<a name="planetz-file"></a><a href="http://www.worldless.com/sfp/hd.html"><img src="/forums/images/file_icon.gif" border="0" alt=" File"> File</a><BR> <a name="planetz-tag"></a>Price ($USD): 0<BR> <a name="planetz-tag"></a>Type: Utility<BR> _____________________________________<BR><BR> PhonoPreAmp
I didn' found my PreAmp, so I built this one to stick my turntable directly into scope.
The default setting is carefully measured to conform to the RIAA curve.
<img src="http://www.worldless.com/sfp/images/PhonoPreAmp.jpg" width="267" height="125">
Unfortunately the analog inputs of scope collect some unwanted frequencies (at least in my case), so you better connect the turntable via an external A/D-Converter.
A side product was an eight band eq, available in the devices forum as well and for free like this one.
have fun !
Wolfgang
PhonoPreAmp
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Shayne White
- Posts: 1454
- Joined: Tue Dec 11, 2001 4:00 pm
- Location: California
- Contact:
I don't know anything about turntables or phono preamps (I'm Gen Y). What's the "RIAA curve"?
Looks nice!
Looks nice!
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http://www.melodious-synth.com
Melodious synth music by Binary Sea
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http://www.melodious-synth.com
Melodious synth music by Binary Sea
http://www.binary-sea.com
Hi Shayne,
if vinyls were cut with the same level of lows and highs as the original, the grooves for lower frequencies would need too much space and the needle could jump out of the groove. In the highs the at playback evolving hiss would be more appearant.
So the lows are decreased and the highs are raised before cutting the vinyl (regarding the highs -> the dolby a/b/c system for tapes works the same). This leads to more recording time regarding the lows and a better signal to noise ratio in the highs.
Until the end of the 50ies every recording facility had their own equalisation curve to achieve this, so every record sounded a bit different. The RIAA (now known from this unbelievable hunting after "pirates") introduced a normed curve, which is generally known as the RIAA curve, and most facilities started to apply that curve.
Btw, I left the equalizer accessable, because one might have a vinyl, where the curve is a bit different, so you can adjust this a bit.
cheers
Wolfgang
if vinyls were cut with the same level of lows and highs as the original, the grooves for lower frequencies would need too much space and the needle could jump out of the groove. In the highs the at playback evolving hiss would be more appearant.
So the lows are decreased and the highs are raised before cutting the vinyl (regarding the highs -> the dolby a/b/c system for tapes works the same). This leads to more recording time regarding the lows and a better signal to noise ratio in the highs.
Until the end of the 50ies every recording facility had their own equalisation curve to achieve this, so every record sounded a bit different. The RIAA (now known from this unbelievable hunting after "pirates") introduced a normed curve, which is generally known as the RIAA curve, and most facilities started to apply that curve.
Btw, I left the equalizer accessable, because one might have a vinyl, where the curve is a bit different, so you can adjust this a bit.
cheers
Wolfgang
-
Shayne White
- Posts: 1454
- Joined: Tue Dec 11, 2001 4:00 pm
- Location: California
- Contact:
I downloaded it, but I don't even have a turntable right now so I can't test it. 
I can't open up the EQ panel. What's up with that? Nothing appears.
Thanks for the RIAA explanation!
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<font size=-1>[ This Message was edited by: Shayne White on 2005-01-15 13:22 ]</font>
I can't open up the EQ panel. What's up with that? Nothing appears.
Thanks for the RIAA explanation!
_________________
Melodious Synth Radio
http://www.melodious-synth.com
Indieanna: Integrated Solutions for the Independent Musician
http://www.indieanna.com
<font size=-1>[ This Message was edited by: Shayne White on 2005-01-15 13:22 ]</font>
much, much appreciated, thanks Wolf
in fact it's rather noisy on the Pulsar 1 IOs, didn't even knew you could 'drive' them that high.
My (old) A16 indeed adds less noise, but with a proper mic-pre this should be the device for vinyl input.
Now that it basically works I finally have something worth modding a channel of the A16 with different OP-amps. I wouldn't dare that on the Pulsar, where it makes few sense due to the environment inside the PC anyway.
cheers, Tom
in fact it's rather noisy on the Pulsar 1 IOs, didn't even knew you could 'drive' them that high.
