Thanks for all the suggestions and comments. I guess I will start with
the "linear" part - frequency or impulse response, then noise and
pops. For non-linearity, I might start with a threshold - above the
threshold, the output follows a polynomial curve. There is also a
partition issue for linear filtering. Some filtering (ie. band-
limiting) will be before the NL operation and some (ie. resonance),
after. The good thing is that the project does not require any special
DSP hardware. I can simply convert CD data to linear PCM wav files, do
whatever I need on a PC, then convert the processed samples to mp3 for
playing.

On 2007-08-28, Randy Yates <yates@ieee.org> wrote:
> Tim Wescott <tim@seemywebsite.com> writes:
>> [...]
>> And nonlinear effects, to, I would imagine.
>>
>> Altogether it would be an interesting challenge, particularly if you
>> wanted to mimic _different_ gramophones and recording equipment.
>
> By the way, here are a couple of recordings kindly made available
> by Serge Auckland.
>
>   http://audiopages.googlepages.com/otherstuff
>
> You'll have to scroll down a bit to get to two mp3 links of
> his gramophone recordings.

I have no great insight into solving your problem, but it's obvious that
all sorts of things are going on here which give the gramophne its 
characteristic sound.

1. It's certainly got weak response to low frequencies.
2. There is a fair amount of hiss, which you could probably characterize
   with a bit of work. 
3. There is a fair amount of popping.
4. I'm curious if the noise is correlated to the rotational speed of 
   the gramophone...
5. It's pretty clear that certain frequencies result in a resonant buzz.
   

Neat!

	Mark

In article <1188239338.408481.89130@50g2000hsm.googlegroups.com>, 
ghuang@comcast.net says...
>
>
>I wonder if there exist some spec or transfer function of a filter
>that would immitate the responce of an old gramophone or 78s. I am
>retrfitting an old gramophone with modern mp3 electronics but like it
>to sound more "authentic".
>

I would start here:

http://www.victor-victrola.com/Victrola%20Horns.htm

As other posters have noted, you may want to add noise, nonlinear 
distortion, and clicks if you really want the simulation to be 
believable.

Do not forget adding some scratches, the click(s) for each turn of the 
record.

And sometime you need to push the arm it you got stuck in same groove. 
(I know there is only one groove on each side ;-)

-- 
Christen Fihl
http://HSPascal.Fihl.net/

Tim Wescott <tim@seemywebsite.com> writes:
> [...]
> And nonlinear effects, to, I would imagine.
>
> Altogether it would be an interesting challenge, particularly if you
> wanted to mimic _different_ gramophones and recording equipment.

By the way, here are a couple of recordings kindly made available
by Serge Auckland.

  http://audiopages.googlepages.com/otherstuff

You'll have to scroll down a bit to get to two mp3 links of
his gramophone recordings.
-- 
%  Randy Yates                  % "Maybe one day I'll feel her cold embrace,
%% Fuquay-Varina, NC            %                    and kiss her interface, 
%%% 919-577-9882                %            til then, I'll leave her alone."
%%%% <yates@ieee.org>           %        'Yours Truly, 2095', *Time*, ELO   
http://home.earthlink.net/~yatescr

On Aug 28, 6:28 am, panabiker <ghu...@comcast.net> wrote:
> I wonder if there exist some spec or transfer function of a filter
> that would immitate the responce of an old gramophone or 78s. I am
> retrfitting an old gramophone with modern mp3 electronics but like it
> to sound more "authentic".

Well it's all been said but a good high pass filter makes music tinny.
Add some white noise as well and it's a start.
There is a distinct sound of a 78 though - the needle in the groove
sound and of course the sound at the end as it spins on the end of the
groove.

panabiker wrote:
> I wonder if there exist some spec or transfer function of a filter
> that would immitate the responce of an old gramophone or 78s. I am
> retrfitting an old gramophone with modern mp3 electronics but like it
> to sound more "authentic".

