Vox ac15tb > ok with a 16ohm spkr?

[Dave H]

The first thing you have to do is to find a wire that measures low resistance to the existing speaker wires...

Edit: What Pete said

[Sea Chief]

I see what you mean.
Without a photo I have only the words of this thread to go by.
Can you post a photo or look at the three wires that go to the EL84s as the other two or hopefully three wires will tell us what is what.
If there are three wires, it has a 16 Ohm tapping.

I can only look for now. *I can see only two wires going to the el84's. One each to the same pin, on each socket. Where would a 3rd "16ohm" one go-?

The online info (using the 6 digit code) for this OT you see, is frustratingly vague to it having one or not (it has a full stop in an infuriating place causing ambiguity as to what bit of info is relating to which OT: the one 'it replaces' or the one itself/ pictured).

All I know is it has no 16ohm jack (*And only 2 wires to the el84's; but I dont think this prooves, neccessarily, that it has no 16 ohm tap.. does it?)

The implication then is: both that it -does- have one (the OT code info -might- imply this).. & that it -doesn't- have one (there are only 2 wires to el84, as you say). I think.

[vintagekiki]

A little help



http://web.archive.org/web/20061128152419/http://www.thejennifers.com/vox/ac15/chassis/

http://web.archive.org/web/20061129110758/http://www.thejennifers.com/vox/ac15/
1)
https://www.offsetguitars.com/forums/viewtopic.php?f=10&t=40631&start=15

[vintagekiki]

...And only 2 wires to the el84's; ...there are only 2 wires to el84...

The 2 wires that go to the el84's are the wires that go from the primary OT to the anode of the el84's

[Jon Snell]

If you note the UK sheet I sent regarding the original transformer wiring, Black is common, Green is 8 Ohm and Brown is 16 Ohm, or it may be (Blue).
Just swap the centre wire to the right hand terminal.

[Sea Chief]

The schematic shows 3 terminals on the OT secondary; starting from the bottom, they will typically be common, 8ohms and 16ohms. The 8ohm output will be taken from the common and 8ohm terminals. A 16ohm output would be taken from the common and 16ohm terminals.
There is the possibility that the 3 terminals are common, 4ohms and 8ohms.
If you can identify the 3rd terminal then it will be possible to work out whether it is intended to be 16 or 4ohms.
The terminals may be in the form of wires (colour coded) emerging from the OT, or as solder terminals (also referred to as 'lugs') mounted on the OT. Wire colour codes are typically specific to a manufacturer, they are not generic.
I hope that made sense?

Hi pdf.. sorry I must have missed this reply, don't know how tbh I was reloading page countless times in case a new reply ~midday.

Anyway thanks this clarifies things somewhat. But I guess I can only answer the Q now by taking the whole amp out.. which I was trying to avoid as it's a huge pain, hence asking beforehand.

I'm still not understanding where the bold additional info derives from, that Jon's diagram has, overlaid on my OT schematic info (which says/ suggests YES it has a 16ohm tap). If this could be established I might be able to determine what it very likely has without having to remove amp. And Im not sure even if I do, & find 3 terminals, how I then "identify" it. Measure it? with the amp on?

[pdf64]

Please note that Sea Chief’s amp is a Vox AC15TB.
ie http://www.voxshowroom.com/uk/amp/15tbx_hood.html
not a vintage type model.

[Sea Chief]

Please note that SeaChief’s amp is a Vox AC15TB.
ie http://www.voxshowroom.com/uk/amp/15tbx_hood.html
not a vintage type model.

Aha. I think this perhaps clears up why I'm confused by some of Jon's replies. thanks

[pdf64]

If, as per the photos in the link, the only wires emerging from the secondary side of the OT are the black and green pair, then unfortunately you could be out of luck.
Maybe there’s another wire under the transformer cover, which has been cut off rather than being brought out? But I suspect that’s going a bit deeper than you may be comfortable with.
The amp should be fine with a 16ohm speaker. For given control settings it won’t be quite as loud, and it won’t put out full power, eg may be 10W.
I suggest to avoid turn the gain and master volume up full and playing at full blast. Otherwise though, don’t worry about it.

[Sea Chief]

If, as per the photos in the link, the only wires emerging from the secondary side of the OT are the black and green pair, then unfortunately you could be out of luck.
Maybe there’s another wire under the transformer cover, which has been cut off rather than being brought out? But I suspect that’s going a bit deeper than you may be comfortable with.

