Favorite GZ34/5AR4

MS15X2 · Post by **MS15X2** » Fri 01/29/10 1:07 pm

Hello Good Tube People !

On the prowl for a good, reliable, toneful - ok if it's on the bright side - NOS or current, GZ34/5AR4. I can share with you that both from personal experience as well as hearing from several knowledgeable amp techs & builders is that the current JJ has a high failure rate and seems to be rather inconsistent from batch to batch. As Miles Davis said to Bach, Beethoven & Marilyn Monroe, there's no such thing as a bad note - as long as you resolve it later. Looking forward to your views. THANKS !

krx · Post by **krx** » Fri 01/29/10 2:45 pm

There's no such thing as a "toneful" or "bright" rectifier. It rectifies AC to DC, and it sags if you push it hard enough (would have to be really hard for a GZ34). There's only two questions to ask about a rectifier: does it meet specs and is it reliable?

In my opinion the JJ is just fine, especially at about 10% the cost of NOS. How many of them have failed on you? Under what operating conditions?

andreaps72 · Post by **andreaps72** » Fri 01/29/10 2:52 pm

True
Never had problems with JJ GZ34 till now, but the last 4 tubes I bought blow fuses over and over again, all 4 in several amps.

snoof · Post by **snoof** » Fri 01/29/10 2:54 pm

I've had one JJ 5ar4 go south on me, whereas others in the same amp are fine.

krx · Post by **krx** » Fri 01/29/10 3:13 pm

One thing to keep in mind is the GZ34 spec is 60uF max on the input filter. Another thing to keep in mind is that standby switches are EVIL and can and often will blow your rectifier.

If the JJs are simply built to spec rather than overbuilt like some of the old tubes, I can see how they'd have problems in circuits that don't respect the datasheet.

MadDitch · Post by **MadDitch** » Fri 01/29/10 4:21 pm

The JJ I have is about 20 volts on the low side, but the Sovtek Gz34s I have seem pretty consistent.

MS15X2 · Post by **MS15X2** » Sat 01/30/10 1:09 pm

andreaps72 wrote:True
Never had problems with JJ GZ34 till now, but the last 4 tubes I bought blow fuses over and over again, all 4 in several amps.

I'm curious as to the four amps you mention - same model, circuit design etc as well as did you put JJ's back in all four ? Distinctive sound difference ??

krx · Post by **krx** » Sat 01/30/10 2:10 pm

MS15X2 wrote:Distinctive sound difference ??

The only sound difference from different rectifiers is due to different voltages being put out. Running an amp at, say, 340 Volts will sound a little different than at 355 Volts.

MS15X2 · Post by **MS15X2** » Sat 01/30/10 2:27 pm

krx wrote:There's no such thing as a "toneful" or "bright" rectifier. It rectifies AC to DC, and it sags if you push it hard enough (would have to be really hard for a GZ34). There's only two questions to ask about a rectifier: does it meet specs and is it reliable?In my opinion the JJ is just fine, especially at about 10% the cost of NOS. How many of them have failed on you? Under what operating conditions?

Thanks for your reply. Technically I can agree with your statement regarding tone.While I don't purport to be a know-it-all - and I'm not trying to imply in any way that you are - wouldn't you agree that everything in the circuit - everything in the overall chain for that matter - affects tone ? An AC30 circuit ,for example, designed to achieve it's tone by over-driving the power tubes, is going to sound different than the same amp designed with a master volume riding herd or an amp whose" tone " center is derived from over driving the pre amp tubes. Add an EF 86 channel, Celestion Blues vs. Greenbacks vs. your choice here and everything changes again. Take an amp where ALL the variables remain constant and all you're doing is auditioning different make rectifiers and the sound will change, otherwise ALL rectifier tubes would be exactly the same and have exactly the same affect. Since we know that no two same model amps are identical, you're going to have variations. That's what I was referring to when I described it in terms of " tone " and " brightness ". Lastly, to your point regarding cost, I think a trade-off exists. As I'm sure you're aware,back when tubes ruled the electronic world and the U.S. Gov't was the biggest buyer, standards were incredibly high. Now, standards are much lower, materials have changed and the lifespan is about half that of true NOS. If the JJ runs, say $20 and through useage you replace it a couple of times a year, go through a few more until you find one that " sounds " like the one you're replacing/affects the tone the same way, what are you spending in the end ? More than a NOS ?? Everybody has a different 10% factor based on what they hear - will I spend 2x as much, 5x as much if it has a noticeable impact on tone of 10% ? 35% ? 50% ? AND might last upwards of 20-30 years ? This is all part of the fun of achieving one's own unique, individual sound. Find it, have one tube or set of tubes go down, change guitars, the sound changes and you're frustrated. Maybe that's why McCartney plays the ukelallie( acoustic, I might add ). All I'm trying to learn from others is what their experience is/has been before I end up buying one of everything. While trial and error is a lot of fun and educational, finding that certain tubes are merely rebranded X , have defects by nature or aren't worth the money is helpful. Thanks again.

andreaps72 · Post by **andreaps72** » Sat 01/30/10 2:59 pm

Where is no difference if you use Sovtek or JJ, and I can't hear difference in only 10 volt in an amplifier running at 400-450 volt.

