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Old 3rd March 2007, 11:04 AM   #1
G is offline G  United States
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Default What voltage? What capacitance?

Hi all. I have decided to go ahead and build a GC. I would like to be able to drive a wider array of speakers rather than be limited to high efficiency ones. I am presently using a SE EL34 amplifier that I built and a tube preamplifier that I built along with a pair of Fostex full range MLTLs. If I undetand correctly the power supply caps make a large difference in how the amplifiers sound. Let me just say that I don't want "harshness" but I do want warmth and clean sound. I plan on buying one of Mr. Daniels kits and I would appreciate any suggestions on how to proceed in order to achieve a happy medium between tube sound and analitical sound. I will be driving the amp with a Foreplay (the original circuit) knockoff and later a Aikido preamp.

Has anyone tried Rubycon ZA/ZL capacitors in a gainclone?
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Old 3rd March 2007, 12:27 PM   #2
Nuuk is offline Nuuk  United Kingdom
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My advice would be a 20 VAC traffo, and try the different caps until you find the best combination. Stick with 1000uF per rail. If your speakers are a fairly 'easy' load, tha twill be plenty.
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Old 3rd March 2007, 01:49 PM   #3
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Quote:
Originally posted by Nuuk
My advice would be a 20 VAC traffo, and try the different caps until you find the best combination. Stick with 1000uF per rail. If your speakers are a fairly 'easy' load, tha twill be plenty.
Do you mean 1000uF on the PSU board or the amplifier board?
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Old 3rd March 2007, 01:57 PM   #4
Leolabs is offline Leolabs  Malaysia
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You can go for 2200uF too.
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Old 3rd March 2007, 02:15 PM   #5
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Capacitance is cheap at these low voltages. Use a lot.

Using too small capacitance will get you poor bass performance.

Look at commercial amps (not the original GC which hardly qualifies as commercial). Even cheesy, mass-market, audio junk has bigger caps in the supply than 1000 uF.

OK, so you want to be different from cheesy, mass-market, audio junk. Do you want to be better or worse?

Look at top of the line stuff from Boulder, Mark Levinson, Pass Labs, etc. Do they use tiny caps? There is a reason: you can't get decent output at low frequencies without a lot of capacitance in the power supply.

Look through threads in these forums. Complaints about poor bass performance from gain-clown amps are common. What do they have in common? Using small capacitance on the power supply rails.

Duh!

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Old 4th March 2007, 07:34 AM   #6
G is offline G  United States
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Quote:
Originally posted by I_Forgot
Capacitance is cheap at these low voltages. Use a lot.

Using too small capacitance will get you poor bass performance.

Look at commercial amps (not the original GC which hardly qualifies as commercial). Even cheesy, mass-market, audio junk has bigger caps in the supply than 1000 uF.

OK, so you want to be different from cheesy, mass-market, audio junk. Do you want to be better or worse?

Look at top of the line stuff from Boulder, Mark Levinson, Pass Labs, etc. Do they use tiny caps? There is a reason: you can't get decent output at low frequencies without a lot of capacitance in the power supply.

Look through threads in these forums. Complaints about poor bass performance from gain-clown amps are common. What do they have in common? Using small capacitance on the power supply rails.

Duh!

I_F
I have read a lot of posts, by people with no reason to lie, that too much capacitance makes the chips sound bad. Calling them "gain-clowns" seems rather childish. If you don't like them then what are you doing posting on this board?
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Old 4th March 2007, 08:23 AM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
I too am biased in favour of discrete but try to offer a balanced view.

I-forgot is correct when he repeats the lack of good strong, but not exaggerated bass, complaints when most chipamps builders follow the "sound good" advice (=small caps).

If you want a wideband amplifier that can cover the whole audio frequency range at upto maximum power then typical 1mF to 1.5mF of smoothing caps will not cut it.

If you want good treble and good midband then the small caps seem to work. This relies heavily on the short time scale of much of the transient signals and that when bass is removed from the whole audio signal the average output is even lower than the typical -20db. I guess it could be as little as -30db below peak (rms) level.

