Ron’s New System
- Thread starter Ron Resnick
- Start date
"
This amplifier without modifications will allow to use the GM70 and the 813 (FU-13) output tubes.
The 813 is a general-purpose transmitting beam power tube with thoriated-tungsten filament with a maximum plate dissipation of 125 watts.
It is a very linear tube in triode connection with the same amplification factor of the GM70 and a reduced internal resistance so with the same 10Kohm output transformer it is possible to get a better damping factor.
The GM70 and the 813 (FU-13) in a direct comparison with the 845 have the same sound quality but these tubes have the great advantage of a higher voltage gain to allow an simple driver stage.
The GM70 and the 813 with graphite plate are not very good so you should use only copper plate for the GM70 and metal plate for the 813 (FU-13 Shuguang).
I have used a 10Kohm output transformers to get a good damping factor (Rout less than 1.6ohm) and an anode voltage of 1100V to get more than 20w in a pure A1 class operation.
In these last years many DIY are designing amplifiers with transmitter tubes working in A2 class operation.
I never will create an amplifier with these tubes because there are no benefits to use these, only the cost is lower but there is no impact on the total budget because the transformers are the main cost of a vacuum tube amplifier.
Tubes like the 805, 808 and 304TL also if used with strong drivers are less linear of 845, GM70 and 813 so it is necessary use feedback."
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This amplifier without modifications will allow to use the GM70 and the 813 (FU-13) output tubes.
The 813 is a general-purpose transmitting beam power tube with thoriated-tungsten filament with a maximum plate dissipation of 125 watts.
It is a very linear tube in triode connection with the same amplification factor of the GM70 and a reduced internal resistance so with the same 10Kohm output transformer it is possible to get a better damping factor.
The GM70 and the 813 (FU-13) in a direct comparison with the 845 have the same sound quality but these tubes have the great advantage of a higher voltage gain to allow an simple driver stage.
The GM70 and the 813 with graphite plate are not very good so you should use only copper plate for the GM70 and metal plate for the 813 (FU-13 Shuguang).
I have used a 10Kohm output transformers to get a good damping factor (Rout less than 1.6ohm) and an anode voltage of 1100V to get more than 20w in a pure A1 class operation.
In these last years many DIY are designing amplifiers with transmitter tubes working in A2 class operation.
I never will create an amplifier with these tubes because there are no benefits to use these, only the cost is lower but there is no impact on the total budget because the transformers are the main cost of a vacuum tube amplifier.
Tubes like the 805, 808 and 304TL also if used with strong drivers are less linear of 845, GM70 and 813 so it is necessary use feedback."
813 / GM70 amplifier with Bartolucci transformers
Pick your poison and let your ears be your guide. There are fans of the A2 models, linearities aside.
Most interesting @cjfrbw … I am a big fan of Bartolucci output transformers .
A couple of observations if I may , The Chinese FU-13 is an ok more recent manufactured 813 however it is considerably less ‘Musical’ where fidelity of the amplified signal is concerned imho … Early RCA production rectangular copper plate (If you can find them) are very nice however can sound a tad ‘brittle ‘ especially if heavily pre used as they tend to strip quickly in transmitter duties but NOS they are nice … Produced in their many thousands the Various American manufacture ‘Oval Plate ‘ 813’s are also fine sounding valves however … where amplified audio reproduction is concerned Philips manufactured angular plate and Mullard re-brand angular plate 813’s are concerned , these are by some margin the finest sounding 813’s where optimal audio fidelity is the objective … imho.
A couple of observations if I may , The Chinese FU-13 is an ok more recent manufactured 813 however it is considerably less ‘Musical’ where fidelity of the amplified signal is concerned imho … Early RCA production rectangular copper plate (If you can find them) are very nice however can sound a tad ‘brittle ‘ especially if heavily pre used as they tend to strip quickly in transmitter duties but NOS they are nice … Produced in their many thousands the Various American manufacture ‘Oval Plate ‘ 813’s are also fine sounding valves however … where amplified audio reproduction is concerned Philips manufactured angular plate and Mullard re-brand angular plate 813’s are concerned , these are by some margin the finest sounding 813’s where optimal audio fidelity is the objective … imho.
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Graphite GM70s sound good. Copper plate ones sounded weak in my amp and not worth the trade offs ."
This amplifier without modifications will allow to use the GM70 and the 813 (FU-13) output tubes.
