Since this thread has drifted to things 6J52P...
I have a preamp with triode wired E810F in the first stage. I want to try a triode wired 6J52P in the circuit, to see how it compares.
I checked the pin-outs, and see that the only difference looks to be how pin 8 is connected.
In E810F, pin 8 is connected to grid 3 (suppressor grid) and to an internal shield.
In 6J52P, pin 8 is connected to grid 3 (suppressor grid) only.
My question:
Using the E810F, should I strap pin 8 to the cathode (pins 1 and 3)? If I do that, the cathode will then be connected to the internal shield. Is that OK?
Using the 6J52P, I assume strapping pin 8 (grid 3) to the cathode (pins 1 and 3) will be correct.
So if I can make a permanent connection of pin 8 to the cathode, then I can simply swap the two types in this preamp (and tweak later). But if there's a problem with connecting the E810F suppressor+internal shield directly to its cathode, then I might need to do it differently. Advice for me?
Thanks,
I have a preamp with triode wired E810F in the first stage. I want to try a triode wired 6J52P in the circuit, to see how it compares.
I checked the pin-outs, and see that the only difference looks to be how pin 8 is connected.
In E810F, pin 8 is connected to grid 3 (suppressor grid) and to an internal shield.
In 6J52P, pin 8 is connected to grid 3 (suppressor grid) only.
My question:
Using the E810F, should I strap pin 8 to the cathode (pins 1 and 3)? If I do that, the cathode will then be connected to the internal shield. Is that OK?
Using the 6J52P, I assume strapping pin 8 (grid 3) to the cathode (pins 1 and 3) will be correct.
So if I can make a permanent connection of pin 8 to the cathode, then I can simply swap the two types in this preamp (and tweak later). But if there's a problem with connecting the E810F suppressor+internal shield directly to its cathode, then I might need to do it differently. Advice for me?
Thanks,
The D3a has the same pin-out as the E810F (with pin 8 connected to g3 and a shield). The Telefunken data sheet allows connection of g3 + s to either anode or cathode so I don't think you'll have any problems triode-connecting an E810F either way. I too use a triode-connected E810F as the first stage in a pre-amp (a phono preamp) and it is possible to substitute D3a or 6J52P (or E280F, or even E282F!) without any crisis arising.
I think you will find that 6J52Ps are extremely variable and very prone to microphonics. I only found two out of twenty that worked properly. I eventually settled on E810Fs as the most stable and least likely to turn into sound effects devices.
I think you will find that 6J52Ps are extremely variable and very prone to microphonics. I only found two out of twenty that worked properly. I eventually settled on E810Fs as the most stable and least likely to turn into sound effects devices.
Just an update -- I got a bunch of 6J52P from an ebay seller in Moscow. Popped a couple in the phono preamp, replacing the 7788's that were in there. 6J52P-triode is working fine, sounds pretty similar to the 7788's in triode. I must have good tube karma these days, as these 6J52P's are no more prone to ringing than the 7788's, at least in this particular circuit.
The first stage has +215V B+, 9.1k ohm plate resistor, IR LED in the cathode (-1.2V g-k). The DC heater voltage is a bit low at 5.9V DC. Maybe not ideal conditions, but in the ballpark.
The 7788-triode draws 14mA, while the 6J52P draws 12mA. I did find that the amount of current draw varies a fair amount from tube to tube, but this is true for both E810F/7788 and 6J52P.
-=|=-
The first stage has +215V B+, 9.1k ohm plate resistor, IR LED in the cathode (-1.2V g-k). The DC heater voltage is a bit low at 5.9V DC. Maybe not ideal conditions, but in the ballpark.
The 7788-triode draws 14mA, while the 6J52P draws 12mA. I did find that the amount of current draw varies a fair amount from tube to tube, but this is true for both E810F/7788 and 6J52P.
-=|=-
Last edited:
For D3A tube, that is 'Anode and grid No. 2 to grid No. 1' Cag2/g1. Is it actually Cag value?
And what about Cag1? There is no value for Cag1 in datasheet.
Does anyone know how to calculate Cag value for 7788 tube?
Did you perhaps not understand the post you quoted? You are interested in triode mode? Do you not understand the difference between a triode and pentode? The 2.7 pF is Cag when shorting g3 to cathode and shorting g2 to anode. The 3.3 pF is Cag when shorting both g2 and g3 to anode.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.