Dared MP-2a3c mods - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 14th December 2011, 03:47 PM   #1
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Default Dared MP-2a3c mods

I recently decided to take a closer look at the Dared MP-2a3c innards and see how it's made. At first sight it looks like simple PCB that is well laid out. I see some Nichicon caps in the power supply and some cheap coupling caps that need to be replaced. Internal signal wires also look cheap and cheesy.

The four black coupling caps are .47k, 2 of them 400v and two 630v. I looked at Auricaps and Solen for replacement. My concern is that Auricaps are 600v rating (the next one is 1500v), and I wonder if they could substitute the 630v ones. I could always use Solen caps for the 630v pair...

Also is there anything else I should or could address while dissecting this amp?

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 14th December 2011, 07:45 PM   #2
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
In the third pic you can see OMRON H3Y-2 5 sec timer, which is used as some sort of "soft starter" which is not. I would imagine it simply allows heater filaments to get to temperature before kicking in the current for the rest of the electronics. Its operation produces loud "pop". I wonder if it could be replace with suitable real soft start pcb assembly.
  Reply With Quote
Old 14th December 2011, 09:08 PM   #3
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Quote:
Originally Posted by ClefChef View Post
Also is there anything else I should or could address while dissecting this amp?
I see a pair of pig-tail fuses soldered to the PCB. I would remove these and run wires to a pair of through chassis fuse holders mounted somewhere for convenience sake. Perhaps on the rear apron if space allows, or even on the top side. This makes replacing them very easy should you ever have to.

600 volt caps for 630V, virtually the same....so no problem-o. The actual in circuit voltage is probably less anyway. But the brand name units may well be much bigger and more difficult to mount.
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 14th December 2011, 09:49 PM   #4
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
0.47 auricaps are half the size of the original ones, so fitment should be no problem. I will install fuse holders, maybe next to delay circuit relay.
Speaking of Omron relay - is there anything better than this semi-mechanical timer?
  Reply With Quote
Old 15th December 2011, 02:16 AM   #5
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Quote:
Originally Posted by ClefChef View Post
- is there anything better than this semi-mechanical timer?
I'm not prepared to say what, if anything, is better since I don't know for sure just what it's doing. But I will say there is nothing wrong with relays. But if it makes a loud pop, then perhaps a simple timer and solid state relay might work better. Or maybe a capacitor across the contacts.

I am surprised that an Auricap is so small. But then I never buy them. I'm not convinced they're worth the price. I'm too old school and have many hundreds of capacitors stashed away. The caps in your picture look pretty small to begin with using the 4-pin socket as a size reference. Most likely made in Asia. Below are some various .47/600v units except the first one. ICC, Rifa, ERO/Roderstein, socket, Wima & Sprague Vitamin Q.
Attached Images
File Type: jpg MVC-010F.JPG (131.3 KB, 222 views)
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 19th December 2011, 08:26 PM   #6
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Did the upgrade. Auricap 600v caps were significantly larger and some fitment issues arose. Everything is back together and the amp sounds really good. The stock "audiophile" caps were tossed - I had to cut their leads and solder Auricap wires to them (wires were too thick for pcb board).
  Reply With Quote
Old 23rd December 2011, 03:18 AM   #7
diyAudio Member
 
ClefChef's Avatar
 
Join Date: Sep 2011
Click the image to open in full size.

I replaced the coupling caps with Auricaps. As you can see they are significantly larger than the stock ones, I should've probably used the 450V instead of 600V...But esthetics aside everything sounds great.

I took a closer look at the PCB. I don't have the schematics and I am no expert in electronics but...The 2a3c filament circuit is currently powered by 2.5 V ac current which may cause some audible 120 Hz hum. On the PCB we can see the provision for DC circuitry with a rectifier and filtering cap for each tube. I circled it red on the top of the pic. The markings on the board are Q2 and Q3 for rectifiers and C20 and C21 for caps. It is somewhat simplistic but I wonder if it would work.

On the bottom of the pic I circled two bypass (probably) 100mf caps and two empty spaces for similar caps - one for each 12a..7 tube. Some dared amps I looked at have no caps there at all. It leaves some space to experiment I guess, what cap does what to the sound.

I would ask experts to chime in. Again, my knowledge of electronic circuits is on 101 level so please forgive me if my comments look silly...

Last edited by ClefChef; 23rd December 2011 at 03:31 AM.
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
ART Tube MP mods? screamersusa Instruments and Amps 2 5th April 2011 08:10 AM
Dared mp30 ziocalepino Tubes / Valves 2 28th November 2010 01:18 PM
2A3C Mono plate: Shuguang Or Sovtek? levelfive Tubes / Valves 18 5th December 2008 01:47 PM
Help with dared MP-15, please! reyrios Tubes / Valves 3 18th November 2007 09:07 AM
Shuagang 2A3C cantskienuf Tubes / Valves 1 28th April 2005 02:15 PM


New To Site? Need Help?

All times are GMT. The time now is 04:59 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2