Equalisation

[WGCman]

This is my first posting to this forum - rather long, I'm afraid, but I'm hoping that someone with more experience than I will not only answer my specific query on equalisation, but maybe also pick up from my other comments things I could be doing more effectively. I bought DC MIlennium ("DCM") several years ago with the intention of transferring my collection of LPs and 78s to CD or (more probably) MP3. For various reasons I am only now about to start seriously, and will probably upgrade to DC7 within rhe next few weeks.

I am confused about the various filters for equalisation in DCM - (even more in DC7, having seen the demo). Some of these (DCM and DC7) are on the paragraphic equaliser (PE), some (DC7 only) on the virtual phono pre-amp (VPA). Presumably you can use either? As I understand it, when records were made, the high frequencies were boosted and the low cut. When playing back this has to be reversed. An international standard for this HF boost and its reversal was established c1955 by the RIAA. Before then, different companies used different curves, though all for the same reason so not all that different from the standard. Most LPs will therefore require the RIAA standard reversal and most 78s will require something slightly different.

I have an Arcam Delta 60 Integrated Stereo amplifier, designed, I believe in the 1980s. Though the brief specifcation provided when I bought it does not say so, I believe that the "disc" input (which has a switch for moving magnet or moving coil cartridges) has circuitry to reverse an RIAA recording curve. It would have been silly to produce an amplifier for the masses without and I assume the spec takes it "as read" so doesn't even mention it. I imagine that most people using DC will have similar equipment, so, when recording LPs to computer will be able to rely on this for equalisation and will need the DC PE or VPA only if they use a "flat" amplifier input?

I have started with my collection of 78s. Initially I connected the pickup arm to a tape input, and got a quiet (but loud enough) signal, clipped in parts (female vocal especially), possibly because the impedance of the ceramic cartridge was poorly matched to the amplifier. I then tried connecting to the disc input, which more or less cured the clipping but got unacceptable 50Hz hum (50 Hz being in UK). My turntable has not been used for years, and I was able to reduce the hum to an acceptable level by improving the earthing with a soldering iron. However, even when I applied the RIAA LF boost to my original "tape input" recording, there was less hum than on the new "disc input" recording. I believe this could mean that my original was losing LF material (including the hum) as well as being clipped.

So I have decided that I need to record through the "disc" input and convert the equalisation from "RIAA" to something more appropriate to the 78s I have. If you're still reading, this is where I am confused. In both DCM and DC7 is a filter called "RIAA phono equalisation curve" This has LF boost and HF cut, so presumably provides the REVERSAL of the LF cut made by an LP record manufacturer; it would therefore be needed by someone using a flat amplifier or USB turntable, but not by someone recording to computer, like me, through a conventional phono amplifier. Is this correct?

Both DCM and DC7 also have a filter called "Reverse RIAA w 200Hz 78 Turnover" This has HF boost and a lesser LF cut. Am I right in assuming that this reverses the reversal of the RIAA performed by the playback pre-amp and substitutes it with a reversal of the LF cut made by the recording engineer? If so - this is probably the chap I need.

If I haven't overstayed my welcome, I have a further query. One disc, recorded by Melodisc, probably over 60 years old now, is warped and I could only play it by increasing the tracking weight from 2.5 to 5gr and reducing the speed from 78 to 45. Should I use a different "reversal" equalisation, and should I do this before or after changing the pitch and speed?

[Doug]

I am confused about the various filters for equalisation in DCM - (even more in DC7, having seen the demo). Some of these (DCM and DC7) are on the paragraphic equaliser (PE), some (DC7 only) on the virtual phono pre-amp (VPA). Presumably you can use either? As I understand it, when records were made, the high frequencies were boosted and the low cut. When playing back this has to be reversed. An international standard for this HF boost and its reversal was established c1955 by the RIAA. Before then, different companies used different curves, though all for the same reason so not all that different from the standard. Most LPs will therefore require the RIAA standard reversal and most 78s will require something slightly different.

The Paragraphic equaliser is for those who are "hardcore" about using the correct equalisation curves where as the virtual phono preamp (VPA) provides a more simple user interface and selection of the most commonly used equalisation curves, you just have fewer choices. So to answer your question, Yes you can use either.

Most LPs will require the RIAA standard equalisation unless as outlined in the manual for different eras and companies (cant remember what page it was).

78's on the other hand only require bass boost type equalisation or no equalisation at all (acoustical). The most common frequency turnover/filter for 78's is given in the VPA, but there are many more available in the paragraphic equaliser should you wish to experiment with them.




I hope that helps?

[Doug]

I have an Arcam Delta 60 Integrated Stereo amplifier, designed, I believe in the 1980s. Though the brief specifcation provided when I bought it does not say so, I believe that the "disc" input (which has a switch for moving magnet or moving coil cartridges) has circuitry to reverse an RIAA recording curve. It would have been silly to produce an amplifier for the masses without and I assume the spec takes it "as read" so doesn't even mention it. I imagine that most people using DC will have similar equipment, so, when recording LPs to computer will be able to rely on this for equalisation and will need the DC PE or VPA only if they use a "flat" amplifier input?

