Is an RIAA curve always desireable in a phono amp?

[muzic...@yahoo.com]

I have this Rolls VP29 Phono pre - per its housing it incorporates the RIAA curve. However it's my understanding the curve wasn't universally used in all LP recordings.

So, if a recording uses some other eq curve, how will it negatively impact the resulting output?

[Les Cargill]

muzic...@yahoo.com wrote:
> I have this Rolls VP29 Phono pre - per its housing it incorporates
> the RIAA curve. However it's my understanding the curve wasn't
> universally used in all LP recordings.
>

The RIAA curve was used for vanishingly close to "all" recordings.

> So, if a recording uses some other eq curve, how will it negatively
> impact the resulting output?
>

It'll sound like the RIAA curve only too much so. There's a picture
at the Wikipedia page.

--
Les Cargill

[Trevor]

<muzic...@yahoo.com> wrote in message
news:112fcef6-b74c-4836...@googlegroups.com...

The playback frequency response will be wrong obviously. That's likely to be
the case for most 78's. But if you are recording to digital rather than
listening, you are better using RIAA and adjusting from there in post, than
recording flat, if you don't have the proper pre-amp EQ's necessary. For
those doing a lot of 78 listening, they usually buy one that is adjustable.

Trevor.

[William Sommerwerck]

LPs have always used some form of bass cut and treble boost. There were
several curves, usually proprietary to specific companies. In 1955, the RIAA
introduced a cut/boost curve intended to be the standard for all record
companies.

Recordings made with other curves will show bass and treble "shelving" -- the
response won't be flat.

[William Sommerwerck]

When I said "recording", I meant the LP itself. The curve is applied when
mastering the disk. It is never a part of the original recording.

[geoff]

<muzic...@yahoo.com> wrote in message
news:112fcef6-b74c-4836...@googlegroups.com...

LP 'pressings' that is.

You have some extremely rare odd recordings ? If not, 99% if not 99.9% will
require RIAA. I don't think I've ever heard of a phono preamp without RIAA.

geoff

[Adrian Tuddenham]

<muzic...@yahoo.com> wrote:

> I have this Rolls VP29 Phono pre - per its housing it incorporates the
> RIAA curve. However it's my understanding the curve wasn't universally
> used in all LP recordings.

Early L.P.s used an assortment of different curves until the RIAA
standard was established. Some of them used the RIAA curve but called
it something else.

Almost no 78s used the RIAA curve, so you can guarantee that your
pre-amp will be unsuitable for playing older recordings. There were
also 33.3 rpm coarse groove discs before commercial L.P.s, and these did
not use RIAA either. If you really dig around , you will find discs
with vertical modulation (hill & dale), speeds up to 120 rpm and
diameters up to 21", but the pre-amp will be the least of your problems
if you want to play any of those formats.


More information in Chapter 6 of:

http://www.bl.uk/reshelp/findhelprestype/sound/anaudio/analoguesoundrest
oration.pdf



--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

[PStamler]

As others have said, some LPs recorded before 1955 used curves other than RIAA, and most 78s did. Play them back with an RIAA preamp and you'll get errors in frequency response, correctable with shelving EQ.

Now about playing back flat: I used to think it was a dubious idea. But a couple of years ago I modified the preamp I use for playing back 78s to be switchable to flat response (because I was working on a bunch of acoustically-recorded discs of Irish-American music), and I tried using it on electrically-recorded 78s, applying EQ in post. It turned out that my de-scratching program, DC-EIGHT, does a better job with fewer artifacts if I descratch before applying EQ, and I also like to be able to experiment with various EQ settings at my leisure without worrying about damaging the record with repeated playings. I think my 78 transfers sound a lot better now.

I've never tried the flat playback method with LPs, so I don't know if the improvement in descratching works for them too. One of these days...

Peace,
Paul

[Adrian Tuddenham]

PStamler <psta...@pobox.com> wrote:

[...]

