I know some of the members of this board have built an Andrea Cioffoli's Power Follower 99 and I have recently put one together also. Mine runs from about 29 V rails and 2 A bias, uses IRFP240 instead IRFP150 and general low impedance capacitors not Elna Cerafines recommended by Ciuffoli.
My question is to those who have built or heard Power Follower 99 and compared to other amps perhaps about the sound characteristics of this amp.
After couple of evenings of listening this amp I have mixed feelings about it’s sound. I need to decide, if I should go further with building this amp by replacing the caps to Cerafines (or similar) and transistors to IRFP150 to see any dramatic sound improvement or should I just drop it and recycle.
One more note: also a decent voltage gain stage is yet to come, I drive my Follower with OPA2134 single opamp circuit right now so this might have influenced total sound as well.
Any thoughts?
regards,
Argo
My question is to those who have built or heard Power Follower 99 and compared to other amps perhaps about the sound characteristics of this amp.
After couple of evenings of listening this amp I have mixed feelings about it’s sound. I need to decide, if I should go further with building this amp by replacing the caps to Cerafines (or similar) and transistors to IRFP150 to see any dramatic sound improvement or should I just drop it and recycle.
One more note: also a decent voltage gain stage is yet to come, I drive my Follower with OPA2134 single opamp circuit right now so this might have influenced total sound as well.
Any thoughts?
regards,
Argo
No voltage gain is the reason that made me discard this project in favour of Aleph 30 (and Aleph X ).
Anyway I saw a interesting article on Rod Elliot's site, where a Power Follower by Pavel Macura is "integrated" with DoZ preamplifier. Since the 2 followers aren't that different you might try a similar arrangement, or switch to that project.
Cheers
Andypairo
Anyway I saw a interesting article on Rod Elliot's site, where a Power Follower by Pavel Macura is "integrated" with DoZ preamplifier. Since the 2 followers aren't that different you might try a similar arrangement, or switch to that project.
Cheers
Andypairo
Andypairo,
Actually to build a voltage gain stage is not a big issue for me right now. I have collected some schematics and good suggestions from other threads and I have the parts to build one. What I am more interested is if the sound of Andrea's Power Follower sound relay heavily on component quality and what are the overall sound characteristics of this amp. I can compare it only to my JHL class A amp now and they really differ from each other.
Argo
Actually to build a voltage gain stage is not a big issue for me right now. I have collected some schematics and good suggestions from other threads and I have the parts to build one. What I am more interested is if the sound of Andrea's Power Follower sound relay heavily on component quality and what are the overall sound characteristics of this amp. I can compare it only to my JHL class A amp now and they really differ from each other.
Argo
preamp for power follower
Yes, the DoZ preamp gives a good sound impression. I have also made a preamp with OPA134 and I would prefer it, but the output voltage swing from OPA is limited to some +/-17V when supplied from +/-18V. You can find more circuits on my original page http://www.pha.inecnet.cz/macura/audiopage.html compared to Project83 on Rod Elliott's page. I would especially like to mention the project on http://www.pha.inecnet.cz/macura/pma1_en.html
Pavel Macura
Yes, the DoZ preamp gives a good sound impression. I have also made a preamp with OPA134 and I would prefer it, but the output voltage swing from OPA is limited to some +/-17V when supplied from +/-18V. You can find more circuits on my original page http://www.pha.inecnet.cz/macura/audiopage.html compared to Project83 on Rod Elliott's page. I would especially like to mention the project on http://www.pha.inecnet.cz/macura/pma1_en.html
Pavel Macura
Changing the FETs to IRP150Ps probably wouldn't change much, I use IRFP044s in my Power Follower 99Cs. I use 3A with -33V. As for the parts reccomended by Ciuffoli, I wouldn't bother for the cerafines (except maybe the output caps). If you read any of his other articles, tube projects expecially, you'll notice that he says only NOS mullard tubes will sound good and other similar things, we all have our own opinions but I think any good quality cap can be used instead of the cerafines. As to the sound, I love mine, I can't compare them to an Aleph or Zen since I've never heard either. I would first of all replace the opamp. I run mine from a tube voltage gain stage and they sound great, I tried running them from an LM6172 preamp, and while it sounded alright, not anywhere near as good as it does now. I hope that helps, but I wouldn't give up yet, I really like the sound of mine, but then again mine's slightly different and we all have different tastes...