Some of us still use standard phono preamp equipment - and why not when it was at it's pinnacle back in the 80s. It's pretty unlikely that any amp back then applies no RIAA (or a 78rpm equivalent) to the signal tho. In which case, you are correct in saying you dont need to use the VPA unless you wish to reverse the RIAA curve before running impulse noise filters etc. But that is up for your experimentation to draw conclusions on which is better for the records you have.

I have started with my collection of 78s. Initially I connected the pickup arm to a tape input, and got a quiet (but loud enough) signal, clipped in parts (female vocal especially), possibly because the impedance of the ceramic cartridge was poorly matched to the amplifier. I then tried connecting to the disc input, which more or less cured the clipping but got unacceptable 50Hz hum (50 Hz being in UK). My turntable has not been used for years, and I was able to reduce the hum to an acceptable level by improving the earthing with a soldering iron. However, even when I applied the RIAA LF boost to my original "tape input" recording, there was less hum than on the new "disc input" recording. I believe this could mean that my original was losing LF material (including the hum) as well as being clipped.

So I have decided that I need to record through the "disc" input and convert the equalisation from "RIAA" to something more appropriate to the 78s I have. If you're still reading, this is where I am confused. In both DCM and DC7 is a filter called "RIAA phono equalisation curve" This has LF boost and HF cut, so presumably provides the REVERSAL of the LF cut made by an LP record manufacturer; it would therefore be needed by someone using a flat amplifier or USB turntable, but not by someone recording to computer, like me, through a conventional phono amplifier. Is this correct?

I think you need to clarify this more carefully - Are you using a Ceramic cartridge and not a moving magnet cartridge?

If so, then the output of the cartridge is too great for a "tape input" (which applies an incorrect EQ anyway) or for a MC/MM "Phono input". Instead, a ceramic cartridge is generally connected directly to AUX inputs.

Both DCM and DC7 also have a filter called "Reverse RIAA w 200Hz 78 Turnover" This has HF boost and a lesser LF cut. Am I right in assuming that this reverses the reversal of the RIAA performed by the playback pre-amp and substitutes it with a reversal of the LF cut made by the recording engineer? If so - this is probably the chap I need.

If I haven't overstayed my welcome, I have a further query. One disc, recorded by Melodisc, probably over 60 years old now, is warped and I could only play it by increasing the tracking weight from 2.5 to 5gr and reducing the speed from 78 to 45. Should I use a different "reversal" equalisation, and should I do this before or after changing the pitch and speed?

I've used that technique before as well. First, you need to establish your cartridge type and if there is EQ being applied to the sound. Playing 78s at 45 works well, but gets tricky if an EQ is applied at that speed. If the RIAA is applied at 45rpm, then it must be removed from the file BEFORE you change the speed of the file. Once removed, you can speed the file up then introduce the correct EQ curve for that 78.

[Brian]

One disc, recorded by Melodisc, probably over 60 years old now, is warped and I could only play it by increasing the tracking weight from 2.5 to 5gr and reducing the speed from 78 to 45. Should I use a different "reversal" equalisation, and should I do this before or after changing the pitch and speed?

Another slightly more expensive but much simpler technique would be to purchase one of the record weights normally on eBay for $15-$35. They are basically a heavy metal disc about the size of a hockey puck that sits on the turntable spindle and holds the record down. Except in the most severe cases of record warping it will flatten the LP permitting playback with normal counterweight and speed settings.

[Craig Maier]

I noted that you mentioned the use of a ceramic phono cartridge. This is not compatible with audio restoration work. It will not work properly with an RIAA preamplifier nor will it work properly with the various curves in the Diamond Cut suite because ceramic cartridges are not intrinsically flat in their response. As a matter of fact, they have a resonance in the middle of the audio band.

So -

You need to obtain a decent magnetic phono cartridge.

[WGCman]

I think you need to clarify this more carefully - Are you using a Ceramic cartridge and not a moving magnet cartridge?

If so, then the output of the cartridge is too great for a "tape input" (which applies an incorrect EQ anyway) or for a MC/MM "Phono input". Instead, a ceramic cartridge is generally connected directly to AUX inputs...........


........I've used that technique before as well. First, you need to establish your cartridge type and if there is EQ being applied to the sound. Playing 78s at 45 works well, but gets tricky if an EQ is applied at that speed. If the RIAA is applied at 45rpm, then it must be removed from the file BEFORE you change the speed of the file. Once removed, you can speed the file up then introduce the correct EQ curve for that 78.

Thanks that's helpful - remove the RIAA before correcting the speed. Obvious, actually, but I hadn't thought of it!

