Music Angel - Help wanted - 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 25th March 2008, 08:47 PM   #1
Nardis is offline Nardis  United Kingdom
diyAudio Member
 
Join Date: Aug 2003
Location: London
Default Music Angel - Help wanted

I have a Music Angel which uses a DCC90 in the input stage, driving 2A3s and 300Bs.

The little DCC90 is very prone to microphony and is set in a little cage. It is mounted on a base set in a rubber sheet and well below the level of the top plate. All this is supposed to decouple it but it isn't enough. I want to get it out to put some damping rings on it.

Does anyone have any bright ideas about how to get it out without taking the whole amp apart? The cage seems to be bolted on from below, but to get at the bolts it looks like I would have to take out the plate on which all the other bases are mounted. There seems to be plenty of opportunity for mishaps on the way. It doesn't seem to dismantle from the top.

It's one of those stupid frustrating puzzles. I want to avoid taking the amp apart because it weighs 25kg and since I've just had surgery on my back I can't move the thing from its shelf and turn it over!

(For the curious, here's a photo of another Music Angel model showing the cage)
Attached Images
File Type: jpg ma_dcc90.jpg (49.1 KB, 259 views)
  Reply With Quote
Old 25th March 2008, 09:34 PM   #2
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
I've never had one of these but have you tried loosening what looks like acorn nuts on top and see if it will come apart that way.
__________________
"I regard the brain as a computer which will stop working when it's components fail. There is no heaven or afterlife for broken down computers. That is a fairy story for people afraid of the dark." ~Stephen Hawking
  Reply With Quote
Old 25th March 2008, 11:42 PM   #3
Nardis is offline Nardis  United Kingdom
diyAudio Member
 
Join Date: Aug 2003
Location: London
Thanks, Hollowstate, but I tried that.
The nuts appear to be 5.5mm acorn nuts and I have had a socket spanner on them. I tried clamping the steel shafts tightly with grips. It is possible to rotate the acorn nut with force, but something somewhere out of sight must be rotating with it. I had been expecting it to unscrew this way, but it doesn't.

Logic says the steel shafts should be in 3 sections with internal thread,each holding one of the horizontal rings. These sections .should screw into each other and the top ring held in place with the acorn nut. However it does not seem to want to behave like that.

I was hoping someone had found a way of getting the DCC90 out of its base when the base is mounted on a pliant piece of rubber and the cage has so little clearance that I can't get a grip on the glass. If all else fails I'll have to hacksaw the layers of the cage off until I get it down far enough to extract the DCC90.
  Reply With Quote
Old 26th March 2008, 12:12 AM   #4
chrish is offline chrish  Australia
diyAudio Member
 
chrish's Avatar
 
Join Date: Oct 2003
Location: Sydney
Quote:
Originally posted by Nardis

Logic says the steel shafts should be in 3 sections with internal thread,each holding one of the horizontal rings. These sections .should screw into each other and the top ring held in place with the acorn nut. However it does not seem to want to behave like that.

Maybe the cage supports are bolts or threaded shafts with sections of steel tubing. This would be why trying to undo the nut is not working. You might have to look underneath the chassis to see if you can place a spanner in there to stop it turning. Can you fit something like a small screwdriver under the valve to prise it up? If you attack it with a hacksaw you will probably do some damage to the chassis (or I know I would if I tried something like that).

Chris
  Reply With Quote
Old 26th March 2008, 02:08 AM   #5
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
The cage is like this:

under chassis - acorn nut onto a piece of M4 threaded rod.

Rod goes through chassis and then the 3 lower sleeves are slipped on, then a ring, then the next 3 sleeves and another ring and so on. The acorn nut is last then on top. You need to grip the acorn nut inside the chassis to open it.

Apart from looks, those cages are useless as regards microphony. Can't see tube rings doing that much either. Is there an alternative tube/make thats less microphonic thats a direct sub?

Fran
  Reply With Quote
Old 27th March 2008, 05:17 PM   #6
Nardis is offline Nardis  United Kingdom
diyAudio Member
 
Join Date: Aug 2003
Location: London
Thanks Woodturner-Fran.

Using your description I was able to twist the sleeve sections against the central rod and create enough friction to get two of the acorn nuts off. The third was cross threaded, and since I could not get the ECC90 out of the socket, my only choice was to hacksaw the acorn nut from the shaft.

I had intended to replace only the bottom ring but I found that the central rods are not threaded all the way only at their ends. So I can't just refit the bottom ring and use the acorn nuts to hold it firm.

I tried a temporary fix, packing the sleeve pieces with Blutack. It looks ok and I can remove the DCC90, which was what I originally intended, but it obviously needs gluing with something heat tolerant.

LESSON LEARNED: avoid designs with fancy little cages. It took half a day to fit tube damping rings!
MUSIC ANGEL OWNERS BEWARE!. There are some powerful magetic forces around these valve sockets, and I almost lost a screw into the interior. If you do dismantle the cage, use masking tape to cover any openings in the chassis.
  Reply With Quote
Old 28th March 2008, 12:07 AM   #7
Nardis is offline Nardis  United Kingdom
diyAudio Member
 
Join Date: Aug 2003
Location: London
After a talk with another Music Angel owner and a second examination of the area around the DCC90 I realise that I got the matter of magnetism wrong. It wasnít so much that the MA was magnetic as that for some reason two of the threaded rods in the cage had become magnetised.

What I assumed was that magnetism from the amp was pulling a piece of metal across the stainless steel top when in fact I was watching a powerful little magnet heading for some nice iron to cling on to. The puzzling thing is why two of three 4mm bolts had become magnetic, but one hadnít. Maybe they were magnetic before the amp was assembled? Its build quality was quite poor. It took a lot of work by friends who know more about these Chinese bargains than I do, to get it sounding good.

Meanwhile the warning about taping over the sockets still stands, even if the reason is different.
  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
music angel 845 SET PeterParsons Tubes / Valves 8 11th November 2013 04:12 AM
Music Angel Amplifiers OXAUDIO Tubes / Valves 64 25th August 2012 01:47 PM
Music angel XD-SE EL34 Kippy Tubes / Valves 18 12th January 2011 09:36 PM
Music Angel franckM Tubes / Valves 11 11th June 2007 12:24 AM


New To Site? Need Help?

All times are GMT. The time now is 08:48 PM.


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