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Insulating material for amp lid (like Quad405)

HarryCrumb

HarryCrumb

pfm Member
Hello,

I've got a Quad 405 which has had the insulating pad removed from the inside of the lid. I would like to replace it but I'm not sure what to search for and am having no luck.

It's a couple of mm thick. Roughly 250mm x 130mm

Can anyone point me in the right direction?

Ta
 
I am not famiilar with the amp, but sure that it was insulation? Not vibration absorber. something like Dynamat - like very thick roofing felt?
 
Thats a good point. I'm not sure if it's there to insulate, or to dampen vibrations, but the amp where it's been removed (i've got multiple 405's) certainly rattles where the others don't. The lid does sit very close to the transformer and the power supply caps though, so I assumed it was adding some level of protection as well.

Dynamat looks a bit too thick, but you may have pointed me in a better direction. Pictures below show the original material on one of the other amp lids.


DSC01544.jpg


DSC01545.jpg
 
Very tricky to say but that looks like reconstituted mica sheet - a bit of both worlds, but basically a heatshield too. Could be some type of glass fibre sheet too, but not one that I am familiar with.
 
Thanks Vinny, I will investigate along those lines... The one in the photo will be from 1976. The missing one is from almost ten years later but same principles will apply.
 
If the amp rattles, then the transformer is defective, pad or no pad. I wish I had better news, sorry. I've been there.
 
I normally use the self adhesive felt pads you get in packs from bargain shops for £1. As hp1 says it's just there to give the lid a more solid feel and stop it clanging when tapped.
 
3L fizzy drink bottles yield a large thin sheet of insulating material.
Cut the top and bottom off and cut down the length.

Pete
 
Thanks for all the suggestions. Just to clarify, there is no defect here. I have several 405’s... one of them is missing the material on the inside of the lid, and as a result sounds a little “tinny” when handling it. But, it's only the lid rattling very slightly. I also think it should be there as insulation in the event that the lid is pushed down and makes contact the transformer or power supply capacitors, and also to keep the heat from the lid (as can be seen from the scorch marks).

Here is one with it, and the one without.

DSC01549.jpg



RS components seem to have a good selection of mica sheets and other materials that I'm looking in to.
 
chartz said:
If the amp rattles, then the transformer is defective, pad or no pad. I wish I had better news, sorry. I've been there.
Click to expand...

Yes, One of my Quads had a transformer with a mechanical buzz. I was going to replace it with a torodial but in the end I got a replacement from Quad. It was almost the same price, but obviously a guaranteed fit and if I ever decide to sell it, probably better to have an original.

I just finished fitting it the other day and it's now as quiet as a mouse. I didn't bother wiring the voltage switch back in. And I used 1.5mm wire, which looks a bit toy-town'ish compared to the original wiring. It's all a learning curve for me...

DSC01550.jpg
 
HarryCrumb said:
Yes, One of my Quads had a transformer with a mechanical buzz. I was going to replace it with a torodial but in the end I got a replacement from Quad. It was almost the same price, but obviously a guaranteed fit and if I ever decide to sell it, probably better to have an original.

I just finished fitting it the other day and it's now as quiet as a mouse. I didn't bother wiring the voltage switch back in. And I used 1.5mm wire, which looks a bit toy-town'ish compared to the original wiring. It's all a learning curve for me...

DSC01550.jpg
Click to expand...
Quad’s after sales service is stunning ! Always amazes me.
 
It doesn't look like there's a toroidal transformer inside, but I learned while building an amp this year how important it is to prevent a conductive loop through the middle of the torus. If this happens, it behaves as a short circuit and bad things happen. So my first guess was the pad was to prevent the transformer mounting hardware from contacting the top cover. But then again it doesn't look like a toroid so this probably isn't the reason.
 
HarryCrumb said:
I also think it should be there as insulation in the event that the lid is pushed down and makes contact the transformer or power supply capacitors, and also to keep the heat from the lid (as can be seen from the scorch marks).
Click to expand...

The black marks are just dust deposits that build up with the movement of warm air inside the case and don't indicate high temperatures. If the internal temperatures of a 405 ever got so high that the lid needed insulation then you would have one seriously faulty amplifier. Some other amps do have electrical insulation on panels that are close to teminals as you mention but that is nearly always plastic (or plastic coated cardboard).
 
I've used that self adhesive sound deadening sheet available from good auto (car) shops

I have put it in several preamps to good effect

It's fairly cheap to buy too
 
Self adhesive neoprene sheet is available in a range of thicknesses.

I have used this to replace the crumbling foam on my Naim NAC12. In the Naim the foam holds the daughter boards firm in the mother board.
 
cctaylor said:
Self adhesive neoprene sheet is available in a range of thicknesses.

I have used this to replace the crumbling foam on my Naim NAC12. In the Naim the foam holds the daughter boards firm in the mother board.
Click to expand...


Thanks, I'll haver a look for that. This is tempting https://www.deadening.co.uk/products/dodo-dead-mat-hex-sheet It's cheap, looks good and is ready adhesive, but I don't think lining it with foil is a good idea. Neoprene would be safer.

1x1m @ 2mm £10.

https://shop.deltarubber.co.uk/rubb...d-foam-neoprene-epdm-rubber-sponge-sheet.html
 
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