Re: P1.7 tweaks
Hi Andreas,
I understand your "fears" to leave Nelson Pass genius solutions by tweaking and destroy the hole thing.
But you got me wrong, I think. I am also EE and know very well what I do. I even measured some effects with best equipment at a lab at my job. Of cause the Pass circuits are perfect working stuff – but also of cause Pass is equipping devices with this budget limitations of OEMs. Exactly here we DIYer can be extremely happy – our main budget is not an exiting high end aluminum chassis for customers in hifi studios, it can be best material regarding electronic devices, too.
I had the chance to compare my Aleph4 monos blocks to original Aleph2 power stations. They, the pure OEM 2, had no chance. My 4 has almost three times more cap capacity, bypass impulse cap everywhere, soft recovery power diodes, best coupling caps, inductance free power resistors… The OEM 2 was really blown away, the perfect sound of them was improved strongly and lost nothing – it just wins. Tweaking destroys nothing; it just improves the things not given due to OEM budget limits. I had no chance to compare an OEM P1.7 with my clone, but the tendency should be the same. The story is always the same: additional impulse caps to stabilize the function of caps at impulse loads and suppress HF distortions. EE should not have fear, they should know and be open minded to check this up. Many OEMs create "special edition" versions for higher price and do exactly this stuff! Best example is the company AVM in Germany, they copied exactly the tweaks Mr. Hartwig at Thel uses for almost 10 years and which are discussed at audiomap.com forum for now many years. Why should this tweaks be not valid and helpful for the magic Nelson Pass solutions? So I have highest respect for Nelson Pass and also know how to improve the magic performance of his work at free budget.
How to describe the sonically improvements? Well, it is more focus, silence, transparency, dynamics, "freshness" and better saturation and colors of sound. Especially the heights are no longer a bit of soft. The extreme neutrality is combined with more precision. Test it – each step can be easily gone back! It is a pitty that you live far away from my, we could have a nice session – without winners or competition, just to open mind.
By the way, I do not love the M-Cap Supreme 0,1uF for its high price, it is simply the best impulse cap I have ever measured. NO additional inductance, extremely low ESR and neutral frequency behavior. Second best is the M-Cap tin (Zn) 0,1uF, sometimes a bit bright in sound. MKP10 0,1uF from WIMA is comparatively slow and tiered. Wrong bypass caps can destroy the complete harmony in sound, that is the only risk.
Enough tweaking stories from my side. I am a kind of irritated that not more guys and EEs just test tweaks. They would be astonished about the success. Of cause it just makes sense if the hole hifi set chain is already on e high level.
Regards
Klaus
Hi Andreas,
I understand your "fears" to leave Nelson Pass genius solutions by tweaking and destroy the hole thing.
But you got me wrong, I think. I am also EE and know very well what I do. I even measured some effects with best equipment at a lab at my job. Of cause the Pass circuits are perfect working stuff – but also of cause Pass is equipping devices with this budget limitations of OEMs. Exactly here we DIYer can be extremely happy – our main budget is not an exiting high end aluminum chassis for customers in hifi studios, it can be best material regarding electronic devices, too.
I had the chance to compare my Aleph4 monos blocks to original Aleph2 power stations. They, the pure OEM 2, had no chance. My 4 has almost three times more cap capacity, bypass impulse cap everywhere, soft recovery power diodes, best coupling caps, inductance free power resistors… The OEM 2 was really blown away, the perfect sound of them was improved strongly and lost nothing – it just wins. Tweaking destroys nothing; it just improves the things not given due to OEM budget limits. I had no chance to compare an OEM P1.7 with my clone, but the tendency should be the same. The story is always the same: additional impulse caps to stabilize the function of caps at impulse loads and suppress HF distortions. EE should not have fear, they should know and be open minded to check this up. Many OEMs create "special edition" versions for higher price and do exactly this stuff! Best example is the company AVM in Germany, they copied exactly the tweaks Mr. Hartwig at Thel uses for almost 10 years and which are discussed at audiomap.com forum for now many years. Why should this tweaks be not valid and helpful for the magic Nelson Pass solutions? So I have highest respect for Nelson Pass and also know how to improve the magic performance of his work at free budget.
