Vox tube advice thread inadvertently deleted

[tboy]

Well, I guess I fumble-fingered that one pretty good.

A new member (who's name escapes me, sorry) had requested tube advice for a vintage AC30, and soundmasterg posted a reply. If either of you guys wants to re-post on that subject, by all means feel free

[shuv2000]

Hello Again,

I wrote the original post...

I was asking for advice on tube replacement for an orignal VOX 67' TOP BOOST AC30 which is primarily used for recording in our studio.


Thanks!

[Alf]

Is this what you want ?

Q. What valve types should I have in my AC30?

A. There have been several different design variation of AC30 over the decades and the valve types have changed accordingly, but the traditional valve line-up in the original and the latest AC30 design is:

Vib/Trem channel input valve - ECC83
Vib/Trem LFO valve - ECC83
Vib/Trem modulator valve - ECC82
Normal & Brilliant channel input valve - ECC83
Bass/Treble control valve - ECC83
Final pre-amp phase-spliter valve 6 - ECC83
All four Power amp valves - EL84
PSU rectifier valve - GZ34

The standard AC30's made during the late 1980's used ECC83 valves for the entire pre-amp section. The AC30 Limited Edition and Vintage models made by Rose Morris during 1990 -1992 had the following valve line up:

Valve 1 : Vib/Trem LFO valve - ECC83
Valve 2 : Vib/Trem channel input valve - ECC83
Valve 3 : Vib/Trem modulator valve - ECC82
Valve 4 : Normal & Brilliant channel input valve - ECC83
Valve 5 : Bass/Treble control valve - ECC81
Valve 6 : Final pre-amp phase-spliter - ECC83
All four Power amp valves - EL84

The Vintage model with reverb (1991 - 1992) had two additional valves for the reverb section:

Reverb tray driver valve - ECC81
Reverb tray receiver valve - ECC83

Alf

[shuv2000]

Hi Alf,

Thanks for your response.

I really appreciate your answer, very informative.

I guess I would also like to know if replacing some tubes with another type (then the ones you metionned) would give us an even better tone?
We're definately going after the best possible tone, so if you have any other suggestions to make, please do so.
If using the tubes you mentionned, what brand would you recommend?

Kind Regards

[soundmasterg]

I replied to the previous one with a decent post on tube recommendations, but I guess you didn't get to read it before it was lost. For an AC30, the tube choice makes a huge difference in the sound because of the lack of negative feedback in the amp.

I've found the best sound for the power tubes comes from using some good NOS GE, Tungsram, Mullard, Valvo, etc EL84's. They're more spendy, but they last longer. I got a quad of NOS GE EL84/6BQ5's from Angela Instruments for a reasonable price a couple months back. I plan to use these only in the studio. For the rest of the time, I use EI EL84's in my AC30 and they sound very similar to the GE's, but don't last as long. EI stopped making tubes in August and what they were making for a year or so had been suspect anyway. They were having trouble getting some of the specialized metals used in tubes and so weren't coating the plates like in years past, and the tubes didn't perform as well. Anything pre-war (Balkan War) is fine. Anything post-war, especially in the last couple years, is suspect. Aside from EI, most of the modern production stuff for EL84's sounds dark and uninspiring, but the other brands are usually more reliable than the EI's have been. If it was me, and for the use you plan, I'd spend the money and find some good NOS EL84s.

For preamp tubes, there are a lot of good choices in 12AX7 types these days. I've had good luck with the Sovtek 12AX7LPS, JJ ECC83S, JJ ECC803S, EH 12AX7, Groove Tubes 12AX7M, and some of the chinese 12AX7 types are pretty good too. Pre-war EI 12AX7's sound the best of new production if you get one that isn't microphonic, which can be a problem with these. The best overall mix of sound and quality with today's 12AX7 types that I've seen has been the new Tung-Sol 12AX7 that is made in Russia. These so far have been extremely good and remind me of a 60's GE like they put in all the Fenders. I haven't tried these yet in my Vox because I have a great sounding set of pre-war EI's in it.

For NOS, if you have the money there are some great deals out there for preamp tubes. Telefunken 12AX7's/ECC83's have a premium price, but they have the most detail and the most balanced sound ever from any I've heard. They last ridiculously long too. Mullard 12AX7's/ECC83's have a great reputation too, and I like the ones I've heard. Amperex 12AX7's/ECC83's are also very nice, in addition to Brimar, Valvo, Tungsram, Siemens, old Tesla. The US stuff can sound good, but sometimes are not as sweet as the Euro stuff. Good US brands were RCA, GE, Sylvania, Tung-Sol, and some others.

You can get the NOS tubes from good dealers. There are plenty around. Angela Instuments like I mentioned is one. Lord Valve has a good rep, as does Jim McShane. You can also try stuff from places like Antique Electronics.

[shuv2000]

What a great answer!
Couldn't have hoped for a better one, thanks for taking the time...

I'll definately look into some NOS tubes.


Kind Regards