I haven't purchased fans in quite a while. Think I used to use whispers for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an amp?
Most important criteria is to be as quiet as possible in order not to ruin
low level detail. Secondly, they must push a reasonable cfm to do the job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

west

in article , west at
wrote on 9/27/05 11:18 AM:

I haven't purchased fans in quite a while. Think I used to use whispers for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an amp?
Most important criteria is to be as quiet as possible in order not to ruin
low level detail. Secondly, they must push a reasonable cfm to do the job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

west


West,

A/C fans are a bad idea period.

Low voltage DC fans are cheap and effective. AFAIK they do not add much
noise, but I personally wouldn't use them in a preamp or high gain
application.

DC fans are available in muffin and squirrel cage configurations.

Muffin fans do not have much static pressure; they cannot move air well
against any resistance such as a filter. Squirrel fans offer more CFMs, but
the cage bearings tend to be noisier.

In my experience, lowest noise is possible by operating a DC muffin fan at
reduced voltage, e.g. A 12V fan at 6.3.

I've got dozens of fans (not including Andre) and would be happy to send you
some to fool with.

Jon

In article , Jon Yaeger wrote:
in article , west at
wrote on 9/27/05 11:18 AM:

I haven't purchased fans in quite a while. Think I used to use whispers for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an amp?
Most important criteria is to be as quiet as possible in order not to ruin
low level detail. Secondly, they must push a reasonable cfm to do the job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

west


West,

A/C fans are a bad idea period.

Low voltage DC fans are cheap and effective. AFAIK they do not add much
noise, but I personally wouldn't use them in a preamp or high gain
application.

DC fans are available in muffin and squirrel cage configurations.

Muffin fans do not have much static pressure; they cannot move air well
against any resistance such as a filter. Squirrel fans offer more CFMs, but
the cage bearings tend to be noisier.

In my experience, lowest noise is possible by operating a DC muffin fan at
reduced voltage, e.g. A 12V fan at 6.3.

I've got dozens of fans (not including Andre) and would be happy to send you
some to fool with.

Jon



Most AC fans are noisey.Take a look through Tiger Direct's fans.
Fan size was not determined, but they have a bunch.
Read the noise specs and CFM. Maybe 20-30 CFM or less.
Don't let the fan suck warm air. Let it blow cool air.
Try a regulated walwart from Jameco.

greg

"Jon Yaeger" wrote in message
...
in article , west at
wrote on 9/27/05 11:18 AM:

I haven't purchased fans in quite a while. Think I used to use whispers
for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an amp?
Most important criteria is to be as quiet as possible in order not to
ruin
low level detail. Secondly, they must push a reasonable cfm to do the
job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

west


West,

A/C fans are a bad idea period.

Low voltage DC fans are cheap and effective. AFAIK they do not add much
noise, but I personally wouldn't use them in a preamp or high gain
application.

DC fans are available in muffin and squirrel cage configurations.

Muffin fans do not have much static pressure; they cannot move air well
against any resistance such as a filter. Squirrel fans offer more CFMs,
but
the cage bearings tend to be noisier.

In my experience, lowest noise is possible by operating a DC muffin fan at
reduced voltage, e.g. A 12V fan at 6.3.

I've got dozens of fans (not including Andre) and would be happy to send
you
some to fool with.

Jon

Hi West and John. Hopefully you will post the results of any trials and
conclusions on RAT, as I am sure this is a topic of interest to many.

But what makes you so sure that cooling fans are required? I have built
amps up to 100W that are cooled by convection without any problems.

Iain

west wrote:

I haven't purchased fans in quite a while. Think I used to use whispers for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an amp?
Most important criteria is to be as quiet as possible in order not to ruin
low level detail. Secondly, they must push a reasonable cfm to do the job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

west

If you need a fan or fans in an amp, methinks you
dunno how to design an amp.

The only type of amp to benefit from fans are the PA amps
whose size can be reduced with fans, and it don't matter if they
whir away loudly behind the scenes at a rock concert.

But fans in the lounge room? you gotta be kidding man.