How to describe the sonically improvements? Well, it is more focus, silence, transparency, dynamics, "freshness" and better saturation and colors of sound. Especially the heights are no longer a bit of soft. The extreme neutrality is combined with more precision. Test it – each step can be easily gone back! It is a pitty that you live far away from my, we could have a nice session – without winners or competition, just to open mind.
By the way, I do not love the M-Cap Supreme 0,1uF for its high price, it is simply the best impulse cap I have ever measured. NO additional inductance, extremely low ESR and neutral frequency behavior. Second best is the M-Cap tin (Zn) 0,1uF, sometimes a bit bright in sound. MKP10 0,1uF from WIMA is comparatively slow and tiered. Wrong bypass caps can destroy the complete harmony in sound, that is the only risk.
Enough tweaking stories from my side. I am a kind of irritated that not more guys and EEs just test tweaks. They would be astonished about the success. Of cause it just makes sense if the hole hifi set chain is already on e high level.
Regards
Klaus
Tweaking
Klaus,
thanks again for your thoughts - as said earlier, I would consider 'tweaking' if a comparison of my P1.7 and a 'tweaked' version would clearly show 'significant' differences that could be verified via some sort of 'blind testing' in MY SYSTEM. I am certainly not afraid to tweak, nor am I afraid that I could 'ruin' my amplifier.
I do not want to go down this path before the rest of the system is to the same level of performance than my DIY-PASS components.
Regards,
Andreas
P.S.: We used decent quality components, matched Cs and Qs, good quality (matched) Rs but tried to stay away from exotic parts and snake oil.
Klaus,
thanks again for your thoughts - as said earlier, I would consider 'tweaking' if a comparison of my P1.7 and a 'tweaked' version would clearly show 'significant' differences that could be verified via some sort of 'blind testing' in MY SYSTEM. I am certainly not afraid to tweak, nor am I afraid that I could 'ruin' my amplifier.
I do not want to go down this path before the rest of the system is to the same level of performance than my DIY-PASS components.
Regards,
Andreas
P.S.: We used decent quality components, matched Cs and Qs, good quality (matched) Rs but tried to stay away from exotic parts and snake oil.
Klaus,
I like your experiments with the bypass caps and theory.
I am right in saying from your description that the head of the supply filter bank (initial filtering) benefits the most from the bypassing and then within the regulator itself, but no bypassing on the in board line stage decoupling caps?
Can you post a diagram to show your modifications?
I assume your mods would equally benefit the BOSOZ.
Whats do you use for the output coupling caps by the way?
Cheers
Ian
I like your experiments with the bypass caps and theory.
I am right in saying from your description that the head of the supply filter bank (initial filtering) benefits the most from the bypassing and then within the regulator itself, but no bypassing on the in board line stage decoupling caps?
Can you post a diagram to show your modifications?
I assume your mods would equally benefit the BOSOZ.
Whats do you use for the output coupling caps by the way?
Cheers
Ian
details about tweaks
Hi Ian,
I also like them, the open minded experiments – because the sonically improvements really astonish. I can "promise" Andreas not to need any direct A-B comparison with an OEM or untweaked DIY P1.7. – the differences are really easy to be accessed. Without snake oil and voodoo… Even best components benefit from improvements, especially bypass caps.
