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Dave's crap pre amp comparison

Postby turbodave » Thu May 09, 2013 7:45 pm

Hi All, Very soon I shall release a paper explaining my methods in detail. This paper shall take the form of a matchbox bottom. Suffice to say I recorded myself singing "sometimes I feel like a motherless child" by Paul Robeson, twice.
The first time through my spanking new ISA one digital via the optic cable and into the HD24. The second through my considerably cheaper (per pre amp) Octopre ,through the optic cable and into the HD 24. Both takes using my Neumann KMS 105. These then came out of the HD24 into my desk with both channels set neutrally and into my Genny 8020s.
I made sure that the levels going into the HD24 were as close as possible both through gain and proximity.
THE RESULTS------------NO DIFFERENCE ( only kidding).....Definite difference!!! The ISA one sounds comparatively, like a veil has been removed...not a thick veil, but like a spiders web has been sonically blown away (aah! the poetry). Now I know the Octopre ain't great but I have always been relatively happy with it.....I will now notice its shortcomings Dave...ps any questions about my methods, please phone my doctor.
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Re: Dave's crap pre amp comparison

Postby BJG145 » Thu May 09, 2013 8:56 pm

...ambulance is on the way...
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Re: Dave's crap pre amp comparison

Postby turbodave » Thu May 09, 2013 9:15 pm

BJG145 wrote:...ambulance is on the way...
Ta!
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Re: Dave's crap pre amp comparison

Postby Hugh Robjohns » Thu May 09, 2013 10:23 pm

:D
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Re: Dave's crap pre amp comparison

Postby Fran Guidry » Sat May 11, 2013 8:05 pm

turbodave wrote:Hi All, Very soon I shall release a paper explaining my methods in detail. This paper shall take the form of a matchbox bottom. Suffice to say I recorded myself singing "sometimes I feel like a motherless child" by Paul Robeson, twice.
The first time through my spanking new ISA one digital via the optic cable and into the HD24. The second through my considerably cheaper (per pre amp) Octopre ,through the optic cable and into the HD 24. Both takes using my Neumann KMS 105. These then came out of the HD24 into my desk with both channels set neutrally and into my Genny 8020s.
I made sure that the levels going into the HD24 were as close as possible both through gain and proximity.
THE RESULTS------------NO DIFFERENCE ( only kidding).....Definite difference!!! The ISA one sounds comparatively, like a veil has been removed...not a thick veil, but like a spiders web has been sonically blown away (aah! the poetry). Now I know the Octopre ain't great but I have always been relatively happy with it.....I will now notice its shortcomings Dave...ps any questions about my methods, please phone my doctor.

I only respond here because because I hope to restore your happiness with the Octopre .

First, have you considered that the electronics, with vanishingly low distortion and nearly perfect frequency response, are certainly more consistent than your two performances?

Second, are you aware of the degree to which minute volume changes are interpreted as quality differece? Specifically "veils lifting" type differences. Your "close as possible" level matching, if done without test tones and careful metering, is far far from "close enough" to give a meaningful result.

Third, do you understand the crucial importance of blinding in comparisons like this? We all like to think that we can override our cognitive/perceptual biases, but in fact they occur below the level of consciousness and are unavailable to our will. If you can see the label, you are screwed when it comes to making valid comparisons.

Start your test over. Use a single mic, dynamic or self-powered, through a passive splitter and into both preamps at the same time. Using a 1 khz test tone, match the levels to better than .1 dB. Do a single performance into both preamps at the same time. Put the resulting clips into a double blind ABX comparator like the one in foobar2000. Can you correctly identify the clips 13 times out of 16 trials? If so, you can hear a difference to a high probability and have a basis to make a reasonable judgment. If not, no audible difference. And I'd put my money on the latter.

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Re: Dave's crap pre amp comparison

Postby hugol » Sat May 11, 2013 8:25 pm

Fran Guidry wrote:
First, have you considered that the electronics, with vanishingly low distortion and nearly perfect frequency response, are certainly more consistent than your two performances?


Completely sensible post Fran - and I'm thinking the same thing as you about needing to be scientific and compare the exact same take. However just questioning whether these two pre-amps are both really aiming to be as neutral and linear as possible? The ISA One makes a big deal about being transformer based, whether this transformer imparts a noticeable sonic signature I don't know - but transformers have that reputation don't they?
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Re: Dave's crap pre amp comparison

Postby Exalted Wombat » Sat May 11, 2013 8:38 pm

turbodave wrote:THE RESULTS------------NO DIFFERENCE ( only kidding).....Definite difference!!! The ISA one sounds comparatively, like a veil has been removed...not a thick veil, but like a spiders web has been sonically blown away (aah! the poetry). Now I know the Octopre ain't great but I have always been relatively happy with it.....I will now notice its shortcomings Dave...ps any questions about my methods, please phone my doctor.


