Prefix - mounting for non LP12 TTs

Posted by: John on 24 January 2002

I am looking for suggestions on how to mount or store my prefix. I have a P9 and plan to have an ARO connector fixed to the arm cables. The prefix comes with an ARO connection. This gives me the flexibility of changing the prefix if needed with a cartridge change. Some people have suggested using valcro and fixing it to the bottom of the TT base. Does anyone have any other suggestions? Does Naim make a box for the prefix or a bracket to hang it?

Any suggestions are appreciated. Can someone at Naim comment!

John

Posted on: 25 January 2002 by pm

John/Jason

I don't want to rain on the parade, but isn't the point of the prefix that it keeps the signal path and number of connectors from the cartridge to the first stage of amplification to a minimum???

Surely, if you can't achieve that then you might as well spend the money elsewhere as the prefix is the same circuit as that on the 5*** cards.(I'm led to believe..)so why bother?

I'm interested because perhaps I've got it wrong. I wanted to make a DIY prefix for my LP12 from a couple of Naim phono cards. I couldn't see the point because my dealer couldn't get me the Ekos arm connector on its own and wanted £80+ for another complete arm lead!! That wasn't within the DIY budget! I still used the cards to build a separate phono and psu stage which I'm very pleased with.

Question, is the Ekos arm connector a pattern part used on any other arms? Does anybody know of a source for the connector.

Best of luck with your plans.

Posted on: 25 January 2002 by John

PM:

Jason doesn't seem to understand me. I want to cut leads that connect to the leads that typically go out to the preamp. This is were I intend on fixing the ARO connector so the signal path is reduced significantly. I am using the ARO connector because the prefix is a used one that comes with the ARO connector. My other option would be to cut and soder the prefix leads to the arm leads. I don't like this option because it makes it more difficult to change the prefix in the future. It also voids the warranty on the prefix. I am looking for ideas on storage of the prefix with the P9.

You comment that the internal boards are similar. I have a ground loop problem with the internal boards that is only solved my disconnecting my CDS1 from my 52 and plugging my CDPS into another socket. The internal boards knock down the performance of the 52 when another source is used. I expect to resolve this with the prefix. Try running your TT without any other source, if you notice a performance jump (considerable in my case) you probably have the same problem. Is this a design flaw with the Naim preamps??? I also expect a jump in performance as I assume it is being powered more efficiently and the length of cable will be shortened significantly. If the ARO connector is good for the ARO arm then it should be good for the RB900.

John

[This message was edited by John on FRIDAY 25 January 2002 at 19:24.]

Posted on: 25 January 2002 by Bob Edwards

John--

I wouldn't worry about voiding a warranty on the Prefix, since it appears you purchased it used. Generally the warranty only applies to the original purchaser.

Cheers,

Bob

Posted on: 25 January 2002 by David Dever

Why not fit a female DIN connector to the tonearm leads?

Or, you could have the tonearm re-wired in a continuous run from cartridge tags to DIN, have Prefix modified to DIN-type or use a tonearm cable of your own choosing.

Sadly, the wiring is the weakest link in the Rega tonearm saga.

Posted on: 25 January 2002 by John

Dave:

I am planning on doing the OriginLive internal rewiring at the same time. I have ordered a wire run with bare ends that extends about 3cm from the base of the TT. The prefix comes with the ARO connector so I had the dealer get the corresponding ARO connector from NANA to attach to the leads. You suggested the DIN connector, would this be preferable? if so why? After examining the ARO connector that needs to go on the leads I am very confident the attachement to the ARO connectors will be simple.

What about storing the prefix? Can it just sit on the shelf or should I isolate it be suspending it from the TT base?

Any help is appreciated.

John

Posted on: 25 January 2002 by David Dever

quote:
You suggested the DIN connector, would this be preferable? if so why?

'Cos it's not an ARO (!)--use something more standard, leaves you room for trying different arm cables or jettisoning the arm entirely.

If you do this mod intelligently, you'll end up with quite a good arrangement--I've seen too few people who knew how to solder the wire to the ARO plug, with disasterous results. The principal difference between the two is the size (two-point "pincer" contact for both, assuming you've got a good-quality DIN), which is necessary for the ARO to move unimpeded in normal operation.

Dave Dever, NANA

Posted on: 26 January 2002 by pm

David,

Any chance you could make a sketch and scan it in for us please?
Any hints on the soldering operation also gratefully received......

