I seen UGS4 module on PASS X250, does it as same as UGS2,3 module in PASS X2 ?
I think it's cascode jfet+transistor and drive with little mosfet (zvn\zvp) but I don't understand how to use zvn/zvp stage to drive power mosfet by use irfdxxxx for vbe bias in balanced aplication.
I want to apply this module for input stage of AYRE V3 PROTO is it posible ?
Please me Mr.PASS (only simplify)
Best regard
analog guy
I think it's cascode jfet+transistor and drive with little mosfet (zvn\zvp) but I don't understand how to use zvn/zvp stage to drive power mosfet by use irfdxxxx for vbe bias in balanced aplication.
I want to apply this module for input stage of AYRE V3 PROTO is it posible ?
Please me Mr.PASS (only simplify)
Best regard
analog guy
Attachments
I was tempted to release this JFET power amp I've been working on as a "hot follower" circuit, meaning just the output stage and leave the voltage gain to the user. During development, I was using a front end not unlike an Aleph--IRF610 differential, but biased with a (single) current source. It worked well, but was somewhat limited in voltage swing for anything more than a modest power amp. In addition, the bandwidth (-3dB circa 90kHz) was not as wide as I like. And so on and so forth. With that in mind, I set out to put together another front end.
I wasn't explicitly trying to emulate either Nelson or John Curl, but found myself with a complementary JFET front end, which then needed cascoding (I did not fold) for voltage reasons. As things stand now, it will work with a wide range of rail voltages with minimal modification (two resistor values). I believe it satisfies "X" requirements.
The downside is that it uses a 2SK389 & 2SJ109, both of which are difficult to find and comparatively expensive. I have a source for new 2SK389s, but they make only N-ch devices, hence no 2SJ109s. Bummer.
My intention is to fiddle with this front end a bit more, then release it as part of the JFET amp. I will then do one of two things--either go on to the next power JFET topology on my list, or pull together an entirely different front end that uses more commonly available parts (the J310, perhaps--lower gain, but a nice part in its own right and can pass a fair amount of current).
If all goes well, this front end will stand on its own as a John Curl-style transconductance line stage, or work with another, non-power JFET amplifier output stage; a normal push-pull N & P-ch MOSFET output, for instance.
If someone does post another front end, it will be interesting to see whether we end up with a case of convergent evolution.
Grey
I wasn't explicitly trying to emulate either Nelson or John Curl, but found myself with a complementary JFET front end, which then needed cascoding (I did not fold) for voltage reasons. As things stand now, it will work with a wide range of rail voltages with minimal modification (two resistor values). I believe it satisfies "X" requirements.
The downside is that it uses a 2SK389 & 2SJ109, both of which are difficult to find and comparatively expensive. I have a source for new 2SK389s, but they make only N-ch devices, hence no 2SJ109s. Bummer.
My intention is to fiddle with this front end a bit more, then release it as part of the JFET amp. I will then do one of two things--either go on to the next power JFET topology on my list, or pull together an entirely different front end that uses more commonly available parts (the J310, perhaps--lower gain, but a nice part in its own right and can pass a fair amount of current).
If all goes well, this front end will stand on its own as a John Curl-style transconductance line stage, or work with another, non-power JFET amplifier output stage; a normal push-pull N & P-ch MOSFET output, for instance.
If someone does post another front end, it will be interesting to see whether we end up with a case of convergent evolution.
Grey
So Grey, I take it you're not the mystery poster we're all waiting for here? Whatever happened to that line level pre-amp project you had burning in several months ago? You said you were going to post it if all went well. What's the story?
If it's any help I have UGS type circuit I've built but not yet powered up. It's based on acaudio's work from last summer and uses cascoded 'k389's and 'J109's with four current mirrors at each corner and 610/9610 followers lifted from the Aleph Ono. The whole thing is set down in a context lifted from the X2 pre-amp ver 2. It was designed to replace the gain block of the Aleph P with a stepped attenuator hung on the output. I was planning to post it in a couple of months (if it worked).
I would be happy to post the schematic and maybe even a photo if the other poster doesn't show up. It demonstrates what ANALOG GUY requested but it ain't tested.
Cheers,
Graeme
If it's any help I have UGS type circuit I've built but not yet powered up. It's based on acaudio's work from last summer and uses cascoded 'k389's and 'J109's with four current mirrors at each corner and 610/9610 followers lifted from the Aleph Ono. The whole thing is set down in a context lifted from the X2 pre-amp ver 2. It was designed to replace the gain block of the Aleph P with a stepped attenuator hung on the output. I was planning to post it in a couple of months (if it worked).
I would be happy to post the schematic and maybe even a photo if the other poster doesn't show up. It demonstrates what ANALOG GUY requested but it ain't tested.