My (old) A16 indeed adds less noise, but with a proper mic-pre this should be the device for vinyl input.
Now that it basically works I finally have something worth modding a channel of the A16 with different OP-amps. I wouldn't dare that on the Pulsar, where it makes few sense due to the environment inside the PC anyway.
cheers, Tom
@shayne:
the eq surface opens fine here, don't know what could be the problem at your system, sorry.
@tom:
the noise starts here around -60dB, which is quite good regarding it is analog domain (especially since my cable to the turntable is 5 meters long )
I think it depends as well on the qualitiy of the ad-converter (I have the adi-8 ds), but a good mic preamp will do it fine as well.
Finally you can easily take a noise print and remove the noise floor via a denoiser (with osiris I come down to around -75dB).
Then take a 2nd denoiser to remove the playback noise of the needle, etc.
@immanuel
yeah, mm would be better, but most systems are mc these days.
Now, anyone dares to check out LochNess ?
cheers
Wolfgang
the eq surface opens fine here, don't know what could be the problem at your system, sorry.
@tom:
the noise starts here around -60dB, which is quite good regarding it is analog domain (especially since my cable to the turntable is 5 meters long
)I think it depends as well on the qualitiy of the ad-converter (I have the adi-8 ds), but a good mic preamp will do it fine as well.
Finally you can easily take a noise print and remove the noise floor via a denoiser (with osiris I come down to around -75dB).
Then take a 2nd denoiser to remove the playback noise of the needle, etc.
@immanuel
yeah, mm would be better, but most systems are mc these days.
Now, anyone dares to check out LochNess ?
cheers
Wolfgang
Thank you Wolfgang,
This could be the 'killer app' as far as getting some people attracted to Scope.
I think, though, that there are a lot more moving magnet cartridges than moving coil. A moving coil usually likes to see a low-impedence load, so a microphone pre-amp providing a load of 2,000 ohms should work fine. But a typical moving magnet cartridge wants to see about 47,000 ohms.
Not to look a gift-horse in the mouth, but would you consider offering impedence-compensation in the next version of your pre-amp? Maybe you could offer that one for sale.
This could be the 'killer app' as far as getting some people attracted to Scope.
I think, though, that there are a lot more moving magnet cartridges than moving coil. A moving coil usually likes to see a low-impedence load, so a microphone pre-amp providing a load of 2,000 ohms should work fine. But a typical moving magnet cartridge wants to see about 47,000 ohms.
Not to look a gift-horse in the mouth, but would you consider offering impedence-compensation in the next version of your pre-amp? Maybe you could offer that one for sale.
Nice one, Wolf! Thanks
jabney, your post made me think... Impedance is the sum of resistance and reactance. Resistance is the same for all frequencies, reactance is frequency dependant. More on that: http://www.whirlwindusa.com/tech03.html
The RIAA curve compensates for the reverse EQ applied before, and/or as a result of, pressing. The low output voltage of phono out doesn't have an influence on Pulsar's reading of the spectrum, I think Pulsar's AD convertors have a (near) flat frequency response. So, according to the impedance 'formula', their reactance would be very low. Remains the question how their reactance, or that of the pre-amp, compares to the one of a phono input. But I think they won't be much different. Maybe that can be simply answered by the following question, which is all that finally matters.
how does it sound?
Don't have a phono player here for now, I'm most curious!
The difference in input voltage to the convertors, without a preamp, will make for 5-6bit loss :/ So a pre-amp is certainly needed to compensate for that, to add analog 15-18dB's.
Just some background idea's...
[edit]
Funny, phono's ground wire attached to the PC case
<font size=-1>[ This Message was edited by: at0m|c on 2005-01-16 16:28 ]</font>
jabney, your post made me think... Impedance is the sum of resistance and reactance. Resistance is the same for all frequencies, reactance is frequency dependant. More on that: http://www.whirlwindusa.com/tech03.html
The RIAA curve compensates for the reverse EQ applied before, and/or as a result of, pressing. The low output voltage of phono out doesn't have an influence on Pulsar's reading of the spectrum, I think Pulsar's AD convertors have a (near) flat frequency response. So, according to the impedance 'formula', their reactance would be very low. Remains the question how their reactance, or that of the pre-amp, compares to the one of a phono input. But I think they won't be much different. Maybe that can be simply answered by the following question, which is all that finally matters.
how does it sound?Don't have a phono player here for now, I'm most curious!
