Naim Stageline questions

Got a few questions about the Naim Stageline phono Stage. Any help would be much appreciated.

I wanted to change the loading on my Stageline K (560 ohms) I know the minimum loading for MC that Naim do is the S type at 470 ohms, but wondered if anyone has changed to a lower value such as 100 ohms? That would probably suit my Ortofon MC cartridges better. I also have a Linn Kandid that I think needs lower loading than that. The Urika setting for the Kandid is 42 ohms. The recommended range for the Kandid is 50-200 ohms. It does sound too bright at 560 ohms IMO.

I’ve looked inside the Stageline and located the loading resistors. What brand of metal film resistors do Naim use? I assume standard cheap metal films aren’t optimal?

I read that you can upgrade to Charecroft Z foil resistors but I want to try some different values in cheaper resistors first.

For the loading resistor positions, I might try to install some small screw wire connectors (or similar) so I can change the loading more easily without soldering (at least to test out the different values)

In this thread on the Naim forum, in post 5 a guy reckons that the differences between K and S aren’t just down to the loading resistors.
https://community.naimaudio.com/t/naim-stageline-k-help/985/5
He says the S rolls off after 22 KHz but the K doesn’t

Does any know if that is correct or not? Are there any other circuit differences between the K and S apart from the 2 loading resistors?

 

I expect it is the same or similar to the NAC32/72 card designs and yes it changes loading resistor and capacitor between S and K otherwise they are the same circuit. To be honest Stageline is not Naim's finest moment, if you are using it in the context of a Naim system, what preamp do you have? I looked at Prefix which is arguably the best implementation of the same old design, better than a Stageline, and came to the conclusion RSL MC cards in my 72 were better. They provide jumper link adjustment for more than just S and K comparability. Kit does cards for 32/42/62/72/52/82. Hope that helps.

 

Thanks for the info. Preamp is non Naim. SJS model 1 (tube) or a Stax hybrid headphone amp.
Appreciate the stageline isn’t the best but the prices of the Naim preamps have rocketed. My Dads old 32.5 sounded nice too and is similar to the 72 but they cost £500 secondhand now.

Has anyone any idea of the cap value difference between S and K?, and which caps are different?

 

See post #4 here...

 

Thanks for that info. Much appreciated. I’ll now need to identify which caps are the 1 nF input caps.

So if I want to venture as to 100 ohms loading or even lower I assume I should probably change the input cap to 6.8 nF rather than the 1 nF currently installed?

Any idea on the brand of resistors and caps I should use that would most closely match the originals? I can try tinkering with different brand or types later but I want a base to compare to when changing values so I can evaluate the sound difference of the value change first.

 

Apologies, I should have quoted rather than linked, from my link, as per Craig's link:

"The loading is done by R1 and C9. The one shown is the S type i.e. 470R, 6n8. The K type is 560R, 1n0."

The C will be right next to the R. I wouldn't worry too much about the C but yes 6n8 if you are lowering the R. I believe the 6n8 will be a blue plastic cased rectangular job while the 1n0 will be a transparent cylinder polystyrene. I did find a source for the latter after I touched one with a soldering iron and shorted it out. I'll try and find out.

From acoustica preamp mods bible "Naim use the BC componets SFR25 resistors everywhere".

As I'm sure you are aware, K was for Linn cartridges of the Asaka, Karma, Troika era. S was for other low output MC cartridges. There may he others that have tried optimisation for Ortofon.

 

I think something like these LCR for the 1nF are close to what Naim used.
Something like this for the 6n8.

 

Thanks a lot for the info. I think I’ve identified the caps, they are indeed cylindrical 1nF caps.

Thanks for the LCR link. I wonder what Naim originally used?

I read that the -3dB point in the treble will get higher when you lower the resistor value to 100 ohms, so maybe if I replace those 1nF caps with 6.8nF will be better. I was a bit worried at first as I saw many people say the S boards don’t sound as open and dynamic as the K boards and the K boards are far preferable. If I left the 1nF caps in place when putting in 100 ohm resistors would I get HF nasties? Would the roll off point be too high?

I wonder if others have tried a cap value in between 1-6.8 nF Say 2 or 3 nF etc?

I actually have got a Troika and Karma, so it’s a bit inconvenient not having easily changeable cap or resistor loading as I also have some Ortofons and the Kandid that need much lower loading than the older Linn Supex built carts. I did read somewhere about someone modding a stageline with some plugs or something so you could easily change resistors. Not totally sure how to go about that though.

 

I don’t seem to be able to find BC componets SFR25 resistors to buy.