Cheers,
Graeme
OK here is a UGS type line stage. It is meant to operate in an Aleph P type of setting with input selection up stream and an attenuator on the outputs. It's based on acaudio's UGS posted last summer. To that has been added an array of NP breadcrumbs. It's been built but not tested.
Here's the circuit in a nutshell.
1) The input JFET diff pairs are cascoded with BJTs. The cascodes put about 7 volts across the JFETS. V1 is adjusted to give 4ma of operating current through each JFET.
2) The current mirrors are level shifters and provide no gain. I was going to use 857's and 957's but couldn't get one of them at the time. These transistors are matched for gain and Vbe.
3) The output followers are lifted from the Aleph Ono and the bias is set by measuring across the 33 ohm resistors.
There are a number of unanswered questions:
1) I don't know if the offset adjustments are the right ones or if they have enough range. I am hoping that all will be revealed when the power goes on.
2) I don't know if load resistors are required off the outputs of the current mirrors. We'll just have to see.
Hey ANALOG GUY I hope this answers some of your questions. You're on your own trying to fit this into the V3! But keep the board posted on what happens. Sounds like a very creative project.
Mr. P - thank you again for the crumbs.
Cheers,
Graeme
Here's the circuit in a nutshell.
1) The input JFET diff pairs are cascoded with BJTs. The cascodes put about 7 volts across the JFETS. V1 is adjusted to give 4ma of operating current through each JFET.
2) The current mirrors are level shifters and provide no gain. I was going to use 857's and 957's but couldn't get one of them at the time. These transistors are matched for gain and Vbe.
3) The output followers are lifted from the Aleph Ono and the bias is set by measuring across the 33 ohm resistors.
There are a number of unanswered questions:
1) I don't know if the offset adjustments are the right ones or if they have enough range. I am hoping that all will be revealed when the power goes on.
2) I don't know if load resistors are required off the outputs of the current mirrors. We'll just have to see.
Hey ANALOG GUY I hope this answers some of your questions. You're on your own trying to fit this into the V3! But keep the board posted on what happens. Sounds like a very creative project.
Mr. P - thank you again for the crumbs.
Cheers,
Graeme
The line stage was a made-to-order thing with 24dB gain. I used a 2SK389 as a straight differential driving an IRF610 follower. Cap-coupled the output rather than stick in a level shifter. The signal only went through two active devices. If I recall correctly, bandwidth was around 300kHz. Distortion .07%?...something like that. Only 7dB NFB--down in tube territory. Sounded very nice (scared the dooky out of a buddy of mine who has a big CAT preamp). The circuit was single-ended, so it wouldn't be of use for this application. Not that it would be all that difficult to make it balanced, but I opted to do complementary differentials this time for four times the fun.
Incidentally, that line stage caused me to give up on the Panasonic film caps. WIMA polypropylene is the ticket. They're harder to get, but sound notably better in the midrange and high end. Mouser carries a rather eclectic assortment of values at reasonable prices. I ran the IRF610 fairly hard for a line stage (50mA?) and used a 3.3uF WIMA PP bypassed with a small polystyrene. Nearly as good as the big MIT tin & polystyrene for a fraction of the cost. The Panasonic film caps are roughly equivalent to the WIMA in the bass, so perhaps I'll use them for something to do with my subs. Who knows?
Grey
Incidentally, that line stage caused me to give up on the Panasonic film caps. WIMA polypropylene is the ticket. They're harder to get, but sound notably better in the midrange and high end. Mouser carries a rather eclectic assortment of values at reasonable prices. I ran the IRF610 fairly hard for a line stage (50mA?) and used a 3.3uF WIMA PP bypassed with a small polystyrene. Nearly as good as the big MIT tin & polystyrene for a fraction of the cost. The Panasonic film caps are roughly equivalent to the WIMA in the bass, so perhaps I'll use them for something to do with my subs. Who knows?
Grey
I don't know about the Panasonic polypropylene--I was using the 10uF polyester. It's no real surprise that polypropylene sounds better than polyester, but I needed larger values in order to get the frequency rolloff down.
Grey
EDIT: You want the schematic? No problem. Remind me when I'm at home and can get to it.
Grey
EDIT: You want the schematic? No problem. Remind me when I'm at home and can get to it.
Some concept coming soon
I used ACAUDIO & MY & DAVID BERNING design concept for a new PCB layout, it's quite good result with simulation and now I designing this schematic (I don't use 2SK389, 2SJ109, ZVN3310, ZVP3310, ZTX450, ZTX550) but I used 2N5458/5461, IRF610/9610, BC550/560, so I have to change parts value for best frequency response with 220uF coupling IN/OUT, UNBALANCED/BALANCED.
