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Upgrade Fluke 510A AC voltage reference

Posted 16th July 2012 at 04:45 PM by 1audio

While doing some research on making an ultra low distortion analyzer I stopped to look at the Fluke 510A that has been siting on my shelf for years. Lots more on the 510a here: http://assets.fluke.com/manuals/510A_AD_imeng0000.pdf

In short a low distortion (.005% or better) 10V +/- .002% reference oscillator. There are very good numbers and by 1970 standards exceptional.

I was looking at it because I was researching AGC circuit for oscillators. This is an interesting implementation with its standards lab precision accuracy and stability. However its not simple and the critical parts are expensive (an ultra stable voltage reference, ultra stable resistors etc.)

In any case I was wondering if the distortion can be reduced still further. At the time it was built .002% was about as good as possible in practice and better would be hard to verify.

In short, after a number of experiments I got the distortion down to .0003% THD (30 KHz...
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Old

Audio heaven? No, not me, the other guy ...

Posted 12th July 2012 at 01:39 AM by fas42
Updated 16th July 2012 at 12:16 AM by fas42

This follows a suggestion from another member -- thanks, bear! -- to chronicle at least one journey in optimising sound. And, yes, it's not one of my efforts, because the way I do things is very messy: they look incredibly messy, full of false turnings and bits of "I wonder if this is actually doing anything positive now". Enough to get anyone watching closely thoroughly confused ...!!

The story is that a small music listening group kicked off, then faded away. But from that an ongoing exercise began, where a younger, very enthusiastic DIYer was happy to hear my feedback on what path to take with his system, and this has continued for a couple of years, with quite substantial, positive gains in sound quality, to this day.

So, to give a clearer picture of the angle I'm coming from I'll attempt, from memory, to list the steps taken, in fairly general terms, and what the various ups and downs in the process were ...

At the start, when I first...
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Old

miniDSP tools

Posted 9th July 2012 at 02:29 PM by DougL

If I ever have my DCX break and need another XO, these tools look like they make miniDSP a real choice.

the Active Crossover Designer web page
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Old

Musical monitor: Okay, what's this "musical" tag here mean, really??

Posted 8th July 2012 at 01:24 AM by fas42
Updated 16th July 2012 at 12:21 AM by fas42

I alluded to this in the first post on the thread, and it's worthwhile "defining" it a bit more.

Everybody would have a gut understanding as to what I mean, but what actually is it, and how do I measure it, to assess whether I've achieved it? There are the people who live and die by the conventional audio measurement yardsticks, and then there are the others who feel that these animals leave a lot to be desired. Again, look at the activity on the "Sound Quality Vs. Measurements" thread ...

Well, I'm pretty obviously in the latter camp, the standard numbers that an AP setup will pop up will mean very little, and since my project includes speakers the nightmare of getting meaningful distortion figures for the full path of the sound exists. So, I'll use the next best thing, my ears.

To make life easy here, I'll use a pretty accessible test object: the acoustic piano. We have one of those beasts in the listening area, my wife plays,...
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Old

Musical monitor: Some comments on the positive input in the original thread

Posted 7th July 2012 at 04:45 AM by fas42
Updated 16th July 2012 at 12:21 AM by fas42

By tnargs:

Quote:
I was assuming we were going to take something like a Behringer 2031A (2 way, 8", active, affordable) and see what tweaks are on the table.
Most perceptive ...

Quote:
Whenever I see a measured FR of a Behringer it looks nice and smooth and flat, off axis too, so it seems a decent start.
Exactly so.

Quote:
Although Lynno's post is true enough, I thought we would be keeping the drivers and looking at any gains from astute use of felt or resin (on or around the cone/dome), replacement of dust cap, stiffening or dampening the pressed steel driver frame... what else?
Possibly will improve the frame in some such fashion; and look at stronger coupling of the whole driver assembly to the carcase such that vibration is transferred in the most direct path to the surface the monitor is sitting on.

