AC30 CC2X tube question: Which one's for the normal channel?

[paologregorio]

Does anyone know which, if any, preamp tube is for the normal channel on the AC30 CC2X? I have what sounds like microphonic or tube noise coming out of the normal channel only on my AC 30 CC2X; the sound is only audible when the normal channel volume is on at any level-when I turn the normal channel volume all the way off the sound goes away. The Brilliant channel does not make this noise at all. I want to switch out the offending tube, if it's a tube, but I don't know which one it is. There are only three preamp tubes on the AC 30 CC2X, which is obviously quite different from the old AC30. Since there's next to zero clearance for tube access, I'd like to only have to reach in there once-with the power off, the amp unplugged, and the caps discharged, of course!

I usually use my vintage AC 30, but I might be using the CC2X again soon, and I like to use the channel combining feature at times, which means that I'd need to use the normal channel. Besides, it annoys me when my gear isn't 100%.

[sharkboy]

The CC versions of the schematic are not up on Schematicheaven.com. There is not a lot of common reference designators between the family. I'll look around some more.

You might try changing individual 12AX7s until that problem goes away or changing the lot of them.

[Razor]

The 12AX7s are the pre-amp tubes, apparently the Chinese ones that come in the AC30CCs are pants. I've read quite a bit about them and it seems they are a weak point of the CC. Most people advise changing them for better quality ones.

There's plenty about it on Harmony Central - you'll also read that in order to change the valves you need to remove the chassis - which involves disconnecting (unsoldering) the speakers - great design...

[sharkboy]

I like the Chinese 12AX7 tubes a lot, and I also like the Chinese EL84s. So far, I've seen no failures in either in my own use. Unlike a lot of the tubes sold from elsewhere, they are capable of sounding very Voxy. That said, I think the 12AX7 is not as reliable as some others.

I don't completely understand why they didn't redesign the Vox hotbox tube cooker mechanical design, but it does look "vintagey". It is also possible that some of the magic from an AC30 comes from its difficult industrial design. They may have accrued some proximity advantage in this design in keeping the tubes away from the EM field of the speakers in the combo- but that's a heckuva way to do it.

[paologregorio]

I appreciate all the tips. It apeears as though we're all a bit familiar with the CC2X in this respect, yet still equally in the dark as to which specific tube, if any, controls the normal channel.

The basic layout of the oldAC30, and the CC2X, at least to the eye, looks quite similar. The older AC 30s of course, had three separate channels, with the vibrato channels accesible only on the vibrato channel, and six inputs- a high and a low for each channel. These amps have more preamp tubes-the exact number of which escapes me at the moment, and I don't really want to go peeking inside the amp to count them . The new CC2X has 3 preamp tubes. I switched out the original Chinese tubes awhile back, as they were complete rubbish. the power amp tubes, as well as the recitifier were of Russian and Eastern European origing, respectively. The Chinese preamp tubes started making all sorts of noise within a year after purchase of the amp. I switched them out for some Groove Tubes and hadn't had any trouble with amp noise until the last time I used the CC2X.

The too short speaker wire length of hard wired speaker wire is a Vox characteristic not limited to the new CC models. My old AC 30 had this "feature" as well. I had a non shorting(?) speaker jack installed by my local amp tech on the underside of my AC30 to deal with this on my vintage AC30. On the new amp, I was unaware of the problem until I decided to change the tubes, which was when I discoverd that
(a) the new AC30s have two more screws securing the chassis tray(hidden on the UNDERSIDE of the chassis tray-"why won't the tray move"?) than the old AC30s do, and
(b) Just like the vintage AC30s, the hard wired speaker leads are too short!

I wish I'd bought my amp from North Coast Music, as they change out the lousy tubes and modify the speaker jack like so

in order to facilitate tube changes and servicing. I might do this modification myself in lieu of having a speaker jack added, but then again, a speaker jack might be a more secure option.

In any case, I was able to slide the chassis only about 1/3 to 1/2 of the way out of the chassis before I ran out of Speaker wire length(thanks Korg/Vox), but it was enough to be able to acess everything. It's going to be a complete nightmare for my amp tech. I think I'm just going to have him hard wire the whole amp when the time comes. He converts pc board amps to hand wired quite often and knows the craft well. I will definitely have the too short spekaer wire problem dealt with!

[Ric-360-12FG]

Can anyone of you experts tell me how to remove the chassis of a Vox AC30 CC1? I tried to open the amp just to have a look at the tubes and to make sure that I really know how to open it. I would like to install JJ tubes after christmas. So I removed the back plate that is held by 8 screws. After doing that I can see electronic parts but I do not see the tubes and it's not possible to pull out the chassis. It feels as if there are some more screws that still hold it in place but I don't see any. Can anybody help me? Normally I'm not that clumsy with a screwdriver...

[paologregorio]

I had the same problem with my CC2X, which I mentioned in an earlier post on this thread . Check the underside of the chassis tray; if the CC1 is fastened together the same way as a CC2, there will be two screws on each side of the underside of the chassis tray securing it to the rails. I think I turned my amp upside down for access to these...gently, of course. Once those are removed, you should be able to remove the chassis. Be careful to mind your speaker wire.

[whojamfan]

check your email Paul Feel free to pass those on to anyone who wants them.