What would be a suitable 2x12 extn cab for a Vox AD120VTX Valvetronix 2x12 stereo combo?

Voxman

The 'Blue' AD120VTX is a 2x12, 2 x 60w stereo modelling amp.  There are 2 extension cab outs - 'Left' 8 Ohm & 'Right' 8 Ohm.  

The matching 2x12 extension cab is the AD212.  This has 2 x 8 Ohm (left & right) inputs, plus a single 16 Ohm & single 4 Ohm input.  To optimise both channels/power sections of the stereo AD120VTX you connect both 8 Ohm 'outs' to both 8 Ohm 'ins' of the AD212, and change the impedance selector on the amp from 8 ohm to 16 Ohm.  

However, the AD212 is no longer made, they are harder to find used than rocking horse droppings, and they are expensive.

So, if someone had the AD120VTX and was looking to buy an alternative 2 x 12 extension cab, the problem is that most cabs only have a single 8 Ohm, 16 Ohm or 4 Ohm 'out'.  If you connected the 8 Ohm extn cab input to ONE of the 8 Ohm outs from the amp, you'll only be utilising a single channel of the amp, not both.  

1. Are there other extn cabs out there that have 2 x 8 Ohm inputs?  
2. If not, is there a way to safely connect an extn cab to both the 8 Ohm left AND 8 Ohm right extn cab 'outs' of the AD120VTX so that both channels/power sections are being fully utilised? If so
(a) how eg 'Y speaker cable'?, and
(b) what input options do you need on the extn cab eg 8 Ohm or 16 Ohm?

As always, thanks guys.

NOTE:

Just seen specs for a Harley Benton 2x12 cab that has 2 inputs for 2 x 60w stereo at 16 Ohm.  Would this do the job ie with both the AD120VTX and HB cab set at 16 Ohms?  

ICBM

Not quite, although it will work - it won't be optimum because the total impedance will be 24 ohms per channel - the extension speakers are in series with the internal ones. It will be safe, but the amp will be a little low on power, by about a third. Whether that matters with a 120W amp...

The extension cab will also take 2/3 of the power, so it may seem louder than the combo, especially as the HB has V30s.

Given how cheap the HB is and that you can sell V30s easily, you could always swap them for 8-ohm speakers.

Forgot to say - important - no, do not connect both outputs to the same mono speaker cab, at all. That's possibly dangerous to the amp if the two stereo signals are significantly different.

Voxman

Thanks @ICBM - do you  (or anyone else here on FB) know of any extn cabs around with 2 x 8 Ohm inputs that would be suitable to give full power?   

(btw - I already have the AD212 extn cab so don't have this problem - this is to try & help another AD120VTX owner )

ICBM

I can't think of any with two 8-ohm speakers and stereo inputs - all the stereo cabs I know of are 2x16-ohm, and all the 16-ohm cabs are mono… there may be some but they will most likely be cheap things designed for solid-state amps, to give 4 ohms in mono.

The HB will be fine. The volume loss from running at 24 ohms as opposed to 16 is negligible - no more than about 1dB - and you really won't notice with such efficient speakers as V30s in the extension cab.

Voxman

Thanks @ICBM - that's exactly what I've told the guy.  

The other option that he's thinking of doing, is to buy a second AD120VTX or AD120VT 2x12 combo, which can still be found reasonably easily & cheaply.  

Both 'Blue' Valvetronix' amps can be controlled from his VC12 floor controller (its specifically designed to do that with an ethernet connector for a second amp). With this he could either replicate the same patches in both amps or do the 'two amps at once' thing where one amp might be Blackface plus compressor, and the other amp might be Bassman plus tubeOD etc! Or he could mix effects eg have one amp with chorus, the other with rotary etc etc.  Endless possibilities there!

It also means he has an instant back-up amp should any problems arise with one of the amps. Downside is the extra weight, but he's a young guy so I don't think that worries him. 

ICBM

Just to be clear, make sure to tell him that if he gets the HB, he needs to be absolutely sure it isn't set to Mono when he's using it - unlike things like the Marshall 1936, it doesn't automatically switch to separate inputs when you connect to both jacks.

Voxman

ICBM said:

Just to be clear, make sure to tell him that if he gets the HB, he needs to be absolutely sure it isn't set to Mono when he's using it - unlike things like the Marshall 1936, it doesn't automatically switch to separate inputs when you connect to both jacks.

Thanks for that - those HB cabs seem incredible value!! - Thomann's are selling the G212 Vintage with VC30's for £186 inclusive of VAT & free shipping!  The VC30's alone retail at around £90 each!!  How wrong can you go - & how do they do it? 

Presumably the cabs are decent (and they're even made with plywood not MDF) and they have proper VC30's?   

ICBM

Voxman said:

ICBM said:

Just to be clear, make sure to tell him that if he gets the HB, he needs to be absolutely sure it isn't set to Mono when he's using it - unlike things like the Marshall 1936, it doesn't automatically switch to separate inputs when you connect to both jacks.

Thanks for that - those HB cabs seem incredible value!! - Thomann's are selling the G212 Vintage with VC30's for £186 inclusive of VAT & free shipping!  The VC30's alone retail at around £90 each!!  How wrong can you go - & how do they do it? 

Presumably the cabs are decent (and they're even made with plywood not MDF) and they have proper VC30's?   

Yes. It's because there is no middleman at all - Thomann buy directly from the factory in China. It wouldn't surprise me if it's next door to the Celestion factory either.

The speakers are real V30s, and the cabs are decent-quality ply. I have seen a couple where the finishing is a little rough round the back - gaps in the vinyl - and the jacks aren't the best quality, but for the price, does it really matter?

Voxman

ICBM said:

Voxman said:

ICBM said:

Just to be clear, make sure to tell him that if he gets the HB, he needs to be absolutely sure it isn't set to Mono when he's using it - unlike things like the Marshall 1936, it doesn't automatically switch to separate inputs when you connect to both jacks.

Thanks for that - those HB cabs seem incredible value!! - Thomann's are selling the G212 Vintage with VC30's for £186 inclusive of VAT & free shipping!  The VC30's alone retail at around £90 each!!  How wrong can you go - & how do they do it? 

Presumably the cabs are decent (and they're even made with plywood not MDF) and they have proper VC30's?   

Yes. It's because there is no middleman at all - Thomann buy directly from the factory in China. It wouldn't surprise me if it's next door to the Celestion factory either.

The speakers are real V30s, and the cabs are decent-quality ply. I have seen a couple where the finishing is a little rough round the back - gaps in the vinyl - and the jacks aren't the best quality, but for the price, does it really matter?

Not at all!  You know what, for that price I'm thinking of getting myself one to use with my Marshall DSL401, Laney VC30, and/or Laney Cub 12R!