Ceramic Cartridge Phono Pre-Amp

[timelog]

About hum measurement: To measure 50/60Hz hum you can use any PC/Laptop recording software ( like free audacity ). Hum source is often groudloop of equipments AC mains connection. With using recording sofwares simple level (db) meter you can test easily witch mains connection combinations give smallest hum levels.  The measured range hum can be -45db  to almost -70db depending how succesfully
connections control hum.
 

[williamsunique]

About hum measurement: To measure 50/60Hz hum you can use any PC/Laptop recording software ( like free audacity ). Hum source is often groudloop of equipments AC mains connection. With using recording sofwares simple level (db) meter you can test easily witch mains connection combinations give smallest hum levels.  The measured range hum can be -45db  to almost -70db depending how succesfully
connections control hum.
  

Thank you for sharing this.  I use Adobe Audition, but Audacity will do just as well.  In Audition, I record a 20 second sample, in this case the signal from the turntable, with nothing actually playing, so "silence".  I now have a sound sample, which I then convert using the built in frequency analysis part of Audition.  This gives you a graph, where you can see where any noise is.  There will always be a peak at mains frequency, but one's goal is to get this peak as low as possible.

Paul

[timelog]

Bit offtopic: Just measured todays hum values (MM pickup) for fun

PC audiocard input*                            -77/-77 db(L/R)
Preamp out (recordplayer off)              -72/-70 db(L/R)  
Phono out  (recordplayer power off)     -60/-61 db(L/R)
Phono out  (recordplayer running)       -70/-52 db(L/R) ..needle up/inner groove
Phono out  (recordplayer running)       -70/-52 db(L/R) ..needle up/midle groove
Phono out  (recordplayer running)       -70/-50 db(L/R) ..needle up/outer groove

Phono out  (recordplayer running)*      -48/-44 db(L/R) ..needle down playing record end groove 

There is intresting issue that recordplayer powering makes L channel hum down 10db and R channel hum up 9 db.
Maybe because player is designed to be grounded through it mains AC connector. In case PC mains is grounded, but recordplayer not trough mains. Zero level (0db) is defined for level where record played not clip.

* Later additions

[williamsunique]

Bit offtopic: Just measured todays hum values (MM pickup) for fun

Preamp out (recordplayer off)              72/70 db(L/R)  
Phono out  (recordplayer power off)     60/61 db(L/R)
Phono out  (recordplayer running)       70/52 db(L/R) ..needle up/inner groove
Phono out  (recordplayer running)       70/52 db(L/R) ..needle up/midle groove
Phono out  (recordplayer running)       70/50 db(L/R) ..needle up/outer groove
  
There is intresting issue that recordplayer powering makes L channel hum down 10db and R channel hum up 9 db.
Maybe because player is designed to be grounded through it mains AC connector. In case PC mains is grounded, but recordplayer not trough mains. Zero level (0db) is defined for level where record played not clip.

This is useful information.  All your figures here would of course be minus.  It is useful as a ballpark that others can compare their figures to.  The record player powering is indeed strange.

Paul

[needlestein]

My wife has an old Dell PC laptop that I may resurrect if current shareware software will still work on it, download Audacity and maybe some other stuff and see what I can do.  I've been getting requests for digital captures of my ceramic cartridge experiments, but right now I just can't do it. 

[timelog]

Bit offtopic 2: Here measured Lenco L75 hum values with battery powered phonoamp (MM Pickup)

Battery powered phonoamp has "floating ground" and Lenco has no AC mainsplug grounding, grounding was solved connecting
Lenco L75 ground wire to soundcards backplate (usually connected to amplifier)

PC audiocard input                            -77/-77 db(L/R)
Phono out  (just phonoamp on)           -68/-68 db(L/R) ..ground here from phonoamp because measurement    
Phono out  (recordplayer power off)     -63/-65 db(L/R)
Phono out  (recordplayer running)        -60/-60 db(L/R) ..needle up/inner groove
Phono out  (recordplayer running)        -60/-62 db(L/R) ..needle up/midle groove
Phono out  (recordplayer running)        -60/-62 db(L/R) ..needle up/outer groove

Phono out  (recordplayer running)        -48/-48 db(L/R) ..needle down playing record end groove

Lenco frame rumble test*                   -45/-45 db(L/R) ..motor running + needle on stacked coins on steelplate

Lenco vinyl on platter rumble test*      -53/-53 db(L/R) ..motor running, but platter not + needle on vinyl record                     

Lenco vinyl on platter (idler free)
rumble test*                                    -50/-50 db(L/R) ..motor running, platter in free move (no idler) with needle playing record

Lenco feedback recistance (peak)*      -53/-52 db(L/R) ..Loudspeakers running loud 0,5m + needle on stacked coins + motor off  

In this case end groove hum was used to set Zero level (0db) correction (compared first measurement).
(Error +-2db)

* Later additions

[williamsunique]

Philips GP390 ssshhhhh!  Let's not rave about them, at least until I have obtained one.