Maybe I have a wrong schematic but I don't care because it's only DIY project.
Best regard
analog guy
I used ACAUDIO & MY & DAVID BERNING design concept for a new PCB layout, it's quite good result with simulation and now I designing this schematic (I don't use 2SK389, 2SJ109, ZVN3310, ZVP3310, ZTX450, ZTX550) but I used 2N5458/5461, IRF610/9610, BC550/560, so I have to change parts value for best frequency response with 220uF coupling IN/OUT, UNBALANCED/BALANCED.
Maybe I have a wrong schematic but I don't care because it's only DIY project.
Best regard
analog guy
Attachments
Mysterious Poster...
Well, as you guys seem to be full of ideas, here's the version I use :
Pretty close to acaudio's one, but I made some cosmetic changes :
- Higher bias for the input jfets (3.8 mA)
- BJT cascode for the first stage
- Choose Zetex mosfets (lower capacitance)
- Added "McMillan magic resistors" to stabilize the differential offset, as done in the Aleph X
Straight from the box, it already shows a ridiculous absolute offset (+/- 5mV).
But with matched mosfets (M1 matched with M2 and M3 matched with M4) I can go under one mV. In free air, the offset still wanders a bit, but I lately added a little thermal coupling with aluminium bars for all the active devices, and the absolute offset stays under 1 to 2 mV for hours. The relative offset is always ridiculous and typically under 0.5mV.
Now for the sound... All I can say is : Wowwww
It easily blows away my BoSoZ. A perfect match to my AXs. It's a rocket : fast and stratospheric. Added depth and width, so quick on transients. Marvelous highs, no part of the spectrum is privilegied. Widens the scene, reveals every aspects of the sound. It was the first time I heard a noise gate shutting so clearly...
And dead silent... Even if I made PCBs for them, the whole thing is breadboarded with thin wires, low quality volume pots at the output... And despite of that, absolutely no noise...
Made some measurements for what it's worth. Absolutely flat response from 5Hz to 20 kHz, mainly H2 distorsion (-70/-75 dB), but I will remake the measurements with the final version.
I'll try to post some pics on Friday (I'm having hard times finding time ), showing the breadboarded horror
All I can say is : Thanks, Mr Pass
Cheff
Well, as you guys seem to be full of ideas, here's the version I use :
Pretty close to acaudio's one, but I made some cosmetic changes :
- Higher bias for the input jfets (3.8 mA)
- BJT cascode for the first stage
- Choose Zetex mosfets (lower capacitance)
- Added "McMillan magic resistors" to stabilize the differential offset, as done in the Aleph X
Straight from the box, it already shows a ridiculous absolute offset (+/- 5mV).
But with matched mosfets (M1 matched with M2 and M3 matched with M4) I can go under one mV. In free air, the offset still wanders a bit, but I lately added a little thermal coupling with aluminium bars for all the active devices, and the absolute offset stays under 1 to 2 mV for hours. The relative offset is always ridiculous and typically under 0.5mV.
Now for the sound... All I can say is : Wowwww
It easily blows away my BoSoZ. A perfect match to my AXs. It's a rocket : fast and stratospheric. Added depth and width, so quick on transients. Marvelous highs, no part of the spectrum is privilegied. Widens the scene, reveals every aspects of the sound. It was the first time I heard a noise gate shutting so clearly...
And dead silent... Even if I made PCBs for them, the whole thing is breadboarded with thin wires, low quality volume pots at the output... And despite of that, absolutely no noise...
Made some measurements for what it's worth. Absolutely flat response from 5Hz to 20 kHz, mainly H2 distorsion (-70/-75 dB), but I will remake the measurements with the final version.
I'll try to post some pics on Friday (I'm having hard times finding time
), showing the breadboarded horror All I can say is : Thanks, Mr Pass
Cheff
Attachments
And the PCB I use.
This one is temporary. I'm currenly making a double sided one, mainly for aesthetic purposes More seriously, I want to add some compensation caps, since I detected very little oveshoot on square signals. Very layout dependent, since I didn't have this problem on the very first prototype...
Cheff
This one is temporary. I'm currenly making a double sided one, mainly for aesthetic purposes
More seriously, I want to add some compensation caps, since I detected very little oveshoot on square signals. Very layout dependent, since I didn't have this problem on the very first prototype...Cheff
Hi Jam, nice to see you rambling around here
No coupling caps were necessary
With thermal coupling, absolute offset is under 1 to 1.5mV, with slow variations due to home wind. But the whole setup has no casing, so I thing it overestimates the offset variations. It's mainly a thermal problem, since I clearly saw the differences before and after the thermal coupling. Before, the 0.1mV digit on the DMM changed at each reading, and after, the same digit stays stable for 5 to 10 seconds, even longer in case of fair weather conditions . BTW, if people want to use it without coupling caps, I think it's better to leave it on all the time. At cold startup, the offset begins at 20-25 mV, and rapidly stabilize to its nominal and almost null value.
