Building a mid-60's JTM45'ish amp with lots of NOS parts - which pots would you use??
Posted: Fri Sep 11, 2020 2:39 am
Hi Gang.
This forum is truly the only group of peeps that could appreciate my "dilemma" - I hope some of you old heads are still keeping an eye out here!!!!!!
I am building a 1964'ish JTM45 style amp where I have sourced all of the era correct parts - through the signal path... so the circuit board will contain all Piher resistors and Mullard mustard caps. For transformers/choke I choose George's Drake replicas (super excited about these!!!). Otherwise, F&T filtering, higher wattage vitrohm wire wounds (in filtering sections)... not sure about plate load resistors yet, and not sure about potentiometers to use....
I have an opinion these days that good tolerances of the correct parts get you 90% of the way there (or there abouts). Of course I am after that 10%!!! I have a modern 2014 Marshall JTM45 RI where I have changed the caps out to Sozo Next Gen and I have a hard time imagining a better sounding amp (yes, even with the crappy stock Dagnall Trannys). But that is what this great experiment is about. Of course however I have NEVER played the real thing.... sooooooo...
A long time ago I used PEC, but my recollection of that amp, while favorable, left my opinion rather indifferent when it came to most "upgrades" (including Mercury Magnetic trannies - from which I ended up having a tad of buyers remorse over). So I did not forgo the 15 euros (moved to Belgium about 10 years ago *sigh*) per pot this time (though I spent more per mustard cap).
In recent experiences I think that Alpha standard 24mm pots have left me with little desire to use anything else... though in many of my amp builds I have used CTS, more or less only because "that's what a high quality amp has installed". In my stash, the Alpha pots are very very close to their advertised values - 1M pot usually reads extremely close to 1M, where a CTS pot of the same value will read 850k to 900k.
AFAIK they are all made in Korea... even Bourns (which I also have).
So my immediate contenders are Alpha 24mm, CTS 24mm, Bournes HRT 24mm pots. I have not measured the Bourns yet, but the Alphas are bang on the $$$ with their tolerance.
Are there any ideas I am missing here? Or is there a supply of NOS that I am unaware of??? HEEEEEP PLEASE!! What would you do?
This forum is truly the only group of peeps that could appreciate my "dilemma" - I hope some of you old heads are still keeping an eye out here!!!!!!
I am building a 1964'ish JTM45 style amp where I have sourced all of the era correct parts - through the signal path... so the circuit board will contain all Piher resistors and Mullard mustard caps. For transformers/choke I choose George's Drake replicas (super excited about these!!!). Otherwise, F&T filtering, higher wattage vitrohm wire wounds (in filtering sections)... not sure about plate load resistors yet, and not sure about potentiometers to use....
I have an opinion these days that good tolerances of the correct parts get you 90% of the way there (or there abouts). Of course I am after that 10%!!! I have a modern 2014 Marshall JTM45 RI where I have changed the caps out to Sozo Next Gen and I have a hard time imagining a better sounding amp (yes, even with the crappy stock Dagnall Trannys). But that is what this great experiment is about. Of course however I have NEVER played the real thing.... sooooooo...
A long time ago I used PEC, but my recollection of that amp, while favorable, left my opinion rather indifferent when it came to most "upgrades" (including Mercury Magnetic trannies - from which I ended up having a tad of buyers remorse over). So I did not forgo the 15 euros (moved to Belgium about 10 years ago *sigh*) per pot this time (though I spent more per mustard cap).
In recent experiences I think that Alpha standard 24mm pots have left me with little desire to use anything else... though in many of my amp builds I have used CTS, more or less only because "that's what a high quality amp has installed". In my stash, the Alpha pots are very very close to their advertised values - 1M pot usually reads extremely close to 1M, where a CTS pot of the same value will read 850k to 900k.
AFAIK they are all made in Korea... even Bourns (which I also have).
So my immediate contenders are Alpha 24mm, CTS 24mm, Bournes HRT 24mm pots. I have not measured the Bourns yet, but the Alphas are bang on the $$$ with their tolerance.
Are there any ideas I am missing here? Or is there a supply of NOS that I am unaware of??? HEEEEEP PLEASE!! What would you do?