Can I use my old Valvestate Amp as a Cab only? (Updated Pics of 30 Year Old "Roadworn" Amp)

Bellycaster · December 2022

I want something I can leave in the rehearsal room and I don't want to leave my main cab in there.

Here is a pic of the back connectors. I'd guess what to do with one connector (female to female coupler), but 2 connectors? There are 2 of those speakers. Yes, they are shite, but they'll do for rehearsal.

I don't know the Ohms either? Or how I'd work it out with 2 speakers.

https://i.imgur.com/9BFErWW.jpg

https://i.imgur.com/I7V9qJb.jpg

https://i.imgur.com/ATrfT2r.jpg

https://i.imgur.com/Wm5GRlm.jpg

https://i.imgur.com/lSpQtAH.jpg

https://i.imgur.com/2kqqo1g.jpg

https://i.imgur.com/Ujq0on2.jpg

https://i.imgur.com/Ws3RoRW.jpg

https://i.imgur.com/gceY14o.jpg

https://i.imgur.com/0UCIbT2.jpg

Another daft question: If using combo as a cab, I take it would be unwise to have the combo accidentally switched ON as well as the amp head I am using also being on.

Thanks.

ICBM · December 2022

G12T-75s aren’t shite! They’re not everyone’s favourite, but they’re a decent enough modern-sounding speaker, a bit hollow in the mids and buzzy at the top end, but not terrible.

You *must* fully disconnect the amp from the speakers, not just connect the head to them as well. If there’s still any risk of powering the amp up, wrap the ends of the disconnected wires with tape - if they touch anything they could do damage to the amp. If it’s a stereo one you will need to connect the speakers to each other as well as to the cable.

The impedance should be marked on a label on the side of the magnet, or sometimes in ink (often barely legible) stamped on the speaker frame. They will be either 4-ohm or 8-ohm, I can’t remember with that amp model - 8240? - either way, it’s most likely going to be better to connect them in series not parallel. (8 ohms for two 4-ohm speakers, 16 for two 8s.) You need one extra wire for that, to connect the + of one speaker to the - of the other, with the new cable to the other two terminals.

Does that help?

LastMantra · December 2022

Don't plug the combo in!

Modulus_Amps · December 2022

Those look like push on connectors, if so I would just get a new wiring loom made up with a jack plug on one end to go into your amp.

Like ICBM said, do not leave the speakers connected to the valvestate amp, doing so could kill the amp you are playing through and kill the valvestate amp too.

ICBM · December 2022

Modulus_Amps said:

Those look like push on connectors, if so I would just get a new wiring loom made up with a jack plug on one end to go into your amp.

I forgot to say that if you’re linking the speakers in series, the new cable must have much longer ‘tails’ than normal, since they have to go one to each speaker, not both to the same one.

Modulus_Amps said:

Like ICBM said, do not leave the speakers connected to the valvestate amp, doing so could kill the amp you are playing through and kill the valvestate amp too.

Yes, I’ve seen this happen a few times. The usual cause is when a combo has a jack on the back marked ‘extension speaker’, and someone plugs a head into that thinking that it’s for using the combo *as* an extension speaker. The external amp is then trying to drive the power transistors backwards, which will quite often fry them and the resulting short then blows the valves or power transistors in the external head as well.

Bellycaster · December 2022

ICBM said:

G12T-75s aren’t shite! They’re not everyone’s favourite, but they’re a decent enough modern-sounding speaker, a bit hollow in the mids and buzzy at the top end, but not terrible.

You *must* fully disconnect the amp from the speakers, not just connect the head to them as well. If there’s still any risk of powering the amp up, wrap the ends of the disconnected wires with tape - if they touch anything they could do damage to the amp. If it’s a stereo one you will need to connect the speakers to each other as well as to the cable.

The impedance should be marked on a label on the side of the magnet, or sometimes in ink (often barely legible) stamped on the speaker frame. They will be either 4-ohm or 8-ohm, I can’t remember with that amp model - 8240? - either way, it’s most likely going to be better to connect them in series not parallel. (8 ohms for two 4-ohm speakers, 16 for two 8s.) You need one extra wire for that, to connect the + of one speaker to the - of the other, with the new cable to the other two terminals.

Does that help?

Thanks @ICBM @LastMantra and @Modulus_Amps ;

I understand some of that, particularly masking the metal jacks of the input cables, but the bit in Bold? What Cable do you mean? Just for reference, the video below is about as much as I can comprehend, but sadly my amp makes things more complicated

I have found out that the Speakers are 4 Ohms. I will put more pics in the O.P for reference to additional questions I have on here.

It does sound a bit of a headache to do the Cab "conversion" unless it's explained in the simplest possible terms. However, I was pleasantly surprised to find out that this Amp works a lot better than I expected it to and sounds really rather great. I may just take it down next time and run with it as it is.

