your thought on this please . single GZ34 vs 2 x EZ81 parralell for preamp duty

What is your current draw?, posted on July 21, 2014 at 05:35:52
Chip647 Audiophile Posts: 2652 Location: The South Joined: December 24, 2012	If it is low enough, don't count out 6X5GT (including the Bendix Red Bank version 5852) Or the 5Y3 and the 6106 Bendix version. I generally pick a rectifier that matches about 50% to 75% of the load rating. Pulling 25mA from a 5AR4 that can handle 250mA is not a condition I would select.

RE: What is your current draw?, posted on July 21, 2014 at 06:25:55
lovetube Dealer Posts: 3008 Location: Melbourne Australia Joined: June 8, 2003	hi C. it draw around 25ma . LT

RE: What is your current draw?, posted on July 21, 2014 at 06:50:34
Thomas Mayer Manufacturer Posts: 602 Joined: May 8, 2001	Hi! Why double rectifiers for a mere 25mA? Any of these will work nicely: 6X4, 6X5, 6AX5, 6BY5. Or a pair of 6AX4, 6DE4, 6DQ4 if you want to be fancy A single EZ81 should do nicely too. Best regards Thomas

RE: your thought on this please . single GZ34 vs 2 x EZ81 parralell for preamp duty, posted on July 21, 2014 at 06:55:18

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

From my experiences listening in 2013, with high mu tubes as would be used in a preamp ( but in my case, an amp ) I would DEFINITELY avoid paralleling sections.

Use one high powered dual rectifier tube.

I like "directly heated" ones, and would FIRST try a new production JJ 5U4G in that rectifier spot !! PSUD2 it. Possibly listen to a higher Z 5R4 with a bigger drop of B+. No paralleling of rectifiers with high mu tubes, skewed the sonics to my ears, screwed up diction and enunciation slightly, and others who did similar tests concur.

Use a big SINGLE rectifier tube and a BIG high current rated power transformer.

'Ever look at a 1970's ARC SP3 power trannie, which has stood the test of time? No tiny dude, like a Dynaco PAS-3 at all. The 1970s ARC D-75 power trannie was about 8 Ohms DCR on its HV winding too !!! William Z KNEW !! Everyone skrimps and barely gets by !! They, I"M"HO, do not understand !!

Jeff Medwin

Are you sure about that total current draw?, posted on July 21, 2014 at 07:39:34
FenderLover	25mA seems awfully low. Even for a simple gain stage unit.

RE: your thought on this please . single GZ34 vs 2 x EZ81 parralell for preamp duty, posted on July 21, 2014 at 13:19:48
Salectric Audiophile Posts: 1358 Location: East Coast Joined: February 23, 2003	For preamp with 25ma draw, I would use a 5R4GY preferably a RCA brown base.

RE: What is your current draw?, posted on July 21, 2014 at 17:39:28
lovetube Dealer Posts: 3008 Location: Melbourne Australia Joined: June 8, 2003	Thanks Thomas. the reason I thinking of using two rectifiers in paralell is to lower they impedance therefore lower impedance of the PSU LT

Get some European mesh plate rectifiers for a preamp, posted on July 22, 2014 at 03:55:57
andy evans Audiophile Posts: 4382 Joined: October 20, 2000	AZ1 and all the other mesh plate European models have the edge over anything to my ears. Yes - they cost more. But often you can hear a difference in a nice way. It gets less audible when you pile on the shunt regs, chokes, glow tubes and so on but there's a difference to start with which can still show through depending on the system. Since they're the best, I just fit them and forget it.

RE: What is your current draw?, posted on July 22, 2014 at 08:51:42

Thomas Mayer
Manufacturer

Posts: 602
Joined: May 8, 2001

Hi!

How much the impedance matters also heavily depends on the actual preamp circuit itself and also on the PSU scheme: full wave CT, full wave bridge, choke input cap input, etc. In my experience you won't gain a lot by doubling the rectifiers if anything at all. Over the years I went the other way and I got tremendously good sound results with high impedance power supplies others would laugh at.

