That screen decoupling cap might be too large by two magnitudes, and it should relate to the cathode instead of ground.
Beste regars!
Beste regars!
I see it's the same as in the original Hohner schematics you posted in #11. Anyway, it isn't good engineering practice to relate a screen decoupling cap to ground if the cathode isn't grounded AC wise. In addition, do we really need 1 µF and a LF rolloff at 0.3 Hz?
The PCF200 wasn't the worst choice at this place. It's very high transconductance frame grid pentode allowed for high gain, hence considerable NFB.
Another question: Admittingly I don't completely get if 6P41S and EL508 are equivalent tubes. It so, it is fine. If not, where's the difference? There's no 6P41S datasheet at Frank Philipse's site.
Btw, German MI manufacturer Hohner, that was best known for their accordions, their harmonicas, and their Clavinet D6, of course, did astonishing things with P series TV tubes. There was, for instance, an Orgaphon amplifier that squeezed more than 40 watts out of a pair of PL84's!!
Btw, @ moderators' team: Shouldn't this thread be moved to the 'Those magnificent TV tubes' branch, hence made sticky?
Best regards!
The PCF200 wasn't the worst choice at this place. It's very high transconductance frame grid pentode allowed for high gain, hence considerable NFB.
Another question: Admittingly I don't completely get if 6P41S and EL508 are equivalent tubes. It so, it is fine. If not, where's the difference? There's no 6P41S datasheet at Frank Philipse's site.
Btw, German MI manufacturer Hohner, that was best known for their accordions, their harmonicas, and their Clavinet D6, of course, did astonishing things with P series TV tubes. There was, for instance, an Orgaphon amplifier that squeezed more than 40 watts out of a pair of PL84's!!
Btw, @ moderators' team: Shouldn't this thread be moved to the 'Those magnificent TV tubes' branch, hence made sticky?
Best regards!
Of course it doesn't need even 1 uF, but it was already soldered to the printed circuit board, and that's also the reason it's connected to ground because it was already like that and I didn't change anything.
...
I don’t think the EL508 and 6P41S are exactly the same tubes, but I’ve never had a brand new EL508 to compare them to in a test amp, or in detailed measurements.
A visual comparison from the outside (I have a few old PL508s) shows that the 6P41S has a different mechanical construction, has a much larger plate area and heating consumption. I think the 6P41S was much (relatively!?) later constructed so although it initially had the same purpose as the EL508, but believe the constructors had the EL506 in mind as it shares a base connection with it.
This is supported by the data provided by the manufacturer for the 6P41S for use in audio amplifiers as they exist for the EL506, and there is no such data for the EL508, or PL508.
...
I don’t think the EL508 and 6P41S are exactly the same tubes, but I’ve never had a brand new EL508 to compare them to in a test amp, or in detailed measurements.
A visual comparison from the outside (I have a few old PL508s) shows that the 6P41S has a different mechanical construction, has a much larger plate area and heating consumption. I think the 6P41S was much (relatively!?) later constructed so although it initially had the same purpose as the EL508, but believe the constructors had the EL506 in mind as it shares a base connection with it.
This is supported by the data provided by the manufacturer for the 6P41S for use in audio amplifiers as they exist for the EL506, and there is no such data for the EL508, or PL508.
Although the EL508/PL508 is a beam power tetrode, while the EL86/PL84/UL84 is a power pentode, the Va/Ia curves of the two look pretty similar at Vg2 = 200 V.
Until now I thought of the EL508/PL508 as a kind of EL86 which could be used at a much higher anode voltage.
EL508/PL508:
Va max = 400 V
Vg2 max = 275 V
EL86/PL84/UL84:
Va max = 250 V
Vg2 max = 250 V
Until now I thought of the EL508/PL508 as a kind of EL86 which could be used at a much higher anode voltage.
EL508/PL508:
Va max = 400 V
Vg2 max = 275 V
EL86/PL84/UL84:
Va max = 250 V
Vg2 max = 250 V
