| Sherman |
I built a stereo amp using Brian's boards and the basic kit using Panasonic capacitors. It sounds great and I've tried it on three different sets of speakers, two which I've built and one set of Advent/1. I've been able to compare it to a couple of mid-level solid state amps and find it definitely holds its own.
Now a friend of mine has built an amp basically following Brian's schematic but using perf-board and hardwiring the "traces" using 18AWG solid core wire. Since he used what he had in his parts bin the caps he used were cheap Xicons. They are 1000uF, 50V. He used Dale 1% resistors (about 3 times as large as the Phoenix resistors in Brian's kit).
My friend brought the amp over and we sat down and listened to it using the same sources and speakers that I tested mine with. I think his sounds just as good (though it doesn't look as nice and the boards are bigger :D ).
We tried his amp with his power supply and with mine. We also used his ps on my amp. The main difference we heard was when changing power supplies. His is bigger (200VA vs. ~100-120 for mine) and has higher voltage (+-31 VDC vs. +-27VDC for mine). His ps sounded a better on both amps with the Advents, the sound was closer with my higher efficiency home-built speakers.
So... I don't claim to have either a golden ear or high-end sources (a Pioneer turntable with ADC cartridge, an Aiwa DVD player for CDs, and a cheap DVD player for CDs but I thought my amp with the Panasonic caps should have sounded better. Then I read some things on Rod Elliot's site saying the "sound" of capacitors is grossly over-rated. Also the signal path, actually all the paths, in his amp are longer but that doesn't seem to hurt the sound. What do others think? |
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| Jay |
Off course Rod was right when he said that the “sound” of capacitors is grossly over-rated. In fact, it is not only relevant to that peticular saying. The reason is that too many people do not do the work, but reading and hearing :D And also caps do not sound, not even do amplifiers.
We don’t know what exactly happened when you said a sound is “better” than the other. Sometimes people have similar impression due to merely an increase in SPL.
Bigger transformer rating tends to sound better, when it is able to deliver current easily. For a good sound, you need transient or dynamics, so you often need an overated power supply. And so is voltage rating. And EI tends to sound “better” than toroid.
The next part in your chain is the rectifier. You need a fast diodes for good dynamics. Almost any rectifier constructed from axial diodes sound better than any bridge rectifier.
The capacitor, when it is only 1000uF, is unpredictable IMO. But I’m sure that your system won’t sound better if you replace the Panasonic with the Xicons.
Now, why not changing caps? :D :D
About the longer path, it was made from solid (copper) wire, wasn’t it?
The more complicated thing in audio is to know if
what sounds good is really good! |
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| Jocko Homo |
But........
If anyone thinks that any filter cap/transformer combination will "sound" just as good.....or as bad.....as any other, hasn't built enough amplifiers yet.
An amplifier is just a modulated power supply. And the power supply is ........?
Yeah, that's right.
Jocko |
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| carlosfm |
With those sources (as you recognize yourself), you're not going to get reliable conclusions.:whazzat:
Where's the dynamics?
Where's the detail?
Ahhh... forget it.:D
Trash-in-trash-out, the source is the most important component of any system.
IMHO and whatever.:angel:
Note: I'm still waiting for the miracle (some people believe this!:eek: ) of a good amp and speakers making a bad source sound good.:clown: |
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| janneman |
| quote: | Originally posted by Jay
Off course Rod was right when he said that the “sound” of capacitors is grossly over-rated. In fact, it is not only relevant to that peticular saying. The reason is that too many people do not do the work, but reading and hearing :D And also caps do not sound, not even do amplifiers.
We don’t know what exactly happened when you said a sound is “better” than the other. Sometimes people have similar impression due to merely an increase in SPL.
Bigger transformer rating tends to sound better, when it is able to deliver current easily. For a good sound, you need transient or dynamics, so you often need an overated power supply. And so is voltage rating. And EI tends to sound “better” than toroid.
The next part in your chain is the rectifier. You need a fast diodes for good dynamics. Almost any rectifier constructed from axial diodes sound better than any bridge rectifier.
The capacitor, when it is only 1000uF, is unpredictable IMO. But I’m sure that your system won’t sound better if you replace the Panasonic with the Xicons.
Now, why not changing caps? :D :D
About the longer path, it was made from solid (copper) wire, wasn’t it?
The more complicated thing in audio is to know if
what sounds good is really good! |
You know what bothers me? In a power supply, the diodes conduct say 10% of the time (only when the sec voltage is above the cap voltage). That means that 90% of the time the transformer is effectively disconnected fom the amp.
How the hell does the transformer manage to sneak in in those 10% and make up for the sound when it wasn't there in the other 90%?
Jan Didden |
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| SY |
| quote: | | How the hell does the transformer manage to sneak in in those 10% and make up for the sound when it wasn't there in the other 90%? |
Perhaps it's a matter of the degree of coupling between primary and secondary (passing noise)? John Curl was big on that, and it's certainly made me hesitate before using a toroid. Another possibility (and I haven't thought this one through, just shooting from the hip) is what happens near current peaks with the core; could that pass on garbage as it goes near (or past) saturation? |
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| janneman |
| quote: | Originally posted by SY
Perhaps it's a matter of the degree of coupling between primary and secondary (passing noise)? John Curl was big on that, and it's certainly made me hesitate before using a toroid. Another possibility (and I haven't thought this one through, just shooting from the hip) is what happens near current peaks with the core; could that pass on garbage as it goes near (or past) saturation? |
SY,
There is indeed coupling from primary to secondary through a toroid. Toroids are wideband transformers. Am I to understand that this somehow radiates or conducts into the amp to change the sound? Why are we still using toriods then in the first place?