I was wondering about the sound also... I thought about building a follower, but with a little twist- run two followers off of each side of a differential pair (such as the zen balanced line stage) and do away with the output cap. I had a schematic going one time that was completely direct coupled and used X feedback on the front end. I opted to build an Aleph X instead.
-NS
-NS
well, I DID make a power follower... but on plugging in everything appart from the resistors blew up - this was due to a faulty transformer that melted it's plastic coverings in about a second - i doubt even if i had fuses it would have helped
I am now making a zen amplifer instead 🙂 with fuses
I am now making a zen amplifer instead 🙂 with fuses
Pavel,
Nice to meet you here.
I looked to follow your follower project for quite some time but as it happened that I was left with those big IRFs lying around already (tried to build a Mini - A, a scaled down Aleph variant while ago but burnt my fingers with it, that is - it refused to let a decent sound out. Still wondering what was the cause, maybe bad input fets or something I don’t know) I decided to try Andrea's project.
Do I read you correct that you prefer OPA134 based pre to DOZ preamp? I have looked at DOZpre as a candidate too but didn’t like the need of those electrolytic output caps. +/-15V provided by OPA I think should be enough for my follower.
This other (New) follower of yours seems interesting too. Newer saw that in your site before. Thanks for the link. Might try that amp out as well someday.
NS
I saw somewhere in the net a page of one Italian guy who built Follower99 too. What I could read there, he tried to diff pair the followers too but couldn’t tame DC offset in output and as whole amp got twice as big and dissipated twice as much also, the sound didn’t improved a bit. At the end he abandoned that approach and returned to the original version with the output cap. I think the Aleph X is much safer way to go If you have decided to go with direct coupling and X- feedback.
JoeBob
Can you please describe the sound of your amp a bit. I know it’s hard to do without any reference but in general or compared to some mass-market amp.
Why I so eagerly seeking for this description is, that I found Power Follower compared to JLH amp to be totally different. JLH amp is very clear, detailed and almost without any coloration of his own. It treats bad recordings as they should be treated - remorseless but it brings out all the little nuances of beauty of excellent recordings. Power Follewer instead lets the bad recordings sound quite good but doesn’t do justice to the good recordings. It sweetens and smoothes out fine details and doesn’t present the performance with such a reality and clarity as JHL amp does. I think it should perform better than that and there must be some kind of fault somewhere in the components, layout or setup.
fezz
Sorry to hear about your accident. Fuses are good thing to have. I blew out couple of electrolytic caps from my amp but saved the output devices because of fusing when I connected the power rails with wrong polarity through an oversight
Argo
Nice to meet you here.
I looked to follow your follower project for quite some time but as it happened that I was left with those big IRFs lying around already (tried to build a Mini - A, a scaled down Aleph variant while ago but burnt my fingers with it, that is - it refused to let a decent sound out. Still wondering what was the cause, maybe bad input fets or something I don’t know) I decided to try Andrea's project.
Do I read you correct that you prefer OPA134 based pre to DOZ preamp? I have looked at DOZpre as a candidate too but didn’t like the need of those electrolytic output caps. +/-15V provided by OPA I think should be enough for my follower.
This other (New) follower of yours seems interesting too. Newer saw that in your site before. Thanks for the link. Might try that amp out as well someday.