> Now about playing back flat: I used to think it was a dubious idea. But a
> couple of years ago I modified the preamp I use for playing back 78s to be
> switchable to flat response (because I was working on a bunch of
> acoustically-recorded discs of Irish-American music), and I tried using it
> on electrically-recorded 78s, applying EQ in post.

[...]

There are advantages and disadvantages to both systems:

If the equalisation is done in the front end, it makes for a simple
cheap compact unit, but adapting it to other characteristics can be
problematical. If only a few fixed characteristics are required,
networks can be switched in and out; but when it comes to multiple or
continuously-variable characteristics, the situation becomes complicated
and prone to interactions between the various time constants. Another
hazard is the possibility that the low impedances needed in the feedback
loop for some characteristics may overload the pre-amp output stage at
high signal levels (I have only come across this problem with some of
the early discrete transistor designs).


A flat pre-amp, followed by specialised equalisation sections is a much
better way of dealing with a complex or continuously-variable situation.
Because the signal level at the equaliser is higher, several stages can
be chained without any significant noise penalty, so that each stage can
be optimised for a particular function with no risk of interacting with
other stages. Unwanted stages can be switched right out.

The flat pre-amp allows digital equalisation if this is required. It
also allows a flat digital recording to made and then replayed through
analogue equalisers, so that adjustments can be made without the risk of
damage from continuously replaying a valuable original artefact. Some
de-clickers work best if they have access to the flat signal, so they
must be interposed between the pre-amp and the equaliser.

The disadvantage is that the pre-amp and at least the first equaliser
stage must be capable of handling amplitudes and frequencies well above
the average audio level without distortion. Careful consideration must
be given to the gain distribution throughout the chain, so as to avoid
excessive signal levels on one hand or poor noise performance on the
other.

I have found that a voltage gain of x30 can be used with a Shure 44
cartridge whilst still leaving adequate headroom to avoid clipping on
the cracks of a broken shellac 78. A full power bandwidth of around 100
Kc/s is enough to handle this type of signal without slew-rate limiting.

[Scott Dorsey]

<muzic...@yahoo.com> wrote:
>I have this Rolls VP29 Phono pre - per its housing it incorporates the RIAA curve. However it's my understanding the curve wasn't universally used in all LP recordings.

That's true, there are many recordings made in the early 1950s which did
not use the RIAA curve. It got adopted pretty universally quite quickly.

>So, if a recording uses some other eq curve, how will it negatively impact the resulting output?

The response will not be flat. You can look up the published curves for,
say, the early Decca FFRR discs and see how they vary from the RIAA curve
and work out a differential curve.

However, what you should know about the Rolls is that the time constants
used are very low precision, so it probably doesn't actually meet the RIAA
curve anyway. Welcome to the consumer electronics world.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[William Sommerwerck]

> I don't think I've ever heard of a phono preamp without RIAA.

Until the late '50s, preamps often came with adjustable turnover and rolloff,
to accommodate various recording curves.

[Arny Krueger]

<muzic...@yahoo.com> wrote in message
news:112fcef6-b74c-4836...@googlegroups.com...

>I have this Rolls VP29 Phono pre - per its housing it incorporates the RIAA
>curve.

That is the standard. However it is not always implemented precisely and
there are variations on it

http://en.wikipedia.org/wiki/RIAA_equalization

> However it's my understanding the curve wasn't universally used in all LP
> recordings.

LP recordings are not all that precise.

> So, if a recording uses some other eq curve, how will it negatively impact
> the resulting output?

There will be an undesired timbre change.

[William Sommerwerck]

>> So, if a recording uses some other eq curve, how will it

>> negatively impact...

Affect! Alter! Modify! Change! Influence! Degrade!
Use simple, explicit words. Please. "Impact" (as verb or noun) is one of the
most-vapid English words. There are dozens of better words.

>> ...the resulting output?

> There will be an undesired timbre change.

Not quite. They'll be a change in tonal balance, though not much in timbre.

