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)
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)
Attachments
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.
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.
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).Nardis said:
Chris
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
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
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.
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.
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 wasn’t 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 hadn’t. 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.
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 hadn’t. 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.
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