i don't think i've seen a current mirror used that way with a VAS like that before. it seems strange that it would work so well.
very clever!
when's the first model ready?
( i had to ask😀 )
mlloyd1
very clever!
when's the first model ready?
( i had to ask😀 )
mlloyd1
I'm really impressed !
Keep up good work and I'm waiting you for a listening session. 🙂
Regards,
Tibi
Keep up good work and I'm waiting you for a listening session. 🙂
Regards,
Tibi
Thank you all for your kind words.
I have a question for all of you. Did you see this type of folded cascode VAS used before in a commercial or DIY amplifier?
With the help of Q14 I was able to obtain an almost constant current over R14 which means a very high and linear OLG.
The current mirror is inherited from MKI version but isn't necessary and can be replaced with a bootstrap CCS. In this configuration, colector of Q14 can be conected to ground.
R13 can be used to null the offset
Cheers,
Mihai
I have a question for all of you. Did you see this type of folded cascode VAS used before in a commercial or DIY amplifier?
With the help of Q14 I was able to obtain an almost constant current over R14 which means a very high and linear OLG.
The current mirror is inherited from MKI version but isn't necessary and can be replaced with a bootstrap CCS. In this configuration, colector of Q14 can be conected to ground.
R13 can be used to null the offset
Cheers,
Mihai
Mihai,
Your (unique) circuit appears to be a combination of a topology attributed to a German named Lender, and a folded cascode. I'm pretty sure Borbely has used it.
Lender arranged the two resistor loaded collector outputs from the LTP so that one was connected to the VAS base, and the other to the VAS emitter, enhancing OLG with diff drive. You've interposed an additional transistor cleverly.... I have not seen this before but that's not to say it hasn't been done. The truth is, almost nothing is new...... but I do not criticise, it is very clever.
Cheers,
Hugh
Your (unique) circuit appears to be a combination of a topology attributed to a German named Lender, and a folded cascode. I'm pretty sure Borbely has used it.
Lender arranged the two resistor loaded collector outputs from the LTP so that one was connected to the VAS base, and the other to the VAS emitter, enhancing OLG with diff drive. You've interposed an additional transistor cleverly.... I have not seen this before but that's not to say it hasn't been done. The truth is, almost nothing is new...... but I do not criticise, it is very clever.
Cheers,
Hugh
I make big efforts to decrease components count but without loose sonic quality.
I will compare two version of this type of VAS. The one as in posted schematics and the other without mirror and with a simple bootstrapped 3ma CCS form the (-) rail to folded cascode transistor.
I will compare two version of this type of VAS. The one as in posted schematics and the other without mirror and with a simple bootstrapped 3ma CCS form the (-) rail to folded cascode transistor.
I dont think anyone has used that vas single ended before, but with dual differencial Ltps. Nearly all of Pavel dudeks amps use the scheme. For reference you could look at his DPA range of amps, Im pretty sure Bobberly would also have gone dual differencial.
Congrats on a nice design, very good performance.
Congrats on a nice design, very good performance.
Sorry guys but this amplifier now incorporate some non-publicdomain ideas (AKSA) and I will not post in the net future development topologies based on this design. The results, good or bad sounding, will be non-commercial and non-publicdomain.
I strongly recommend you to build the original RMI-FC100, version with dual differential VAS, which is a great sounding amplifier, or to further develop around this single ended VAS topology.
Cheers
Mihai
I strongly recommend you to build the original RMI-FC100, version with dual differential VAS, which is a great sounding amplifier, or to further develop around this single ended VAS topology.
Cheers
Mihai
Hi Hugh,
You said it before me : it's the Lender's circuit, it was used by Erno Boberly in his Mosfet amplifier published in Electronics World.
However I do not agree to call it a folded cascode. It is a simple common emitter amplifying the differential voltage between R14 and R15, not that different of what can be seen on the JC1 circuit.
The most curious thing to me is the pair Q14 Q16 loaded by a current mirror.
You said it before me : it's the Lender's circuit, it was used by Erno Boberly in his Mosfet amplifier published in Electronics World.
However I do not agree to call it a folded cascode. It is a simple common emitter amplifying the differential voltage between R14 and R15, not that different of what can be seen on the JC1 circuit.
The most curious thing to me is the pair Q14 Q16 loaded by a current mirror.
That's ill news.....
Nice flat OLG, however i suspect in real life it is a bit different.... Impressive nevertheless 😱
I see you have used pole-zero compensation, how does that help with the sound?
Nice flat OLG, however i suspect in real life it is a bit different.... Impressive nevertheless 😱
I see you have used pole-zero compensation, how does that help with the sound?
roender said:
Mihai,
Not sure what V7 stands for, but for estimating the open loop gain and phase, you need to be careful with breaking the loop. See http://www.spectrum-soft.com/news/winter2001/loopgain.shtm In this particular case you can neglect the current gain contribution and retain the VOC test circuit only.
Forr,
Many thanks, you are 100% right, my mistake........
I think Mihai's amp is outstanding; very contemporary design.
Hugh
Many thanks, you are 100% right, my mistake........
I think Mihai's amp is outstanding; very contemporary design.
Hugh
syn08 said:
Yes, V7 is there for OLG measurements.
Are you shure that this method isn't valid? 😉
"roender"
i'm using lt spice to simulate
how can you do to make measurment for slew rate ?
i've try square wave but result is not real ?
i'm using lt spice to simulate
how can you do to make measurment for slew rate ?
i've try square wave but result is not real ?
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