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-10 to +4 conversion: analog or digital?

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Anonymous
June 15, 2005 1:47:44 AM

Archived from groups: rec.audio.pro (More info?)

I just borrowed a Tascam 238 cassette 8-track from a friend to transfer some
old recordings I have. I'm playing them on the 238 which has consumer-level
outputs, and recording them into an Alesis HD24 with pro-level inputs.

Is there any significant sonic advantage to raising the signal level in the
analog domain rather than doing so digitally after the A/D conversion? It
seems to me that I'd be amplifying the noise floor the same in either case,
but I don't understand the technical details well enough to know whether or
not that assumption is correct.

Hal Laurent
Baltimore

P.S. I have two Tascam 238 decks lying around here whose transports don't
function properly (one makes horrible noises, and the other doesn't run at
the correct speed). I also have the service manual, but not the knowledge
to use it. If anyone has a perverse interest in these things, I'll let you
have them and the manual for the cost of shipping.
Anonymous
June 15, 2005 11:09:16 AM

Archived from groups: rec.audio.pro (More info?)

"Hal Laurent" <laurent@charm.net> wrote in message
news:4NLre.2$C6.477@news.abs.net...
> I just borrowed a Tascam 238 cassette 8-track from a friend to transfer
some
> old recordings I have. I'm playing them on the 238 which has
consumer-level
> outputs, and recording them into an Alesis HD24 with pro-level inputs.
>
> Is there any significant sonic advantage to raising the signal level in
the
> analog domain rather than doing so digitally after the A/D conversion? It
> seems to me that I'd be amplifying the noise floor the same in either
case,
> but I don't understand the technical details well enough to know whether
or
> not that assumption is correct.

Essentially yes, or at least close enough that no one will ever know the
difference.

In theory, every time you perform an operation on an audio file there is
some degradation, albeit small. Considering what you're starting with, I'd
say go ahead and do it in the digital domain, or hell, just leave them where
they are . So they're 12 dB below maximum, you still are working with a
22-bit signal, which is a copy of a cassette.

Peace,
Paul
Anonymous
June 15, 2005 11:56:06 AM

Archived from groups: rec.audio.pro (More info?)

Hal Laurent wrote:

> I just borrowed a Tascam 238 cassette 8-track from a
friend to
> transfer some old recordings I have. I'm playing them on
the 238
> which has consumer-level outputs, and recording them into
an Alesis
> HD24 with pro-level inputs.

> Is there any significant sonic advantage to raising the
signal level
> in the analog domain rather than doing so digitally after
the A/D
> conversion?

That would depend on the details of the actual process.
Given the quality of this particular source (low) and this
particular digital recorder (pretty good), probably not a
problem.

> It seems to me that I'd be amplifying the noise floor
> the same in either case, but I don't understand the
technical details
> well enough to know whether or not that assumption is
correct.

If the source were higher quality, and/or the recorder had
lower quality, then you'd be amplifying the noise floor of
the recorder. But since the source is of low quality, and
the recorder is presumably of a far higher quality, you're
amplifying the noise floor of the source which is the best
that you can possibly do.

I've had some great luck cleaning up consumer-grade tapes
with the hiss reduction facility in Audition/CE. The noise
floor went way down, but the music seems to be largely
unaffected.
Related resources
Anonymous
June 15, 2005 1:30:29 PM

Archived from groups: rec.audio.pro (More info?)

Hal Laurent wrote:
> I just borrowed a Tascam 238 cassette 8-track from a friend to transfer some
> old recordings I have. I'm playing them on the 238 which has consumer-level
> outputs, and recording them into an Alesis HD24 with pro-level inputs.
>
> Is there any significant sonic advantage to raising the signal level in the
> analog domain rather than doing so digitally after the A/D conversion? It
> seems to me that I'd be amplifying the noise floor the same in either case

In theory, it depends on whether the noise level from the 8-track is
higher or lower than the quantization level of the Alesis.

In practice, we're talking about 8-track cassette and a 24 bit digital
input. Even allowing for the difference in levels, the noise from a
cassette tape is going to be way above the quantization noise of a 24
bit converter.

So you might as well do it digitally if it's easier.

Anahata
Anonymous
June 15, 2005 1:41:26 PM

Archived from groups: rec.audio.pro (More info?)

Hal Laurent <laurent@charm.net> wrote:
>I just borrowed a Tascam 238 cassette 8-track from a friend to transfer some
>old recordings I have. I'm playing them on the 238 which has consumer-level
>outputs, and recording them into an Alesis HD24 with pro-level inputs.
>
>Is there any significant sonic advantage to raising the signal level in the
>analog domain rather than doing so digitally after the A/D conversion? It
>seems to me that I'd be amplifying the noise floor the same in either case,
>but I don't understand the technical details well enough to know whether or
>not that assumption is correct.

