Audiofanatic
You would be better off with the parallel FET's and an a gain stage vs. the bipolar transistors due to leakage currents. Also, that input cap should be a Teflon or polystyrene.
Tubes or ok but their noise is just to much for me. The transformers I have heard had no balls.
A comman gate fet have a natural low impedance. John Dunlevy used this in an older design and worked well. The parts are much better now.
"This is my Texan answer"
You would be better off with the parallel FET's and an a gain stage vs. the bipolar transistors due to leakage currents. Also, that input cap should be a Teflon or polystyrene.
Tubes or ok but their noise is just to much for me. The transformers I have heard had no balls.
A comman gate fet have a natural low impedance. John Dunlevy used this in an older design and worked well. The parts are much better now.
"This is my Texan answer"
Hi,
Johnson noise from the tubes in my circuit is the same as a 70 Ohm resistor...
With a CCS on the anode the PSU noise is out of the picture, no cathode resistors either...
It does I/V perfectly well but it relies on the tubes you use and the noise of the JFETs used as CCSs.
Hope you see the humour....
Cheers,
Johnson noise from the tubes in my circuit is the same as a 70 Ohm resistor...
With a CCS on the anode the PSU noise is out of the picture, no cathode resistors either...
It does I/V perfectly well but it relies on the tubes you use and the noise of the JFETs used as CCSs.
Hope you see the humour....
Cheers,
jewilson said:
The inpedance looking in the source of a fet is 1/Gm...in a typical fet we have 10mA /volts...
So we have 100 Ohms of input inpedance with the fet stage...
With the bipolar the impedance looking at the emiter is 25/Ic...so as the current in the schematic is 1,1mA we end up with 22 Ohms...
Five times better!
"This is my Portuguese answer!"
Cheers
Hi,
Shall I put you through the thinking?
The ECC88/6DJ8 has some qualities few other tubes posess: it's low noise, has very good transconductance and is linear at Vg=0.
Add to that that it's perfectly happy transforming I/V just like a J-FET, stick a CCS on it's anode and you have what a MC needs...
The I/V is done by the load resistor serving as the gridleak and hey, the tube is forced into current mode operation, elegant and simple.
I use a very low output MC and I can't hear any noise...
Not in my system anyway, at a 92dB/WM I'd expect to hear it yet I don't. No noise and dynamic range to die for.
Cheers,
Shall I put you through the thinking?
The ECC88/6DJ8 has some qualities few other tubes posess: it's low noise, has very good transconductance and is linear at Vg=0.
Add to that that it's perfectly happy transforming I/V just like a J-FET, stick a CCS on it's anode and you have what a MC needs...
The I/V is done by the load resistor serving as the gridleak and hey, the tube is forced into current mode operation, elegant and simple.
I use a very low output MC and I can't hear any noise...
Not in my system anyway, at a 92dB/WM I'd expect to hear it yet I don't. No noise and dynamic range to die for.
Cheers,
Tubos!
Hi Frank,
I'll go for the tube version, eventualy!
But first I would want to know if you can supply the 4 tubes and, what would be the price?
I'm gona use the Raven R2 Tweeter 96db/W/M, instead of the Martin Logans, so, what about het noise of this head amp vs. the Hiraga/Threshold?
Audiofanatic
Hi Frank,
I'll go for the tube version, eventualy!
But first I would want to know if you can supply the 4 tubes and, what would be the price?
I'm gona use the Raven R2 Tweeter 96db/W/M, instead of the Martin Logans, so, what about het noise of this head amp vs. the Hiraga/Threshold?
Audiofanatic
Hi,
We need to look at the tube's transfer curves in the circuit proper, than look at what it's going to see next and how it will look than etc.
I designed it in such a way that the system as a hole is holistic, the preamp can be used for MM cartridges, the MC Hammer + MM preamp work together well too...
Respecting all standards along the way.
In fact I can't think of a single cartridge it can't cater for...
The preamp's output can drive both lowish impedance and long capacitive cable without changing it's frequency response within the audio band and often way beyond.
This set of qualities is why I'd like Audiofanatic to understand that matching commercial product can and often does result in a mismatch...
Not to mention the fact that most commercial designs need to be even more stringent designing their product...
Designing for your own needs is alot easier, believe me.
Cheers,
We need to look at the tube's transfer curves in the circuit proper, than look at what it's going to see next and how it will look than etc.
I designed it in such a way that the system as a hole is holistic, the preamp can be used for MM cartridges, the MC Hammer + MM preamp work together well too...
Respecting all standards along the way.
In fact I can't think of a single cartridge it can't cater for...
The preamp's output can drive both lowish impedance and long capacitive cable without changing it's frequency response within the audio band and often way beyond.
This set of qualities is why I'd like Audiofanatic to understand that matching commercial product can and often does result in a mismatch...
Not to mention the fact that most commercial designs need to be even more stringent designing their product...
Designing for your own needs is alot easier, believe me.
Cheers,
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