[Amps] Fan Noise in GS-35b Amplifiers

[Carl]

Ive already mentioned the EBM Papst 4600N as an adequate substitute earlier 
in this thread. Ive used them and altho havent measured backpressure the 
spec sheet curve inticates it handles backpressure quite well unlike most 
muffin type fans.
It does a more than adequate job on three 3CX800A7's as factory installed in 
the LK-800 series.

Carl
KM1H


----- Original Message ----- 
From: "John G3UUT" <amps at grebe.plus.com>
To: <amps at contesting.com>
Sent: Friday, February 21, 2014 6:03 PM
Subject: Re: [Amps] Fan Noise in GS-35b Amplifiers


>A possible blower you could consider is the EBM Papst G1G108-AB17-02, this 
>is capable of over 100 CFM at low pressures and could well be adequate if 
>you are not going to push things too hard.  The good thing about it is that 
>the speed can be controlled by an external DC voltage or resistor network 
>which means it's possible to easily implement schemes to reduce the speed / 
>noise when the temp of the outlet air is low.
>
> I've never actually used one of these these blowers but had it in mind for 
> an amp I've been planning so don't blame me if it's really noisy.  However 
> I don't think it's likely to be too bad because; a) its a diecast spiral 
> and in my experience these are quieter than sheet metal and b) My 
> experience with Papst blowers and fans has been very positive.  Anybody 
> else tried them?
>
> If all else fails just cook the thing like the rest of us do, the GS35b is 
> just about the most rugged valve there is and they are not too expensive 
> either and if you really fry it you can get your money back on the cooler 
> at the scrap metal dealer.
>
> Have fun
> John G3UUT
>
> On 19/02/2014 16:07, Jack C. Shutt wrote:
>> I have gathered from all the info that I have read on amps using the 
>> GS-35b that a healthy air flow is necessary to keep these tubes happy. 
>> Unfortunately, the 100 CFM squirrel cage blower that is recommended for 
>> this purpose is quite noisy.  Any suggestions for an effective cooling 
>> arrangement that is quieter?  I thought about remotely locating the 
>> blower and using a hose duct to the amp, but this is just not practical 
>> in my shack.  Suggestions?   73,  Jack, W9GT
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