To start off with, if I went to my local electronics shop, (Cricklewood Electronics, as Maplin have sadly disappeared) if I bought some basic 1/4 or 1/2 watt metal film resistors would they be ok to test out different values? Or would they not be not up to scratch in a Naim component?

When you buy online you usually need to buy in bulk. If the shop resistors are not good enough if someone possibly has some ok resistors that are suitable in some different values - say 47, 100, and 150, 220 ohms or similar they might sell, it would really appreciated if you could give me a shout.

 

Naim never went in for fancy components, just about anything other than carbon resistors would be fine. Check out the acoustica link I provided for pfm past wisdom on better resistors in Naim preamps. Apologies up to my eyeballs in work so ferreting out resistors is a bit beyond me right now unfortunately. I put up cpc links as they have a relatively low free post limit. They are the more limited stock more highstreet version of Farnell from the same group. If you have somewhere local to visit that sells resistors by the ones/twos go for it.

 

In answer to the original question , yes it's fine to change the loading resistor to 100 ohms or even less. I do exactly that for my Ortofon MC's and the difference isn't subtle.

The loading capacitance actually makes very little difference so I wouldn't be in any hurry to change it but you can go as low as 100pF.

I also wouldn't expect any sort of improvement by using any sort of "posh" resistor.

For the higher output Ortofons such as the more recent Kontrapunkts, Cadenzas, Quintets etc it's also worth dropping the gain by moving to somewhere between the K and E circuit.

 

And remember you can just solder a 120R across the 560 to get to 100R as near as dammit to test.

 

Thanks a lot for the info. I assume carbon films are too noisy!
I’ll try the local place for normal metal films then, and see how I get on. If I could install some kind of plug system to plug resistors I and out that would handy. Wonder if anyone did that with a Naim phono stage or preamp?

 

Thanks a lot for the info. I see. So maybe I’ll
just leave 1nF cap alone and only change the resistor value.
yiu mention possibly going as low as 100pF. I only considered going higher but but might there be any benefit in going lower? More open sound?

the Linn Kandid sound fine gain wise with the K and that’s about 0.38 mV.
I guess some of the Ortofons are higher though at around 0.5mV. What’s the problem if you use with a K or S? Is the phono stage overdriven?

I remember reading that one resistor changes the gain. Any ideas which one it is?

 

Thanks for the input. Didn’t think of that. You could do that on the top, so you don’t have to take it apart. Nice tip for testing

 

RSL cards are adjustable on jumper links for R and C.
Superline has it's plugs.
You could modify the Stageline to wire out the R to the back panel and fit an R in a plug if you really wanted to. Personally I would not go there, if you wanted to do some tests to find what R suits then you could put some SIL sockets in there and poke resistors in until you find the right value then solder it in.
I have a colleague that says all problems in electronics come down to software and connectors, he is, of course, exagerating, but a lot do. I would have as few connectors in a system as possible. Some are necessary, this one isn't. I would avoid it long term but can see the purpose for short term testing. Long term, low current connections in particular, deteriorate and increase resistance. Not what you want.

 

You can't really go lower than 100pF. It was the minimum value I needed to stop the boards "motorboating". The purpose of the cap is to effectively ground RF but not pass audio frequencies so its value isn't critical and shouldn't affect the sound at all in theory unless the value is way too big or insufficient. In practice it's the other properties of the cap, ie the ones which cause it to be imperfect, which matter so its important to use some sort of film type, be that polystyrene or polyester.

The resistor does make a lot of difference to the sound with some cartridges.

 

Sorry was busy the past few days. Thanks for the suggestions. The SIL socket idea sounds like a good one for quick changes to test different value resistors.

I bought some resistors and soldered a 120 ohms in parallel to the existing 560 to give 98. To be honest I didn’t quite like the result (with the Linn Kandid). Something sound unbalanced I couldn’t quite put my finger on, and lowering with resistor didn’t really do much to fill things out. Maybe I should increase the cap as well to 6800 pf? The top end still seemed a bit too bright,

I guess I could solder another cap in parallel to the existing 1000pf to add capacitance (so I don’t have to remove the existing 1nF cap).

 

There will be folks with Superline that will have tried every loading under the sun, if you can track down their fumblings on the green forum, or go ask them, it might give you a good starting point? Certainly when I moved to DV20X2L I found some advice from Peter Swain on Superline loading. Might be worth a look.

Yes a traditional S loading 6n8 in parallel with the 1nF would allow you to get a decent idea of whether that will do anything for you. Sure it will be 7n8 ish but that is close enough to test.

 

Yes, here we go, Peter Swain the master Superline whisperer on Kandid. Second hand admittedly. It is another vote for reducing the gain a bit?