5Y3 versus 5AR4

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solderstain
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5Y3 versus 5AR4

Post by solderstain » Wed Jun 08, 2011 4:17 am

As a departure from my recently-completed Express, I'm putting the finishing touches on a 5E3-type build into an old Gibson GA-10 (don't worry, the GA-10 had been gutted a long time ago...). The only original Gibson parts in the build are the bare steel chassis, the Gibson PT, pilot light and power switch. Oh, and the 1961 cabinet with its original tweed, but a new baffle cut for a 12" speaker (the original had a 10"). Everything else is new parts.

For the most part, I stayed true to the 5E3 signal path, except that I implemented independent volume controls. I haven't decided what kind of tone control circuit I'm going to use or if it will be on both channels or just one.

This post is about rectifier tubes. I've got a whole buncha cool old tubes, but not one 5Y3. I have more 5AR4s than I'll use in this life time, and the next two as well. I don't even remember where they all came from (old-guy disease...).

I know I can fire the thing up with a 5AR4, but is it worth buying a 5Y3 for the long run? I also don't have a 12AY7, but I do plan on getting one.

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rdjones
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Re: 5Y3 versus 5AR4

Post by rdjones » Wed Jun 08, 2011 5:18 am

The 5Y3 and 5AR4 (GZ34) are at opposite ends of the spectrum of the various pin-compatible rectifiers.
The 5Y3 has the most voltage drop and the lowest current capacity.
It's that voltage drop that creates the "sag" that amps like the 5E3 have as part of their signature sound.

The 5AR4 (and to a lesser degree the 5V4) have a much lower voltage drop at maximum signal due to their indirectly heated cathodes.
These tubes have a real, separate cathode; B+ does not flow through the filament when they are hooked up right.
HINT : always pull B+ from pin 8 regardless of which rectifier you are using.
The 5AR4 will supply a higher B+ which may exceed some component's design parameters.

Yes, get a 5Y3.

rd

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KT66
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Re: 5Y3 versus 5AR4

Post by KT66 » Wed Jun 08, 2011 6:17 am

Remember to get a vintage 5Y3 - as far as I know nobody makes a real one anymore even though some are labeled as such. There's still plenty of NOS available at reasonable prices.
Ryan

Music is the best. F.Z.

http://Classictubeamps.com

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rdjones
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Re: 5Y3 versus 5AR4

Post by rdjones » Wed Jun 08, 2011 6:32 am

KT66 wrote:Remember to get a vintage 5Y3 - as far as I know nobody makes a real one anymore even though some are labeled as such. There's still plenty of NOS available at reasonable prices.
Excellent point ! I forgot about that.
Modern Russian tubes marked as 5Y3 are built like the 5V4 with an indirectly heated cathode and will supply a higher B+ and have less 'sag'.
Easy to spot if you know what to look for.

Nobody makes a real 5Y3 ? sad if true.
I've got some NOS in my 'private stash', and yes they can be found.

rd

surfsup
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Re: 5Y3 versus 5AR4

Post by surfsup » Wed Jun 08, 2011 10:52 am

"Easy to spot if you know what to look for."

Could you elaborate? Can this connection be seen through the glass?

DR.Z
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Re: 5Y3 versus 5AR4

Post by DR.Z » Wed Jun 08, 2011 10:58 am

Hey guys try out the new JJ 5Y3.
I think you'll be pleasantly supprised.

DR.Z

solderstain
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Re: 5Y3 versus 5AR4

Post by solderstain » Wed Jun 08, 2011 2:18 pm

Thanks, guys - this is getting more interesting as people post. :D

I fired the amp up on the bench last night with generic 12AX7s up front, a pair of JJ 6V6GTs, and a Chinese 5AR4, just to hear it make some noise. I ran it through an open-back cab with an old G12-65, and a closed-back cab with a 1967 Celestion/Vox Silver Bell Alnico.

What a cool sound. It wasn't ideal with the tubes I was using, but it shows a lot of promise. The amp is going to fit nicely in with my other other amps, though I'm running out of room on my 'amp wall'. And I still have a '70s Dumble and a TW Liverpool builds on the shelf. (I know, I know... it's a sickness - the first step is admitting it...)

