VOX T-100 Cabinet

[BassmanPaul]

The VOX AC30TB is arguably one of the best guitar amps ever made. My heart gives a little leap whenever I see one on stage.

It’s surprising just how loud four EL84s can get with a common 50Ω resistor in their cathodes

 

[Bassman 63]

I run the amp section of my AC-30 thru the T-100 cab for recording. I think is sounds great .

 

[dbase]

Then most likely this was a North American name. it surely wasn’t used in the UK. The T indicated Transistor and was only used for the T60 in the UK. The T60 amplifier was implemented using Germanium transistors and was prone to thermal runaway. The outputs were OC28 IIRC.

From what I understand the amp went into oscillation and would over-drive the output stage.. It would then overheat and sound like crap.. I was 18 at the time and didn't understand what was going on with it... My temporary remedy was putting a box fan behind it.

 

[Bflat]

the output stage is almost identical to the Standel output circuit as I remember it , but it sure doesn't sound the same.

 

[Bassman 63]

Does anyone know the watt rating of the T 1109 15 inch speakers that comes in the T-100 cab? Thanks

 

[BogeyBass]

Supposed to be 50 watts. From what ive read. Hence the reason VOX used 2x15 to handle the AC100 power. The 12" /15" t60 only handled 50 watts. And the t100 supposed to handle 100watts with 2 50 watt drivers.

Assuming at frequencies below 100hz the real world fart out distortion factor is most likely 20/30 ish watts

But the voicecoil thermal rating is 50 watts

 

[BogeyBass]

Yea my t 60 sounded pretty bad, and the transistors blew but it is a driver transformer design, so it is pretty easy to use 2n2955s and change 2 resistors and shes back up and running and still sounding pretty bad.

Lol that was good one.

But that sounds pretty cool switching out old transistors. But 2955 ? PNP?

Is it PNP output stage or NPN

Then most likely this was a North American name. it surely wasn’t used in the UK. The T indicated Transistor and was only used for the T60 in the UK. The T60 amplifier was implemented using Germanium transistors and was prone to thermal runaway. The outputs were OC28 IIRC.

Its interesting amp and i always liked its apperance. It was unfortunate that it had thermal issues. Seems like it shouldnt cause i thought it was pretty cool design with pretty generous heatsinks and each transistor i believe mounted to seperate heatsink. Guess more of a design issue than actual devices. Transistors were rather new at the time so guess they had iron out some things.

 

[Bassman 63]

Thanks for the information! My speakers read 12.6 ohms but I think they are supposed to be 15 ohms according to what I could find out.

 

[Bflat]

PNP, just change the base emitter resistor to up the bias for the difference in germanium and silicon. there seems to be a data sheet for the oc28 that is pnp and npn......but the schematic says pnp for the t 60 and viscount......its been 20 years so I really don't remember which one I used. so if the voltage is positive on the collector use npn and if its neg use 2n2955

 

[pie_man_25]

Then most likely this was a North American name. it surely wasn’t used in the UK. The T indicated Transistor and was only used for the T60 in the UK. The T60 amplifier was implemented using Germanium transistors and was prone to thermal runaway. The outputs were OC28 IIRC.

It seems at the time that germanium transistors were the thing to use at the time but they're not so common now. I find that interesting, and will have to do some reading on it, though I imagine the reasoning is as much economical as it is practical and logistical.

 

[BassmanPaul]

At the time that the T60 came out silicon transistors were few. Germanium were pretty much the only choice, poor though they were.

 

[BassmanPaul]

One of my first introductions to transistors was in the telephone industry. My job was to commission exchange equipment. One little circuit comprised of a triple Darlington, made up of three ACY17 germanium transistors, and a relay. The relay was supposed to operate when the line condition changed. Problem was that the relay would always be seized. I traced the problem to the first ACY17 leaking so much that it switched on the second and third and the relay operated. I sent in a suggestion to head office to use Silicon devices which was accepted and I was supplied with a whole bunch of BFX30 replacements. Once changed the circuit worked perfectly I’m pleased to report.

I am amazed that I still remember the device names as my memory is variable. I have a pot full of old transistors that I brought over to Canada with me. I’ll bet there are some of both these devices in there. LOL the stuff we keep - just in case!

 

[Bassman 63]

 

[Doombuggy68]

I had a AC100 and a T100 cab, it looked cool but that is about all I got out of it, I got the cab empty and loaded it with 300 watt Eminence speakers and at low vols it was ok but if you used it live the cab would rattle like hell and fart out. this was before the internet so information was scarce when it came to knowing the right speaker acoustics and math. the T60 and T100 were tiny cabs to be squeezing that much speaker in, they prob would work for guitar cabs, I think Peter Green used them. The AC100 head cab was pretty small also, I would occasionally blow a fuse. I had a 71 Marshal Super Bass head that I should have kept it sounded great lol I always like the AC30 for bass but it wasn't loud enough plus I was afraid Id blow the speakers, i currently have an AC15 and it sounds great for bass but it wouldn't work in a live situation.

 

[BassmanPaul]

Did you do the math to select the drivers you loaded into the cabinet? Doing so would allow the thing to work at it's best whatever it's best is. VOX never did make a decent bass amp, they were pretty much all speakers in a box with no attempt at proper design.

 

[Doombuggy68]

Did you do the math to select the drivers you loaded into the cabinet? Doing so would allow the thing to work at it's best whatever it's best is. VOX never did make a decent bass amp, they were pretty much all speakers in a box with no attempt at proper design.

haha no I was young and didnt know anything about that and didnt have any way of looking for the information.

 

[purplehearted]

I started recently a thread about my T60 cabinet: Vox T60 cabinet sounds horrible

They sure look great but soundwise it's a big challenge to have them sound good (given you play with a band). I play mine with an VOX AC50 from 1965.
Right now I'll stick to my Foundation Cab, with modern speaker (forget which one), but it sounds way more balanced than the T60 cab.
I intend on experimenting a bit, perhaps remove the 12inch speaker and cover the baffle hole.

 

[Doombuggy68]

I tried playing a Hofner bass with my AC100 ran through a T100 cab and I dont know how the hell McCartney made that set up work. Vox must have tinkered with his amp and cab. At one show, I tried to use my Hofner Beatle bass and it was howling with feedback and the cab was rattling like crazy, sounded terrible, totally uncontrollable at stage volume. the Vox worked a little better with a Rickenbacker bass but it was a major disappointment. the AC100 head was blowing fuses later on, they were bad about over heating, its a lot of amp to be crammed in a small box. I sold a 70's Marshall Super Bass and regretted getting the Vox.

 

[John Sankalis]

I had a T-100 cab from North Coast, and didn't like the back rattling and huffing. Sold it, and built one. It's roughly the same size as the 215 cab JohnK built (Starliner?). Loaded with KappaLites. Very nice cab! IMO of course! I like the tight sound, and gentle low end roll off.

I've another in the works that will actually "look" like the Vox, with grill cloth, rounder corners and chrome trolley. I'll also make the matching head box... The Quilter BB800 should fit nicely in it! ;-)

 

[John Sankalis]

Saw you were going to build a copy of the T100. Did you ever build it? Can you tell me what the actual angle on the baffle/grill frame is! Thanks!

John