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Twin tube rectifiers - Why?

Tom_r

Tom_r

Well-Known Member
I have a few vintage mono tube amps which use two 5Y3GT rectifiers tubes:


Bogen DB130 which will be modded per Jim's post, but here is the original schematic.

Grommes 61PG which is the integrated amp I'm listening to in my mono system. There is no schematic available.


I'm wondering, why do some amps use twin rectifiers, and do they need to be replaced in matched (ie same brand/build) pairs?
 
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The main reason is to be able to supply enough current. One 5y3 provides around 120mA. if the amp draws that...it is a little borderline.

They do not have to be matched.
 
Hi Tom -- It is typically due to a mix of engineering and marketing needs. The use of dual tubes allows for double the current capability versus that of a single tube -- giving the performance of a single larger tube from two smaller tubes. The use of two smaller tubes allows more flexibility with regards to styling profile as well.

Because rectifier tubes do not have a Gm characteristic, but rather, just a simple emission characteristic, matching is basically limited to making sure that two good tubes are installed.

I hope this helps!

Dave
 
What he said. You also get less voltage drop running dual rectifiers vs a single of the same type. Depending what exactly it is, and how things are wired you can sometimes sub the dual rectifiers with a single of another type that has a higher current rating though. This only works if they are run in parallel, as in both rectifiers are full wave. Sometimes with dual rectifiers, the plates are tied together and each is used as a halfwave rectifier and the outputs are combined to get a full wave.
 
From what I can tell, too, there was a time period in the post-WWII era, where there were apparently a LOT of 5Y3 rectifiers floating around, cheap (surplus, etc)- and a shortage of 5U4s and other similar higher-power rectifiers. It looks like some manufacturers adapted to this situation, by using dual 5Y3s, instead of a 5U4 or such.

Another case of the dual 5Y3s was by various DuMont chassis... and IIRC, Magnavox also did this, at least in a few cases.

Later, many manufacturers used dual 5U4 rectifiers, in really high-power amps. This was more common in big guitar amps, but it also was done by companies like Magnavox and others for hi-fi gear. If you've got four or six 6L6s, or eight or more 6V6s, or four 6550s to drive, that's about the only way to get enough current, barring solid-state rectifiers...

Regards,
Gordon.
 
Greatness = amps with one tube rectifier per channel. I'm thinking HH Scott 296, 340, Mac MC-30 and MC-60.
 
Lots of up sides to using two rectifiers as noted above. I cannot think of any down side.

I suspect that the driver was usually economics of one kind or another. Consider the EICO HF-81, which is basically two HF-12 mono amps in one box... right down to the two EZ81 rectifiers!

5Y3s were so plentiful in the early 1950s... that they're still plentiful!
In 2013, I think we're all happier replacing 5Y3s than 5AR4s with good NOS or even used vintage tubes! :-)

I think using two rectifiers was just the easiest (and thus cheapest, despite the higher parts count!) way to add more current capability to a design.
 
mhardy6647 said:
Lots of up sides to using two rectifiers as noted above. I cannot think of any down side.
Click to expand...

The only downside I can see is a heater current capacity on the PT. 5Y3 uses 5V@2A, so two of them will require 4A of heater current @ 5V.

5U4 OTOH, will require only 3A to provide the same HT current capacity as two 5Y3 at 4A.

Cheers, Paul.
 
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GordonW said:
From what I can tell, too, there was a time period in the post-WWII era, where there were apparently a LOT of 5Y3 rectifiers floating around, cheap (surplus, etc)- and a shortage of 5U4s and other similar higher-power rectifiers. It looks like some manufacturers adapted to this situation, by using dual 5Y3s, instead of a 5U4 or such.

Another case of the dual 5Y3s was by various DuMont chassis... and IIRC, Magnavox also did this, at least in a few cases.
Click to expand...

My EH Scott 800B uses a pair of 5Y3's. It was made in 1947 and it feeds 24 tubes with those rectifiers. Two 6L6G's for output, and the rest are all radio. Not a huge lot of B+ current outside the power amp but its a big honkin transformer in that baby.
 
radioactive said:
Well I guess that leaves out my fairchild 260's with dual 5v4's:D
Click to expand...

Or this- one of my earlier creations- originally, the chassis (DuMont) had dual 5Y3s, but I converted it over to dual 5V4s, when I made a stereo integrated amp out of it:

index.php


http://www.audiokarma.org/forums/showthread.php?t=218444

Regards,
Gordon.
 
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Oh, and I forgot my Pilot SA-260 has twin 5U4GB's. I still have to restore it but word on the street is they're a pretty good amp.
 
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