I totally agree upon your PSU experience, the initial filtering bank benefits most. All interferences which are shorten or not created here can not disturb the rest. The next level in the 1.7 PSU is the support of the Zener stack. Rests of Zener supply trash then to be cleaned on the PSU FET gate filter cap. And resulting from my tests the 2nd most important place to "help" is the buffer cap at the FET output. Here impulses are really demanded from the signal circuit. At that oversized circuits with 20mA bias current it is hard to argue this way, but… The remaining rest is the line stage cap behind the 3,3Ohms in line filter resistor. Here I found a strange effect like at many other tweaks at various devices before. If this at-front cap is impulse supported as well as the buffer cap at the FET output the sound is like "two pictures superposed". The sound is no longer homogeneous, it is disturbed. So two solutions are thinkable, to support just the cap in-front - or just the one right behind the FET. I found that the first solution increases stability and dynamics, but the sound suffers of saturation and substance somehow. As if the energy supply after "the first fast impulse" is not adequate. The second solution sounds just perfect! So my recipe, keep the in front cap "slow" and support as impulse capable as possible from the PSU cap side. These demands also inductance free resistor for the 3,3Ohms (dissipating less than 0,1W – so use normal metal film resistor) of cause as well as drilled cables for supply.
Sorry, I have no diagram, because there is no universal recipe which impulse bypass cap is the best for this or that electrolytic cap. Here in Central Europe a company called Mundorf has opened the market for better parts. I found that just their 0,1uF caps really sound good, bigger ones are to much. The tin caps have very low ESR and support very well, but somehow sound to sharp and bright sometimes. The Mundorf Supreme is the best cap I know and measured. Standard polyprop caps like WIMA MKP10 are nice, but far behind the lower ESR Mundorfs. They sound somewhat slower and more intransparent. But for first tests perfect. So my topology:
Filter bank behind rectifier: best available bypass cascade. I use 1uF Wima MKP10 to fill mids, 0,1uF M-Cap Supreme as "turbo" and small 10nF MKP ERO1837 63V as HF-cleaner. This cascade fits almost universal at not to fast bigger electrolytics. If smaller and faster ones are used the 1uF is obsolete. Bigger than 1uF often slowes down the sound.
Zener stack: the P1.7 PSU buffers the Zener supply at the gate so IMHO no bigger electrolytic is required. I just use a 0,1uF WIMA MKP10 as HF filter.
Gate buffer electrolytic: the most reasonable and one of the best caps I know is the FC series from Panasonic. Very dynamic and clear, a bit of sharp. A 0,1uF M-Cap tin bypass improves, a WIMA already is to slow and disturbs. A 10nF cleaner also helps much.
Buffer electrolytic behind FET: just the best I know – 1000uF Panasonic FC + 0,1uF Supreme + 10nF. This opens the sound of the P1.7 really immense! Just the FC sounds already very good, but check it out, guys, what you give away!!!!
In front buffer on the line stage PCB: 1000uF Fc without anything. Even a 10nF cleaner creates an inhomogeneous sound.
For coupling caps I tested many stuff: fat 33uF Solen MKP (= polyprop), some paralleled 4.7uF Solen MKPs, some paralleld WIMA MKP10 4,7uF, bypassed with everything like mentioned above. I was never satisfied, slow, rests of in transparency and so on. I never tested the Pass OEM BCs. I found low ESD electrolytics with 10nF MKP bypass the best. Like Elna, Pana FC, Black gate, … . Without 10nF cleaner they sound a bit aggressive and sharp and often bright. No go. BUT with the 10nF bypass everything is gone, really! Just extreme open, fresh and dynamic. Specially the deep bass is unbeleavable clear. I heard some weeks with this solution and then tested the fat foil caps again – it was like covering the clear room with something and retiring most of the musicians… The live like magic was strongly reduced. I can just give the tip to test electrolytics and not to waste room and money for fat foil cap monsters!
A small problem left: 10uF or 30uF Pana FC are almost not available, just bigger ones. With increased cap values the P1.7 circuit needs longer to start up due to the loading time of the bigger caps. At start up the amp should be muted. I delayed the mute from the volume set circuit to 15 seconds and cover the problem. So I use everywhere in my Pass clones exactly the same 220uF FC cap with 10nF bypass. One equal failure character everywere reduces the total failure amount.