The roll-off frequency is generally higher than the fundamental notes of most
instruments, and the error appears as a shelving. There is thus little change
in the relative amplitudes of the harmonics, and thus not much of a change in
timbre.

[Arny Krueger]

"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:kmdl2o$995$1...@dont-email.me...

>>> So, if a recording uses some other eq curve, how will it
>>> negatively impact...
>
> Affect! Alter! Modify! Change! Influence! Degrade!
> Use simple, explicit words. Please. "Impact" (as verb or noun) is one of
> the most-vapid English words. There are dozens of better words.
>
>>> ...the resulting output?
>
>> There will be an undesired timbre change.

> Not quite. They'll be a change in tonal balance, though not much in
> timbre.

Willam, for a one-time professional writer, you surprizingly seem to need to
be schooled in the meaning of this word timbre today:

http://en.wikipedia.org/wiki/Timbre

"In simple terms, timbre is what makes a particular musical sound different
from another, even when they have the same pitch and loudness. For instance,
it is the difference between a guitar and a piano playing the same note at
the same loudness. Experienced musicians are able to distinguish between
different instruments based on their varied timbres, even if those
instruments are playing notes at the same pitch and loudness."

IOW, timbre and tonal balance are pretty much the same thing.

[Tom McCreadie]

>Willam, for a one-time professional writer, you surprizingly seem to need to
>be schooled in the meaning of this word timbre today:

And also of the words explicit and vapid :-)
--
Tom McCreadie

Live at The London Palindrome - ABBA

[William Sommerwerck]

>>> There will be an undesired timbre change.

>> Not quite. They'll be a change in tonal balance, though
>> not much in timbre.

> Willam, for a one-time professional writer, you surprizingly seem to need to
> be schooled in the meaning of this word timbre today:
> http://en.wikipedia.org/wiki/Timbre

"In simple terms, timbre is what makes a particular musical sound different
from another, even when they have the same pitch and loudness. For instance,
it is the difference between a guitar and a piano playing the same note at
the same loudness. Experienced musicians are able to distinguish between
different instruments based on their varied timbres, even if those
instruments are playing notes at the same pitch and loudness."

IOW, timbre and tonal balance are pretty much the same thing.

First, that's a lousy definition by any standard. In fact, it's downright
stupid. You can change the frequency response all over the place with an
equalizer, and still tell a Mauser rifle from a javelin.

Second, timbre and tonal balance aren't the same thing. Broadly speaking,
instrumental timbre is determined by which harmonics are present, and their
relative amplitudes. "Shelving" the harmonics of a musical instrument has
little effect on their relative levels and therefore little effect on timbre.

[Mark]

I thought I remembered someone published curves of the response error
you get when playing a 78 or other EQ record through an RIAA preamp,
i.e curves of the DIFFERENCE between RIAA and other EQs. You could
use a standard RIAA preamp and use the curves to EQ out these errors.

But I can't find them.

Would be interesting to generate these curves if not already done.

Mark

[Tom McCreadie]

>I thought I remembered someone published curves of the response error
>you get when playing a 78 or other EQ record through an RIAA preamp,
>i.e curves of the DIFFERENCE between RIAA and other EQs. You could
>use a standard RIAA preamp and use the curves to EQ out these errors.
>
>But I can't find them.

You could maybe check out the Diamond Cut software (e.g. DC7, DC8). This has a
Virtual Phono Preamp module that has equalization presets for "RIAA Vinyl
LP/45", "�arly Columbia LPs", "American 78s", "European 78s" and "Acoustical".

Perhaps use a suitable tone sweep to make a series of test recordings under
those equalization options, then compare the resultant frequency spectra?.