Fans help SS amps enormously more than they help normal glass amps
where the anodes inside the tubes can't get cooled by heat conduction
to a passing flow of air.
Tubes rely on being able to run happily at 200C and they radiate heat well
since the world outside is a lot cooler.


But where one uses small high powered transmitter tubes
with external copper anodes which have a heat exchanger for a flow of forced
air,
fans are essential, and a pair of small looking tubes can churn out 1,000
watts.

Use big heatsinks for SS rather than have any reliance on fans.

See the 300 watt per channel stereo amp at

http://www.turneraudio.com.au/webpic...et400w302h.jpg

Notice that the heatsinks are external, like a Quad 405.
But each channel has about 3 times the total surface area compared to the the
405,
as one would expect for 3 times the power.

You can run this amp at any power level with a sine wave and the heatsinks
never
rise to more than 65C, even into 4 ohms.

With music taken up to occasional clipping, the sinks don't get hotter than
warm, ie, not over 40C, and they are touchable without burning.

A natural air flow can stream up through well perforated bottom plate and
around the boards and the rear flat part of the sink.

Patrick Turner.

"Jon Yaeger" wrote in message
...
in article , west at
wrote on 9/27/05 11:18 AM:

I haven't purchased fans in quite a while. Think I used to use whispers
for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an
amp?
Most important criteria is to be as quiet as possible in order not to
ruin
low level detail. Secondly, they must push a reasonable cfm to do the
job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

west


West,

A/C fans are a bad idea period.

Low voltage DC fans are cheap and effective. AFAIK they do not add much
noise, but I personally wouldn't use them in a preamp or high gain
application.

DC fans are available in muffin and squirrel cage configurations.

Muffin fans do not have much static pressure; they cannot move air well
against any resistance such as a filter. Squirrel fans offer more CFMs,
but
the cage bearings tend to be noisier.

In my experience, lowest noise is possible by operating a DC muffin fan at
reduced voltage, e.g. A 12V fan at 6.3.

I've got dozens of fans (not including Andre) and would be happy to send
you
some to fool with.

Jon

Your gonna make me cry, Jon. Nobody has been that nice to me in a long time.
I would like to do some research first and get back to you.

Sniff...,
west

"Patrick Turner" wrote in message
...

snip

If you need a fan or fans in an amp, methinks you
dunno how to design an amp.


That's why I have you.


The only type of amp to benefit from fans are the PA amps
whose size can be reduced with fans, and it don't matter if they
whir away loudly behind the scenes at a rock concert.

But fans in the lounge room? you gotta be kidding man.


I had plenty of fans in the lounge when I use to sing.


Fans help SS amps enormously more than they help normal glass amps
where the anodes inside the tubes can't get cooled by heat conduction
to a passing flow of air.
Tubes rely on being able to run happily at 200C and they radiate heat well
since the world outside is a lot cooler.


But where one uses small high powered transmitter tubes
with external copper anodes which have a heat exchanger for a flow of
forced
air,
fans are essential, and a pair of small looking tubes can churn out 1,000
watts.

Use big heatsinks for SS rather than have any reliance on fans.

See the 300 watt per channel stereo amp at


That amp looks like it's only for the "gotrocks folks.


http://www.turneraudio.com.au/webpic...et400w302h.jpg

Notice that the heatsinks are external, like a Quad 405.
But each channel has about 3 times the total surface area compared to the
the
405,
as one would expect for 3 times the power.

You can run this amp at any power level with a sine wave and the heatsinks
never
rise to more than 65C, even into 4 ohms.

With music taken up to occasional clipping, the sinks don't get hotter
than
warm, ie, not over 40C, and they are touchable without burning.

A natural air flow can stream up through well perforated bottom plate and
around the boards and the rear flat part of the sink.

Patrick Turner.

thanks Professor
west

I found a pair of 220v AC fans that run very quietly at 110v AC.

I bolted them together & wired them to a single AC power cord. I have them
powered through the switched AC on the back of my pre-amp. I have them
propped up behind my Stereo-70 which now stays nice and cool.

