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"White Noise Head amp kit" - Page 2

post #16 of 682
Hi Pinky, I saw the gold plated headphone socket used on your casing. I have the same socket I ordered from Farnell, but when I received it, it doesn't fit the normal 3.5 mm headphone jack. The normal headphone jack is too short for the socket, so when pluged in, the ground and the right channel (middle contact of the jack) is shorted, and the jack's tip only reach the 2nd contact of the socket. I expect the tip should reach the last contact.

How about yours? Does it fit a normal 3.5mm headphone jack?
post #17 of 682
Thread Starter 
Quote:
Originally Posted by bpribadi
Hi Pinky, I saw the gold plated headphone socket used on your casing. I have the same socket I ordered from Farnell, but when I received it, it doesn't fit the normal 3.5 mm headphone jack. The normal headphone jack is too short for the socket, so when pluged in, the ground and the right channel (middle contact of the jack) is shorted, and the jack's tip only reach the 2nd contact of the socket. I expect the tip should reach the last contact.

How about yours? Does it fit a normal 3.5mm headphone jack?
The one I have is a 6.3mm socket and the 6.3mm jack plug fits into it perfectly. Have you got a link to the socket you bought?

All the best.

Mike.
post #18 of 682
Thread Starter 
Quote:
Originally Posted by buggalugs
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).
Yes, I'm not too keen on the lamps myself. I measured their resistance with 4 independant meters (to be sure I got an average reading) and here is what they measured:

21.7 ohm
21.2 ohm
21.9 ohm
21.3 ohm

So, if I substitute the incandescent lamps with a 22 ohm 0.1% 15ppm/C resistor we should be rocking ?
post #19 of 682
Thread Starter 
Quote:
Originally Posted by buggalugs
I wonder - are you going to use your Andante supply for this amp? - it should do the trick well.
No, I'll either use the superb £7.95 regulated PSU from http://www.rapidelectronics.co.uk/rk...2001&XPAGENO=1 or I'll use the Graham slee PSU1 (24V)

Quote:
Originally Posted by buggalugs
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 prefer to hard wire to the board also.......... I found the large section of
the manual relating to "latching pins and plugs" a tad convoluted and that section could have concentrated on how to connect the darned amp up to the headphone sockets / pot etc etc........ to heck with "latching pins"




Quote:
Originally Posted by buggalugs
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.
Don't "try" make a point of doing it... nothing quite beats amp pRon
post #20 of 682
Thread Starter 
Phew! Things sure are getting tight inside the enclosure with, literally, 1 millimetre to spare in places I've still got to fit the 3 x 100nF polyprop caps (waiting for them to arrive) and then it's a case of wiring everything up and (all being well) listen to the amp!

I decided to go for a Bourns 91A2A-B28-D15 10K Log potentiometer and, fortunately, it's a perfect fit I've also replaced the Red LED with a blue LED so that should dress the front panel a bit better.





post #21 of 682
Beautiful! Very neat indeed!

I'll get one of those Hammond 4511 series for my next project.

May I know what potensiometer you use in the box?
post #22 of 682
Thread Starter 
Quote:
Originally Posted by bpribadi
Beautiful! Very neat indeed!

I'll get one of those Hammond 4511 series for my next project.

May I know what potensiometer you use in the box?

The potentiometer is a 10k dual log Bourns 91A2A series which is apparantly a very good pot indeed. I haven't hooked it up yet but it's certainly got a silky smooth action and feels a lot better than the ALPS blue velvet.... there's hardly any shaft resistance although there's a slight degree of side to side free play between the shaft and housing which probably accounts for the silky smooth rotation.

Some potentiometers tolerances are so tight, between shaft and housing, that it feels as though you're torquing up a cylinder head every time you turn the volume up or down........ not so with the Bourns 91A2A series it's smooth and silky from the first rotation but not sloppy although, after a few years rotational cycles, it "may" become sloppy.

