16-05-2020, 01:52 PM
I think that somewhere in the last few years chip manufacturing drew a line in the sand and my construction was about as much as your average hobbyist could attempt with regular tools.
Did you notice how ugly it looks?
The box is made from mu metal, I was thinking about various things back then, but in general I only seem to be able to do ugly.
I take my hat off to our more esteemed members such as Yorkie who seem to be able to produce lovely hobby boxes with ease.
My audio sources at the time were
All of these played through my prototype volume control without any problem, so the next thing to consider was how to do the source switching. I had previously designed a demultiplexer for analysing analogue (gas pressure) signals, so I had a good idea about what I needed to do next.
I should explain that I wanted to have the ability to cue up a record and a CD copy at the same time and then switch between them for A B comparison purposes. During breadboarding this worked very well, but one time when I lifted the arm off the record I could still hear the CD bleeding through. It was oh so feint, way too feint for anyone but me to be concerned with, but it was there and that annoyed me.
Much hair pulling later, I gave up and tried a cheap AV switching box from Maplin which turned out to be very much worse when tested under the same conditions. Not really a problem, but it bugged me.
Eventually I did a complete U turn building my own solid state RIAA phono-amp, combining a stepped attenuator with a two pole rotary switch. You can see how this fitted in with my diy class A set up.
Not so ugly this time because I re-purposed a wooden sleeve and an unloved Bush radiogram.
Did you notice how ugly it looks?
The box is made from mu metal, I was thinking about various things back then, but in general I only seem to be able to do ugly.
I take my hat off to our more esteemed members such as Yorkie who seem to be able to produce lovely hobby boxes with ease.
My audio sources at the time were
- Phono pre-amp
- CD player
- Mini disc player
- Computer
- Spare/Mp3 player
All of these played through my prototype volume control without any problem, so the next thing to consider was how to do the source switching. I had previously designed a demultiplexer for analysing analogue (gas pressure) signals, so I had a good idea about what I needed to do next.
I should explain that I wanted to have the ability to cue up a record and a CD copy at the same time and then switch between them for A B comparison purposes. During breadboarding this worked very well, but one time when I lifted the arm off the record I could still hear the CD bleeding through. It was oh so feint, way too feint for anyone but me to be concerned with, but it was there and that annoyed me.
Much hair pulling later, I gave up and tried a cheap AV switching box from Maplin which turned out to be very much worse when tested under the same conditions. Not really a problem, but it bugged me.
Eventually I did a complete U turn building my own solid state RIAA phono-amp, combining a stepped attenuator with a two pole rotary switch. You can see how this fitted in with my diy class A set up.
Not so ugly this time because I re-purposed a wooden sleeve and an unloved Bush radiogram.
