Non of this two ! Both proposed schematics have few crucial mistakes .
Since you want or you already chose to have simple unbalanced input stage based on classic Mullard Amp topology than I want to suggest you to switch there for standard noval EF86 tube for low noise input gain stage , DC coupled to ECC 99 bootstrapped differencial driver stage ,ECC99 is just perfect tube for that driver stage , EF86 is OK tube but far cheaper than C3g tube to !
EF86 could be both pentode or triode connected , EF86 tube triode connected will afford just enough gain , but with maintaining of low output THD % in the same time .
Think that input gain stage with EF86 tube pseudotriode connected is the best solution for this Circlotron power Amp input stage, to have relative low gain & low THD% stage characteristic , but to maintain plenty of headroom for relative high input signals from your CD or SS PreAmp source ,and to hold Amp good sound timbre , since the first input gain stage mainly and usually determined the whole Amp sonic signature .
Than is good for second driver stage to be designed to have relative high voltage gain for sufficient driver capability for output Circlotron power stage ,formed from two EL34 tube triode strapped.
Your proposed input C3g tube is quit rare and expensive one ,think that is better to found her place in some of your exotic DIY phono preamp or similar unit , but if you insist on C3g than OK .
What do you think ?
Best Regards !
Since you want or you already chose to have simple unbalanced input stage based on classic Mullard Amp topology than I want to suggest you to switch there for standard noval EF86 tube for low noise input gain stage , DC coupled to ECC 99 bootstrapped differencial driver stage ,ECC99 is just perfect tube for that driver stage , EF86 is OK tube but far cheaper than C3g tube to !
EF86 could be both pentode or triode connected , EF86 tube triode connected will afford just enough gain , but with maintaining of low output THD % in the same time .
Think that input gain stage with EF86 tube pseudotriode connected is the best solution for this Circlotron power Amp input stage, to have relative low gain & low THD% stage characteristic , but to maintain plenty of headroom for relative high input signals from your CD or SS PreAmp source ,and to hold Amp good sound timbre , since the first input gain stage mainly and usually determined the whole Amp sonic signature .
Than is good for second driver stage to be designed to have relative high voltage gain for sufficient driver capability for output Circlotron power stage ,formed from two EL34 tube triode strapped.
Your proposed input C3g tube is quit rare and expensive one ,think that is better to found her place in some of your exotic DIY phono preamp or similar unit , but if you insist on C3g than OK .
What do you think ?
Best Regards !
i think we are very close to what I want to build
I have some C3g already
its a nice tube
but I don't mind saving it fore a later project
if I better use a different tube, then I'm ok with that too
tho I'm not 100% convinced about the EF86
but I'm open to anything
simple input stage design was mostly chosen because of the C3g
so if theres a better way, I'm all ears
I can use TWO ecc99 instead, if it makes sense
it still only involves two tubes sockets
Deal ! 
But first and before anything else we have duty to design good and reliable Amps PSU !
Good designed PSU is always the corner stone of good sounding Tube Power Amplifier .
Later I will post here one correct schematic for this Amp PSU .
Any another suggestion from anyone else from here will be welcome to !
But first and before anything else we have duty to design good and reliable Amps PSU !
Good designed PSU is always the corner stone of good sounding Tube Power Amplifier .
Later I will post here one correct schematic for this Amp PSU .
Any another suggestion from anyone else from here will be welcome to !
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Deal !
But first and before anything else we have duty to design good and reliable Amps PSU !
after all it still seems like a good day
That`s easy !
ecc81 at balanced input + ecc99 at differencial driver + 2 x EL34 at Circlotron power output = Good music sounding tube Amp to !
Anyway you decide !
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WOW !
Cool differencial tube circuit !!!
It`s shame that not could be implemented for direct drive of excelent sounding Circlotron output power stage , simply Circlotron output power stage due of his CF nature need there that bootstrapped ecc99 for driver stage .
But yes it is posibble to implement that cool differencial circuit for the input Amp gain stage , but to drive with him only grids of than nondifferencial connected ecc99 driver tube and to take in account one more small ecc81 tube on the Amp chassis .
But if you want to run Amp only with balanced signal sources single ecc81 on the input stage is just enough .
I always prefer simple Amp design , found that simple one is always far more musical than complicated one .
Best Regards !
Cool differencial tube circuit !!!