I don't really believe in radiation from a toroid; the tight coupling that promotes the widebanded-ness also prevents it from radiating outwards. Conduction would be a possibility, but that would mean that whatever enters has to take the diodes, reservoir caps, local decoupling etc.
As for saturation effects, yes, that would lower the transformer induction temporarily. What would that do? If anything, the coupling would become less, so junk from outside would be more blocked.
I don't say that different transformers etc cannot influence the sound, but the cases where I have heard it myself are in some tests I've done many years ago with deliberately undersized transformers. I though, hey, the average power of an amp is only 5 watt or so, so I can get away with a tiny transformer. It did change the sound in the sense that the amp sounded much less powerfull and more distorting. At the time I concluded that the severe supply modulation in the peaks caused it, but I didn't proof it to my own satisfaction.
I suspect that here also, as everywhere in audio, psychological effects play a large role if not a dominating one.
Jan Didden |
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| SY |
| quote: | | I suspect that here also, as everywhere in audio, psychological effects play a large role if not a dominating one. |
Let me start with saying that I'm in 100% agreement with this, which should come as no surprise to you.
But claims about changing sound with transformers at least aren't beyond the realm of physics (though there's zero actual evidence that the claim is true). People use toroids because they're compact, low profile, and don't radiate much. But the tradeoff is that they'll transmit garbage from the primary just as efficiently as they'll transmit 60 Hz (ok, 50 Hz for you cycle-deficient Euro-types). |
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| janneman |
| quote: | Originally posted by SY
Let me start with saying that I'm in 100% agreement with this, which should come as no surprise to you.
But claims about changing sound with transformers at least aren't beyond the realm of physics (though there's zero actual evidence that the claim is true). People use toroids because they're compact, low profile, and don't radiate much. But the tradeoff is that they'll transmit garbage from the primary just as efficiently as they'll transmit 60 Hz (ok, 50 Hz for you cycle-deficient Euro-types). |
Cycle-deficient?? Well, I'll be...! You got nothing to brag about, you 110V-potential-challenged lot! Jeez! 110V, in Holland we have bike dynamo's that do better than that.
Seriously, if it is transmitted junk, which only increases for bigger transformers, why is it that 99.99% of the posters report BETTER sound with bigger transformers?
Jan Didden |
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| SY |
| quote: | | which only increases for bigger transformers |
Is that true? I thought that bigger transformers, in general, had looser coupling at high frequencies.
If the hypothesis that this is all psychological is correct, it's not unexpected that Bigger = Better. |
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| Jay |
| quote: | Originally posted by janneman
I suspect that here also, as everywhere in audio, psychological effects play a large role if not a dominating one.
|
Yes, and psychologically, we tend to think that expensive parts sound better.
I have plenty of expensive transformers that are still not used. The build is beautifull. And I'm an artist, in that I think audio is also an art. I like beautifull things (I used to use acrylic to cover my amps). It is bothering me that I love the "sound" of an ugly EI transformer from an old UPS while the beautifull $100 is sitting there unused.
Oh, the "best" sounding toroid I own is a toroid that is custom manufactured for NAD (made in Canada). "HOLMGREN" TRANSFORMER is written on it. I don't know what the hell is that :D |
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| mAJORD |
very intersting topic,
something that interests me is the attittude that THD , signal-noise , and damping factor, among other measurments are considered useless by some audiophiles.....
if any of u are reading, perhaps u could state what other factors make an amp sound 'good' or 'bad' , and why they cant be measured..
something i thought myself was how music unlike a pure simple sinewave signal, consists of almost endles signals superimposed on eachother , and perhaps THD measurements couldnt take into acount how well a given amp could amplify such a complex signal without any impurities, especially when everything was sitting on top of a hefty low freqency bassline :bigeyes: , but I am still learning so perhaps THJD measurments take this into account... or what im saying is irrelevent.. ? ? ? |
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| janneman |
What you say is highly relevant. Most designers and researchers I have read or met agree that THD is just a rough indication of amp linearity. Much effort has been spend throughout the last decades to find a test that correlates with listening preferences. Two-tone intermodulation, is one of them, but for instance the AP systems contain provisions for doing 10 or more tone IM tests. Then there other tests mixing sinus and square wave (low pass filtered) to see how linear the sine is reproduced in the presence of large lf levels. As far as I am aware, progress has been made, but there is not yet a surefire test suite that correlates with listening preferences (under controlled conditions of course).
Jan Didden |
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| Frank Berry |
"there is not yet a surefire test suite that correlates with listening preferences (under controlled conditions of course)."
Absolutely correct. Even after all amplifier parameters are tested, listening (and listener) preferences are added to the mix. |
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| mAJORD |
| thanks , that clears a few things up!. |
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| CRFX |
| I am interested to know what effect "better" caps have in the PS. When they are in the signel path "better" caps should have a noticible effect. But in a PS what differnence does it make? Do they make a smother dc voltage? |
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| Jay |
| quote: | Originally posted by CRFX
I am interested to know what effect "better" caps have in the PS. When they are in the signel path "better" caps should have a noticible effect. But in a PS what differnence does it make? Do they make a smother dc voltage? |
Many said that I’m a very technical person. But in audio, I am a different person. I can read all the theories on how caps work on DC (which I think I have), but what does it give???
