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Regulating NCC200 front end, and other tips

Jusy had to try bypassing the input coupling caps for the NCC200, so now I have no coupling caps in my dacs output or pre's input/output either:D
With everything rigged up DC offset is 22mV one channel and 25mV the other which isn't bad, with no input connected channels for my NCC200's are lower than 10mV's.
Obviously bypassing the coupling isn't something I would recommend and I just wanted to try it out.
Resulting sound is extremely clean and clear, very nice indeed!
 
I tried martin clarcs idea to repace the two diodes with a JFET in my NAP250 and 135.

naim_ccs.gif


As JFET I took a 2N4338. In a second step I followed Rons recommendation MilSpec Tantals (100µ Sprague M39003) instead of EvoxRifa MMK to use. As input coupling I use further SMR.

The result: The sound is completely different. Everyone, which used foils like I, will be surprised. I think, the mids are more accentuated. Swings. Makes fun. Very well, but differently. Guarantees a reconciliation for an NAC full of foils. It was worth a try.

Ronald
 
It was a certain risk, therefore it was somehow exciting. But you had many good ideas and I were curious.

The effect of the JFET alone is subtle. Probably, I inserted the MilSpec Tantal to fast.

Perhaps it tries still someone, which can describe the result better.

Ronald
 
Interesting to understand why in the preamplifier circuits Naim use two transistors to form a current source, while in the power amplifier they use two diodes and a transistor for the same purpose.

More interesting is that those who tried to use the two diodes circuit (or LED) in the preamplifier reported an improvement, while those who tried the two transistor circuit in the power amplifier reported an improvement too. :confused:

I have done some measurements on how these two current source circuits behave and they the same as far as I could measure, could it be that it doesn't really matter which circuit is used...
 
Teddy, I must laugh. Its correct, thats crazy. If you mean Jiiims Mod, I also make it.
Maybe ist an improvement too, if you change the transistor in the NAC against a JFET?
And, I described the change together with the MilSpecTant. Both together is the great change in the soundstage.
 
Thanks Martin, very interesting articles indeed. I'm tempted to try the last circuit in #9. Although most of us spend time improving the voltage regulators, I suspect that a lot can still be achieved by improving the current sources (or sinks).

These Naim amplifiers can be improved endlessly. It's true that not much is left from the original design, but after all the construction quality of the cases is very good... :)
 
Could some kind gent post a circuit diagram of the vbe (+ve and -ve rail) for this modification please??
I am reasonably sure of one rail but I am concerned that I might bodge a dodgy circuit to the detriment of my vbe, NCC200 and ego!
Cheers Andy.
 
Yes, thanks. Looking closely I can now see what I am after. I'm sorry to go on a bit about this seemingly simple circuit but I have had problems with reliabilty of vbe circuits in the past for reasons I cannot identify. Also negative rail circuits can be tricky for me to get my head round. I'll get it right yet. Cheers Andy.
 
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