The difference in input voltage to the convertors, without a preamp, will make for 5-6bit loss :/ So a pre-amp is certainly needed to compensate for that, to add analog 15-18dB's.
Just some background idea's...
[edit]
Funny, phono's ground wire attached to the PC case
<font size=-1>[ This Message was edited by: at0m|c on 2005-01-16 16:28 ]</font>
Immanuel is right, the impedance of the input stage is a hardware property and out of software control.
Basically (since the pickups impedance is higher) it will not have a significant influence on the input stage.
But at a closer view the system is much more complex. The pickup/entry stage is a wiered mix of inductivity (the coils !), resistance, (unwanted) capacity due to the physical construction, and real capacity from the usual input coupling.
The true frequency response and behaviour is more or less unpredictable - and that's what this device can compensate, at least to a degree
I have a 100 Euro preamp which is considered 'usable' (and a good buy for the money), a preamp with a noticable improvement can easily be 5 to 10 times as expensive - big geek factor included
That stuff is kind of overpriced, to say at least...
Yet it would be great to have the best possible input stage and I assume mic-pres are just that. They have to deal with extremely low signals, just as a moving coil pickup would provide.
In combo with a mic-pre that device can indeed spare an enormous amount of cash
But all that refers to differences way lower than the 'usual' record player distortions due to improper mechanical setup.
You really have to tweak that thing and care for pickup and stylus.
The points above refer to audiophile dealing with analog recordings in mint condition.
Forget about it if all you need is a sample for further musical processing, it's just not necessary to bother with those details
But in any case Wolf's device will save you from those crappy 50 buck phono preamps - well done !
cheers, Tom
<font size=-1>[ This Message was edited by: astroman on 2005-01-16 17:50 ]</font>
Basically (since the pickups impedance is higher) it will not have a significant influence on the input stage.
But at a closer view the system is much more complex. The pickup/entry stage is a wiered mix of inductivity (the coils !), resistance, (unwanted) capacity due to the physical construction, and real capacity from the usual input coupling.
The true frequency response and behaviour is more or less unpredictable - and that's what this device can compensate, at least to a degree
I have a 100 Euro preamp which is considered 'usable' (and a good buy for the money), a preamp with a noticable improvement can easily be 5 to 10 times as expensive - big geek factor included
That stuff is kind of overpriced, to say at least...
Yet it would be great to have the best possible input stage and I assume mic-pres are just that. They have to deal with extremely low signals, just as a moving coil pickup would provide.
In combo with a mic-pre that device can indeed spare an enormous amount of cash
But all that refers to differences way lower than the 'usual' record player distortions due to improper mechanical setup.
You really have to tweak that thing and care for pickup and stylus.
The points above refer to audiophile dealing with analog recordings in mint condition.
Forget about it if all you need is a sample for further musical processing, it's just not necessary to bother with those details
But in any case Wolf's device will save you from those crappy 50 buck phono preamps - well done !
cheers, Tom
<font size=-1>[ This Message was edited by: astroman on 2005-01-16 17:50 ]</font>
Good discussion!
Tom, you said, "Immanuel is right, the impedance of the input stage is a hardware property and out of software control."
Yes that is true. But the result of the loading mismatch should only (audibly) impact the frequency response. Therefore it should be correctable at any point between the cartridge and the loudspeaker.
In an RIAA filter you are reducing the high frequencies coming from the phono cartridge by an arbitrary pre-defined amount.
But if you load a cartridge which wants to see 47,000 ohms with only 2,000 ohms, you will lose some top end.
Would not adjusting the RIAA curve so that the signal was reduced less (and perhaps at different - or even additional - points) compensate for the loading mismatch?
This is not the case for guitars. An electric guitar with a passive pickup likes to see a very high-impedence load (one reason tubes and guitars like each other). Try plugging a guitar into a 10k or 20k load and it will sound relatively dull (one reason for DIs). If you try to compensate with tone controls, you have to boost a signal which also boosts any unwanted 'stuff' in the signal chain. And you are likely to get complaints from players that they don't get the same 'feel' as from a real amp.
A phono cartridge doesn't really care about feel, and the tonal adjustment (which is being done anyway by the RIAA curve) should still be cuts not boost and still have noise-reduction qualities even if load-compensated in software.