That is correct. You're getting less dynamic range in the conversion
than you otherwise would, but given that the source doesn't have much
dynamic range to begin with, you're home free.

>P.S. I have two Tascam 238 decks lying around here whose transports don't
>function properly (one makes horrible noises, and the other doesn't run at
>the correct speed). I also have the service manual, but not the knowledge
>to use it. If anyone has a perverse interest in these things, I'll let you
>have them and the manual for the cost of shipping.

Take them to Washington Professional and have them fix them. Those should
be easy fixes, and those guys will probably enjoy working on something
mechanical for a change.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 15, 2005 1:41:32 PM

Archived from groups: rec.audio.pro (More info?)

In article <4NLre.2$C6.477@news.abs.net> laurent@charm.net writes:

> Is there any significant sonic advantage to raising the signal level in the
> analog domain rather than doing so digitally after the A/D conversion? It
> seems to me that I'd be amplifying the noise floor the same in either case,
> but I don't understand the technical details well enough to know whether or
> not that assumption is correct.

If you amplify it digitally, you'll also be amplifying the low level
errors which are present to some extent in all A/D converters. But to
be practical, there's probably enough hiss on the tape to cover up
that detail anyway.

But when I do this sort of thing, I always run through the console and
get the level right at the destination. Less to fool with when (or if)
I ever work with it.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
June 15, 2005 1:41:33 PM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:
> In article <4NLre.2$C6.477@news.abs.net> laurent@charm.net writes:
>
> > Is there any significant sonic advantage to raising the signal level in the
> > analog domain rather than doing so digitally after the A/D conversion? It
> > seems to me that I'd be amplifying the noise floor the same in either case,
> > but I don't understand the technical details well enough to know whether or
> > not that assumption is correct.
>
> If you amplify it digitally, you'll also be amplifying the low level
> errors which are present to some extent in all A/D converters. But to
> be practical, there's probably enough hiss on the tape to cover up
> that detail anyway.
>
> But when I do this sort of thing, I always run through the console and
> get the level right at the destination. Less to fool with when (or if)
> I ever work with it.
>

This would also give you the opportunity to do some gentle overall EQ
to "prepare" the audio before transcription. Of course you may wish to
do that in the digital domain as well... probably won't make much
difference considering the source.

Karl Winkler
Lectrosonics, Inc.
http://www.lectrosonics.com
Anonymous
June 15, 2005 3:24:30 PM

Archived from groups: rec.audio.pro (More info?)

Mike Rivers wrote:

> If you amplify it digitally, you'll also be amplifying the
low level
> errors which are present to some extent in all A/D
converters. But to
> be practical, there's probably enough hiss on the tape to
cover up
> that detail anyway.

Point of order, there are no such things as low-level errors
in modern A/D converters. Yes there are errors, but they are
equally present at all levels.
Anonymous
June 15, 2005 3:30:00 PM

Archived from groups: rec.audio.pro (More info?)

In article <jtGdneISSeaw1S3fRVn-1Q@comcast.com>,
Arny Krueger <arnyk@hotpop.com> wrote:
>Mike Rivers wrote:
>
>> If you amplify it digitally, you'll also be amplifying the
>low level
>> errors which are present to some extent in all A/D
>converters. But to
>> be practical, there's probably enough hiss on the tape to
>cover up
>> that detail anyway.
>
>Point of order, there are no such things as low-level errors
>in modern A/D converters. Yes there are errors, but they are
>equally present at all levels.

I'm not sure I buy that quite yet. Arny, how about doing a plot of
distortion spectrum vs. level on a couple of soundcards? I think it
would be an interesting exercise.

I agree that the low level distortion issue of the eighties is long
gone, but I'm not sure I believe the spectrum and level will be constant
with amplitude right yet.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 15, 2005 3:38:23 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> In article <jtGdneISSeaw1S3fRVn-1Q@comcast.com>,
> Arny Krueger <arnyk@hotpop.com> wrote:
>> Mike Rivers wrote:
>>
>>> If you amplify it digitally, you'll also be amplifying
the
>> low level
>>> errors which are present to some extent in all A/D
>> converters. But to
>>> be practical, there's probably enough hiss on the tape
to
>> cover up
>>> that detail anyway.
>>
>> Point of order, there are no such things as low-level
errors
>> in modern A/D converters. Yes there are errors, but they
are
>> equally present at all levels.
>
> I'm not sure I buy that quite yet. Arny, how about doing
a plot of
> distortion spectrum vs. level on a couple of soundcards?
I think it
> would be an interesting exercise.

