[PinkFloyd]

Quote:

Originally Posted by damitamit However, they do tend to look quite nice after 5 coats (sanding in between) of black car spray paint, which is what the guy I sold my ra-1 clone to did. Thou he's a real perfectionist so i doubt i could get it looking like that. Ill try get him to post some pics of it.

heh,

The Chiarra / Andante kit came with the same unpainted aluminium Maplins enclosures (the larger ones)

I ended up spray painting the lid a battleship grey colour and the rest of it black.. looked ok but far from an aesthetic work of art, let's just say they looked "unassuming"

 

[PinkFloyd]

Quote:

Originally Posted by Madcat05 I'm not really fond of the silver end enclosures, but Pinkie I see you've used a black end Hammond. Could you link me to it on Hammond's site?

Hi,

The part number is 1455N1602BK I get mine here

 

[Madcat05]

Thanks PinkFloyd.

I can get that one for more than half the cost of the one David sells.

 

[Alick]

Quote:

I'll select a few 9.5M ones and send them over to you Alick.

Quote:

I'll send the AD-811 over to you after Christmas Alick for a second opinion

Quote:

got a few 10M resistors. A couple are on their way to you as we speak Alick.

You guys are going to give my postie a hernia. OK, maybe not, but you know what I mean.

What can I say, but thanks!

 

[PinkFloyd]

I've just realised this thread is 6 months old and what a great six month's it's been!

When I first took delivery of the board from Dr. White I didn't know what to make of it as it was unchartered territory and was purely a £30 "suck it and see" punt.

I'm so glad I parted with that £30

I'd just like to thank Dr. White for all his work on making the amp what it is today, he really is a valuable asset to the Hi-Fi community and is a true gentleman who is passionate in his work and strives to provide the best possible sound for the pound. he's been an absolute gem of a guy to communicate with and I have learn't a lot from him over the past few months as well as benefiting from the aural magic the WNA delivers.

I'd also like to thank the contributors to this thread for their ideas and inspiration, this is one of the most friendly and informative threads I have ever been involved in and I thank you all for your input.

The past six months have seen quite a few developments let's hope next year sees a lot more ........ I'd like to see provision on the board for the ALPS blue velvet pot, an on / off switch and headphone socket....... a minor gripe but it would negate the need for hook up wire and would make the kit easier to build

All the best for Christmas. (enjoy the 10M and AD-811) may your New Year be output cap free

Mike.

 

[Alick]

...and so say all of us. I couldn't have put it better, so...what Mike said. Merry Christmas!

 

[PinkFloyd]

What a great way to spend Christmas Eve.... armed with a multimeter, a few bottles of Hobgoblin Ale and a reel of 100 x 10M chip resistors.

I managed to find "4" that measured 10M exactly, the other 96 were over the 10M mark and not one was under

I fitted them onto the LM6171 (piece of cake and a perfect fit) rolled them into the WNA (minus output caps) and measured the DC offset:

Left channel: -46.7mV
Right Channel: -41.3mV

Quite a difference from David's -8.5mV readings I think 9M will be needed to get the offset down that low and, even then, -8.5mV is not as good as the "zero" reading you get with output caps fitted.

50mV or thereabout is not going to damage your headphones (300R Sennheisers) so I had a darned good listen without the output caps and to be totally honest, if there is an improvement I can't hear it... I wasn't expecting miracles but assumed there may be a subtle difference without the output caps but nope, not as far as my ears go... maybe a bat could detect something but I can't.

The AD-811 offset measured pretty weird:

Left channel: -0.9mV
Right channel: -17.3mV

Must be a fluctuation in the chips.. not very precise.

The real surprise with offset was the humble Opa 134:

Left Channel: -0.2mV
Right Channel: -0.3mV

I measured offset with 3 independent meters and they all measured within a whisker of each other so these measurements are deemed pretty accurate. Maybe with 2 LM6171's from a different batch the offset would have been lower, who knows, one things for certain though......... I'm sticking with output caps with the LM6171....... there's no audible advantages removing them (not to my ears anyway) and there's one big advantage to using them..... ZERO DC offset.. Nil, none, nada, 0%

Oh well, it was worth a go and Rapid sure are Rapid! I ordered the chip resistors yesterday at 7pm along with some solder and the package arrived today at 11am!! Now that "is" Rapid especially considering the time of year.

Now what the heck can I make with 98 10meg chip resistors?

 

[Jan Meier]

"Quite a difference from David's -8.5mV readings I think 9M will be needed to get the offset down that low"

No, you need a higher value than 10 MOhm!!!!

Jan

 

[PinkFloyd]

Quote:

Originally Posted by Jan Meier "Quite a difference from David's -8.5mV readings I think 9M will be needed to get the offset down that low" No, you need a higher value than 10 MOhm!!!! Jan

Yes,

It's looking that way Jan..... though I think the output caps are the best solution in a kit amp considering the different voltages that may be used... 24 - 36V. There will also be variations from one LM6171 to another so a low offset cannot be guaranteed simply by fitting resistors to the -ve power supply rail ( LM6171 pin 4 ) and the + or non inverting input to the LM6171.

