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Get thee an elna silmic....

...Just tried the 3.3uF SMR PPS caps on the input of the phono boards - worthwhile.
Pain to fit though - I had to extend their legs, though it might be better to fit them underneath the boards instead.
 
Hi Mark,

Is this right?
shoebox.msnw
 
Hi fatmarley

:)

Sure is...Well done!. What's she sounding like? Any better?

I see that your front led will still work...must have been something Naim planned to do themselves :D

Hope it works for ya

Cheers

Mark
 
HI Mark,

I've had the whole system off for a couple of days so it's difficult to say how it sounds compared to before, but i'm convinced it sounds better than my previous un-modified 102/180 (now 62/140) even from cold, or it could be my mind playing tricks on me!

Have you got any ideas for what i should do next?

What about bypassing the (normal/mute/monitor) switch?

Andrew weekes super regs?

Does anyone know what value/type of resistor i should use in place of the links i put in the balance control?
 
go with some Sregs - either in your hicap or clone or else fitted inside the pre and feeding them with raw dc from the power supply (ie get rid of its reg circuits)

Might have to wait a bit though - but well worth it - don't know anyone who has a less than ecstatic word for them
 
I'd second Tim's recommendation for SRs. I couldn't even begin to detail the changes these little cct boards made to my pre-amp. Andy is a real star.

You may want to start splitting the power rails up too, feeding each with its own SR.

I can't remember whether you use a TT, but look to replacing those ZTX384 transistors (both on the phono boards and the line/final gain ccts) with something a little more 'modern'. I've just switched out the ones on the phono boards and the input tranny on the other boards with 2SD786s. The difference is quite extraordinary(??). Sound textures, pace and rythm, lots and lots!!! :)

Sadly I only had 20 2SD786s, but I have 50 2SC3329s. I could mail you over a few if you wanted to try them. Free, or just return 'em :D
 
Hi fatmarley

>>I've had the whole system off for a couple of days so it's difficult to say how it sounds compared to before

That's why the "carded" preamps are wonderful tools to learn tweaking on!

>> but i'm convinced it sounds better than my previous un-modified 102/180 (now 62/140) even from cold, or it could be my mind playing tricks on me!

As long as your minds trick playing ability seems to be repeatable....thats great :)

>>Have you got any ideas for what i should do next?

If you really REALLY want my advice...based on my similar experiences with modding my 42..I would say...WHHOOOOOAAAA. Stop! For now at least.

Forget all the mods you have done, all the joys had from tweaking. Start enjoying more music and seeking more music to play on the system. This modding thing can almost be a drug that can send you down the dark side at times. Enjoy what youve accomplished and get to know your system better. Thrill yourself with new music till the year end. Elsewise...you just get hooked into making changes and forget that they really are done to improve our enjoyment of music.

I followed your exact path fatmarley and ended up loosing my way.....Im back on track now. So stop the modding till next year at least. Enjoy thy efforts of labor n fumes my good mann.



>>What about bypassing the (normal/mute/monitor) switch?
I'd leave it alone for now. Youve done good so far. Real good.

>>Andrew weekes super regs?
The power supply should be your next stop, yes. Send me a private message when you can.


>>Does anyone know what value/type of resistor i should use in place of the links i put in the balance control?:)
Do a search on balance control removal...this was covered about 2 months ago here in PFM

Cheers

Mark
 
Hi Chilly,
out of interest where did you get your 2sc3329 s? Are they as good as the 2sd786 s?
would be interested to give these a try.
cheers
ced
 
Ced,

I purchased the 2sc3329s from Pacific Semiconductor. They got 225 still in stock. I cleaned them out of all the 2sd786's they had, 20 in total. For the 2sc3329s they are charging $0.20 each, but you have to place an order over $50 for overseas. Though I got away with around $25.

http://www.pacificsemi.com/index.php

Or you could try here, but the cost is huge: http://www.borbelyaudio.com/index21.htm

Both transistor types have a very low noise figure and a low Rbb.

I haven't had chance to compare the two transistor types. I had a devil's job of getting the 786s in the right way round, you have to twist the legs. Look here in RichardH's reply about leg twisting.

I've now replaced the MC transistor ladder, the transistor Q6 from Neil McBrides cct diagram (or here press the signal path button) and the ZTX384 input transistor on all the other boards.

I'm still hunting for some reasonably priced 2sb737s!
 
Andy

I've been looking at this mod with interest but I've been told it may not be an optimum implementation of the cascode principle - because to quote..."Cascoding is supposed to prevent voltage variations between base and collector of the cascoded transistor thereby reducing the variance of the base-collector capacitance which is voltage dependant. Hence for a cascode to work properly the reference connection of the Vref of the cascode transistor base should be taken from the base of the cascoded transistor". I've also been directeed to this website link .

I don't understand a word of this - I just plug bits in where I'm told - I had decided to just give it a try, which I will anyway unless you think there's a better way of doing it

Tim
 
Chiily,

I would be very interested in trying the transitors, i will pm you.(don't tell Mark!) ;)


Mark,

I think your right, it gets very addictive. My original plan was to listen to the system for at least a few weeks in standard form but i took the lid off straight after the postman handed it to me! :eek:

One thing that's been on my mind is where i bypassed the buffer stage, if you follow the track past the bypass cable i fitted it goes to a resistor and back into the buffer stage + to ground, Should i cut the resistor out? or at least bypass it to ground?
 
There's nothing fundamentally wrong with the Cascode as shown, it will effectively shield the input devices from the output signal, holding Vcb more constant.

This will greatly improve linearity, reduce input capacitance and give better bandwidth.

Whether it sounds any good is a different matter - please report back!

You may find these interesting, although there are topological differences with FET's: -

http://www.borbelyaudio.com/ae599bor.pdf

http://www.borbelyaudio.com/ae699bor.pdf

This one is good, but appears to be broken at present: -

http://www.passlabs.com/pdf/cascode.pdf

Meanwhile, this is useful, look at the 2nd schematic: -

http://www.passdiy.com/projects/pearlono2.htm
 
Having real trouble finding a source for these - are the 2SC1755 an alternative for this cascode input thingy
 
The 2SD786 is discontinued :( hence the reference to the 2SC3329 as an alternative. I'm game to get some of these in from the US, if anyone wants some when I've got 'em? I reckon you need 11 per phono card if that's what you're modding, plus as many as needed to do the other stages.
 
I'm up for about 30-40 of the 2SC3329 if they're sane prices.
cheers
Ced
 
Richard,

I'll take some more 2sc3329. I'm going to try and use PSpice to model the London HiFi MC stage, then try and lay it out...it may take a little time. So I would be up for another 20. Try Pacific Semiconductor, I think I placed the link earlier in this thread.
 
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