Ortofon MC Diamond and SPU Mono CG 25.

[Johan K]

Hello dear hifi friends,

I’m sitting here in my humbled hifi-bunker, listening to an old Glenn Miller album in mono trough my recent Ortofon MC Diamond investment, with a nice hot cup of morning coffee. Tough it is a stereo cartridge that goes in a mono groove, it performs amazingly well. It sounds like that beautiful old fashion sound I always heard when I came over to my grandparants as a young boy. Just love it??.
It is understandable that Ortofon has made cartridges for about a 100 years when I hear the performance of the MC Diamond. The sound is just exquisite.
Now… I know all about using a ”real” mono cartridge when playing a mono record, and have had the Miyajima Zero mono cartridge here before, which performed even better in this area than the MC Diamond ofcourse due to the fact that it is a ”real” mono cartridge. I love the sound from Miyajima and will go for the Infinity Mono cartridge later this year. But unfortunatly I don’t have a mono-cart here at the moment, so I use the MC Diamond for now, -which performs best on mono recordings when compared to my other stereo cartridges.
However… Ortofon has a certain type of sound that I favour too, when playing these old recordings. So I feel a strong craving for an Ortofon SPU mono CG 25 Di MKII and put that cartridge onto my Technics SL-1200G, as a compliment to my coming Miyajima Infinity.

Is there anyone out there who has any experience of the Ortofon SPU mono CG 25? I have been concider the SPU for years now, but never got my *** out of the wagon to actally buy one. Any info about it is very much appreciated.

All the best

/ Jk

 

[Shuggie]

The Ortofon SPU Mono CG 25 is a very old-fashioned thing, but still a very fine cartridge. When properly partnered in terms of a step-up it does approach the level of Miyajima's Zero. But, the caveat here is that the SPU is a MC design with a peculiar 1.5mV output that's far too high for most MC phono amps and far too low for MM; in either case it tends to sound very unspectacular indeed. The answer is to pair the Ortofon SPU mono CG with a suitable step-up transformer, and fortunately Ortofon's own ST-M25 mono SUT has the right amount of gain for running into MM phono preamps and it clearly loads the cartridge correctly too. Partnered with the ST-M25 SUT, the SPU's sound character is set free and it becomes much more dynamic, colourful and musically expressive - a very good standard of mono reproduction by any standard.

I hope that helps. For what it's worth, I sell both Ortofon SPUs and Miyajima, and I had written off these ancient SPU Mono CG cartridges until I tried them with the ST-M25; and the good news is that this combination is quite reasonably priced. Yes, a Miyajima Zero (or Infinity) is clearly better, but at considerably higher cost, and I very much doubt that you would feel dissatisfied with the SPU/ST-M25, until you hear that Infinity!

 

[bonzo75]

The Miyajima carts also work better with their SUT

 

[Johan K]

The Ortofon SPU Mono CG 25 is a very old-fashioned thing, but still a very fine cartridge. When properly partnered in terms of a step-up it does approach the level of Miyajima's Zero. But, the caveat here is that the SPU is a MC design with a peculiar 1.5mV output that's far too high for most MC phono amps and far too low for MM; in either case it tends to sound very unspectacular indeed. The answer is to pair the Ortofon SPU mono CG with a suitable step-up transformer, and fortunately Ortofon's own ST-M25 mono SUT has the right amount of gain for running into MM phono preamps and it clearly loads the cartridge correctly too. Partnered with the ST-M25 SUT, the SPU's sound character is set free and it becomes much more dynamic, colourful and musically expressive - a very good standard of mono reproduction by any standard.

I hope that helps. For what it's worth, I sell both Ortofon SPUs and Miyajima, and I had written off these ancient SPU Mono CG cartridges until I tried them with the ST-M25; and the good news is that this combination is quite reasonably priced. Yes, a Miyajima Zero (or Infinity) is clearly better, but at considerably higher cost, and I very much doubt that you would feel dissatisfied with the SPU/ST-M25, until you hear that Infinity!

Shuggie,

Thank you for that good explaination.
I have my SL-1200G connected to an AirTight ATH-2 Reference SUT, with a two step gain of 23 or 29dB, and I think it could bring the SPU CG 25 to come alive and sing, what do you think..?

/ Jk

 

[Johan K]

The Miyajima carts also work better with their SUT

Indeed they do?!

/ Jk

 

[Shuggie]

The Miyajima carts also work better with their SUT

Unlike the SPU Mono CG cartridges, Miyajima mono cartridges are quite conventional in electrical terms, and actually work well with other SUTs with optimum gain, but of course Miyajima's SUTs are always a good choice. I am presently running my Miyajima Zero Mono B through a Phasemation 1:20 SUT, employing RCA 'Y' adapters to keep things truly mono, and the listening experience is very good indeed.