Cut the lows below about 150Hz and the highs above 2KHz. Iss a few 
notches and a few resonant peaks.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

Tim Wescott <tim@seemywebsite.com> writes:

> Randy Yates wrote:
>> R.Lyons@_BOGUS_ieee.org (Rick Lyons) writes:
>>
>>> On Mon, 27 Aug 2007 11:28:58 -0700, panabiker <ghuang@comcast.net>
>>> wrote:
>>>
>>>> I wonder if there exist some spec or transfer function of a filter
>>>> that would immitate the responce of an old gramophone or 78s. I am
>>>> retrfitting an old gramophone with modern mp3 electronics but like it
>>>> to sound more "authentic".
>>> Hi,
>>>    Ha.  That sounds like a neat project.
>>>
>>> I certainly don't know what is the correct answer, but I'll bet
>>> you'll have to pass the "high-fidelity" audio through some sort of
>>> bandpass filter that attenuates low frequencies as well as
>>> attenuating high frequencies.  Just what the filter's low- and
>>> high-frequency cutoff values should be is the question.
>>>
>>> Then again, because nothin' is ever as simple as it first seems,
>>> maybe this is complicated problem.  Perhaps you'll need to
>>> implement some truly oddball "equalizer."
>>>
>>> If you solve this problem, I hope you share your solution with us.
>> It's not just linear distortion that needs to be modeled,
>> but also noise. No?
>
> And nonlinear effects, to, I would imagine.
>
> Altogether it would be an interesting challenge, particularly if you
> wanted to mimic _different_ gramophones and recording equipment.

By the way, here are a couple of recordings kindly made available
by Serge Auckland.

  http://audiopages.googlepages.com/otherstuff

You'll have to scroll down a bit to get to two mp3 links of
his gramophone recordings.
-- 
%  Randy Yates                  % "...the answer lies within your soul
%% Fuquay-Varina, NC            %       'cause no one knows which side
%%% 919-577-9882                %                   the coin will fall."
%%%% <yates@ieee.org>           %  'Big Wheels', *Out of the Blue*, ELO
http://home.earthlink.net/~yatescr

Randy Yates wrote:
> R.Lyons@_BOGUS_ieee.org (Rick Lyons) writes:
> 
>> On Mon, 27 Aug 2007 11:28:58 -0700, panabiker <ghuang@comcast.net>
>> wrote:
>>
>>> I wonder if there exist some spec or transfer function of a filter
>>> that would immitate the responce of an old gramophone or 78s. I am
>>> retrfitting an old gramophone with modern mp3 electronics but like it
>>> to sound more "authentic".
>> Hi,
>>    Ha.  That sounds like a neat project.
>>
>> I certainly don't know what is the correct 
>> answer, but I'll bet you'll have to pass the 
>> "high-fidelity" audio through some sort of bandpass 
>> filter that attenuates low frequencies as well 
>> as attenuating high frequencies.  Just what 
>> the filter's low- and high-frequency cutoff 
>> values should be is the question.
>>
>> Then again, because nothin' is ever as simple as 
>> it first seems, maybe this is complicated problem.  
>> Perhaps you'll need to implement some truly 
>> oddball "equalizer."
>>
>> If you solve this problem, I hope you share your 
>> solution with us.
> 
> It's not just linear distortion that needs to be modeled,
> but also noise. No?

And nonlinear effects, to, I would imagine.

Altogether it would be an interesting challenge, particularly if you 
wanted to mimic _different_ gramophones and recording equipment.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

panabiker wrote:

> I wonder if there exist some spec or transfer function of a filter
> that would immitate the responce of an old gramophone or 78s. I am
> retrfitting an old gramophone with modern mp3 electronics but like it
> to sound more "authentic".
> 

I can't really remember how does the real gramophone sound like.
However several resonant peaks with Q ~ 10 at the frequency of ~500Hz 
and its harmonics will make a distinctive "metallic" sound. You can also 
add the low rumble, hiss and flicks to it.


Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com