Hi xraylaser.
I agree with you. For what it’s worth I popped the 12CG7 tubes in. Unfortunately I think they’re DOA - no treble at all.
Anyone know if this is a 6/12v issue or just dead tubes?
I agree with you. For what it’s worth I popped the 12CG7 tubes in. Unfortunately I think they’re DOA - no treble at all.
Anyone know if this is a 6/12v issue or just dead tubes?
12AU7, 12AT7, 12AY7, 12AX7, 12BH7 all have the same pin-out.
But the 12BH7 has 2X the filament current of all the others (a little more load on the power transformer, hpe it is not running hot already).
Maximum Plate Dissipation, Watts:
12AU7 2.75
12AT7 2.5
12AY7 1.5
12AX7 1.2
12BH7 3.5
Pity the poor 12AX7 that is plugged into a maxed out 12AU7 or 12BH7 circuit.
The u of those tubes varies from 16.5 to 100.
If we try to use one of the higher u tubes, we might be able to increase the gain enough to make the global negative feedback unstable, then we would have a power oscillator instead of a power amplifier (your ears and your speakers would not like that).
Plug and Pray at your own risk.
But the 12BH7 has 2X the filament current of all the others (a little more load on the power transformer, hpe it is not running hot already).
Maximum Plate Dissipation, Watts:
12AU7 2.75
12AT7 2.5
12AY7 1.5
12AX7 1.2
12BH7 3.5
Pity the poor 12AX7 that is plugged into a maxed out 12AU7 or 12BH7 circuit.
The u of those tubes varies from 16.5 to 100.
If we try to use one of the higher u tubes, we might be able to increase the gain enough to make the global negative feedback unstable, then we would have a power oscillator instead of a power amplifier (your ears and your speakers would not like that).
Plug and Pray at your own risk.
@6A3sUMMER
Thanks for that explaining in your previous posts.
I didn't want to get all into that stuff, I just gave basic info.
And yes, a 12AX7 with its high mu needs its own circuitry designed for it.
It cracks me up, those musicians, who "roll" the 12xxx's without having the sense to understand the differences, only "how they sound".
So much for amateurs....
Thanks for that explaining in your previous posts.
I didn't want to get all into that stuff, I just gave basic info.
And yes, a 12AX7 with its high mu needs its own circuitry designed for it.
It cracks me up, those musicians, who "roll" the 12xxx's without having the sense to understand the differences, only "how they sound".
So much for amateurs....
I sleep well, thanks.
It's just that being "in the business" for 45+ years, and knowing my trade as I do, I simply don't buy into hype and "what ifs" when I know better from experience.
Thanks Chris. What do you mean by "no xCG7 type will work at all, not even light up"? That no xCG7 will work in my amp circuit? or not if wired for 6.3v? Because when I popped them in, they didnt light up or get warm at all
@wiseoldtech - with all your experience, I am curious what amp and speakers you use, if you dont mind?
@Wilsonron
I have various systems at home, including my own designs.
Nothing expensive, yet my audio friends are impressed, and they wonder why they spent so much on "high end" stuff.
I have various systems at home, including my own designs.
Nothing expensive, yet my audio friends are impressed, and they wonder why they spent so much on "high end" stuff.
Type xCG7 has its heater connected between pins 4 and 5. Type 12BH7, etc. has two 6.3 volt heaters connected between pins 9 and 4 and between pins 9 and 5. You really really need to look at the pinouts of the valves you're interested in. This 101 stuff.
All good fortune,
Chris