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Possible B4 Buffer Improvements

As I think this is the thread to post my queries on improving my B4. Let me elaborate on what I've done so far so that you can help me. Forgive me for my questions not being so refined as those in debate so far.
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http://s449.photobucket.com/albums/qq212/angartal/
http://i449.photobucket.com/albums/qq212/angartal/Imagen052.jpg

1,. PSU. 50va toroid with 40va 12-0-12v or so devoted to B4 circuit + 10va 10v-0 to power the input selector relay circuit. I had it in my bits box.
Query -none except that I'd try an R-core in the future
1.2 Smoothing: Hacker generic rectifier board sporting 8100uf per rail (Gold Muse 2200uf x 4 boutique caps preceded by 2x 4700 ordinary Nichicon)with fast diodes and RC filtering with only R47 resistor value
query: Shall I up the resistor value? I have no scope to analyse the supply.
2.-Input selector kit. Bought from ebay shop -can't remember who from.
Good Matsusita silver plated contact relays; but all signal coming in
share mono ground which I then split in two stereo wires and then go star grounded in the B4 Pink Fish approved circuit board.
query Shall I discard this kit because of this grounding trick? Any suggestions?
3.- B4 board stuff: Bom as per PINKFISH. Input cap 3.3 WIMA. output cap 2.2uf policarbonate film EVOX from a charity auction run by Les.
Polysterenes are COPPER POLYSTERENES from Tubeshunter as well as the J501 diodes
Vol pot- NOS 20K Noble new
Query Are Polypropilenes to be prefered at the output? Are these polysterenes the right stuff?
Here you food for thought/debate
Cheers
harthold
 
This is as good a place as any to post/discuss your queries. The traditional pecking order for caps in audio (in order of improved quality) goes

Polyester
Polycarbonate
Polypropelene
Polystyrene
Teflon/PTFE

There will be good and bad in each category and overlaps in perceived quality as a result. Generally speaking foil is preffered to film (where the metal is sprayed onto the plastic).

Of course as you go down this list for a given value, the caps get both larger and more expensive. There is also a degree of tuning and balancing between the caps in a piece of kit and after a bit of swapping you start to get a feel for the ones you prefer.

I would go for polyprops , polystyrene or even better if you can find them teflon for both the input and output caps. I struggled to find a big enough teflon for the output and the Russian 0.47uf I have on the input took an age to arrive from accross the Urals. I find Teflon to be the most transparent sounding yet as detailed and balanced as any other. Polystyrenes are nearly as transparent and have a sweet top end but can appear a little light in the bass. Polpropelenes vary greatly IMHO and I haven't used the really pricy ones such as the Mundorfs.

Inaddition to all of these there are the various boutique caps with silver /gold in oil wnd with various dialectrics. These are out of my reach but I'm willing to believe some of the hype about them given their frequent use in Tube amps and reputation. Here's a site i trust for reviews on these:

http://http://www.humblehomemadehifi.com/Cap.html

I don't know the answer to your other questions as I haven't experimented enough in these areas. I would agree with you on the R Core though, and if you are going to run multiple earth runs from two common grounds keep the loop area between them small, i.e twist them together, to reduce any slight possibility of earth loops - someone will probably tell me that this is insignificant in a minute.

BTW your layout style looks similar to mine but a lot tidier. The big caps really mess the layout up.

John
 
Hi John,

Whats the input impedence of your Nap135 clones? 22k?

Is it bad to have 100k plus 0.47uf on the B4 input, when the Naim input is 22k? Does it matter at all?

I'm looking forward to starting building this amp! Do you really think that it has bettered your NAC52?
 
John, I've cracked open one of the smaller .22uf russian cap and the 1uf with the moulded teflon end caps, they are both very tigthly wound true teflon film and high quality polished foil caps.

I used them extensively in my Prefix for decoupling and bypass duties, and never ever found them to show any microphony when attached to the scope and 'flicked' when passing steady state signal. As far as i can tell the ones i have are utterly none microphonic. If they are going to show up anywhere, it'll be in a 60db circuit.
 
Hi Bennynoyph,

I've got no input cap on my NAP clones so i think it is 22k in parallel with 100k, about 18k ohms at the input. This has a small effect on the output DC offset but is no problem otherwise. I may remove the 100k to sort this out.

My B4 has a 3uF teflon on the output so there's no offset there or at the input to the power amp. Still have to be a bit careful when plugging things up as the cap discharges with a thump into the amp. The DC offset before this B4 output cap is circa 60mV due in part to the high input resistance of the B4 as you imply, but this doesn't unbalance the B4 output stage significantly.

I am absolutely sure the B4 betters the NAC52 on single CD input sound quality, but it is obviously less versatile with no remote, no tape buffer or MM/MC input option, or even case as things stand! However as I never really needed any of these aspects of the NAC52 I sold it for a sonic upgrade to the Starfish and now the B4.

John
 
Hi sq225917,

That's interesting. The ones I have on the input are 0.47uF FT-3 types. They seem to pick up hum easily and their orientation and proximity to the PSU is important. It may be that I mistook this for microphony as when I insulated them I also moved them further from the PSU. I have read that they do sound better without their cases though - smoother apparently. The same person reported that a smaller cased teflon FT-3 as a bypass improved the very top end of them when they were uncased giving an overall improvement. I can dig the link out if you want. Anyway I think I may have been a little hasty in my conclusions on these its only been 3 days.

There are also reports of people damping the cases of the FT-3 caps with tape and getting improvements though given your findings with 60dB of gain I think this is questionable.

The output caps I'm using a from Hong Kong and are 3 uF Teflon in Oil, housed in a steel case. They are made by CRC ?? Chinese perhaps? Now these have both the hum problems and are microphonic. After start up I can reduce the hum a lot in the long term just by temporarily grounding their case but the microphonics is reduced by putting the case on compliant material rather than a hard surface.

Next week I'll drag the scope to the lounge and do some objective tests on both sets of caps to see if I have done any harm.

I must admit I do like the Teflons sound though. Real quality at low cost.

John
 
I've literally only just purchased 10 of those exact caps from another Russian seller. They are the ones widely recommended for bypass use, and the caseless construction perhaps explains that. The 1uF ones are very hard to find, in fact I've failed. Do you know where they can be found?
 
Haven't seen the 1uf in ages. I have one left in my spares box- wishing I hadn't sacrificed one at the alter of knowledge now.
 
Has anyone placed their power-supply and B4 boards in separate aluminium enclosures? Would there be any benefit to this?
 
I can't see the need. The pre doesn't need a huge power supply to work well and I can't detect any issues in the 50Hz area with my set up.
 
Harthold, I've used the 1uf version of the 2nd cap you display, they are good caps. I have a few spare if you only need a couple.
 
I've ordered some 22nF Teflons to try out as bypass caps for my larger (3uf) Teflon in oil ones in use as output caps. I've read mixed reports of their effect but would like to make up my own mind on these.
 
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