NS
I saw somewhere in the net a page of one Italian guy who built Follower99 too. What I could read there, he tried to diff pair the followers too but couldn’t tame DC offset in output and as whole amp got twice as big and dissipated twice as much also, the sound didn’t improved a bit. At the end he abandoned that approach and returned to the original version with the output cap. I think the Aleph X is much safer way to go If you have decided to go with direct coupling and X- feedback.
JoeBob
Can you please describe the sound of your amp a bit. I know it’s hard to do without any reference but in general or compared to some mass-market amp.
Why I so eagerly seeking for this description is, that I found Power Follower compared to JLH amp to be totally different. JLH amp is very clear, detailed and almost without any coloration of his own. It treats bad recordings as they should be treated - remorseless but it brings out all the little nuances of beauty of excellent recordings. Power Follewer instead lets the bad recordings sound quite good but doesn’t do justice to the good recordings. It sweetens and smoothes out fine details and doesn’t present the performance with such a reality and clarity as JHL amp does. I think it should perform better than that and there must be some kind of fault somewhere in the components, layout or setup.
fezz
Sorry to hear about your accident. Fuses are good thing to have. I blew out couple of electrolytic caps from my amp but saved the output devices because of fusing when I connected the power rails with wrong polarity through an oversight
Argo
Wrong polarity huh? Well the same thing happened to me when I assembled mine, it blew a cap but once replaced it worked fine.
As for how mine sounds, well I was never good at describing these things but I'll try. First of all I use panasonic FC caps and not any fancy boutique parts. My amp does indeed sound "warm" but I could atribute that to the tube voltage gain stage, I don't know if that's actually due to the power follower, but that is something Ilike. On bad recordings I notice less imaging but other than that it does do a good job at making them sound better. But on good recordings I was really amazed, one of my favorite CDs, which sounded just like the rest, when I played it for the first time with my power follower I couldn't take it out of the player for a while. I just ordered a few vinyls and am in the process of building a RIAA preamp to see how it sounds with them. But what I did notice about my follower is that the midranges are better than anything I've heard before by a long shot, it made me realise what all the buzz about single-ended class-a MOSFETs was all about...
As for how mine sounds, well I was never good at describing these things but I'll try. First of all I use panasonic FC caps and not any fancy boutique parts. My amp does indeed sound "warm" but I could atribute that to the tube voltage gain stage, I don't know if that's actually due to the power follower, but that is something Ilike. On bad recordings I notice less imaging but other than that it does do a good job at making them sound better. But on good recordings I was really amazed, one of my favorite CDs, which sounded just like the rest, when I played it for the first time with my power follower I couldn't take it out of the player for a while. I just ordered a few vinyls and am in the process of building a RIAA preamp to see how it sounds with them. But what I did notice about my follower is that the midranges are better than anything I've heard before by a long shot, it made me realise what all the buzz about single-ended class-a MOSFETs was all about...
JoeBob said:
And that’s exactly what my follower is missing. Highs are good, very good indeed, lowest bass - I cant tell because I use sub, midbass - I would like some more impact but midrange - its recessed and close compared to JLH 🙁.
Argo
Yep. That’s what I'm starting to think too. Got some tubes and trannies layng around, still need to by some rubber cloves and shoes.😎JoeBob said:
MY POWER FOLLOWER
Hi. I have built The Power Follower about two weeks ago. It plays first without a voltage gain stage - I have a disc player with regulated output. It plays very loudly with my diy speakers. Yesterday I have finished from balanced B.O.Z by Pass ( thanks to Pass 😎 ).
OK! - power follower - voltage rails is + - 30V then I use regulators and in fact there is + - 24 volts, and 2 amps of bias. I don't use capacitors at output. Voltage stage is B.B.O.Z. but I change bias resistors to a current sources ( about 30mA each ), and gain resistor is replaced by pot. It plays fine, but volume control is not so linear. There is + - 40 volt after regulators, about 20 volts on output. Then I give a power zener diode ( it built from bjt, zener diode and resistor from "The Art of Electronics" ) to reduce output DC to about 4 volts. And last block, a dc servo. It is a simple op amp with low pass filter on input, and output at second input of voltage stage.
