Motown Direct Amplifier-inspired Preamp?

[DaveP]

So the circuit now has two 15k grid stoppers and a 20pF by-pass cap?
Can I update the circuit yet?
best
DaveP

 

[heatwalk]

Just chiming in to say this has been a great thread to read thus far - shouts out to Dave and CJ and everyone else! Love this forum to see and learn from projects like this.

 

[CJ]

Dave there us a 68K on both grids of the 6N1P and a 15K on the 6BX7 and a 20 pf dogbone cap on the f/b resistor but a ceramic would work just as well.

A Jensen 4:1 output would probably sound awesome in this circuit.

 

[DaveP]

This is the schematic as it stands today:-

The 6N1P was a Russian tube introduced in 1954, I'm not sure if it was imported into the US before the Motown amp was made.
The ECC88/6DJ8 was introduced into the US in 1957. We cannot be sure if we have duplicated the original circuit but it looks like we have matched the spec. Thanks CJ.
best
DaveP

 

[capacitorless]

Not to derail, but I'm just (thanks, Dave & CJ!) finding out about the 6N1P, as a possible replacement for the ecc88 type. Is this a superior device in this particular circuit?

I know there's more filament draw, just wondered about the other parameters.

 

[My3gger]

Dave there us a 68K on both grids of the 6N1P and a 15K on the 6BX7 and a 20 pf dogbone cap on the f/b resistor but a ceramic would work just as well.

A Jensen 4:1 output would probably sound awesome in this circuit.

Do nickel core outputs sound better to you in general, despite higher price for Ni, or just in particular applications like this mic amp/DI where majority would go for steel core? I like them a lot, despite slightly higher distortion if Ni core isn't quite a bit bigger than the same steel core.
If Davep, Ian, you and others think it is appropriate, we could have OEP also make some typical tube output ratios. One OT the offered to me as a sample had 80Ni core with 2:1 ratio, i will certainly call them soon and post the test (electronic and listening).

 

[My3gger]

This is the schematic as it stands today:-

The 6N1P was a Russian tube introduced in 1954, I'm not sure if it was imported into the US before the Motown amp was made.
The ECC88/6DJ8 was introduced into the US in 1957. We cannot be sure if we have duplicated the original circuit but it looks like we have matched the spec. Thanks CJ.
best
DaveP

Strange, schematic only opens if i quote that post.

 

[DaveP]

Not to derail, but I'm just (thanks, Dave & CJ!) finding out about the 6N1P, as a possible replacement for the ecc88 type. Is this a superior device in this particular circuit?

The circuit was designed for the ECC88, but as CJ has shown, it also works very well for the 6N1P with slightly different voltages.
best
DaveP

 

[DaveP]

Strange, schematic only opens if i quote that post.

I had trouble with my usual image site and had to use another.
best
DaveP

 

[Disco Volante]

Works fine here. Great work!