I wanted to get a taste of Andrea Chiuffolis Amplifier End but the Interstage Transformer is a bit on the pricey site for a mear test.
He uses the LL1671 in Alt Q configuration parallelling the four primaries and putting the secondaries in series.
Lundahl ommits so much relevant data that I as a novice can not find a substitute.
In my application I use the amp only above 100hz which should make it easier to find a cheaper substitute I think.
Any help is greatly appreciated.
Klaus
He uses the LL1671 in Alt Q configuration parallelling the four primaries and putting the secondaries in series.
Lundahl ommits so much relevant data that I as a novice can not find a substitute.
In my application I use the amp only above 100hz which should make it easier to find a cheaper substitute I think.
Any help is greatly appreciated.
Klaus
I built his 300B amp with all Lundahl transformers in it and it is the best sounding amp I have ever heard. ( yes I am a little biased but its damn good). I would say save up your money and buy the lundahls. I attached the schematic of mine and while it was not cheap it is fantastic. esp with the changes I made to it.
Yes but how to find the right one with such little information.
There must be Somebody who can deduct the needed values from the Lundahl Datasheet.
Leave yourself some room for potential disappointment. An audio transformer, especially interstage transformer, will offer a great variety of frequency performances vs section wiring. Lundahl have offered the wiring way, but no frequency response data.
Putting myself into customer's shoes, I'd feel more comfortable with available data for each wiring option.
In a perfect world, if an interstage transformer is to be built for multiconfigurational purposes, it should be optimized with such construction in mind.
Putting myself into customer's shoes, I'd feel more comfortable with available data for each wiring option.
In a perfect world, if an interstage transformer is to be built for multiconfigurational purposes, it should be optimized with such construction in mind.
I don't even need four primary windings.
Andrea uses the primaries in parallel fashion.
All that is needed is a former for about 2k impedance source between 40 to 50H and a 4:1 ratio with center tapped secondaries.
I just don't know where to find it.
Andrea uses the primaries in parallel fashion.
All that is needed is a former for about 2k impedance source between 40 to 50H and a 4:1 ratio with center tapped secondaries.
I just don't know where to find it.
Thanks,
I will never understand how 10k to 600ohm
can be a four times ratio, but never the less this was exactly what I wanted to know.
Klaus
I will never understand how 10k to 600ohm
can be a four times ratio, but never the less this was exactly what I wanted to know.
Klaus
Another noob question or better two:
Is the ma rating concerning the primaries or the secondaries?
For testing purposes can I parallel two separate formers to meet the ma rating?
Is the ma rating concerning the primaries or the secondaries?
For testing purposes can I parallel two separate formers to meet the ma rating?
1.) DC current flows via only the primary.
2.) It's possible.
If you you use same 4:1 transformer paralleled, the half of "total" current passes through each transformer primary.
But ... the overall induction is half of transformer primary induction, so the lower frequency limit growing.
2.) It's possible.
If you you use same 4:1 transformer paralleled, the half of "total" current passes through each transformer primary.
But ... the overall induction is half of transformer primary induction, so the lower frequency limit growing.
Dear Radian,
If you place a schematic of the circuit you want to make (Andrea Chiuffolis Amplifier) you make it a lot easier for most people here.
The datasheets from Lundahl always look like a mistery so this isn't helping. Just tell us what kind of step-up or step-down you want, the tube you want to use, the current you use and what bandwidth you like to have. ( be realisitc, don't exepct a miracle like 1Hz to 1MHz)
If you place a schematic of the circuit you want to make (Andrea Chiuffolis Amplifier) you make it a lot easier for most people here.
The datasheets from Lundahl always look like a mistery so this isn't helping. Just tell us what kind of step-up or step-down you want, the tube you want to use, the current you use and what bandwidth you like to have. ( be realisitc, don't exepct a miracle like 1Hz to 1MHz)
Tube is D3a
Andrea:
INTERSTAGE TRANSFORMER
The interstage transformer is used to reduce the output impedance of the vacuum tube, to increase the output current and to create a differential signal in oder to drive the mosfet with opposite phase as required by the Circlotron design.
It is necessary a good 4 : 1+1 with a minimun inductance of 50H to have a good low frequency response if the internal resistance of the vacuum tube is about 2000-2700ohm and the Rdc of primary is more than 300ohm.
Ft(-3dB) = R / ( 2 * 3.14 * L ) = 3000ohm / ( 2 * 3.14 * 50 ) = 9.55Hz
LL1671/30mA in ALT Q configuration have 35H so the version with an air gap for only 20mA will have about 35H * 30mA / 20mA = 52.5H.
Using a 4 : 1 instead of a 2 : 1 + 1 the mosfet grid will be driven with low impedance and more current so there is a better high frequency response and faster slew rate.
Andrea:
INTERSTAGE TRANSFORMER
The interstage transformer is used to reduce the output impedance of the vacuum tube, to increase the output current and to create a differential signal in oder to drive the mosfet with opposite phase as required by the Circlotron design.
It is necessary a good 4 : 1+1 with a minimun inductance of 50H to have a good low frequency response if the internal resistance of the vacuum tube is about 2000-2700ohm and the Rdc of primary is more than 300ohm.
Ft(-3dB) = R / ( 2 * 3.14 * L ) = 3000ohm / ( 2 * 3.14 * 50 ) = 9.55Hz
LL1671/30mA in ALT Q configuration have 35H so the version with an air gap for only 20mA will have about 35H * 30mA / 20mA = 52.5H.
Using a 4 : 1 instead of a 2 : 1 + 1 the mosfet grid will be driven with low impedance and more current so there is a better high frequency response and faster slew rate.
Attachments
Try simulating this to decide how much of low impedance is really enough. Keep in mind these are source followers, no gain, no input capacitance multiplication.
It's a good idea to design the transformer for high-capacitance driving in mind. Adding further capacitance to the secondary will decrease the series resonance of the transformer.
Personally I'd be more than satisfied with cut-off point equal to or above 50kHz, but it's a personal opinion.
ALSO, it is a phase splitting transformer. Constant frequency response and phase of the two secondaries is IMHO mandatory for 20kHz at least. In practice it is hard to make such transformer and the designer should have PHASE SPLITTING priority in his mind when making such transformer.
It's a good idea to design the transformer for high-capacitance driving in mind. Adding further capacitance to the secondary will decrease the series resonance of the transformer.
Personally I'd be more than satisfied with cut-off point equal to or above 50kHz, but it's a personal opinion.
ALSO, it is a phase splitting transformer. Constant frequency response and phase of the two secondaries is IMHO mandatory for 20kHz at least. In practice it is hard to make such transformer and the designer should have PHASE SPLITTING priority in his mind when making such transformer.