I've noticed that pots with a tighter shaft to housing tolerance "bed in" after a while (much like pistons in a car) and tend to loosen up ...... the Bourns 91A2A feels like a pot that has already been "bed in" and this is why it feels so silky smooth in operation. In reality, the Bourns tolerances "may" not be as exacting as other manufacturers (in the shaft to housing department) so you may get a 91A2A with a tight shaft, a medium tight shaft or a loose shaft........ It could be that they are manufactured to very "precise" tolerances to ensure that each pot has that "old glove" feel (much like stonewashed jeans) and that's what I'd like to believe........ I'd hate to think that buying a Bourns pot was a case of "pot luck"

Anyways...... so far so good! A very smooth pot and a welcome change from the stiff ALPS Blue Velvet (which becomes smoother over the years).......... Now, just a case of listening to it in action.

Pinkie.
post #23 of 682
Thread Starter 
Quote:
Originally Posted by buggalugs
No attempt is made to bias the opamp into class A, which Dr. White considers more trouble than it's worth.
Hi Buggalugs,

Dr. White has been hard at work and has come up with a really eloquent solution for biasing the opamp into class A which involves simply replacing 2 components on the board

I quote Dr. White from a recent e-mail: "If you want to bias the opamp output stage 2mA into class A then change I2 from a 3.5mA to a 5.6mA constant current diode and change R6 from 120R to 75R. In earlier versions of the headphone amp R6 was 56R, in this case reduce it to 36R. Everything else stays the same. The class A bias is simply the difference in value between the two constant current diodes, 5.6 - 3.5=2.1mA, and the change of the R6 resistor value keeps the quiescent current the same in both output transistors. The class A bias current is drawn from the negative supply rail."

So there you go Buggalugs...... a simple 2 component mod and your opamp is biased into Class A :-) I'll be ordering the parts today.

I still haven't connected the amp together as I'm waiting for the 100nF caps to arrive (should be here tomorrow) once they arrive I'll connect everything up and get down to listening to the music I've ordered 6 browndogs from Tangent and, once I've soldered the chips onto them, I'll be auditioning the following in the White Noise amp:

OPA 134 PA
OPA 627 BP
AD 825 AR
AD 8610 BR
AD 8065 ARZ

I just can't wait for the caps to arrive as this looks like one "seriously" good amp and my ears are twitching in anticipation

All the best

Pinkie.
post #24 of 682
Thread Starter 

White Noise Audio amp completed.

At last, the parts I were waiting for arrived and I've completed the White Noise Audio amp. It worked from first switch on but all was not well with the Bourns potentiometer . It only started to kick in around the 11 o' clock position and I thought I must have wired it up incorrectly, I looked at the connections and all appeared ok so I whipped the pot out and tested it with an Ohmeter between pins 3 & 2........ The resistance stayed at 10K all the way up to the 11 o'clock position and only started to fall after 11 o'clock.

EDIT: Farnell have inspected their entire batch of these pots and they are indeed defective so their batch will be sent back to Bourns for inspection. I've ordered a Vishay PA11 as a replacement.



I had another Bourns pot but it suffered the exact same problem so they will both be returned to Farnell tomorrow for a refund. The only other pots I had to hand were a cheap Omeg 10K and a small Vishay 10K..... I fitted the 10K vishay and it worked great :-) I'll source another pot to replace the vishay but I doubt it'll be another Bourns pot...... not a good first impression with 2 of them exhibiting the same fault :-(



First impressions of the amps sonic capabilities are very good indeed. I'm using a pair of opa 134 PA's at the moment (far from ideal and probably TI's most chocolaty sounding op amp) but even with the OPA 134 PA's onboard I can detect an underlying well of sheer class which is just shouting out to be fed a decent op amp to allow it to flow to the surface. I think this little amp is going to prove to be a giant, if not a giant killer.

Dr. White favours the LM6171 and has recently been working around optimising the WNA head amp to accommodate the LM6171 which he says "enables you to pick out each individual voice in a choir instead of the entire choir sounding like one voice" now that sounds like the op amp for me!!! If there are any fellow WNA head-amp owners reading this who would like to try the LM6171 ...it's a simple case of replacing R4 (220R on both channels) with a zero ohm link which will ensure the LM6171 will not oscillate. In fact, Dr. White recommends the R4 resistors are removed (whatever op amp you are using) as he finds the op amps perform better without them in the circuit..... I told you he'd been hard at work!