 

[Shuggie]

Shuggie,

Thank you for that good explaination.
I have my SL-1200G connected to an AirTight ATH-2 Reference SUT, with a two step gain of 23 or 29dB, and I think it could bring the SPU CG 25 to come alive and sing, what do you think..?

/ Jk

You really need 12dB gain for the SPU Mono CG

 

[Johan K]

You really need 12dB gain for the SPU Mono CG

Okay..? Why just 12 dB… any reason for that particular number?

 

[shakti]

Shuggie,

Thank you for that good explaination.
I have my SL-1200G connected to an AirTight ATH-2 Reference SUT, with a two step gain of 23 or 29dB, and I think it could bring the SPU CG 25 to come alive and sing, what do you think..?

/ Jk

even 23db is still too much gain for the most MM phono stages. The ATH-2 is optimized on the 23db position for carts with 40ohm coils, but the MPU has a 6ohm coil. This can work, but will not be ideal. Some step ups do allow for parallel resistors, which can be the way to create or to buy a customized step up for the MPU.

Having had the MPU, the sound is not like the Ortofon Heritage DNA, so there is no family sound between MPU and ANNA.

The Ortofon MC-Quintet Mono or the 2M Mono are more close to Anna family sound.

 

[Shuggie]

Okay..? Why just 12 dB… any reason for that particular number?

Because 12dB gain equates to 4 x voltage gain, which brings the SPU's output of 1.5mV up to around 6mV, so good for any MM phono preamplifier, and the volume control range of the system remains normal.

 

[Johan K]

even 23db is still too much gain for the most MM phono stages. The ATH-2 is optimized on the 23db position for carts with 40ohm coils, but the MPU has a 6ohm coil. This can work, but will not be ideal. Some step ups do allow for parallel resistors, which can be the way to create or to buy a customized step up for the MPU.

Having had the MPU, the sound is not like the Ortofon Heritage DNA, so there is no family sound between MPU and ANNA.

The Ortofon MC-Quintet Mono or the 2M Mono are more close to Anna family sound.

Thank you for these inputs shakti… really appreciate it?.

/ Jk

 

[Johan K]

Because 12dB gain equates to 4 x voltage gain, which brings the SPU's output of 1.5mV up to around 6mV, so good for any MM phono preamplifier, and the volume control range of the system remains normal.

Thank you Shuggie. That sounds very reasonable. Great info…!!

 

[Johan K]

Thank you for these inputs shakti… really appreciate it?.

/ Jk

Dear shakti,

About the heritage DNA of Ortofon, regarding the SPU’s and the other Ortofon mono’s soundvice is something to concider… took me a while to think about it, haha.. Saturday morning and all… haha.
Thank you shakti??!

All the best

/ Jk

 

[Johan K]

Because 12dB gain equates to 4 x voltage gain, which brings the SPU's output of 1.5mV up to around 6mV, so good for any MM phono preamplifier, and the volume control range of the system remains normal.

Dear Shuggie,

Thank you so much again for enlight me on the SPU issue yesterday… I am sorry for having left my brain somewere we don’t talk about… okay… haha. You know, I’ve stared at the SPU for about 3-4 years now I think, and always seen the ”1,5mV” as 0,15mV… That is why I thought it would work find with my already existing SUT. Don’t ask me why, and don’t tell anyone - they might think I’m from Sweden or something, hahaha….

Joke’s aside… I’ve done my homework and read about the SPU CG mono, and the ST M25 step-up transformer. So logical about the 12dB gain. What about go with the SPU Mono MM cartridge directly, with it’s 3mV output? Then you can skip the SUT all along. Do you have any experience with that one too? And if you have had… have you find any differences soundvice between the SPU Mono and the SPU CG Mono?

I don’t know why I’m so crazy about the SPU’s, but I find them so retro, and I think they look beautiful… well.. that’s just me. If I get them to sound right in my system, it would be a nice bonus… so we’ll see what will happen.

If you have some more info on the issue, I would be delighted.

All the best

/ Jk

 

[Shuggie]

Dear Shuggie,

Thank you so much again for enlight me on the SPU issue yesterday… I am sorry for having left my brain somewere we don’t talk about… okay… haha. You know, I’ve stared at the SPU for about 3-4 years now I think, and always seen the ”1,5mV” as 0,15mV… That is why I thought it would work find with my already existing SUT. Don’t ask me why, and don’t tell anyone - they might think I’m from Sweden or something, hahaha….

Joke’s aside… I’ve done my homework and read about the SPU CG mono, and the ST M25 step-up transformer. So logical about the 12dB gain. What about go with the SPU Mono MM cartridge directly, with it’s 3mV output? Then you can skip the SUT all along. Do you have any experience with that one too? And if you have had… have you find any differences soundvice between the SPU Mono and the SPU CG Mono?

I don’t know why I’m so crazy about the SPU’s, but I find them so retro, and I think they look beautiful… well.. that’s just me. If I get them to sound right in my system, it would be a nice bonus… so we’ll see what will happen.