The only differences you can hear is if you put a 5U4 (where you can due to the 3A filament instead 1,9A) in the place of an GZ34.
First for the drop of 30-40 Volt and second for the direct heating filament, a little more compressed sound.

krx · Post by **krx** » Sat 01/30/10 3:22 pm

MS15X2 wrote:An AC30 circuit ,for example, designed to achieve it's tone by over-driving the power tubes

Take an amp where ALL the variables remain constant and all you're doing is auditioning different make rectifiers and the sound will change, otherwise ALL rectifier tubes would be exactly the same and have exactly the same affect.

The AC30 was designed not to distort at all, and the early Marshalls were advertised for their clean headroom

Yes, different rectifiers (of the same model) can change the sound of the amp but this is entirely due to the different voltages they put out. These differences are very subtle. The audio signal does not pass through the rectifier. There are dozens and dozens of things that have a far more significant effect on the sound than whether you're using a JJ or an Amperex GZ34.

The average price for an NOS GZ34 from a reputable dealer is well over $100, and I can get the JJ or Sovtek for $15. If NOS "mojo" is worth that much money to you, go for it.

Post by **CurtissRobin** » Sat 01/30/10 5:38 pm

If you were to list in order of importance those things that affect the sound of an amp, the particular GZ34/5AR4 you plug in would be near the low end of the list, more important than the power cord and less important than the cabinet wood. I'll throw in with krx that changing B+ value will affect the sound but I'll add that substituting one GZ34/5AR4 for another GZ34/5AR4 is unlikely to make anybody's ears perk up, especially since Ken Fischer died. You're inflating the importance of the rectifier tube on an amp's voicing.

KennyO

krx · Post by **krx** » Sat 01/30/10 9:46 pm

CurtissRobin wrote:If you were to list in order of importance those things that affect the sound of an amp, the particular GZ34/5AR4 you plug in would be near the low end of the list, more important than the power cord and less important than the cabinet wood.

Exactly

. That doesn't stop some people from spending a few hundred bucks on a power cord though

http://www.pedalgeek.com/cgi-bin/new_sh ... k--easous5

shasen · Post by **shasen** » Sun 01/31/10 2:34 pm

krx wrote:
CurtissRobin wrote:If you were to list in order of importance those things that affect the sound of an amp, the particular GZ34/5AR4 you plug in would be near the low end of the list, more important than the power cord and less important than the cabinet wood.
>Exactly . That doesn't stop some people from spending a few hundred bucks on a power cord though

Question have these nay-sayers actually spent the $$ required to get a super Rare NOS Mullard 5AR4/GZ34 to actually hear the difference for themselves? Didn't think so

To date I've sold about 10 of these NOS Mullard 5AR4/GZ34s (Both 4 and 7 notchplate versions). They typically go for between $70-$89. Many of those customers have gone out of their way to write me to say that installing the Mullard has increased the "tightness and tone" in their amps. They mention that each note is much more clear.

My Warranty. If you don't like it, just contact me within 7 days and send it back for a refund. You pay shipping for the try-out session. No one has ever returned one of these babies. Only 2 days left to find out for yourself.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... RK:MESE:IT

krx · Post by **krx** » Sun 01/31/10 3:39 pm

No offense Shasen, but please keep your advertising to the Dealer Classified section.

krx · Post by **krx** » Sun 01/31/10 3:47 pm

shasen wrote:Question have these nay-sayers actually spent the $$ required to get a super Rare NOS Mullard 5AR4/GZ34 to actually hear the difference for themselves? Didn't think so

Have I used those tubes? Yes.

Many of those customers have gone out of their way to write me to say that installing the Mullard has increased the "tightness and tone" in their amps. They mention that each note is much more clear.

There are three possibilities here: 1. They were using a different rectifier and switching to the GZ34, which puts out a higher voltage with less sag, produced a different sound. 2. They were using a worn out or off-spec GZ34 and replacement with a new one changed the voltage and sag enough to be noticeable. 3. They spent the money and of course they subconsciously want to hear the improvement

.

There is zero science to back up claims that different brands of GZ34 affect the tone unless they are off-spec or worn out. This isn't like a 12AX7 where you can have different size plates, geometry, etc., which can affect the response at different frequencies for the audio signal which is passing through them (but does not pass through a rectifier).

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