I have a wild idea for a next grand opus project, and it will be 2 part.
I have a large stash of 6c33c tubes I want to put to good use. I was thinking choke loaded SE, maybe 3 or 4 tubes for an output. I haven't thought much about input/driver yet, but I like long tail pairs and with cathode followers. To make this doable, a dedicated set of speakers.
This may need to go in the speaker forum, but it is relevant here. I'm thinking of a BIG line array. Something like 12-20 speakers, but for the sake of tubes, wired in series.
What I'm hoping to gain with this is 100-160 ohm, then with 4 parallel triodes, each seeing 400 ohm load. Not too far out of what the tube likes. I should be able to squeeze out 60-80 watts with a lot of headroom, and without the iron.
Am I crazy? Don't answer that. Can anyone else see the merit in such a setup? I could always scrap out the amp and rewire the speakers to SS impeadance if it's a big fail.
And this is more realistic that my other idea of taking the trannies out of my Martin Logan Monoliths and driving with a pair of 833A OTL.
I have a large stash of 6c33c tubes I want to put to good use. I was thinking choke loaded SE, maybe 3 or 4 tubes for an output. I haven't thought much about input/driver yet, but I like long tail pairs and with cathode followers. To make this doable, a dedicated set of speakers.
This may need to go in the speaker forum, but it is relevant here. I'm thinking of a BIG line array. Something like 12-20 speakers, but for the sake of tubes, wired in series.
What I'm hoping to gain with this is 100-160 ohm, then with 4 parallel triodes, each seeing 400 ohm load. Not too far out of what the tube likes. I should be able to squeeze out 60-80 watts with a lot of headroom, and without the iron.
Am I crazy? Don't answer that. Can anyone else see the merit in such a setup? I could always scrap out the amp and rewire the speakers to SS impeadance if it's a big fail.
And this is more realistic that my other idea of taking the trannies out of my Martin Logan Monoliths and driving with a pair of 833A OTL.
With OTL I think I can use a little global negative feedback to reduce the THD a little. I wonder how accurate the published curves are. I'll play around a little with possible load lines looking for the sweet spot of best linearity.
I wonder if it would be worth the effort to make an arduino curve tracer...
I wonder if it would be worth the effort to make an arduino curve tracer...
Yes, I've searched. I've seen OTL's and circlotrons and all sorts of malaise to try to get the damping factor or output impeadance to a usable level, or using an output tranny, but not tailoring the speaker to better match the amp.
I haven't looked at line arrays. No there's nothing earth shattering brilliant about wiring them in series... other than maybe my idea of making them more friendly to an OTL tube amp.
And No, I haven't found anyone do quite what I'm thinking other that the guy who did the amp with 4 833A's per channel to drive an electrostatic panel 10 yrs ago or so. Yea, I posted in that thread way back then.
I'll search for tubetvr stuff an get a look. I usually am not a fan of the compromises needed to drive a 8 ohm load without a OPT.
I'll also check out Tim Mellow OTL, but I am all about "extravaganza". I go big or stay home. Check this past experiment... DIYHiFi.org • View topic - Mother of all tube amps...833 SET
I haven't looked at line arrays. No there's nothing earth shattering brilliant about wiring them in series... other than maybe my idea of making them more friendly to an OTL tube amp.
And No, I haven't found anyone do quite what I'm thinking other that the guy who did the amp with 4 833A's per channel to drive an electrostatic panel 10 yrs ago or so. Yea, I posted in that thread way back then.
I'll search for tubetvr stuff an get a look. I usually am not a fan of the compromises needed to drive a 8 ohm load without a OPT.
I'll also check out Tim Mellow OTL, but I am all about "extravaganza". I go big or stay home. Check this past experiment... DIYHiFi.org • View topic - Mother of all tube amps...833 SET
Hi Brian,
I suggest you obtain a copy of the book 'Audio Reality' by Bruce Rozenblit. It is long out of print but you can download a copy from his website for 20 bucks. It has a full explanation of his OTL patient using 6C33 tubes. His 80 watt T8 Amplifier is based on the patient and uses 6KG6/40KG6 tubes. Lots of other good info and projects in the book too.
I suggest you obtain a copy of the book 'Audio Reality' by Bruce Rozenblit. It is long out of print but you can download a copy from his website for 20 bucks. It has a full explanation of his OTL patient using 6C33 tubes. His 80 watt T8 Amplifier is based on the patient and uses 6KG6/40KG6 tubes. Lots of other good info and projects in the book too.
It would be good to flush out what you mean by "compromise". I have a feeling some of us would interpret "compromise" as "religion", so it would be best to declare up front what design considerations must be met and avoid wasting the time of some partitipants. Based on your original post I am guessing it must be SET without high NFB?
Yes, I'd be interested to know what compromises you are referring to. 25W at low distortion, and output impedance of a fraction of an ohm, is completely straightforward with a pair of 6C33Cs in the output stage. And if you wanted higher power, it roughly-speaking scales as the square of the number of output tubes.
Just 3 ? Why go chicken, THIS!
