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martinswimmer
25-12-2019, 22:01
Merry Christmas everyone!

While experimenting with a new step-up transformer - I tried running an Ortofon MC25 FL into the phono stage (Valab LCR) with gain set to 0db and impedence 47K.
This goes into a stepped ladder type attenuator (I don't use a pre-amp - just an attenuator) and then into a valve power amp. The sound is better than when I was using various step-up transformers and I've got plenty of gain.

My speakers are Horning Agathon Ultimate, so fairly sensitive and the amp is push-pull EL34.

The questions is - is it expected that a relatively low output MC cartridge wouldn't need any amplification prior to getting to a power amp?

Pharos
25-12-2019, 22:10
In my limited experience the design of pre stages for MC cartridges has in the past been problematic with regard to S/N ratio.
MCs generally need a lot of gain, and to achieve this the designs have to be very well done to avoid noise.

You may have a lucky combination, or the phono stage have an inherently high gain..

walpurgis
25-12-2019, 22:35
Well, if it works, it works. I've done the same occasionally, but don't need to as I have a fine SUT handy.

Just don't go switching to other sources while you have the volume up enough the listen to your MC or you could blow your speakers (or ears).

martinswimmer
25-12-2019, 22:48
Well, if it works, it works. I've done the same occasionally, but don't need to as I have a fine SUT handy.

Just don't go switching to other sources while you have the volume up enough the listen to your MC or you could blow your speakers (or ears).

I don't have any switching mechanism - it's simply MC into the phono stage into a bare stepped attenuator into the power amp. So, I'm attenuating the already miniscule? signal coming out of the phono stage with no gain applied.

walpurgis
25-12-2019, 22:54
Ah. Simple but effective.

martinswimmer
25-12-2019, 23:18
If I understand correctly, if you're using a passive amplifier and the signal coming out of the phono stage doesn't need amplifying for your phono stage/power amp/speaker combo - there is no good reason to increase the gain prior to the attenuator.

I suppose that there are many people running sensitive systems with low output MC who never tried NOT using a step up attenuator or leaving the gain setting as for the MM?

Also, why 47K sounds better (to my ears and in my system) than say 200Ohms (for this particular cartridge)? Internal impedence is 6 Ohms - so recommended is 60+ ?
Theoretically, I could be running this into a MM phono stage with fantastic results.

oceanobsession
26-12-2019, 23:13
Hi there , is this due to your sensitive speakers that you are getting away without an sut , im using a valab with cadenza bronze 62db and 200 ohms load , great phono
for the money , also using a tisbury and valve monos , phil.

martinswimmer
26-12-2019, 23:22
Hi there , is this due to your sensitive speakers that you are getting away without an sut , im using a valab with cadenza bronze 62db and 200 ohms load , great phono
for the money , also using a tisbury and valve monos , phil.

I suppose it is. Today I've tried 2 other phono stages and they all work with zero gain and output roughly similar levels. How sensitive are your speakers? Have you tried running with no gain? Is your version of Valab the one that goes from 200 ohms straight to 47k?

JohnG
27-12-2019, 11:14
I have three MM Phon's that I can try this with.
I can try it immediately with a 'rebuilt Ortofon Kb', I can also at a later time do a Ortofon Kb, and a Hana SL if I feel it is worthwhile.
I have a Slagle AVC Dual Mono Volume Control, as well as two built in Balance Control Pot's on the 845 Monoblocks, that can be used as Volume Controls. Either gives me options to regulate the Volume.

I like the idea of this method with the MM Input, If it results in my setting the Pot's wide open on the Monoblocks, this setting cancels out any effects of the Pot' on the SQ, and I can eliminate a additional device in the system, hence remove the Slagle AVC.
If I were to use the built in Pot's only for Volume Control, a quarter turn will offer more than enough volume level.
If the MM Input works, the possibility is that I then get the opportunity to have the built in Pot's wide open and maintain a acceptable sound level.
I can then evaluate the effects of both Volume Control methods on the SQ, as the Slagle AVC is usually used with the Monoblocks Pot's wide open, as well as evaluate a Phon's performance with a SUT removed from the set up.

martinswimmer
27-12-2019, 12:54
I have a Slagle AVC Dual Mono Volume Control, as well as two built in Balance Control Pot's on the 845 Monoblocks, that can be used as Volume Controls. Either gives me options to regulate the Volume.