See www.pcavtech.com


I think just about every report shows 1 KHz @ close to FS
and also at -60 dB.

Compare:

"1 kHz Total Harmonic Distortion"

to

"Residual Noise - (Dynamic Range)"

Example:


http://www.pcavtech.com/soundcards/LynxTWO/index.htm


> I agree that the low level distortion issue of the
eighties is long
> gone, but I'm not sure I believe the spectrum and level
will be
> constant with amplitude right yet.

Generally, there is less absolute magnitude distortion at
lower levels.
Anonymous
June 15, 2005 4:30:08 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" <kludge@panix.com> wrote in message
news:D 8pb66$m7q$1@panix2.panix.com...
> Hal Laurent <laurent@charm.net> wrote:
>
>>P.S. I have two Tascam 238 decks lying around here whose transports don't
>>function properly (one makes horrible noises, and the other doesn't run at
>>the correct speed). I also have the service manual, but not the knowledge
>>to use it. If anyone has a perverse interest in these things, I'll let
>>you
>>have them and the manual for the cost of shipping.
>
> Take them to Washington Professional and have them fix them. Those should
> be easy fixes, and those guys will probably enjoy working on something
> mechanical for a change.

I thought about that (they worked on one of them a number of years ago). It
would likely cost more to repair them than they're worth nowadays, though,
and I don't have any use for them myself once I get the old tapes
transferred.

Hal Laurent
Baltimore
Anonymous
June 15, 2005 6:32:55 PM

Archived from groups: rec.audio.pro (More info?)

In article <lIYre.8$gF.64@news.abs.net>, Hal Laurent <laurent@charm.net> wrote:
>"Scott Dorsey" <kludge@panix.com> wrote in message
>news:D 8pb66$m7q$1@panix2.panix.com...
>> Hal Laurent <laurent@charm.net> wrote:
>>
>>>P.S. I have two Tascam 238 decks lying around here whose transports don't
>>>function properly (one makes horrible noises, and the other doesn't run at
>>>the correct speed). I also have the service manual, but not the knowledge
>>>to use it. If anyone has a perverse interest in these things, I'll let
>>>you
>>>have them and the manual for the cost of shipping.
>>
>> Take them to Washington Professional and have them fix them. Those should
>> be easy fixes, and those guys will probably enjoy working on something
>> mechanical for a change.
>
>I thought about that (they worked on one of them a number of years ago). It
>would likely cost more to repair them than they're worth nowadays, though,
>and I don't have any use for them myself once I get the old tapes
>transferred.

If you're pitching them, I'll take one to have as a parts machine, but
you never know when you might need one.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 15, 2005 8:09:42 PM

Archived from groups: rec.audio.pro (More info?)

In article <jtGdneISSeaw1S3fRVn-1Q@comcast.com> arnyk@hotpop.com writes:

> Point of order, there are no such things as low-level errors
> in modern A/D converters. Yes there are errors, but they are
> equally present at all levels.

Oh, you know what I mean - the stuff that sounds nasty when things get
quiet.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
June 16, 2005 1:58:05 PM

Archived from groups: rec.audio.pro (More info?)

On Wed, 15 Jun 2005 09:41:32 -0400, Mike Rivers wrote
(in article <znr1118834742k@trad>):

>
> In article <4NLre.2$C6.477@news.abs.net> laurent@charm.net writes:
>
>> Is there any significant sonic advantage to raising the signal level in the
>> analog domain rather than doing so digitally after the A/D conversion? It
>> seems to me that I'd be amplifying the noise floor the same in either case,
>> but I don't understand the technical details well enough to know whether or
>> not that assumption is correct.
>
> If you amplify it digitally, you'll also be amplifying the low level
> errors which are present to some extent in all A/D converters. But to
> be practical, there's probably enough hiss on the tape to cover up
> that detail anyway.


Hmmm, DITHER.

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
Anonymous
June 16, 2005 2:37:28 PM

Archived from groups: rec.audio.pro (More info?)