Cheers,

[This message was edited by pm on SATURDAY 26 January 2002 at 11:56.]

Posted on: 26 January 2002 by David Dever

This is easy--don't solder the wire to the plug, solder it to the pins (removed), then insert the pins into the plug (or socket).

Posted on: 27 January 2002 by John

Thanks Dave, I have changed my order at OriginLive and asked them to terminate the wire cables with a DIN connector. This way I only have to change the ARO connector on the prefix. I haven't seen the internal wires for the arm but I imagine they are more delicate than the ones with the prefix which look like they will be easy to work with.

I am planning to use velcro to mount the prefix on the bottom of the TT. Do you have any other ideas for mounting? Would it be better to have just sit on the self?

Thanks again for your input.

John

Posted on: 28 January 2002 by Laurie Saunders

I have recently installed a Prefix. I am using it with a Michell Orbe/SMEV/52/SCAP/135. I bought the Pefix second hand. It was an S type and was fitted with an Aro armplug. I sent it to Naim and they converted it to K type(I had been using the K boards in my 52). They also replaced the armlead with one few inches longer, and fitted an SME armplug which I supplied (they were quite happy to obtain one for me) They returned the prefix to me within a week in a brand new box, fully tested for a very modest sum (less than £30 I seem to recall)To install the prefix I made a smal plinth fro 12mm MDF and fitted small sorbathane feet to stop it sliding about. It sits on my turntable shelf under my Orbe. The clearances are qite close but sufficient. I initially powered the Prefix from my 52 (AUX a) the improvement was immediate and dramatic, even cold. I have since obtained a Hi-Cap to power the prefix. This made another large improvement. I then replaced the K boards within the 52 with "straight through" boards (£20). The sound of all inputs on the 52 improved(I now use the "phono" input on the 52 as another line level input having replaced the BNC sockets with RCA ones. The whole execise of getting the prefix has lifted the performance of the whole system, and as I said in an earlier posting, for anyone with a reasonably good MC cartridge a Prefix is a fantastic sound per £ bargain upgrade. Hope my experience is of some value-best of luck.

Posted on: 28 January 2002 by John

L. Saunders:

Can you explain to me the different setup options for the prefix. I don't fully understand your message but it suggests I have more than one option. I assumed that I would just plug the DIN connector into socket 2 in my 52. You seem to imply a better option.

What about the ground connector. Where do I connect this?

Thanks
John

Posted on: 30 January 2002 by Laurie Saunders

John: yes... you have to plug the prefix into input 2 on your 52 until you can get a power supply (Hi-Cap, or SCap). I strongly recommend that you remove the phono cards from your 52(they are now redundant) and replace them with (£20) straight through boards. All inputs on your 52 will sound better as you are making life easier for your Scap. What type of prefix is yours? I believe that the K type is vastly superior to the S type; the latter include an extra capacitor and resistor to filter out RF, though its a case of babies and bathwater here. Naim will do the conversion for a very small cost. The options you have are with the flying earth lead. I started out with it disconnected from the 52, and had no noise, hum or RF whatsoever. However after some listening I felt that the sound was slightly "thin" and connected the earth lead to the 52. The sound quality improved but I was now plagued with RF interference. I then wrapped the earth lead several times through a ferrite choke (available from RS for a few pounds), and left the earth lead connected to the 52. RF has now gone completely, and the sound now is the best I`ve heard. I`ve tried ferrite chokes on signal and power cables but always felt that they "slugged" the sound giving a rolled off effect. In this case it is the earth cable that has the choke on it and (theoretically) should be carrying no signal-other than the RFI picked up by the "aerial" effect. You should simply try all these options yourself. They are quick, easy and cost almost nothing and don`t involve switching equipment off, so you should be able to to do the comparison within a short time.
Best of luck

Posted on: 31 January 2002 by John

Laurie Saunders:

I purchased an E prefix to go with my Benz M2 cartridge. I am trying to create a setup that I can easily remove the prefix to send it for modification to a different type when I change the cartridge. Thanks for the info regarding the ground lead. I will have to play around with it to get the best results.

You mention that I should use the straight through boards. My 52 came with boards that I replaced when I bought my E internal boards. Are these straight through boards??? Maybe Dave Dever can quickly comment?

Thanks
John