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Old 7th February 2009, 01:43 AM   #1
WRyan is offline WRyan  United States
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Default Running Single Ended 6V6 in Triode Mode

Hello,

Can anyone tell me how to run a single ended 6v6 in triode mode?

I would like to perform this modification on this circuit: http://www.kbapps.com/audio/schemati.../champ5f1.html

I built this amp and it sounds great, but now I want to see what else I can do with it.

Thanks so much!
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Old 7th February 2009, 03:13 AM   #2
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Default Re: Running Single Ended 6V6 in Triode Mode

Quote:
Originally posted by WRyan
Hello,

Can anyone tell me how to run a single ended 6v6 in triode mode?

I would like to perform this modification on this circuit: http://www.kbapps.com/audio/schemati.../champ5f1.html

I built this amp and it sounds great, but now I want to see what else I can do with it.

Thanks so much!
I would say fugeddaboudit. It's a guitar amp, not HiFi. I'd leave it alone if you like the sound. The specific "tone" of guitar amps is heavily dependent on its particular distortion. As such, trying to change it, especially by trying a more linear final, just might end up sounding too dull.

Furthermore, 6V6's don't do so well trioded as SE amps. The output power is quite low. You can go here: Frank's and check out some 6V6 specs. These include trioded plate characteristics. Run some loadlines and you'll see what I mean.
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Old 7th February 2009, 09:08 AM   #3
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Default 6V6 EL90 6AQ5 as output triode

Quote:
Originally #2 posted by Miles Prower


...

Furthermore, 6V6's don't do so well trioded as SE amps. The output power is quite low. You can go here: Frank's and check out some 6V6 specs. These include trioded plate characteristics. Run some loadlines and you'll see what I mean.
Hi Miles,
the 6V6 is an excellent triode. Efficiency is >25% and the EL90 = 6AQ5 (similar to 6V6) can handle high anode voltages since it is recommended as a vertical deflection output triode.

Kind regards,
Darius
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Old 7th February 2009, 09:25 AM   #4
45 is offline 45  Italy
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I agree with Miles Power.
The 6V6 is not very efficient when run in SE triode connection.
I have done it.
If you use typical 285-300V anode supply and 5K load, with that circuit, you will get 1.5-1.7W approx. (with reasonable distortion).

Cheers,
45
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Old 7th February 2009, 09:55 AM   #5
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The Champ OPT has a Ra of ca 8k. As we are talking about guitaramps it is no idea to discuss ideal operating point.

It is all about tone!

Strap screen to anode via a 100ohm resistor and play. If you like it, keep it. If you like both, add a switch, see attachment.
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Old 7th February 2009, 11:03 AM   #6
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Quote:
Originally posted by 45
I agree with Miles Power.
The 6V6 is not very efficient when run in SE triode connection.
I have done it.
If you use typical 285-300V anode supply and 5K load, with that circuit, you will get 1.5-1.7W approx. (with reasonable distortion).

Cheers,
45
???
How much bias current did you take?
What do you expect from a 45?

Cheers,
Darius
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Old 7th February 2009, 12:31 PM   #7
45 is offline 45  Italy
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Quote:
Originally posted by oldeurope


???
How much bias current did you take?
What do you expect from a 45?

Cheers,
Darius

At 300V/40 mA 5K load you get approx. 1.6W with 5% THD.

The 45 is not exceptionally efficient as well (because it has low Gm essentially) but it is much better than 6V6:the sonic perfomance is in another league, at low levels THD is much lower and the IMD is incomparably better, especially with filament DC supply.

So the 6V6 gives an anode efficiency of 1.6/12 = 13.3%!!

The 45 needs 250V/34 mA only for 1.6W at the same THD and so its efficiency is 18.8%.

The triode connected EL84 is much better than 6V6 as you get approx. 2W with less than 8W anode dissipation.

Cheers,
45
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Old 7th February 2009, 01:55 PM   #8
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Default Re: Re: Running Single Ended 6V6 in Triode Mode

Quote:
Originally posted by Miles Prower


I would say fugeddaboudit. It's a guitar amp, not HiFi. I'd leave it alone if you like the sound. The specific "tone" of guitar amps is heavily dependent on its particular distortion. As such, trying to change it, especially by trying a more linear final, just might end up sounding too dull.

Furthermore, 6V6's don't do so well trioded as SE amps. The output power is quite low. You can go here: Frank's and check out some 6V6 specs. These include trioded plate characteristics. Run some loadlines and you'll see what I mean.
I disagree almost completely. First off, the low power output allows the amp to be overdriven without it reaching ear-splitting volume levels.

Second, the reduced gain/changed gain structure will change the tone of the amp. Whether he likes the tone or not only he can decide. As well, the reduced gain will also reduce the amount of NFB, also changing the tone.

It's likely the amp will be "cleaner" in triode, and depending on playing style, etc., it can be very pleasing. I've installed "triode switches" on a number of Fenders, and the owners have been pleased in every case.

I agree with revintage - I'd put a switch in so I could have it either way, triode or pentode.
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Old 7th February 2009, 03:24 PM   #9
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Default @ #7

Quote:
Originally #7 posted by 45



At 300V/40 mA ...
Thanks, this is what I have expected, makes me sad.

Cheers,
Darius
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Old 7th February 2009, 05:36 PM   #10
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Oldeurope ,

You said "What do you expect from a 45?" .

What tube are you referring to ?



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