Phono boards (again, but different!)

Posted by: Chris L on 02 November 2001

On my LP12, I've got a high output moving coil cartridge, intended to be used with standard moving magnet input stages. Now, the output may be high for a MC, but at 2.5mV it's pretty low for a MM, and the consequence is that I've got to wind up the volume on the 32.5 rather a lot.

I remember seeing someone on the forum mention that Naim had modified his Prefix to better match the volume on various inputs (couldn't find the thread in a quick search).

So, onto my question, anyone suggest who would be the best person to contact at Naim about the possiblity of ordering a set of boards matched to 2.5mV input for my 32.5?

Cheers,

Chris L

Posted on: 02 November 2001 by JosephR

Does your preamp have the same board as the NAC 72 i.e. upright ? In my NAC72, its "K" board was perfect for the Dynavector 10X4 mK2 at 2.5 mv. On my NAC 52, my standard Lyra Helikon at 0.5mv is too high for its "K" board. Looks like the specs now are meant for the newer preamps ...
Have ordered the Helikon SL as a result ... Try a "K" board if you can maybe borrow from your dealer (or probably bring your preamp and test in the showroom) ...

Posted on: 02 November 2001 by Phil Barry

I ran a Grado (4.5 mv) through the 5-series K boards, but the MM boards were better.

I suspect that the 2.5mv would overload a 323K.

What's the p[roblem with turning the volume pot up? As long as you still have the ability to adjust volume to your liking, why change from the boards which best match the cart to other boards which do not match the cart?

Phil

Posted on: 02 November 2001 by JosephR

quote:
Originally posted by Phil Barry:
I ran a Grado (4.5 mv) through the 5-series K boards, but the MM boards were better.
I suspect that the 2.5mv would overload a 323K.
What's the p[roblem with turning the volume pot up? As long as you still have the ability to adjust volume to your liking, why change from the boards which best match the cart to other boards which do not match the cart?
Phil

Phil,

4.5 mv would be overload for sure ... also, you're using the new 5 series ... I used the 0.4mv Transfiguration Spirit on the older NAC 72 using its "K" board and turning up the volume to 4 o'clock could not bring out the powerful bass (tried the "S" as well, same results).

But using the Spirit on the NAC 52 and its "K" board, the bass punches out delightfully at 2 o'clock ...

Unless my 72 was defective (the boards were all new), it seems the phono section design of the older preamps like the 72 (or 32.5) vis a vis the recent ones are different ... anybody can confirm this ?

Posted on: 02 November 2001 by Chris L

As far as overloading goes, I was once told by a dealer that the Naim boards are so "over-engineered" that putting a 75mV signal into the phono boards for a brief time wouldn't harm them - although it's obviously not recommended! But I wouldn't expect using 2.5mV into boards intended for (I'd guess) between 0.25 and 0.75mV, to do any harm.

In fact, I ran a MM cartridge with 322S boards for quite a while - by mistake, I might add, but the cartridge was so rubbish, it didn't degrade the sound much.

I'll try the K boards for a while, as it happens I have a spare set - but I'd really rather get the right boards, matched for the 2.5mV output.

Chris L

Posted on: 02 November 2001 by Martin Payne

quote:
Originally posted by Chris L:
On my LP12, I've got a high output moving coil cartridge, intended to be used with standard moving magnet input stages. Now, the output may be high for a MC, but at 2.5mV it's pretty low for a MM, and the consequence is that I've got to wind up the volume on the 32.5 rather a lot.
I remember seeing someone on the forum mention that Naim had modified his Prefix to better match the volume on various inputs

Naim cartridge boards are available in the following configurations:-

Cartridge and high level options
Moving Magnet type "N" 2mV, 47 KOhms
Moving Coil type "S" 100µV, 470 Ohms
Moving Coil type "K" 100µV, 560 Ohms
Moving Coil type "E" 400µV, 560 Ohms

(from the Naim site).

If the "N" boards are too insensitive, maybe try out the "E"s?

May be an impedance mis-match, though.

cheers, Martin

Posted on: 02 November 2001 by Justin

How did you run a Grado MM into a set of MC boards?!! I did this by mistake once and the top half of the musical spectrum dissappeared. Tonally, I was under the impress that you can run MC carts into MM boards and it will sound OK, but you'll have very little gain. On the other hand, an MM cart into an MC board sounds terrible, even though there is plenty of gain. No???

Judd

Posted on: 02 November 2001 by David Dever

quote:
Grado into MC??!!! How did you run a Grado MM into a set of MC boards?!! I did this by mistake once and the top half of the musical spectrum dissappeared. Tonally, I was under the impress that you can run MC carts into MM boards and it will sound OK, but you'll have very little gain. On the other hand, an MM cart into an MC board sounds terrible, even though there is plenty of gain. No???

The Grado Statement, for example, sounds quite good with a 323-"k"-type board in a NAC 72, even though it's (allegedly) rated at a couple of millivolts. Don't ask me why; it's not unusual considering the fact that low-output moving coil cartridges tend to sound better than their high-output bretheren on a regular basis...you ultimately have to try what works.

Dave Dever, NANA