Some of the TV dampers listed have very low impedances. There or others even lower, for example 6CG3, 6CJ3 are approaching the numbers of MV tubes.

If the impedance of the rectifier worries you, use solid state diodes,or a regulated PSU

Best regards

Thomas

Can you provide more info?, posted on July 22, 2014 at 10:26:40
Lew Audiophile Posts: 10912 Location: Bethesda, Maryland Joined: December 11, 2000	For example, what "common" tube rectifier (e.g., 5U4, 5V4, etc) roughly corresponds to what "European mesh plate" rectifier in terms of voltage drop, filament voltage, and current capacity? I've got a phono stage with tube rectification, and I'd be willing to try a mesh plate type. I think I've got a 5V4 in there right now, and I like it very much.

Should be on the web, but here's some pointers, posted on July 22, 2014 at 11:22:06
andy evans Audiophile Posts: 4382 Joined: October 20, 2000	Look up these: RGN1064 RGN1054 RGN2004 AZ1 AZ4 AZ11 AZ12 Some of these are very expensive now - basically for collectors. You'll probably get best deals on the AZ11. Needs to be mesh.

RE: your thought on this please . single GZ34 vs 2 x EZ81 parralell for preamp duty, posted on July 22, 2014 at 16:28:21
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Nice sounding in that application, +1. JM

I agree with this, posted on July 23, 2014 at 15:29:04

Ray Moth
Audiophile

Posts: 2784
Location: Jakarta, Indonesia
Joined: November 10, 2003

"Over the years I went the other way and I got tremendously good sound results with high impedance power supplies others would laugh at."

Maybe some others, but by no means all would laugh; not everyone on these forums is of the "Low PSU Impedance" persuasion. These things need to be seen in perspective. A low current preamp, whatever Mu its tube(s) may have, is not going to give one iota of improved fidelity by feeding it from an "industrial strength" power supply.

I've even found slight improvement when going from an EZ81 to an EZ80 in one low-current preamp's PSU. It seems to be a matter of "horses for courses" IME.

info, posted on July 24, 2014 at 08:01:47

Jim Dowdy
Manufacturer

Posts: 1518
Location: Atlanta, GA
Joined: July 22, 2000

Lew:

Emission Labs currently manufactures the AZ4 mesh-plate rectifier - this link contains info on that tube, plus some basic info on some of the others mentioned by Andy.

http://www.emissionlabs.com/datasheets/EML-AZ4.htm

6CJ3, posted on July 25, 2014 at 13:56:15

Mike C
Audiophile

Posts: 1074
Location: Essex
Joined: November 23, 2000

Work out your current draw and look up the voltage drop of a GZ34 and a 6CJ3 (and EZ81 and others). In a typical preamp the 6CJ3 will drop a whole lot less voltage .. typically 5v or so I guess.
So the dynamic voltage drop with varying load current will be very low with a 6CJ3. Combine this with a highly over spec mains TX and low DCR chokes and you'll have a robust, powerful, dynamic PSU with no need for active voltage regulation (and unreg sounds sweeter to my ears).

Only drawbacks are, you need 2 6cj3's i.l.o. 1 GZ34; and it needs a highish current 6.3v supply. But then again, 6CJ3's are cheap (and sound very good indeed!), whereas a metal base GZ34 costs hundreds of UK pounds ....

Ditto ..., posted on July 29, 2014 at 23:24:08
Naz Audiophile Posts: 2184 Location: Sydney Joined: September 2, 2005	The quality of tube itself compared to its peers more often makes way more difference IME. In this instance, Mullard D Getter 50's EZ81 sound glorious (regardless of internal resistance) but Mullard may suck in another tube variety. Naz

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your thought on this please . single GZ34 vs 2 x EZ81 parralell for preamp duty

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