Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => MonAmour => Topic started by: triode on July 19, 2020, 10:58:16 PM

Title: 6DJ8 to substitute 5670
Post by: triode on July 19, 2020, 10:58:16 PM

Hi

I have a stash of 6DJ8/6992 tubes, some are quite exotic (Siemens CCa, etc)
Just wondering if I can substitute the 5670 tube with 6DJ8 without any circuit change?
I understand that tube socket adaptor would be needed since the pinout of these tubes are different.

Looking at tube datasheet, 6DJ8 will have lower anode voltage, around 130-150V. Would that too much for the CS4?

Note that I replaced the cathode's TL431 network with 930ohm resistor to reduce the hiss in my high sensitive tweeter (as per PB in other thread)   

Thanks

Title: Re: 6DJ8 to substitute 5670
Post by: Paul Joppa on July 20, 2020, 04:37:23 AM

No.

One half is the plate voltage regulator running at 300v, which exceeds the rating for either tube. And because the plate resistance is half that of the 5670, both halves would require twice the current in order to operate in the linear region. And if they DID run that way, the plate dissipation limits would exceed the rating. And finally, the 5670 is quite a bit more linear.

Title: Re: 6DJ8 to substitute 5670
Post by: triode on July 20, 2020, 09:50:20 AM

OK, I'll stick with 5670...

Thanks Paul