You've left out: "My wife came into the room and, without prompting, asked what I'd done to make my voice sound so much better!" :-)
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Re: Dave's crap pre amp comparison

Postby turbodave » Sun May 12, 2013 12:11 am

Fran Guidry wrote:
turbodave wrote:Hi All, Very soon I shall release a paper explaining my methods in detail. This paper shall take the form of a matchbox bottom. Suffice to say I recorded myself singing "sometimes I feel like a motherless child" by Paul Robeson, twice.
The first time through my spanking new ISA one digital via the optic cable and into the HD24. The second through my considerably cheaper (per pre amp) Octopre ,through the optic cable and into the HD 24. Both takes using my Neumann KMS 105. These then came out of the HD24 into my desk with both channels set neutrally and into my Genny 8020s.
I made sure that the levels going into the HD24 were as close as possible both through gain and proximity.
THE RESULTS------------NO DIFFERENCE ( only kidding).....Definite difference!!! The ISA one sounds comparatively, like a veil has been removed...not a thick veil, but like a spiders web has been sonically blown away (aah! the poetry). Now I know the Octopre ain't great but I have always been relatively happy with it.....I will now notice its shortcomings Dave...ps any questions about my methods, please phone my doctor.

I only respond here because because I hope to restore your happiness with the Octopre .

First, have you considered that the electronics, with vanishingly low distortion and nearly perfect frequency response, are certainly more consistent than your two performances?

Second, are you aware of the degree to which minute volume changes are interpreted as quality differece? Specifically "veils lifting" type differences. Your "close as possible" level matching, if done without test tones and careful metering, is far far from "close enough" to give a meaningful result.

Third, do you understand the crucial importance of blinding in comparisons like this? We all like to think that we can override our cognitive/perceptual biases, but in fact they occur below the level of consciousness and are unavailable to our will. If you can see the label, you are screwed when it comes to making valid comparisons.

Start your test over. Use a single mic, dynamic or self-powered, through a passive splitter and into both preamps at the same time. Using a 1 khz test tone, match the levels to better than .1 dB. Do a single performance into both preamps at the same time. Put the resulting clips into a double blind ABX comparator like the one in foobar2000. Can you correctly identify the clips 13 times out of 16 trials? If so, you can hear a difference to a high probability and have a basis to make a reasonable judgment. If not, no audible difference. And I'd put my money on the latter.

Fran
Thanks Fran....you will not know this but my ears are %ucked! Fortunately they are consistently %ucked and so I can detect differences through my already present veil of tinnitus/hiss and nagging! There is a difference in the sound between these two pre amps....yes I know, you don't want to hear it, but just as a clementine has a warmer midrange than a satsuma, so my ISA one has a more forward mid range (tartiness), which I think is more pleasant to the human ear. The Octopre is still great for the price, but I hear a midrange "thrust" with the ISA that I don't hear with the Octopre....and without added noise, that relatively the Octopre possesses more of. Maybe my ears ain't so bad!! ....and Wombat!...you know my wife ain't interested...its not the quality of the voice, but the 5hit I speak! Dave
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Re: Dave's crap pre amp comparison

Postby Exalted Wombat » Sun May 12, 2013 11:58 am

So the next job is to see if you can reproduce this mid-range difference with some simple eq. Never choose an expensive solution, if there's an existing cheap one!

It ain't about the gear.
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Re: Dave's crap pre amp comparison

Postby Martin Walker » Sun May 12, 2013 1:30 pm

Fran Guidry wrote:Using a 1 khz test tone, match the levels to better than .1 dB. Do a single performance into both preamps at the same time. Put the resulting clips into a double blind ABX comparator like the one in foobar2000. Can you correctly identify the clips 13 times out of 16 trials? If so, you can hear a difference to a high probability and have a basis to make a reasonable judgment.

I use to adopt this procedure (against a benchmark) whenever I tested an audio interface for SOS.

And you tell the kids today... :beamup:


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Re: Dave's crap pre amp comparison

Postby turbodave » Sun May 12, 2013 6:56 pm

Exalted Wombat wrote:So the next job is to see if you can reproduce this mid-range difference with some simple eq. Never choose an expensive solution, if there's an existing cheap one!

It ain't about the gear.
Aye, and the added hiss that would accompany it! ;)
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Re: Dave's crap pre amp comparison

Postby Exalted Wombat » Sun May 12, 2013 7:06 pm

turbodave wrote:
Exalted Wombat wrote:So the next job is to see if you can reproduce this mid-range difference with some simple eq. Never choose an expensive solution, if there's an existing cheap one!

It ain't about the gear.
Aye, and the added hiss that would accompany it! ;)

Yeah, that midrange hiss can be a bugger!
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Re: Dave's crap pre amp comparison

Postby turbodave » Sun May 12, 2013 10:07 pm

You ain't got my desk!
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Re: Dave's crap pre amp comparison

Postby Exalted Wombat » Sun May 12, 2013 10:52 pm

Well, get a £100 Behringer then. They're pretty quiet.
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Re: Dave's crap pre amp comparison

Postby turbodave » Mon May 13, 2013 6:56 am

Ha! Get the wool out your ears Mr. Wombat. I refer the honourable gentleman to the title of this thread. :headbang: Dave
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