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Old 28th November 2012, 05:40 PM   #8681
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In my opinion...
...this 'drift' in the RIAA caps...
...is not dissimilar to hooking up a very low frequency LFO ( like in a guitar 'phaser' stomp-box eg. )
Which COULD be varying the response on a long ( several seconds ) cycle of up to 3%.
I figure, without 'rattling on' too much technical BS...
...this, in an 'inverse RIAA' for example ( smaller value caps )...
...could be about equal to roughly 0.25dB 'cycling drift' at the capacitors 'frequency points'.
( less either side, of course )

Mica seems the only way forward to me.

Cheers.

Si.

Also on inverse RIAA.
Get a wire-wound for the 500,000 Ohm & 40,000 Ohm resistor, if nothing else.

Phew !!!
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Old 28th November 2012, 05:46 PM   #8682
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Quote:
Originally Posted by merlin el mago View Post
That's not a calibrate LCR, no Kelvin wire to measure, you are far to know real values are you measuring, you are just trusting matching seller without to know if is OK or not the value needed.
I do not trust the seller´s measurements, that is why I measure all caps myself using a calibrated measurement.

Quote:
Originally Posted by AndrewT View Post
Merlin, you are wrong !

If the two caps, one 20% tolerance and one 1% tolerance are measured and found to be close to an exact match, say within 0.1% then you KNOW that both capacitors are within 1.1% of true value, if you have used the same measurement procedure specified by the 1% manufacturer.
That is my opinion also.

Quote:
Originally Posted by AndrewT View Post
I have a small range of 0.3% capacitors I use to roughly calibrate my measuring procedure.
That is how I do it also.
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Old 28th November 2012, 05:47 PM   #8683
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Quote:
Originally Posted by AndrewT View Post
I have a small range of 0.3% capacitors I use to roughly calibrate my measuring procedure.
Same with my much bigger range of 0.1% resistors.

But I am aware of drift and I cannot guarantee 0.3% accuracy, maybe 1% accuracy for all my 5% and 10% and worse capacitors, if I need absolute values rather than component matching.

Most of my component matching can achieve better than 0.1% spread and sometimes if I take great care, better than 0.005% (1part in 20000 spread).
Your LCR is calibrated?
If it's calibrated more than 1 year ago needs re-calibrating?
Your LCR have 4 wires Kelvin connection?
How many time do you have the 0.3% capacitors & the 0.1% resistors?
If your need absolute values the only right way is to buy a precision LCR with 4 wires Kelvin connection & calibrated by a Lab, if not the rest of your measurements aren't valids
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Old 28th November 2012, 05:56 PM   #8684
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Merlin

I believe we are heading to an endless discussion... Anyway, I relatively trust my measurement methodology. Whenever I read a 0.3% cap or a 1% cap, the values I find are coincident.

In the end, what matters more is the relative matching between channels and that can be obtained with regular equipment.

I have listened to numerous riaa amps, some built with great discrepancies regarding Lipshitz calc, and they sound good so....
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Old 28th November 2012, 05:59 PM   #8685
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RCruz

I'm sorry if I disturbed you

Cheers
Felipe
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Old 28th November 2012, 06:04 PM   #8686
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You did not Felipe

You are very welcome, I feel you are my friend

I only did not agree with your initial idea regarding cap tolerances, but maybe you are right and I am wrong....
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Old 28th November 2012, 06:13 PM   #8687
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You are right if you match both channels with the same caps value you don't ear any difference. I only want to remark that possibly all our measurements are worng (including sellers) it's very expensive have a precision calibrated LCR only a few perosns/company have on his bench.
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Old 28th November 2012, 06:18 PM   #8688
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Quote:
Originally Posted by merlin el mago View Post
You are right if you match both channels with the same caps value you don't ear any difference. I only want to remark that possibly all our measurements are worng (including sellers) it's very expensive have a precision calibrated LCR only a few perosns/company have on his bench.
Totally agree... we can never be sure, even the 1% caps we buy can have less than perfect values.

Strangely the caps you sent me measured exactly the same with my meter.

The ones that Michael sends me are also spot on, and the ones I got from Peter (Acoustic Dimension) also have really close values to those I measure here, so I guess we are not far from the truth.
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Old 28th November 2012, 06:31 PM   #8689
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The important thing it's enjoy doing DIY.

Possible our two LCR have the same unaccuracy.

I don't know how measures Michael Percy: never asked him but seriously I doubt he have a Lab precision calibrated LCR.

P.S. we can match with a bad LCR but we can't measure well with a bad LCR....

Last edited by merlin el mago; 28th November 2012 at 06:35 PM.
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Old 28th November 2012, 06:52 PM   #8690
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Hi Ricardo

I saw your earlier post on the wire-wounds.

INDUCTANCE.
-----------------

I too was concerned about this.
But aparently this is pretty much a 'non issue', especialy compared to 'capacitor drift'.
Morgan Jones's in his book 'Valve Amplifiers' says something like...
...the inductance even of small R's ( potentialy the worst ) is all but 'insignificant' for our purposes.
Worst case, 0.5deg phase-shift @ 100Khz ( low value R ).
Manufacturers old & new, are all winding to avoid inductance anyhow.

EXPENSE.
-----------

Well...
...Yes, they are a bit expensive.
But, how much does a 'teeny-weeny' 'audiophool' resistor cost ?
I've bought a few; as much, if not alot more than a wire-wound.
How many resistors are in a 'Simplistic' anyhow ?...not many.
How many quality wire-wounds can you buy for the price of 1 'gold-plated cap' ?...
A lot.

SIZE.
-----

Yep...'size doesn't matter' ?...
...Well it does, if you're trying to 'stuff' a tiny kit PCB with them...
...problems...problems...problems...
I guess that's another reason people save 'em for valve stuff.
However, every 'Simplistic' is like the best 'prototype racing car'...
...every one, uniquely different ( but similar ), all built for MAXIMUM performance.
( That's why I like this thread ! )

So.

Why not ?

Still finding parts here...
...but we start soldering in a few more weeks, I rec.
Pictures of course, in due time.

Cheers.

Si.

Now...
...if I put the pre-amp in a vat of liquid nitrogen ( like the radio-telescope guys 'listening to outer-space do ), could I get the performance even better.
This, I'm afraid to say, is how we are thinking at 'Space Egg' on this one.

Made some 'clips', with a couple of pF's on !!!!!!!!!!!!
Nice !
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