Thanks for doing the Sim.
My only question is why would you do it with an EL84?
A 6L6 would be at least close to Design center max.
An EL509/6KG6 seems to be within design center max.
An EL34 would be within design center.
What earthly reason would this be considered good engineering?
OK, it seems to not destroy tubes.
The transformers are almost certainly higher than normal Z.
What is the down side in using a EL34 or 6L6 in this app?
Slightly higher tube cost, and more heater power.
The advantage would be a tube that is running conservatively and an 8K or 10K transformer could be used.
As far as I can see, the design used an EL84 just for marketing purposes.
Doug
My only question is why would you do it with an EL84?
A 6L6 would be at least close to Design center max.
An EL509/6KG6 seems to be within design center max.
An EL34 would be within design center.
What earthly reason would this be considered good engineering?
OK, it seems to not destroy tubes.
The transformers are almost certainly higher than normal Z.
What is the down side in using a EL34 or 6L6 in this app?
Slightly higher tube cost, and more heater power.
The advantage would be a tube that is running conservatively and an 8K or 10K transformer could be used.
As far as I can see, the design used an EL84 just for marketing purposes.
Doug
I have built a load of EL84 Amps.
In Ultralinear Mode at B+ of 300V you get 10.5 Watts.
RMS Power, Peak Music Power etc. etc. are things which DO NOT exist and so you can claim whatever value you like, its still B.S..
Power (note NOT "RMS" Power just Power) is RMS Voltage times RMS Current. No other definitions, names, etc. exist in electronic engineering ONLY in sales brochures.
The Datasheet power output for pentode mode is 17 watts.
Claims of more than 17 watts are suspect. You MAY be able to get 20W by abusing the tube and running beyond its specifications.
The other way to get a bit more power out of a pair of EL84 is to use screen drive and that may be what is done in the RM10 mentioned above (although the posted link seems to suggest it is not). With Screen drive the output tubes are operated very close to Class B (idle current approximately 1/10th or even 1/20th of what is used in for UL or Pentode Mode). You can therefore run a little higher peak currents and still keep average dissipation withing limits. You MAY achieve 25W from a pair of EL84 using screen drive.
Cheers,
Ian
In Ultralinear Mode at B+ of 300V you get 10.5 Watts.
RMS Power, Peak Music Power etc. etc. are things which DO NOT exist and so you can claim whatever value you like, its still B.S..
Power (note NOT "RMS" Power just Power) is RMS Voltage times RMS Current. No other definitions, names, etc. exist in electronic engineering ONLY in sales brochures.
The Datasheet power output for pentode mode is 17 watts.
Claims of more than 17 watts are suspect. You MAY be able to get 20W by abusing the tube and running beyond its specifications.
The other way to get a bit more power out of a pair of EL84 is to use screen drive and that may be what is done in the RM10 mentioned above (although the posted link seems to suggest it is not). With Screen drive the output tubes are operated very close to Class B (idle current approximately 1/10th or even 1/20th of what is used in for UL or Pentode Mode). You can therefore run a little higher peak currents and still keep average dissipation withing limits. You MAY achieve 25W from a pair of EL84 using screen drive.
Cheers,
Ian
I find this all very difficult to believe - I have a bunch of old PP EL84/6BQ5/7189A based amplifiers around here, and none of them are happy with modern 6BQ5 or even necessarily the more rugged 6P14P-EV Russian equivalent to the 7189A. None of these run over 400V on the plates, and they are not reliable with modern 6BQ5..
I can't imagine the clearances in any 6BQ5 are adequate for operation at 700V.
Without seeing a schematic this is all conjecture, but there was nothing unusual in the photographs that made me believe this is anything other than a very generic interpretation of the classic 6BQ5 PP amplifier. Voltage doubler, rc filtered supply, pentode connection, single tube cathodyne phase splitter with voltage amplifier, (from appearances) and very cheap parts (!) Without someone confirming the B+ voltages present in this amplifier it's just a wild guess. And what about those sockets? Really think they can handle 1.3KV of B+ plus audio.. I don't...
I remember liking one of his relatively conventional EL34 amplifiers about 20 yrs ago, but never got to look inside it. Hard to know if it met all of its performance claims, it certainly did not outperform other similar EL34 amplifiers of the time if recollection serves.
The designer has been controversial since I was almost a kid, and these sorts of claims without some transparency are the reason why. I'd love to see an AP plot of power output vs a reasonable fixed value of thd for the entire audio frequency range..
Just my opinion of course.
I can't imagine the clearances in any 6BQ5 are adequate for operation at 700V.
Without seeing a schematic this is all conjecture, but there was nothing unusual in the photographs that made me believe this is anything other than a very generic interpretation of the classic 6BQ5 PP amplifier. Voltage doubler, rc filtered supply, pentode connection, single tube cathodyne phase splitter with voltage amplifier, (from appearances) and very cheap parts (!) Without someone confirming the B+ voltages present in this amplifier it's just a wild guess. And what about those sockets? Really think they can handle 1.3KV of B+ plus audio.. I don't...