(Photos in the link.. which vkk added which isn't in fact my amp-?)

Yup now I'm 100% on board with what you mean here tho. This is a small triumph for me:-) Ok so I gotta get the beast out & see.

--

You see the bigger picture pdf, is do I: whip out the vox blue (an addition if it's labelled a TB.. the TBX had the blue alnico) & put in the 16ohm 1973 vintage 30w greenback celestion instead > sell the AC15 like so (if of course I can reconfig the 16ohm tap) > & sell the vox blue separately.

Or sell as is, sell the vintage celestion alone. My next Q's if i found the 16ohm idea feasable, is how it would affect the amp/ whether this might add or detract from it's value.

I'm really struggling for income/ clobbered by the pandemic you see, so I decided last night I gotta sell all unneccesary stuff.. & I need to max my chances. I have my self built TwinRev to keep.

The vox blue I discovered today, is a china job.. so my mind made up on the sell idea now, even if it sounds extremely good I must say. 2 amps is unneccesary considering how much of a struggle it is for me to understand almost everything about them!

thx SC

[vintagekiki]

If, as per the photos in the link, the only wires emerging from the secondary side of the OT are the black and green pair, then unfortunately you could be out of luck.
Maybe there’s another wire under the transformer cover, which has been cut off rather than being brought out? But I suspect that’s going a bit deeper than you may be comfortable with.
The amp should be fine with a 16ohm speaker. For given control settings it won’t be quite as loud, and it won’t put out full power, eg may be 10W.
I suggest to avoid turn the gain and master volume up full and playing at full blast. Otherwise though, don’t worry about it.

OT vintage series amps AC15 & AC30 have 3 wires for speaker connection
- GND (connected to chassis)
- 8 ohm for (1x8 ohm or 2x16 ohm in parallel) speakers.
- 16 ohm for (1x16 ohm or 2x8 ohm in series) speakers.
The speaker connection is available when remove the wooden back side.
Speaker connection was realized over the PVC terminal strip, just behind the input jacks.

https://5.imimg.com/data5/CP/JQ/MY-37835190/strip-connector-500x500.jpg
PVC Strip Connector

[vintagekiki]

Please note that Sea Chief’s amp is a Vox AC15TB.
not a vintage type model.

A little help. Let's not wander. Let's help to friend.
Vox ac15tb chronology.
Vox ac15tb > ok with a 16ohm spkr?
Vox AC15 (TBX).. redesign?
Vox AC15 (TBX) general Q's
Vox AC15 TBX: input 1 problem

[pdf64]

(Photos in the link.. which vkk added which isn't in fact my amp-?)

Sorry for not being clear, I was referring to the AC15TB photos in the link to the AC15TB in my post, here it is again
http://www.voxshowroom.com/uk/amp/15tbx_hood.html
If your amp has a Vox Blue, isn’t it a TBX model? Or is the Blue not its original speaker?

Is there much difference in secondhand value between the Chinese Blue and your vintage Celestion?

[Sea Chief]

Sorry for not being clear, I was referring to the AC15TB photos in the link to the AC15TB in my post, here it is again
http://www.voxshowroom.com/uk/amp/15tbx_hood.html
If your amp has a Vox Blue, isn’t it a TBX model? Or is the Blue not its original speaker?

Is there much difference in secondhand value between the Chinese Blue and your vintage Celestion?

Aha sorry I missed you'd put that link up & those were the pics you were referring to, my mistake/ you were perfectly clear.

I can't be the original speaker -I think now- if the amp plate says TB, & this is effectively now a TBX (the X designating the upgraded blue spkr version). I would think, unless they whacked on wrong plate in factory, or if the TBX had the uk made celestion labelled blue, not this vox labelled blue.

I'm not sure of the value of either speakers, not the foggiest idea.. but I just had a hunch the blue might be worth a good chunk more if £215 new.

I'd certainly be grateful for anyone's opinion on value of them though.

thanks SC

[g1]

If, as per the photos in the link, the only wires emerging from the secondary side of the OT are the black and green pair, then unfortunately you could be out of luck.

Here is a photo, and it appears there is only the 2 secondary wires you mentioned, so no other tap than the one in use.
As you say, if he is not pushing the volume, it should be fine to use the 16 ohm speaker.