Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › "White Noise Head amp kit"
New Posts  All Forums:Forum Nav:

"White Noise Head amp kit"

post #1 of 682
Thread Starter 
Latest

To save any new people having to trawl through over 600 posts the WNA is now supplied as a complete kit for £150.. details here the kit includes everything you need to build the complete amp and even comes with a PSU... it uses top quality parts and is the best amp I have heard. For those of you who want to find out the history of how the amp has evolved and improved over the past year then start here:


I've today taken delivery of the White Noise Audio (WNA) headphone amp kit after threatening to try it out for the past couple of years.

As you'll probably know, I've spent the past 2 years tinkering with the Chiarra and assisting Graham Slee with the mods to his "SOLO" amp and haven't had much time to dedicate to anything else (amp wise)

I was first made aware of the WNAHA (white noise audio head amp) a couple of years back and always meant to give it a try but never seemed to get round to it..... It's another one of those "unchartered territory" amps, like the Chiarra was at the time, and to spend money on the kit is something of a gamble as there's not a lot of information about it on the web and, as such, I was reluctant to give it a go.

Well, life is too short to "wonder" and I've taken the first step and purchased a kit and will be reviewing the completed amp in due course. I have spoken with the designer, David White, and am impressed with his philosophy and his electronics knowledge and his design.

Full details of the WNAHA kit can be viewed at http://www.wnaudio.com/cat.pdf (page 17)

The WNAHA "appears" good on paper and the PCB slots directly into a Hammond but will it be able to compete with a Chiarra or a PPA? All will be revealed shortly.

I'll poplulate the board next week sometime and will report back, in full, with my findings once the amp has had a chance to break in.

In the meantime............ a sneak preview of a 5% populated WNAHA in a Hammond enclosure........... imagine it fully populated with Stepped attenuator and OPA 627 etc........... looking good.





Pinkie.
post #2 of 682
Looks interesting. did you get the audiophile or standard kit?

I look forward to your review...
post #3 of 682
Nice one Pinkie!

I don't recall seeing this amp mentioned on Head-Fi before. It will be interesting to read your impressions.
post #4 of 682
Thread Starter 
Quote:
Originally Posted by damitamit
Looks interesting. did you get the audiophile or standard kit?

I look forward to your review...
I just bought the PCB, 4 constant current diodes, 2 x 12V 60mA wire ended incandescent lamps and a gold plated headphone socket from WNA.

I'd probably have been as well ordering the complete kit from WNA as it took me like 3 hours to source the parts from Rapid electronics / maplins etc. I managed to get everything though and am just waiting for it all to arrive

Also going to order one of WNA's stepped attenuators as the conductive plastic pot I was going to get from RS components was out of stock (bloody typical!) I've never used a stepped attenuator before so it will interesting to see how it performs in relation to a carbon pot.

Pinkie.
post #5 of 682
Been using one for some time now. It's a satisfactory piece of kit which I'm happy to live with but I won't steal PF's thunder.... I might follow up his review with a few comments at a later time.
post #6 of 682
Thread Starter 
Quote:
Originally Posted by buggalugs
Been using one for some time now. It's a satisfactory piece of kit which I'm happy to live with but I won't steal PF's thunder.... I might follow up his review with a few comments at a later time.
Feel free to steal my thunder Buggalugs, it'll save me a lot of typing


What op amps are you using, are you using a stepped attenuator and what do you mean it's a "satisfactory piece of kit"? does that mean "it does the job" or "it does the job and then some" or "It's ok but nothing special" etc. etc. ?

The instructions are great up to a point but omit to tell you where to connect the potentiometer on the board........ did you find this also or am I just being thick?


All the best.



