A friend likes my 6H30 / transformer output headphone amp and has asked me to build something similar for him. However he wants the tube on display, and wants ‘a big looking tube’. He means something that looks like a 2A3 for example.
So is there a triode (or triode strapped pentode) that has the following:
Mu about 12 – 18
Internal impedance Rp of less than 2000 Ohms
Indirectly heated cathode
Physically bigger than a 6H30 (i.e. bigger than a typical 9 pin tube)
Any type of base / socket is OK
What would you recommend?
So is there a triode (or triode strapped pentode) that has the following:
Mu about 12 – 18
Internal impedance Rp of less than 2000 Ohms
Indirectly heated cathode
Physically bigger than a 6H30 (i.e. bigger than a typical 9 pin tube)
Any type of base / socket is OK
What would you recommend?
Hi !
6S41S /6C41C Russian/!! Ri = apr. 300 ohm/!!/, mu = 16-19!!
http://scottbecker.net/tube/sheets/018/6/6S41S.pdf
Very good vision!
6S41S /6C41C Russian/!! Ri = apr. 300 ohm/!!/, mu = 16-19!!
http://scottbecker.net/tube/sheets/018/6/6S41S.pdf
Very good vision!
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How about 6AS7? Looks similar to 2A3 and no OPT needed, see this project for example:
HeadWize - Project: A Single-Ended OTL Amplifier for Dynamic Headphones by Aren van Waarde
I haven't heard that headphone amp but I did build the 6SN7/6BL7 by Eric Barbour some years ago (also on Headwize) and I really liked it. A good preamp with enough power for my 150ohm Sennheiser headphones.
speleo
HeadWize - Project: A Single-Ended OTL Amplifier for Dynamic Headphones by Aren van Waarde
I haven't heard that headphone amp but I did build the 6SN7/6BL7 by Eric Barbour some years ago (also on Headwize) and I really liked it. A good preamp with enough power for my 150ohm Sennheiser headphones.
speleo
The only "affordable" G-style tube that comes to mind is the Russian 6F6G. This is a little higher Rp and a little lower mu (triode connected) than you're looking for... and then there are the Chinese 6L6s that look like mini 6550s. In GT style, 6AH4 and 6CK4 are possibilities, as is 6EM7 and the like if you need a gain stage. Of course, I'm thinking in terms of what's in MY basement...
I have the same OTL 6AS7 /6H13C Russian/ and Sen. 580 - 300 ohm, I think this is the best tube cathode follower
for OTL! Ri is aprox. 300-400 ohm. I advise You this link!
Second that!
Remove the cover carefully to display the mesh grid. (I was corrected when I called it "mesh plate" in another post.) You will need to put a small marking on the glass to keep track of the orientation when the cover is removed. These tubes are also used in AYONs statement preamps.
I bought most of my C3ms from Frag Jan zuerst --- Ask Jan First a few years back. Also bought the rare 6.3V version, C30, before the prices took off.
How about a pair of 5u4's as a bridge rectifier, and maybe some 0D3's as regulators, and then stick with the appropriate 6H30 for amplification?
I hadn't thought of that, but it's certainly a nice idea, and it'll not blow his budget.
I'll be spending the weekend crawling over the 'net and reading up on the recommendations that you have all contributed. I would like to say a big 'thank you' to all for your help.
6AS7 and other similar
these 6AS7 and the russian types are designed to regulate DC voltages. This application does not need to be linear. And, their linearity is not good, despite what people say which have built with them... no one of them would
tell, that the own creation is not good. also, these bottles need driving voltage exceeding many real audio tubes driving voltage. I tested the 6H30 in some applications, designed for it, it is near to perfect to do the job. linearity is very good. you may even use systems in parallel to half the Rp. and double the slope. with this, efficiency is up against the 6AS7 etc.
we tube people should also show a bit responsibility for energy saving projects. and, triodes are already the worst case for that.
these 6AS7 and the russian types are designed to regulate DC voltages. This application does not need to be linear. And, their linearity is not good, despite what people say which have built with them... no one of them would
tell, that the own creation is not good. also, these bottles need driving voltage exceeding many real audio tubes driving voltage. I tested the 6H30 in some applications, designed for it, it is near to perfect to do the job. linearity is very good. you may even use systems in parallel to half the Rp. and double the slope. with this, efficiency is up against the 6AS7 etc.
we tube people should also show a bit responsibility for energy saving projects. and, triodes are already the worst case for that.
