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 2nd February 2020, 06:12 PM   #1201
maxhifi is offline maxhifi  Canada
diyAudio Member
 
Join Date: Oct 2005
One quick question:

On your website, you suggest a 2 x 25VAC transformer for the Modulus 686.

National Semiconductor, in their publication for the BPA200, specifies a Toroid Corp of Maryland 2 x 30VAC secondary transformer.

Some years ago, I assembled most of the parts to construct a BPA200, including a Toroid Corp of Maryland 820VA 30VAC x 2 transformer, to use with a stereo version of the BPA200. Per the Toroid Corp website, the DC output voltage of this transformer should be about 38.5V, when used with a full wave rectifier, and a "large capacitor".

My question is, would the transformer I currently possess be suitable to power a pair of Modulus 686 amplifiers, or does the extra 5 volts in your opinion represent a show stopper?
  Reply With Quote
Old 2nd February 2020, 06:50 PM   #1202
Kay Pirinha is offline Kay Pirinha  Germany
diyAudio Member
 
Kay Pirinha's Avatar
 
Join Date: Oct 2011
Location: Somewhere in Germany
As the datasheet allows 42 Vdc as maximum rail voltages under load, you should be on the safe side. Hopefully Tom might chime in, though.
Best regards!
__________________
"I spent a lot of money on booze, birds and fast cars. The rest I just squandered." (George Best)
  Reply With Quote
Old 2nd February 2020, 09:05 PM   #1203
tomchr is online now tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
The LM3886 data sheet specifies an ABS MAX of 42 V with signal applied. If you go beyond 42 V, the reliability of the LM3886 will be affected. This could mean anything from, "the IC will last 8 years instead of 10 years" to "the IC will last 10 ms".

You will also notice that all the parameters in the data sheet are given for the 28 V operating point. The data sheet only mentions 35 V for the power rating into 8 Ω.

The way I read this is: For the best performance, operate the LM3886 with 28 V for 4 Ω load and 35 V with 8 Ω load (or if you want to support both 4 Ω and 8 Ω loads, then run it at 28 V and accept lower output power into 8 Ω). If you go beyond 28/35 V with 4,8 Ω loads, respectively, accept degraded performance.

This is consistent with my experience in the lab. I generally find that 28-30 V is the maximum supply voltage that results in good performance with 4 Ω load. If you push beyond that, the SPiKe protection kicks in a bit earlier (higher supply voltage -> greater power dissipation -> greater temperature differential across the thermal impedance of the package -> SPiKe engages earlier). This results in degraded performance (higher THD, lower max output power).

With the bridge-parallel approach I take in the Modulus-686, you'll get the full performance with a 36 V power supply. That's why I suggest that as the design target. Pushing beyond 36 V will not provide any benefit, so why go there?!

FWIW, I run my "daily driver" Modulus-686 on 27 V using a pair of Mean Well RPS-400-27-C switching supplies. That provides 130 W (8 Ω), 200 W (4 Ω) and will fit in a ModuShop Mini Dissipante 3U x 330 x 300 mm chassis. I love the form factor and 130 W is plenty of power for me (even with a sizeable listening space and mid-low efficiency KEF R700 8 Ω speakers).
If you want to push to 36 V, you need a 4U x 300 mm heat sink (assuming the ModuShop Dissipante heat sinks).

Tom
__________________
Modulus-86, 186, 286, & 686: 40-240W (8Ω), <-120dB THD. HP-2 Headphone Amp: 660mW, <-130dB THD. Taming the LM3886.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right

Last edited by tomchr; 2nd February 2020 at 09:09 PM.
  Reply With Quote
Old 9th February 2020, 01:44 PM   #1204
JustLiSten is offline JustLiSten  France
diyAudio Member
 
Join Date: Feb 2020
Location: Bretagne (Britany)
Hello,
Newcomer to this forum, I am awaiting receipt of the Modulus 686 kit and I have received most of the components to complete the assembly.
So I will certainly open a FAQ bar to benefit from each other's experiences.
You can find a bit of me by following this link JustLiSten | Living Leedh
If I decided to undertake this realization it was following an experience of presentation of a Leedh E2 glass speaker model (glass diaphragm technology, ironless motor, ferrofluid seal), from a French manufacturer and friend that I accompanied to a presentation of his latest model at Munich High End 2016. Munich High-End 2016 | Living Leedh
These fabulous speakers were powered by a prototype amplifier based on 3868 ( << L’Ampli >>, un prototype | Living Leedh )
This amp will not have a follow-up but I could appreciate the sound. Convinced tubist, I find that the 3886-based amps sound a bit like tubes with more power qualities.
See you soon, with all my questions
Best regards
JLS
  Reply With Quote
Old 12th February 2020, 06:52 AM   #1205
absolutk is offline absolutk  United States
diyAudio Member
 
Join Date: Jul 2017
Location: San Francisco
For anyone wanting to try out Tom's insanely good amplifier, my build is looking for a new and loving home...

FS: Neurochrome Modulus 686 Amplifier - top of the line build!
  Reply With Quote
Old 14th February 2020, 10:59 PM   #1206
PScal is offline PScal  United States
diyAudio Member
 
Join Date: Jan 2010
Location: Little Rock, Arkansas
I framed the inside of my enclosure with some aluminum angle and bent up some perforated aluminum sheet. Now the electronics are fully encased.



Click the image to open in full size.


Click the image to open in full size.


Click the image to open in full size.
  Reply With Quote
Old 15th February 2020, 12:31 AM   #1207
tomchr is online now tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
I like the vertical design. Nice use of perf plate too. Modulus-Monolith.

Tom
__________________
Modulus-86, 186, 286, & 686: 40-240W (8Ω), <-120dB THD. HP-2 Headphone Amp: 660mW, <-130dB THD. Taming the LM3886.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
  Reply With Quote
Old 20th February 2020, 01:58 PM   #1208
JustLiSten is offline JustLiSten  France
diyAudio Member
 
Join Date: Feb 2020
Location: Bretagne (Britany)
Built the enclosure "around" the heatsink : good idea !
  Reply With Quote
Old 23rd February 2020, 01:37 PM   #1209
JustLiSten is offline JustLiSten  France
diyAudio Member
 
Join Date: Feb 2020
Location: Bretagne (Britany)
Bonjour tous.
Work in progress.
The plate is 243x60x3 mm.
h= 60 mm because my idea is to make some thermal measurements on the LM3886 and the heatsink with this kind of tool: https://fr.farnell.com/pico-technolo...deg/dp/7820178
Just for fun.
Thank you Tom for your drill templates. You save my life !


IMG_1215.JPG - Google Drive

Last edited by JustLiSten; 23rd February 2020 at 02:03 PM.
  Reply With Quote
Old 24th February 2020, 10:49 AM   #1210
JustLiSten is offline JustLiSten  France
diyAudio Member
 
Join Date: Feb 2020
Location: Bretagne (Britany)
@PScal :
What kind of heatsink do you use ?
Thanks
  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 2452 11th February 2020 11:13 PM
SDTRANS384, MODULUS-86, POWER SUPPLU AND TROIDALS, Audio nirvana 8 alnico potstip Swap Meet 14 14th August 2015 02:06 PM
cabiant for Xpload 220w Hosam Subwoofers 19 12th March 2011 05:37 AM
Extremely low power and low loss transformers percy Tubes / Valves 12 23rd February 2005 11:30 AM
Extremely low power first amp problem m0rg Tubes / Valves 9 17th February 2004 12:05 AM


New To Site? Need Help?

All times are GMT. The time now is 04:57 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki