1. Check out the Western Electric 300B datasheet's various quiescent conditions:
Plate Voltage; Plate Current; Plate Load, RL; and Output Power @ 2nd Harmonic distortion dBc, and 3rd Harmonic distortion dBc.
Pick your favorite combination; there are lots of them.
By the way, -26dBc 2nd Harmonic is 5% distortion, and does not include the 3rd Harmonic dBc.
THD % is slightly larger, when it includes both the 2nd and the 3rd.
Consider a review of the Elrog ER300B.
"Elrog's ER300B is best described as a '300B compatible' vacuum tube. It deviates from the original Western Electric specifications".
Of course you get more power, it is a higher voltage tube . . .
But it is Not a 300B!
Yes, a more powerful tube has more output power at a given distortion level (like -26dBc 2nd Harmonic).
211, 845, GM70, WE 212E anyone?
Just my opinions (and a whole lot of others opinions too).
2. I could not easily find the specifications on the web. I do not read German, sorry.
I was interested in the specs of the Elrog ER300B:
Filament Voltage
Filament Current
Plate Dissipation Maximum
Plate Voltage; Plate Current; Plate Load, RL; and Output Power @ 2nd Harmonic distortion dBc, and 3rd Harmonic distortion dBc.
Pick your favorite combination; there are lots of them.
By the way, -26dBc 2nd Harmonic is 5% distortion, and does not include the 3rd Harmonic dBc.
THD % is slightly larger, when it includes both the 2nd and the 3rd.
Consider a review of the Elrog ER300B.
"Elrog's ER300B is best described as a '300B compatible' vacuum tube. It deviates from the original Western Electric specifications".
Of course you get more power, it is a higher voltage tube . . .
But it is Not a 300B!
Yes, a more powerful tube has more output power at a given distortion level (like -26dBc 2nd Harmonic).
211, 845, GM70, WE 212E anyone?
Just my opinions (and a whole lot of others opinions too).
2. I could not easily find the specifications on the web. I do not read German, sorry.
I was interested in the specs of the Elrog ER300B:
Filament Voltage
Filament Current
Plate Dissipation Maximum
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The ELROG 300B is not really a 300B. It has higher plate resistance and lower mutual conductance at 3.3 mA/V, pretty much as the 211 and 845. Indeed it looks more like a downsized 845 with lower plate resistance. And of course it has toriated tungsten filament. The specified max dissipation is 40W. I guess such limit is dictated by common sense as these tubes cannot rely on millions of tube made and used like in the past.....
The original WE datasheet does indicate a couple of working points that result in 14.6W and 17.8W but distortion is 5% and 10%, respectively and tube dissipation is 36W. Possibly original WE tubes can work at 36W with no issues. Surely not Russians and Chinese copies. For 3% THD and 32W plate dissipation the output power can be about 11-12W, depending on the quality of the tubes.
Some 300B copies cannot even take more than 25-27W dissipation. Mostly those with punched or mesh plates.
For 15W at 3% THD you need the uprated 300B's. Namely, the 300B XLS by KR or EML. The KR is rated at 70W max plate dissipation, the EML is guaranted to last a decent amount of hours (5K or more) at 55W. If want to give it a go with 5K transformer I suggest 560V plate voltage and 75mA anode current for about -120V bias. This is only 42W and tubes will last forever. You will need a hefty driver tough, much like those for the 845.....
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Cascode amplifiers:
Probably the highest number of Cascode circuits ever were in the RF amplifier of early TV sets.
Another very successful use of the Cascode circuit was the 30MHz IF amplifier in the US Navy's 10GHz surface search radars.
I love cascode amplifiers whenever they make sense.
Skunkie seems to have found one application that works well with a 300B;
and it is a simple design to build.
As far as I know, Skunkie never claimed it was the highest performance 300B amplifier ever.
If I were a Moderator, I would tell some of you to back off (Yosemite Sam)
All designs have tradeoffs.
The Original Tacoma Narrows Bridge is a bad example of tradeoffs: It went up, it came down.
I thought that diyAudio was a place to help people, and to have fun.
Probably the highest number of Cascode circuits ever were in the RF amplifier of early TV sets.
Another very successful use of the Cascode circuit was the 30MHz IF amplifier in the US Navy's 10GHz surface search radars.
I love cascode amplifiers whenever they make sense.
Skunkie seems to have found one application that works well with a 300B;
and it is a simple design to build.
As far as I know, Skunkie never claimed it was the highest performance 300B amplifier ever.
If I were a Moderator, I would tell some of you to back off (Yosemite Sam)
All designs have tradeoffs.
The Original Tacoma Narrows Bridge is a bad example of tradeoffs: It went up, it came down.
I thought that diyAudio was a place to help people, and to have fun.
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Thanks astouffer.
Please note the max output is specified at max anode dissipation (36W) with low primary Z load (2-3k); it's not a recommended operating.
The tube would not last long.
Please note the max output is specified at max anode dissipation (36W) with low primary Z load (2-3k); it's not a recommended operating.
The tube would not last long.
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euro21,
Thanks for posting that data sheet!
By the way, the Maximum power out from the 300B is with 450V Plate to Filament.
That is also the maximum quiescent plate to filament voltage.
So, it makes sense that a EL300B with a maximum quiescent plate to filament voltage of 600V, will probably have more output power than a WE300B.
Thanks for posting that data sheet!
By the way, the Maximum power out from the 300B is with 450V Plate to Filament.
That is also the maximum quiescent plate to filament voltage.
So, it makes sense that a EL300B with a maximum quiescent plate to filament voltage of 600V, will probably have more output power than a WE300B.
Do not forget one of the factors of output power:
A moderate cost output transformer that has primary DCR, and secondary DCR, which causes a 1dB insertion loss . . .
Then, 12.5 Watts signal power from a 300B plate to the primary, will cause only 10 Watts signal power from the secondary.
Everything is what it seems to be, until you find out it is different.
A moderate cost output transformer that has primary DCR, and secondary DCR, which causes a 1dB insertion loss . . .
Then, 12.5 Watts signal power from a 300B plate to the primary, will cause only 10 Watts signal power from the secondary.
Everything is what it seems to be, until you find out it is different.
In case somebody is interested, here is a simulation of circuit in the first post. Simulation shows 6W RMS just before clipping:
All caveats with simulations apply. Model used for 300B is the Ayumi one, DC voltages are quite close to the real circuit, but the 300B current is a bit higher than in the real circuit.
That's the common 20% loss you can use for quick output power guesstimates.
So the loadline would use 350v plate and -72v bias curve. Skunkie says it swings 140v p-p on the grid. So, the peak goes to 70v, 2v shy of the 0v curve. Perfect. That leaves ~100v on the plate @ 0v grid. The plate swing is @250v peak. Turn that into RMS and it's 177v RMS. Now you transform that by the TR of the tranny (25) and get 7v RMS and then you remove the 20% for loss. The estimated power is 5.7W RMS for an 8R load.
Only if you use 550-600V anode voltage. I guess, you might be able to get 12-13W at 3% THD with some 600V/60ma and 7.5-8K. At lower anode voltage the "standard" 300B is more efficient because it has higher gm and lower rp. I don't think Thomas was really after max plate efficiency. It's not his philosophy.
10W at 3% THD can be obtained at dissipation of about 30W. I have done it a few times moving in the range from 420V/70mA with 4.2K to 450V/65mA with 5K. If one can get modest 2nd harmonic cancellation between driver and 300B, THD of the amplifier can get down to 1-1.5% (because it's Class A1 with largely dominant 2nd harmonic). I have always used standard 300Bs. One pair were Cetron (re-branded WE) and the others strictly selected Chinese 300Bs like Billington Gold, Golden Dragon 4-300B and 4-300BLX. The very first was with the excellent Golden Dragon 4-300BLX with Titanium plate some 20 years ago....unfortunately it was discontinued after few years in production. The amplifier started out as a replica of the well-known Ciro Marzio Katelelo (which like the Skunkie was operating the 300B at 350V anode voltage for 8W) but ended up with Tango NC-20 interstage and 420V anode voltage. Yes, the NC-20 is/was expensive, more expensive than the output transformer, but it's not a boutique transformer. There is no other way for best performance with IT. Other similar IT's have been made (like Hashimoto, for example) and end-up pretty much at the same point (performance, cost etc.).
