Solid rubber blocks - where to buy in UK???


E

Eusebius

I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
 
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C

chris_doran

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
When I was a research student, we used to use large rubber bungs for
such purposes. I don't know where you get them from outside laboratory
suppliers, though, or whether they go up to 2". Home-brewers' supplies
maybe?

Continuing to think laterally, there is a form of dense packing
material that looks like rubberised matted horse-hair. I think I have a
slab somewhere looking for a good home.

You could also try a garage or breaker's yard; I think I've seen big
rubber blocks in cars.

Chris (SE London)
 
T

The3rd Earl Of Derby

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier
to avoid microphonics. I need to build up a raised platform on which
to mount two octal valve bases so they are decoupled from the base
plate. Any ideas welcome. I'm in Hammersmith London, so anywhere
local would be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
Rubber door stops any good?
http://www.diytools.co.uk/diy/Main/Category.asp?iCategoryID=548
 
M

meow2222

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
I think 2"x2" will be way too much rubber to mount something as light
as a valve base. It'll be so stiff the sound absorption will be poor.
Try something much lighter.


NT
 
J

john2

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
Hmm, strange thing to build in this era, however a solid block of
rubber may not help much as the valve itself is so light that the
mechanical resonance will be at a high frequency and below this
frequency there won't be any decoupling. So for isolating say
loudspeaker vibrations which are usually at a few hundred Hz, it may not
be ideal.
You could try to find some stong compression springs that will take the
traditional 4BA bolts screwed in the ends. I think at the time they
used to have special anti-vibration valve holders which were like a flat
disc of phosphor bronze pressed out into a shape something like a flat
gyroscope or chronometer mounting.

john2
 
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?

.

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier
to avoid microphonics. I need to build up a raised platform on which
to mount two octal valve bases so they are decoupled from the base
plate. Any ideas welcome. I'm in Hammersmith London, so anywhere
local would be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
mount the pre amp on a sturdy shelf on the wall
 
F

Frank Erskine

I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.
In the past I've mounted valveholders using rubber grommets in the
chassis holes, obviously with washers behind the nuts to protect the
grommets from the nuts.
 
A

Andrew Gabriel

The standard way of doing this was to use a paving stone supported
on an inflated tyre inner tube, but that's for the whole thing, not
just a valve.
You could try to find some stong compression springs that will take the
traditional 4BA bolts screwed in the ends. I think at the time they
You've just created the image in my mind of Eusebius sitting listening
to his loud music, as 4BA nuts are coming loose and launching the valves
into space in the background...
 
J

John Rumm

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
I would have though you would need to create an isolated platform
(concrete pad perhaps) that you can mount on rubber mounts (e.g part
number RMM7) and fix the electronics to that:

http://www.prestwich.ndirect.co.uk/hdwrrubbersetc.htm
 
E

Eusebius

I've decided to try a couple of Chinese ceramic octal sockets (heavy)
for the two valve bases, and mounted them on a sheet of solid teflon
about 6mm thick. Just thinking how to attach this to the base plate.
First thoughts are a couple of big bolts say M6, and decouple these
with rubber grommets so they don't touch the teflon.

It then occurred to me that ordinary erasers from stationary shops
might be rather good - the rubber is soft.

I may have to do a few experiments - microphonics are quite severe. The
base for the two octal sockets may have to be heavy - like 10mm alu. I
have another preamp with directly heated triodes (notoriously
microphonic things) where the sockets are mounted on a 4mm alu plate
and that's much better for microphonics.
 
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A

Andrew Gabriel

I may have to do a few experiments - microphonics are quite severe. The
base for the two octal sockets may have to be heavy - like 10mm alu. I
have another preamp with directly heated triodes (notoriously
microphonic things) where the sockets are mounted on a 4mm alu plate
and that's much better for microphonics.
Back in my days of playing around with valve amplifiers (before
any of the valve resurgencies), a valve which had gone microphonic
was regarded as dead.
 
T

The Natural Philosopher

Eusebius said:
I need some small rubber blocks (e.g. 2" x2") for acoustical isolation
- specifically to mount valve (vacuum tube) bases on a pre-amplifier to
avoid microphonics. I need to build up a raised platform on which to
mount two octal valve bases so they are decoupled from the base plate.
Any ideas welcome. I'm in Hammersmith London, so anywhere local would
be great.

