The idea of using a pair of 6AU6s for a lower power application intrigues me... Honest-to-goodness tiny little beam tubes in a 7-pin base! The RCA manual says they're pretty much the same as a 6V6 within their ratings... I'm thinking a pair of these in ultra linear ought to make for a pretty good sounding output stage for a receiver I'm thinking of building.
I'm looking for low distortion, about 10W output, and a compact design. Could use 6BQ5s I guess, but the idea of true beam pentodes sounds better for some reason. I also found the 6973 (or was it 7369?) but my goodness, they want $30 a pop for these beauties- and it looks like they're a bit rare. 6AU6's are available everywhere, at bargain-basement prices (well, ALMOST...) I only hope there's not a good reason for that.
Strangely, there's almost a complete lack of information/results out there from anyone that's actually built anything using them- it's as if the world hasn't heard of this tiny little miracle...!
Or are they junk?
Anyone have any actual experience in using these for a 10W audio amp? How did they work out?
I'm looking for low distortion, about 10W output, and a compact design. Could use 6BQ5s I guess, but the idea of true beam pentodes sounds better for some reason. I also found the 6973 (or was it 7369?) but my goodness, they want $30 a pop for these beauties- and it looks like they're a bit rare. 6AU6's are available everywhere, at bargain-basement prices (well, ALMOST...) I only hope there's not a good reason for that.
Strangely, there's almost a complete lack of information/results out there from anyone that's actually built anything using them- it's as if the world hasn't heard of this tiny little miracle...!
Or are they junk?
Anyone have any actual experience in using these for a 10W audio amp? How did they work out?
Re: 6AU6s in push-pull
Greetings from FixitLand!
I think you've confused 6AU6 with 6AU5-GT...6AU5-GT is in fact a beam power tube (octal base) for TV H sweep applications with 10 W plate dissipation rating in that service. 6AU6 is a small-signal 7-pin sharp-cutoff pentode with 3.5 W plate dissipation rating -- nowhere near a 6V6 <grin>.
Or you're thinking of a 6AQ5, which IS a 7-pin near-equivalent of a 6V6. I used a couple 6AQ5s in P-P (not UL) in the homebrew radio I built a few years ago; sounds great.
Take care,
--
J. E. Knox 'The Victor Freak'
Greetings from FixitLand!
I think you've confused 6AU6 with 6AU5-GT...6AU5-GT is in fact a beam power tube (octal base) for TV H sweep applications with 10 W plate dissipation rating in that service. 6AU6 is a small-signal 7-pin sharp-cutoff pentode with 3.5 W plate dissipation rating -- nowhere near a 6V6 <grin>.
Or you're thinking of a 6AQ5, which IS a 7-pin near-equivalent of a 6V6. I used a couple 6AQ5s in P-P (not UL) in the homebrew radio I built a few years ago; sounds great.
Take care,
--
J. E. Knox 'The Victor Freak'
hey-Hey!!!,
The 6AU6 is a three-grid, signal pentode pentode. I don't think you'll get 10W; not enough plate dissipation. 2W should be possible.
cheers,
Douglas
The 6AU6 is a three-grid, signal pentode pentode. I don't think you'll get 10W; not enough plate dissipation. 2W should be possible.
cheers,
Douglas
AAAUUUUGH!!!
I meant 6AQ5, not 6AU6
Yes, Shoog... 10W is a bit ambitious for a pair of 6AU6 pentodes designed for RF amp service...!!
And Rojoknox, tnx for waking me up! You did succeed at guessing what I was *really* thinking about!
<groan> Sorry for the confusion!!
I meant 6AQ5, not 6AU6
Yes, Shoog... 10W is a bit ambitious for a pair of 6AU6 pentodes designed for RF amp service...!!
And Rojoknox, tnx for waking me up! You did succeed at guessing what I was *really* thinking about!
<groan> Sorry for the confusion!!
You could try with the EH 6973's. They are very good indeed.
You can buy a matched quad for 60$.
Cheers,
45
6AQ5 is a beam Tetrode (6BQ5 is a Pentode).
That aside the 6AQ5 should make for a nice amp with 8W (UL) to 10W(Straight Tetrode PP. If you need more than 10W you could go with a 5K p-p transformer and do a Parallel Push Pull, but getting tubes matched close enough might be an issue.
I'm working on a 6P1P-EV PP version with selectable UL or not.
That aside the 6AQ5 should make for a nice amp with 8W (UL) to 10W(Straight Tetrode PP. If you need more than 10W you could go with a 5K p-p transformer and do a Parallel Push Pull, but getting tubes matched close enough might be an issue.
I'm working on a 6P1P-EV PP version with selectable UL or not.
6AQ5 == minature 6V6. Use any 6V6 schematic 🙂
Though when I was a kid, I made a modulator for a mini AM TX from a pair of PP 6AU6 and it worked OK 😎
Cheers!
