YOU cannot. The bias is very different. the cut off is -2V for the ECC81/12AT7 and -8V for the ECC82/12AU7. The plate current is 10 mA both for the ECC81 and ECC82
It's unlikely that you can substitute the tube directly without other circuit changes.
Why do you need more gain, for phono or line level?
The 12AU7 is a low gain tube with a mu of 20. The 12AT7 has a mu of 60.
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I need more gain I thought that the ecc81/82/83 can be change without damage anything.
I have try now an step up on MM but still not enough gain.
Many to try the change the fet.
I have try now an step up on MM but still not enough gain.
Many to try the change the fet.
First you said you don't get enough gain at line level but the SFP-1 is a phono preamp. And now you said you need a "step up on MM". I am really confused. What is it that you're trying to achieve? Can you tell us more about your system or what's in the signal path, what kind of cartridge you're using?
Need more gain if I try an simple phonomena phono stage I have more gain. Now 58 phonomena 65
So if I need more gain on the line of phono I don't know
So if I need more gain on the line of phono I don't know
Here you can find the specs and downloadable user manual. I wouldn't change the tubes and should leave them as intended. 12AU7 will give you LESS gain. Assuming you are using a low output MC cartridge, you can try to add a step-up transformer of moderate gain and make sure the MC stage's input impedance stays at 47K. Or you can using a high gain step-up transformer into the MM stage. Or you can use a line preamp with higher gain. Or.... use a different phono preamp!
I have try an stepup t5 with MM, but when connecting the t5 less gain.
What does go wrong. It should have more gain.
What does go wrong. It should have more gain.
use the phono stage in MM 37dB with T5 26dB total 63 dB
connecting the T5 but the gain is lower instead of higher
strange....
connecting the T5 but the gain is lower instead of higher
strange....
There is no SUT I am aware of that is compatible with an MM (moving magnet) cartridge. Connecting an MM to a typical MC SUT will present the MM cartridge with something looking a lot like a short to its relatively high source impedance, the transformer gain will not compensate for that.
The circuit looks 'interesting'. I am unable to see exactly how they do RIAA, but I suspect that the curve will depend on valve gain rather more than is wise from an engineering point of view. Scope for tube rolling, though! Some may regard this as a good feature.
Sorry. To change the gain would need a redesign. To do a redesign would require a careful reverse engineering of an 'interesting' circuit - which may or may not contain basic flaws. You can't simply swap valves and get more gain.
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