[Adrian Tuddenham]

Tom McCreadie <mccreadi...@xs4all.nl> wrote:

> >I thought I remembered someone published curves of the response error
> >you get when playing a 78 or other EQ record through an RIAA preamp,
> >i.e curves of the DIFFERENCE between RIAA and other EQs. You could
> >use a standard RIAA preamp and use the curves to EQ out these errors.
> >
> >But I can't find them.
>
> You could maybe check out the Diamond Cut software (e.g. DC7, DC8). This has a
> Virtual Phono Preamp module that has equalization presets for "RIAA Vinyl
> LP/45", "�arly Columbia LPs", "American 78s",
> "European 78s" and "Acoustical".

"Acoustical" as a single preset? Either that is a bad joke or marketing
bullshit. Every acoustic recording has to be equalised individually,
even those made on the same day at the same session.

[Tom McCreadie]

>"Acoustical" as a single preset? Either that is a bad joke or marketing
>bullshit. Every acoustic recording has to be equalised individually,
>even those made on the same day at the same session.

Adrian, firstly I know nothing about this specialized field, but was merely
relaying some possibly helpful stuff I'd encountered in the DC software (that I
actually use for other purposes).

I'd noted those Equalization Presets from a cursory glance at the radio buttons
in the Virtual Phono Preamp menu of the DC7 program. And yes, "acoustical" did
puzzle me too.

The DC7 Users Manual gives:: :
-----------------------------
Virtual Phono Preamp
1. Default
2. Flat Preamp Hardware playing Acoustical Records
3. Flat Preamp Hardware playing American 78s
4. Flat Preamp Hardware playing Columbia Vinyl LPs
5. Flat Preamp Hardware playing European 78s
6. Flat Preamp Hardware playing RIAA Vinyl LPs
7. Line Input � Phono Preamp Bypass
8. RIAA Preamp Hardware Playing Acoustical Records
9. RIAA Preamp Hardware Playing American 78s
10. RIAA Preamp Hardware Playing Columbia Vinyl LPs
11. RIAA Preamp Hardware Playing European 78s
12. RIAA Preamp Hardware Playing RIAA Vinyl LPs
---------------------------------------------
Might 'Acoustical' have been the name of a now defunct record company? :-)

On further perusal of that Users Manual, however, I now see a wealth of info
that possibly answers the OP's question. It's inappropriate to reproduce the
details here, but FWIW there were tables for:

1. Equalization Curves (phonographic).
This gave the Turnover Frequency in Hz and Roll-off dB at 10kHz for the
following Equalization Curves:
AES, Columbia LP, EMI LP, ffrr (1949), ffrr (1951), ffrr (1953), NAB,
NARTB, RCA Early Orthophonic, RCA New Orthophonic, RIAA

2. RIAA Curve. Table of Values

3. Equalization Chart for LP records (prior to RIAA Standard)
This gave the Turnover Frequency in Hz and Roll-off dB at 10kHz for the
following Manufacturers:
Angel, Audio Fidelity, Bach Guild, Bartok, Boston,
Caedmon, Capitol, Capitol-Cetra, Cetra-Soria, Colosseum,
Columbia, Concert Hall,
Decca, Decca FFRR (1951), Decca FFRR (1953), Ducretet-Thompson,
EMS, Epic, Esoteric, Folkways, Haydn Society, HMV,
London, London International, Lyrichord, Mercury, MGM,
Oceanic, Oiseau-Lyre, Overtone, Polymusic,
RCA Victor (until 1953), Remington, Urania, Vanguard

Finally, the Diamond Cut Users forum might be a useful resource..lots of people
there doing restoration and forensic work.

[Adrian Tuddenham]

Tom McCreadie <mccreadi...@xs4all.nl> wrote:

> >"Acoustical" as a single preset? Either that is a bad joke or marketing
> >bullshit. Every acoustic recording has to be equalised individually,
> >even those made on the same day at the same session.
>
> Adrian, firstly I know nothing about this specialized field, but was merely
> relaying some possibly helpful stuff I'd encountered in the DC software
> (that I actually use for other purposes).

Sorry, I didn't intend it to appear as though I was criticising you
personally.