Question regarding it's FX Loop. I never used it at all when I used it regularly waaaaay back in the 90's. I am used to only seeing one "return" input. Which input would I use as I would like to use the FX Loop as well when rehearsing.

Thanks.

Bellycaster · December 2022

Just as a matter of interest, is the "Valve" underneath that Silver Cover on the back? Is it a 12AX7?

ICBM · December 2022

Bellycaster said:

I understand some of that, particularly masking the metal jacks of the input cables, but the bit in Bold? What Cable do you mean?

The new cable with the plug on the other end that you will connect to the separate head.

If the speakers are 4-ohm you will definitely need to connect them in series - to give 8 ohms - since parallel will give a 2-ohm total.

Bellycaster said:

It does sound a bit of a headache to do the Cab "conversion" unless it's explained in the simplest possible terms. However, I was pleasantly surprised to find out that this Amp works a lot better than I expected it to and sounds really rather great. I may just take it down next time and run with it as it is.

They aren't bad at all. An amusing trick is to turn the chorus on but set the depth and rate to zero - that gives a huge, 'automatic double tracked' sound which is great for hard rock and metal

.

The 'conversion' is really simple though - remove all four push-connectors from the speakers, and the power cable from the amp

. Connect a new cable with a 1/4" plug on one end and push-connector 'tails' on the other to the + terminal of one speaker and the - terminal of the other. Connect the other + and - to each other with a wire. That's it.

Bellycaster said:

Question regarding its FX Loop. I never used it at all when I used it regularly waaaaay back in the 90's. I am used to only seeing one "return" input. Which input would I use as I would like to use the FX Loop as well when rehearsing.

Use the left/mono return.

Bellycaster said:

Just as a matter of interest, is the "Valve" underneath that Silver Cover on the back? Is it a 12AX7?

No, that's the power transformer. The valve (12AX7/ECC83) is in a socket on the PCB inside.

Bellycaster · December 2022

This below:

The 'conversion' is really simple though - remove all four push-connectors from the speakers, and the power cable from the amp

. Connect a new cable with a 1/4" plug on one end and push-connector 'tails' on the other to the + terminal of one speaker and the - terminal of the other. Connect the other + and - to each other with a wire. That's it.

Thanks @ICBM , I know it's painful, but I am struggling with this. Put simply, I can see two cables per speaker (one red, one black) that can be disconnected by hand. I can also see red and black push in connector cables that plug into the reverb tank.

I don't know what else to say, I'm totally confused. What is the "New Cable"? What goes into the 1/4 plug end?

I would actually need to see this being done with my own eyes. No offence to you, I just cannot absorb it, I just don't understand the terminology. You might be over estimating my understanding. I need an Idiot Proof demo, I'm afraid.

ICBM · December 2022

Bellycaster said:

Thanks @ICBM , I know it's painful, but I am struggling with this. Put simply, I can see two cables per speaker (one red, one black) that can be disconnected by hand. I can also see red and black push in connector cables that plug into the reverb tank.

I don't know what else to say, I'm totally confused. What is the "New Cable"? What goes into the 1/4 plug end?

I would actually need to see this being done with my own eyes. No offence to you, I just cannot absorb it, I just don't understand the terminology. You might be over estimating my understanding. I need an Idiot Proof demo, I'm afraid.

New cable - something like this:

https://www.designacable.com/guitar-head-to-cab-cable-jack-to-spades-speaker-lead-neutrik-np2x-to-faston.html

You will need it at least 50cm long if the head is going to sit on the combo, and with the speaker connection tails much longer (20cm each should do) since the speaker terminals are about 30cm apart and one needs to go to each speaker.

You also need a single wire about 40cm long with a similar ‘Faston’ connector on each end to link the other two speaker terminals together.

Designacable allow you to custom spec the cables - I don’t know if they would do a plain speaker link wire, but I can’t see why not if you contact them.

Don’t remove the reverb cables. The only things in the combo you need undo are the four wires on the speakers.

Bellycaster · December 2022

Thanks @ICBM It's a bit clearer now. Just to confirm, the cable in the link you sent. The 1/4 jack end goes to the 4 Ohm output of my Amp head? Or would it be the 8 Ohms output as there are 2 speakers?

Then the Blue and Brown wires of the cable in the in the link goes to one of the spade connectors of each speaker? But which connector to which, does blue go to a + on one speaker and brown go to the - on the other speaker?

The additional single faston ended wire would then link to the two remaining spade connectors on the speakers?

Then wrap the loose ends of the Amp's wires in tape to avoid shorting?

Just for clarity, the Amp's speaker wires, is it Red for + and Black for - on each speaker?

Don't know what I was thinking with the cables that go into the Reverb Tank. I don't think I realised it was the Reverb Tank to start with and thought those cables were somehow linked to "plugging in the speakers".

That video of Colin I posted, a lot of single speaker combos have a cable like that to connect the amp part with the speaker part and I thought that those cables on mine did something similar.

