Low noise amplifier type 450 - UK Vintage Radio Repair and Restoration Discussion Forum

thermion · 25th Mar 2024, 5:23 pm

Came across this brookdeal low noise amplifier type 450.
Could the filters be used to clean up the output of my audio sig gen with a view to taking distortion measurements on valve amps perhaps?

Radio Wrangler · 25th Mar 2024, 7:29 pm

Brookdeal were very much into things like lock-in amplifiers and boxcar detectors for pulling signals with expected characteristics out of noise. With their stuff, you have to dig out the spec sheet to be sure of just what you've got.

However, it looks like a straight-forward low noise amplifier with a few highpass and lowpass filters. The filter steps look to be decadic so if you want to clean up an audio generator's harmonics you will only get benefit with the audio osc running just below one of the lowpass filter points. As it's all about noise, then the roll-off rate is liable to not be very fast, so the harmonic suppression benefit may not be much.

Notice that the input BNC is a 75 Ohm type, which might just be for lower capacitance for scope probes etc. The output BNC is 50 Ohms type.

A lot of Brookdeal stuff is fascinating. They were at their peak in the early seventies.

David

Craig Sawyers · 25th Mar 2024, 7:42 pm

Indeed David. I used a bunch of their kit in the late 70's when digging coherent signals out of the noise. It was great stuff - discrete component, and extensive manuals.

Craig

thermion · 26th Mar 2024, 1:41 am

Ok, thanks for the replies. Maybe a bit special purpose for general use then. Can go back on the shelf.
Thanks chaps

25th Mar 2024, 5:23 pm	#1
thermion Tetrode Join Date: Dec 2011 Location: Cheshire, UK. Posts: 89	Low noise amplifier type 450 Came across this brookdeal low noise amplifier type 450. Could the filters be used to clean up the output of my audio sig gen with a view to taking distortion measurements on valve amps perhaps? Attached Thumbnails

25th Mar 2024, 7:29 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,917	Re: Low noise amplifier type 450 Brookdeal were very much into things like lock-in amplifiers and boxcar detectors for pulling signals with expected characteristics out of noise. With their stuff, you have to dig out the spec sheet to be sure of just what you've got. However, it looks like a straight-forward low noise amplifier with a few highpass and lowpass filters. The filter steps look to be decadic so if you want to clean up an audio generator's harmonics you will only get benefit with the audio osc running just below one of the lowpass filter points. As it's all about noise, then the roll-off rate is liable to not be very fast, so the harmonic suppression benefit may not be much. Notice that the input BNC is a 75 Ohm type, which might just be for lower capacitance for scope probes etc. The output BNC is 50 Ohms type. A lot of Brookdeal stuff is fascinating. They were at their peak in the early seventies. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

25th Mar 2024, 7:42 pm	#3
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 5,001	Re: Low noise amplifier type 450 Indeed David. I used a bunch of their kit in the late 70's when digging coherent signals out of the noise. It was great stuff - discrete component, and extensive manuals. Craig __________________ Doomed for a certain term to walk the night

26th Mar 2024, 1:41 am	#4
thermion Tetrode Join Date: Dec 2011 Location: Cheshire, UK. Posts: 89	Re: Low noise amplifier type 450 Ok, thanks for the replies. Maybe a bit special purpose for general use then. Can go back on the shelf. Thanks chaps