Help me re-tube my new AC15C1....

[Echoes14]

I just bought my first Vox (hooray!), an AC15C1. In my previous tube amps, I've always used the Tung Sol reissue 12ax7 for preamp tubes. Well, I finally stepped off the deep end about bought some old preamp tubes on ebay. I hedged my bet a little, though, and only spent $26 on a trio of different tubes. Here's the description:

For auction are three 12AX7 vacuum tubes with long grey ribbed plates. The manufactures of the tubes are RCA, Tung-Sol, & CBS

All three tubes were tested on a recently calibrated Hickok 539C where the minimum reading for this tube is 875gm and the reading for a new tube is 1350gm

The tubes measured as follows,

1300gm/1100gm RCA
1300gm/1300gm Tung-Sol
1400gm/1400gm CBS

So, for those with any experience with Vox and/or older tubes, do you think these would be fine to run in all three positions? Or choose two older ones for the V1 and V2, with a new Tung Sol for the PI?

Also, I've read that some EL84 power tubes "won't fit in VOX AC15 reissue". Does this hold true for the C1 version? The power tube section is pretty wide open, as far as my eyes can tell....and the base plate looks no different.

Thanks for your help!

 

[beaubrummels]

Re: Help me re-tube my new AC15C1....

Run the RCA in V1, but note long plate 12AX7s can be microphonic, more so than small plates. In an AC15, might not get loud/hot enough to cause a problem. (One of my two AC30s gets microphonic when it's hot.) You can put what you want in the other positions. The center and left ones both look like RCA to me, but who knows. Would have to really inspect it and do some research. (Tube manufacturers did so much rebranding and outsourcing it's a challenge sometimes to ID old tubes.)

I can't speak to the EL84 not fitting thing. That makes no sense to me. I haven't seen dramatic differences in EL84 sizes such that one would clear the chassis/cabinet and another wouldn't.

 

[Echoes14]

Re: Help me re-tube my new AC15C1....

This is the text from Tube Depot (this is found on EH, Mullard, Sovtek, Tung Sol, Genalex....basically all the tubes made at the Reflector factory):

Due to the larger diameter of the glass envelope, this EL84 will NOT fit in the following amplifiers:

•BadCat Model 2R
•Bad Cat Amplifier Model Black Cat
•Marshall DSL201
•Marshall DSL401
•VOX reissue AC15

 

[Myaccount876]

Re: Help me re-tube my new AC15C1....

This is the text from Tube Depot (this is found on EH, Mullard, Sovtek, Tung Sol, Genalex....basically all the tubes made at the Reflector factory):

Due to the larger diameter of the glass envelope, this EL84 will NOT fit in the following amplifiers:

•BadCat Model 2R
•Bad Cat Amplifier Model Black Cat
•Marshall DSL201
•Marshall DSL401
•VOX reissue AC15

Correct, those tubes will not fit.

As for tube arrangements, it is all trial and error. In my very honest and humble opinion though, I'm happy if the amp turns on. Were tubes better back in the day? Supposedly very much so, but it isn't worth stressing over. Just use whatever works, is available to you, and sounds best. The oldest tube may or may not sound best on V1, but I find it easier to not care unless it really sounds bad.

 

[Myaccount876]

Re: Help me re-tube my new AC15C1....

I can't speak to the EL84 not fitting thing. That makes no sense to me. I haven't seen dramatic differences in EL84 sizes such that one would clear the chassis/cabinet and another wouldn't.

The tubes have slightly larger bottles. That slight difference changes it all up.

 

[Echoes14]

Re: Help me re-tube my new AC15C1....

Correct, those tubes will not fit.

Do you have experience with that situation?

Reading different forums has only confused the situation. I found ONE post that definitively said "That refers to the 80's reissue of the AC15. The CC1 and C1 are totally new amps, and aren't considered reissues, so the tubes will work."

I sent an email to Tube Depot to try to get an answer, but no response so far.

 

[Progbusters]

Re: Help me re-tube my new AC15C1....

In my ac15c1 I just changed the V1 with the new Tung sol and it was already a big improvement. More character.

 

[Myaccount876]

Re: Help me re-tube my new AC15C1....

I don't, but I remember a few threads where people were having trouble. You could always call tube depot and ask for more clarification.

 

[Echoes14]

Re: Help me re-tube my new AC15C1....

Called Tube Depot, and they said there were some models with a "silver rim" around the socket, and said if the amp had that rim, the tubes wouldn't fit. I sent them a pic of the sockets in my AC15, which just have regular tube retainers, and they replied: "Yes...that looks like there should be room. Thanks for the pic." So, Mullard reissues for me, I guess.

 

[Myaccount876]

Re: Help me re-tube my new AC15C1....

Good news then, glad it'll work. I'm also happy to have a straight answer as to which ones will fit and which ones won't.