I'm off to shop for an old 12AY7 and 5Y3. I also need to figure out which speaker to get for the final install in the Gibson cabinet. For this amp, the Alnico speaker definitely sounded nicer than the ceramic. I think I've read good things about a black Weber Alnico, but that was a little while ago... I'll have to do my research again.

solderstain
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Re: 5Y3 versus 5AR4

Post by solderstain » Wed Jun 08, 2011 2:27 pm

rdjones wrote:...the 5V4) have a much lower voltage drop...
I like me some 5V4 for the right situation. :wink: It's what's saving my '63 AC30/TB... or more correctly, the old tubes I have in that amp.

My wall voltage can get as high as 127 VAC during low demand periods during the day, and that can jack the B+ up higher than it was ever meant to be for some old amps. I've cooked some expensive old EL84s in that amp, so, for a while, I'd play with a Variac hooked up and dialed back to about an actual 115 VAC. Someone on another forum recommended running a 5V4 in place of the GZ34, and PRESTO! With the 5V4, the voltages dropped within a volt or two of what I measured with the GZ34 and the Variac pulling things down to 115 VAC. Sometimes, juggling rectifier tubes has really paid off for me.

guitarmike2107
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Re: 5Y3 versus 5AR4

Post by guitarmike2107 » Wed Jun 08, 2011 3:14 pm

Another option is to use what you have got and insert a series flameproof power resistor after the rectifier, which will drop the voltage and introduce more sag, then you make it switchable so you have both options available

solderstain
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Re: 5Y3 versus 5AR4

Post by solderstain » Wed Jun 08, 2011 3:44 pm

guitarmike2107 wrote:Another option is to use what you have got and insert a series flameproof power resistor after the rectifier, which will drop the voltage and introduce more sag, then you make it switchable so you have both options available
Thanks for the suggestion. Anyone who has seen any of my builds knows I'm all for different tricks and tuning options, but for THIS one, I just want get it dialed in and then never touch it again. Besides, there really isn't room on the GA-10 chassis to put more switches, etc. This is one case where simpler is better, at least for me. :lol:

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rdjones
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Re: 5Y3 versus 5AR4

Post by rdjones » Wed Jun 08, 2011 6:54 pm

surfsup wrote:"Easy to spot if you know what to look for."

Could you elaborate? Can this connection be seen through the glass?
Yes, the construction can be seen through the glass unless there's excessive silvering but either the top or bottom, or both, should be visible to determine construction.

The 5Y3 (a real one) is built like a smaller version of the 5U4 with a single flat loop of filament that goes up through the middle of the plate enclosure, over the top of the support mica and back down again.
There is no separate cathode element, the filament is the cathode.

The 5AR4, 5V4 and other rectifiers that are indirectly heated have a separate cathode tube that surrounds the heater.
The heater will be a cluster of 'strings' folded together inside the tube.

rd
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surfsup
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Re: 5Y3 versus 5AR4

Post by surfsup » Wed Jun 08, 2011 11:58 pm

Rdjones thanks. I'll check me 5y3s and see whether they look like that.

solderstain
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Re: 5Y3 versus 5AR4

Post by solderstain » Thu Jun 09, 2011 4:48 am

Well, I hooked up the Variac and dialed up a steady 120 VAC and took some measurements - I've got 390 VDC on the plates of the 6V6s...

I didn't know what to really expect for voltage since I didn't remember what the Gibson PT was putting out. I was curious if I was going to be close to the 360 VDC range, which is my target, but... I'm definitely going to be picking up a 5Y3 now! :lol:

Tone Lover
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Re: 5Y3 versus 5AR4

Post by Tone Lover » Thu Jun 09, 2011 5:19 am

guitarmike2107 wrote:Another option is to use what you have got and insert a series flameproof power resistor after the rectifier, which will drop the voltage and introduce more sag, then you make it switchable so you have both options available
Would you happen to have a schematic or drawing so I could understand how you impliment this my friend.
Bill

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