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M³ amplifier build discussions thread - Page 11  

post #151 of 828
3/17/05 at 6:11am
Thread Starter 
Anyone else got a working M³ yet (other than myself, jamont, thrice, MisterX, phobus, steinchen and Magsy)? I'd like to see some pics and hear about your impressions.
post #152 of 828
3/17/05 at 9:56am

I'm covering my job and also the job of a co-worker who moved on, so I am not getting squat done that is not directly tied to the day job. {*snif*}
post #153 of 828
3/17/05 at 12:39pm
Quote:
Anyone else got a working M³ yet ?
Well, I'm still struggling... someone alert the media.

Got the trimpots adjusted (per your setup instructions), but no sound (through some cheapie functional headphones). All the readings are dead on, and tweaked after warming up. Nothing was alarming, or unexpected.

How can I tell if I'm getting output with the meter?

If it will help, I can post pics tonight. Perhaps I have some other bone headed wiring issue.

Otherwise, I'm 85% through the second board (without the resistor value faux pas), so maybe tonight.
post #154 of 828
3/17/05 at 12:46pm
Quote:
Originally Posted by pabbi1
Well, I'm still struggling... someone alert the media.

Got the trimpots adjusted (per your setup instructions), but no sound (through some cheapie functional headphones). All the readings are dead on, and tweaked after warming up. Nothing was alarming, or unexpected.

How can I tell if I'm getting output with the meter?

If it will help, I can post pics tonight. Perhaps I have some other bone headed wiring issue.

Otherwise, I'm 85% through the second board (without the resistor value faux pas), so maybe tonight.
Try out some of the suggestions in this article:

http://www.tangentsoft.net/audio/trouble.html
post #155 of 828
3/17/05 at 1:32pm
After buying crap caps yesterday my Cerafines arrived today!
So in true headfi fashion I made the most of my lunch hour and got them on.

Sooo sexy....





All it needs now is a once over with some Isoprop and putting into a case. The heatsinks are warmer than I thought, I wouldn't fancy no vents with this setup.

I'm really impressed by the bass boost, it seems to work nothing like bass boost you get on the average hifi. It's much more subtle and seems to be effective over a tighter range - more focused, all in all really useful.

Will be back with real impressions once its burned in/I'm used to it
post #156 of 828
3/17/05 at 5:06pm
Thread Starter 
Quote:
Originally Posted by pabbi1
Got the trimpots adjusted (per your setup instructions), but no sound (through some cheapie functional headphones). All the readings are dead on, and tweaked after warming up. Nothing was alarming, or unexpected.
Can you list what you measured at each channel's output for DC offset? What voltage drops were measured across the R5 and R9 resistors? Also, try measuring the voltage across the collector and emitter pins of Q2 for each channel. What do you get? Do the MOSFETs get warm? What is your PSU voltage and what do you measure across pins 7 and 4 on the opamps, as well as from pin 7 and 4 to IG?

Quote:
How can I tell if I'm getting output with the meter?
I assume you do not have the board mounted in a case yet, and the volume control pot body is not connected to ground. If all your measurements are ok (especially DC offset), then plug in a pair of headphones without any input connected. You'll hear hum as you touch the volume pot shaft (use no knob for this, or a metal knob) when the pot is turned part-way up. This will be a clue that the amp is outputting a signal that is "induced" from the input (your body). If you hear nothing, then there is probably something wrong with the wiring to your headphone jack.

At any rate, some close-up pics of the board (top and bottom) and wiring to the jacks might be helpful for us to diagnose your problem.
post #157 of 828
3/18/05 at 12:51am

Well...

Here are my measurements (L-R-G):

STEPS: 32.0v

Across R5: 0.503v - 0.503v - 0.504v
Across R9: 80.1:79.2mv - 79.8:79.9mv - 80.0:79.0mv
Pins4&7: 29.4v - 29.4v = 29.4v
Pin 4 to IG: 14.7 - 14.7- 14.7
Pin 7 to IG: 14.7 - 14.7- 14.7
IG to O: (-.5mv) - (-.3mv) - .1mv
Q2 7.26v - 7.25v - 7.28v

BTW, it sounds great.