So, some readers will have turned there eyes wile reading. But nobody is forced to tweak caps and explore the real performance capabilities of the genius Pass circuits. Isn't Peter denial also bypassing everything with enthusiasm?
Tweaky regards
Klaus
macka said:
Hi Ian,
I also like them, the open minded experiments – because the sonically improvements really astonish. I can "promise" Andreas not to need any direct A-B comparison with an OEM or untweaked DIY P1.7. – the differences are really easy to be accessed. Without snake oil and voodoo… Even best components benefit from improvements, especially bypass caps.
I totally agree upon your PSU experience, the initial filtering bank benefits most. All interferences which are shorten or not created here can not disturb the rest. The next level in the 1.7 PSU is the support of the Zener stack. Rests of Zener supply trash then to be cleaned on the PSU FET gate filter cap. And resulting from my tests the 2nd most important place to "help" is the buffer cap at the FET output. Here impulses are really demanded from the signal circuit. At that oversized circuits with 20mA bias current it is hard to argue this way, but… The remaining rest is the line stage cap behind the 3,3Ohms in line filter resistor. Here I found a strange effect like at many other tweaks at various devices before. If this at-front cap is impulse supported as well as the buffer cap at the FET output the sound is like "two pictures superposed". The sound is no longer homogeneous, it is disturbed. So two solutions are thinkable, to support just the cap in-front - or just the one right behind the FET. I found that the first solution increases stability and dynamics, but the sound suffers of saturation and substance somehow. As if the energy supply after "the first fast impulse" is not adequate. The second solution sounds just perfect! So my recipe, keep the in front cap "slow" and support as impulse capable as possible from the PSU cap side. These demands also inductance free resistor for the 3,3Ohms (dissipating less than 0,1W – so use normal metal film resistor) of cause as well as drilled cables for supply.
Sorry, I have no diagram, because there is no universal recipe which impulse bypass cap is the best for this or that electrolytic cap. Here in Central Europe a company called Mundorf has opened the market for better parts. I found that just their 0,1uF caps really sound good, bigger ones are to much. The tin caps have very low ESR and support very well, but somehow sound to sharp and bright sometimes. The Mundorf Supreme is the best cap I know and measured. Standard polyprop caps like WIMA MKP10 are nice, but far behind the lower ESR Mundorfs. They sound somewhat slower and more intransparent. But for first tests perfect. So my topology:
Filter bank behind rectifier: best available bypass cascade. I use 1uF Wima MKP10 to fill mids, 0,1uF M-Cap Supreme as "turbo" and small 10nF MKP ERO1837 63V as HF-cleaner. This cascade fits almost universal at not to fast bigger electrolytics. If smaller and faster ones are used the 1uF is obsolete. Bigger than 1uF often slowes down the sound.
Zener stack: the P1.7 PSU buffers the Zener supply at the gate so IMHO no bigger electrolytic is required. I just use a 0,1uF WIMA MKP10 as HF filter.
Gate buffer electrolytic: the most reasonable and one of the best caps I know is the FC series from Panasonic. Very dynamic and clear, a bit of sharp. A 0,1uF M-Cap tin bypass improves, a WIMA already is to slow and disturbs. A 10nF cleaner also helps much.
Buffer electrolytic behind FET: just the best I know – 1000uF Panasonic FC + 0,1uF Supreme + 10nF. This opens the sound of the P1.7 really immense! Just the FC sounds already very good, but check it out, guys, what you give away!!!!
In front buffer on the line stage PCB: 1000uF Fc without anything. Even a 10nF cleaner creates an inhomogeneous sound.
