Zener Limiter Build

[anvl]

" both channels sound scratchy and poppy, unusably so if the unit is driven" ... probably related to matching zener diodes (in my opinion)

 

[Cqwet Dbdfte]

Boards are finished, lets hope the layout is ok. Circuit breaks up pretty well into input, output and side chain. Power supply will be remote. Only a couple of slight component changes over the original circuit - have adjusted the HF boost and the pad at the input. Chassis arrived yesterday but the wings/ears were bent during shipping.

Using perf boards for a simple circuit is OK , but for these circuits it is faster and cheaper to order PCB's from JLC, GO-GO etc for a few bucks.
Too many things to go wrong in those type boards and trouble shooting is harder without a CAD program to do error checking.
Pain has thought me.

 

[Ó Draighnáin]

I have matched zeners now. I used the first test jig I built (absolute - the one posted a few comments back) to group similar zeners and then the second jig (relative) to match pairs. Without the initial grouping matching pairs would be quite tedious.

 

[slipperyflax]

Did swapping zeners fix your noise issue? I've had problems with noisy zeners in the past but swapped them and everything was fine after that. Can't remember any details though

 

[Cqwet Dbdfte]

Zeners in clipping are classic noise sources.

 

[Ó Draighnáin]

I have reduced it considerably but have not eliminated it yet. Swapping out the zeners definitely had an impact. I have made a lot of progress but I consider this unit unfinished as of yet.

There a few things to do in addition to more zener swapping, e.g., adjust my meter shunt resistors slightly (needles should be bang in the middle/vertical for an unmodded version with original hold control), review all published voltages (there are quite a few on the schematic) against my voltages and compare, also look into the AOT resistors and distortion patterns a bit more critically.

However, taking a break from electronics at the moment, spare time is currently allocated to other projects (e.g. practicing to get a recently composed finger picking piece to performance level proficiency, building a parlour guitar form and managing my little private viticultural research project (it is spring here)).

I will get back to it anon.