One thing I taught myself is that in audio every parts work together in a very unique way. Trade-offs are things you will always encounter, so you must know what to trade and when. You may need a PS cap that have the smoothing ability, or you may want a transformer to do that for you (don’t ask me how) and let the cap to do other things such as serving the output transistor with current in bass passage when the toroid is so poor on this respect. But if your amp is tube you may want to forget that.
In PS, too smooth a DC (or very noise free) usually means a bad transient. A “good” cap is a cap that can do many thing so you don’t have difficulty with the trade-off. With “better” cap in PS I want a silent system but doesn’t harm the sonic. I will make sure that the relatively cheap rectifier does not function as the bottle-neck for this. I will make sure that the trafo is not underrated also.
Many fake capacitors have damaging effect on sound, but I haven’t found that exotic capacitor is justifiable (in term of increased performance per dollar). I can use thick wire for supplying the board and use a small Black Gate on the leg of the output transistor.
Oh, yes, if we think an audio signal path as tunnel of water, you’re right that in the signal path “better” caps should have a noticable effect. But there’s no such tunnel. That’s just an analogy to make things understandable. But you can expand the analogy to uh… multi-dimensional space where uh… forget it :D |
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| sss |
| quote: | Originally posted by mAJORD
something i thought myself was how music unlike a pure simple sinewave signal, consists of almost endles signals superimposed on eachother , and perhaps THD measurements couldnt take into acount how well a given amp could amplify such a complex signal without any impurities, especially when everything was sitting on top of a hefty low freqency bassline :bigeyes: , but I am still learning so perhaps THJD measurments take this into account... or what im saying is irrelevent.. ? ? ? |
THD stands for total harmonic distortion
the thing is that even the most complicated music signal is made of many simple pure sinewaves :nod:
but thats not all
lets say u got a power amp with a gain of 20 and u are measuring the thd at 1Khz freq and the thd at that freq is 1%
now u are doing the same test but under load conditions and the thd is still 1%
if the gain of that amp under load is only 10 the thd metter wount show nothing!! the thd remains 1% even if the signal is attenuated
hope that helps u to understand things better
;) |
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| CRFX |
| quote: | Originally posted by Jay
Oh, yes, if we think an audio signal path as tunnel of water, you’re right that in the signal path “better” caps should have a noticable effect. But there’s no such tunnel. That’s just an analogy to make things understandable. But you can expand the analogy to uh… multi-dimensional space where uh… forget it :D |
::scratches head:::apathic:
probably shouldn't have read that right after work.:xeye:
I'll just stick with some decent panasonics for now. |
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| janneman |
| quote: | Originally posted by Jay
[snip]In PS, too smooth a DC (or very noise free) usually means a bad transient. [snip]:D |
That's completely new for me! Can you explain this? Do you mean a smooth supply without load or under load?
Jan Didden |
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| janneman |
| quote: | Originally posted by sss
[snip]lets say u got a power amp with a gain of 20 and u are measuring the thd at 1Khz freq and the thd at that freq is 1%
now u are doing the same test but under load conditions and the thd is still 1%
if the gain of that amp under load is only 10 the thd metter wount show nothing!! the thd remains 1% even if the signal is attenuated
hope that helps u to understand things better
;) |
No I don't. If the no-load THD is 1%, how can it also be 1% at load? All amps I have ever seen get worse under load. I also have no idea what is meant with the statement that at a gain of 10 the meter would not indicate anything? I realise this may be a language problem?
Jan Didden |
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| runebivrin |
| quote: | Originally posted by CRFX
I am interested to know what effect "better" caps have in the PS. When they are in the signel path "better" caps should have a noticible effect. But in a PS what differnence does it make? Do they make a smother dc voltage? |
If you think about it, the PS caps are in the signal path, at least in a class B amplifier. If you draw arrows indicating the momentaneous flow of current through the output transistors and the loudspeaker when the rectifier diodes aren't conducting, you'll see the current going through the PS caps!
To what extent that affects sound is another issue, for those inclined to debate such things...
Rune |
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| fdegrove |
Hi,
| quote: | | To what extent that affects sound is another issue, for those inclined to debate such things... |
And he asked himself...What is an amplifier?
A modulated powersupply perhaps? Must be....
So you'll be in part listening to that too, so.....
Does it matter what class the amp is running in for the powersupply caps to matter?
Not really, they're always there those nasty electrolytics, aren't they?
So yes, it would matter more in a class B or class AB amp than in a pure class A design but it matters nonetheless.
Nobody ever built an amp with nothing but polyprops in the PSU?
Guess not.
I'll be the first to admit it's easier to do with tubes due to the much higher rail voltages used but the difference is easily heard...
Thankfully electrolytics have much improved over the years but filmcaps haven't exactly been sitting still either.
Give it a try guys,;) |
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| sss |
| quote: | Originally posted by janneman
I also have no idea what is meant with the statement that at a gain of 10 the meter would not indicate anything? |
what i'm trying to say is the gain can change with the load impedance or frequency and the thd metter wount show more distortion |
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| Christer |
| quote: | Originally posted by fdegrove
Nobody ever built an amp with nothing but polyprops in the PSU?
