Why did Ferrograph do this?
 

Here's a photo of the amplifier in a Ferrograph 6 series. I wonder why they chose to install the valves in this way? It seems quite labour-intensive and therefore expensive!

Re: Why did Ferrograph do this?
 

Hi,
Do they plug into a second valve holder in the chassis?
If so, and it's just my guess, maybe it's a convenient way to alter the amp characteristics and/or equalisation curves, etc.
Cheers, Pete.

Re: Why did Ferrograph do this?
 

Hi Pete,
The valveholders on the chassis have only the interconnecting wiring, most of the passives are wired in between the B9A plug and the remote valveholder. It is quite odd!

Re: Why did Ferrograph do this?
 

Service by module replacement?

David

Re: Why did Ferrograph do this?
 

It's not a cheap way to do things, but it does make repairs, ad-hoc changes/customisations a lot easier.

Plenty of stuff in the 1950s/early-60s - specially military gear and 'instrumentation' like oscilloscopes - was built similarly. The US called these "cordwood modules". The "Philbrick" company in the US produced op-amps using the same idea -

http://www.cowardstereoview.com/analog/philk2w.jpg

http://www.dvq.com/oldcomp/analog/Ph...dium/gapr2.JPG

in 1952!

[This being one of the designs which made the late Bob Pease famous].

Re: Why did Ferrograph do this?
 

Its not unique to the Ferrograph 633 , Revox also did a similar thing. It offers space saving economies as the 633 is a three head design so more circuit to squeeze into the same space as a conventional two head mono design. The stereo models utilised an extra chassis. Malcom Hill designed this model.

A neat solution.

regards

Terry

Re: Why did Ferrograph do this?
 

Thanks Terry, it seems like a neat solution to a real-estate problem!