Pinkie.
post #7 of 682
Yes I'd better clarify what I meant by the word satisfactory - firstly this amp bears a marked similarity to a circuit from the UK magazine Elektor published about a dozen or so years ago so I would't say it's at the cutting edge of current thinking. It is an ultra simple circuit buffered with a complimentary pair of transistors (the ubiquitous BD139/140) contained within the feedback loop of the opamp and biased into class A with constant current diodes. No attempt is made to bias the opamp into class A, which Dr. White considers more trouble than it's worth.
Nonetheless those of us who have made headphone amps over the years may have found that less is often more in terms of quality and therein lies the strength of this amp. It is very direct, clear and dynamic. I have slight reservations about the overall quality of reproduction which IMHO slightly hardens up when the source material becomes complex and loud. Others may not notice this ( I am being hyper critical).
This is why I was hesitant about going over the top with my initial response. However if I applied a personal subjective scale for amps I have currently on hand for comparison I would put (out of 10) the headphone socket of my main amp on 4, my CMOY on 5, my maxed out Meta 42 on 6.5 and the White amp on 8.5.
Dr White himself feels marginal improvement would be gained by using a darlington pair of transistors in the output stage to improve linearity; pity he's not thinking Mosfet!
One thing I really do like about the circuitry is the very elegant on-board rail splitter which is quite unlike anything I have seem in these forums. It really does supply an ultra clean and really "stiff" supply making all the battery amps I have on hand sound thin and wimpy.
When I built this amp I didn't use input caps (never do in fact - if you need them then your source must be suspect in my view). I soon removed the lamp bulbs used as output protection and gained another half octave of bass extension as a result (I substituted them with 4.7r resistors and I make sure that the phones are not plugged/unplugged when the amp is switched on to avoid transient short circuits).
Regarding op amps I like the AD8610 better than OPA627 and this is my current choice. I find the OPA627 sounds like an old man mumbling into his beard compared with the startling definition and clarity and detail rendition of the AD8610.... a real champagne quality with this device. Of course the opamp is everything with this type of circuitry - as it will be with the Chiarra.
Pink Floyd - you mention that there is no space on the board to mount the pot or attenuator. I'm afraid that's correct - you'll have to mount it separately and wire it up with flying leads which is a bit of a pain. In fact you may have trouble shoehorning all this lot into the enclosure you picture so good luck mate!
Do make it up and post one of your inimitable reviews - I'm absolutely sure you'll be impressed by it.
post #8 of 682
Thread Starter 
Hi Buggalugs,

You were right! a shoehorn is required to get everything into this enclosure

I've managed to work round the headphone socket and will fit C2 underneath the board (plenty of room) I fitted the LED and bezel (being replaced with a blue one. that red thing looks like a big cherry!) directly above the headphone socket to give me more room on the front panel for a biggish volume control knob.

Unfortunately, my plan for a stepped attenuator won't be going ahead as there's definitely not enough room (see pic)



As you can see C4 and C6 (not yet fitted) would get in the way. as would the transistor and electrolytics :-( I've been hunting about for a suitable alternative and have only managed to find a Spectrol 12mm conductive plastic pot at £6.08. It's a "linear" pot and I'm wondering if I'd be better hunting for a log variety? David white reckons 10K is the way to go...... to be on the safe side would 20K be ok? Are you using a stepped attenuator in yours?

All I have to do now is to source a decent pot, fit all the caps, fit heatsinks onto the transistors and wire the amp up (that'll be fun!)

Oh well, that's the state of play so far and I should get round to completing it by the end of the week with a bit of luck. It's a pity the stepped attenuator wouldn't fit into the enclosure but I think I'd prefer a conductive plastic pot in a compact enclosure rather than a stepped attenuator in a big ugly behemoth of an enclosure

Here are a few pics of the progress so far (about 2 hours work)

By the way, do you have any pics of yours? It would be great to have a look at the wiring as there are no instructions in the manual on where to connect the pot to I assumed there would have been provision made on the PCB (ie 6 pads) for the potentiometer connection but obviously not I'm sure it's "figureoutable" but that's definitely a very weak part of the instructions and a diagram showing the pot connections would have been very welcome. Apart from that, the instructions are superb.