The "bullet proof" solution is to fit output caps which ensures Zero offset irrespective of voltage and this is why Dr. White recommends them in his kit amps, they cover all eventualities with the LM6171 and won't pose any issues with any voltage from 24 - 36V.

I'll pop out and hook two of the chip resistors together and check the offset with 20M across 3&4.

****, so much for enjoying Christmas Eve basting a turkey

All the best and have a peaceful Holiday Jan.

Mike.

EDIT: oops!....... Drunk in charge of a Multimeter (scuse me your honour it is Christmas Eve) I'm off to baste my bird have a great holiday people!

 

[PinkFloyd]

EDIT!!! too much HobGoblin incorrect reading of the meter!!! OOOPS!!


Come on guys it "is" Christmas Eve!

 

[Alick]

Quote:

EDIT!!! too much HobGoblin incorrect reading of the meter!!! OOOPS!!

So what was incorrect? '+' instead of '?' Out by a factor of 10? uV insted of mV?

'fess up, Mike...

 

[PinkFloyd]

Quote:

Originally Posted by Alick So what was incorrect? '+' instead of '?' Out by a factor of 10? uV insted of mV? 'fess up, Mike...

OK.

I've really been testing the LM6171 without output caps extensively over the past couple of days whilst the rest of you have probably been stuffing yourself with turkey

I tried 6 x LM6171's and no two gave measurements that suggested simply whacking a resistor between 3 & 4 is the ideal solution.

With 10M all of the results were "-mV" and here are the results:

Chip 1: -48.1mV
Chip 2: -41.3mV
Chip 3: -23.5mV
Chip 4: -13.7mV
Chip 5: -37.2mV
Chip 6: -25.8mV

With 15M all of the results were "+mV" and here are the results:

Chip 1: +15.9mV
Chip 2: +24.7mV
Chip 3: +34.9mV
Chip 4: +49.0mV
Chip 5: +27.8mV
Chip 6: +31.2mV

I made up quite a few 15M resistors using 3 x 10M resistors suitably configured (series / parallel) to make 15M:

Pretty small chips to work with but easy when you get the hang of it.

I then tested each one and selected 6 which where pretty spot on to 15M and then encased these 6 "modules" in hot glue to ensure there was no way of them coming apart:

I attached these "modules" to the 6 x LM6171's and identified them by heatshrinking different colours onto their wires.

I used the left channel of the WNA to perform the tests and then the right channel...... both channels measured pretty identical using the same LM6171 in each channel.

My conclusions are that neither 10M or 15M can be considered "ideal" as all of the chips have to be individually "tuned" to give very low offset.. simply sticking a 15M between 3&4 is far from satisfactory.

If you are going to remove the output caps I strongly suggest you have a few different resistors to hand as you'll have to "make" the correct ohmage resistor to suit each individual LM6171..... it could be anywhere from 10M to 16M dependant on the individual LM6171 you have... from the above results 12M - 13M may be a good starting point but be prepared to spend a very long time finding the value that will give you zero offset.

I listened to a WNA with the two lowest offset measured LM6171's fitted (-13.7mV & 25.8mV) against a WNA with output caps fitted:

I won't waste time typing here as I could hear "no" difference between the two.... NO difference at all.

So, is it worth removing the output caps? IMO no it isn't. With the output caps in place there is ZERO offset and, as such, the full dynamic range will not be affected (any dc offset will pull or push the diaphragm away from its resting point which will reduce it's travel in one direction whilst uselessly increasing it in the other direction) You also risk blowing the crap out of your headphones if one of those resistors falls off

Nope, I can fully understand why Dr. White has chosen to use output caps.... zero dc offset, guaranteed protection for your headphones and all this with minimum (if any) insertion loss.....

Just my two cents but output caps it is for me considering the variations between LM6171's.... if a set value resistor gave an exact offset reading with "every" LM6171 then fine but due to the wide fluctuations output caps are the bullet proof solution.

Merry Christmas!

 

[PinkFloyd]

Another little thing I tried today was to interchange parts from a black Hammond to an aluminium one and vice versa...... I think they look much better than plain black or plain aluminium what do you think?

 

[Alick]

I'll probably still have a go, but it sounds like the output cap's aren't such a compromise after all. I suppose it was wishful thinking that a major improvement could be made so simply to an amp which already sounds so good...

EDIT: I quite like the "black and silver" look. I could do with getting another case anyway as I slightly bashed one corner of my front panel when I fitted the ALCAPs in a wee bit of a hurry and didn't take as much care as I should have.

 

[GoRedwings19]

Hi dudes I am not a diy'er as I have no clue when it comes to things like this. But I am awaiting delivery of my WNA and I am really excited. Reading the thread has only heightened me excitement even more. I will post impressions initially and then compare notes with you WNA'ers.