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Avondale NCC300 amp project ..

I pull some pins out of an 8 pin dip socket and used them to swap out BC456's, got the offset on my Qudos to +4 and -6 before I got bored.
Not sure it makes an audible difference but heyho.
 
GWM said:
I pull some pins out of an 8 pin dip socket and used them to swap out BC456's, got the offset on my Qudos to +4 and -6 before I got bored.
Not sure it makes an audible difference but heyho.
Click to expand...

Been there done that on many occations but still spend time making sure TR1 has a higher HFE than TR2 :) (a good practice procedure) In the past I have just thrown any BC456s in without checking HFE's and bugger me makes not a lot of difference maybe 10mv either way. Which is nothing to be concerned about.

To boot, I can't hear any difference ...
 
RichardH said:
You need something like these
pin-terminals.jpg


I have tested inserting the legs of TO92s into them and they go in nice and firmly and can also be easily removed. You can break them off individually, so with a bit of fiddling you could fit them where a TO92 should go. I've just tested, and the spacing is such that two still joined will fit the diagonal two hole span of a standard TO92 PCB layout, so you can get away with a block of two plus a single one.

I don't know what they are called though. I have two strips of them as per the one pictured (enough for 13 TO92s), and you're welcome to them if you wish (PM me your address and I'll pop them in the post). Alternatively someone can probably provide a link to a supplier, I'm sure.
Click to expand...

Thanks, Richard, I inherited a couple of those strips from somewhere. I had thought they were meant for some sort of cable connector, but that's excellent that the TO92 legs fit in and out so well. Unfortunately, the PCB would have to be designed for them. They're too widely spaced for the inline ZTX holes on the PCB, and installing them one per hole for the various BC transistors would've been a big PITA.

Maybe Graham's right, and it's just not worth the worry. Then again, if Les is considering a gen 2 PCB, it would be a nice touch to design for the spacing of these headers.
 
GLARING ERROR..!! I'm now advised, and I have checked to verify that the BD237 transistor
does NOT have an isolated case and should be insulated when mounting by a small mica pad

Sincere apologies to anyone caught out by my not checking.
 
LesW said:
GLARING ERROR..!! I'm now advised, and I have checked to verify that the BD237 transistor
does NOT have an isolated case and should be insulated when mounting by a small mica pad

Sincere apologies to anyone caught out by my not checking.
Click to expand...

Good shout Les..

You can use the DB237STU which is a fully encapsulated incarnation which works without the need for isolation. But I did put a drop of paste on the back just to make sure of thermal integration.

41345063202_42f03f8ed4_b_d.jpg
 
I noticed "Pin 4" on the backside of the BD237 and placed a pad as a matter of course. The case itself is nonconductive. Inside the bolt hole, there are 3 places where Pin 4 is exposed, but the bolt is protected from them by a layer of plastic. So this looks to be fine.

BD237_mounting-1.jpg
 
Right then.....Ongoing development has encouraged me to expand this project within the membership of PFM

To that end, I have 3 more sets of circuit boards along with the hard-to-find bits and bobs available to bona
fide builders to make NCC300s for themselves. Freebies they will be and going to the first 3 constructors to
contact me with genuine requests but believe me, I know who you are.

In the interests of open and fair dealing, no-one is disqualified from applying, techncal merit is all that counts.

Get to it.......
 
Pecking order so far:

Edd9000, R J Harker

One more........

OK, leniency time....Ramona and Kenb have slipped in under the wire

Book's now closed chaps.

Addresses from those listed - [email protected] - if you'd be so kind.
 
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I was hoping that someday pcbs will be available, since I'm not a regular lately I don't think I'll be on the list, so my question is: will they be available in any form for the rest of us ?
With Pass XO now almost at hand, I'm going active and I need something to put next to my NCC200 (which now sings better than before with Salas preamp).
TBH I was expecting from Les to sell them only in kit form as upgrade to Naim users (harvesting the fruits of his development)
 
Hello! I’m new here. I have been reading here for a while but first time posting. Been modifying my nap110 (and building synths, preamps compressors etc for some years) and I guess I now want to build an amp from scratch and this project looks very interesting. If pcb’s of this will come available for buying I would definately be in to buying a set! -Wille/Finland
 
Both of mine are complete and sounding excellent now
When i first set my Bias Voltage to 2.1 the sound was a a bit veiled and bass muffled so I checked the bias Voltage and current.
For 2.1 V I only had 15 & 18 ma bias current so way under biased
Turning up the Bias current started to ramp up as the driver transistors switched fully on.
2.2V gave me 110ma
2.23V gave me 120ma
2.3V gave me 220ma
I settled on 120ma for now and the sound was transformed to sounding transparent, bass has clout now and string tones are superb
Again this is still early days in the running in process and i will check again in a couple of days and maybe try pushing the bias current a little more as the heat sinks are still only hand warm even after plating music all day :)
So this reinforces Les's note to make sure the driver transistors are fully switched on.


Some picks

IMG_3318 by Alan Towell, on Flickr

IMG_3322 by Alan Towell, on Flickr
IMG_3320 by Alan Towell, on Flickr

20180411_162721 by Alan Towell, on Flickr

20180411_175915 by Alan Towell, on Flickr


IMG_3322 by Alan Towell, on Flickr
20180411_162919 by Alan Towell, on Flickr
Alan
 
Sweet, Alan! Those look to be the ultimate Voyagers. My NAP135 heat spreaders are running 33° playing music. Some of the earlier stuff (MJEs, ZTXs, and other transistors) are running more like 43°, but all boxed up, the cases are still pretty much room temp. I still need to insert the watt meter, but given the low heat, I'm expecting it to be reasonable.
 
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