Guess not.
|
There is some company making enormeous film caps to replace
lytics in PSUs and I think Jonathan Carr has used them, or
maybe he just talked about trying them. Not sure if they are
polyprop. though. Probably costs you an arm and a leg anyway. :) |
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| till |
| isn´t it a proble with polypropylene caps they are large? for decouplin of DACs i need small caps to decouple as near as possible at the IC pins. MKS is avaiable in 2,5mm. Also multilayer ceramics X7R are very small. MKP10 is huge. |
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| fdegrove |
Hi,
| quote: | | There is some company making enormeous film caps to replace |
No idea these even existed...
When using tubes most people use something like these caps:
SCR
Lowest available voltage is 250VDC which low for tubes yet too high for most thing SS.
Still the difference is easily heard when upgrading loudspeaker x-over series caps, for instance.
| quote: | | Probably costs you an arm and a leg anyway. |
Not cheap but still worth every penny.
Cheers,;) ;) |
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| fdegrove |
Hi,
| quote: | | isn´t it a proble with polypropylene caps they are large? |
They're often not larger than their polyester equivalents except when you go down to very low voltage such as 63VDC perhaps.
Either way, shouldn't one design the PCB around what's one planning to use on it?
Pitch of robotic insertion components is always stated in the leaflets.
Cheers,;) |
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| Christer |
| quote: | Originally posted by fdegrove
No idea these even existed...
|
Can't for my life remember brand or any links unfortunately.
| quote: |
When using tubes most people use something like these caps:
SCR
|
Yes, the SCRs are available locally here. Not cheap if you need
larger values, but reasonable for smaller ones. We also have
ICEL. Didn't you speak well of them once? |
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| fdegrove |
Hi,
| quote: | | ICEL. Didn't you speak well of them once? |
Indeed, I did.
For non-boutique caps they're among the best you can get in MKP.
Jadis uses them and I'm sure other branders have wound their wrappers around them too.
Unfortunately I can only get them in small values (~0.100µF) and high voltages (~1000VDC+).
For SS PSU use I'm sure there are alternatives by means of the excellent BG caps, for instance or if all alse seems impossible, just bypass elcos with decreasing values of MKP in //.
100µF elco + 10µF MPK + 1µF + 0.100µF + 0.10µF + 0.010µF...
Knowing where to put them so they can work their best is just as important though...
Cheers, ;) |
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| Christer |
| quote: | Originally posted by fdegrove
Indeed, I did.
For non-boutique caps they're among the best you can get in MKP.
Jadis uses them and I'm sure other branders have wound their wrappers around them too.
Unfortunately I can only get them in small values (~0.100µF) and high voltages (~1000VDC+).
|
Aha, seems we have a better selection here then. I can get
MPWR type upt to 1.0uF in 160 and 630V versions and the
1% MPL type up to 4.7uFin 160V. I can also get 160V Evox
Rifa up to 15uF. |
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| fdegrove |
Hi,
| quote: | | Aha, seems we have a better selection here then. |
Elfa?
Cheers,;) |
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| Christer |
| quote: | Originally posted by fdegrove
Hi,
Elfa?
|
Yes. Want me to buy some for you? :) |
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| fdegrove |
Hi,
| quote: | | Yes. Want me to buy some for you? |
Thanks for the kind offer, Christer...
Not yet, I'm still too busy for the coming months upgrading my current stuff to think about cooking up something new...
Tell you what though, I'll definetely build a new phono preamp with not a single electrolytic cap in sight....
Unfortunately it WILL cost me an arm and a leg to get it where I want it. :bawling:
Ciao,;) |
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| Christer |
I may be wrong, but I think the ones I meant were even bigger,
but not as high voltage. |
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| CRFX |
| a 3 foot tall capacitor?!?! for only 1000uf, did I read wrong? |
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| fdegrove |
Hi,
| quote: | | a 3 foot tall capacitor?!?! for only 1000uf, did I read wrong? |
Right or wrong...you may just as well use batteries...:D |
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| Damon Hill |
I thought AVX's glass capacitors were interesting, too.
Available in similar range to silver mica, extremely low
DF and DA and virtually impervious to anything including
the sort of radiation you'd find in reactor cores. :)
From what I see in the Allied catalog, they're VERY expensive.
I have no idea what 'sound' they'd have, if any. Sort of like bulk foil resistors, but much more costly. Best left to your
scientific sample-and-hold instrumentation, I suppose.
I don't believe I will be using them in any amplifier bypass
cap locations, or even in the feedback loop.
http://www.avxcorp.com/docs/Catalogs/ck31-32.pdf
I have several 100 uF @2200 V caps sitting around that
are probably polypropylene/paper? in oil, originally used for
defibrillators. Planning to use them in a tube amp power
supply. I think my source has some more, at $25 apiece.
They're slightly larger than the biggest multi-section 'lytic
you see on many tube amp chassis.
For the really exotic, you might consider carbon aerogel
supercaps. Have to stack a number in series to get the
required voltage, though. |
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| Jay |
| quote: | Originally posted by janneman
That's completely new for me! Can you explain this?
|
To smooth the DC you need to do something. This something you do that harm the transient. You don't need to think that I'm talking about voltage ripples or something. When I said "transient", it is more a "quality" that is known to my ears. This transient-or-noise, is the major trade-off in power supply. |
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| janneman |
...but what is this something to do? How does it influence transient????