Ty Ford wrote:
> On Wed, 15 Jun 2005 09:41:32 -0400, Mike Rivers wrote
> (in article <znr1118834742k@trad>):
>
>>
>> In article <4NLre.2$C6.477@news.abs.net>
laurent@charm.net writes:
>>
>>> Is there any significant sonic advantage to raising the
signal
>>> level in the analog domain rather than doing so
digitally after the
>>> A/D conversion? It seems to me that I'd be amplifying
the noise
>>> floor the same in either case, but I don't understand
the technical
>>> details well enough to know whether or not that
assumption is
>>> correct.
>>
>> If you amplify it digitally, you'll also be amplifying
the low level
>> errors which are present to some extent in all A/D
converters. But to
>> be practical, there's probably enough hiss on the tape to
cover up
>> that detail anyway.
>
>
> Hmmm, DITHER.

Exactly. It's impossible for a properly-dithered system to
have detail problems at just low levels.
Anonymous
June 16, 2005 3:03:20 PM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger <arnyk@hotpop.com> wrote:
>
>Exactly. It's impossible for a properly-dithered system to
>have detail problems at just low levels.

Unless the analogue section that is driving it has a crossover distortion
issue. Remember a lot of the "conversion" problems today actually have to
do with the analogue stuff in front of the converters.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
June 16, 2005 4:08:12 PM

Archived from groups: rec.audio.pro (More info?)

Scott Dorsey wrote:
> Arny Krueger <arnyk@hotpop.com> wrote:
>>
>> Exactly. It's impossible for a properly-dithered system
to
>> have detail problems at just low levels.
>
> Unless the analogue section that is driving it has a
crossover
> distortion issue. Remember a lot of the "conversion"
problems today
> actually have to do with the analogue stuff in front of
the
> converters. --scott

<guardhouse lawyer's hat on>

Your point is taken Scott, but it violates the condition I
stated:

"a properly-dithered system".

The analog section would be part of the system. If the
system was well-dithered, the dither would be applied prior
to the analog section and its crossover distortion. The
dither would effectively linearize the crossover distortion
along with any other low-level nonlinearity.

I've applied low level noise to the input of a power amp
with audible crossover distortion, and noticed that the
noise effectively eliminated the audible artifacts due to
the crossover distortion.


<guardhouse lawyer's hat off>
Anonymous
June 17, 2005 12:38:00 AM

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:
> Scott Dorsey wrote:
>
>>Arny Krueger <arnyk@hotpop.com> wrote:
>>
>>>Exactly. It's impossible for a properly-dithered system
>
> to
>
>>>have detail problems at just low levels.
>>
>>Unless the analogue section that is driving it has a
>
> crossover
>
>>distortion issue. Remember a lot of the "conversion"
>
> problems today
>
>>actually have to do with the analogue stuff in front of
>
> the
>
>>converters. --scott
>
>
> <guardhouse lawyer's hat on>
>
> Your point is taken Scott, but it violates the condition I
> stated:
>
> "a properly-dithered system".
>
> The analog section would be part of the system. If the
> system was well-dithered, the dither would be applied prior
> to the analog section and its crossover distortion. The
> dither would effectively linearize the crossover distortion
> along with any other low-level nonlinearity.
>
> I've applied low level noise to the input of a power amp
> with audible crossover distortion, and noticed that the
> noise effectively eliminated the audible artifacts due to
> the crossover distortion.
>
>
> <guardhouse lawyer's hat off>
>
>
In other words (mine), noise is good. :) 
Anonymous
June 17, 2005 2:33:40 AM

Archived from groups: rec.audio.pro (More info?)

On Thu, 16 Jun 2005 12:08:12 -0400, "Arny Krueger" <arnyk@hotpop.com>
wrote:

>"a properly-dithered system".
>
>The analog section would be part of the system. If the
>system was well-dithered, the dither would be applied prior
>to the analog section and its crossover distortion. The
>dither would effectively linearize the crossover distortion
>along with any other low-level nonlinearity.
>
>I've applied low level noise to the input of a power amp
>with audible crossover distortion, and noticed that the
>noise effectively eliminated the audible artifacts due to
>the crossover distortion.

Maybe, but when I asked this very question here and
on comp.dsp, I got several convincing answers otherwise.

At a practical level though, a good noise floor seems
to heal a *lot* of wounds. Maybe it's just the
generation we grew up in; we're still as noisy and
divided as ever.

Thanks,

Chris Hornbeck
Anonymous
June 17, 2005 10:44:54 AM

Archived from groups: rec.audio.pro (More info?)

In article <p7v3b1td2q91g9jfg8h3fjbspo5khemrs0@4ax.com> chrishornbeckremovethis@att.net writes:

> Maybe, but when I asked this very question here and
> on comp.dsp, I got several convincing answers otherwise.

Welcome to the Internet, where everyone has an opinion as to what the
real facts are.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
!