post #9 of 682
Hiya Pink. I used the next size up Hammond case from the one you have which made assembly a whole easier.
Regarding pots I'm using a 47k alps pot merely 'cos I had one available in my box of spares; I'm no expert on these things but intuitively I feel 10k or 22k one would be a slightly better choice. I quite fancy the stepped attenuator option and may go down this route at some stage. Just on this matter of pots I have a 100k pot extracted from a previous (thermionic) project which cost me over £40 from Audionote about 10 years ago; this very expensive pot (purportedly the bees knees at that time) measures OK at minimum setting but after a 10% turn measures 111k in one channel and 96k in the other! What a stitch up!
By the way Rapid electronics in the UK were showing Alps pots available at 6 quid apiece and in stock until recently.
I wonder - are you going to use your Andante supply for this amp? - it should do the trick well. Funnily enough I have a very early Andante power supply here myself which is gathering dust in my attic but since I have a marked preference for the AD8610 it pushes out just a bit too much voltage for that chip, so I use the excellent 24v wallwart sourced from David and duly populated the rail splitter section on the board.
If you use a + 15v - 15v supply David recommends that heat sinks are required for the output transistors; I'd suggest you don't get those clip on sinks from Maplin which are crap and tend to fall off but merely bolt on some small pieces of aluminium sheet which will be entirely adequate.
One other observation - David bangs on on his web site about the benefits of gold plated input/output connecters but what does he supply with his kit to couple up the signals? - nothing less than risible little tin plated plugs and sockets. I gained a vast improvement in sound quality by hard wiring my cabling directly to the pins and omitting the plugs.
I've just moved house and haven't got round to unpacking my digital camera; when the dust/blood pressure settles I'll try and get round to supplyling some pics.
post #10 of 682
Just re read your post Pink. Don't even think of buying a linear pot unless you want to ponce around with law faking resitors or shunt resistors... I should know since I wasted many an hour trying to optimise the values for these!
post #11 of 682
Thread Starter 
Quote:
Originally Posted by buggalugs
Hiya Pink. I used the next size up Hammond case from the one you have which made assembly a whole easier.
Regarding pots I'm using a 47k alps pot merely 'cos I had one available in my box of spares; I'm no expert on these things but intuitively I feel 10k or 22k one would be a slightly better choice. I quite fancy the stepped attenuator option and may go down this route at some stage. Just on this matter of pots I have a 100k pot extracted from a previous (thermionic) project which cost me over £40 from Audionote about 10 years ago; this very expensive pot (purportedly the bees knees at that time) measures OK at minimum setting but after a 10% turn measures 111k in one channel and 96k in the other! What a stitch up!
By the way Rapid electronics in the UK were showing Alps pots available at 6 quid apiece and in stock until recently.
I wonder - are you going to use your Andante supply for this amp? - it should do the trick well. Funnily enough I have a very early Andante power supply here myself which is gathering dust in my attic but since I have a marked preference for the AD8610 it pushes out just a bit too much voltage for that chip, so I use the excellent 24v wallwart sourced from David and duly populated the rail splitter section on the board.
If you use a + 15v - 15v supply David recommends that heat sinks are required for the output transistors; I'd suggest you don't get those clip on sinks from Maplin which are crap and tend to fall off but merely bolt on some small pieces of aluminium sheet which will be entirely adequate.
One other observation - David bangs on on his web site about the benefits of gold plated input/output connecters but what does he supply with his kit to couple up the signals? - nothing less than risible little tin plated plugs and sockets. I gained a vast improvement in sound quality by hard wiring my cabling directly to the pins and omitting the plugs.
I've just moved house and haven't got round to unpacking my digital camera; when the dust/blood pressure settles I'll try and get round to supplyling some pics.
Hi Bug,

I'm starting off by putting a kinda basic kit together first to see what it sounds like and will report firstly and foremost on the standard amp. I'll start with OPA134 opamps then go to OPA 627, AD8610 etc etc. It's only fair for other DIY'ers to learn about the standard kit first and, if there are improvements that can be introduced further down the line then all the better. I've got all the Burr Brown and Analogue devices chips that can possibly drop into the WNAHA at hand and will experiment over the next year or so :-)

My "major" concern at the moment is with the instructions (or lack of) regarding connection of the headphone socket and the potentiometer. I expect clear instructions from start to finish and the provider of the kit should (at no stage) assume the builder knows / understands what's required... builders of kits range from the absolute beginner to the very experienced and the instructions should cater for the absolute beginner as well as the seasoned pro's.

I've brought this to David's attention and he'll hopefully address the issue in the immediate future......... I won't connect the headphone socket and pot up until he sends a diagram in case I short circuit something

Pinkie.
post #12 of 682
Pinky, Rapid Electronics sell the ALPS Blue, it's order code 66-0225 for the 50K version, at £8.50

g
post #13 of 682
Thread Starter 
Quote:
Originally Posted by guzzler
Pinky, Rapid Electronics sell the ALPS Blue, it's order code 66-0225 for the 50K version, at £8.50

g
Hi G


I know.......... it's too big for the enclosure :-( Thanks for the steer toward rapid btw.......... fantastic firm

Mike. looking fo a 12mm conductive plastic pot........ dual log 50K preferably
post #14 of 682
No conductive plastic, but anyway:

1) Farnell has a 9mm Alps dual that should fit just fine. Quality is OK without being outstanding in any way Some claim that they track horribly but I haven't had any problems with the ones I've used (just a few, but still)

2) Guzzler might still be hiding a few Panasonic EVJ's somewhere The quality is a bit better than the Alps and it should fit as well. The only problem is that it is difficult to work with if you want to solder wires directly onto the legs

/U.
post #15 of 682
Thread Starter 
Quote:
Originally Posted by Nisbeth
No conductive plastic, but anyway:

1) Farnell has a 9mm Alps dual that should fit just fine. Quality is OK without being outstanding in any way Some claim that they track horribly but I haven't had any problems with the ones I've used (just a few, but still)

2) Guzzler might still be hiding a few Panasonic EVJ's somewhere The quality is a bit better than the Alps and it should fit as well. The only problem is that it is difficult to work with if you want to solder wires directly onto the legs

/U.
I've found a superb Bournes pot which Dr. White recommended (silky smooth and the business) I'll reveal All soon (as if!)

Pinkie.............
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › "White Noise Head amp kit"