Sorry for the drama... but, I swear all I did was solder the ground from the two Alps screws to IG. Beats me... but, bottom line success. And, this was the (self inflicted) messed up board.






Not sure the steel metal divider (from the bottom of an old Carver CDP) is necessary, but what the heck.

Already (most way through the first SACD), I have had a dozen 'never heard that before' moments. And, that's with Alice in Chains... I immediately notice significantly more presence, air and detail... which is probably just the OPA637 (627 in Ground) vs the OPA2132.

Is there an alleged 'burn in' time?

I'll withhold detail listening results until the weekend, or 40 hours of listening time, whichever comes first....

And, we owe you, Ti, and in equal measure, Morsel, for bringing this to fruition. Awesome job.
post #158 of 828
3/18/05 at 1:04am
Thread Starter 
Pabbi1, I am glad that everything worked out ok. Your voltage measurements are indeed spot-on. Congratulations! The Sun computer chassis is definitely an interesting application.

Allow the amp to burn-in for some time (maybe leave it on continuously for a few days). It does seem to improve the sound. Since you have a spacious enclosure you might try tweaking up the MOSFET quiescent current a bit, try 100mA - 120mA and see if you hear any difference.
post #159 of 828
3/18/05 at 1:38am
Nice Sparc-M³!! I see theres room for maybe a silent cooling fan in the back ?
post #160 of 828
3/18/05 at 1:46am
Quote:
Originally Posted by phobus
Nice Sparc-M³!! I see theres room for maybe a silent cooling fan in the back ?
Been there, done that and then disabled the fan.
It was to noisy.

Well that and there was no need for it either.





Nice work pabbi1!
post #161 of 828
3/18/05 at 2:47am
I have one of those old sun cases lying around, never really thought of using it as a case though. I assume that you painted it black instead of keeping it that ugly grey. Lots of extra room though in that case. I say go for like 4" heatsinks and crank up the bias to the extreeeme.
post #162 of 828
3/18/05 at 2:59am

Thermal Compound

If you are using the TO-220 mounting kits to mount the MOSFETs to the heat sink, is it advised to use thermal compound also? Or is the small electrical isolator pad an efficient thermal conductor by itself?
post #163 of 828
3/18/05 at 3:13am
Thread Starter 
Quote:
Originally Posted by rjkdivin
If you are using the TO-220 mounting kits to mount the MOSFETs to the heat sink, is it advised to use thermal compound also? Or is the small electrical isolator pad an efficient thermal conductor by itself?
The insulator pads are good thermal conductors, but in order to work properly they must adhere completely to the surfaces of the TO-220 device and the heat sink.

Some of these insulator pads are slightly "soft" and will conform to the small imperfections of the TO-220 device and heat sink mounting surfaces, giving good heat conductivity. These do not require the use of thermal compound. Others (like the common mica-based insulators) do require the use of heat sink compound. The compound fills the micro-gaps between the layers, assuring maximum heat transfer.

It won't hurt to use some regardless of insulator type. Don't use too much, though. just a very thin film is enough.
post #164 of 828
3/18/05 at 3:49am
Congrats on your amp, pabbi1!

rjkdivin, I favor silicone TO-220 insulators because they don't need messy heat sink grease and don't crack like mica.
post #165 of 828
3/18/05 at 3:55am

Thermal Compound

Thanks AMB and Morsel....just what I needed to know, and conforms with what I was thinking. The isolators with the TO-220 kits are pretty soft and should conform nicely.

My first M3 is coming along well. I'm waiting on some caps from Mouser that were back ordered, but should be able to start mounting as soon as I figure out what case to use.
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