> I'd noted those Equalization Presets from a cursory glance at the radio
> buttons in the Virtual Phono Preamp menu of the DC7 program. And yes,
> "acoustical" did puzzle me too.
>
> The DC7 Users Manual gives:: :
> -----------------------------
> Virtual Phono Preamp
> 1. Default
> 2. Flat Preamp Hardware playing Acoustical Records
> 3. Flat Preamp Hardware playing American 78s
> 4. Flat Preamp Hardware playing Columbia Vinyl LPs
> 5. Flat Preamp Hardware playing European 78s
> 6. Flat Preamp Hardware playing RIAA Vinyl LPs
> 7. Line Input � Phono Preamp Bypass
> 8. RIAA Preamp Hardware Playing Acoustical Records
> 9. RIAA Preamp Hardware Playing American 78s
> 10. RIAA Preamp Hardware Playing Columbia Vinyl LPs
> 11. RIAA Preamp Hardware Playing European 78s
> 12. RIAA Preamp Hardware Playing RIAA Vinyl LPs
> ---------------------------------------------

The de-RIAA function is useful for someone who is just beginning and has
to use a RIAA pre-amp on unsuitable records. I have recently made an
analogue version of that, so as to reverse engineer customers' mistakes.

To lump all "European" 78s together is a big can of worms. Although
most English recording companies used a 300c/s turnover, the German and
French branches of HMV sometimes used the American 500c/s standard.
Decca did something else again (even before FFRR) and Edison Bell went
right out on a limb at one time with a turnover above 1Kc/s.

Some early electrical English HMVs used an extra pole of bass roll-off
to give the record a longer life when played on an acoustic gramophone.
There aren't many equalisers that will offer correction for that.

A lot of English post-war direct-cut discs used the 500c/s bottom end of
the RIAA curve but without the top boost. The BBC used a 2dB per octave
slope for some of their internal recordings.

On top of all this, many of the microphones gave a response that was far
from flat, so the recording amplifier sometimes compensated for it and
sometime it was left uncorrected and just regarded as part of the
overall recording characteristic.

> Might 'Acoustical' have been the name of a now defunct record company? :-)

There was the Acoustical Manufacturing Company of Huntingdon (which was
better known as QUAD), but they didn't make records. I have never seen
an "Acoustical" label here in the UK and I wouldn't imagine the name
could enhance the image of a record company anywhere else either.

>
> On further perusal of that Users Manual, however, I now see a wealth of info
> that possibly answers the OP's question. It's inappropriate to reproduce the
> details here, but FWIW there were tables for:
>
> 1. Equalization Curves (phonographic).
> This gave the Turnover Frequency in Hz and Roll-off dB at 10kHz for the
> following Equalization Curves:
> AES, Columbia LP, EMI LP, ffrr (1949), ffrr (1951), ffrr (1953), NAB,
> NARTB, RCA Early Orthophonic, RCA New Orthophonic, RIAA
>
> 2. RIAA Curve. Table of Values
>
> 3. Equalization Chart for LP records (prior to RIAA Standard)
> This gave the Turnover Frequency in Hz and Roll-off dB at 10kHz for the
> following Manufacturers:
> Angel, Audio Fidelity, Bach Guild, Bartok, Boston,
> Caedmon, Capitol, Capitol-Cetra, Cetra-Soria, Colosseum,
> Columbia, Concert Hall,
> Decca, Decca FFRR (1951), Decca FFRR (1953), Ducretet-Thompson,
> EMS, Epic, Esoteric, Folkways, Haydn Society, HMV,
> London, London International, Lyrichord, Mercury, MGM,
> Oceanic, Oiseau-Lyre, Overtone, Polymusic,
> RCA Victor (until 1953), Remington, Urania, Vanguard

That sounds a lot better, although the subject is immensely complex when
you try to sort out pre-1955 L.P. curves. The other problem is to know
where the master was recorded - a British label does not always
guarantee a British recording, there was a lot of matrix swapping going