Without some form of negative feedback, both the 6L6G and EL34 will have a damping factor less than 1. And the distortion will be high at 10 Watts, unless (even if) you use negative feedback.
You may need to use a 6L6GC instead of a 6L6G, or use an EL34 to get 10 Watts. Plate dissipation of the 6L6G is 19 Watts, 6L6GC is 30 Watts, and EL34 is 25 Watts. You will not get 50% efficiency out of a single ended amp. (you will really be pushing it to get near to 10 Watts single ended with only one of those tubes). You need to go parallel single ended, or get less than 10 Watts.
Otherwise, you need to go with Push Pull (and that is two output tubes per channel; so if you want single ended with those tubes, go to a parallel single ended circuit).
Single Ended 6L6G or EL34 without negative feedback:
The output impedance of the 8 Ohm tap will be higher than 8 Ohms. 4 Ohm tap impedance > 4 Ohms, etc. The amplifier will not damp the Woofer.
And the frequency response of the amp output will be according to the varying impedance of the speaker versus different frequencies.
Even with an 8 Ohm resistor on the 8 Ohm tap, the amp frequency response will be dependent on: the output transformer inductance the output transformer distributed capacitance the output transformer leakage reactance.
You will need some form of negative feedback: Global including the output and driver stages Schade feedback 16 Ohm output tap to the 6L6G / EL34 cathode (make sure the phase is correct so that it is negative feedback, not positive feedback) Ultra Linear (may need to go with 50%, 60%, or 70% UL tap). A primary 40% UL connected backwards gives 60% (but reverses phase at the output). Triode wiring of the beam power tube / pentode tube
Trying all those circuits, and asking how the sound is compared to a 300B that may not need or have negative feedback is quite a task. And of course the sound is dependent on how well each of those negative feedback designs are carried out, and how good the output transformer is. Beam power tubes, pentodes, and real triodes need good output transformers.
You may need to use a 6L6GC instead of a 6L6G, or use an EL34 to get 10 Watts. Plate dissipation of the 6L6G is 19 Watts, 6L6GC is 30 Watts, and EL34 is 25 Watts. You will not get 50% efficiency out of a single ended amp. (you will really be pushing it to get near to 10 Watts single ended with only one of those tubes). You need to go parallel single ended, or get less than 10 Watts.
Otherwise, you need to go with Push Pull (and that is two output tubes per channel; so if you want single ended with those tubes, go to a parallel single ended circuit).
Single Ended 6L6G or EL34 without negative feedback:
The output impedance of the 8 Ohm tap will be higher than 8 Ohms. 4 Ohm tap impedance > 4 Ohms, etc. The amplifier will not damp the Woofer.
And the frequency response of the amp output will be according to the varying impedance of the speaker versus different frequencies.
Even with an 8 Ohm resistor on the 8 Ohm tap, the amp frequency response will be dependent on: the output transformer inductance the output transformer distributed capacitance the output transformer leakage reactance.
You will need some form of negative feedback: Global including the output and driver stages Schade feedback 16 Ohm output tap to the 6L6G / EL34 cathode (make sure the phase is correct so that it is negative feedback, not positive feedback) Ultra Linear (may need to go with 50%, 60%, or 70% UL tap). A primary 40% UL connected backwards gives 60% (but reverses phase at the output). Triode wiring of the beam power tube / pentode tube
Trying all those circuits, and asking how the sound is compared to a 300B that may not need or have negative feedback is quite a task. And of course the sound is dependent on how well each of those negative feedback designs are carried out, and how good the output transformer is. Beam power tubes, pentodes, and real triodes need good output transformers.
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Using EL34, You will have no more 4-5 W clear sound. 10 W is not serious for HiEnd, and sound will be sharp and distorted /EL34, 6L6 are, IMO, for guitar amps/. Better choice is 300B, that will give You real 6-7 W with clear, warm sound and deep and detail sounding. /using FB will press the scene of sound/.
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Do you want to spend hundreds of dollars for short lived 300B?
KT88/6550 wired as triodes are excellent single ended
The kt88/6550 have similar plate impedance to a 300b, so just as good damping factor. More power than 300B's. Easier to drive. warm sound and deep and detail sounding. is a matter of opinion Better to put the money saved using 6550 instead of 300B into better output Transformers
KT88/6550 wired as triodes are excellent single ended
The kt88/6550 have similar plate impedance to a 300b, so just as good damping factor. More power than 300B's. Easier to drive. warm sound and deep and detail sounding. is a matter of opinion Better to put the money saved using 6550 instead of 300B into better output Transformers
10 watts, I might suggest an EL84 push-pull, but I get that's not everyone's cup of tea.
As for SE, I second the suggestion for the KT88. A 300B is going to be a very expensive 8 watts. I haven't heard one so I can't comment on their performance. I have heard a P-P EL84 amp (similar to a Dyna ST35) that made 15 very, very sweet watts. I'd be inclined to go in that direction.
If you're set on SE, I'd either do parallel 6L6GCs or a KT88. Anything run in pentode or tetrode mode will need negative feedback to get a reasonable damping factor. No need to fear this. Lots of great amps use negative feedback to lower distortion and flatten out the frequency response.
As for SE, I second the suggestion for the KT88. A 300B is going to be a very expensive 8 watts. I haven't heard one so I can't comment on their performance. I have heard a P-P EL84 amp (similar to a Dyna ST35) that made 15 very, very sweet watts. I'd be inclined to go in that direction.
