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Modulus-86  build thread
Modulus-86  build thread
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Old 6th July 2019, 10:29 PM   #4711
tomchr is offline tomchr  Canada
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Originally Posted by sq225917 View Post
Tom, if you think you have it bad with ear lead swappers, you should read the dac threads. There's all sorts of unmeasured junk being thrown inside some of them as mods.
...most of which utterly wrecks the DAC performance. Yeah... Not my idea of a good time.

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I think it fair to tell you that I modded my bridged 86p monos today.
GOOD GAWD!!

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I added a light pipe from the led on my soft start board to the third pin hole on the front panel so I can now tell between unplugged, plugged in, and powered up from the the 3 front panel leds. A mod I'm sure you'll be able to get behind.
But did you use audiophile grade light pipes of pure grain-oriented glass drawn from a single glass crystal? Was the crucible heater supplied from a filtered power supply and connected by pure solid silver conductors?

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Cos frankly there's bugger all else to do with them but play music...
Yeah... I designed them that way. I'm glad you like them.

Tom
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Old 7th July 2019, 01:03 AM   #4712
Mark Johnson is offline Mark Johnson  United States
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Modulus-86  build thread
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Originally Posted by tomchr View Post
You need more than 10 nF to swamp out the diode parasitics, though.
The diodes that you posted in 686 #1072 (link) are about 0.2nF, your image copied below.

Click the image to open in full size.

And the four bridge devices are connected across the secondary (forming a resonant RLC circuit) in a series-parallel configuration of diodes where only two of the four diodes is biased at 0V (the high capacitance regime) when reverse recovery happens. The diodes in series with the high-C devices, are decidedly low-C since they are at about -28V reverse bias.

0.2nF also happens to be, approximately, the zero bias junction capacitance of the diodes in the GBJ four-in-one bridge rectifier package used in the lower current Power-86 PSU.

It seems to me that 10nF >> 0.2nF ... is this wrong?
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Old 7th July 2019, 02:35 AM   #4713
tomchr is offline tomchr  Canada
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No, 10 nF >> 0.2 nF. However, as you point out the diode capacitance is dependent on the reverse voltage. What's the capacitance at 0.1 V reverse bias? How about during reverse recovery?

Tom
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Old 7th July 2019, 08:14 PM   #4714
sq225917 is offline sq225917  United Kingdom
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Oh god, now you've got me thinking Tom. I should have used glass optic cable, not the 50p a metre plastic stuff. Bollocks....
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Old 8th July 2019, 10:54 PM   #4715
pelayostyle is offline pelayostyle  United States
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Just ordered a pair of Mod86 boards and waiting on parts to arrive. My music chain will consist of a Topping D70 to the Mod86. The D70 has an XLR output of 4.0v @ 0dBFS. Does this mean that the volume control will be limited in range? In other words, its going to get loud quickly with small increments.
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Old 8th July 2019, 11:25 PM   #4716
tomchr is offline tomchr  Canada
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That should work just fine. I use a MiniDSP SHD with 4 V output. I just use the volume control on the SHD. Works very well. I'm assuming the Topping will be similar.

Tom
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Old 17th July 2019, 03:31 PM   #4717
dwk123 is offline dwk123
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That should work just fine. I use a MiniDSP SHD with 4 V output. I just use the volume control on the SHD. Works very well. I'm assuming the Topping will be similar.

Tom
How do you like the SHD? I'm starting to get somewhat serious about revamping our main living room system, and the SHD seems like an almost ideal fit (maybe aside from price) - I think I can live with a 2-way setup with a passive xover on M/T and active to the woofers. I'm 'fairly sure' I could put together a Linux-based system that does much the same thing, but not without a fair bit of work (and when the wife can't watch TV because "my stuff" doesn't work, things aren't good)

Mod-86 content: I have what I think are an old pair of 2.1 boards I never got around to building, mostly because I stumbled across someone selling a completed Mod-86 here on the Swap Meet. My guess is that finding parts to build out a V2.1 set will be basically impossible, but I figured I'd get a more informed opinion before abandoning the idea.