It sounds great.
Disadventages - low output power ( not for me ), non linear volume conrol, and some like low freqency oscillations when powered up ( but it runs abouts two days, there is a lot of time to repair this ).
If you are interested I could give you a schematics, but I have to draw it ( I have built my amp in "blind" mode for its simplicity ).
Hi. I have built The Power Follower about two weeks ago. It plays first without a voltage gain stage - I have a disc player with regulated output. It plays very loudly with my diy speakers. Yesterday I have finished from balanced B.O.Z by Pass ( thanks to Pass 😎 ).
OK! - power follower - voltage rails is + - 30V then I use regulators and in fact there is + - 24 volts, and 2 amps of bias. I don't use capacitors at output. Voltage stage is B.B.O.Z. but I change bias resistors to a current sources ( about 30mA each ), and gain resistor is replaced by pot. It plays fine, but volume control is not so linear. There is + - 40 volt after regulators, about 20 volts on output. Then I give a power zener diode ( it built from bjt, zener diode and resistor from "The Art of Electronics" ) to reduce output DC to about 4 volts. And last block, a dc servo. It is a simple op amp with low pass filter on input, and output at second input of voltage stage.
It sounds great.
Disadventages - low output power ( not for me ), non linear volume conrol, and some like low freqency oscillations when powered up ( but it runs abouts two days, there is a lot of time to repair this ).
If you are interested I could give you a schematics, but I have to draw it ( I have built my amp in "blind" mode for its simplicity ).
hi.
regarding the mosfet in the Power Follower, is there any best choice for it? HEXFET or L-MOS? IRF? hitachi 2SK? Magnatec BUZ? HEXFET?
thanks
Mincy
regarding the mosfet in the Power Follower, is there any best choice for it? HEXFET or L-MOS? IRF? hitachi 2SK? Magnatec BUZ? HEXFET?
thanks
Mincy
I use IRFP240 as shown in other thread:
http://www.diyaudio.com/forums/solid-state/170987-dc-offset-class-se-power-amp.html
Anyway, the DC offset in the output may not be constant due to themperature rising (due to different of MOSFET vs BJT CCS thermal).
After it is hot, the MOSFET seems less conductive than BJT (although the IRFP thermal coefficient is positive), so if we use Lateral, I am afraid if i will be different too far (since coefficient is negative/less conductive when hot).
May be the best one is using all MOSFET with same characteristic (not BJT for CCS).
CMIIW.
Thanks,
Ervin L
thanks ervinl!
you got the point, indeed V-mos and L-mos differ in thermal coefficient sign. If swap, it will be a disaster, well i'll stick to V-mos.
after 2 months, i came up with the PF in 2SK1058 version (which is not the one reccomanded by the author). I also add a tube VAS (in mu-stage) to provide acceptable volume level.
This amp is featured with a standby mode which limits the output current to 0.2A, while the normal operation mode the MOS will sucks slightly more than 2A.
Everything was fine while testing on standby mode: voltage at the source of the upper MOS was stable enough, while connecting to a headphone, i can hardly hear the hiss/hum. (tube was not connected to the amp board yet!)
However, while running on normal operation, the amp started to behave a little bit weird. Working point, current measured at the resistor were correct, but I heard a strong humming coming out from the headphone.
I just wonder why, does it have to with the crocodile clip wire because of the smaller gauge which could not sustain the high current? or may be because of the extremely hot resistor between the two PSU caps(~2A passing through 0.5ohm, ~2,4watt of power dissipation)? or bad earthing?
Any suggestion? thank you.
This amp is featured with a standby mode which limits the output current to 0.2A, while the normal operation mode the MOS will sucks slightly more than 2A.