I remember liking one of his relatively conventional EL34 amplifiers about 20 yrs ago, but never got to look inside it. Hard to know if it met all of its performance claims, it certainly did not outperform other similar EL34 amplifiers of the time if recollection serves.
The designer has been controversial since I was almost a kid, and these sorts of claims without some transparency are the reason why. I'd love to see an AP plot of power output vs a reasonable fixed value of thd for the entire audio frequency range..
Just my opinion of course.
The screen resistors for each channel are 2.2K (from pix in the Six Moons review) so assuming a nominal of 10mA per screen (about the max before meltdown) we can determine that the screens are about 45V below the plates which is usual territory for this tube. B+ is very unlikely to be over 400V, and I would guess more like 370 - 380V. Someone claimed the screens were at 350V so given the above conjectures it seems possible that B+ is really in the vicinity of 390V..
Note also that the screen filter caps are single IC brand types in a style not available above 450V/500V IME - these would probably not survive a 700V surge during warm up.
More reasons why I can't believe the claims made for this amplifier.
Just my opinion of course...
Note also that the screen filter caps are single IC brand types in a style not available above 450V/500V IME - these would probably not survive a 700V surge during warm up.
More reasons why I can't believe the claims made for this amplifier.
Just my opinion of course...
Music Reference posted an address behind a link that says, "Please feel free to contact us for more information about the RM-10."
info@ramlabs-musicreference.com
No use idly speculating - I'm sure the designer will answer your questions.
-d
info@ramlabs-musicreference.com
No use idly speculating - I'm sure the designer will answer your questions.
-d
30W EL84 PP good article
http://lundahl.se/pdfs/claus_byrith/amplifier_30wpp.pdf
http://lundahl.se/pdfs/claus_byrith/appendix_cb.pdf
Covers most of the original questions.
/sreten.
http://lundahl.se/pdfs/claus_byrith/amplifier_30wpp.pdf
http://lundahl.se/pdfs/claus_byrith/appendix_cb.pdf
Covers most of the original questions.
/sreten.
I felt like resurrecting this old thread since I found another thread with Roger explaining how he gets 35 watts from two EL84's.
Re: Power ratings... - Roger A. Modjeski - Tubes Asylum
Apparently he IS using 700V on the plates and 350V at the screen. Idle current is 30mA and load is 14.2k plate to plate. Says the tubes last >5000 hours.
Thoughts?
Re: Power ratings... - Roger A. Modjeski - Tubes Asylum
Apparently he IS using 700V on the plates and 350V at the screen. Idle current is 30mA and load is 14.2k plate to plate. Says the tubes last >5000 hours.
Thoughts?
I had a SCOTT 222C stereo amplifier that I fully restored and sold last year :
The measured power output is 20W RMS on 8 ohms resistive load with an OPT CT voltage of 415VDC. The tubes are EL84/6BQ5 working in fixed bias / pentode operation.
I would not expect to go further in power output with such tubes for reasonable life duration and foolproof operation. But that's my opinion...
A+!
The measured power output is 20W RMS on 8 ohms resistive load with an OPT CT voltage of 415VDC. The tubes are EL84/6BQ5 working in fixed bias / pentode operation.
I would not expect to go further in power output with such tubes for reasonable life duration and foolproof operation. But that's my opinion...
A+!
Tubelectron,
Nice Scott, I have a 299A that I use and love. The output iron in your 222C are much bigger then the ones in mine. My plate voltage is over 400V and @ 1kHz I was getting similar power out. I have some really nice Reflektor 6P14P-EV valves in it now and everything is great. I don't trust modern production 6BQ5's in this amp..........even the NOS valves were not meant to be in those amps! The 6BQ5 is rated for 300V plate and 300V screen. The 7189 has an uprated max plate voltage of 440V and screen 330V. My screen voltage is very close to max rating in the Scott.
SY,
I will have a look at your Red Light District amp. 500V on the plates seems much more reasonable, 25 watts is nothing to sneeze at from two 6BQ5's. I wonder if Roger is using the EL84M from Sovtek. Have you tried any of these valves in your Red Light District amp? I wanted to compare the EL84M to the 7189 but can't find a datasheet. I have been going off the 6P14P datasheets being told they are the same tube.
Nice Scott, I have a 299A that I use and love. The output iron in your 222C are much bigger then the ones in mine. My plate voltage is over 400V and @ 1kHz I was getting similar power out. I have some really nice Reflektor 6P14P-EV valves in it now and everything is great. I don't trust modern production 6BQ5's in this amp..........even the NOS valves were not meant to be in those amps! The 6BQ5 is rated for 300V plate and 300V screen. The 7189 has an uprated max plate voltage of 440V and screen 330V. My screen voltage is very close to max rating in the Scott.
SY,
I will have a look at your Red Light District amp. 500V on the plates seems much more reasonable, 25 watts is nothing to sneeze at from two 6BQ5's. I wonder if Roger is using the EL84M from Sovtek. Have you tried any of these valves in your Red Light District amp? I wanted to compare the EL84M to the 7189 but can't find a datasheet. I have been going off the 6P14P datasheets being told they are the same tube.
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