I stumbled upon something really strange. I don't understand this circuit, but it seems to perform very well. It's similar to the Leach moving coil head amp, but the capacitors that grounded the bases have been removed. I don't think I can call this a grounded base amplifier any more. The whole thing floats. I set the current generator to -6.2mA output and what happens is that the power supply just shifts without disturbing the current flows in the transistors. What's really weird is that distortion is extremely low. It's something like five or six zeros, then a number. S/N is about -130dB or more. Go figure, I don't understand it. So, this circuit doesn't seem to care about the DC offset from the current generator.
Attachments
Last edited:
I seems to work without grounding the emitters of the bias transistors. I think you could get a noise advantage when you put an elctrolytic between the bases of the bias transistors.
OK, I just now tried that. S/N is the same: -140dB. Distortion is the same too. I don't think I need it. I'm still amazed! wow.
Attachments
Your circuit dont have a ground connection so the current that comes in have to go out, there is no other way, the distortion is zero.
This dont work for a dac but maybe for a MC head
I have now put the Santos I/U into my system as phono MC pre-pre. Noise is very low and gain is good. As MM stage i use my House RIAA, i called it that way because it should never leave the house as other stages do.
Impressions are very favorable. I have heard and made many transimpedance stages like the Nobrainer, Rosi, The Grail, Aquox and even a balanced version that was the MPP2010.
Usually they major in what is known as "PRAT factor", that is power, rhythm, attack.
They can sound a little over damped and not as fluid as a Fet or tube stage though.
This Santos I/U is different from all transimpedance stages i heard, no, make that from all stages i heard. At first it struck me that the sound was not harsh or sharp at all but still very transparent and open. That comes with a lot of air and liquidity. It resolves tiny details but does not give an analytic impression. The sound stage has an enormous size. The most iintriquing ability is to sound tonally correct but also light and fast on the feet. Tonal colors are fleshed out but do not give the impression to be from " material".
It is rather a see through quality that lets the tone exist without any obvious encavement and without boundary. Lighter then air, more like light but curiously not slim or threadbare. I would say it sounds simply very natural. We can expect some surprises.
Impressions are very favorable. I have heard and made many transimpedance stages like the Nobrainer, Rosi, The Grail, Aquox and even a balanced version that was the MPP2010.
Usually they major in what is known as "PRAT factor", that is power, rhythm, attack.
They can sound a little over damped and not as fluid as a Fet or tube stage though.
This Santos I/U is different from all transimpedance stages i heard, no, make that from all stages i heard. At first it struck me that the sound was not harsh or sharp at all but still very transparent and open. That comes with a lot of air and liquidity. It resolves tiny details but does not give an analytic impression. The sound stage has an enormous size. The most iintriquing ability is to sound tonally correct but also light and fast on the feet. Tonal colors are fleshed out but do not give the impression to be from " material".
It is rather a see through quality that lets the tone exist without any obvious encavement and without boundary. Lighter then air, more like light but curiously not slim or threadbare. I would say it sounds simply very natural. We can expect some surprises.
Attachments
congratulations Joachim... 🙂
I'm relieved that the problem was not from the circuit.
And from the photos it seem very stable.
I´m happy that it also sounds good, as this is our final objective.
I am more then relieved too, i could not even sleep so well 🙂
What really bugged me was that all currents seemed to be OK and NOTHING came out of it.
I think the nS oszilation i had on the scope was just a stray field.
What really bugged me was that all currents seemed to be OK and NOTHING came out of it.
I think the nS oszilation i had on the scope was just a stray field.
Ok. now you make me with more desire to construct my one. 🙂
But i have so many circuits that i dont know were to start.
I think im going to try first my original circuit.
Last edited:
One thing that you should try, is replacing the input transistors with the nxp BISS, maybe you get a surprise, this are very good at low input impedance. and i bet that the Rbb are very low.
Or leave as it is, if you like the end result 😉
Or leave as it is, if you like the end result 😉
I will get some.
I also experimented with some Zetex SMD that are very low Rbee`but i did not like them as much as the BCs i am using. I have some very low impedance Renesas i can try.
I also experimented with some Zetex SMD that are very low Rbee`but i did not like them as much as the BCs i am using. I have some very low impedance Renesas i can try.
What do you like to win with the BISS ? I asume less distortion.
In terms of speed we are alraedy at 4.5Mhz and a gain over 30 and noise is really low.
And with a much simplified circuit.
Anyway, i am open to sugestions and look forward to your full steam implementation.
In terms of speed we are alraedy at 4.5Mhz and a gain over 30 and noise is really low.
And with a much simplified circuit.
Anyway, i am open to sugestions and look forward to your full steam implementation.