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Old 4th September 2012, 10:42 AM   #1
disco is offline disco  Netherlands
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Default 6H6pi curves available?

I'm looking for data on the russian 6H6pi, like curves. Are 6H6P and 6H6N faulty names for the same tube?

It must swing 150 to 180 volts in the grid of a 6C41C, SRPP seemed a good choice, not?

Click the image to open in full size.

Got one hooked up at 3mA but I guess this would be out of the linear region...

Sounds somewhat like the loudness switch is pressed
otoh ... this might come from the high impedance PSU as I measured >1V AC on the cathode.
Impressive bassnotes from the EV15B though

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Old 4th September 2012, 01:43 PM   #2
Bone is online now Bone  United Kingdom
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Check here - Russian 6N6p / 6H6pi :-)
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Old 4th September 2012, 04:39 PM   #3
disco is offline disco  Netherlands
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Thanks mate, I had the search engine in its highest gear for twenty minutes but missed this one. Calculation time
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Old 5th September 2012, 07:51 AM   #4
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I would suggest much higher currents for the 6N6P. I use them at around 20mA anode current and 4.4V bias voltage. In the lower half of the tube you could also use two green LEDís in series for bias (giving around 4.4V bias @ 20mA).
Sound quality can further be enhanced by bypassing the LEDís with HQ capacitors. I like tantalum capacitors very much in that position.

Peter
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Old 5th September 2012, 01:38 PM   #5
disco is offline disco  Netherlands
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Hi Peter,

Raising the current to 9mA did the 6H6pi good. I will investigate your advice but Vgk must be at least 7V as my pre has highish output voltage. The current situation:

Click the image to open in full size.

In the meantime I got data on the 6C41C and lowered the grid leak resistor (200K max) to 150K ohm. The SRPP likes it as distortion is noticeably lower. Optimizing it is new to me so I'm reading MerlinB's article. Good source.

I'm trying to determine the exact load for the SRPP.
Taken from the 'Basic Data Electrical Parameters' 6C41C is specified for input capacitance between 5 and 17pF and for mutual conductance anywhere between 12 and 26mA/V. What impedance will be parallel to the load resistor?
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Old 6th September 2012, 03:32 AM   #6
disco is offline disco  Netherlands
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Angry 6C41C properties

All (four) 6C41C power triodes I own measure south of this graphic. Is there a smarter method to obtain ra than inputting say 10Vrms into its grid and measuring voltagedrop over a test resistor in the cathode?

My actual operating point: Va-c= 298-74= 224V, Iq= 74V/750 ohm= 98mA.
The steepness of the green line in this graphic suggests a ra of 26V over 140mA= 186 ohm and a gm of 5.4mA/V. What can be made of Cmiller and how does it load our SRPP?

The whole thing of getting the numbers right depends of course on some trustworthy data and formulae but when it's whetfingering all over the place one could better use its floppies, or perhaps borrow an old HP 334A and study the manual

Click the image to open in full size.
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Old 6th September 2012, 08:16 AM   #7
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The 6C41C Tube

IRL performance!
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Old 6th September 2012, 03:49 PM   #8
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Yes, noticed that one. I've evened out the scales (purple):
Click the image to open in full size.
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Old 7th September 2012, 10:18 AM   #9
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Hi

in attach you can find a 6N6/6H6 curve by SOFIA

Walter
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File Type: bmp 6n6-B.BMP (37.6 KB, 100 views)
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Old 7th September 2012, 01:59 PM   #10
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Thanks Walter, seems I'm stuck then, with the available power supply voltage for the SRPP.

WRT SRPP driving miller capacitance (besides the grid leak resistor) it sees a falling impedance with frequency. The stage could be optimised for a 'worst case scenario' but the distortion of a not optimal tuned SRPP is already of a much smaller magnitude than that of the SE output stage.
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