30W dissipation is absolutely fine for standard, well made 300B's, without fancy mesh or punched plate styles.....
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That is really too much. It might be acceptable for a very economical amp but what's the point of using cheap transformers with the 300B's? One thing is avoiding unnecessary costs but at the other end there are minimum requirements as well.
The EDCOR's insertion loss is rated at 0.5 dB max.
45,
0.5 dB insertion loss . . .
Which Edcor output transformer for the single ended 300B (or is it for a push pull 300B)?
Please list the Edcor Model number, and the following specifications:
Primary & secondary impedances; and the primary & secondary DCRs.
Thanks!
Sometimes the power that the 300B delivers to the output transformer is Under-Estimated.
That is because just using peak to peak volts does not always give the right answer when it comes to power.
Power is proportional to the Integral of the Positive alternation, plus the Integral of the Negative alternation.
One Integral is large, the other Integral is small.
(Those two Integrals are not equal . . . primarily because of 2nd harmonic distortion).
Does everybody own a True RMS DMM, Digital Scope, or capable software and either a sound card or digitizer?
No.
Then get one.
Are all 8 Ohm speakers 8 Ohm from 20Hz to 20kHz?
If not, the 2nd Harmonic cancellation from driver tube to 300B may not be working across the whole frequency range.
Just saying
0.5 dB insertion loss . . .
Which Edcor output transformer for the single ended 300B (or is it for a push pull 300B)?
Please list the Edcor Model number, and the following specifications:
Primary & secondary impedances; and the primary & secondary DCRs.
Thanks!
Sometimes the power that the 300B delivers to the output transformer is Under-Estimated.
That is because just using peak to peak volts does not always give the right answer when it comes to power.
Power is proportional to the Integral of the Positive alternation, plus the Integral of the Negative alternation.
One Integral is large, the other Integral is small.
(Those two Integrals are not equal . . . primarily because of 2nd harmonic distortion).
Does everybody own a True RMS DMM, Digital Scope, or capable software and either a sound card or digitizer?
No.
Then get one.
Are all 8 Ohm speakers 8 Ohm from 20Hz to 20kHz?
If not, the 2nd Harmonic cancellation from driver tube to 300B may not be working across the whole frequency range.
Just saying
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20to20,
You said "guesstimates".
Not me.
I actually measure Insertion Loss at 1kHz. Write down the number. Then . . .
For most of the transformers I have owned, the calculations from primary & secondary impedances, turns ratio, and primary and secondary DCRs: The calculated Insertion loss is in very close agreement to the measured Insertion loss.
Simulation, no.
Do the hard work!
Just my experience
Your Mileage May Vary
You said "guesstimates".
Not me.
I actually measure Insertion Loss at 1kHz. Write down the number. Then . . .
For most of the transformers I have owned, the calculations from primary & secondary impedances, turns ratio, and primary and secondary DCRs: The calculated Insertion loss is in very close agreement to the measured Insertion loss.
Simulation, no.
Do the hard work!
Just my experience
Your Mileage May Vary
https://edcorusa.com/collections/tu...-5k-ohms-single-ended-tube-output-transformer
Your comment about 2nd harmonic cancellation I have heard many times. And that my friend is just speculation!
Practice says that the cancellation works over the full audio band: somewhere more efficiently, somewhere a bit less because 2nd harmonic distortion is not just happening for a fixed load. I normally test at 100Hz, 1KHz and 10KHz with 5-to-8R. It's always there, a bit more or a bit less really doesn't make much difference: distortion is always lower than without. At best is a cancellation of 6-7 dB. That is enough because the amplifier has already low distortion without and going towards lower signal level there is less and less of it as both driver and power tube behave more linearly. The way I use it, its max (modest) effect happens when getting close to clipping. Just before clipping it's at its max so much so that 3rd harmonic can even become almost level (remember, we are talking of less than 3% THD here, not 5%, 10% or other silly numbers.....). How does that sound? It sounds more like an amp with grip, control rather than fluffy. It makes the full power more usable, IME. Forget soundcards and simulations...they will never tell how it sounds!
A lot of people have amplifiers where 2nd harmonic cancellation is happening but they are not aware....
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