Hi, just bought some pairs of "matched" Golden Lion reissue 12AX7, NOS Telefunken 12AX7 smooth plate diamond bottom, and NOS milspec Mullard CV4024 (12AT7).
Mullard CV4024: Mu 51.8/42.1 53.1/45.2
Golden Lion: Mu 97.2/95.5 96.7/99.0
Telefunken: Mu 91.5/91.5 91.0/91.8
My questions:
1) I'm not a tube expert but the Mullard is wildly off internally, 20% mismatch for one and 16% for the other. Between tubes seem relatively close, but still imbalanced internally. Would you return these for better matched pair?
2) I suppose the Golden Lion is pretty close. Is this acceptable?
3) The Telefunkens are almost perfectly matched. But absolute values seem a little low for NOS. Should be close to 100 according to specs. Is this acceptable? Especially given, I paid over $100 each for these.
Thanks for your input.
Mullard CV4024: Mu 51.8/42.1 53.1/45.2
Golden Lion: Mu 97.2/95.5 96.7/99.0
Telefunken: Mu 91.5/91.5 91.0/91.8
My questions:
1) I'm not a tube expert but the Mullard is wildly off internally, 20% mismatch for one and 16% for the other. Between tubes seem relatively close, but still imbalanced internally. Would you return these for better matched pair?
2) I suppose the Golden Lion is pretty close. Is this acceptable?
3) The Telefunkens are almost perfectly matched. But absolute values seem a little low for NOS. Should be close to 100 according to specs. Is this acceptable? Especially given, I paid over $100 each for these.
Thanks for your input.
Acceptable on what basis? An instrumentation application might fail them, but then, an instrumentation amplifier would contain enough negative feedback to overcome such differences with room to spare.
For audio purposes, even the worst '4024 halve vs. the best Golden Lion halve is not a huge difference: a mu-stage will differ by 7.4dB, which means you'll change the volume control once and forget about it (the 12AT7 distortion may be noticable, but that depends on design). You won't discern the differences between Golden Lion and Telefunken devices at all: the worst mismatch is only 0.73dB.
All in all, I'd be very concerned if you had a circuit that was so knife-edge unstable that 0.73dB variance was enough to make it malfunction. That's not a tube problem, that's a fundamental design issue!
Tim
For audio purposes, even the worst '4024 halve vs. the best Golden Lion halve is not a huge difference: a mu-stage will differ by 7.4dB, which means you'll change the volume control once and forget about it (the 12AT7 distortion may be noticable, but that depends on design). You won't discern the differences between Golden Lion and Telefunken devices at all: the worst mismatch is only 0.73dB.
All in all, I'd be very concerned if you had a circuit that was so knife-edge unstable that 0.73dB variance was enough to make it malfunction. That's not a tube problem, that's a fundamental design issue!
Tim
Mullard CV4024 are often poorly matched. I'm not sure if that means they were built to optimise something else (CV4000 series are supposed to be 'better' than earlier versions), or just that we are now left with the dross.
For good section matching try RFT, although they may be branded as something else (e.g. Mazda foreign).
For good section matching try RFT, although they may be branded as something else (e.g. Mazda foreign).
The CV4xxx series are of rugged construction and usually differ in construction to standard types . I have tested my way through many hundreds of NOS Mullard CV4024/M8162 from mid 1970's to final 1985/86 production and find these test all over the shop with many having sectional matching way off such as 4.5mA/V one side and 6mA/V the other .
316a
Hmm, ruggedized versions were subjected to more thorough tests. I heard a story that early transistors, in ruggedized military versions, were *less* reliable than their commercial counterparts, because the commercial parts were tested by sampling and not subjected to the rigors of military testing, which irreversibly stressed the parts inside.
I haven't heard of this for tubes, and all "ruggedized" tubes I've seen really are beefier inside (the most amazing examples being tubes like the Bendix 6384, equipped with with hard glass envelope, ceramic insulators, quadrupled alignment pins and shock absorbing springs), and I have no doubt they would survive testing, and continue to provide high-reliability service under very harsh conditions.
Just a thought.
Tim
I haven't heard of this for tubes, and all "ruggedized" tubes I've seen really are beefier inside (the most amazing examples being tubes like the Bendix 6384, equipped with with hard glass envelope, ceramic insulators, quadrupled alignment pins and shock absorbing springs), and I have no doubt they would survive testing, and continue to provide high-reliability service under very harsh conditions.
Just a thought.
Tim
Not sure. The Mu values are written on the box that the tube came in. I bought it from Partsconnexion who measured these values.
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