For coupling caps I tested many stuff: fat 33uF Solen MKP (= polyprop), some paralleled 4.7uF Solen MKPs, some paralleld WIMA MKP10 4,7uF, bypassed with everything like mentioned above. I was never satisfied, slow, rests of in transparency and so on. I never tested the Pass OEM BCs. I found low ESD electrolytics with 10nF MKP bypass the best. Like Elna, Pana FC, Black gate, … . Without 10nF cleaner they sound a bit aggressive and sharp and often bright. No go. BUT with the 10nF bypass everything is gone, really! Just extreme open, fresh and dynamic. Specially the deep bass is unbeleavable clear. I heard some weeks with this solution and then tested the fat foil caps again – it was like covering the clear room with something and retiring most of the musicians… The live like magic was strongly reduced. I can just give the tip to test electrolytics and not to waste room and money for fat foil cap monsters!
A small problem left: 10uF or 30uF Pana FC are almost not available, just bigger ones. With increased cap values the P1.7 circuit needs longer to start up due to the loading time of the bigger caps. At start up the amp should be muted. I delayed the mute from the volume set circuit to 15 seconds and cover the problem. So I use everywhere in my Pass clones exactly the same 220uF FC cap with 10nF bypass. One equal failure character everywere reduces the total failure amount.
So, some readers will have turned there eyes wile reading. But nobody is forced to tweak caps and explore the real performance capabilities of the genius Pass circuits. Isn't Peter denial also bypassing everything with enthusiasm?
Tweaky regards
Klaus
Tweak caps
Hallo Klaus,
I read about your tweakings with great interest and i have a few questions.
The 10nF MKP ERO1837 63V ??? is that old stock ?
I can only find Vishay MKP 1837 series 160V.
I hope it's almost the same.
What do you mean with "drilled cables for supply"? twisted?
By the way, Mundorf Supreme are really excellent. Did you alreaddy try the gold versions ?
Best regards,
Johan.
Hallo Klaus,
I read about your tweakings with great interest and i have a few questions.
The 10nF MKP ERO1837 63V ??? is that old stock ?
I can only find Vishay MKP 1837 series 160V.
I hope it's almost the same.
What do you mean with "drilled cables for supply"? twisted?
By the way, Mundorf Supreme are really excellent. Did you alreaddy try the gold versions ?
Best regards,
Johan.
Chassis/Case
Josep,
the chassis is a catalog item from Schroff and is called MULTIPAC. It was purchased from RS-components in Germany. It is a standard 19" chassis, in our case with 2 height units (2HE). You have to order the bottom plate and the cover separately. We used an additional 'subchassis' (2mm aluminum) to mount all the transformers, boards etc. etc.) - the bottom plate from Schroff is simply too thin to mount anything heavy onto it.
Regards,
Andreas
Josep,
the chassis is a catalog item from Schroff and is called MULTIPAC. It was purchased from RS-components in Germany. It is a standard 19" chassis, in our case with 2 height units (2HE). You have to order the bottom plate and the cover separately. We used an additional 'subchassis' (2mm aluminum) to mount all the transformers, boards etc. etc.) - the bottom plate from Schroff is simply too thin to mount anything heavy onto it.
Regards,
Andreas
Re: Tweak caps
Hi Johan,
Of cause I meant "twisted"…
You are right. Vishay boght ERO. An old production series was the legend 1830 with 63V. You find it everywhere in OEM high end stuff. This small blue cubes. It seems that the 1837 extented to 160V is somewhat the successor. To be found here, sorry, in German language http://de.farnell.com/jsp/catalog/v...T43ZOH5GADQFIAEWSFE4AVAAS0IV3?prodId=3038543. A Fellow told me that he checked the performance of old 1830 and new 1837 and found no difference. It is a problem to get that small capacity caps for low voltages.
I had forgotten to mention that I checked any addition to my tweaky cascade, like Silver Mica, Styroflex (what is the English word for?) with values from 22pF up to 680pF – no improvement, just inhomogeneous effects to my ears. Styroflex always overlayed the sound with a plastic mat, mica made it to analytic and aggressive. Funny, how huge the sound changes caused by this small caps are! Just EMC behaviour at -70dB seems to drive the sound character. I have accepted, in spite of my problems not to know well explanations for this, forced as the EE I am who has to have a model for everything… Forget theory and use your ears!