In response to your earlier point, the ceramic cartridge has an output of 200mV @ 2 megohms recommended load, the amp's tape input a sensitivity of 220mV @ 10 kokms. I have to turn the amp volume control high to hear through headphones or the speakers, but the digital output is usable despite the occasional distortion I mentioned. But I have found that it works better put into the disc input which has a sensitivity of 1.9mV @ 47 ohms (for MM) .

[WGCman]

I noted that you mentioned the use of a ceramic phono cartridge. This is not compatible with audio restoration work. It will not work properly with an RIAA preamplifier nor will it work properly with the various curves in the Diamond Cut suite because ceramic cartridges are not intrinsically flat in their response. As a matter of fact, they have a resonance in the middle of the audio band.

So -

You need to obtain a decent magnetic phono cartridge.

I have one, but....

The ceramic is a Decca Deram with freq response 18Hz to 18kHz plus or minus 3dB, on a four speed Garrard turntable. I also have a Shure M75 type 2 on a Thorens TD160 33/45 only, which I used for my LPs.

The Deram cartridge was not "state of the art" even when I bought it, but far better than most at a time when magnetic cartridges were very expensive indeed. More to the point I was happy with the sound, though of course microgroove discs were still rare and CD quality not even dreamed of.

Since those long-off days I have retired, and my hearing has deteriorated to the extent that I have been prescribed hearing aids which I use for some purposes, though not for playing or listening to music. I can still hear perfectly the full range of my piano, and hear things at concerts which others miss (though voices can be a problem). But my audiogram starts to diminish above about 5kHz, and I hear very little above 10kHz. So if I applied to Diamond Cut for a job in Audio Restoration you would probably be right to turn me away.

But I want to restore records for my own use. Rather than put my restored music onto CD, I shall convert the .wav files at the final stage to .mp3, to listen whilst hiking (one of the few activities I can still indulge). If I find that my hearing disability stops me from restoring I shall not persist, but I am not ready to give up yet. I believe it might even be possible to compensate partly for hearing loss by introducing a treble lift before restoring, to be reversed later. If others want to listen to my work, that will be a bonus, but it's not essential.

If I were a professional restorer, I would not dream of using anything but the best, and I certainly appreciate your advice about ceramic, but I believe that the quality of the ear is at least as important as the quality of the cartridge. It might be possible to get a 78 stylus for the Shure and fit the head into the Garrard arm, and will investigate further. However, considering the limitations of what I want to achieve, and the limitations on what I am physically capable of achieving, would you still insist that I need to do so?

[Craig Maier]

I should have articulated my point more clearly about the magnetic cartridge.

1. A Ceramic Phono Cartridge has a very high output level compared to a magnetic one and is not compabible with normal phono inputs on stereo preamplifiers. It can only be used with a line level input if you want to assure that you do not encounter clipping distortion.

2. Aside from what you can hear, the software must be able to "listen" accurately to the incomming signal in order to properly discriminate between audio signals and impulsive noise. A ceramic phono cartridge, besides having a marginally flat frequency response, produces a lot of distortion which can interfere with the detection/discrimination process. So, even though you may not be able to hear the full range of the audio spectrum, the Diamond Cut software relies on all of the information contained therein to perform its function properly.

so -

I strongly recommend the use of a Magnetic Phono cartridge. One that performs reasonably well for a decent price is the Stanton 500. It can be purchased with an LP 0.7 mil stylus. You can also purchase an auxillary stylus for 78s which you can plug into the cartridge when needed.

[Dan McDonald]

I am very very happy with the Stanton 500. I have a range of stylus sizes and the frequency response is extraordinary.

Dan

[WGCman]

I should have articulated my point more clearly about the magnetic cartridge.

1. A Ceramic Phono Cartridge has a very high output level compared to a magnetic one and is not compabible with normal phono inputs on stereo preamplifiers. It can only be used with a line level input if you want to assure that you do not encounter clipping distortion.

2. Aside from what you can hear, the software must be able to "listen" accurately to the incomming signal in order to properly discriminate between audio signals and impulsive noise. A ceramic phono cartridge, besides having a marginally flat frequency response, produces a lot of distortion which can interfere with the detection/discrimination process. So, even though you may not be able to hear the full range of the audio spectrum, the Diamond Cut software relies on all of the information contained therein to perform its function properly.

so -

I strongly recommend the use of a Magnetic Phono cartridge. One that performs reasonably well for a decent price is the Stanton 500. It can be purchased with an LP 0.7 mil stylus. You can also purchase an auxillary stylus for 78s which you can plug into the cartridge when needed.

Thanks, Craig and Dan,
I now know what I need

[Geebster]

Correct me if I'm wrong, since I don't use Stanton products.... Didn't they discontinue the 500 AL and E phono carts? A few dealers still may have them in inventory, but weren't they replaced by the 500 V3? The V3 doesn't look like near the calibre of cart.

GB