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Old 7th November 2010, 04:47 AM   #41
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Originally Posted by Wavebourn View Post
If you don't afraid...
Let's just leave it for another day... btw, the curves look vaguely like the pentode curves instead of thestandard triode curves...
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Old 7th November 2010, 04:58 AM   #42
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Originally Posted by quikie22 View Post
Let's just leave it for another day... btw, the curves look vaguely like the pentode curves instead of thestandard triode curves...
Typical right-handed triode curves.

Here is the RCA classics, 6N7 (actually, Russian version 6Н7С):

Click the image to open in full size.
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Old 7th November 2010, 08:58 AM   #43
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Initially I built the amplifier with 811A triode.
After completing the design I also tested it with 807 and GU50 with hi-mu connection. Below is the schematic for the original 811A version.

Click the image to open in full size.

When GU50 is used, it is better to use one half (or both) of 6N6P triode instead of 6N1P. This is because the GU50 has lower input impedance (some 350 to 400 ohms for AC) than 811A and thus requires a little bit more driving power. The required driving voltage however is only some 10 Vrms for 15 W output.

I can also complete the schematic of GU50-version if this is interesting anybody.

Here is the image of the prototype (with 811A).

Click the image to open in full size.
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Old 7th November 2010, 09:14 AM   #44
45 is offline 45  Italy
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I think that hi-mu connection was meant for push-pull class B2 operation where you tie the grids together and connect them to ground (by means of an IT secondary, typically). The catode is also grounded. Basically it is a 0V bias connection with low quiescent current and high efficiency.

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Last edited by 45; 7th November 2010 at 09:27 AM.
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Old 7th November 2010, 11:37 AM   #45
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Originally Posted by artosalo View Post
Initially I built the amplifier with 811A triode.
After completing the design I also tested it with 807 and GU50 with hi-mu connection. Below is the schematic for the original 811A version.

Click the image to open in full size.

When GU50 is used, it is better to use one half (or both) of 6N6P triode instead of 6N1P. This is because the GU50 has lower input impedance (some 350 to 400 ohms for AC) than 811A and thus requires a little bit more driving power. The required driving voltage however is only some 10 Vrms for 15 W output.

I can also complete the schematic of GU50-version if this is interesting anybody.

Here is the image of the prototype (with 811A).

Click the image to open in full size.

This is really interesting. How would you say it sounds? Sound signature is typical SET?

What grid currents would you use for GU-50? Do you think half 6N6P is sufficient as the current for 6N6P is almost double of the 6N1P.
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Old 7th November 2010, 12:02 PM   #46
spswmsw is offline spswmsw  Ukraine
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Originally Posted by artosalo View Post

I can also complete the schematic of GU50-version if this is interesting anybody.
Yes, please, it will be very nice.
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Old 7th November 2010, 12:39 PM   #47
45 is offline 45  Italy
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Originally Posted by quikie22 View Post
What grid currents would you use for GU-50? Do you think half 6N6P is sufficient as the current for 6N6P is almost double of the 6N1P.

Quikie22 the 811A is a different device. Firstly it's a triode and one doesn't have choice for the connection. It has 10W grid power handling and quite less grid current than the GU50 whose G2 grid handling is 5W only and much less for G1. In fact the GU50 in that hi-mu triode connection has a maximum specified quiescent anode current of 30 mA only........
Secondly one can get up to 22W from a 811A at plate dissipation around 50W (600V/80-85 mA and bias around +18.5V). I don't think one can get double figures Pout from a properly biased GU50 and also (!!! ) looking for a reliable audio amplifier to listen to music......

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Last edited by 45; 7th November 2010 at 12:58 PM.
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Old 7th November 2010, 01:11 PM   #48
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Yes, please, it will be very nice.
Yes I second that spswmsw.
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Old 7th November 2010, 01:45 PM   #49
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This is really interesting. How would you say it sounds? Sound signature is typical SET?

What grid currents would you use for GU-50? Do you think half 6N6P is sufficient as the current for 6N6P is almost double of the 6N1P.
Unfortunately I am not anymore a "golden ear". My high frequency limit is around 12 kHz. But I think it sounded very good. One reason is maybe that since the output power capacity was sufficient (15W), the linearity was good and distortion low with typical listening level. In principle my evalution of all these three versions (811A, GU50 and 807) was mainly technical.

The dc-grid current (=bias) for GU50 was around 12 mA and bias voltage about + 7 volts.

One half of 6N6P is sufficient to drive and bias GU50. Then the anode current of 6N6P should be about 25 to 30 mA.

I have full test data at my "lab", but I am now spending the winter in Spain and I have only some drawings at my computer. However I can complete the circuit diagram.

It seems that I have the 811A test results in my computer, which I could publish, since those were very equal with GU50 test results.
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Old 7th November 2010, 03:32 PM   #50
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Originally Posted by artosalo View Post
Unfortunately I am not anymore a "golden ear". My high frequency limit is around 12 kHz. But I think it sounded very good. One reason is maybe that since the output power capacity was sufficient (15W), the linearity was good and distortion low with typical listening level. In principle my evalution of all these three versions (811A, GU50 and 807) was mainly technical.

The dc-grid current (=bias) for GU50 was around 12 mA and bias voltage about + 7 volts.

One half of 6N6P is sufficient to drive and bias GU50. Then the anode current of 6N6P should be about 25 to 30 mA.

I have full test data at my "lab", but I am now spending the winter in Spain and I have only some drawings at my computer. However I can complete the circuit diagram.

It seems that I have the 811A test results in my computer, which I could publish, since those were very equal with GU50 test results.

Good, please show us. This would be a good learning experience for me. This is the first time I have heard of a "right handed triode". Would be interesting to see how it is configured.
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