Indeed I use the DCB1 powered with two very special shunts. It conveys a really wide soundstage with really stunning insight regarding microdetail.
Much better than my previous pedja buffer that in itself was already superior to my initial LM4562 preamp.
It is an excellent device bringing back the art to electronics. If I were a designer I would wish I would have designed it 
Till now the very few negative comments I read were based on breadboarded copies of the original B1 circuit.
If DCB1 (aka Mezmerize) is written the design is meant as sold here on Diyaudio. A hard to beat design.
Till now the very few negative comments I read were based on breadboarded copies of the original B1 circuit.If DCB1 (aka Mezmerize) is written the design is meant as sold here on Diyaudio. A hard to beat design.
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Good... I know it is good but there is still room for improvements...
After reading this presentation I got the idea that one can search for an optimum bias for a push pull buffer so I decided to play a bit with the bias and increased it slightly from 130 to 180mA.
Measurements showed a real improvement... squares look like squares until 50kHz and faze shift is also greatly reduced in both extremes.
The major improvement is in bandwidth that now extends to 580khz at -3dB and starts at 1.4Hz at -3dB.
I could not believe in my measurements so I repeated them several times with consistent results.
Quite dazzled I connected the amp to my main system and now it sings !!!
Treble is now really extended and clear. Image grew a lot laterally as well as in depth. Bass is perfectly integrated, going low with very good control.
Voices are true and cymbals have real slam.
The amp is really quiet and I find the 19dB gain adequate in my system.
I plotted my measurements that I post here hoping for some edificant comments.
PS: I now consider this amp very good and the only drawbacks I can find are related with the opamp input .... maybe it is possible to use a suitable discrete jfet input ?
Attachments
You can destroy your soundcard.
I would make a 100 Ohm voltage devider so 90 Ohm in series with 10 Ohm.
From the 10 Ohm resistor ( plus ground ) it goes into the soundcard.
Bob Cordell said that 100 Ohm is a tough load for a poweramp so you will see a bit more distortion then it would have, say into 8 Ohm.
This is a bit counter intuitive i know. Usually a lighter load gives less distortion.
I would make a 100 Ohm voltage devider so 90 Ohm in series with 10 Ohm.
From the 10 Ohm resistor ( plus ground ) it goes into the soundcard.
Bob Cordell said that 100 Ohm is a tough load for a poweramp so you will see a bit more distortion then it would have, say into 8 Ohm.
This is a bit counter intuitive i know. Usually a lighter load gives less distortion.
Thank you, I will try that but I believe it will not cure the slight lack of speed in the transients that impairs ultimate fluidity and clarity.
Between fast changing notes in the trumpet there is a sense of silence where there should be some decay.
It is a very distinct feature of opamps IMO. I would like to try a simple discrete input ans VAS stage.
You can try the LME49870 that can stand plus-minus 22V so you get more power.
You could also try the LME49880. It is a JFet double.
You can simply stack the input opamps ( parallel them ) and connect the output together with a 10 Ohm resistor. Then you have double the current drive. I learned that simple trick from Douglas Self and it works.
You could also try the LME49880. It is a JFet double.
You can simply stack the input opamps ( parallel them ) and connect the output together with a 10 Ohm resistor. Then you have double the current drive. I learned that simple trick from Douglas Self and it works.
I like this one :
Tube buffer
It is simple and does not need much HV.
This liquidity and decay you desire comes from a harmonic distortion profile i think.
Actually a tube stage does not sound distorted subjectively.
Tube buffer
It is simple and does not need much HV.
This liquidity and decay you desire comes from a harmonic distortion profile i think.
Actually a tube stage does not sound distorted subjectively.
You mean a tube buffer as preamp ?
This buffer can not replace the opamp... no gain.
I do not know if it is distortion I am lacking but I believe not. I built several opamp preamps and also some discrete ones both bjt and fet with and without coupling caps. the best sounding (more open and detailed) are the discrete ones.
It is the distortion, i am sure. The guys in the studios know that too.
I do not talk about massive distortion, it is more subtle.
Hiraga did some research on this, also the guys at Stereoplay in germany.
They had an enigma. Tube amps came out of the subjective listening test very well but they did not measure as good as some transistor amps.
I do not talk about massive distortion, it is more subtle.
Hiraga did some research on this, also the guys at Stereoplay in germany.
They had an enigma. Tube amps came out of the subjective listening test very well but they did not measure as good as some transistor amps.
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