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Modulus-86  build thread
Modulus-86  build thread
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Old 14th June 2019, 09:23 PM   #4671
futurama82 is offline futurama82
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Quote:
Originally Posted by tomchr View Post
Great choice!



That should work, assuming you can make everything fit. The heat sink should be adequate for music reproduction with 28-30 V rails.



Do beware that the SMPS-86 provides 24 V at 2.5 A, so if you are using low-impedance loads and like to crank the music loudly, you may run out of power. For 8 Ω loads, it'll be fine in 99% of cases.



Yep. Go to the section for the power amp. Note the rail voltage (46 V). The absolute maximum for the Modulus-86 is 42 V. I recommend staying below 36 V - especially with smaller heat sinks. So you'll have to either find a way to lower the supply voltage (maybe you can use a different primary tap (say choose the 240 V tap instead of the 220 V one) or use a different power supply.

Tom
thanks for the reply, after digesting your responses I've done some probing and come up with the following findings.
*I should add at this point that mine is the UK model (B on the schematic)*
The power supply produces 42v DC or 50v DC depending up on the impedance switch setting. As I understand it the impedance switch simply selects which secondary winding is being sent to the supply board.
(is this what you were referring to by using a different tap?)

In terms of the existing mains transformer it outputs both 30v AC and 36v AC.

So with the above in mind I have the following 2 questions before i decide what to buy:
1: is the 42v DC too far to the limit to power 2x modulus 86?
2: If i opt to get a power 86 instead of using the existing supply, will the existing transformer be compatible?

Thanks

Tom
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Old 15th June 2019, 07:02 AM   #4672
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by futurama82 View Post
The power supply produces 42v DC or 50v DC depending up on the impedance switch setting.
42 V is the absolute maximum the LM3886 can handle with signal applied. If mains variation causes the supply voltage to go beyond 42 V, you severely compromise the reliability of the chip. This may mean that it'll last eight years instead of ten, that you have to replace the chip every month, or that it goes *poof* in a cloud of smoke.

The other thing to be aware of is that a higher supply voltage leads to higher power dissipation in the LM3886, which will cause the SPiKe protection in the LM3886 to engage earlier. This compromises performance. That's why I recommend 28-30 V max. for 4 Ω load and 35-36 for 8 Ω load.

Quote:
Originally Posted by futurama82 View Post
As I understand it the impedance switch simply selects which secondary winding is being sent to the supply board.
(is this what you were referring to by using a different tap?)
Yep. The switch selects different secondary taps. There's only one primary, so my idea of using a different primary tap to get a lower output voltage will not work.

Quote:
Originally Posted by futurama82 View Post
1: is the 42v DC too far to the limit to power 2x modulus 86?
Yes. I would do something to lower the output voltage of the supply.

Quote:
Originally Posted by futurama82 View Post
2: If i opt to get a power 86 instead of using the existing supply, will the existing transformer be compatible?
Yes. The transformer in your amp has a secondary with centre tap. Connect the centre tap (black wire) to either terminal 2 or 3 on the input of the Power-86 and the blue wires to terminals 1 and 4, respectively. Cut the ends of the red wires and cover with heat shrink.

You could look at using a bucking transformer. See below (from Rod Elliott's page).
Click the image to open in full size.

You need to reduce the output voltage by about 10-15% at least, so you'll need a bucking transformer that produces 10-15% of your mains voltage (so 24-36 VAC if you're in the UK). Good news is that it only needs to supply the primary current, so you can likely get away with a 50 VA type, which you might be able to shoehorn into the chassis.

The best option is to get a transformer that's better suited for the application, though. You'll want 2x22 VAC at about 160-200 VA for the Modulus-86. Hammond 1182N22 would be an option. Mouser carries Hammond transformers.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
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Old 15th June 2019, 01:25 PM   #4673
futurama82 is offline futurama82
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Quote:
Originally Posted by tomchr View Post
The best option is to get a transformer that's better suited for the application, though. You'll want 2x22 VAC at about 160-200 VA for the Modulus-86. Hammond 1182N22 would be an option. Mouser carries Hammond transformers.

Tom
Hey tom, thanks so much for all of the advice.
I've weighed up my options and decided that shoe-horning the existing electronics isn't worth the extra hassle, especially when it wont yield optimal power for my pair of M86's.
This morning I cleared out the chassis (I'll include pictures as my build progressed), it all ready feels like the right way to go ans now I have a lot more flexibility for mounting a new transformer & PSU when building my amp. (The existing PSU was on the same board as the power amp and hence connected to the hat sink) This would have created so many limiting factors when mounting the new amp boards.

So this weekend I'll be ordering my pair of boards and Power 86 board from your site, and I'll pick up the transformer you recommended.

Thanks

Tom
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Old 15th June 2019, 05:26 PM   #4674
tomchr is offline tomchr  Canada
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I agree with your assessment that gutting everything and fitting all new electronics in the chassis is the way to go. Should you find reusing the chassis to be more trouble than it's worth, the 2U ModuShop Dissipante (available directly from Modushop or via the DIY Audio Store) is a good way to go.

