Joachum, I believe there is an error in this schematic you posted - you show the opamp input being fed from the base of the cascode transistor. I thought maybe this was a secret trick, until I saw the 150nF cap to gnd from this point. This connection to the opamp must go to the cascode Tr's collector - yes?
Regards, Allen
No, the way i have drawn the circuit should work. The "Secret Trick" is called a ground referenced common base stage. This circuit is rarely seen and has the advantage of simplicity ( only one bias source) and low noise because the resitor combination is also a kind of current feedback and drops the gain and so the noise. I learned that circuit from Hugh of AKSA fame. If we asume that there is a very high impedance at the cascode collector, then a 470 Ohm resistor in reries
that makes the output impedance even higher and then the base resistance of the cascode resistor in parallel, lowering the impedance slightly but not much we can asume that the 150nF cap is driven by a high impedance current source so with the other 470 resistor to ground it forms a 75usec transimpedance pole. 470 x 0.159 = 74.73 usec. This is a bit lower then the ideal 75 usec because i asume that the output resistance of my theoretical current source is not infine. Actually the 0.159 uF should be a bit higher because in praxis the parallel impedance is lower then 470 Ohm. I am not good at simulating but i
know a person that could do that in minutes. Usually my asumptions are surprisingly accurate and i measue and optimise the values later on my testbench.
that makes the output impedance even higher and then the base resistance of the cascode resistor in parallel, lowering the impedance slightly but not much we can asume that the 150nF cap is driven by a high impedance current source so with the other 470 resistor to ground it forms a 75usec transimpedance pole. 470 x 0.159 = 74.73 usec. This is a bit lower then the ideal 75 usec because i asume that the output resistance of my theoretical current source is not infine. Actually the 0.159 uF should be a bit higher because in praxis the parallel impedance is lower then 470 Ohm. I am not good at simulating but i
know a person that could do that in minutes. Usually my asumptions are surprisingly accurate and i measue and optimise the values later on my testbench.
Over the weekend i finished my first complete preamp including cabinet. Actually it is not ready yet because i am still working on some subassemblies.
The phonostage is a High Z MPP, volume control is a Tent Labs relay module with remote control and the output stage is a PSG buffer. PSU is a Twisted Pear Placid.
I call it Markus because it is for a very god friend and mentor of mine.
The phonostage is a High Z MPP, volume control is a Tent Labs relay module with remote control and the output stage is a PSG buffer. PSU is a Twisted Pear Placid.
I call it Markus because it is for a very god friend and mentor of mine.
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After Allen left i took a deep breath and thought how i can get part of the sound back we had. Markus visited me today to see the progress his preamp makes and we tried al 4 poweramps i have at home right now. The Berentzen Special Edition, an LFD poweramp,
A Strada Digital amp and my LA Audio Monoblocks. I had dusted them of some weeks ago found 4 output tubes that match well, adjusted the bias to AB ( ca.70mA) and switched into triode mode. Fortunately the LA Audio saved my day. It sounds beautiful on my MPL.
On loudspeakers with medium sensitivity i prefer the Berentzen but my MPLs sounded much better with the tubes. I think this is a good compromise i can live with until i make
my own Poweramp, but not soon, i am too busy.
Another photo shows the little Cearaudio turntable with Lyra Helicon. It sounds very good. A super expensive turntable is not the only way to good sound. The cartridge and the setup is very important too
A Strada Digital amp and my LA Audio Monoblocks. I had dusted them of some weeks ago found 4 output tubes that match well, adjusted the bias to AB ( ca.70mA) and switched into triode mode. Fortunately the LA Audio saved my day. It sounds beautiful on my MPL.
On loudspeakers with medium sensitivity i prefer the Berentzen but my MPLs sounded much better with the tubes. I think this is a good compromise i can live with until i make
my own Poweramp, but not soon, i am too busy.
Another photo shows the little Cearaudio turntable with Lyra Helicon. It sounds very good. A super expensive turntable is not the only way to good sound. The cartridge and the setup is very important too
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Good idea. I am planning to visit Holger in two month anyway.
Today i also did some more work on my JG-Self. It has a second balanced MC input now with a simpler topology and i fitted some Spectrol conductive plastic pots.
I hope they sound better then the surprisingly good sounding Omeg carbons.
I will report tomorrow how the changes perform.
Today i also did some more work on my JG-Self. It has a second balanced MC input now with a simpler topology and i fitted some Spectrol conductive plastic pots.
I hope they sound better then the surprisingly good sounding Omeg carbons.
I will report tomorrow how the changes perform.
LA Audio Monoblocks?
I think this is a good compromise i can live with until i make my own Poweramp said:Dear Joachim,
Just admit it, you are falling in love with the Tube's sound
I think you need to try this circuit from the one and only Nelson Pass.
Try this with your speakers, you'll love it!
Firstwatt is also good, but I seem too have a weakness for these kind of amps. Nelson is a brilliant designer when it comes to building a musically "simple" amp that sound like a tube amp
And when my Mono triodes are ready you'll be the first to be invited to listen to it! Well, together with Jaap if you don't mind driving a few hours
Cheers,
Audiofanatic
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Sorry, Nelson's amps DO NOT sound like a tube amp, to a good tube amp designer. To someone who has only ever heard high NFB SS amps, they may sound more like a tube amp, but they are FAR FAR from being even close to a good tube amp.
