Question on ceramic cartridge output

[Wigwam Jones]

I resurrected an ancient Voice of Music Stere-o-matic four-speed changer today, and it seems to run pretty well now that I've gotten it going again. It has a Sonotone 8T cartridge and stylus in it.

It came in a V-M console from 1958 that I pulled the tube amp from, so it's been languishing for some time. But I decided to see what I could do to bring it back to life.

Now that it's spinning, I took the RCA outputs and put them into a vintage solid-state receiver but I noticed that I have a little issue with it.

The ceramic cartridge puts out a higher voltage that the typical magnetic cartridge, so it's 'too hot' to run into a phono input on the receiver. On the other hand, it's too low for the aux input.

Hmmm, what to do, what to do. I could put the original tube amp back into it, no problem there, but I was also wanting to record the output, and the original tube amp does not have a record-out capability.

Any thoughts on this? Is there perhaps an external phono pre-amp available for ceramic carts? I'm mostly wanting to play 78 RPM records with it. I have a more modern turntable that has 78 RPM speed on it and a Shure 91ED cartridge, which I believe I could get a 78 stylus for, but I'd like to see what I can do with this old V-M changer. Thanks for any ideas.

 

[gadget73]

I think the 8T should be about 1 volt output. They typically drop in output as they age though, so its very possible yours is on it's way out if it seems considerably weaker than a normal line-level device. Its possible the best option is replacing the cartridge with another of a similar type that has known good output.

 

[Wigwam Jones]

I think the 8T should be about 1 volt output. They typically drop in output as they age though, so its very possible yours is on it's way out if it seems considerably weaker than a normal line-level device. Its possible the best option is replacing the cartridge with another of a similar type that has known good output.

Thanks, that's good to know. So you're saying that a ceramic cartridge should have high-enough output to run straight into an aux input?

I did do a little poking around, because I know next to nothing about ceramic cartridges and their output voltage. What little I was able to find out was that apparently the 8T was one of the hotter cartridges in terms of voltage? And from searching eBay and other sources, it also appears that although the needles are available, the carts are rather expensive when they can be found. If I were going to spend that much, I'd probably go with a 78 RPM stylus for my more modern turntable. I do appreciate the information though.

 

[JBL GUY]

And in general this type of phono cartridge wanted to be connected to a device with a very high input impedance, up to 1 megohm.

At that impedance the output is relatively flat with little need for equalization, so an input with RIAA EQ would not be correct.

The typical line level input or aux input impedance of a solid state amplifier is usually less than 100K Ohms and this loads down the output voltage of the cartridge and also changes it frequency response from mostly flat the a response that will require some equalization. This account for reports of this type of cartridge lacking bass frequency response and sounding to bright.

Some have loaded down and attenuated the output of this type of cartridge to make it compatible with a standard phono input. When this type of cartridge is loaded down, the output changes to one that is similar to the RIAA EQ curve.

So while some do connect this type of phono cartridge to the aux input, it may not be the best option, even if the amplitude of the signal is enough to drive the amplifier.

 

[Wigwam Jones]

And in general this type of phono cartridge wanted to be connected to a device with a very high input impedance, up to 1 megohm.

At that impedance the output is relatively flat with little need for equalization, so an input with RIAA EQ would not be correct.

The typical line level input or aux input impedance of a solid state amplifier is usually less than 100K Ohms and this loads down the output voltage of the cartridge and also changes it frequency response from mostly flat the a response that will require some equalization. This account for reports of this type of cartridge lacking bass frequency response and sounding to bright.

Some have loaded down and attenuated the output of this type of cartridge to make it compatible with a standard phono input. When this type of cartridge is loaded down, the output changes to one that is similar to the RIAA EQ curve.

So while some do connect this type of phono cartridge to the aux input, it may not be the best option, even if the amplitude of the signal is enough to drive the amplifier.

So what would be your recommendation? Sorry, I didn't quite catch the 'loaded down' part; don't know how one would do that.

 

[JBL GUY]

So what would be your recommendation? Sorry, I didn't quite catch the 'loaded down' part; don't know how one would do that.

Sorry, by loading down, I mean placing a relatively low resistance in parallel with the output of the phono cartridge.

10 k Ohms has be recommend by some as a good starting point. This changes the output frequency response to somewhat match the input frequency response (RIAA) of a typical MM phono input and will attenuate the signal level to a level that may match a MM phone input.

Others have used a small value capacitor, around 250 pF in series with the output to lower the output level and provide a sort of RIAA eq output and then plug the cartridge into a MM phono input. This helps to restore the correct frequency response, but the RIAA curve has three knees to its EQ, and this only supplies one.

There are several circuits using FET transistors or OP amps that have been used to make ceramic cartridges compatible with the aux input of solid state amplifiers.

These typically have unity gain with a very high input impedance and a low output impedance to drive a solid state amplifier.

A quick internet search will turn up a number of these.

This is what is done when using a ceramic cartridge to play standard 33 1/3 rpm record with RIAA EQ.

Playing 78 rpm records is another can of worms. 78 rpm records may have one of several playback EQ curves depending on the manufacturer of the the record. Back in the day a number of the higher end pieces of audio gear had switch selectable phono playback EQ curves. Again a lot of info on the internet.

Here is a link with some information about 78 rpm playback EQ.

78 RPM EQ

You will receive information ranging from none of this makes any difference to it may be the most important thing.

Archivists become very OCD about this.

So it is up to you to decide how deep you want delve into the playback of 78 rpm records.

Any of these methods may provide adequate sound quality for the playback of 78 rpm records, it depends on the end listener and their perception of adequate sound quality.

 

[Wigwam Jones]

Thanks, that makes more sense to my somewhat nontechnical capabilities. I guess if I was really getting involved in 78 RPM playback in a big way, I'd go whole hog with EQ and so on; I was aware that pre-RIAA, there were a lot of different curves.

On a simpler and perhaps easier and more introductory idea, if I could simply pop up the gain and put it into an aux input, I can easily do the EQ in Audacity after it's recorded. I'm actually more interested in recording them at the moment, rather than simply listening.

 

[JBL GUY]

Then I would suggest one of the active circuits like the ones that I posted and run the output of them into the AUX input of your amplifier.

This will provide a mostly flat frequency response, electronically speaking because it will provide a very high impedance load to the ceramic cartridge and you should not have to DE-RIAA before applying the proper EQ for the particular record via Audacity or what every program that you use.

Of course you may experiment with the other methods that I have mentioned that use the MM phono input and see if they meet your sound quality needs. Adding a 250 pF capacitor in series with the output of the ceramic cartridge or placing a 10k Ohm resistor in parallel with the output of the cartridge and feeding this signal into your MM phono input would be simple things to try. You may experiment with different values of capacitance and resistance to find a value that works for you.

Here is a link to an Audacity page with information on recording 78 rpm records.

You may be aware of this information, but there may be others that find it interesting.

AUDACITY RECORDING 78 RPM RECORDS

You may still need to replace your ceramic phono cartridge. The do wear out as they age.

Please keep us informed as to how this works out for you.

 

[Wigwam Jones]

Thanks, I will do so!

 

[Wigwam Jones]

I have an idea!

I happen to have an old Realistic 32-1200C mixing console that I picked up a couple years ago, NOS, NIB for a couple bucks. I tested it, it works, and I didn't do anything with it.

However, the doco says:

http://support.radioshack.com/support_audio/doc8/8801.htm

* Two pairs of stereo phono inputs for your turntables (two magnetic
cartridges or two ceramic cartridges)

Since it has variable output, I should be able to 'pump up the output' before running it into my aux in!

This is not a photo of mine, but it's the same model as mine:

It's getting late here now, but I'll try this tomorrow, what do you think?

 

[gadget73]

That might do it. I had forgotten about the really high impedance bit. I don't spend much time with ceramics either, but if you do need a replacement, Gary at thevoiceofmusic can probably hook you up with one for small money. I had to replace one in a V-M changer recently and I think the replacement was under $20.

 

[JBL GUY]

Looks like it may work OK.

The specifications list the ceramic phono input impedance 1 meg Ohm and that is what you are looking for.

This should provide you with a signal that you can use for recording and applying the correct EQ via Audacity or whatever program you choose to use.

 

[Wigwam Jones]

Hey thanks a lot! I will try it out and let everyone know. Can't wait to give it a shot!

 

[Wigwam Jones]

Well, I hooked it up and it is working great! I sincerely appreciate everyone's advice and information. I would never have even thought about my old Realistic mixer had you not given me this valuable information! Thanks!

I have the mixer in the circuit now; from the changer to the Phono 1 on the 'ceramic cartridge' input. My workflow looks like this:

Input using Behringer UCA-202 to USB input on my laptop (Linux)
Record using 'arecord' from the command line to CD-quality WAV format
Denoise
Declick
Audacity to apply EQ, trim start and stop, apply metadata, export as FLAC/WAV/MP3 as desired.

My only question at the moment is whether to denoise or declick first. I'm experimenting with both.

 

[JBL GUY]

That is great.

I am glad it all worked out for you.

And we learned something about your mixer that may prove useful to others.

 

[oldvinyldude]

And in general this type of phono cartridge wanted to be connected to a device with a very high input impedance, up to 1 megohm.

At that impedance the output is relatively flat with little need for equalization, so an input with RIAA EQ would not be correct.

The typical line level input or aux input impedance of a solid state amplifier is usually less than 100K Ohms and this loads down the output voltage of the cartridge and also changes it frequency response from mostly flat the a response that will require some equalization. This account for reports of this type of cartridge lacking bass frequency response and sounding to bright.

Some have loaded down and attenuated the output of this type of cartridge to make it compatible with a standard phono input. When this type of cartridge is loaded down, the output changes to one that is similar to the RIAA EQ curve.