Jan Didden |
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| fdegrove |
Hi,
| quote: | | How does it influence transient???? |
I suppose Jay's talking about the capacitor reactance?
Cheers,;) |
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| Nuuk |
Remember that there are two factors influencing the (possible) differences in the sound of components such as capacitors. They are electrical and mechanical.
We can't do much about the electrical factor but has anyone experimented with the mechanical? eg adding mass.
I have just removed 8 capacitors from the PSU for my GC buffer circuit.
The PSU had two stages of regulation using LM317/337 regs and I had read somewhere about adding some extra 220 uF caps to lower the noise from the regulators. Unfortunately, they only added some distortion and now I am wondering if this was because I used some very cheap caps that have been in my parts box for five or six years!
Still on the subject of 'do caps make a difference to the sound', it is always worth remembering that
2 + 3 +11 +1 +6 = 23 as does 5 + 10 + 2 + 6!
In other words, there are many combinations of numbers that arrive at the same total. |
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| Damon Hill |
Large amounts (relatively) of capacitance on 317
regulators may cause them to be unstable.
Slightly smaller amounts on the adj pin will improve
noise rejection; you'll need to see the application
notes. |
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| Nuuk |
Thanks Damon,
I added the 220 uFs after reading a review of regulator circuits (on TNT if I remember correctly).
I may do some more experimenting with 'fresher' caps of different values. |
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| carlosfm |
| quote: | Originally posted by Nuuk
I added the 220 uFs after reading a review of regulator circuits (on TNT if I remember correctly).
I may do some more experimenting with 'fresher' caps of different values. |
Try 100uf.;) |
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| Nuuk |
Any particular reason Mr Carlos? ;) |
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| carlmart |
There's another very good option: Ansar capacitors.
http://www.cricklewoodelectronics.c...ome.php?cat=155
They seem to be sold just by Cricklewood, but they come in up to 80uF and are 400v. For higher voltages (?) you can always do a series.
Kuei Yang Wang is probably listening and can comment about them.
Carlos |
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| carlosfm |
| quote: | Originally posted by Nuuk
Any particular reason Mr Carlos? ;) |
No.
Just because I like and I use them.:D
Seams the right value for me, not too much, not too little.
100uf it is.
Anyway, it's the most common value I see on commercial products after an LM317/337.
I know this doesn't mean anything but...:clown:
Nuuk, just try it and tell us, it seams you have there a particularly sensitive circuit to test this, so...;) |
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| Nuuk |
| quote: | | Nuuk, just try it and tell us, it seams you have there a particularly sensitive circuit to test this, so... |
Just for you Carlos, I will try the 100 uFs but you will have to wait until I have a big enough order as Farnell now have a minimum order of 20UKP :bawling:
BTW Congratulations to Porto last night - now hand over your manager please :devilr: |
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| carlosfm |
| quote: | Originally posted by Nuuk
BTW Congratulations to Porto last night - now hand over your manager please :devilr: |
:whazzat: :D
Well... life goes on, you pay well, you have the best.;)
The french people may not be happy now.
Porto eliminated 3 french teams from the champions league this year.:eek:
Viva o Benfica !!!:D |
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| Christer |
| quote: | Originally posted by carlosfm
No.
Just because I like and I use them.:D
Seams the right value for me, not too much, not too little.
100uf it is.
|
Sounds like real engineering. :) |
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| carlosfm |
| quote: | Originally posted by Christer
Sounds like real engineering. :) |
I'm not an engineer, thanks.
Something against that?:confused:
Engineers measure and get satisfied when it measures right.
I only get satisfied when it sounds good to me.
Something against that?:rolleyes:
If you don't have anything useful to say, shut up.:apathic:
Or else, what's the ideal capacitance after an LM317/337 regulator?
And why?
Tell us, Mr. Engineer.:clown: |
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| Christer |
Carlos,
it was intended as a joke about engineering not about you.
Sorry, if you took it the wrong way. |
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| analog_sa |
| quote: | | Something against that? |
Touchy, aren't we? 100uF may well work in your particular system but to insist that it's the one and only value is absolutely ludicrous. The capacitor type will certainly have stronger audible effect than the value alone. |
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| DSP_Geek |
| quote: | Originally posted by fdegrove
Does it matter what class the amp is running in for the powersupply caps to matter?
Not really, they're always there those nasty electrolytics, aren't they?
So yes, it would matter more in a class B or class AB amp than in a pure class A design but it matters nonetheless.
Nobody ever built an amp with nothing but polyprops in the PSU?
Guess not.
I'll be the first to admit it's easier to do with tubes due to the much higher rail voltages used but the difference is easily heard...
Thankfully electrolytics have much improved over the years but filmcaps haven't exactly been sitting still either.
Give it a try guys,;) |
Well, there are a couple of ways of avoiding electrolytics feeding output transistors directly.
1) Capacitance multiplier
2) Switching power supply
I've heard good things about CMs although I haven't tried them. There are persistent rumours that SPSs have exceptional characteristics - the PanasonicXR45 uses one to feed its class D output stages, which have negligeable PSRR, and people seem to like the thing. Comments?
