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GZ34 in Deluxe Reverb

 
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Muttcaster



Joined: 03 Sep 2006
Posts: 130
Location: New Mexico

PostPosted: Sat May 17, 2008 9:16 pm    Post subject: GZ34 in Deluxe Reverb Reply with quote

I was poking around in my SFDR and found a Fender brand GZ34 in the rectifier position. According to this:
http://acruhl.freeshell.org/mga/main/rectifiers.html
that's a bad idea.

I should get a 5U4GB in there ASAP?

If so, anyone have one for sale?

The DR is my "down at the barn amp" and I don't use it a whole lot, but I do want to take care of it.
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Drake



Joined: 22 Aug 2006
Posts: 89
Location: California

PostPosted: Sun May 18, 2008 1:51 am    Post subject: Reply with quote

it's not necessarily bad - it depends on the resulting B+. 6V6 tubes generally don't last with the higher voltage GZ34, but if they are JJs then you might be alright. Switching in the GB will lower the B+, requiring you to re-bias the amp, which isn't a big deal for a tinkerer like you.

If it were my amp, I'd probably switch rectifiers.


Last edited by Drake on Sun May 18, 2008 2:38 pm; edited 1 time in total
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Doc62049
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PostPosted: Sun May 18, 2008 2:19 am    Post subject: How Many? Reply with quote

5U4GB's do you want?
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Muttcaster



Joined: 03 Sep 2006
Posts: 130
Location: New Mexico

PostPosted: Sun May 18, 2008 3:01 am    Post subject: Reply with quote

Drake- they are JJ's. I think you pointed out the rectifier tube when I asked you about the amp. I'll get a 5U4GB on hand and then re-bias. That's partly why I bought the thing anyway, right? To learn about them.

Good to hear from ya, BTW!
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Muttcaster



Joined: 03 Sep 2006
Posts: 130
Location: New Mexico

PostPosted: Sun May 18, 2008 3:02 am    Post subject: Re: How Many? Reply with quote

Doc62049 wrote:
5U4GB's do you want?


I just need 1.

Whatchya got?
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Doc62049
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PostPosted: Sun May 18, 2008 4:09 am    Post subject: 5u4gb Reply with quote

Check your PM box.
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Muttcaster



Joined: 03 Sep 2006
Posts: 130
Location: New Mexico

PostPosted: Thu May 29, 2008 1:29 pm    Post subject: Reply with quote

Amp update- 54UGB's arrived and I installed one. Upon checking the bias pot in the amp, I found that it was turned almost all the way "hot". Hot was 2 pm, and the pot was set at 12. I played around with the setting, using my ear and quickly found that 6 pm was too thin, brittle, and lackluster. 9 sounded really good and after trying 8 and 10, we settled on 9.

Previously the amp was so "hot" that it started breaking up around volume = 2-3 and was nearly unuseable at 5-6. The distortion was just ugly and not really very musical at all. At anything past volume = 3, the bass was so farty that I had to set the bass at 1-2. It just really wasn't a very pleasant amp, at least not for the sounds I want.

With the bias at 9, it sounds great at volume =3. Very clean and responsive, dripping with harmonics, and with a totally usable volume level. I can run the bass at 3-4 and it's powerful but not farty. Vol = 5-6 is where there serious breakup occurs, but it's so much more musical now and the actual volume of the amp isn't so obnoxious.

Overall, it's sounding MUCH better. Many thanks to Doc for helping me out.
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Silverface



Joined: 23 Aug 2006
Posts: 324
Location: Hermosa Beach CA

PostPosted: Fri May 30, 2008 12:34 am    Post subject: Reply with quote

Quote:
I found that it was turned almost all the way "hot". Hot was 2 pm, and the pot was set at 12.


How could you know? How do you know hot is "2" since it will vary depending on the output tubes?

Setting bias by ear in DR is a sure-fire way to lose you output tubes, and maybe a cap or two and the OT just for fun.

The DR is running 6V6's over spec already - that's one reason they were kind of under the radar until a few years ago when something OTHER than the roman-candle EH/Sovtek 6V6's ( which were simply Sovtek 5881 servo tubes...not even a real 6L6...that didn't pass 6L6 tests, hence the blacked-out glass so no one could tell without breaking one.)or expensive NOS tubes were available. You either bought expensive tubes and knew how to use them, or bought cheap ones and broke them and your amp.

A "sweet spot" bias-wise on a DR can often be right on the edge of disaster, and it's imperative to at least know you're in the "safe zone" for the JJ's. T bare minimum I'd use one of the $25 bias gadgets you can find on eBay and a digital multimeter - then you can see 1) were you are, and 2 whether or not your output stages are balanced. If they are not, then you try a new driver tube first - hopefully it was just unbalance. But if the bias is off more than 5ma or so either the tubes are off match or there's something amiss in the phase inverter.

Better would be an Allesandro Bias and Matching Meter or a Weber Bias Rite. The "all in one" nature of those makes them worth it, since it only takes a few minutes to check/set the bias.

The bigger 6L6 amps - Supers, Pros, Twins, Vibroverbs - can be biased by ear if you're careful (but it's still prudent to check things for the health of the amp); but a DR just runs those 6V6's too hot to take a chance that way (and I'd NEVER even think about it with a GZ34!).
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telemetric



Joined: 19 Oct 2006
Posts: 38
Location: seattle

PostPosted: Sat Feb 28, 2009 7:48 am    Post subject: gz34 Reply with quote

My drip edge Silverface Deluxe Reverb has the GZ34 on the tube chart.
No real problems here.
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