The removal of R4 (220R) along with the op amp class A mod (see post above) and LM6171 op amps apparantly transforms this amp into a totally different kettle of fish (a kettle of caviar perhaps ;-)

I've built the amp in it's basic guise and it sounds absolutely fantastic and I'd be happy to enjoy the music through it as it stands......... Dr. White has been hard at work the past couple of weeks trying to squeeze the last ounce of performance out of his design and I'll put his latest revisions into place before fully reviewing this amp in the Head-Fi amplification section and at http://www.rock-grotto.co.uk/xcanpropage.htm

One thing is absolutely certain....... This is a superb kit that's easy to build, very reasonably priced and, as such, should be added to your shortlist if you're considering building a kit amp.

All the best.

Pinkie.
post #25 of 682
Thread Starter 
It's amazing just how long a dodgy potentiometer takes to be accepted as "dodgy" by a company :-(

I've tried two of the Bourns 91A2A's from Farnell and "both" have failed to drop any resistance from the 7am position up to the 11 am position (no sound at all until the volume hit the 11am position)

After 2 weeks of alerting them to the "fact" that I was in receipt of dodgy pots they finally concede that "there may be something wrong with them" and they are sending their entire batch back to Bourns for "inspection"

Farnells "technical" call operative stated that "logarythmic pots don't kick in until the 12pm position on the dial" hmmmmm...............

Once I managed to bypass this neanderthal things got better and I was put onto someone called "Tim"..... "Tim" explained that I would be better with a linear pot as the measurements I were quoting were clearly ok as far as he was concerened and he suggested I "re-educate" my ears and adapt to a linear pot.

To cut a VERY long story short, Farnell's entire batch of 91A2A's have been sent back to Bourns (6,000+ pots) as they are clearly faulty........... I asked them for a suitable replacement, considering the circumstances, and they came up with the Vishay PA11.

I was actually asked to "pay" for the PA11 !!!!!!!!!!!!! "pay??" ............... after much "to do" they agreed to send me a free PA11.

Big deal! I alerted them to the fact they were supplying dodgy pots and, basically, I did their QA job for them.............. I think a free pot as a gesture of goodwill for all the hassle and time wasted faffing about with these faulty pots is the least they could do.

Should have the Vishay pot fitted soon and will report back on it
post #26 of 682
Sounding good! Any initial comparisons to our beloved PPA?

-Z
post #27 of 682
Thread Starter 
Quote:
Originally Posted by Zemo
Sounding good! Any initial comparisons to our beloved PPA?

-Z
Hi Zemo!

I really haven't had an opportunity to compare the White Noise Head-amp to anything, as yet, as Dr. White is hard at work coming up with revisions to his design and I am putting them into place in the amp as soon as he comes up with them so, at the moment, I'm basically evaluating the improvements the mods have made over the standard kit amp (these mods will be incorporated in future kit amps so I believe)



Dr. White has been experimenting with numerous opamps and and reckons the LM6171 brings the best out of the amp. He's been optimising the circuit to bring the best out of the LM6171 and I am awaiting a couple of LM6171's to give them a try........

As soon as the amp is fully populated with all the revisions I will get down to listening to it. I can already report that in it's standard guise with OPA 134 opamps it sounded pretty ordinary (good but nothing spectacular) the class A opamp biasing improved things very slightly. Rolling in a couple of AD8610's brought about a pretty dramatic improvement to the sound and, apparantly, the LM6171's will bring about an even more pronounced improvement to the sound.

The Vishay PA11 arrived today and works great! It's not as smooth as the Bourns and you can actually hear it squeaking when you rotate the shaft..... pretty tight but I'm sure it'll soon bed in :-) It may be my imagination but I believe it has made the amp sound a bit more "open" could be something to do with the gold conductive elements / legs maybe?



It's a pity that I can't show a photo of the "entire" amp. I've had to mount some of the components on the underside of the board due to the lack of space (my fault for being arrogant and insisting that it would all fit into a Hammond 1455K1202 enclosure!) I'd have been a lot better going for a Hammond 1455N1602, that would have given me enough room to mount a stepped attenuator and more space to route the wiring etc. Oh well, I was warned but chose to shoehorn everything (carefully route ) into a compact enclosure.

Underside of board:
post #28 of 682
Thread Starter 

Amp finally completed!

At last, the lid will be fitted onto the amp as it's now finally complete


Compact enclosure

The LM6171's were fitted into place and the input caps were removed and 2 50uF bi polar output caps were fitted. Dr. White said the LM6171's made a big difference but I didn't expect the difference to be "so" enormous!