This is not completely true. The 6AS7G RCA was born an audio amplifier, too. From the RCA 1951 tube manual : " Glass octal type used as a regulator tube in dc power-supply units, as booster tube in the scannig circuit of television receivers, and as a pushpull class A output tube in high fidelity audio amplifiers....."
http://www.pmillett.com/tubedata/RC16.pdf look here (pag. 117). A 10W PP amplifier is in the circuit section (pag. 276).
The NOS RCA 6AS7G is more linear than the Russian version that has always been built for DC regulation only.
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ofcourse they want to sell their stuff as much as possible, marketing bla bla, design target wasn't audio. goehte said already: what you got printed on a paper, you may carry home. its an irony..so, why the 6AS7 never was really used for recording?\
RCA etc. want to sell, to sell, to sell...
RCA etc. want to sell, to sell, to sell...
There were several published articles in the '50s using the 6AS7 in power amps. Problem is, it's a bear to drive because the mu is so low. The 6528 is considerably better (mu = 14), but it came along as interest in tube amps was starting to fade. The 6C33 is quite popular nowadays, too, and it's of the same family, though much stouter than the 6AS7.
i not like a truck as a racing car. i dont know, why people defend this idea always against better knowledge. there is so much better stuff around. i dont use my umbrellar to make an airplane, they do it and say, it is flying nicely. tubes are in general high impedance, low current devices, why force them into an odd job? nowadays , everything must be bent with force until it fits. every tube now becomes "audiophile" no matter what its design target, the japanese are masters of mis-using. motto: the stranger, the better. others use 4CX250 or so transmitting tubes, stating revolutionary results. but a few only some ending up in a well selling design.
i have a word for this, but i am not allowed to use it here. i ask, if these things are so good, why they have not been published by tube manufacturers in a great amount? we dont need vacuum tubes for a special purpose, every tube can do. as long as it lookks great, it must sound great. but: i dont take measurenment to publish, i am careful, you know.
no S/N figures, no flicker noise, no frequency response, no intermodulation effects, no this, no that, just only in best case: THD. and THD is nothing.
only statemant: sound is ok.
ofcourse i can use tubes in different way, but why we have so many differnt types? RCA, Sylvania, Mullard not need to spend money to design, just define the use newly.
i have a word for this, but i am not allowed to use it here. i ask, if these things are so good, why they have not been published by tube manufacturers in a great amount? we dont need vacuum tubes for a special purpose, every tube can do. as long as it lookks great, it must sound great. but: i dont take measurenment to publish, i am careful, you know.
no S/N figures, no flicker noise, no frequency response, no intermodulation effects, no this, no that, just only in best case: THD. and THD is nothing.
only statemant: sound is ok.
ofcourse i can use tubes in different way, but why we have so many differnt types? RCA, Sylvania, Mullard not need to spend money to design, just define the use newly.
The 6AS7G in audio application has much higher internal resistance than 280 ohms. The problem has noted by SY is just the low gain.
For example, in the RCA 10W amplifier each triode works around 250V/50 ma -133V bias. In this condition the tube will have 770 ohm internal resistance (like a 300B!!) a 2 mA/V mutual conductance.
The gain is 1.55 and this is the only trouble.
RCA produced so many tubes that had no reason to sell the 6AS7G for audio tube if it was not suited.....
In 1950's globalization didn't exist, yet!
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Most tube amp manufacturers are not exactly groundbreaking pioneers, least of all during the 6AS7's production period. And cost was paramount. A diyer doesn't have those constraints, nor does he have to worry about long-term supply of obsolete tubes for his customers. So, free of those constraints, he can take advantage of the low plate resistance of series regulator tubes, which reduces the Bad Things that output transformers do.
There is no reason to handcuff diyers with commercial considerations.
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