Go Back   Home > Forums > > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Vendor's Bazaar Commercial Vendors large & small hawking their wares

Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old Yesterday, 09:04 PM   #831
chrisb is offline chrisb
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
At the very least would be the not inconsiderable additional cost of two chassis and connecting cables. Personally I like as few boxes and interconnects as possible and actually don’t mind the height of a 3U, which could make some of the shoehorn/ dental surgery tight work a bit easier.
__________________
you know I cant quit you, baby

Last edited by chrisb; Yesterday at 09:09 PM.
  Reply With Quote
Old Yesterday, 09:17 PM   #832
zgtc is online now zgtc  Europe
diyAudio Member
 
zgtc's Avatar
 
Join Date: Nov 2016
Location: Barcelona
Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
Quote:
Originally Posted by MrKettle View Post
Out of interest, do you have a view on whether having the power supply elements (e.g. soft start, transformer(s) and rectifier board(s)) in a separate enclosure is angood or bad thing?
He answered this months ago referring to external PSU in a Mod86, I assume Mod686 will be the same:

Quote:
Originally Posted by tomchr View Post
Yes. There are many downsides to housing the supply separately. You maximize the supply impedance that way, which is never a good idea. Also, the currents drawn by a Class AB output stage are not pretty. Each amp half draws a pulse each half of the signal cycle, so the currents are relatively high bandwidth --> good sources of EMI.

Separating the supply from the rest is sometimes done on phono amps where hum is the main concern. Even on those amps, you still have the drawback of the increased supply impedance, but at least the currents drawn by such an amp are usually pretty nice as the amp runs (mostly) in Class A and doesn't draw that much current. In phono and preamps, you could also implement local supply regulation in the amp enclosure to minimize the supply impedance.
Then again, in my DIFF PRE 8x2, I used a pair of switching power bricks for the supply and the worst case mains hum I measure on the output is -115 dBV (1.8 V). In the HP-1 I added regulators to the switching supplies and pushed the mains hum down below -136 dBV (160 nV).
Something tells me that doubling the chassis cost by having to build two enclosures isn't necessary for good performance. One just have to pay attention to the circuit layout.

Tom
  Reply With Quote
Old Yesterday, 11:03 PM   #833
tomchr is offline tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
Yeah. I'm not a fan of the separate supply and umbilical cord, especially in the case of power amps. It's an EMI nightmare waiting to happen for reasons I've outlined in the quote above.

Also, many who build the amp and supply into separate enclosures choose identical enclosures and stack the amp on top of the supply. That is rather likely to make any mains hum worse, so in addition to the EMI issues and supply inductance issues, you're now also creating a hum issue.

Tom
__________________
Modulus-86, 186, 286, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
  Reply With Quote
Old Yesterday, 11:07 PM   #834
tomchr is offline tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
Quote:
Originally Posted by chrisb View Post
At the very least would be the not inconsiderable additional cost of two chassis and connecting cables. Personally I like as few boxes and interconnects as possible and actually don’t mind the height of a 3U, which could make some of the shoehorn/ dental surgery tight work a bit easier.
It's not so much of a height issue, actually. The transformer is the tall pole in the tent and will fit within the 80 mm of a 2U chassis with 10 mm to spare. The issue is the width of the Mini Dissipante. The 250 mm internal width is pretty tight.

The Dissipante (not Mini) increases this to 350 mm if I recall correctly. That's plenty of room. 2U would work under the constraints I mentioned a few posts back. Otherwise, I'd use 3U for 4 Ω operation on 27 V rails and 4U for 36 V rails. The 430 x 300 mm footprint of the Dissipante is a pretty common HiFi component footprint size.

Also: Don't forget that you need to allow room for the wires to exit the board. The MegaFit connectors require a good 40-50 mm of bending radius on the leads. One trick is to build your modules with the vertical connectors (file off the locating tab and triple-check that you have the orientation right).

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

Last edited by tomchr; Yesterday at 11:10 PM.
  Reply With Quote
Old Yesterday, 11:21 PM   #835
chrisb is offline chrisb
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
Re 3U height, I was probably thinking of builds like the 686 with a pair of the Meanwell SMPS stacked vertically, or Guardians directly mounted on the rear panel for those folks still wanting to use binding posts rather than Speakons. But of course, it’s all postulation on my part until I actually build something.
__________________
you know I cant quit you, baby

Last edited by chrisb; Yesterday at 11:30 PM.
  Reply With Quote
Old Yesterday, 11:51 PM   #836
wcwc is offline wcwc  United States
diyAudio Member
 
Join Date: Oct 2011
The mod686 on one heat sink, the transformer in the opposite front corner close to the opposite side heat sink, the Mod86/Mod186 on the opposite heat sink towards the middle/back, and the Power686 and ISS stacked in the center. All the boards fit in 2d cadd representations, but it doesn't include wire clearances or heights of the boards.


I have the 2U 4xMod 86 minid chasis I could use for layout purposes.
  Reply With Quote
Old Yesterday, 11:51 PM   #837
tomchr is offline tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
I considered stacking the Mean Well SMPSes as well. The cage-free version (RPS-400-27) seemingly lends itself to stacking. Unfortunately, one of the standoffs will interfere with the control connector (located on a vertically mounted sub-assembly PCB). You can kinda/sorta make it work, but I really don't like the amount of torque it puts on the sub-assembly. I also wonder how that affects airflow for the lower PCB.

That's one of the reason I spent a few bucks more (literally!) to get the caged version (RPS-400-27-C) and mounted them vertically side-by-side in the 3U Mini Dissipante.

Anyone interested in building a copy of my MOD686 amp can request that exact chassis from ModuShop. The chassis will set you back about $350/each due to the amount of modification I do. I have ModuShop modify all panels except the top panel. It's a bit pricey but man it is so nice to have a chassis that just requires the turning of a screwdriver when it arrives.
If any of you is interested in going this route, please ping me and I'll send the latest CAD drawings to ModuShop.

If any of you is interested in buying one of these, also let me know. I'm thinking $3250 would be a reasonable price point for a custom built amp of this performance. Quite a few of the attendees at the Vancouver Island DIY Fest agreed with me on this.

Tom
Attached Images
File Type: jpg Finished-2.jpg (262.3 KB, 80 views)
File Type: jpg FinishedRear.jpg (359.3 KB, 86 views)
File Type: jpg Inside.jpg (470.6 KB, 91 views)
__________________
Modulus-86, 186, 286, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right

Last edited by tomchr; Yesterday at 11:55 PM.
  Reply With Quote
Old Today, 02:13 PM   #838
chrisb is offline chrisb
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
After seeing the tidy layout that configuration allowed, I wouldn’t consider doing a 686 any other way
__________________
you know I cant quit you, baby
  Reply With Quote

Reply


Modulus-686: 380W (4&#937;); 220W (8&#937;) Balanced Composite Power Amp with extremely low THDHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Modulus-86: Composite amplifier achieving <0.0004 % THD+N. tomchr Vendor's Bazaar 2407 12th September 2018 04:27 AM
SDTRANS384, MODULUS-86, POWER SUPPLU AND TROIDALS, Audio nirvana 8 alnico potstip Swap Meet 14 14th August 2015 01:06 PM
cabiant for Xpload 220w Hosam Subwoofers 19 12th March 2011 04:37 AM
Extremely low power and low loss transformers percy Tubes / Valves 12 23rd February 2005 10:30 AM
Extremely low power first amp problem m0rg Tubes / Valves 9 16th February 2004 11:05 PM


New To Site? Need Help?

All times are GMT. The time now is 08:43 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki