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Old 6th Mar 2018, 3:38 am   #27
joebog1
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Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
Default Re: Golden Ear Laboratory Amplifier Build

So I have made up some chassis!! and this DID take some chassis bashing .

You must remember EVERY hole started as 3 millimetre.
The "front" view is self explanatory, with the power supply on the left, and amplifier proper on the right. Front panel of power supply has on/off switch and pilot lamp ( a lovely big glass lens type from Belling and Lee, NEON of course, there is no 6 trillion candle power blue leds here !!! ).

Amplifier has output level meters, scavenged from Japanese sand amp I wrote off years ago as "not worth it".

Rear is as follows:
Power supply has fused IEC socket in centre
4 fuses two for left two for right channel, one for mains and one for HT per channel.
Two standard circular connectors for umbilical to left and right channels on the amp chassis.

Amp rear is as follows:
Bottom two holes are standard circular connectors from PSU.
Two output socket pairs ( in fact they are 19mm test terminals GOLD plated no less , as I could not get standard nickle plate variety), immediately behind the output transformer cutouts.
Two quick release fuse holders that are for setting/monitoring the output quad of 5B/254 cathode currents.

The multitude of holes on top of chassis are pretty self explanatory, and in any case will become self evident as the build progresses. N.B. the "farm circles" surrounding every valve is for convection cooling of all the glass on board.

Pic entitled "layout: is me trying to see logic into the layout, and planning wiring and component positions.

This layout took me several weeks of "thinking", and its wet season here so dragging my 60 kilogram drill press out the door every day was not possible.

I dont want to be a pest, BUT, if somebody will look at the circuit, specifically the 12BH7 drive to the 5B/254 grids, there is only ONE grid resistor, both in my redraw, and in the origional article writeup. Please correct me if I am wrong, but shouldnt it be that EACH G1 of the 5B/254 have a 1k2 resistor from the cathode of the 12BH7A, rather than one from the cathode pin of the 12BH7A to the "first" ( I would call it "the closest) grid and then hard wired to the second G1 of the second ( or furthest ) 5B/254?.
As I was taught many years ago, the resistor body should be "as close as practical" to the G1 pin on the valve socket.

So when it stops raining I will post some pics of the paint job, and the main hardware assembly, to be followed by my "build"



Cheers for now

Joe
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