WNA with LM6171's on board

When I fired the amp up my jaw dropped to the floor, Dr. White sure has managed to get every last ounce of performance out of the LM6171, instead of listening to the music as a congealed mass of instruments and voices I found myself listening to individual performers and individual instruments.... so much space around the performers and so much clarity and detail.......


Overhead view

The introduction of the LM6171's has transformed this amp from a "good one" to "the best I have ever heard" without a shadow of a doubt. The energy, the impact, the slam, the clarity..... it's got everything you always wish a headphone amp would give you.

I played a favourite album (Roger Waters "in the flesh") 3 times (yes three times, that tells you a bit about what this amp is about!) and it was honestly like being back at the concert..... pretty surreal in fact.... it felt as if I was sitting in the audience and the applause and "whooping" (must have been an American audience ) was coming from behind me, in front of me and from left to right....... there was also one instance during "shine on you crazy diamond" where a member of the audience shouted "god damn" into my right ear (track 11 - 3:02 minutes in) I have "never" heard such clarity on this recording before which is why it's now playing for a 4th time....... I can't believe the bags of information I'm hearing through this fantastic amp.



The goosepimples have been up and down on my neck like a yo yo these past few hours and that's without the aid of alcohol and in the daylight hours...... I can't wait to hear this amp once the sun sets!

It's just soooo musical, so real sounding and it's streets ahead of any headphone amp I have ever listened to. I was a great lover of the Williams Hart Chiarra before I listened to the WNA with LM6171's and I'm sorry to report that the WNA absolutely trounces the Chiarra (sorry because Shaun Williams is a great guy and, through our telephone conversations re: the Chiarra, we have become good friends) I'm sure Shaun will respond with a "super Chiarra" but, until that day arrives, the White Noise Audio amp is (by far) the best I have heard to date and Dr. White's work on biasing the opamp into Class A and optimising the circuit for the LM6171 has borne fruit.

I'll review the sonic attributes of this beauty in the amplification section once 500 hours of music has passed through the circuit. My impressions so far can be marked as follows: (some amps are from memory but amps I currently have in my possession include: MF X-Can V2 Pink modded, Chiarra, GSP Solo 2004, B-Tech BT928, MINT (in a Hammond)

Musical fidelity X-Can V2: 4 / 10

Musical Fidelity X-Can V2 with pink mods: 5.5 / 10

Chiarra with OPA627 / Silmics: 8 / 10

GSP audio SOLO: 7 .5 / 10

B-Tech BT928 (with elna caps) 2.5 / 10

MINT (in Hammond enclosure) 3 / 10

White Noise Audio 9 / 10


Before I review the White Noise Audio amp in the "amplification" section I'll send it to Nigel, another head-fi member, for an audition........ he doesn't pull his punches and calls a spade a spade......... He is the ideal person to present a "second opinion" review.

All will be revealed
post #29 of 682
that last set of pictures with the headphones for comparison really allowed me personaly to get sense of the scale,the size of the amp.

i had the impression it was larger for some reason.

nice work mike ,very pretty amp very nice construction

BUT

When do we get a shootout between all of your "in house" amps so we can all know who/what the winner is !


cheers amn

rickmeister
post #30 of 682
Thread Starter 
Quote:
Originally Posted by rickcr42
that last set of pictures with the headphones for comparison really allowed me personaly to get sense of the scale,the size of the amp.

i had the impression it was larger for some reason.

nice work mike ,very pretty amp very nice construction

BUT

When do we get a shootout between all of your "in house" amps so we can all know who/what the winner is !


cheers amn

rickmeister
Hi Rickster,

Yes it's pretty "compact" ,due to me shoehorning it into a Hammond 1455K1202, I was warned that things would be tight and I should have taken heed of the warnings In true Pink fashion I went ahead with my choice of enclosure and managed to shoehorn the components into the 1455K1202 case :-)


It's possible to house it in a 1455K1202 if you work to zero tolerance and have "pot luck" on your side (some would call it skill ) but the next WNA I build will be in a larger case!

The shootout will take place 500 hours from now (499 hours and 7 minutes to be precise ) I think it will be a foregone conclusion, however, unless the Chiarra, solo etc shape up in the meantime. This really is the best I have heard to date.

Dr. White sure has worked wonders with that LM6171

Pinkie.
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