I have never heard a TVC but wanted to go that route before scaling down on ambitions and getting a ladder type pot.
If you can defeat the pots on power amps - maybe it would be better to keep the Slagle as volume control? In my system, I'm roughly half way up the volume scale, so no compromise in terms of loudness range.
Anyway, please let us know what are your thoughts once you've tried the combo. I've been mercilessly reducing the signal path everywhere - cables from the attenuator to the phono stage (input) and power amp are soldered to the attenuator and only 10cm long.

oceanobsession
27-12-2019, 16:13
Hi again , my speakers are 90db ish and my ming da 805 monoblocks needs 3/4 volume on the tisbury for 70 db lisening level , the valab lcr is the
current one on ebay , oh sorry i meant cadenza blue . if you set up the valab the same as me dont it give you excesive volume , im also building a dave slagle avc
and my system seems to like the volume pot open for best sound , but it still depends what ohms your cartridge likes , and my cadenza blue likes 200 ohms , the bronze likes 50 ohms , so it could work with the bronze , phil.

Mike Reed
27-12-2019, 19:28
If I remember the MC25 (my friend had one), it had a very healthy output; for a l.o. m/coil, that is. Don't know your amplification ststem, so can't comment further.

martinswimmer
27-12-2019, 19:55
If I remember the MC25 (my friend had one), it had a very healthy output; for a l.o. m/coil, that is. Don't know your amplification ststem, so can't comment further.

I think it's not the lowest outputting MC @ 0.5Mv but I've got a VDH Mc One, Shelter 901, Supex 1000, Entre Mc-1 - so will try them all over the weekend and see what happens.
I have plenty of gain with this but when I run the input into my S-VHS Hifi machine that I use for recording - it doesn't register anything on VU Metres. So, this anomaly must be down to my very sensitive speakers and relatively powerful power amplifier. I bet that a single ended EL84 won't be able to pull it off.

JohnG
30-12-2019, 14:54
Last night I put The New All Valve MM Phonostage into the home system.

I played the Vienna Mimic, rebuilt Ortofon K'b straight into the New MM Phonostage, and with the inbuilt Pot's wide open on the 845 Mono's, I was getting acceptable night time sound levels, and definitely sound levels that will be suited to most individuals requirements .

I have as a preference a requirement for a little more volume for certain music and day time listening, so I introduced the Slagle AVC, the result was a slight improvement in sound level, as well as a reverting to the sonic signature of the effect of the Slagle that I prefer, the sound signature that has kept the Slagle in the system for some time now .

The Slagle was still a little shy of the Sound Levels I would like to achieve, but possibly now at a level many would refer to as too loud, so it looks like I will be introducing the SUT on occasions in the future, just to achieve the extra sound level.

At present I am in Awe of the New Phonostage, and keeping the signal path free from other devices, will I hope have added to my 'Jaw Hit the Floor' moment with the new experience.
I am pleased for the info that has prompted me to use this method, and also pleased I can confirm it is working in my system producing very audible sound levels.

martinswimmer
30-12-2019, 16:28
Glad to hear it worked for you. Can you hear improvement in the sound on account of one less component/set of cables in the path?
I've swapped cartridges and using the Supex 0.2mv. It's working great, but now 1/4 short of the full phono stage output. I've put the load to 200 Ohms again...

JohnG
30-12-2019, 17:27
I will update on this question you have asked at a later date.
The Phonostage is Brand New, with Boutique Components, some it is said requiring 500+ hours burn in.
I promise to give a update on both playbacks methods, Phono Direct into Amp, or AVC > Amp vs SUT > Phonostage.
It will be a while before I report, but I will update on the New Phonostage, covering the 18 months of Journey to its final fruition.