If you're set on SE, I'd either do parallel 6L6GCs or a KT88. Anything run in pentode or tetrode mode will need negative feedback to get a reasonable damping factor. No need to fear this. Lots of great amps use negative feedback to lower distortion and flatten out the frequency response.
300B unnecessarily expensive, or rather, they are artificially inflated demand. If you want to use direct-glow radiators, a good solution is the 811A, as well as the Russian and Chinese counterparts. 811 is a feature, they are the right characteristics and require a thoughtful driver, and there are also a lot of ready-made circuits for them.
GUNFU
"300B unnecessarily expensive, or rather, they are artificially inflated demand. If you want to use direct-glow radiators, a good solution is the 811A, as well as the Russian and Chinese counterparts. 811 is a feature, they are the right characteristics and require a thoughtful driver, and there are also a lot of ready-made circuits for them."
I have made many Push pull 811a amps 100 watts at 600 volts 40 watts class A. can be used down to 450v 2k-5 k transformer sound wonderful, but you need some feedback. Or altec/515 or JBL speakers Just my preference but did not like single ended sound with 811A
Have circuits.
"300B unnecessarily expensive, or rather, they are artificially inflated demand. If you want to use direct-glow radiators, a good solution is the 811A, as well as the Russian and Chinese counterparts. 811 is a feature, they are the right characteristics and require a thoughtful driver, and there are also a lot of ready-made circuits for them."
I have made many Push pull 811a amps 100 watts at 600 volts 40 watts class A. can be used down to 450v 2k-5 k transformer sound wonderful, but you need some feedback. Or altec/515 or JBL speakers Just my preference but did not like single ended sound with 811A
Have circuits.
I don't necessarily agree with you. Many awesome amps have been built around the 6L6GC, EL34, KT88 etc.
The design of the amplifier has a bigger impact than the individual tubes used. Beyond that, I've seen plenty of 300B amps using poor designs and $40 output transformers.
I'm still going to recommend a PP EL84. As for SE, the 811 looks like a good choice. Parallel 6L6GC is an excellent choice as well... careful about oscillation though. I've found that parallel 6L6s have a nasty habit of oscillating at HF frequencies. They do make nice transmitting tubes after all.
An externally hosted image should be here but it was not working when we last tested it.
GOTHAM PFB-150WA Power Amplifier YouTube
One of the best studio amplifiers for cutting master discs of varnish. Where is the cheap sound here? Yes, feedback is necessary, but unlike the 300B on the 811A, you can tune the optimal internal resistance with minimum distortion, analogy with the UL D.Hafler circuit or as in the partial feedback circuit, telefunken V69 and neumann LV60.
And now show me an example of using 300B not in movie theaters, but in recording studios. )))
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I have built lots of these record cutting amplifiers Leaving out the.record cutting audio stages.
The sound is wonderful can drive any speakers; you would never use 6550/KT88 compared to the 811A GOTHAM PFB-150WA Power .Recently I built one with a Toriody output transformer
https://www.diyaudio.com/forums/tubes-valves/333839-el34-6l6g-post5696164.html
The sound is wonderful can drive any speakers; you would never use 6550/KT88 compared to the 811A GOTHAM PFB-150WA Power .Recently I built one with a Toriody output transformer
https://www.diyaudio.com/forums/tubes-valves/333839-el34-6l6g-post5696164.html
I have built lots of these record cutting amplifiers Leaving out the.record cutting audio stages.
The sound is wonderful can drive any speakers; you would never use 6550/KT88 compared to the 811A GOTHAM PFB-150WA Power .Recently I built one with a Toriody output transformer
Our company can manufacture you an output toroidal transformer not only from silicon steel but also on amorphous alloy.
Moreover, we can produce exclusively for your requirements, and without the need for switching versatility for different tubes in this case, as in that original transformer General Radio 942-A http://www.ietlabs.com/pdf/Manuals/GR/942-A%20Output%20Transformer.pdf
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santitruco,
It seems there are no end to suggestions. Most or all of them are really good ideas.
But back to your original post, what do you want most?
Low distortion? Single Ended? 10 Watts? 6L6G or EL34? Willing to use a higher wattage tube, or to parallel two of the above tubes to get the power with SE? Less than 10 Watts would be OK? Push Pull with 6L6G or EL34; or with other tubes, EL84, or etc.?
Parallel SE is OK when designed and implemented properly. I was one of the authors of Parallel Tubes Effects in Glass Audio. We made 600 measurements, had 3 listening Venues (double blindfold listening tests), Math proofs, and more.
It seems there are no end to suggestions. Most or all of them are really good ideas.
But back to your original post, what do you want most?
Low distortion? Single Ended? 10 Watts? 6L6G or EL34? Willing to use a higher wattage tube, or to parallel two of the above tubes to get the power with SE? Less than 10 Watts would be OK? Push Pull with 6L6G or EL34; or with other tubes, EL84, or etc.?
Parallel SE is OK when designed and implemented properly. I was one of the authors of Parallel Tubes Effects in Glass Audio. We made 600 measurements, had 3 listening Venues (double blindfold listening tests), Math proofs, and more.
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Quite some bold statements, aren't they? I'm sure you want to substantiate them
.Best regards!
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