Chunks of solid rubber may well be sold as some other kind of product
(door stops?) so lateral thinking is welcome. Andy
I think you probably want high density foam rubber as valves are not
that massy.

It won't solve microphony though..thats more down to direct coupling of
the glass and grid stuff. You need an acoustic shroud over the valves
for that.

Or better still, use FETS instead. Valves have some slight advantages in
power amplifiers, none whatsoever in pre-amplifiers. Particullarly hi-fi
ones.

They are marginally nice in gutar amps where non linearity and
microphony adds a little color to a rather dull pickup sound. The non
linearity is easy to fake in solid state, the microphony is not.
 
T

The Natural Philosopher

Eusebius said:
I've decided to try a couple of Chinese ceramic octal sockets (heavy)
for the two valve bases, and mounted them on a sheet of solid teflon
about 6mm thick. Just thinking how to attach this to the base plate.
First thoughts are a couple of big bolts say M6, and decouple these
with rubber grommets so they don't touch the teflon.

It then occurred to me that ordinary erasers from stationary shops
might be rather good - the rubber is soft.

I may have to do a few experiments - microphonics are quite severe. The
base for the two octal sockets may have to be heavy - like 10mm alu. I
have another preamp with directly heated triodes (notoriously
microphonic things) where the sockets are mounted on a 4mm alu plate
and that's much better for microphonics.
Its probably down to valve design rather than mounting.

We used to 'ping' the pre-amp valves in Marshall valve amps with a
fingertip and any that were vile got used in the power amp instead ..all
ECC83 IIRC..some brands were always worse than others.
 
A

Andy Wade

The said:
We used to 'ping' the pre-amp valves in Marshall valve amps with a
fingertip and any that were vile got used in the power amp instead ..all
ECC83 IIRC..some brands were always worse than others.
Those were always a bit microphonic though and the heaters need to be
run on DC to avoid hum problems in very low level input stages for gram
pickups and tape heads, etc.

Mullard introduced the EF86 specifically to overcome those two problems.
 
E

Eusebius

Back in my days of playing around with valve amplifiers (before
any of the valve resurgencies), a valve which had gone microphonic
was regarded as dead. >>

Different thing, it isn't malfunction as you rightly refer to - these
directly heated triodes were used in radios in the field and operated
from batteries. The filaments were something like 50mA at 1.4v -
nothing at all. So the filaments were tiny and fragile, and it's these
kind of filaments that tend to sing in a microphonic way. It's a
well-known issue with these particular type of DHTs. Despite this, they
sound so good that all obstacles simply have to be overcome.
 
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E

Eusebius

It won't solve microphony though..thats more down to direct coupling of

the glass and grid stuff. You need an acoustic shroud over the valves
for that. >

Yes, this could well be true (some DHT users report good results), or
failing that some rubber damper rings


Or better still, use FETS instead. Valves have some slight advantages
in
power amplifiers, none whatsoever in pre-amplifiers. Particullarly
hi-fi ones. >>

Unfortunately this isn't true at the highest levels where you want to
squeeze the ultra details and timbre out of the system. DHTs for all
their many problems just go that little way further in clarity and
tone. You'd have to hear them to know what I'm talking about - they are
so arcane (20s and 30s as well) that there's no body of opinion to
guide your thoughts, so I wouldn't expect you to to believe all this
just on my say-so. .


They are marginally nice in gutar amps where non linearity and
microphony adds a little color to a rather dull pickup sound. The non
linearity is easy to fake in solid state, the microphony is not. >

this is another field - stage gear for effects - I'm talking about hifi
as above. As I say, all this is hard to accept without actually hearing
DHTs and there is no production preamp that uses them since they
haven't been made since the 30s and 40s. I don't expect you to believe
anything on faith alone, so I guess we just have to differ on this one.
Andy
 
?

.

Eusebius said:
this is another field - stage gear for effects - I'm talking about
hifi as above. As I say, all this is hard to accept without actually
hearing DHTs and there is no production preamp that uses them since
they haven't been made since the 30s and 40s. I don't expect you to
believe anything on faith alone, so I guess we just have to differ on
this one. Andy
have a look here:

http://snipurl.com/v6ai

hope that helped ;-)
 
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