If you were to separate the two functions: driving the upper & lower bass from driving the mid & treble then I believe you can get the best out of the chipamps. It would also ease the loading on each of the chipamps by only having to drive half the crossover, allowing the chipamps to run cooler.

I have noticed that the builders who recommend and use regulated supplies for the chipamps rarely complain of a lack of bass and presumably they still find the mid & treble acceptable. I think it is no coincidence that the regulated supplies have by comparison massive smoothing and low output impedance (although in general still less than an equivalent discrete design).
It is the low PSU output impedance over the whole audio frequency range and beyond that the small caps cannot achieve.
It also appears that the chipamp responds to PSU tuning, that's what all the bypassing/decoupling and snubbers are doing.

Some threads have shown that the chipamps are very susceptible to environmental conditions, even to the extent that a recent thread is discussing the type of metallic/nonmetallic/no case and it's effect on the sound quality. I suspect this is down to vibration and damping and it seems to extend to whether the chip is the isolated or non-isolated version.

Here I will show my colours, avoid all this tuning and potential for getting it wrong and go discrete.
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Old 4th March 2007, 01:10 PM   #8
jaycee is offline jaycee  United Kingdom
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My own gainclone works pretty much as a discrete amp would.. there's 4x4700uF capacitors feeding both channels (thats 2x4700uF per rail), and then on the amp board itself, close to the IC, there's 470uF Panasonic FC's, and 100nF polyesters.

I'm using 25V rails and it sounds good driving my Eltax Liberty speakers. Not the best, but not bad considering the simplicity and price - certainly better than many low end offerings i've heard
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Old 4th March 2007, 06:19 PM   #9
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Quote:
Originally posted by G
I have read a lot of posts, by people with no reason to lie, that too much capacitance makes the chips sound bad. Calling them "gain-clowns" seems rather childish. If you don't like them then what are you doing posting on this board?
No reason to lie is one thing. Not knowing any better is another. Being deluded is yet another. Knowing what you are talking about is yet another.

Who says I don't like chip based amps? My everyday, listening-all-the-time-amp is an LM3886 based. I built it myself using a schematic from the NS data sheet/app note. See it here: http://mark.rehorst.com/LM3886_amp/index.htm
I used about 100k uF in the power supply (I can't recall if the caps cost $4 or $8 for all of them). The amp drives Quad ESL-63 apeakers, not legendary for their bass output, but the system sounds great. No complaints about weak bass.

Taking offense at calling them gain-clowns tells me you take all this nonsense much too seriously. It's just an amplifier. I think the idea of using tiny capacitors in the power supply is cute, and fun, like a toy. I find the idea of people who consider themselves serious audiophiles sitting in their rooms listening to such amps and thinking that they are hi-fi amusing, too. All this fun and the word "clone" makes me think of fun things like clowns.

You posted for advice, and received it. If you don't like advice that doesn't reinforce your prejudices, you should ask only for advice that does. Maybe you should have used this as the subject: "Requesting capacitor advice from true believers" or something similar. I would never respond to that.

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Old 4th March 2007, 06:47 PM   #10
sek is offline sek  Germany
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Guys, note that even clowns don't mean fun to everyone!

I also support the larger capacitance route. I also happen to use 2x4.700uF per channel with two channels (LM3886) on a 2x22V transformer. It sounds and measures better than the low capacitance version (2x1000u per channel), because the equivalent series resistance and inductance (and their compensation or the lack thereof) determine the sonic influence to an audible degree, not the actual capacitance value. And you bet I already skimped on capacitor cost with that arrangement (because no bass channel is involved).

The 1000uF idea was for the LM3875, a similar but different amplifier. It was an idea by an - how do I put that appropriately (?!) - elderly Japanese master with a very own kind of ideals of minimalism and simplicity. The man (Junji Kimura) designs all his stuff only for the purpose of simplicity (not versatility) and listens to strictly only classical music.

His gaincard had then been cloned and resembled by believers and non-believers. The reason why there emerged sophisticated large capacitance value power supply projects for LM3886 based amps is because it really makes a difference. For almost everyone besides Mr. Junji Kimura and some believers.

Hope this helps,
Sebastian.
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