I tested no silver or gold version – at that price level my tweaking stops. I am absolutely satisfied with this Supreme+Vishay 1837 trick. If it is consequently used from PSU to frequency crossover in the speakers the result is that outstanding that really no interest to spend more money is stimulated.
Regards
Klaus
joho said:
Hi Johan,
Of cause I meant "twisted"…
You are right. Vishay boght ERO. An old production series was the legend 1830 with 63V. You find it everywhere in OEM high end stuff. This small blue cubes. It seems that the 1837 extented to 160V is somewhat the successor. To be found here, sorry, in German language http://de.farnell.com/jsp/catalog/v...T43ZOH5GADQFIAEWSFE4AVAAS0IV3?prodId=3038543. A Fellow told me that he checked the performance of old 1830 and new 1837 and found no difference. It is a problem to get that small capacity caps for low voltages.
I had forgotten to mention that I checked any addition to my tweaky cascade, like Silver Mica, Styroflex (what is the English word for?) with values from 22pF up to 680pF – no improvement, just inhomogeneous effects to my ears. Styroflex always overlayed the sound with a plastic mat, mica made it to analytic and aggressive. Funny, how huge the sound changes caused by this small caps are! Just EMC behaviour at -70dB seems to drive the sound character. I have accepted, in spite of my problems not to know well explanations for this, forced as the EE I am who has to have a model for everything… Forget theory and use your ears!
I tested no silver or gold version – at that price level my tweaking stops. I am absolutely satisfied with this Supreme+Vishay 1837 trick. If it is consequently used from PSU to frequency crossover in the speakers the result is that outstanding that really no interest to spend more money is stimulated.
Regards
Klaus
Re: Vishay 1837
Hi again,
I hope you have just half of the benefit I got, than you will dance on the table...
I sent by the time to many fellows this small KP1830 drugs (rests here at the lab at my job) and they all couldn´t believe what they got. Coupling electrolytics and the best bypass impulse caps loose really 95% of their aggression and sharpness. As if these failures are catalyzed to pure sound and sound colors. It sounds so mad, but hope for positive results.
Let us know about your results!
Regards
Klaus
joho said:
Hi again,
I hope you have just half of the benefit I got, than you will dance on the table...
I sent by the time to many fellows this small KP1830 drugs (rests here at the lab at my job) and they all couldn´t believe what they got. Coupling electrolytics and the best bypass impulse caps loose really 95% of their aggression and sharpness. As if these failures are catalyzed to pure sound and sound colors. It sounds so mad, but hope for positive results.
Let us know about your results!
Regards
Klaus
Boards
Thomas,
we did the design for the boards but handed our files off to Kristijan (PCB Design) for manufacturing. Kristijan re-implemented the plans into his tool (PROTEL) and produced our boards. As said in an earlier thread - we do not mind Kristijan offering 'our' boards. Similar story for the APOX API board - we specified it and the APOX folks implemented it for us.
We do not have any Gerber files for these boards - if you want a copy of our original design which was the basis for Kristijan's implementation let me know. We used a German tool called 'Target', the homepage is http://www.ibfriedrich.com/english/index.htm.
Best regards,
Andreas
Thomas,
we did the design for the boards but handed our files off to Kristijan (PCB Design) for manufacturing. Kristijan re-implemented the plans into his tool (PROTEL) and produced our boards. As said in an earlier thread - we do not mind Kristijan offering 'our' boards. Similar story for the APOX API board - we specified it and the APOX folks implemented it for us.
We do not have any Gerber files for these boards - if you want a copy of our original design which was the basis for Kristijan's implementation let me know. We used a German tool called 'Target', the homepage is http://www.ibfriedrich.com/english/index.htm.
Best regards,
Andreas
Hi Klaus,
you really got me interested by your post about tuning Alephs.
Great thing,and you are open minded guy.I like this aproach.
Could you please tell me how exactly does look the changes that you apply to the original Aleph 4?