The 813 is a general-purpose transmitting beam power tube with thoriated-tungsten filament with a maximum plate dissipation of 125 watts.
It is a very linear tube in triode connection with the same amplification factor of the GM70 and a reduced internal resistance so with the same 10Kohm output transformer it is possible to get a better damping factor.
The GM70 and the 813 (FU-13) in a direct comparison with the 845 have the same sound quality but these tubes have the great advantage of a higher voltage gain to allow an simple driver stage.
The GM70 and the 813 with graphite plate are not very good so you should use only copper plate for the GM70 and metal plate for the 813 (FU-13 Shuguang).
I have used a 10Kohm output transformers to get a good damping factor (Rout less than 1.6ohm) and an anode voltage of 1100V to get more than 20w in a pure A1 class operation.
In these last years many DIY are designing amplifiers with transmitter tubes working in A2 class operation.
I never will create an amplifier with these tubes because there are no benefits to use these, only the cost is lower but there is no impact on the total budget because the transformers are the main cost of a vacuum tube amplifier.
Tubes like the 805, 808 and 304TL also if used with strong drivers are less linear of 845, GM70 and 813 so it is necessary use feedback."
View attachment 117783813 / GM70 amplifier with Bartolucci transformers
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Happy Saturday, folks!
I've been focusing on JA200s with EL34s. But I should be thinking about the intermediate step first, the JA120. I do believe that fewer output tubes is better (all else being equal).
JA100 (four output tubes)is designed specifically around KT90. JA100 has proven that 80 or 90 Jadis watts work on the panels. But the unique circuit in JA100 with EL84 drivers I think drives the KT90s relatively harder than other Jadis amplifiers drive EL34s or KT88s.
JA120 (6 output tubes) is designed specifically around KT120 and specs output at 100 watts.
How many watts output should I expect from using EL34s in the JA120?
I've been focusing on JA200s with EL34s. But I should be thinking about the intermediate step first, the JA120. I do believe that fewer output tubes is better (all else being equal).
JA100 (four output tubes)is designed specifically around KT90. JA100 has proven that 80 or 90 Jadis watts work on the panels. But the unique circuit in JA100 with EL84 drivers I think drives the KT90s relatively harder than other Jadis amplifiers drive EL34s or KT88s.
JA120 (6 output tubes) is designed specifically around KT120 and specs output at 100 watts.
How many watts output should I expect from using EL34s in the JA120?
Ron hopefully the EI KT90s will kick the JA 100s up a notch. I know you are curious about the sound of EL34 but I agree with some of the other posters that your next amplifier venture should be a big SET like the Kronzilla. If you can’t be happy with what you have already which is spectacular. I can’t even imagine how good your system must sound!
Comes a time when you settle down……..
Comes a time when you settle down……..
Why? Kronzilla is a reverse hybrid.
The "weightiness" in the upper bass to lower midrange of the Jadis is the Jadis' raison d'être. I definitely do not want to give this up.
So the question is can retain the "weightiness" in the upper bass to lower midrange of the Jadis and also pick up "midrange magic" and purity from an SET/PSET (without losing the Jadis weightiness)?
This is not at all a frivolous question in that just because a tube amp is SET or PSET does not mean that it is not going to be more linear and more neutral in the upper bass/lower midrange than Jadis. (An SET or PSET might very well be more linear and more neutral (less full, weighty, rich and warm) in the upper bass/lower midrange than Jadis.)
I don't know what this is about. When did I say I'm not happy? I could fold my cards and just stay with JA100s.
By WBF standards being curious about trying two or three different amplifiers doesn't qualify me even for junior varsity box-swapping.
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I am looking forward to the Ei KT90s, thanks to you! I also have sets of Mullards for the input and driver positions.
Are we to take it that you have managed to source some tested type II or even better type III Ei’s Ron .
I have Mullard XF2, original KT77 and the reissue now to compare, a pair. I will do it in am amp that uses it as driver, to start with.
KR has a weightiness that is missing in a lot of amps…I think it is one of their key attractions.
Quite likely In no small part a product of the Hybrid input stage, together with a quality power supply.
It's a lost cause, Brad.
Ron wants what Ron wants.
Except Don tells him what to want.
Ron's preferences don't really align with KR Audio amps. They are much more toward the SS end of the spectrum like his VTLs. (I actually quite like them, just not relying on a single company for tubes).