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Post by bigben55 on Mar 25, 2018 17:59:28 GMT -7
I'm about due. I'm going back to Dr Zs recommendations, which is: -Shungang 5AR4 rectifier -JJ 6V6S -Tung Sol Ri 12AX7 -Winged C EF86
I already have the Winged C in there now. The 12AX7 in it now is a nice NOS GE. I'm gonna buy a matched quad of the JJ 6V6s, the double mica ones from Eurotubes so I have spares.
In it now is a Genelex GZ34 rectifier. I'm just gonna leave it for now. My question is, after it gets new 6V6s and biased at the techs, can I just buy the Shungang 5AR4 and just plug it in, no harm no foul?
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Post by meanslide on Mar 26, 2018 12:16:48 GMT -7
I was told ( in this thread) that one would need to re-bias if changing the rectifier tube. Power tubes and rectifier: re-bias small tubes: pop in and play....no re-biasing needed. Just make sure you don't mix up the sockets...(unless you like sparks and possibly fire)
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Post by bigben55 on Mar 26, 2018 13:27:13 GMT -7
Obviously if going from ie a 5AR4 to some other recto tube. I was told if going from a NOS 5AR4 to a modern one you should rebias too, as many new production ones don't supply AS much voltage as the NOS ones do. But, going from a modern one to another modern One?
My (limited) understanding is, AC from the wall gets converted to DC by the rectifier and power transformer, and sent to the power tubes. If you have the bias perfect how you want it, and significantly change the voltage by changing rectifier tubes, you just messed up your biasing.
My question would be, is there a significant voltage difference between a Shungang and a Genelex reissue 5AR4/GZ34? And what constitutes a "significant difference"?
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Post by Christopher on Mar 27, 2018 8:38:43 GMT -7
The two different rectifiers can pull similar amounts of current but not the exact same and can alter the amount of current going to the rest of your tube compliment and that's why it's recommended to rebiasing the whole thing when changing them out. That said, I've dropped NOS GZ34s in place of current production and also put Brand X in place of Brand Y rectifiers without rebiasing without any ill effects but to be on the side you may want to have the rectifier put in with the new 6V6s so everything is kosher and on the same page. It's your amp so do as you will but don't be torqued if you red plate (too much current) or get a sterile lifeless (too little current) tone from the new power tubes bc the newer rectifier doesn't match up as closely as you assumed.
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Post by bigben55 on Mar 27, 2018 13:20:33 GMT -7
My rub is, I emailed Dr Z a while ago, got a quick response from Don Depew about tubes. He said: "Your Z28 was built in 2011 Ben, the past few years we’ve shipped Z28s with TungSol 12AX7s in V2. Also Shuguang 5AR4 rectifiers instead of the Sovtek 5AR4, the combination produces a fuller tone, increased clarity and a smoother high end. We’ve used JJ 6V6s for quite a while and are not looking to change, they continue to be the most reliable 6V6 available in addition to being part of the sound of our amps. NOS Winged C EF86s have shipped in our amps for at least the past 5 years."
So apparently the Shuguang 5AR4 makes a difference, but it's a @$20 tube and I have a known, working $40 5AR4 in it now. Buy a Shuguang, or just roll with the Gold Lion ri??? The 6V6s are ordered. Doing it all at once makes sense. Many will say rectifiers "either work or they dont. " Many will also say "Drop "$250 on a NOS Mullard, it'll outlive you!" Im not able to do that. I've experimented lots with preamp tubes and power tubes but not rectifiers.
What should I do?
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Post by daddyelmis (Greg) on Mar 27, 2018 13:32:33 GMT -7
Have you watched Doc’s AMA on rectifiers? My impression from that is that a given class of rectifier will behave properly absent some flaw in the tube. So that either 5AR4 would work fine. If you’re going to check or adjust bias because of the new 6v6s then the old rectifier won’t matter.
I’m sure that some may be able to perceive the difference between 2 same class rectifiers, but I don’t think it would jeopardize the amp.
Since the Z28 is fixed bias, you may want to (or have a tech) check/set bias with the new power tubes if in doubt.
My $0.02 (pre-tax)
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Post by bigben55 on Mar 27, 2018 16:40:38 GMT -7
Thx^. Amp will go to the tech for rebiasing, and I bought a matched quad so when these tubes get used up I won't have to take it back. I may buy the Shuguagh.
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Post by bigben55 on Mar 28, 2018 11:50:31 GMT -7
I think I'll leave the Gold Lion GZ34 in there for now, have the amp rebiased with the JJ tubes. I need another Winged C EF86 more, as I have NO spares and I know how EF86s can "go microphonic" pretty much whenever. I need a spare. And I'll buy a TungSol ri 12AX7 eventually too. I'll worry about the rectifier last. Who knows, maybe I can save up for an NOS one while that 1st pair of JJs get used up.
I do have 2 related rectifier tube questions though. Running the amp HARD wears out power tubes faster. This I know. But does it wear out rectifiers faster too? And when a rectifier fails(never had this happen to me) I understand the fuse usually blows. If I ever had a fuse blow(again never have) i would replace the recto and power tubes and fuse thru my tech. Are there other components that such a failure can damage and is that rare or common?
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Post by Christopher on Mar 28, 2018 19:07:48 GMT -7
I've had a rectifier blow once and luckily the amp had resistors to prevent the power tubes dying and the fuse blew to protect the OT. If you're unlucky it can take out the transformer and power tube section. It's not fun. Regardless, all tubes do drift after time. They are envelopes of gas with current running through them and eventually they will fail, although the old NOS types were built to last and most do. Modern production quality isn't as good but they do hold up a spell and with regards to rectifiers they are pretty stout. I've had more preamp and power tube failures from a certain brand than any others. Generally I change power tubes once/year and only do preamps when they go microphonic. Rectifiers only get changed if I want more or less squish and then only in certain amps. I have another maker's amp that I use a 5Y3 for when I want tweed and it can sub a GZ34 for headroom without biasing bc it's a single power tube based amp. It can also sub in a 6L6 in place of the 6V6 which is fun when I want a change from the thick chunk of my '28. Like Doc says in his AMA, his designs can handle some recto changes with proper biasing and within reason. If you've had the gold lion rectifier in there a while I'd leave it. A newer 5AR4 will probably tighten up the amp a bit and may sound more stiff to your ear until the new tube gets some time on it.
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Post by bigben55 on Apr 18, 2018 18:29:17 GMT -7
So I finally got the whole Dr Z recommended tube compliment in the mail and installed today, with some playtime.
Swapped a Shuguang 5AR4 in for a Gold Lion GZ34, a Tung Sol ri 12AX7 for the NOS GE/Fender 12AX7, and put a new NOS Winged C EF86 in. It got new JJ 6V6s last week.
The combo makes me like the strat thru it more than I did, the regular tele the same, and the straight in, cranked amp, no effects dual humbucker tele slightly less. This is a good thing, as the strat(1993 G&L Legacy) is my "best" guitar. It and the ASAT Classic will be this summer's gig guitars, with the pedalboard.
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