Just out of curiosity, what are those cables actually for? I don't know how a reverb tank works or why one says "in" and the other "out". It also looks like there are marker pen symbols or letters drawn on?

Thanks for taking the time.

ICBM · December 2022

Bellycaster said:

Thanks @ICBM It's a bit clearer now. Just to confirm, the cable in the link you sent. The 1/4 jack end goes to the 4 Ohm output of my Amp head? Or would it be the 8 Ohms output as there are 2 speakers?

Then the Blue and Brown wires of the cable in the in the link goes to one of the spade connectors of each speaker? But which connector to which, does blue go to a + on one speaker and brown go to the - on the other speaker?

The additional single faston ended wire would then link to the two remaining spade connectors on the speakers?

8 ohm. 2x 4 ohms in series is 8.

Brown to + on one speaker, blue to - on the other speaker (doesn’t matter which way round), extra wire between the other + and -.

Bellycaster said:

Then wrap the loose ends of the Amp's wires in tape to avoid shorting?

Just for clarity, the Amp's speaker wires, is it Red for + and Black for - on each speaker?

That video of Colin I posted, a lot of single speaker combos have a cable like that to connect the amp part with the speaker part and I thought that those cables on mine did something similar.

Red for + and black for - with the original wires on each speaker.

Don’t bother taping them if you don’t want the faff, it’s more effective to simply remove the power cable from the amp to make sure it doesn’t get switched on.

Many amps do have a plug on the back to connect the speakers, others (especially cheaper ones and where it’s not expected that you might use a different cabinet) have them hardwired like yours.

Bellycaster said:

Don't know what I was thinking with the cables that go into the Reverb Tank. I don't think I realised it was the Reverb Tank to start with and thought those cables were somehow linked to "plugging in the speakers".

Just out of curiosity, what are those cables actually for? I don't know how a reverb tank works or why one says "in" and the other "out". It also looks like there are marker pen symbols or letters drawn on?

They carry the signal to and from the reverb tank, a bit like an effect pedal in a loop. They need to be the right way round, which is why they’re marked.

I know all this seems very basic to me, but remember there are no stupid questions when you know nothing about any of this, and don’t be afraid to ask… stupid is doing something like plugging a head into a combo ‘extension speaker’ socket *without* asking anyone if that’s the right thing to do

.

Bellycaster · December 2022

Thanks for that explanation @ICBM I won't have the power lead anywhere near the Amp let alone plugged into it

I'll get onto Designacable and send them the info. I am gonna use the amp as it is to start with though. Next rehearsal definitely. I'm even tempted to gig it to give it a run out, it sounds very good and for bloody 30 years old. I will want a cable though, just in case the amp part goes Kaput and then I can run it as a passive Cab.

If I recall, the chassis is pretty straight forward to take out, the screws on the top. Just in case the valve ever needs replacing or to clean the pots.

Only one problem with the amp is that the Effects Loop isn't working with it set up like you said, and that's the way I set it up for my other amps, so it should work. I've tried the mixing effects knob and nothing happens, I had the loop set on 0Db, so should have been fine. The -20dB setting didn't work either.

The Manual states for the effects mix knob: Note - if no effects processor in line, Effects Mix full clockwise will result in no signal.

I'm not sure what they mean by that, but I am running 2 Strymon Pedals which are connected properly.

Thanks.

rossi · December 2022

I have done this on an old Peavey Back stage with a 10 in it .I just disconected the amps speaker spade connectors and made a new speaker to RCA jack .Obviously dont plug the amp in when I connect it .

Bellycaster · January 2023

Just another question regarding the single faston to faston wire.

Does it need to be Speaker Cable spec or Instrument Cable spec. I'm in email discussion with the guy currently @ICBM ;

ICBM · January 2023

Bellycaster said:

Just another question regarding the single faston to faston wire.

Does it need to be Speaker Cable spec or Instrument Cable spec. I'm in email discussion with the guy currently @ICBM ;

Neither - a single (covered) wire. Almost any gauge above about 22 will do, he will have something suitable.

Bellycaster · January 2023

ICBM said:

Bellycaster said:

Just another question regarding the single faston to faston wire.

Does it need to be Speaker Cable spec or Instrument Cable spec. I'm in email discussion with the guy currently @ICBM ;

Neither - a single (covered) wire. Almost any gauge above about 22 will do, he will have something suitable.

Thanks @ICBM I guess he'll know what that means. I'm almost quoting word for word from this thread in my email

Bellycaster · July 2023

The Valvestate did it's first Gig in 29 years last night and performed well and sounded fantastic.

I don't miss carrying the Bastard thing though.

I'll no doubt go back to the Laney for the most part but it was a good itch to scratch just getting the Marshall out there. It gets used for rehearsal every week as well.

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Can I use my old Valvestate Amp as a Cab only? (Updated Pics of 30 Year Old "Roadworn" Amp)

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