So while some do connect this type of phono cartridge to the aux input, it may not be the best option, even if the amplitude of the signal is enough to drive the amplifier.

Maybe I am missing something here-but you suggest placing a small value resistance (10k) in parallel to the line input-I thought this would make the effective resistance somewhat less than 10k ohm, as it is now in parallel with the 100k load, and current will seek the path of least resistance.

My limited understanding suggests placing a 900k resistance in series with the 100k of the line in connection, to arrive at 1meg.

I saw that the OP has found his solution, but I hope to gain some understanding here. I am interpeting "loading down" to mean adding resistance.

Thanks JBL Guy

 

[cdk99]

In my early-yet vinyl ripping experience, it is worthwhile to rip to 24/96 unless you are burning to CD, then 24/88. It's kind of like saving a RAW photo file, if you learn a new technique later you can go back and do better. My own listening has me doing everything in FLAC, I use a Sandisk Zip Clip player running Rockbox to play back away from home, it'll play about anything I load, not quite VLC, but omnivorous enough for me.

I also have found that denoise/declick automatically burns up some SQ, particularly the air in the highs. Have learned to edit out clicks and pops between tracks and live and let live with ones within songs.

If your denoise/declick is doing better I'm very interested in learning. I have Linux on a VM so I could try your workflow. So far I'm getting my best results using Amadeus Pro on Mac OS.

On my 1959 Boulevard tube amp, there are 3 disc settings, Flat, RIAA, and Old LP. It has a ceramic input, no mention of a setting for 78 unless Old LP covers that.

 

[JBL GUY]

Quote:
Originally Posted by oldvinyldude View Post
Maybe I am missing something here-but you suggest placing a small value resistance (10k) in parallel to the line input-I thought this would make the effective resistance somewhat less than 10k ohm, as it is now in parallel with the 100k load, and current will seek the path of least resistance.
My limited understanding suggests placing a 900k resistance in series with the 100k of the line in connection, to arrive at 1meg.

I saw that the OP has found his solution, but I hope to gain some understanding here. I am interpreting "loading down" to mean adding resistance.

Thanks JBL Guy

In the context that I used the term loading down, it means to reduce the load impedance (resistance) as seen by the device supplying the signal, in this case the ceramic phono cartridge. This is done by placing the resistance in parallel with the output of the device supplying the signal.

The frequency response of a ceramic cartridge in terms of EQ is not the same as a MM phono cartridge. A MM phono cartridge must have an EQ curve called the RIAA EQ curve applied to it to compensate for the EQ that is applied to a record when it is made.

A ceramic phono cartridge due the the way that it works, applies the needed EQ curve by a mechanical means. It is the difference between a velocity sensitive device (the MM phono cartridge) and a position/pressure sensitive device (ceramic phono cartridge).

This is a somewhat of a simplification of the explanation of how these two types of phono cartridges work.

If a ceramic cartridge is operated into a load impedance of around 10k Ohms instead of 1 meg Ohm, two things happen.

This impedance is achieved by placing a resistor of about 10 k Ohms in parallel with the ceramic phono cartridge output. One for each channel if is a stereo cartridge. The 10k Ohm value was an arbitrary value that some have stated has worked OK for them.

One, the output level of the signal is reduced and may be able to be connected to a MM phono input.

The second thing that happens is the frequency response is altered to somewhat perform in the manner of a MM phono cartridge.

As such the output frequency response somewhat matches the RIAA EQ curve supplied by the MM phono input.

If one were to place a 900 meg Ohm resistor in series with the output of the ceramic phono cartridge, the cartridge might see close to a 1 meg Ohm load, but the voltage drop across the resistor is so great that the signal may not be large enough to plug into an AUX input and if one tries to use a MM phono input the EQ curve would not be correct, because of the mechanically applied EQ of the ceramic phono cartridge.

Hope this helps.

 

[catman]

G'day mate, right on! :thmbsp: Regards, Felix aka catman.

 

[Wigwam Jones]

I also have found that denoise/declick automatically burns up some SQ, particularly the air in the highs. Have learned to edit out clicks and pops between tracks and live and let live with ones within songs.

I'm still learning, hardly an expert. I generally do not use deNoise on vinyl; only deClick. I sometimes use the noise reduction inside Audacity on vinyl.

However, with 78's, I am learning that deNoise is absolutely required. However, automatic settings are terrible. I have been playing around with making manual changes and monitoring the output as I make them. I work to find the sweet spot where the most surface noise is lost and the least music is lost, then do an abort/restart with that setting, and Bob's your uncle.

Not perfect by a longshot, but I have already produced a couple rips that stand up to what I'm hearing on the 78RPM library on archive.org.

However, deClick and deNoise are not freeware. I'm on the evaluation period. They're looking good enough to me that I'm going to have to save some money up and buy them; they're worth it to me.

That puts them in the same class as something I use to scan film, called vuescan. Paid for it long ago, never regretted it; it's the best.

These are my results so far. I'm still playing, still learning.