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Can you run a 12V pedal at 9V?


Clarky
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Electronic numpty time.

I have a bunch of 9V pedals all hooked up and daisy chained on my pedalboard but have just acquired a valve OD pedal that has a 12V power supply. I would prefer not to have two plugs coming off my pedalboard (OK, its not a massive issue but sometimes there are limited electricity points at gigs; plus its one more wire to trip over!).

What would happen if I just daisy chained the valve OD pedal? Would it be silent or underpowered or even blow? I have no idea so I thought I would ask you august folks! Cheers in advance

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If it’s a Dave Hall then you’re fine; they have a relay circuit inside that doubles the voltage, so plugging 9v in will give the tube 18v. 

They’re centre positive though, so you’d need to invert the supply.

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You may end up in trouble, if the polarity is reversed in one pedal. This may mean that the plus is in the case in two and minus in the third pedal. When you connect them with signal cables, the plus and minus are in the same metal surface and the voltage will be plain 0. Not good. Power supply doesn't like this.

You can try to connect all together with line cables and then power them up. If they turn themselves down, you need to buy a power brick with isolated outputs.

Modern power supplies usually have other than just 9 V outputs and some are close to cheap.

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On 19/07/2019 at 13:19, paul_5 said:

If it’s a Dave Hall then you’re fine; they have a relay circuit inside that doubles the voltage, so plugging 9v in will give the tube 18v. 

They’re centre positive though, so you’d need to invert the supply.

Not always. The VT1 Pro Bass Drive works off a centre neg.

I have a 2-way 13A extension socket on my pedal board, I'm not a fan of training wall wart cables across stages either.

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On 19/07/2019 at 12:59, Clarky said:

Electronic numpty time.

I have a bunch of 9V pedals all hooked up and daisy chained on my pedalboard but have just acquired a valve OD pedal that has a 12V power supply. I would prefer not to have two plugs coming off my pedalboard (OK, its not a massive issue but sometimes there are limited electricity points at gigs; plus its one more wire to trip over!).

What would happen if I just daisy chained the valve OD pedal? Would it be silent or underpowered or even blow? I have no idea so I thought I would ask you august folks! Cheers in advance

 

Valve pedals tend to have much higher requirements than usual 9V Boss type analog pedals. I'm not sure you can damage it but it's likely it will not be very good. I have had several valve pedals that I tried at different voltages. With some, I lost headroom. With others, they just didn't work, giving me faint noises. Also, it's not just the voltage, the current rating is important, probably more so than voltage alone. If your pedal required at least 120mA, and you're daisy chaining several... chances are it will not work very well.

You could fit a 2-way into your pedalboard so you can power the valve pedal separately, but still using a single plug off the board.

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If it's a 12V DHA pedal, you can run it a 9V no problem, Dave Hall himself (RIP) said so. Just make sure it has plenty of mA on tap (no idea how much it needs though) and expect slightly more breakup at lower gain levels than you would get from 12V.

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38 minutes ago, dannybuoy said:

If it's a 12V DHA pedal, you can run it a 9V no problem, Dave Hall himself (RIP) said so. Just make sure it has plenty of mA on tap (no idea how much it needs though) and expect slightly more breakup at lower gain levels than you would get from 12V.

 

Indeed. My old DHA VT-1 (I think it was the VT-1) ran ok at 9V provided the mA rating was taken into account. It was slightly (very slightly) noisier and the overdrive didn't seem as full as it was at 12V, but it was very useable and worked well.

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Numpty Q #3 - how do I know its got enough mA? I bought a basic PSU that has currently has a tuner, squelch filter (official term) and compressor daisy chained and the valve OD was going to join these 3 pedals

Edited by Clarky
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21 hours ago, Clarky said:

Numpty Q #3 - how do I know its got enough mA? I bought a basic PSU that has currently has a tuner, squelch filter (official term) and compressor daisy chained and the valve OD was going to join these 3 pedals

Output of power supply (written on the power supply)

-

(Current draw of pedal tuner + draw of filter + draw of compressor + draw of valve OD (apparently 150mA) + some taking into account a safety margin and the quality of the power supply)

!= >0

 

All of your pedals will have a current draw written on them, but this is usually a totally worst case. This list might help.

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16 minutes ago, dannybuoy said:

I've got a lot of pedals here, I don't think any of them do! It can often be found in the manual though.

Yeah you're right I think it's very variable, some of mine do and some don't.

 

Either way they're usually not very accurate. OP, you can use an ammeter and a 9v if you really want to know but to be honest even that's not accurate because (even though you can measure precisely) the pedal's draw will change depending on knob settings and playing conditions, duty cycle, blah blah.

 

There's also the indefinable 'is my psu any good?' to think about. I fully believe Strymon when they say the Ojai does 5x500mA. I'm not so sure about the far eastern sellers on ebay selling units for £6 or £7.

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