WOW Mr G.
Hi Joachim,
I'm speechless, WOW !
I love stroomspiegels, (Current Mirrors) I don't know what to say, it's so great to see you posting these circuits.
The only thing that comes to mind is, why didn't I think of this before??
Well done Joachim, I'm very happy with this and will let you know how it performs when it's ready.
Danke
atb,
Audiofanatic
Hi Joachim,
I'm speechless, WOW !
I love stroomspiegels, (Current Mirrors) I don't know what to say, it's so great to see you posting these circuits.
The only thing that comes to mind is, why didn't I think of this before??
Well done Joachim, I'm very happy with this and will let you know how it performs when it's ready.
Danke
atb,
Audiofanatic
Jose`, the line stage with current mirror is not finished yet. The problem is that for a certain amount of gain we need a certain loading resistor. If the output impedance of the mirror is high the resistor value is low or we end up with too much gain, say 220 Ohm in my example is about right. We have only the current that flows in the input stage. Take the Starless input stage for example. We have 2 2SK170BL on Idss in there. That is 16mA. 16mA into 220 Ohm is 3.52V. That is just enough for a line stage but i would prefer if we are able to swing plus-minus 12V that is over the Fets to get a better dynamic range. One way is to raise the current in the mirror but that is expensive because we need a lot of 2SK170BL. After thinking hard and long ( this is for you Michael ! ), a better way would be to lower the output impedance of the mirror. That way we can raise the loading resistor say to 1500 Ohm for full swing. To lower the output resistance we can lower the differential feedback resistors ( now 50 kOhm ) or we can go back to simpler mirrors like the Widlar or three transistor mirror. Anyway, we will solve that problem When you ask me how i came to the idea to use mirrors i think about that since over 20 years and in the beginning my friends did jokes about me : " That does not work, i tried it" and so it goes. Now you say : " Why didn´t i think about this before". "The times they are a changing " Bob Dylon and later Willy Brand.
I think we need a little gain, otherwise a buffer would do and i am already very pleased with my Buffalo Bill modified diamond. Yes, it is impedance matching and driving a potentially high capacitance cable. Curiously the Forsell sounds better with the Buffalo Bill in the chain and it has already a very elaborate output stage. With a normal CD player with a wimpy analog output stage the effect is even more drastic. 6dB is enough though in most cases. Another issue is that i loose some gain in my balance and volume control.
When i put in 6V, 10V comes out so i would like to compensate for that.
I know that a transimpedance line stage is not easy to design. Therefore i presented the alternative circuits with the Hawksford cascode.
The picture made my day.
When i put in 6V, 10V comes out so i would like to compensate for that.
I know that a transimpedance line stage is not easy to design. Therefore i presented the alternative circuits with the Hawksford cascode.
The picture made my day.
Attachments
When he doesn't post on DIYAudio
Jack,
It's simple, my friend Joachim sleeps when we don't see him posting on the forum.
I already ask him this a few times and his answer was, (in short) a few hours a day spread over 24 hours.
We are a bit alike Joachim and I
Regards,
Audiofanatic
Jack,
It's simple, my friend Joachim sleeps when we don't see him posting on the forum.
I already ask him this a few times and his answer was, (in short) a few hours a day spread over 24 hours.
We are a bit alike Joachim and I
Regards,
Audiofanatic
Good, this is interesting. Then you can compare the much more complex FPS to the Starless.
I am still in Vienna after the Klangbilder show. We had a Suesskind Rauschfrei at work. That is the FPS with some additions. For example i can short Pin 3 to Pin1. That way i was able to compare balanced to unbalanced. I thought balanced brought out even more details and "air". For one particular customer this was a bit too much and a preferred the "simpler" sound of the unbalanced. Anyway, the show was very well attended and the sound that most exhibitors had was better then i heard in Munich at the High End show. My personal best sounds of the show was Manger with a new very nicely made active speaker and Avantgarde. I usually do not like horns so much but they had a very big room with the speakers far from my listening place and it worked. Daniela Manger was streaming with a Micro Mega over Wifi and Avantgarde had Doc Feikert on the turntable with Kuzma arm and Lyra Skala. The setups could not be different but both played music so well that i could forget about the technology and only listened to the music. There was also an interesting speaker from Podzus - Zellaton, the Emotion. I heard that this 2 way system does not use a crossover on the bass-mid. The sound showed great potential but the setup was not finished when i came into the room. I missed the Trenner and Friedel presentation. I met people i trust that recommended that room to me.
I am still in Vienna after the Klangbilder show. We had a Suesskind Rauschfrei at work. That is the FPS with some additions. For example i can short Pin 3 to Pin1. That way i was able to compare balanced to unbalanced. I thought balanced brought out even more details and "air". For one particular customer this was a bit too much and a preferred the "simpler" sound of the unbalanced. Anyway, the show was very well attended and the sound that most exhibitors had was better then i heard in Munich at the High End show. My personal best sounds of the show was Manger with a new very nicely made active speaker and Avantgarde. I usually do not like horns so much but they had a very big room with the speakers far from my listening place and it worked. Daniela Manger was streaming with a Micro Mega over Wifi and Avantgarde had Doc Feikert on the turntable with Kuzma arm and Lyra Skala. The setups could not be different but both played music so well that i could forget about the technology and only listened to the music. There was also an interesting speaker from Podzus - Zellaton, the Emotion. I heard that this 2 way system does not use a crossover on the bass-mid. The sound showed great potential but the setup was not finished when i came into the room. I missed the Trenner and Friedel presentation. I met people i trust that recommended that room to me.
Our setup at Klangbilder 2011 in Vienna :klangBilderWien's Channel - YouTube
The blue light comes from the Suesskind Rauschfrei.
The blue light comes from the Suesskind Rauschfrei.
looks like a very small room.... interesting tweeters......
hopefully you will see (and hear) my starless at ETF..... case is drilled, now i need to solder the circuit, will use perfboard. transistors are selected....
one question, then NPNs and PNPs i have are matched for current gain, but between them the gain is different, do you think that may cause a problem?
hopefully you will see (and hear) my starless at ETF..... case is drilled, now i need to solder the circuit, will use perfboard. transistors are selected....
one question, then NPNs and PNPs i have are matched for current gain, but between them the gain is different, do you think that may cause a problem?
You can run into problems with offset. You can adjust the emitter resistors. Small differences here have a big effect on the offset. That is the only problem when you do not use servo. The offset you get will take away a bit of dynamic range. I think plus minus 100mV is more then good enough and even plus minus 500mV tolerable. The effect on the sound will be minimal. When i build the prototype of the circuit i did not even match the BJTs. Maybe thermo coupling will help the drift but i did not try that.
I am still searching for a low distortion transimpedance line amp. Here is my latest thinking. It is a folded driven cascode. Other then the Hawksford or bootstrap cascode this is driven by the source resistors of the input Fets. It is potentially quite linear and does not have such a high output impedance so that the voltage that can develop over the gain setting output resistor is limited too much. Here is an interesting paper about J-Fets :
http://ist-socrates.berkeley.edu/~phylabs/bsc/PDFFiles/bsc5.pdf
http://ist-socrates.berkeley.edu/~phylabs/bsc/PDFFiles/bsc5.pdf