Francois. |
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| Damon Hill |
An engineer (or engineering wannabe like me :) ) would
have taken measurements with a distortion analyzer
and an oscilloscope if it didn't 'sound right'.
Might have caught some oscillation. Simply tinkering
blind without testing to confirm normal operation is
risky. I know most DIYers don't have any test gear
beyond a DMM nor much technical knowledge, but
that's the chance you take.
To mangle an old saying, measure twice, then
listen. Lots of engineers do this, too. I did extensive
modifications on my all-JFET Hafler SE-100 preamp,
in the process discovering my mods had caused
one of those wretched 7815s to go unstable, which
a local 10 uF cap on the output cleared up.
Call it double confirmation. And it did sound better
afterwards.
(Hey, Carlos! You know what they say about
'French military victorys'...Cinco de Mayo! :D ) |
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| carlmart |
| quote: | Originally posted by Damon Hill
in the process discovering my mods had caused
one of those wretched 7815s to go unstable, which
a local 10 uF cap on the output cleared up.
Call it double confirmation. And it did sound better
afterwards.
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Which mods were that?
You probably tried them, but every time I replaced a 7X15 with an LM3X7 I had sound improvements all over.
Are we going to talk soccer now? Remember I come from Brazil and Argentina!
Carlos |
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| janneman |
Hey Carlos,
You have a funny idea about engineers. Basically an engineer tries to get the best performance by intelligently combining techniques, parts, layout, etc. Measurements are a great help to see if you are going the right way.
That doesn't mean that it must replace listening, of course. But saying hey, I tried 100uF, and it sounds good doesn't seem a very smart way to try to get the best from what you have available. I mean, maybe 50uF sounds even better! Measurements and knowing what you are doing can help you see in which direction and how far to go.
Jan Didden |
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| carlosfm |
| quote: | Originally posted by Christer
Carlos,
it was intended as a joke about engineering not about you.
Sorry, if you took it the wrong way. |
Well then, I'm sorry too.
This net thing is too slow and the smile didn't appear on your post.:bawling:
| quote: | Originally posted by analog_sa
Touchy, aren't we? 100uF may well work in your particular system but to insist that it's the one and only value is absolutely ludicrous. The capacitor type will certainly have stronger audible effect than the value alone. |
Man, I just gave a suggestion for Nuuk to try it.:dodgy:
I didn't say it's the only value.
I said it to try this on HIS circuit, as it seams that HIS circuit is sensitive to these small changes.
BTW I think that, as always, the cap must be NEAR the component (in this case the regulator).
If that's not practical, at least a small 0.1uf near the regulator.
:angel: |
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| janneman |
| quote: | Originally posted by carlosfm
[snip]BTW I think that, as always, the cap must be NEAR the component (in this case the regulator).
If that's not practical, at least a small 0.1uf near the regulator.
:angel: |
Carlos,
You are right that the cap needs to be near the component. But we are not trying to decouple the regulator, we are trying to decouple the amplifier circuit. Therefore, logically, you want the cap as close as possible to the amp circuit.
If that is too far away, you may need an additional cap near the regulator to keep it stable, but that is secondary.
Jan Didden |
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| till |
| i thought i can´t be wrong placing a small cap (200-300nF) and a larger (100-200uF near to regulator, small on direct to regulator pin, one pair at input and one at output, and one small + one larger cap at the amp/IC i want to supply with power. I did everything this way until now. Microcontrollers, audio ICs, DACs ....) |
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| janneman |
No, of course it isn't wrong. But the focus must be on whatever you are powering. If in addition you want to surround the reg with caps, sure. But it would not be the best solution if one would put the cap(s) closest to the reg, with the circuit to be powered a few inches away. If you want to do both, great.
Jan Didden |
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| Christer |
Jan,
What if we have some distance between regulator and
amp/whatever and use large caps at both ends? Isn't there
some risk of ringing due to the lead inductance inbetween?
But I guess this is a typical case where we want a
not-too-low-ESR cap? |
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| janneman |
Hmmm. Don't think there will be a problem. At the reg side, ringing *should* be adequately damped by the low Zout//cap. That cap should not have too little ESR to keep the thing, well, uhh, damped.
At the load side, you have the other cap. I think the ringing etc would come from improper termination, like end of the line left dangling. Both ends with caps would be OK, but you would want a couple of parallel caps to have good decoupling over a wide freq range.
Jan Didden |
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| Christer |
Yes, I suppose the lead inductance is perhaps often low
enough too, not to cause too much problems? Probably
this will depend a lot of the particular application too.
I just thought this was one of these cases where the obvious
answer is very obvious and simple, but at second thought
it isn't obvious if the answer is obvious. "Of course it is best
to have caps at both ends!! But wait, is it really so...?" |
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| carlosfm |
| quote: | Originally posted by janneman
Carlos,
You are right that the cap needs to be near the component. But we are not trying to decouple the regulator, we are trying to decouple the amplifier circuit. Therefore, logically, you want the cap as close as possible to the amp circuit.
If that is too far away, you may need an additional cap near the regulator to keep it stable, but that is secondary.
Jan Didden |
Jan, I meant that.
There must be a cap near the regulator.
But of course you don't take out the cap from the other chip just to put it closer to the reg.:D
Calm down, I was not generalizing on the engineers.:)
It's that I reminded of one I know, a friend of mine.
