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NAP-140 Clone Amp Kit on Ebay
NAP-140 Clone Amp Kit on Ebay
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Old 3rd January 2018, 06:23 PM   #2731
rensli is offline rensli  Estonia
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Join Date: Jul 2014
Quote:
The ZTX652 or 653 and ZTX752 or 753 VAS transistors certainly are essential for real Naim sound quality
ZTX753/653 paired with MJE25x series drivers gives very good drive on the output, balanced feeling.

I have tried everything in LTP positions, long and short listening... nothing beats BC239C transistors.

Second best is BC550B PH03, these are also vintage, never seen them anywhere....

Quote:
2N5089 is a similar low-noise component from On-Semi and is supplied in the Caowei NAP200 clones, which sound superb with a little tinkering
I have these, you suggest to try them on the input LTP ??? I use them in VBE positions.
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Old 3rd January 2018, 07:37 PM   #2732
Ian Finch is offline Ian Finch  Australia
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The essential features of BC239C is that it has high Hfe, >600 and a very low noise figure as well. That's hard to find in current products and is a fair test for genuine parts. Naim's would originally have come from Texas Instruments in the UK, like the BC384, 184, 214 used in preamps, I believe). Another consideration is the PCBs are made for the US style EBC pinout and Philips BC types were CBE pinout, so they could need reversing - this a trap for anyone who thinks all the Prolectron BC series are the same.

BC550C is good but gain has to be selected to match that. There are plenty of so-so audio transistor fakes/copies of these out there on Ebay. Typically they are all much the same part, with medium noise and gain performance - nothing outstanding, at best like a simple BC550. What would be nice to find among the trash, are the really good Hitachi 2SC2545,6,7E series transistors which are long obsolete but highly regarded since long ago and still fetch good prices. https://4donline.ihs.com/images/VipM...TJS12201-1.pdf

I don't know how 2N5089 would go in your build, other than I suggest you look for really high gain among the choices you have - anything available in low noise types. I have been looking at what is available in SMD types but the choices are nothing special for this purpose. Good luck and tell us what you find in through-hole types because I haven't been successful so far.
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Last edited by Ian Finch; 3rd January 2018 at 07:39 PM.
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Old 3rd January 2018, 08:17 PM   #2733
rensli is offline rensli  Estonia
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Quote:
I have been looking at what is available in SMD types
Me too , just now i have collected hundreds of them(small signal to medium).
FZT651 and FZT751 <--- will try them as VAS

BC847C NXP, BC846B NXP.

They'r HFE are perfectly on spot... ~490 for BC847 and ~240 for BC846B

Its impossible to find low or high gain among same type

They are hard to test in setup, ITS SMD ment for Machinary insertion ((...

I like 2N5089 in VBE on NAP140 circuit. Yes they are high HFE, highest of all i got in the collection

first NAP140 will have 4x25VAC 300VA transformer from toroidy.pl
The other one will get 4x34VAC 400VA regulated down to 4x30V DC from toroidy.pl.
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Old 3rd January 2018, 08:47 PM   #2734
Ian Finch is offline Ian Finch  Australia
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For the Vbe multiplier, any gain requirement is only for DC and very small so any NPN is fine and should not affect sound much at all. In VAS applications, A Vceo of only 60V is a problem. You would need the FZT653/753 at 100V for most of the NAP range because the voltage swing is close to the difference between the rail voltages. With regulated +/-30V rails, I guess you should be OK.
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Old 4th January 2018, 06:48 AM   #2735
rensli is offline rensli  Estonia
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Quote:
You would need the FZT653/753 at 100V for most of the NAP range
I get these FZT651/751 transistors as sample from different batches. Same goes for small signal types.

They should give the idea how FZT653/753 act's in VAS )
Will try SMD types in future on lower rails.
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Old 4th January 2018, 10:26 AM   #2736
AndrewT is offline AndrewT  Scotland
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CDIL make a clone of the BC239 in all three hFE grades
Reading Cdil's datasheet they seem VERY SIMILAR to BC549
The hFE of the C grade is from 380 to 800 and HF noise is stated as 4dB typical.
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Old 2nd February 2018, 10:24 PM   #2737
huggygood is offline huggygood  France
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Ian,Andrew,I admire you and above all, I admire your patience and your perseverance.
the virtual is good but I hope to have the chance to meet you real one day.
the same for Nigel
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Old 3rd February 2018, 06:59 AM   #2738
Ian Finch is offline Ian Finch  Australia
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'Nice to know there is more than one reader out there but it is rewarding for us too, if it only helps one person to be inspired to read, think and be motivated to share by building and adapting some of this amazing technology for themselves and doing it right by their own initiative.

I don't know that I will travel to Europe again but I hope you find continuing inspiration here and go on to surprise yourself with great sound and share the details with us - perhaps with some ideas and advice of your own
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Old 3rd February 2018, 08:23 AM   #2739
huggygood is offline huggygood  France
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Quote:
Originally Posted by Ian Finch View Post
'Nice to know there is more than one reader out there but it is rewarding for us too, if it only helps one person to be inspired to read, think and be motivated to share by building and adapting some of this amazing technology for themselves and doing it right by their own initiative.

I don't know that I will travel to Europe again but I hope you find continuing inspiration here and go on to surprise yourself with great sound and share the details with us - perhaps with some ideas and advice of your own
you know, it's been years that I am having fun with amps, many, many amps ... and I always come back to the same school (naim quad A / R crimson jlh, ariston, cyrrus, nytech, some Bryston, some C-audio, some H / H and lots of tube amps).
I had big equipment like plinius, levinson, golmund but I was never satisfied with it, that's what led me to build my own devices with schema that I had heard.
for example, at naim, the best result for me was obtained with modified cd drives based on tda 1521 under different forms (OS, NOS, tube output, direct dac output, BJT output, op) but still without preamp or just a buffer.

I learned a lot with you and you, but also from Hiraga, Plantefeve, jacovopoulos, kaneda,Hood, brian powell etc etc etc
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Old 3rd February 2018, 08:25 AM   #2740
Ian Finch is offline Ian Finch  Australia
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Quote:
Originally Posted by AndrewT View Post
Reading Cdil's datasheet they seem VERY SIMILAR to BC549
The hFE of the C grade is from 380 to 800 and HF noise is stated as 4dB typical.
Continental Device India Limited - datasheet pdf
Continental Device India Limited - datasheet pdf
Yes, I looked at their BC239C and thought that with a range so wide for a graded transistor, it has to be optimistic these days and the typical range is probably maintained at about 400-600. That could be OK if you bought enough and were lucky but it's been many years since I bought a 100+ of TO92 transistors that weren't all closely grouped in the middle to lower end of the range. I opt for cut tape packaging and certainly get close matching but not often where we would like it. BC549C seems to have the more credible range.

Anecdote warning: Ages ago, Graham Dicker (The designer of the ultra-simple Digi 125 amp that AKSA developed into the AKSA55) wrote a few articles for ETI magazine (yes, it originated here in Oz) and a couple were based on selecting high gain BC549C parts for use as very basic, low noise amplifiers and buffers with better performance than typical opamps. IIRC, the measured range of the Siemens parts was up to 1200 (1) and grouped around 500 which allowed a 600 min. spec to be met by about 15 parts from the hundred bought.

The labels may not have changed and the tolerances are tighter but I think the average performance of these and similar high gain transistors has gone backwards in the near 50 years they have been around .
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