[strhd07]

I have a Decware ZMC MC step-up transformer, which is passive but is adjustable by a knob on the front. If I'm going to use it with my Pro-ject phono pre (which also has continuously adjustable loading on it), what should I set the loading on the Project pre at if I'm going to hook it up to the Decware and fiddle with the Decware loading? Decware says to turn the knob up until you reach maximum volume and refine up or down from there to taste, but what setting should I have on the phono pre before I start adjusting the Decware SU?

Should I just flip the phono pre switch to "fixed" instead of "variable," which Pro-ject recommends for MM carts, but what setting should I use as the fixed setting if I'm going to hook the Decware up to it? Decware says the ZMC is meant for preamps with only an MM stage, but is there any advantage to using the ZMC with the MC stage on my phono pre and using the variable settings function on that?

Thanks for any help with this.

Mark

[woodsyi]

I think you would have too much gain if you use MC on your pre and SUT.  My guess is that your MC stage in your Project is a cheap transformer inside since active gain stage is much more expensive.  So you would be piggybacking two SUTs -- not a good thing.  Using the MM stage you are bypassing the cheap internal SUT and putting in a presumably better SUT to get the extra gain you need for the LOMC that you are using.  Additionally MC out on your Project would have resistive loading that would interact with loading from your SUT that you say has variable loading.  I am assuming the Decware folks would have configured their loading with 47K ohms standard MM load.  So that would be another reason to use MM on your Project with your SUT.

[strhd07]

Thanks. That's what I'll do then.

[andyr]

I have a Decware ZMC MC step-up transformer, which is passive but is adjustable by a knob on the front. If I'm going to use it with my Pro-ject phono pre (which also has continuously adjustable loading on it), what should I set the loading on the Project pre at if I'm going to hook it up to the Decware and fiddle with the Decware loading? Decware says to turn the knob up until you reach maximum volume and refine up or down from there to taste, but what setting should I have on the phono pre before I start adjusting the Decware SU?

Should I just flip the phono pre switch to "fixed" instead of "variable," which Pro-ject recommends for MM carts, but what setting should I use as the fixed setting if I'm going to hook the Decware up to it? Decware says the ZMC is meant for preamps with only an MM stage, but is there any advantage to using the ZMC with the MC stage on my phono pre and using the variable settings function on that?

Thanks for any help with this.

Mark

I agree with woodsyi - go MM in your ProJect phono stage; this will present a load of 47K to your Decware SUT.

I presume you have the ZMC1 - with the 1:20 ratio for LOMCs?  In which case your 1:20 transformer presents a load to the cart of 47000 / 400 (20 ^2)  =  118 ohms.

If this is the optimal loading for your cart - then that's perfect!     But if it's not ... you may have a problem.   

The Decware ZMC website didn't go into enough detail about what exactly the 'adjustable cartridge loading knob' does ... but I suspect it is an adjustable resistance.  In which case, it will act in parallel with the Project phono stage's 47K - and will lower this.  IOW you can achieve a load for the cart of anywhere from 118 ohms downwards.

But if your cart likes more than 118 ohms ... you can't get there!     The oft-repeated 'rule of thumb' is that you need to have a load which is 10x the resistance of the cart coils - so if your cart's coils are 12 ohms or less, the ZMC will theoretically be able to provide the 'right' value.  However, when I had a Benz LP, I and my keen-eared listening panel thought the optimal loading was 3K3 ... which is 100x the coil resistance!  So IMO, the 'rule of thumb' is incorrect.
Note: you can only try higher loadings if you use an (active) head amp in front of the MM phono stage, since with any SUT, the "square of the turns ratio" factor comes into play.   


Regards,
Andy

[strhd07]

Thanks to all for the help. Still a lot for me to digest, un-tech that I am. Yes, it's the ZMC1. The Zu Denon DL103 and Benz LO Glider that I have both spec >100 ohms for a load, so it sounds as if I should be OK. The Pro-Ject RS phono pre also has on/off settings of 10, 100, 100, and 220pf at a fixed load of 47k ohms, with examples of 220 pf for an Ortofon 2M Red MM cart and 420pf for an Ortofon X5-MC cart. Someone else told me that lower capacitance (which I don't understand but have found a couple discussion threads that talk about it) is the place to start.

I'm only doing this because Art Dudley of "Stereophile" banged the gong for years that MC carts sound better with a separate SUT, for reasons I don't remember or didn't understand at the time, but also because, as someone else told me, the Decware presumably has higher-quality SUTs than the Pro-Ject. Anyway, it's worth playing around with to see what I get by using the ZMC1 and the fixed 47k ohm setting on the phono pre.