"west" wrote in message
m...
: "Jon Yaeger" wrote in message
: ...
: in article , west at
: wrote on 9/27/05 11:18 AM:
:
: I haven't purchased fans in quite a while. Think I used to use whispers
: for
: medical gear.
: Question: What do you recommend for possibly 2 fans installed in an
: amp?
: Most important criteria is to be as quiet as possible in order not to
: ruin
: low level detail. Secondly, they must push a reasonable cfm to do the
: job
: of cooling tubes. Is there advantages in DC or AC types, save hum
: considerations? Suggestions? Thank you.
:
: west
:
:
: West,
:
: A/C fans are a bad idea period.
:
: Low voltage DC fans are cheap and effective. AFAIK they do not add much
: noise, but I personally wouldn't use them in a preamp or high gain
: application.
:
: DC fans are available in muffin and squirrel cage configurations.
:
: Muffin fans do not have much static pressure; they cannot move air well
: against any resistance such as a filter. Squirrel fans offer more CFMs,
: but
: the cage bearings tend to be noisier.
:
: In my experience, lowest noise is possible by operating a DC muffin fan at
: reduced voltage, e.g. A 12V fan at 6.3.
:
: I've got dozens of fans (not including Andre) and would be happy to send
: you
: some to fool with.
:
: Jon
:
: Your gonna make me cry, Jon. Nobody has been that nice to me in a long time.
: I would like to do some research first and get back to you.
:
: Sniff...,
: west
:
posted 11 months ago:
Mouser has a 92 mm fan that's allready in whispermode at the nominal
2050 rpm.
It's cat# 664-D9225LB-12V 36 CFM at
25 dBA noise l. for USD 12.50.
Running it below 12V reduces the noise further and you still have quite some
flow left.

Rudy

"west" wrote in message
m...
I haven't purchased fans in quite a while. Think I used to use whispers for
medical gear.
Question: What do you recommend for possibly 2 fans installed in an amp?
Most important criteria is to be as quiet as possible in order not to ruin
low level detail. Secondly, they must push a reasonable cfm to do the job
of cooling tubes. Is there advantages in DC or AC types, save hum
considerations? Suggestions? Thank you.

**Most decent fan manufacturers provide noise and airflow figures for their
fans. Choose the largest fan you possibly can. Large fans, operating at low
RPM will usually be quieter than small fans funning fast. To accomplish
this, you will need to look at AC fans. Most are 'impedance protected' and a
simple (power) resistor can be used to lower fan RPM to the desired level.
DC fans are not easily speed controllable. Here's some typical figures:

80mm fan - 23CFM (Cubic Feet per Minute) Sorry, figures are not Metric
120mm fan - 85CFM
150mm fan - 230CFM

As you can see, the amount of air moved increases dramatically, with
increasing fan diameters. Use a big fan and run it slow. It is far and away
the best solution. I've used 150mm fans, running slow, moving the same
amount of air as a 120mm fan running flat out. Under these conditions, the
150mm fan is almost totally inaudible. Another issue are bearings. Sleeve
bearings don't last as long as ball race bearings, but are generally
quieter.

BTW: If you run two AC fans in series, you'll get quieter operation and
fewer losses, compared to using a series resistor.


--
Trevor Wilson
www.rageaudio.com.au

Yep,
Exactly what I did. Using the same 4" (100 mm) cast aluminium fan for nearly
10 + years, works great. Not a cheapie though. Every motor head in sight
will tell you never to operate an AC motor at a voltage lower than its
designed for but so far so good. I use it because I have some tube gear in
an enclosed cabinet. Sometime a must when you have to deal with a member of
the fairer sex in your household.
M
"- - : R A T B o y : - -" - - : R A T B o y : - wrote in
message ...
I found a pair of 220v AC fans that run very quietly at 110v AC.

I bolted them together & wired them to a single AC power cord. I have
them powered through the switched AC on the back of my pre-amp. I have
them propped up behind my Stereo-70 which now stays nice and cool.