Yes, I've got an H.H. Scott 299B amp with 6BQ5 pentodes... A nice amp, to be sure, but after designing with beam tetrodes, it seems I can do better on performance (notably distortion) than by using pentodes.
I don't need much power- I'm thinking of making an AM/FM radio but paying attention to getting the best fidelity possible (instead of the usual single-ended 50C5, use a pair of 6AQ5s, and instead of a diode detector, use a product detector, synchrodyne, or some such) etc. etc.
So a few watts is fine. Even 2-3 watts of really clean audio would be a vast improvement over what the All American Five typically offers.
The 6973 looks like a GREAT tube... I may give it a shot despite the cost... I just thought that if I could get good results from a pr of 6AQ5s, why not? -But if someone knows why not (if there's something fundamentally wrong with the idea) I'll go straight to something better- likely 6973s.
I'll have to look up the 6P1P-EV thing... not familiar with that. It'd be fun to be able to switch UL or not while listening (avoiding any big transients, etc). I made measurements and convinced myself that UL would likely sound better, but there's nothing like actually LISTENING in a real A-B way to decide for real.
As Dan von Recklinghausen said, "If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you've measured the wrong thing."
I don't need much power- I'm thinking of making an AM/FM radio but paying attention to getting the best fidelity possible (instead of the usual single-ended 50C5, use a pair of 6AQ5s, and instead of a diode detector, use a product detector, synchrodyne, or some such) etc. etc.
So a few watts is fine. Even 2-3 watts of really clean audio would be a vast improvement over what the All American Five typically offers.
The 6973 looks like a GREAT tube... I may give it a shot despite the cost... I just thought that if I could get good results from a pr of 6AQ5s, why not? -But if someone knows why not (if there's something fundamentally wrong with the idea) I'll go straight to something better- likely 6973s.
I'll have to look up the 6P1P-EV thing... not familiar with that. It'd be fun to be able to switch UL or not while listening (avoiding any big transients, etc). I made measurements and convinced myself that UL would likely sound better, but there's nothing like actually LISTENING in a real A-B way to decide for real.
As Dan von Recklinghausen said, "If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you've measured the wrong thing."
The 6P1P seems to be a Russian equivalent of the 6AQ5, with a different pin out. I've seen a few sellers advertising it as a 6BQ5 equivalent which it is not (6P14P is close to 6BQ5).
I think the military (XXXXX-EV) tubes are supposed to be better quality than the standard tubes.
Low power + good speakers = pleasant listening
I think the military (XXXXX-EV) tubes are supposed to be better quality than the standard tubes.
Low power + good speakers = pleasant listening
I tried using the 6AQ5 as a preamp tube, but found it very microphonic. I don't suppose this would be an issue in output duty.
Shoog
Shoog
How many brands did you try? Not all of them are.
The Valvo EL90 is really nice.
Cheers!
The 6AQ5 is electrically equivalent to the 6V6 except it is less rugged but more compact. The 6005/6005WA, EL90, 6P1 (different pinout) are equivalent.
I prefer the 6V6GT.
The 6973 is in another league. IMHO, even the modern ElectroHarmonix tube is better than 6AQ5. Being a more recent tube and having higher plate/g2 voltage ratings in comparison to the common EL84 you can get 2-3 additional watts from PP, both UL and penthode, at the same THD. To match the 6973 you have to go for the E84L/7723 or the true american 7189a......
Another similar and very useful tube is the 6CZ5. This has higher plate resistance and higher mutual conductance than the 6AQ5.
The EL82 is another very good cheap tube.
If you don't mind about power output and are looking for quality you can consider the E80L too.
Cheers,
45
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The 6BW6 works very stable at Ua(Ub)=350V and Ug2=320V(Rg2=470ohmsx2) several Year in my small home-made guitar amplifier. Rk are 2x470ohms, Ia=37mA(x2), Pa~2x12W and real Ua-k is 322V.
It sounds like the 6CZ5 is just what I was looking for-! after 20 years of reading the RCA tube manual cover-to-cover, I'd never heard of the 6CZ5 until 2 minutes ago...!
The 6973 does sound like a more modern tube than the 6AQ5, but they're about $30 each. I can get the 6CZ5 for only about $10 each- much more reasonable, and it looks like the performance is comparable to the 6973.
The circuit I'm thinking of using this for will become a sort of generic output stage I'll use whenever I need a few watts of good, clean audio- not the ultimate in performance, but just a good, clean, small, lower-power stage.
The 6V6 (especially the GT) would be great, too- but I'm thinking of using this circuit as the output stage of a higher-fidelity AM/FM receiver, sized about like a "table radio"- so I'd like to keep things small- miniature bases preferred for this project.
Thanks for calling my attention to the 6CZ5 -looks great!
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