He was making an active crossover for his speakers.
He showed me once I went to his house.
His idea was to measure his speakers, because he was very worried something coud be wrong.
I said let's hear it.
The sound was not to my taste, he showed me the schematic and I said: change this 12k resistor for an 11k.
He did it, we listened again and :eek: high end.:D
He was impressed by my guess.
We couldn't stop listening to music.
But 30 minutes later we was talking again of measuring the speakers and making some changes to the crossovers.:dodgy:
Is this normal?:bawling: |
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| fdegrove |
Hi,
Christer,
| quote: | Yes, I suppose the lead inductance is perhaps often low
enough too, not to cause too much problems? |
Well, if the decoupling is done right after the reg (which is what you'd want to decouple in the first place) I don't see where any stray inductance is going to come from?
Iso an electrolytic cap you may want to try a 1/10 smaller solid tantalum cap, these should have sufficent ESR to cause no oscillation from the reg.
As Jan said, the bigger chunk of the capacitance should be close to the circuit proper, not the reg.
That's where you could try out high quality (Low ESR) caps such as metalised film.
Cheers,;) |
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| Nuuk |
Hey guys, I just wanted to report that removinig the caps from my regulated PSU actually improved the sound, not start WWIII :D
For the record, my preamp supply consists of transformer, bridge rectifier, smoothing caps and first stage of 317/337 regulation in one box which is connected to the amp with about a metre of cable.
In the amp is the second stage of regulation also using 317/337 regulators. There are 0.1 uF polypropylene caps on all the regs.
This works well but I put in the extra 220 uF caps after reading that they would decrease noise from the regulators. In fact the opposite was the case although I admit that the caps were some old cheapies that I just had lying around. ;) |
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| Christer |
| quote: | Originally posted by fdegrove
Well, if the decoupling is done right after the reg (which is what you'd want to decouple in the first place) I don't see where any stray inductance is going to come from?
|
I was probably thinking wrong. I didn't write down any
equations or anything. The idea was that if we have one
cap at each end we could have an energy flowing forth and
back between these caps. Maybe the inductance would
rather work as a damper in this case?? Never mind. The
main point was, I guess, that one should question also
the simplest and most obvious things once in a while, to
see if they are simple and obvious.
| quote: | Originally posted by Nuuk
Hey guys, I just wanted to report that removinig the caps from my regulated PSU actually improved the sound, not start WWIII :D
|
Just wait till the electrolytics start exploding. :bomb: :) |
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| janneman |
| quote: | Originally posted by carlosfm
Jan, I meant that.
There must be a cap near the regulator.
But of course you don't take out the cap from the other chip just to put it closer to the reg.:D
Calm down, I was not generalizing on the engineers.:)
It's that I reminded of one I know, a friend of mine.
He was making an active crossover for his speakers.
He showed me once I went to his house.
His idea was to measure his speakers, because he was very worried something coud be wrong.
I said let's hear it.
The sound was not to my taste, he showed me the schematic and I said: change this 12k resistor for an 11k.
He did it, we listened again and :eek: high end.:D
He was impressed by my guess.
We couldn't stop listening to music.
But 30 minutes later we was talking again of measuring the speakers and making some changes to the crossovers.:dodgy:
Is this normal?:bawling: |
Carlos,
I'm impressed. You're way above anyone of us.
Jan Didden |
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| till |
"Is this normal?"
its a well known and very common effect at this place. it is related to narcism, autosuggestion, imagination. some neuroleptica may help against audiophile-mania. |
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| carlosfm |
| quote: | Originally posted by janneman
Carlos,
I'm impressed. You're way above anyone of us.
Jan Didden |
Joking?:dodgy:
You don't know the circuit I was talking about, so why comment?
Just op-amps, nothing special.
If you listened to that I thing and with the circuit at hand you would probably give the same suggestion.
You understand my words as you like, I was joking but at the same time telling a real situation.
A madness that some people have to measure everything.
I'm not above anyone, I think that YOU think you are.
I don't want a fight with anybody, I take this as a hobby and you're a professional.
Either way we all learn here, including me, including YOU.
I hope you have the honesty to admit this.
Yes, even the genious have always something to learn.
Otherwise they wouldn't come here loose their time.
:angel: |
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| till |
| carlos, thanks for your precious time. |
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| carlosfm |
till, read the post more carefully.
The genious are the others, not me.
We have very important contributions in this forum, and I mean that even those have something to learn in sharing experiences.
Am I talking english or what?:bawling: |
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| till |
| some of you postings read like you think you are the one. |
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| carlosfm |
No.
No way.:whazzat:
Maby because english is not my native language I may sometimes be misunderstood, but who knows me a little better will understand I don't ever claim that.
When I'm absolutely sure I say it, but when I'm not, I may make a suggestion.
I made a suggestion to Nuuk and this degenerated in some guys making jokes, but they DON'T EVER GIVE THE ANSWER.
It's like saying that it doesn't work, and don't say how it should be done.
Some people here would be good in politics.:clown: |
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| janneman |
| quote: | Originally posted by carlosfm
Joking?:dodgy:
You don't know the circuit I was talking about, so why comment?
Just op-amps, nothing special.
If you listened to that I thing and with the circuit at hand you would probably give the same suggestion.
