Amp shopping

rob · Post by **rob** » Sun Apr 30, 2006 6:28 pm

Bill,

I live in Western New York and I think Jackson Music is a heck of a store. Do you go there often? I haven't been there in a while. I sure hate window shopping in a toy store without the extra green, if you know what I mean.

stubby · Post by **stubby** » Tue May 09, 2006 3:43 pm

No, I don't go there often, it's pretty out of my way (a couple of hours from my home and over the border). I've only been 4 or 5 times. I agree with you, great gear, good guys - knowledgeable, friendly, and helpful. A very nice store all around.

stubby · Post by **stubby** » Tue May 09, 2006 3:46 pm

No, I don't go there often, it's pretty out of the way for me (a couple of hours from my home and over the border). I've only been 4 or 5 times. I agree about the place though, great gear, good guys-knowledgeable, friendly, and helpful. A nice store all around.

stubby · Post by **stubby** » Tue May 09, 2006 3:46 pm

Sorry for the double post!

brammy · Post by **brammy** » Sun Dec 17, 2006 11:14 am

The AC-15 discussion goes back to last spring, but what the hell...

First of all, I am NOT a tube expert at all. Also I do realize that the subject of amp tubes is huge and neverending.

I have a vintage AC15 (blue alnico speaker) and have tried various tubes. The ones I seem to come back to are the JJ brand EL84 power tubes (two) and 12AX7 (aka ECC83S) preamp tubes (five). They seem to have the clean, sweet, warm tone that I like and they are reasonably priced.

Does anyone have any other suggestions for AC15 tubes?

And how important is it to have 'matched' tubes for the power and first two preamp tubes?

jnbass · Post by **jnbass** » Sun Dec 17, 2006 11:37 am

fwiw

matched output tubes are usually essential if you have a fixed bias circuit.

I like Valve Art KT66, reissue Tung-Sol 6550, EH 7868, KT88, Svetlana 6550, 6L6.

I do not have an amp that uses EL84's but I likee JJ-when you can find 'em.

sharkboy · Post by **sharkboy** » Sun Dec 17, 2006 12:57 pm

I have a strong preference for Ei EL84s. The JJ's behave a lot more like a 6V6 for my tastes (softer and darker.) I managed to obtain some Chinese EL84s that are very nice. I'm currently using these in a DC30 clone and generally only using the EF86 channel. I also like Ei 12AX7 tubes in preamps that use them, but Tung Sol reissues are nice. I want to try JJ's ecc803 tubes to see if they are bright enough for my tastes

chrisb · Post by **chrisb** » Sun Dec 17, 2006 7:01 pm

I like the Ei tubes also for EL84s in my Korg AC15TBX (which I love).

My understanding is that matched tubes are not at all necessary in class A amps since each tube handles the entire waveform.

soundmasterg · Post by **soundmasterg** » Sun Dec 17, 2006 7:52 pm

I too like the EI power tubes and preamp tubes for my AC30. There is no need to match preamp tubes. In the Ac30, the power tubes all share a common cathode bias resistor, and all the tubes set their own bias level in relation to that, and in relation to each other. Because of this, it is a good idea to use matched power tubes in a Vox AC30 so that you don't have one tube trying to swing more than the others. It will reduce hum and crossover distortion, and make the amp sound richer overall if you use matched power tubes. The AC15 is the same idea, but only two tubes share the common bias resistor, so you only get two matched power tubes.

There is a bad misconception out there about the AC30 in that it is class A. It is completely NOT TRUE! I'll refer you to Randall Aiken's excellent article about it, (link below) but the big reason it is not Class A is because the voltages are too high. If you tried to make it Class A at the voltages the power tubes run at, they would burn up. It is Class A at very low volumes like most amps, but as the amp is turned up, it goes clearly into Class AB. Many people think that an amp that is cathode biased is Class A, but the bias method and the Class the amp is biased into are completely different things. The AC30 is a hot biased, push-pull Class AB amp. Further, the bulk of guitar amps ever made are not Class A. The only ones that are for sure are single ended things like the Fender Champ, the THD Univalve, the Epiphone Valve Junior, etc. Read the article.

http://www.aikenamps.com/VoxAC30classA_2.html

sharkboy · Post by **sharkboy** » Sun Dec 17, 2006 7:55 pm

"My understanding is that matched tubes are not at all necessary in class A amps since each tube handles the entire waveform."