They sound like (to me) poorly engineered solid state amps - with very little feedback - which in this case is not a good thing. IMO.
Regards, Allen
I Respect your opinion !
Hello Sir,
Please don't get me wrong, I don't say that Nelson Pass is the only one that builds good amp's. You are a Gentleman that is known for his good taste in designing amplifiers that sounds wonderful. That much is clear I hope.
Please be careful with what you just said about sound of an amplifier.
You may hurt someone with these words
Whatever "we" (read: designers) accept as/ find good sounding equipment, is not always good for everybody, it's a matter of tast!
I respect you and hope you understand the meaning of these words.
Sincerely,
Audiofanaitc
Hello Sir,
Please don't get me wrong, I don't say that Nelson Pass is the only one that builds good amp's. You are a Gentleman that is known for his good taste in designing amplifiers that sounds wonderful. That much is clear I hope.
Please be careful with what you just said about sound of an amplifier.
You may hurt someone with these words
Whatever "we" (read: designers) accept as/ find good sounding equipment, is not always good for everybody, it's a matter of tast!
I respect you and hope you understand the meaning of these words.
Sincerely,
Audiofanaitc
Tube amp !
That's why I love well engineered (SE) Tube amp's
I hope there is nothing wrong with that from your point of view
Best regards,
Audiofanatic
That's why I love well engineered (SE) Tube amp's
I hope there is nothing wrong with that from your point of view
Best regards,
Audiofanatic
Soundquality is very subjective. I like two types of amplifiers :
One that is perfect on the testbench : that is the reason i am using the Audionet Max2.
It was originally designed for blood analysys at the University of Bochum. It is so low in distortion and has so low noise, wide bandwidth and high power that i have not found one design here on the web that even comes close. It does not have a sound at all and that meens it can sound dreadfull or wonderfull.
The other type of amplifier i like i call a "musical" amplifier. Amplifiers like that are mostly designed by designers with a strong personality that put a lot of work into their product to make them sound good on all types of material. Usually they use little or no feedback, do not have an extremely high damping factor and a carefully designed distortion profile that somehow is able to enhance the musical pleasure. Some of them have high bandwidth, some of them don´t. You can talk to the designer for hours about the reasons why and will never find out the secret. Also consider for what they are designed. A 7W single ended 300B, provided that it does not humm or hiss like a waterfall can do magic on a 110dB efficient Goto Mushroom Bell tweeter simply because it is very linear at tiny output levels. So lets do not fight against each other but accept that we all are similiar but different the same time.
One that is perfect on the testbench : that is the reason i am using the Audionet Max2.
It was originally designed for blood analysys at the University of Bochum. It is so low in distortion and has so low noise, wide bandwidth and high power that i have not found one design here on the web that even comes close. It does not have a sound at all and that meens it can sound dreadfull or wonderfull.
The other type of amplifier i like i call a "musical" amplifier. Amplifiers like that are mostly designed by designers with a strong personality that put a lot of work into their product to make them sound good on all types of material. Usually they use little or no feedback, do not have an extremely high damping factor and a carefully designed distortion profile that somehow is able to enhance the musical pleasure. Some of them have high bandwidth, some of them don´t. You can talk to the designer for hours about the reasons why and will never find out the secret. Also consider for what they are designed. A 7W single ended 300B, provided that it does not humm or hiss like a waterfall can do magic on a 110dB efficient Goto Mushroom Bell tweeter simply because it is very linear at tiny output levels. So lets do not fight against each other but accept that we all are similiar but different the same time.
I fully understand you Joachim !
So lets do not fight against each other but accept that we all are similiar but different the same time.
Nicely said Joachim, I fully agree with you on this.
BTW, the amp I was talking about is not a 300B.
I've listen a lot to this type of amp also Jaap's own 300B and like his 300B a lot and other brands also, but the one I'm building uses a milk bottle triode
It's not an Ongaku, it's something different, more on this when I'm done and Jaap had listen and fine tuned it.
Best regards,
Audiofanatic
So lets do not fight against each other but accept that we all are similiar but different the same time.
Nicely said Joachim, I fully agree with you on this.
BTW, the amp I was talking about is not a 300B.
I've listen a lot to this type of amp also Jaap's own 300B and like his 300B a lot and other brands also, but the one I'm building uses a milk bottle triode
It's not an Ongaku, it's something different, more on this when I'm done and Jaap had listen and fine tuned it.
Best regards,
Audiofanatic
Seems I opened a can of worms here. I meant specifically speakers of some 100 dB (104 in my case) and NOT say 82 dB electrostats. I note though that Srajan Ebaen at 6moons reviewed a Firstwatt F3, compared it to a list of SE tube amps that he liked, and claimed the F3 to sound similar to a his SE tube amps but more extended.
Sorry boys, i think i opened up that can of worms.
This is not a thread to discuss the sound of poweramps.
It is just that i am searching for an amp that drives my MPL.
As always i think i have to build somethig myself. I simply can not afford Allens amp at the moment that gave sofar the best performance, but i know now where the journey goes to.
This is not a thread to discuss the sound of poweramps.
It is just that i am searching for an amp that drives my MPL.
As always i think i have to build somethig myself. I simply can not afford Allens amp at the moment that gave sofar the best performance, but i know now where the journey goes to.