You understand my words as you like, I was joking but at the same time telling a real situation.
A madness that some people have to measure everything.
I'm not above anyone, I think that YOU think you are.
I don't want a fight with anybody, I take this as a hobby and you're a professional.
Either way we all learn here, including me, including YOU.
I hope you have the honesty to admit this.
Yes, even the genious have always something to learn.
Otherwise they wouldn't come here loose their time.
:angel: |
Carlos,
Be reasonable. You look into a piece of equipment, you just say: change this from 12k to 11k and the circuit transforms from bad to hi-end. That IS impressive. I'm not a professional engineer, I wish I had your abilities. So, what's your problem? I mean, this WAS a true story, no?
Jan Didden |
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| Christer |
Carlos,
The reason I made the joke in the first place was that I
thought you were trying to be funny. I understand that
your recommendation was serious, but the way you
expressed it sounded to me as if you intended it to
sound amusing at the same time. One can be both
serious and joking at the same time.
Making small changes to component values and see what
happen can be reasonable if you have a fair idea of how
the circuit works. Any major change should be done only
after analysing the technical consequences of changing
the component. To take an extreme example, you can't
try a single op amp instead of a dual one (without
changing the PCB). Even for simple things you need to
check details. If you make a resistor smaller, will it need
to be able to handle more power? If you change it either
way, how does it affect the working conditions of other
components?
When I was some 14-15 years old, I tried to understand
how amplifiers work. I read a lot of books, but I still didn't
have the necessary understanding of math and physics to
understand it. I eventually decided to try the empirical way
of figuring out resistor values, using pots for all resistors.
I learnt two things from this experiment:
1) How to convert a TO92 BJT into one diode and the novel
one-pin collector device. :)
2) The empirical way of understanding the basics of amplifier
design doesn't work. |
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| carlosfm |
| quote: | Originally posted by janneman
Carlos,
Be reasonable. You look into a piece of equipment, you just say: change this from 12k to 11k and the circuit transforms from bad to hi-end. That IS impressive. I'm not a professional engineer, I wish I had your abilities. So, what's your problem? I mean, this WAS a true story, no?
Jan Didden |
Ok Jan, I said you don't know the circuit, why comment?
But you insist, I'll tell you.
The speakers are the crappy Kef Q7 (yes, you heard me well, CRAPPY).
The tweeter is the weak point on these speakers (uni-Q new generation metallic (titanium?) dome).
The treble doesn't go high, it's just a splash.
At 20khz these tweeters are more than 6db down.
Making an active crossover and tri-amping:eek: my friend thought it was possible to make something better out of these speakers.
His schematic was not bad at all, and it worked fine.
One of the op-amps was making a slight treble lift to account for the tweeter loss in output around 14~15khz.
And it was on this op-amp that I told him to change the resistor.
Deam, a resistor and a cap across it before an inverted op-amp is a simple circuit, don't you think?:dodgy:
Change the resistor or the cap and you're changing the treble lift, right?:dodgy:
It happens that the value I suggested him was right on spot, BECAUSE the sound I was LISTENING suggested a small correction in that direction.
Clear now?
What's impressive here? |
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| janneman |
You are. And I didn't insist on anything.
Forget it Carlos, I'm sorry I brought it up, you did a great job for your friend.
Jan Didden |
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| Jay |
| quote: | Originally posted by carlosfm
Yes, even the genious have always something to learn.
Otherwise they wouldn't come here loose their time.
:angel: |
Wrong, Carlos.
Not everyone come here to learn. Some just don't have a good social life so they think this virtual life means a great deal (and no need to tell you that it is the geniuses that usually have such a problem).
Relax, and enjoy your browsing here. As with me, I believe that what you think about me is different with what people around me think about me. And why should I care about what you think about me? You're not the one who raise my salary, are you? And I'm not dating your daughter!
Anyhow, like watching drama movies, some enjoy seeing debates and fights. So, go ahead guys :D |
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| carlosfm |
Jay,
I've seen very respected members here opening threads to ask questions about some new op-amps they haven't tried yet.
That's the point.
Exchange knowledge.
So, they aren't here loosing their time, just for fun, are they?
Anyway, don't worry, I'm relaxed and this conversation should be over now.
Anything more to say. |
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| till |
"That's the point.
Exchange knowledge.
So, they aren't here loosing their time, just for fun, are they?
Anyway, don't worry, I'm relaxed and this conversation should be over now.
Anything more to say."
Oh thanks, thats new for me.
I thought the points are: -no matter whats the topic, do have some answer and know better.
- every have the last word no matter if you have anything to say. |
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| carlosfm |
:confused:
Sorry, I don't understand what you're trying to say.
Doesn't matter.
I don't care.
Bye. |
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| matjans |
me neither. These fora have changed quite a bit, recently.
carlos, don't be put off, stay with us.
/matjans |
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| Christer |
I think this was all about making a hen out of a feather. It
started with a mutual misunderstanding between Carlos and
me and then others interferred and it all escalated for no real
reason, I think. It happens sometimes. Just to forget and go
on. |
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| carlosfm |
Thanks matjans.
I think summer is coming and we all need some vacations.:D
Just imagine, I'm now watching Rock in Rio (this year is here in Lisbon) direct on TV.
A fantastic Ben Harper concert just finished and now it's Peter Gabriel playing.:cool: |
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