd go for the Ralph Power/ Stigla 2A3 design (maybe with a CCS in the 2A3 tail) or the Lynn Olson Petit Amity.
* I think that may be best for right now. Will check these out.
** Thoughts which of these would have more punch ?
> Mind you ANY amp, properly built with transmitter type tubes will be big, heavy and expensive. And probably have low WAF.
I’ll start looking out for cost savings ideas, and checking out good chassis design.
Mr tubelab
Thanks for the explanation about the problems with bigger amps.
Thanks again guys
A gm70 amp would be much more costly then a 300b SE/PP simply because of the iron requirements. Big OPTs arnt cheap. I had planned to have Jack of Electra-print wind me 60w OPT. Bigger wattage amps are simply more expensive even if the part count is the same. Simple try and locate 100uF 1000VDC+ rated caps then you will understand. Also another consideration is safety, you have to work alot slower and take no chances when working with higher voltage which why it prolly isnt a good amp to be your first project. BTW using all electra-print iron and front panel express for chassis i had priced the gm70 project out at about $3,000 USD. You can prolly build it for much cheaper but i never understood the point of wasting your time with cheaper parts. Cheap tubes can be replaced down the road, cheap iron is with you for life 
Oops, dont know if anyone answered this already because its 7am You really cant wire OPTs in parallel, any difference in voltage between the two windings will produce large amounts of currents between the windings. Similar to power trannies, only trannies that had the windings wired at the same time can be connected in parallel because you know they will have the same voltage. One solution ive seen to getting around the large OPT requirement is to go with parafeed, using large chokes and OPTs designed for pushpull.
You really cant wire OPTs in parallel, any difference in voltage between the two windings will produce large amounts of currents between the windings. Similar to power trannies, only trannies that had the windings wired at the same time can be connected in parallel because you know they will have the same voltage. One solution ive seen to getting around the large OPT requirement is to go with parafeed, using large chokes and OPTs designed for pushpull.
It's just not required. Cary do it because an 805 can best be driven in A2, but none of the TT's I mentioned need to be to give excellent sound or power output. A2 just makes added complications that I don't see will bring any real benefit, whereas with Tubelab's 833 amp, it needs to be driven into A2. If you want to go down the 300B as driver path, then build it as a 2A3 and substitute in the 300B's at lower levels and plate dissipation to get long life out of them. You definitely do not need the power of a 300B to drive any of the TT's mentioned to full power.rick57 said:
Best results I got with the 813T was a single penode 12HG7 as a driver (ie 1 per phase).
Easier to do, but I think the 2A3's would be better still. This was just a cheaper option
I have no idea what "punch" means to you. The Amity was an extraordinarily good sounding amp. I just don't like 300B's.
I'd suggest building it vertically as a couple of small towers with the amp at the top and the PSU below (encased within the tower). Easier to do than a horizontal setup in lots of ways, keeps the HV wiring enclosed and simply makes the bottles themselves the main aesthetic feature. Veneer/stain the cabinet to match the rest of your furniture and maybe even sit them beside the speaks as monoblocks.
Brett
Further interesting ideas.
I’m leaning towards maybe the Power 2A3, ‘Petit Amity’ or a modified 300 SE (‘Lady Day”). Will take a while to decide.
I like the idea of small towers, I wonder if the wife will?
> the same pair of output trannies in everything from paralleled EL84 . . . to 813T/GM70.
Does that mean they were overkill for the EL84s?
Further interesting ideas.
I’m leaning towards maybe the Power 2A3, ‘Petit Amity’ or a modified 300 SE (‘Lady Day”). Will take a while to decide.
I like the idea of small towers, I wonder if the wife will?
> the same pair of output trannies in everything from paralleled EL84 . . . to 813T/GM70.
Does that mean they were overkill for the EL84s?
On topic for a moment
The Wavac HE-833 at around $40,000 pr. would have to rate a mention here. Pretty drool-worthy sonically too, by the sounds of it.
I have this fantasy of building an 833 based amp to drive a pair of Apogee ribbon speakers. But the consequence of making a mistake during testing the thing would, well, be my last. The cost of the Wavac doesn't seem that outrageous next to that thought.
The Wavac HE-833 at around $40,000 pr. would have to rate a mention here. Pretty drool-worthy sonically too, by the sounds of it.
I have this fantasy of building an 833 based amp to drive a pair of Apogee ribbon speakers. But the consequence of making a mistake during testing the thing would, well, be my last. The cost of the Wavac doesn't seem that outrageous next to that thought.
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