But these things will be only addressed after the electronics are sorted out, and I see how well the driver behaves itself at maximum SPLs.
...
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Old

B-board Boxer Project : A Low Voltage Headphone Amplifier for 16 ohm Loads

Posted 7th July 2012 at 12:19 AM by rjm
Updated 29th September 2012 at 02:58 AM by rjm

I always seem to end up optimizing my headphone amplifier circuits for higher impedance headphones, this mostly happens because I own a pair of 300 ohm HD-600s and it is tedious to design for both the voltage requirements of high impedance headphones and the current requirements of low impedance headphones.

Not impossible, just, for the class-A designs I seem to be building recently, increasingly large, heavy, and impractical.

Complimentary transistor circuits, however, offer the opportunity to swap voltage for current at something close to the same design cost. They are therefore a practical topology for efficient class-A power delivery into low impedance headphones. As a design experiment, my aim is to discover how far I can leverage an ultra-low-voltage, unity gain circuit for compactness without sacrificing sound quality.

Ok. Back-of-the-envelope calculations:

A typical 16 ohm in-ear-headphone has a sensitivity of 100-105...
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Old

Ceasar II 300B SE mono block upgrade Part #1

Posted 5th July 2012 at 06:36 PM by dvb projekt
Updated 24th July 2012 at 05:33 PM by dvb projekt (Titel changed)

A short quick upgrade for my Ceasar II Mono´s
to push the sq to the limit...


The last upgrade i made is to swap from the very good sounding Emission Labs 300B-XLS to

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the Sophia Electric Royal Princess 300B

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For me the best sounding 300B on the market!

The parts for further upgrading are:

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1st - The caps C2 & C3
2nd - The grid stoppers R5, R8 & R10


1st Upgrade




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The Mundorf silver/gold/oil are changed to the new Duelund Cast PIO-Cu.

Click the image to open in full size.Click the image to open in full size.
...
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Old

My wiring scheme for the O2 in a B3-080 Desktop case with RCA's and 1/4 inch jack

Posted 5th July 2012 at 04:23 AM by MrSlim
Updated 5th July 2012 at 04:26 AM by MrSlim (fixed typo)

When I was planning the wiring scheme for the Baby Desktop O2, originally, I thought I would use 3 and 4 pin board mounted posts with equivalent pin connectors so all the flying wires could be disconnected from the board. I realized that would be too much work(and probably even more prone to disconnection so I only made one of the connections removable (the 3 pin P1 jack for the RCA inputs, beside the input J2 connector).
(note to add part #s for the pins and connectors I used)

Make sure you grind off the anodized coating around the holes on the inside of the panel before you mount the RCAs to get a good ground connection.

I used individual pairs of wire from solid core Cat5 cable for all the connections, and in my wiring description, I'll be using the wire colours from the cable I used. (it helped since I built 16 of them.. )

For P1 (for RCA input) I used Brown/white for Right and Blue/white for Left. The square pad(close to the the...
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Old

ADAU1442 DSP - micro production line!

Posted 4th July 2012 at 02:36 AM by googlyone

I got to the point with my new audio DSP / crossover that I had no more excuse not to load the remaining PCB's I had manufactured.

I initially only loaded one of them, on the basis that if I had a clanger in the layout I could get a new spin of the boards.

Well the thing is all working and I have updated the DAC board - so the remaining five boards needed loading. I find a bit of PCB manufacture and loading to be quite therapuetic - as my previous blog entries will show.

This weekend I found my limit - loading the SMD's for these five boards - by hand in my toaster oven - took about three hours, then loading all the through hole parts, particularly headers and power supply parts blew away I would guess six more hours. I am over it!!!!

They do look pretty though!

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The only part remainig to be loaded on these boards is the ADAU1442 regulstor transistor. Thay will allow me to...
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Old

Musical monitor: And the story continues ...

Posted 4th July 2012 at 02:22 AM by fas42
Updated 16th July 2012 at 12:22 AM by fas42

The project will proceed, exactly as stated in the earlier posts. Just a shame people couldn't help injecting unhelpful comments, and I was provoked into responding. Ahhh, well ...

So, now some peace and quiet! Hopefully at least a few will find something of benefit in what I relate here, and my methods may resonate with some.

Anyway, may all enjoy good listening, no matter what!

Cheers,
Frank

Postscript: Hah! Dumb me, I didn't spot this earlier: http://www.diyaudio.com/forums/blogs...scientist.html. Some excellent thoughts and comments ...
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