Of course boosting the treble a fraction of a dB might work, but probably not as accurately as a properly designed compensation to the compensation.
I could be overlooking something, so I'll try experimenting with different loadings.
An enjoyable topic. Thanks!
(Edited Jan 17 to eliminate a singular-plural conflict )
<font size=-1>[ This Message was edited by: jabney on 2005-01-17 20:16 ]</font>
Tom, you said, "Immanuel is right, the impedance of the input stage is a hardware property and out of software control."
Yes that is true. But the result of the loading mismatch should only (audibly) impact the frequency response. Therefore it should be correctable at any point between the cartridge and the loudspeaker.
In an RIAA filter you are reducing the high frequencies coming from the phono cartridge by an arbitrary pre-defined amount.
But if you load a cartridge which wants to see 47,000 ohms with only 2,000 ohms, you will lose some top end.
Would not adjusting the RIAA curve so that the signal was reduced less (and perhaps at different - or even additional - points) compensate for the loading mismatch?
This is not the case for guitars. An electric guitar with a passive pickup likes to see a very high-impedence load (one reason tubes and guitars like each other). Try plugging a guitar into a 10k or 20k load and it will sound relatively dull (one reason for DIs). If you try to compensate with tone controls, you have to boost a signal which also boosts any unwanted 'stuff' in the signal chain. And you are likely to get complaints from players that they don't get the same 'feel' as from a real amp.
A phono cartridge doesn't really care about feel, and the tonal adjustment (which is being done anyway by the RIAA curve) should still be cuts not boost and still have noise-reduction qualities even if load-compensated in software.
Of course boosting the treble a fraction of a dB might work, but probably not as accurately as a properly designed compensation to the compensation.
I could be overlooking something, so I'll try experimenting with different loadings.
An enjoyable topic. Thanks!
(Edited Jan 17 to eliminate a singular-plural conflict
)<font size=-1>[ This Message was edited by: jabney on 2005-01-17 20:16 ]</font>
good points, Jabney - I have agree to the analogy with guitar pick-up impedance.
Hardcore vinyl geeks not only adjust impedance, but also capacitance of their pre-amps by hardware switches...
Whatever it may sound like, with DSP processing we have some nice (quality!) tools at hand that most people lack. On the other hand a DAW isn't exactly living room compatible
I wasn't able to immediately detect a drop in brilliance between the regular preamp and the direct connection to Pulsar or the (old) A16.
This might be due to the relative difference as guitar pickups usually have a 5-8 times higher impedance than a standard MM pickup.
Accordingly I'd modify my 'use a mic pre' suggestion to the more exclusive MC (moving coil) pickups, unless verified by measurement and proper A/B-ing that (even) MMs benefit despite a misadjustment.
Since most of my records are 2nd hand buys from 50s to 80s vinyls they usually suffer from mechanical problems in the first place.
If the 'tone' has been 'graved off' the track there's no restoration to bring it back
From the listening viewpoint it's pretty strange to publish an SACD master (of a classical recording) as an 'audiophile' vinyl.
It's good to keep the techique at live, though...
cheers, Tom (Shure V15-III on an ugly yet functional Dual 721)
Hardcore vinyl geeks not only adjust impedance, but also capacitance of their pre-amps by hardware switches...
Whatever it may sound like, with DSP processing we have some nice (quality!) tools at hand that most people lack. On the other hand a DAW isn't exactly living room compatible
I wasn't able to immediately detect a drop in brilliance between the regular preamp and the direct connection to Pulsar or the (old) A16.
This might be due to the relative difference as guitar pickups usually have a 5-8 times higher impedance than a standard MM pickup.
Accordingly I'd modify my 'use a mic pre' suggestion to the more exclusive MC (moving coil) pickups, unless verified by measurement and proper A/B-ing that (even) MMs benefit despite a misadjustment.
Since most of my records are 2nd hand buys from 50s to 80s vinyls they usually suffer from mechanical problems in the first place.
If the 'tone' has been 'graved off' the track there's no restoration to bring it back
From the listening viewpoint it's pretty strange to publish an SACD master (of a classical recording) as an 'audiophile' vinyl.
It's good to keep the techique at live, though...
cheers, Tom (Shure V15-III on an ugly yet functional Dual 721)