If you have some more info on the issue, I would be delighted.

All the best

/ Jk

The 'regular' SPU Mono G MkII is a decent thing, at a reasonable price, with some vertical compliance so it won't damage stereo records, but in comparison to the SPU Mono CG with a suitable 12dB SUT, it sounds (to me) rather 'ordinary'. I do feel that, when it comes to playing mono records very well, there really is no substitute for a really old-fashioned mono cartridge like Miyajima or the SPU CG mono. That said, my friend Tom played me some mono LPs recently with a My Sonic Lab mono cartridge, and that was lovely, as it should be for over €3k!

 

[Johan K]

Thank you Shuggie,

Great info again. Very much appreciated. I will definitely take everything you’ve told me under concideration, thanx.

/ Jk

 

[Fonofilm]

Hello, happened to pass by this forum, new to me. I notice some delicious subjects to investigate later on.

Now, I sense a minor but important misunderstanding in this thread. Important, because it may damage your records. Perhaps hurting your wallet a little too, in case your record collection doesn’t match your new mono cartridge.

The Glenn Miller RCA album above really isn’t old. The recordings are old but the record is a modern one probably cut with a stereo lathe. Mono sound still, yes, but the groove (only one groove on each side, right? ;-) has same dimensions as a stereo cut groove.

Ortofon SPU Mono CG 25 Di MkII cartridge is intended for vintage monaural records, i.e. genuine old 33 or 45rpm mono records cut laterally with a wider groove: groove corresponding to a 25 micrometer radius or thereabout, may vary from label to label. Its stylus tip may damage a modern stereo sized groove of about 17 micrometer. A mono cartridge, not for use with all mono records.

Much can be said about playing mono. May I rest for now, it’s beyond midnight after all in these quarters.

 

[Johan K]

Hello, happened to pass by this forum, new to me. I notice some delicious subjects to investigate later on.

Now, I sense a minor but important misunderstanding in this thread. Important, because it may damage your records. Perhaps hurting your wallet a little too, in case your record collection doesn’t match your new mono cartridge.

The Glenn Miller RCA album above really isn’t old. The recordings are old but the record is a modern one probably cut with a stereo lathe. Mono sound still, yes, but the groove (only one groove on each side, right? ;-) has same dimensions as a stereo cut groove.

Ortofon SPU Mono CG 25 Di MkII cartridge is intended for vintage monaural records, i.e. genuine old 33 or 45rpm mono records cut laterally with a wider groove: groove corresponding to a 25 micrometer radius or thereabout, may vary from label to label. Its stylus tip may damage a modern stereo sized groove of about 17 micrometer. A mono cartridge, not for use with all mono records.

Much can be said about playing mono. May I rest for now, it’s beyond midnight after all in these quarters.

Hi Fonofilm, and welcome to WBF.
Thank you for your input, very much appreciated.

/ Jk

 

[rl1856]

Interesting thread, but I believe some clarification is needed.

Are you referring to the SPU MONO cartridge, or the CG25 DI MKII ? These are 2 separate cartridges.

The SPU Mono is the standard SPU stereo cartridge adapted for mono, and it does have vertical compliance. Stylus is 1mil.

CG 25 DI MKII is a single coil mono cartridge that is an update of their original MC design introduced in 1947. It has horizontal compliance only, with a 1mil conical stylus.

I own a CG25 DI MKII along with a single coil modified Denon 103. I regularly play mono LPs in my system (vintage jazz).

Listening through a true mono cartridge is a revelation and makes one wonder how an adapted cartridge can be tolerated.

 

[Johan K]

Interesting thread, but I believe some clarification is needed.

Are you referring to the SPU MONO cartridge, or the CG25 DI MKII ? These are 2 separate cartridges.

The SPU Mono is the standard SPU stereo cartridge adapted for mono, and it does have vertical compliance. Stylus is 1mil.

CG 25 DI MKII is a single coil mono cartridge that is an update of their original MC design introduced in 1947. It has horizontal compliance only, with a 1mil conical stylus.

I own a CG25 DI MKII along with a single coil modified Denon 103. I regularly play mono LPs in my system (vintage jazz).

Listening through a true mono cartridge is a revelation and makes one wonder how an adapted cartridge can be tolerated.

Hi lr1856,

Thank you for your input. Yes I know they are different, and they also have very different output voltage. I was at first very interesting in the true mc mono cartridge - the SPU CG25, but I had for some reason messed up the info regarding the carts output, and thought that I could use my AirTight SUT… But with an output of 1,5mV I would also need the ST M25 mc transformer.. so then I could better go with a true mono cartridge from Miyajima, like the Infinity or the Zero. Have not decide yet.

I like very much the clean big stage mono sound… and have some nice mono records. But not yet a mono cartridge… The Ortofon is still of interest - but so is the Miyajima’s. So we’ll see what will happen.

/ Jk