PP triodes, like most devices vacuum or otherwise, get higher and higher efficiency the higher the load impedance. Usually less THD too, and of course improved damping due to the ratio of load Z to Rp. There is just less IR drop when you hit the knee, and you can operate in a place where the composite gm is pretty darn constant. Works the same for pentodes too, but eventually g2 currents get ridiculous. It’s just a question of where you cry uncle.
If you live in an apartment, what do you do about machining the chassis? That makes more noise than any 10 watt amp, not to mention the MESS. When I lived in a rental house 20 years ago I literally boarded up one entire room for electronics (including plywood over the carpet) but there were still limits on what can be done. I can certainly relate about not being able to crank it up - back in the trailer park I could run power tools till 11 at night and no one cared (because everybody did). But turn up music, and it would bring the cops. Even with a chainsaw running next door.
If you live in an apartment, what do you do about machining the chassis? That makes more noise than any 10 watt amp, not to mention the MESS. When I lived in a rental house 20 years ago I literally boarded up one entire room for electronics (including plywood over the carpet) but there were still limits on what can be done. I can certainly relate about not being able to crank it up - back in the trailer park I could run power tools till 11 at night and no one cared (because everybody did). But turn up music, and it would bring the cops. Even with a chainsaw running next door.
I'm getting ready! Gonna start collecting parts for that garter bias circuit I saw above. These new Mullards are from the same production case lot, since the consensus is that DC/AC balance is the most critical thing to control.
Also get a load of this monster, all-toroid commercial amp for the billionaire audiophile market, I heard this stand up tower amp at Axpona a couple years ago paired with the big Focals. I believe this amp uses solid state phase splitters to more precisely control the balance.
Valve Amps: Output transformers
How much did those Mullards sting you for ? Considering that they are effectively low voltage EL84's which tend to cost a packet - it would be interesting to see the difference. I got a quad of Telefunkens for €25.00, when a single Telefunken NOS EL84 were fetching 4x that.
They were $12.95 each, but the shipping killed me I regret not getting 10 considering the shipping would have been about the same as 6. But don't want to be a hoarder, these should last me nearly the rest of my life!
The loudest sound I make is cutting the hole for the IEC socket with a dremel. Second loudest is the impact driver with the chassis punch. Both make less noise in the hallway than a hammer drill in the concrete wall. This building is very well soundproofed.
They were talking about a single core transformer with 4 windings. I know it works with two cores - I have 5 amplifiers in the room that all use them
and my Hammond set (278CX, 193Q, 167V12, 1650Nx2) is under the bed collecting dust.
I'm using EL86 with 2k2:6R or 3k:8R (VPT12) with 320V B+ and 40mA. Cathode biased with TL783 || 1000uF. The sound is excellent and the power is higher than I expected.
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They were talking about a single core transformer with 4 windings. I know it works with two cores - I have 5 amplifiers in the room that all use them
and my Hammond set (278CX, 193Q, 167V12, 1650Nx2) is under the bed collecting dust.
Either way is a “480 volt winding” which has more inductance than a 240 volt. The two core solution *is* a kluge, but obviously works as long as unit to unit is identical. An 800 to 900 volt winding would have even more inductance, but getting the low impedance winding you want would be more problematic. There really isn’t a solution for 50 to 100 watt amps starting from that end. You either go big or go home starting with an 8T800.
Anyone ever try stacking *four* toroids instead of just two or did that actually arc over between turns and fry four transformers?
Good point!
My top to date is 400V with an 807, maybe I'll do 500V some day but no more, there is plenty of satisfaction and projects in the hobby under 500V to last a lifetime. At 1000V ranges you can get shocked without direct contact.
Re: metal work in the apartment...
If I'm really going to make a racket I have to take the work out to the balcony in the early afternoon when nobody is sleeping and the association's workers are out working on the grounds. Of course if it's raining out then I'm screwed. I try to minimize the drilling and cutting. I like to use things that mount in *round* holes so I can use chassis punches instead of cutting holes with power tools. Drilling holes for nuts and bolts isn't too bad....
If I'm really going to make a racket I have to take the work out to the balcony in the early afternoon when nobody is sleeping and the association's workers are out working on the grounds. Of course if it's raining out then I'm screwed. I try to minimize the drilling and cutting. I like to use things that mount in *round* holes so I can use chassis punches instead of cutting holes with power tools. Drilling holes for nuts and bolts isn't too bad....
Rp for an EL86 triode is 665 ohms if you run them with low plate voltage and high plate current. Rp goes up a bit if you lower the Ip. I was figuring rp of ca. 800 ohms. 3200 ohms p-p would mean each triode sees a 1600 ohm load, which would give you that 2:1 ratio for most power out. But like I mentioned earlier, I'd be looking for lower THD and higher damping. 2500/800 = ca. 3/1, which doesn't seem extreme to me.