Why have capacitors improved so much over the years?

 rather then risk the problems with high maintenance mercury vapor diodes and the isolation transformers for their cathodes that have to be pre-heated and could short circuit.


Have you ever used Mercury vapor Diodes? I don't seem to have any problems with them shorting out,  only the initial preheating is time consuming, after they have been in circuit and the initial 30 minute preheating is accomplished you only preheat for 30 seconds to 1 minute.

@bdp24 They were two of a kind; however, Roger designed circuits requiring perfectly matched output tubes such as he provided for my friend's RM9 amp.  Luckily, the tubes also run conservatively and have an extended lifespan (10,000 hours?).

but…..i have had both my Modjeski RM-4 and RM-9 apart and there are a few very excellent back in the day boutique caps and R in the right places. Engineering Economics is a class some loathe but others can exploit.

one thing to very carefully consider for all the backyard coupling cap replacer chasers…. Does the musical signal at that point in the circuit have enough voltage to form that big bad cap ?  

Roger designed circuits requiring perfectly matched output tubes

This may be more marketing than fact. Matching to 5% is really hard and does not last much after the tube is put in service. 10% is considered pretty darned good. Industry standard used to be 20-25%.

@ieales Roger Modjeski moved the standard..see RAM tubes, early computerized curve tracing, many variables tested, etc..

Miss him