Oh yes and dam, Musonic had them, Musonic is 10 minutes away from here.

Welcome Sharif, thanks for your input.

Paul

I knew they rang a bell.  From an earlier topic highlighted in red below.  
I misunderstood then how the matching circuit, which is built into the GP390 worked.
  
When these GP390s were marketed, ceramics were not regarded as being anywhere as good as moving magnets, or moving coils.  A lot were heavy trackers.  In HiFi circles the lighter playing weight was deemed all important, with some cartridges tracking at under a gram.  Also valve / tube amplifiers had been replaced by solid state amplifiers.  Where as the valve amplifiers input impedance was an ideal match for a ceramic cartridge, a transistors input stage is of a lower impedance and not suitable.  Valve amplifiers had a dedicated ceramic input, this was not available in the solid state amplifier.
I presume for marketing purposes this ceramic cartridge with its built in network, so it could be connected straight into a RIAA moving magnet input was termed an electret cartridge.  Micro-Acoustics also marketed several models of electret cartridges.  I wonder how close to the design of the Sonotone 9TAHC these new electret cartridges were.  The electrical and mechanical design of the 9TAHC, but with a built in network.  Some of the Micro-Acoustics electrets suffered from poor channel balance. Anyway to be able to build in a suitable network into a GP390 cartridge body would have been quiet an achievement, surface mount did not come into wide use until a few years later.

http://www.lencoheaven.net/forum/index.php?topic=12524.0
  "Phillips invariably did things differently.  Here we have a cartridge that you can plug into your MM input.  The output presumably being attenuated internally from several hundred millivolts to that of a typical MM cartridge and again presumably some type of built in reverse RIAA circuit.

I see Musonic still have these GP390 cartridges in stock."

Paul

[needlestein]

Here are some photos of some MR cartridge innards.  You can see the surface mount capacitor at least.

[Chris65]

Might have been mentioned already, but here's a site with Sonotone & Micro Acoustics information:
http://www.roger-russell.com/sonopg/sonopc.htm
http://www.roger-russell.com/sonopg/micropg.htm#cartridges

[analogadikt]

Here are some ceramic carts that I have.
On the top is a NOS Philips GP215. This does not have a replicable stylus assembly. Bellow that an EEI cs2000 on the left and cs2040 on the right. The cs2040 is exactly identical to the Garrard KS40. I believe EEI supplied these carts to Garrard.
The two at the bottom have Made In Japan markings but no brand name.
I have heard these many years (30+) ago and yes, except the EEI cs2000 all others impressed.
I shall try to check them out and report here.

Regards,

[williamsunique]

Here are some ceramic carts that I have.
On the top is a NOS Philips GP215. This does not have a replicable stylus assembly. Bellow that an EEI cs2000 on the left and cs2040 on the right. The cs2040 is exactly identical to the Garrard KS40. I believe EEI supplied these carts to Garrard.
The two at the bottom have Made In Japan markings but no brand name.
I have heard these many years (30+) ago and yes, except the EEI cs2000 all others impressed.
I shall try to check them out and report here.

Regards,

Please let us know how they sound.  I am having the best results using a DCB1 with the input resistors changed to 5M ohm.  Out of the ceramic cartridges I have tried here the Sonotone 9TAHC comes out on top, followed by my Sony VX23P, then my Decca Deram and last, but by no means poor the Sonotone 9TA.

Paul

[audioflyer]

More Philips GP390 information

The GP390 has an output across the ceramic elements and the two resistors in parallel  68K & 15K totalling 83K ohms the output measured across this network on a valve voltmeter is 8 mV (RMS) at a velocity of 1cm/sec.

The resistors form a "Tee compensation network" with the output taken across the 15K ohm resistor again using a valve voltmeter the output is 1.05 mV (RMS) at a velocity of 1cm/sec.

The GP390 also has a low frequency roll-off and is down at 50Hz by -1.2db to -1.5db and about 5db at 20Hz.

I see that on some ceramic cartridges with the compensation network the output is still to high, using the Sonotone circuit you could try increasing the 68K in approximately 5K steps say up to a max of 100K to reduce the output.

Sharif.

[Wout]

Found this by accident from the Sinclair Project 60 manual.
Might be of use.

[williamsunique]

Wout, very useful information, thanks for posting.

Paul

[needlestein]

Yes!  Thank you!