type 83 rectification OK? for kit 6550

[Thenice]

Hello everyone
I was going through a couple of sites
when l came across a 5Z3 substitute or equivalent called the 83 it is a Mercury vapor
design with a 15 voltage drop hence l wonder if it could used in a kit 6550 safely the price is reasonable
Thoughts anyone
When not sure always ask
Thanks to all who reply in advance

Frank

[John Caswell]

Hi Frank,
Well certainly a 5Z3 is fine as the 5U4 is a direct equivalent but in an International Octal base.
Personally I would steer clear of Mercury vapour rectifiers, they can be a bit electrically noisy.
If you are not worried about the top cap situation then you could use a couple of 6D22S which are bomb proof pretty much and dirt cheap to boot (providing you don't opt for the very expensive Mullard/Philips/Telefunken EY500 equivalent)

John

[Thenice]

Thanks John
for replying you basically answered my question but the itch persists sorry
Is the extra voltage a good ldea or a bad one for the amp
l am aware of the more elegant approach of the svets 6d22 but l have
several pairs of rca slyvania 5Z3 with adapters and they seem to work well
as you've said the price of 5u4g is crazy especially if it's a sil
Iy English gec valve let alone w electric
Once again thanks for replying

Frank Robinson
If there's anything l missed please pass it on

[John Caswell]

Hi Frank,
Not sure I understand the "extra voltage" comments.
If you have been using the 5U4 then as the 5Z3 is the same valve but different base then the HT voltage will be similar if not identical.

John

[Richard]

Hi John, Frank,

I read it that Frank actually has Type 83 mercury rectifiers which are electrically different to 5U4 and 5Z3 vacuum rectifiers.

The voltage drop he refers to is 15v when the others are around 40v or 50v, similar to this chart,
https://300guitars.com/articles/rect...ge-drop-chart/

I’ve swapped rectifiers such as GZ34 GZ37 5U4 5R4 5U3C (and valves to ss which gave around 50v HT increase) and yes they sound different. I think it will be due to regulation and voltage drop. Providing any extra voltage doesn’t exceed safe limits you may like or not the sound of the stiffer regulation and higher HT Frank. I did using ss in the WAD 300B pp monoblocs but others who tried it weren’t so keen


Edit, re-reading it perhaps Frank will confirm which rects he actually has...

[Thenice]

Hello Richard
I was just asking if the type 83 was a good idea (and safe) for the kit6550
I've never used Mercury vapor valves l mainly use 5U4G svets and at times 5Z3 with adapters for over 20 hours
or more rca slyvania it's hard sometimes to say um you not sure
Thanks for replying on the voltage drop question l think as a idea l leave it there
better safe then sorry
As for valves l used to hold squat gigs 30 + parties really l got to know, musicians who used
valves and play records and tapes yet record with 3 Mike's with a Sony 14/16 Adc box
on to a beta max vcr l loved sound of records through a 4 x 12 pa l the digital l began to
see as a scrubbing brush Best lightly applied but really good but the analogue could be really rough yet it was the same session well that was 1990 l never thought then that a pa could
sound so good it got to be rubbish huh then l was introduced to the wonderful mystery of military connectors well that's another story those big yellow 3 pins things [was it 2as well]
Thanks for answering, my question if there's more to add please let me know
Best wishes
Frank

[Richard]

Hi Frank,

To the 5U4 and 5Z3 you can add the 5X4 as also being identical except for its base, here’s the Tung-Sol data sheet which lumps them all together,

https://frank.pocnet.net/sheets/127/5/5Z3.pdf

Here’s the sheet for the RCA 83 Mercury vapour,

https://frank.pocnet.net/sheets/021/8/83.pdf

Note the need for plate resistors when using 2 valves as we also mention in the FAQ for Kit6550,

http://www.world-designs.co.uk/forum...ead.php?t=3859

also the note about heating the rect before applying the load, in practice I suppose, turn on from cold and don’t flip it on and off when warmed up. (This goes for valve rects in general perhaps, I’ve had some protests from the rects when rushing valve swaps in some amps including the GZ37 in 300Bpp.)

So can you use 83 in Kit6550? Probably yes but the 6550s may not like it due to the extra voltage (less drop than 5U4). This amp already runs them at 36W. Many folk use 560R on the cathodes instead of 500R. So check that first, then add 50R or 100R to pin 4 and 6 leads of both rects which will balance the loads and drop a little HT. This may be more complicated using adaptors.

I don’t know what any extra noise will sound like or if it will be just spikes on the scope but extra HTv may make the amp a little sharper/brighter/dynamic sounding.

It may be more than that as you may lose some of the compression noted by guitarists (which I take to mean less volume on musical peaks; a softening effect). All probably quite subtle with recorded music but perhaps easy for a guitarist who knows his instrument to home in on. Let us know if you give it a go.

300b pp monoblocs ss rect swap mentioned here,

http://www.world-designs.co.uk/forum...300b+monoblocs

[Richard]

Here's a YouTube of the 83 in action


https://www.youtube.com/watch?v=3d8GKHHZW4E

[Thenice]

Richard
Thanks for your thoughtfulness and your thorough answer

You re a diamond

Best wishes

Frank