It`s shame that not could be implemented for direct drive of excelent sounding Circlotron output power stage , simply Circlotron output power stage due of his CF nature need there that bootstrapped ecc99 for driver stage .
But yes it is posibble to implement that cool differencial circuit for the input Amp gain stage , but to drive with him only grids of than nondifferencial connected ecc99 driver tube and to take in account one more small ecc81 tube on the Amp chassis .
But if you want to run Amp only with balanced signal sources single ecc81 on the input stage is just enough .
I always prefer simple Amp design , found that simple one is always far more musical than complicated one .
Best Regards !
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great
looking at 12BH7 I found this amp (attached)
is it a good tube ?
12BH7A-STR TAD Premium Selected (symmetrisch/balanced) - TAD Vorstufenröhren SELECTED
nice that TAD offers 'balanced matching'
they also suggest ecc81 as a good 'phase driver'
looking at 12BH7 I found this amp (attached)
is it a good tube ?
12BH7A-STR TAD Premium Selected (symmetrisch/balanced) - TAD Vorstufenröhren SELECTED
nice that TAD offers 'balanced matching'
they also suggest ecc81 as a good 'phase driver'
Attachments
The 12BH7 and 6CG7 are both good driver tubes, and are pretty much the same thing as a 6SN7 in a different package.
The ECC81 (12AT7) is nice because it gets good gain but does not have bandwidth problems like the 12AX7. You can put some current through it so it can be used as a driver tube too.
Here is one my idea and schematic for balanced input gain stage and driver stage , with full balanced signal input to input ecc81 tube , than DC connected to grids of bootstrapped differencial driver stage of ecc99 or 12bh7 tube .
Balanced corection negative feedback is conected to both cathodes of ecc81 input gain stage .
Of course that different value of pasive elements can be aplied to achieve different electrical and sonic parameters .
Best Regards !
Balanced corection negative feedback is conected to both cathodes of ecc81 input gain stage .
Of course that different value of pasive elements can be aplied to achieve different electrical and sonic parameters .
Best Regards !
Attachments
Well there is no general rules for small signal tubes type choice for this aplication
But yes miniature noval ecc81 placed at input gain stage in combination with noval ecc99 (12bh7 / 6cg7) for driver stage work fine .( ecc82 tube for input stage is OK to ).
Atmasphere have right ! 6sn7 tube is good pair for both input and driver stage ,than all Amps tube socket will be octal , or if you prefer many nice glowing octal tubes on the top plate on Amp chassis than four octal triode 6j5gt is OK to .
My few word about ``smooth`` and`` neutral`` tube Amp timbre :
OTL Amps sounds positive smooth but Not neutral ,god designed autotrafo coupled Circlotron Amp sounds prety close to that to .
`` neutral `` Amp sound I connect close with`` lifeless `` Amps sound music reproduction which usually we can hear from 99,99% of standard designed SEPP SS based Amps ,I think this negative sound effect apear since this SS Amps usually work with relative high aplied GNFB percent, to cure high open loop Amp distortion, there soundstage presentation is poor to .
Best Regards !
But yes miniature noval ecc81 placed at input gain stage in combination with noval ecc99 (12bh7 / 6cg7) for driver stage work fine .( ecc82 tube for input stage is OK to ).
Atmasphere have right ! 6sn7 tube is good pair for both input and driver stage ,than all Amps tube socket will be octal , or if you prefer many nice glowing octal tubes on the top plate on Amp chassis than four octal triode 6j5gt is OK to .
My few word about ``smooth`` and`` neutral`` tube Amp timbre :
OTL Amps sounds positive smooth but Not neutral ,god designed autotrafo coupled Circlotron Amp sounds prety close to that to .
`` neutral `` Amp sound I connect close with`` lifeless `` Amps sound music reproduction which usually we can hear from 99,99% of standard designed SEPP SS based Amps ,I think this negative sound effect apear since this SS Amps usually work with relative high aplied GNFB percent, to cure high open loop Amp distortion, there soundstage presentation is poor to .
Best Regards !
Open loop you are not going to get much over 12-15KHz out of a 12AX7- it is high impedance and so is affected by capacitance in the layout. To reproduce the audio passband without phase shift, you need bandwidth to 1/10th and 10X the cutoff frequencies. A 12AX7 won't make it to 100KHz or 200KHz but a 12AT7 will do it with with ease.
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