That isn't necessarily true. "Class A" doesn't have a lot of meaning in guitar amplifiers, since most don't stay in "class A" when the output tubes distort. Also, that isn't quite true for a push-pull amp, (referred to as class a) like a Vox AC30 or AC15- those do and would benefit from matched output tubes and possibly even from having matched triodes in the inverter.

If you are talking about a single-ended, class A amp, that would be more correct, since each tube is expressing the entirety of the wave form. Even so, there may be a compelling reason to go with matched tubes to avoid blurring (or to go with unmatched tubes to encourage it.)

sharkboy · Post by **sharkboy** » Sun Dec 17, 2006 7:57 pm

Heh. Greg's got it exactly right.

brammy · Post by **brammy** » Sun Dec 17, 2006 9:45 pm

I think I'll experiment with a set of Ei power and see how they compare to the JJ's. Getting matched pairs only costs a few $ more so I'll get them ... needed or not, it will make my non-tube-savvy conscience feel more at ease.

soundmasterg · Post by **soundmasterg** » Mon Dec 18, 2006 10:37 am

The one thing I didn't mention about the EI stuff is that EI stopped making tubes in August. Apparently they were having trouble getting metal supplies, which is the story I heard. Anyway, the pre Balkan war EI stuff is superior to the new stuff because they have the correct coatings on the metals inside the tubes whereas some of the later ones did not. The newer ones will still work, but they won't perform as well without the added things. Some of the dealers around sell pre Balkan war EI's but they are drying up. It was more of an issue with their preamp tube offerings than their power tube ones. If you can't find any good EI's, then go with NOS. I had good results shopping with Angela.com for a quad of NOS GE's for my AC30 for studio use. The rest of the time I'm using pre-war EI's. Other NOS brands are great too. Valvo, Mullard, Telefunken, Amperex, Brimar, RFT, Tungsram, etc are all great and way better than new manufacture, but of course they cost more, and it is hard to impossible to match NOS stuff nowadays.

I guess I beat you to it by a couple minutes Mark!

sharkboy · Post by **sharkboy** » Mon Dec 18, 2006 4:49 pm

Well, Greg, you're a bit quicker upstairs, so it would stand to reason that you'd beat me to the punch.

I'm a huge fan of Ei's. I have yet to have a failure, and I always have at least some Ei tubes in play at all times- some of them are even recent. I think most of my 12AX7s are of the grey plate variety, though, not the silver ones that are more prone to difficulties.

One bit about Ei was that they were sold in August through the government divesting itself of its industries (the government hadn't been putting any money into the company in a long time and so they couldn't pay for metals and power at the factory.)

I just managed to get some Shuguang EL84s and I'm pretty impressed so far, so I am up to two brands I like. I'll let you know when I get some TADs and plug them in (they use a bigger bottle with a ruggedized version of the tube inside and it is manufactured by Shuguang.) I have found in the DC30 clone that my matched JJ EL84s and unmatched EH EL84s do not sound anywhere near as good.

soundmasterg · Post by **soundmasterg** » Mon Dec 18, 2006 5:22 pm

Thats good to hear about the Shuguang EL84's. Do they have as much top end chime and aggressiveness as the EI's Mark? The JJ and EH EL84's are reliable but thats all.

Also, any idea who bought EI and if they're going to go back to making tubes? They used old Telefunken equipment so if they weren't going to still make tubes, maybe someone like Mike Matthews from New Sensor could buy the equipment and use them on his stuff.