Anyway, even without thermal coupling, and with matched mosfets, the offset very seldom rises above 5mV...
Differential offset is always below the mV (0.2 to 0.5mV max typical)
Well it's only at prototyping stage for the moment, so specifications may change without notice
Cheff
No coupling caps were necessary
With thermal coupling, absolute offset is under 1 to 1.5mV, with slow variations due to home wind
. But the whole setup has no casing, so I thing it overestimates the offset variations. It's mainly a thermal problem, since I clearly saw the differences before and after the thermal coupling. Before, the 0.1mV digit on the DMM changed at each reading, and after, the same digit stays stable for 5 to 10 seconds, even longer in case of fair weather conditions . BTW, if people want to use it without coupling caps, I think it's better to leave it on all the time. At cold startup, the offset begins at 20-25 mV, and rapidly stabilize to its nominal and almost null value.Anyway, even without thermal coupling, and with matched mosfets, the offset very seldom rises above 5mV...
Differential offset is always below the mV (0.2 to 0.5mV max typical)
Well it's only at prototyping stage for the moment, so specifications may change without notice
Cheff
Hi Graeme,
Thanks for your kind comments. But also thank Nelson
Indeed it outperforms my heavily biased (65mA/Fet) BoSoZ, especially in the area of high frequencies. The BoSoZ seem to cast a veil on this part of the spectrum, while the UGS reveals it. But no harsh, just silk
And it also goes very low, without any boomy aspect. Everything is where it should be...
But the main thing is that it seem to widen the scene in a spectaculay way... I dunno where it comes from... And all of this without any special or audiophile component... Black magic, or am I just another proud father ?
And looking closer, it's not that complicated. Not more than my CCSed BoSoZ...
Thanks for your kind comments. But also thank Nelson
Indeed it outperforms my heavily biased (65mA/Fet) BoSoZ, especially in the area of high frequencies. The BoSoZ seem to cast a veil on this part of the spectrum, while the UGS reveals it. But no harsh, just silk
And it also goes very low, without any boomy aspect. Everything is where it should be...
But the main thing is that it seem to widen the scene in a spectaculay way... I dunno where it comes from... And all of this without any special or audiophile component... Black magic, or am I just another proud father ?
And looking closer, it's not that complicated. Not more than my CCSed BoSoZ...
Hi Cheff,
Yes you're right. I thank the man every chance I get. You're right too about the simplicity if you look at the overall component count. What I was referring to is the number of stages. There's something about the elegance of a single transistor line stage that is very compelling - unless it's a zero transistor line stage.
We could probably toss this back and forth all day.
Graeme
Yes you're right. I thank the man every chance I get. You're right too about the simplicity if you look at the overall component count. What I was referring to is the number of stages. There's something about the elegance of a single transistor line stage that is very compelling - unless it's a zero transistor line stage.
We could probably toss this back and forth all day.
Graeme
Graeme
Some remarks:
- it seems to me that you have positive feedback. Your circuit is not inverting (like Cheff's), so you have to feed back the + output to the - input and vice versa
- turn Q7, drain must be attached to the negative rail, not to output
- with R38 and R29, do you want some "current feedback"? For offset reduction?
Success
Tino
Some remarks:
- it seems to me that you have positive feedback. Your circuit is not inverting (like Cheff's), so you have to feed back the + output to the - input and vice versa
- turn Q7, drain must be attached to the negative rail, not to output
- with R38 and R29, do you want some "current feedback"? For offset reduction?
Success
Tino
Hi Zinsula,
Yes you are right about the number of inversions. I realized this after re-reading may notes last night. The inside ends of R39 and R31 should be swapped. R38 and R29 return to a common point so they're fine. Without the followers this is actually a single gain stage amp. I have not used current mirrors in this way before and was intending to sort all this out experimentally before posting.
Correct on Q7. Thank you.
R38 and R29 are the "MacMillan" resistors used to help stabilize absolute offset. They are taken from the X2 preamp ver 2 schematic.
Thank you for the input.
Graeme
Yes you are right about the number of inversions. I realized this after re-reading may notes last night. The inside ends of R39 and R31 should be swapped. R38 and R29 return to a common point so they're fine. Without the followers this is actually a single gain stage amp. I have not used current mirrors in this way before and was intending to sort all this out experimentally before posting.
Correct on Q7. Thank you.
R38 and R29 are the "MacMillan" resistors used to help stabilize absolute offset. They are taken from the X2 preamp ver 2 schematic.
Thank you for the input.
Graeme
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