"Powell" said:

Microphonics are your worst enemy in tube phono stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.


You mean those silicone rings?
They only help to avoid bringing the glass-enevelope in resonance.
Otherwise, for the innards of a tube, they do nothing.
Remember that tube characteristics are highly dependent on the
relative placing of the internal electrodes.
When they get moved relative to each other, parameters will vary.
That's something that a dampening ring *outside* the glass container
can't prevent.

The only "tweak" that is a bit helpful is to mount the tube socket
with rubber braces and spacers onto the chassis.

Even then, a really microphonic tube will manifest itself, and has to
be replaced.

--

"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005

Sander deWaal wrote:

"Powell" said:

Microphonics are your worst enemy in tube phono stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.

You mean those silicone rings?
They only help to avoid bringing the glass-enevelope in resonance.
Otherwise, for the innards of a tube, they do nothing.
Remember that tube characteristics are highly dependent on the
relative placing of the internal electrodes.
When they get moved relative to each other, parameters will vary.
That's something that a dampening ring *outside* the glass container
can't prevent.

The only "tweak" that is a bit helpful is to mount the tube socket
with rubber braces and spacers onto the chassis.

Even then, a really microphonic tube will manifest itself, and has to
be replaced.

It seems that anti-vibration bases are no longer available. I tried
looking once without success.

Graham

Pooh Bear said:

The only "tweak" that is a bit helpful is to mount the tube socket
with rubber braces and spacers onto the chassis.


It seems that anti-vibration bases are no longer available. I tried
looking once without success.


One can use rubber piping gaskets and rubber washers.

Did I already mention it here that tube audio is a DIY thing? :-)

--

"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005

Sander deWaal wrote:
Pooh Bear said:

The only "tweak" that is a bit helpful is to mount the tube socket
with rubber braces and spacers onto the chassis.


It seems that anti-vibration bases are no longer available. I tried
looking once without success.


One can use rubber piping gaskets and rubber washers.

Did I already mention it here that tube audio is a DIY thing? :-)


All the servo kits for RC aircraft have little isolation kits
included. Their vibe environments are quite harsh and motor vibe can
affect servo performance. Of course in that hobby, servo failure
often has catastrophic results.

We have used these guys for helping design isolation of telematics in
extremely harsh construction equipment environment. The web site is
very informative on the science of isolation.

http://www.earshockandvibe.com/

ScottW

"Powell" wrote in message
...

"Sander deWaal" wrote

I'm in the process of designing a pair of monoblocks
based on the Marantz Model 9. Any recommendations
on 6DJ8/6922/7308s?


Microphonics are your worst enemy in tube phono stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.

Many of them have active portions made up of silicon.

Arny Krueger wrote:

"Powell" wrote in message
...

"Sander deWaal" wrote

I'm in the process of designing a pair of monoblocks
based on the Marantz Model 9. Any recommendations
on 6DJ8/6922/7308s?


Microphonics are your worst enemy in tube phono stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.

Many of them have active portions made up of silicon.

I think you mean silicone actually Arny ! ;-)

Graham

"Pooh Bear" wrote in message
...


Arny Krueger wrote:

"Powell" wrote in message
...

"Sander deWaal" wrote

I'm in the process of designing a pair of monoblocks
based on the Marantz Model 9. Any recommendations
on 6DJ8/6922/7308s?


Microphonics are your worst enemy in tube phono stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.

Many of them have active portions made up of silicon.

I think you mean silicone actually Arny ! ;-)

Well that too.

However there are or at least have been pin-for-pin replacements for common
tube types. My radars in the late 60s had silicon 300B replacements in their
power supplies. There were also silicon 6AU6s, 6AL5s, 12AU7s, etc. AFAIK
none of them were microphonic.

Pooh Bear wrote:

I stand corrected. Been a very long time since I had occaison to study that.
IIRC the BR smoothes out the ripple from AC, no?

The reservoir caps do that ( smooth the ripple from the rectified AC ).

(Basic power supply info)

The diodes in the rectifier circuit convert AC to DC by allowing
current to only flow in one direction. The output from the rectifiers
is then filtered into (sort of) smooth DC by capacitors. Ahead of all
this, of course, is the big, heavy (and expensive) thing, the
transformer, which has as it's input the high-voltage AC from the
wall, and outputs a lower voltage into the rectifier circuit.

As an example, the transformer in a 100W/channel amp will step the
120VAC input down to (say) 34VAC at the output, which would then be
rectified and filtered to +/- 47VDC (34 * sqrt(2) - diode drops) at
no load (zero volume). These voltages are supplied directly to the
output stage of the amplifier, and would allow the amplifier to
deliver a peak out voltage of about 33V (RMS), which would allow a
peak output into an 8-ohm load of about 136W. Under heavy load (high
volume) the voltage from the power supply will drop, due to increased
voltage drops across the resistance in the transformer's windings and
rectifier diodes, bringing the the continuous power output of the
amplifier down closer to it's 100W/channel rating.

"Sander deWaal"

Microphonics are your worst enemy in tube phono
stages.

True, and there are helpful tube dampening mechanisms
to reduce microphonics.

You mean those silicone rings?
They only help to avoid bringing the glass-enevelope in resonance.
Otherwise, for the innards of a tube, they do nothing.

Example of products:
3M Viscoelastic tube dampener ($3.50)

Ensemble Tubesox damper ($65 pr)
which is make of Kevlar and copper thread.
This works fine but doesn't fit some of the
unusually small based tubes like the 6922
Mullard.

Bluenote - Midas Hi-Fi ($80 pr.)

Right-Way Audio - Tophats ($120).

Audio Research, as I remember, has dampening
rings for sale, too.


Remember that tube characteristics are highly dependent
on the relative placing of the internal electrodes.
When they get moved relative to each other, parameters will
vary. That's something that a dampening ring *outside* the
glass container can't prevent.

The only "tweak" that is a bit helpful is to mount the
tube socket with rubber braces and spacers onto the
chassis.

Apparently 6922/6DJ8 are also subject to EMF/RF
distortion. In my microphone preamp they are fully
shielded (metal screw-down covers).


Even then, a really microphonic tube will manifest itself,
and has to be replaced.

It has not been mentioned but there are also tube
devices designed to reduce the temp of the glass
envelope.