))
Here is someone's practical experience on arrays of inexpensive drivers, does not come out of my mind, you might like it:
Open Baffle Line Array Speakers
Ah Leadbelly. Great point. Yes, this is more likely religion.
I'm a follower of Pass. I'm a big believer in local feedback of cathode/emitter/source followers. His modulating the current source in the output stage to double efficiency of a pure class A source follower is gloriously brilliant.
I like Brodski's (possible misspelling) Aikio circuit injecting power supply noise into the current source to null it at the output.
I don't like overpriced boutique parts. If something (like an electrolytic cap) is inherently sonically bad, a more expensive one may be a little better, but you quickly run into diminishing returns. Another reason to avoid iron in the signal path where possible. I believe with good implementation and typologies, and running components in their sweet spot, $600 tubes that have had magic schmoo smeared on them, then baked in a oven, then frozen in liquid nitrogen is a waste of money when a $7 tube out of a TV vertical amp will do. No, I'm not a fan of "tweaks".
I do like the Techniques modified Futterman circuit. Tubetvr uses. Haven't yet studied the Mellow circuit.
I like simple circuits I can wrap my head around. Complicated ones that have too many variables have entirely too many ways to go wrong. So I limit myself to 3 pin active devices (not counting heaters and shields).
Unfortunately, with tubes, we don't have positronic based complementary units, so without a transformer to mirror things, we're limited to quasi-complementary typologies for push pull. I was considering something bridged so the symmetry could reduce some distortion, but that goes against the impedance issue I'll already face going OTL.
I haven't set anything in stone yet as to design, but I think I want SET, choke loaded. A little global NFB, for output impeadance reduction, not patching bad THD numbers like the japs of the 70's
In the end, this is more a journey of learning for me. Like my 833 amp, it may never get past plywood. The compromise I had to make with it was floating the speaker out terminals to get the frequency response high enough, then the leaked capacitance put 600V above ground on the speakers.
AND, I have another major project to finish before I do much more than think on this one. I have to finish my house.
I'm a follower of Pass. I'm a big believer in local feedback of cathode/emitter/source followers. His modulating the current source in the output stage to double efficiency of a pure class A source follower is gloriously brilliant.
I like Brodski's (possible misspelling) Aikio circuit injecting power supply noise into the current source to null it at the output.
I don't like overpriced boutique parts. If something (like an electrolytic cap) is inherently sonically bad, a more expensive one may be a little better, but you quickly run into diminishing returns. Another reason to avoid iron in the signal path where possible. I believe with good implementation and typologies, and running components in their sweet spot, $600 tubes that have had magic schmoo smeared on them, then baked in a oven, then frozen in liquid nitrogen is a waste of money when a $7 tube out of a TV vertical amp will do. No, I'm not a fan of "tweaks".
I do like the Techniques modified Futterman circuit. Tubetvr uses. Haven't yet studied the Mellow circuit.
I like simple circuits I can wrap my head around. Complicated ones that have too many variables have entirely too many ways to go wrong. So I limit myself to 3 pin active devices (not counting heaters and shields).
Unfortunately, with tubes, we don't have positronic based complementary units, so without a transformer to mirror things, we're limited to quasi-complementary typologies for push pull. I was considering something bridged so the symmetry could reduce some distortion, but that goes against the impedance issue I'll already face going OTL.
I haven't set anything in stone yet as to design, but I think I want SET, choke loaded. A little global NFB, for output impeadance reduction, not patching bad THD numbers like the japs of the 70's
In the end, this is more a journey of learning for me. Like my 833 amp, it may never get past plywood. The compromise I had to make with it was floating the speaker out terminals to get the frequency response high enough, then the leaked capacitance put 600V above ground on the speakers.
AND, I have another major project to finish before I do much more than think on this one. I have to finish my house.
Not really - 6C33C dissipates around 36 - 38W from each tube at the heaters - so thats 720 - 760W for 20; plus everying else, I'd guess your looking at about 1.2kW for two amplifiers. I suppose it saves having to burn logs in the fire in order to keep warm...
Edit: No details yet... Power Amplifiers NVS-150 Reference OTL Tube Power Amplifier | Navison Audio - The Natural Sound!
Happy New Year, everybody.
Edit: No details yet... Power Amplifiers NVS-150 Reference OTL Tube Power Amplifier | Navison Audio - The Natural Sound!
Happy New Year, everybody.
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What you see as the lower piece looking like a reflection is not reflection. .. they are exactly the PSUs, each twice bigger sized as an amp.
BTW, the heaters in such are sometimes connected in series to the Mains line, unsafe, but not everyone cares. You can easily google such the schematics.
But this one is not the biggest I've seen. .. some maniac possesses the unit with ~30 pieces PC, searched for that photo, can not find it. It seemed installed in a chapel, substituting the traditional organ (maybe).
Surely a link to the article would have been more appropriate. There's a lot of detail in the article regarding the various design choices. It's a good read, and likely to be much more instructive that just the schematic which includes a number of not so obvious elements.
Brazilian OTL
Brazilian OTL
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