For everyone who subs a 6N1P-EV for a 6922.

Posted by twystd (A) on July 30, 2008 at 09:36:29

In Reply to: How do you test these things? posted by Dave Pogue on July 30, 2008 at 05:15:55:

I don't think it's a problem with your tube tester. Although the mu is similar, the 6N1P is not a one to one equivalent, like many people think. Besides differences in heater current 310ma vs 600ma, there is a significant difference in plate resistance and therefore transductance. The 6N1P-EV will operate at much less current when driven at optimized operating points of the 6922. The Soviet era direct drop in for the 6922 is the 6N23P-EV, you might want to try some early 70s production of these.

If you think the 6N1P-EV sounds great, you ought to hear it at optimized operating points! Get the plate voltage in the 180-200V range, and bias it at -2 to -3.V and it'll really sing. I'm running mine at 200V on the plate, and a bias of -2.6V, which gives me about 8.3ma. My 8ma plate chokes are the limiting factor here.

Here's a data sheet on the 6N23P-EV: http://www.mif.pg.gda.pl/homepages/frank/sheets/112/6/6N23PEV.pdf

Here's a data sheet on the 6N1P-EV: http://www.mif.pg.gda.pl/homepages/frank/sheets/113/6/6N1PEV.pdf

As you can see the plate curves are quite different, for example an operating point of 120V on the plate, and -2V bias the 6N23P-EV operates at about 10 MA and is in a fairly linear part of the curves, with about 67% max dissipation.

With the same 120V on the plate and -2V bias (the only way you'd really know these voltages is to measure in the circuit) the 6N1P-EV is operating at about 2.5ma, and the operating point is way down in the toe of the curve, a not so linear operating point. Also it is only operating at about 14% of the rated max dissipation. The 6N1P-EV needs more B+ from the power supply, and probably a change in the bias resistor. However, if it sounds better than the 6922, that's a good thing! I'm just saying it could sound even better.

The fact that 6N1P-EV sounds good in circuits that are designed for the 6922 speaks well for the 6N1P-EV, and is not a problem with your tester. How do you test the 6N1P with a tester? I don't know. What I do is to design a circuit to operate at optimized 6N1P-EV operating points, and test the tubes for balance, current, and mu, in the actual circuit.

twystd

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Follow Ups Full Thread

Topic - Tube Rolling a DRD Amp - SomeJoe 08:13:55 07/29/08 (16)

Hey Joe! - twystd 14:44:52 07/29/08 (0)

Tungsram E-80cc - BR 14:24:32 07/29/08 (0)

RE: Tube Rolling a DRD Amp - twystd 09:00:35 07/29/08 (13)

Black Plates vs. Gray Plates................... - Cut-Throat 16:33:57 07/31/08 (1)

RE: Black Plates vs. Gray Plates................... - twystd 19:42:48 07/31/08 (0)

How do you test these things? - Dave Pogue 05:15:55 07/30/08 (3)

For everyone who subs a 6N1P-EV for a 6922. - twystd 09:36:29 07/30/08 (2)

RE: For everyone who subs a 6N1P-EV for a 6922. - Dave Pogue 13:13:23 07/30/08 (1)

Don't get me wrong. - twystd 17:20:42 07/30/08 (0)

Is the EB designation the same as EV ?........nt - Cut-Throat 11:54:23 07/29/08 (4)

I found a partial explanation for those suffixes - 4season 20:57:55 07/30/08 (1)

Nice find, thanks! (nt) - twystd 12:40:58 07/31/08 (0)

Yes, but it's confusing. - twystd 14:38:16 07/29/08 (1)

I have some that are actually labeled - 6N1P-EB............... - Cut-Throat 14:58:49 07/29/08 (0)

RE: Tube Rolling a DRD Amp - SomeJoe 10:11:26 07/29/08 (1)

You're welcome. (nt) - twystd 13:23:09 07/29/08 (0)

Follow Ups

For everyone who subs a 6N1P-EV for a 6922. - twystd 09:36:29 07/30/08 (2)

RE: For everyone who subs a 6N1P-EV for a 6922. - Dave Pogue 13:13:23 07/30/08 (1)

Don't get me wrong. - twystd 17:20:42 07/30/08 (0)

For everyone who subs a 6N1P-EV for a 6922.

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