Also (as I'm using Aleph P 1,7,too) those electrolitics that you meant to try in signal path (10 and 30uF).Do you mine bipolar or you used regular ,polar onesWhat brand of soft recovery types diodes did you use? IR or IXYS? Maybe some other?
Bartek
you really got me interested by your post about tuning Alephs.
Great thing,and you are open minded guy.I like this aproach.
Could you please tell me how exactly does look the changes that you apply to the original Aleph 4?
Also (as I'm using Aleph P 1,7,too) those electrolitics that you meant to try in signal path (10 and 30uF).Do you mine bipolar or you used regular ,polar onesWhat brand of soft recovery types diodes did you use? IR or IXYS? Maybe some other?
Bartek
tweak details
HI BARTEK,
Excuse my late answer, I wasn't following up the tread. But here we go…
I showed my Aleph4 under http://www.diyaudio.com/forums/showthread.php?s=&threadid=3600 Sorry, the picture quality is terrible. The problem of hum from the transformer was solved by changing to another producer. The first used transfos were a misconstruction and were accepted as reclamation w/o any problem by the supplier. I guess the iron core was not raisin baked and so it hummed terrible. The main tweaks: DC filter, 25A type soft recovery diodes, bypass impulse caps like mentioned at the main buffer, everywhere polarized 220uF Panasonic FC electrolytic caps bypassed with small 10nF cap like ERO1830/1837 or similar. No use of the vertical 680pF filter cap between input and feedback branch. Inductance free MPC71 metal band power resistors. Consequent P2P wiring – paralleled FETs and R´s are connected by a 2,5qmm copper rod. Small optimizations on Marcs downunder PCB. PCB made off hard paper type, no epoxy.
In my Aleph P like now in the D1 output stage under construction I use everywhere this polarized Panasonic FC electrolytic caps bypassed with small 10nF cap like ERO1830/1837. The values can vary, the voltages also. Farnell and others make them accessible. The sound is maybe maximum open and fresh, I have no harshness. W/O the small bypass they really hit the nerves, that is the reason for many prejudices against them, I think.
I used the diodes I easily got in Germany, http://www.schuro.de/Daten/IR/hfa25pb60.pdf. But I am quite sure that many other types with soft recovery and low resistance = types for high current applications will work pretty fine.
Regards
Klaus
zygibajt said:
HI BARTEK,
Excuse my late answer, I wasn't following up the tread. But here we go…
I showed my Aleph4 under http://www.diyaudio.com/forums/showthread.php?s=&threadid=3600 Sorry, the picture quality is terrible. The problem of hum from the transformer was solved by changing to another producer. The first used transfos were a misconstruction and were accepted as reclamation w/o any problem by the supplier. I guess the iron core was not raisin baked and so it hummed terrible. The main tweaks: DC filter, 25A type soft recovery diodes, bypass impulse caps like mentioned at the main buffer, everywhere polarized 220uF Panasonic FC electrolytic caps bypassed with small 10nF cap like ERO1830/1837 or similar. No use of the vertical 680pF filter cap between input and feedback branch. Inductance free MPC71 metal band power resistors. Consequent P2P wiring – paralleled FETs and R´s are connected by a 2,5qmm copper rod. Small optimizations on Marcs downunder PCB. PCB made off hard paper type, no epoxy.
In my Aleph P like now in the D1 output stage under construction I use everywhere this polarized Panasonic FC electrolytic caps bypassed with small 10nF cap like ERO1830/1837. The values can vary, the voltages also. Farnell and others make them accessible. The sound is maybe maximum open and fresh, I have no harshness. W/O the small bypass they really hit the nerves, that is the reason for many prejudices against them, I think.
I used the diodes I easily got in Germany, http://www.schuro.de/Daten/IR/hfa25pb60.pdf. But I am quite sure that many other types with soft recovery and low resistance = types for high current applications will work pretty fine.
Regards
Klaus
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