Everything was fine while testing on standby mode: voltage at the source of the upper MOS was stable enough, while connecting to a headphone, i can hardly hear the hiss/hum. (tube was not connected to the amp board yet!)
However, while running on normal operation, the amp started to behave a little bit weird. Working point, current measured at the resistor were correct, but I heard a strong humming coming out from the headphone.
I just wonder why, does it have to with the crocodile clip wire because of the smaller gauge which could not sustain the high current? or may be because of the extremely hot resistor between the two PSU caps(~2A passing through 0.5ohm, ~2,4watt of power dissipation)? or bad earthing?
Any suggestion? thank you.
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I have built the PF99 nine or ten years ago, and I think I have posted my impression somewhere. I will write my impression again because I cannot forget the sound of this amp, and many times I have been tempted to rebuild the amplifier.
This amplifier is not for everyone. It's very good in one side but too bad in other side. Not in good balance imho. Have you heard that some people don't like the sound of CFP? This is probably the worst for them (but some other really like the CFP).
The drawback of this amplifier is that it doesn't have enough drive, impact, sonic... Those words are used to express what I heard, very non-technical. If I relate it with theory (to try to be more civilized, tho I don't understand electronics) I think it is the lack of DYNAMICS (or dynamic range) and in need of higher slew rate to fix the problem.
But this is a buffer or drain follower. I don't understand electronics, but I don't think that this arrangement can be made faster. I tried driving it with 100Vpp preamp hoping that it would be "faster" soundwise, but it was not. I think what it needs to make it faster is a current drive not voltage drive, which I "think" is not possible. And there's no low capacitance mosfet that can go with this highly biased output stage. What Nelson Pass used in his amps are the best (I used IRFP250 from many fanufacturers)
So, if you know electronics, you may have an idea on how to fix it by making it faster. Because you have something very good in this amplifier.
Now the good side of this amplifier. It is simply the most relaxed, pure and low distortion amplifier I have ever heard. Of course this is by listening only. It is my perception, no relationship with measured THD or anything...
My ears are so sensitive to "distortion" (for example I cannot live with Lowther or lower quality full range drivers used by many tube fans). So I know that I really like the sound of vocal from this amplifier. But that's the problem, I don't listen only vocal...
If anyone (who knows electronics) knows anything to fix what I think is missing from this circuit (by adding suitable front end stage), please share, I would love to rebuild the amplifier.
This amplifier is not for everyone. It's very good in one side but too bad in other side. Not in good balance imho. Have you heard that some people don't like the sound of CFP? This is probably the worst for them (but some other really like the CFP).
The drawback of this amplifier is that it doesn't have enough drive, impact, sonic... Those words are used to express what I heard, very non-technical. If I relate it with theory (to try to be more civilized, tho I don't understand electronics) I think it is the lack of DYNAMICS (or dynamic range) and in need of higher slew rate to fix the problem.
But this is a buffer or drain follower. I don't understand electronics, but I don't think that this arrangement can be made faster. I tried driving it with 100Vpp preamp hoping that it would be "faster" soundwise, but it was not. I think what it needs to make it faster is a current drive not voltage drive, which I "think" is not possible. And there's no low capacitance mosfet that can go with this highly biased output stage. What Nelson Pass used in his amps are the best (I used IRFP250 from many fanufacturers)
So, if you know electronics, you may have an idea on how to fix it by making it faster. Because you have something very good in this amplifier.
Now the good side of this amplifier. It is simply the most relaxed, pure and low distortion amplifier I have ever heard. Of course this is by listening only. It is my perception, no relationship with measured THD or anything...
My ears are so sensitive to "distortion" (for example I cannot live with Lowther or lower quality full range drivers used by many tube fans). So I know that I really like the sound of vocal from this amplifier. But that's the problem, I don't listen only vocal...
If anyone (who knows electronics) knows anything to fix what I think is missing from this circuit (by adding suitable front end stage), please share, I would love to rebuild the amplifier.
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