Hi,
I have a simple EL34 SE Ultralinear amplifier kit amplifier (9 Watt, 6 Watt in Triode mode), no over all feedback. B+ is 375V. Originally, it had two simple gain stages per channel using a 6SN7. I removed one of the 6SN7 stages. The gain is now just sufficient for me.
I've seen the JJ 12AY7 has amazingly linear looking curves, much like a 6SN7. It looks better than a ECC82, 81 or 83 on paper. I have an adaptor where I can put noval tubes in my octal socket which works very well.
How does the 12AY7 work in driving the EL34 and how does it sound ? - Is it detailled and clear and still nice sounding ?
Thank you,
Günther
I have a simple EL34 SE Ultralinear amplifier kit amplifier (9 Watt, 6 Watt in Triode mode), no over all feedback. B+ is 375V. Originally, it had two simple gain stages per channel using a 6SN7. I removed one of the 6SN7 stages. The gain is now just sufficient for me.
I've seen the JJ 12AY7 has amazingly linear looking curves, much like a 6SN7. It looks better than a ECC82, 81 or 83 on paper. I have an adaptor where I can put noval tubes in my octal socket which works very well.
How does the 12AY7 work in driving the EL34 and how does it sound ? - Is it detailled and clear and still nice sounding ?
Thank you,
Günther
I forgot: Of course I will optimize values of anode and kathode resistors as good as possible ! - And I would like not to bypass the kathode resistor.
The 12AY7 is a very nice type. While JJ's Noval production is not nearly under the cloud their Octal production is, I would take a wait and see attitude with the JJ variant. The New Sensor product sold under the ElectroHarmonix (EH) brand has been trouble free and that's what I would buy.
Your UL mode "finals" could be an awkward load for the 12AY7. Compare plate resistance and gm of the 12AY7 to that of a 6SN7.
Your UL mode "finals" could be an awkward load for the 12AY7. Compare plate resistance and gm of the 12AY7 to that of a 6SN7.
I am sometimes puzzled why the characteristic plots for modern valves look astonishingly similar to the plots found in 60-year-old datasheets, even though it is reasonable to expect some differences. For instance, slightly different interelectrode capacitances suggest slightly different internal construction which should lead to slightly different curves. Certainly slightly different mu figures (JJ 40 vs GE 44) must lead to different plots, yet they seem not to. When someone actually plots an example of a modern valve it often looks quite different (especially at low currents) from the datasheet plot.
Do you think modern valve makers sometimes just publish the old curves? In many cases copyright will have elapsed.
Do you think modern valve makers sometimes just publish the old curves? In many cases copyright will have elapsed.
FWIW a JJ 12AT7 tried in a guitar effect pedal operating in starved conditions - 9V on the anodes - didn't work in spite of specs! It worked as expected in high voltage though...
Possibly not. However, if you can make an AT, AX and AU then an AY should not be too difficult. Especially if all you are aiming at is an AY characteristic and not necessarily AY (or AX) levels of noise. I note that the JJ datasheet describes the 12AY7 as an RF valve - true in the sense that it can be used for RF, but I have never seen an RF circuit specify a 12AY7. AX and AY were intended as audio valves; AT and AU were intended for RF.piano3 said:
I thought the whole point of the 12AY7 was low noise; I specifically remember seeing it in mic pre-amp circuits and, I think, phono input as well.
I have made curves ( uTracer) on some JJ 12AY7 and they do look like
the GE counterparts.... No significant differences
> 12AT7 and 12AY7 were designed for TV UHF tuners.
AY was clearly marketed at "low-level stages of high-gain audio amplification". The 10mA cathode current limit doesn't promise TV frequencies.
The AT is of course an early VHF tuner tube. While the present (past?) VHF band only goes to 216MHz (Ch13), the original allocation extended to a channel 19 which would be near the "300MC" on the AT datasheet. (Not the same Ch 19 found in the later UHF allocation.) The AT would be marginal even for for Ch13 (why broadcasters avoided the high channels at first) and marginal for wide range of signal level (such as found in US cities and suburbs). Much better (more bent) TV tuner tubes appeared, the 6BQ7 very popular for a while. The poor unwanted 12AT7 gradually gained sockets for small/medium power audio.
AY was clearly marketed at "low-level stages of high-gain audio amplification". The 10mA cathode current limit doesn't promise TV frequencies.
The AT is of course an early VHF tuner tube. While the present (past?) VHF band only goes to 216MHz (Ch13), the original allocation extended to a channel 19 which would be near the "300MC" on the AT datasheet. (Not the same Ch 19 found in the later UHF allocation.) The AT would be marginal even for for Ch13 (why broadcasters avoided the high channels at first) and marginal for wide range of signal level (such as found in US cities and suburbs). Much better (more bent) TV tuner tubes appeared, the 6BQ7 very popular for a while. The poor unwanted 12AT7 gradually gained sockets for small/medium power audio.
Back to my question: So is the JJ 12AY7 suitabke to drive my EL34 SE amplifier, and is it linear ? - Should I buy the EH or the JJ tube, what about the sound ?
Günther
Günther
It's not the most obvious choice for a driver valve; high ra and 10 mA maximum current. There are several excellent Russian pentodes which cost almost nothing on ebay; 6j9p wired as a triode is one which costs about a dollar and would be extremely suitable.
You would probably need some kind of active loading to benefit from its (12AY7) linearity and also drive the input capacitance of the output stage.
You would probably need some kind of active loading to benefit from its (12AY7) linearity and also drive the input capacitance of the output stage.
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12ay7 is mostly used in line output sections when it is in pro audio equipment. UA used it as that in some of there equipment (610, LA2a, etc)
another tube you might be interested in is the 12az7
Last time I built a little two tube amp like this, I used a 12ax7 and a el34 as my combo
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Why would anyone use a tube with datasheet anode resistance of 25 kohms as a line output? It wouldn't even be particularly suitable as a cathode follower (low gm).
Valves are used in pro audio equipment mainly as some combination of fashion statement and effects box. The fact that a valve is wholly unsuited to a particular circuit role (for hi-fi sound reproduction) does not mean that it cannot be used for other purposes, such as marketing.
Annoyingly often folks try to make a design around some tubes "they got cheap" or "found in the drawer" instead of using the proper ones.
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