I think a Mod-86 should be sufficient for the M/T section of the planned speakers based on my testing with my current unit, but I'd have to consider a 286 or 686 for future-proofing if I bought new assembled units. If I could build out my boards for 'cheap' though, that might allow me to defer that decision and/or put more $$$ into the rest of the system
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Old 18th July 2019, 02:18 AM   #4718
tomchr is offline tomchr  Canada
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Originally Posted by dwk123 View Post
How do you like the SHD?
I like it. Then again, I designed the analog sections in the SHD for MiniDSP, so maybe I'm biased. The analog sections were designed to get the full performance out of the DACs and ADCs.

I had the MiniDSP 4x10HD before (and still do). Its noise floor is a bit high, so with it as a preamp, I can hear a hiss when I put my ear against the speaker. With the SHD that hiss is gone.

It seems the SHD uses a more powerful DSP than the 4x10, so you have more biquads available for filters. That's nice as the LXmini XO pushed the 4x10 to about the max.
I'm now rocking a pair of KEF R700, so the SHD just acts like a DAC. I rather like it. I have not tried the Dirac room correction, though I hear good things about it.

All that said, I still haven't had time to put the SHD on the bench and measure it. One of these days...

If I was to nitpick (and of course I am ), I'd say that MiniDSP went cheap on the remote. I mean... It does the job just fine, but it is rather lacklustre from a human factors point-of-view. The function you use the most (volume control) receives the least real estate and the buttons are arranged left/right (volume down/up) rather than up/down. That said, the remote does the job.

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I could put together a Linux-based system that does much the same thing, but not without a fair bit of work (and when the wife can't watch TV because "my stuff" doesn't work, things aren't good)
Linux.... Sssss... Yeah... I won't stoke that fire. I've run Reaper and ReaEQ on the 2010 MacBook Pro that's my music machine. That worked very well.

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Mod-86 content: I have what I think are an old pair of 2.1 boards I never got around to building, mostly because I stumbled across someone selling a completed Mod-86 here on the Swap Meet. My guess is that finding parts to build out a V2.1 set will be basically impossible, but I figured I'd get a more informed opinion before abandoning the idea.
Oy... 2.1. Yeah. You're doomed. Actually... If you could find a pair of LME49710HA (TO-99 can package), the rest of the BOM is still obtainable. Some of the ceramic caps went obsolete because TDK decided to change the recipe. So you replace FK with FA or FG in the part number and off you go.
The real question is whether you can find a genuine LME49710HA for less than it would cost you to replace the boards with the current revision. It may be possible. Just make sure you get a genuine part. The Modulus-86 relies on the characteristics of the LME49710 to work.

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Originally Posted by dwk123 View Post
I think a Mod-86 should be sufficient for the M/T section of the planned speakers based on my testing with my current unit, but I'd have to consider a 286 or 686 for future-proofing if I bought new assembled units.
For multiway systems optimized for power, I generally recommend running a Ī35-36 V power supply. That gives the maximum output power, but you have to select the amplifier modules according to the drivers:
8 Ω drivers can be powered by a Modulus-86 or -186.
4 Ω drivers can be powered by a Modulus-286 (or -686 if you need more power).

If that blows your budget, I recommend running a Ī28-30 V supply and using Modulus-86 or -186 everywhere.

Tom
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Old 18th July 2019, 03:04 AM   #4719
poseidonsvoice is offline poseidonsvoice  United States
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Modulus-86  build thread
dwk123,

I have a pair of Parallel 86 boards fully built (sans LM4780 which I have here as well), with all genuine parts, etc...and tested. They are ready to be attached to some heatsinks. Give me a holler if interested. I just ordered too many boards from Tom! Let me see, ... Iíve built 16 channels of amplification from Tomís designs...you can say I am a believer...but I am not the only one

Best,
Anand.
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Old 18th July 2019, 04:12 AM   #4720
pelayostyle is offline pelayostyle  United States
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That should work just fine...
Thanks Tom! Sorry, hopefully this is my last question. I have an SMPS300R +-30v laying around that I'd like to use. Will this be enough for a stereo build or should I get another SPMS300 for a dual mono build? I'll be powering a set of 6 ohm and 4 ohm speakers with this amp. Thanks again.
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