I'll fill your order as soon as I get home from vacation. Expect it to ship by the 28/29th of June (assuming you place it before then... )

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 15th June 2019, 06:50 PM   #4675
futurama82 is offline futurama82
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Originally Posted by tomchr View Post
I agree with your assessment that gutting everything and fitting all new electronics in the chassis is the way to go. Should you find reusing the chassis to be more trouble than it's worth, the 2U ModuShop Dissipante (available directly from Modushop or via the DIY Audio Store) is a good way to go.

I'll fill your order as soon as I get home from vacation. Expect it to ship by the 28/29th of June (assuming you place it before then... )

Tom
Cool, thank you for all the advice, and your continued support of this community.
Now, stop replying and enjoy your vacation.
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Old 15th June 2019, 10:20 PM   #4676
Omer Yair is offline Omer Yair  Israel
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This is the first amp out of two 4-channels Mod-86 amps build. They will feed a 4-way system I'm designing. Currently it feeds a sort of 2-way speakers hand built by a sound engineer in Israel (Ariel Ran Liberman).

Initial impression is simply WOW! A couple of drivers on my current speakers were torn and I thought it impaired the whole system. With Tom's Mod-86 the speakers came back to life again. Every note and instrument stands for itself and there is no muffling at all. I never thought those speakers could sound so well.

The build was fairly easy. Tom's instructions are very well written and easy to follow. For any question Tom responds quickly via email. Couldn't ask for better support! Thanks Tom! This is my first project build (excluding O1 amp and blinking LED) and most of the struggle was with the case. I also made a some mistakes with the Mouser order that will be fixed in another time (ordered a toggle switch instead of momentary and a few others glitches).

Since it will be used for a stereo 4-way build, in the future I'll add a connection between the ISS boards to make them turn on (and maybe off too) together.

The case is Dissipante 2U from Modushop. Attached are some photos for you peepers who prefer to look at amps than listen to them
Attached Images
File Type: jpg IMG_20190615_153810_HDR.jpg (977.9 KB, 259 views)
File Type: jpg IMG_20190615_204450.jpg (342.0 KB, 258 views)
File Type: jpg IMG_20190615_204514.jpg (370.5 KB, 248 views)
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Old 16th June 2019, 09:12 PM   #4677
asuslover is offline asuslover  Romania
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Modulus-86  build thread
Very nice ! Looks great! If you are planning to use this with a 4 way speaker then you should consider a different amp for the woofer. Your power supply is feeding 4 amps, Tom has a different ps with 4 caps , I would use one of those .
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Old 17th June 2019, 08:40 AM   #4678
tomchr is offline tomchr  Canada
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Nice build! Thanks for sharing.

Quote:
Originally Posted by asuslover View Post
If you are planning to use this with a 4 way speaker then you should consider a different amp for the woofer.
That depends entirely on the impedance and efficiency of the woofer.

Quote:
Originally Posted by asuslover View Post
Your power supply is feeding 4 amps, Tom has a different ps with 4 caps , I would use one of those .
On the other hand, in a multi-way system, each amp handles a slice of the total frequency range, thus, only a slice of the total output power. That eases the demands on the power supply a bit. That said, I'm just as happy to sell a Power-686 instead of the Power-86.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 17th June 2019, 02:06 PM   #4679
craigtone is offline craigtone  United States
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Here is my Modulus build. I am using a Mini-Dissipante chassis. The boards and instructions were great and it fired up and sounded great the first time! Kudos to Tom for the hard work!

I searched this thread about single-ended wiring and left the shield on the Modulus board floating. Every now and then I would get noise through the amp and moving the cables around resolved it. For kicks I put an alligator jumper from the shield pin on the Modulus board to the RCA shield and it then behaved! If you build this single-ended, HOOK UP THE SHIELD WIRE!

My other issue is that I built this for my Snell E-II's. These are my non-critical listening rock speakers. Sometimes I really like to crank it up and make the walls vibrate and I found the SMPS is NOT suited for that level of volume! It would start cycling on me as it hit the current limit.

Next step is to order the linear PS PCB from Tom and build this with a convential power supply. Live and learn! If anyone is interested in a fully-built and functional SMSP-86, drop me a line!
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Last edited by craigtone; 17th June 2019 at 02:09 PM.
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Old 17th June 2019, 10:27 PM   #4680
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by craigtone View Post
If you build this single-ended, HOOK UP THE SHIELD WIRE!
I cover that on Page 11 of the design doc.

Quote:
Originally Posted by craigtone View Post
My other issue is that I built this for my Snell E-II's. These are my non-critical listening rock speakers. Sometimes I really like to crank it up and make the walls vibrate and I found the SMPS is NOT suited for that level of volume!
Yeah... The SMPS-86 is a good candidate for a desktop amp or an amp powering efficient 8 Ω speakers. If you're looking to rock your house off the foundation, you'll find the Power-86 or Power-686 to work better for you.

Tom
__________________
Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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