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When it doesn't fit anywhere else
 #133588  by easytoslip
 Mon Oct 28, 2013 4:26 pm
Thinking about switching out the stock tubes in my 5w Bugera amp with better ones, as was suggested when I got the amp. I know nothing about tubes, don't expect I'll have trouble with the mechanics of replacing them, but am not sure where to look for the actual tubes. Buy in a set, yes, I got that far.

eta: Looking for a warm, rich, chimey tone and I run a Les Paul Standard into it.
 #133642  by mgbills
 Tue Oct 29, 2013 8:02 pm

No affiliation. Nice selection typically of new & NOS. If you want some nice hard-working and tested tubes those with the Mesa Boogie brand are tested to work in their amps. They seem to be reliable and pleasant sounding on a consistent basis for general purpose.

Lot's of variability in new tubes. I hear good things about JJ's.
 #133659  by tigerstrat
 Wed Oct 30, 2013 7:26 am
I've yet to be very impressed by JJ.

What tubes are in the amp now and what model is it?
 #133666  by caspersvapors
 Wed Oct 30, 2013 10:17 am is the shit, plus if you email the guy he'll probably hit you back with some suggestions

what kind of tubes are in the amp?
 #134038  by tcsned
 Sun Nov 10, 2013 6:42 pm
easytoslip wrote:not sure how I'd find out what kind are in the amp now, pop off the front cover I guess? this is the amp
eta: it doesn't look like the Fender amps I've seen, open and hollow in back, no front cover to pop off that I can see
1 EL84 (power amp tube)
1 12AX7 (preamp tube)

It's good that there's just one power amp tube so there's no need for a matched set.
 #134042  by FretfulDave
 Sun Nov 10, 2013 7:53 pm
tcsned wrote: 1 EL84 (power amp tube)
1 12AX7 (preamp tube)

It's good that there's just one power amp tube so there's no need for a matched set.
what tcsned said . 1 x 12AX7 preamp tube and 1 x EL84 power amp tube. Buying tubes in pairs or quads is for amps that have two or four power tubes. Preamp tubes would not come in pairs and the reason for buying the power amp tubes in pairs or quads is to have the vendor test them and select 2 or 4 with very close operating characteristics as that they sound and work the best for the amp. Not the case with your amp but if you ever get into a 30 watt or larger amp, you would run into that.

From the picture of the back of the amp, the tubes are likely hanging upside down from the amp section housed in the top of the amp. With the back being pretty open, you could just tip the amp down on it's face and look in there and pull out and put in different tubes.

As far as the actual brand of tubes, you will likely find (if you bought it new) that they are Bugera "brand" tubes. This means the tubes are rebranded (i.e., they pay the manufactuere to put the amp company's name on the tubes). There really are only a handful of manufacturers out there. In this case, a poke around on the web seems to indicate that the tubes are re-branded Sovteks. Not sure which exact Sovtek preamp tube it would be as there are long plate, wide plate and plain old plate, i..e, there are Sovtek 12AX7-WA, -WB, -WC, etc. that all have varying charcteristics such as gain and microphonics. Those preamp tubes would really be a try it and see type of thing. And there are other brands as well. Preamp tubes are genearlly are not too expensive.

I had a Peavey Classic 30 with multiple preamp and power tubes. They were all Sovtek, which btw a lot of companies ship as stock tubes now and they seemed to drive into distortion or breakup too early for me. I wanted to "tame" the amp and make it cleaner. So I read about Steve Kimock's tone and ways he achieved it. Turns out he used a slightly different tube in one of his preamps stages. You only have one stage so your selection will be based on what you are trying to achieve.

The preamp tubes that can fit in your amp are of a family with the same pin arrangements and physical electrical characteristics but with different gain capabilities. An abridged rundown is:

12AX7 - 100% gain
5751 - 90% gain
12AT7 - 70% gain

and there are others.

I swapped a preamp tube on the clean channel to a Phillips 5751 and was amazed at how the amp cleaned up, the distortion was gone and the tone had a clear, bell like tone to it. That mellowed a bit as the tube changes I made settled in but still very clean and very clear. I did lose a bit of gain as is to be expected. But the difference in clarity and, for me, the percieved headroom was well worth it. It was a relatively expensive preamp tube but there are other brands that aren't so bad.

I would try a 5751 or a 12AT7 before heading down the power tube swapping thing, but that is just me and I'm sure there are others that would approach the situation differently.

Whatever approach you take, best of luck.


 #134228  by easytoslip
 Sun Nov 17, 2013 4:19 pm
any pluses or minuses to those with 70%gain versus 100% gain that you listed, Fretful Dave; I'm curious specifically on the gain part

and I'm betting I can research those three plus those suggested before your post to see what kind of sound they intend to produce
 #134231  by FretfulDave
 Sun Nov 17, 2013 7:45 pm

I have to apologize and correct my previous statement.

12AX7 = 100%
5751 = 70%
12AT7 = 60%
there are lesser gain models also

I am no tube expert, just trying to help out. Your amp is a single stage, class "A" amp. Simply a preamp tube driving into a power amp tube... fairly direct. I have read that a 12AX7 tube signal can easily drive the EL84 tube to full power. If the signal or power level going into the power tube is more than nominal the tube will start to breakup or distort. If you reduce the amount of gain, and thus the signal output to the power tube, the EL84 should not get to full power (saturation point?) and stay cleaner. Different power tubes should have different saturation levels and some reviews would probably cover that. I also read that 12AT7s aren't particulary good in the gain stages of preamps. I have normally seen them in reverb circuits or the phase inverter portion of a class "A/B" amp. Neither of these things do you have in your amp.

Here is a starter link for your tube review research:

I have seen a lot on the web where the schematics for your brand of amp are not freely available on the web. So from that it is difficult to tell where the volume control is, i.e. on the preamp with power tube running 100% all the time or on the power section with the preamp tube running 100% all the time. I likely am getting way over my head here with what I am talking about and would love it if some others would chip in and try to clear some of this up.

Anyway, love the level you are at with the Sk*ll F*ck emblem. Back in the day I had a tie dye tee-shirt with that emblem that I picked up at a show, my only one ever, and I wore the thing to rags. Cut out the emblem and it is still somewhere around the house.

Things were simpler back in the 70s. Back then I was simply a dirty hippie commie pinko fag. :-D Didn't have to deal with all this Internet stuff. :smile:


 #134446  by easytoslip
 Mon Nov 25, 2013 11:30 pm
all good Dave, I do tons of research before I'm in action, was just something I had in my mind as I'm looking to make small improvements on the electric setup. Definitely not the easiest stuff to comprehend. And yeah, this whole new online era gets mindblowing at times. Was just expressing similar stuff in my job search, used to be just send a resume, get a call, interview and you're in, now I've got to skip backwards counting in Arabic with a thumb in my left ear or some shit like that. Trying like hell to keep life simple as possible over here.

ah, that link looks like a great resource! muchas gracias. Tiff