ART TUBE MP pre amp problem

[jay Burd]

Just pick up a "art tube mp" off use guitar center. Got it to turn on (light up) but no signal using 1/4th input or XLR. I am using a 9v DC power supply even though it calls for 9vAC because that is all i got right now. Does it make sense that I would not be getting a signal because i am using DC instead of AC? or is it something else?

-j

 

[witzendoz]

I am using a 9v DC power supply even though it calls for 9vAC because that is all i got right now. Does it make sense that I would not be getting a signal because i am using DC instead of AC? or is it something else?

-j

Well, if it's still working at all after putting the completely wrong power supply on it I would get the correct one before plugging it in again.

Alan.

 

[ecc83]

Well, if it's still working at all after putting the completely wrong power supply on it I would get the correct one before plugging it in again.

Alan.

Yes Al' he's a "lakky boy"! The 9VDC has gone thru a simple regulator to produce 5.7V which lights the LED (and is maybe heater supply?) but the rest of the circuit is a voltage multiplier which produces 48V spook juice and 33V anode (plate) volts. The pre amp is therefore a "starved plate" design and not a proper valve circuit at all.
The V multiplier will patently not work from DC because the diodes are CAPACITIVELY coupled!

WARNING TO NOOBS!!! NEVER EVER connect a power supply to a piece of kit unless you are dead, bang sure...
1) the voltage is correct for the device (buy a meter)
2) the polarity (if DC) is correct for the device. This is really even more important than being a few % wrong in voltage. (again, buy a meter)
3) check whether the device needs DC or AC!!!!! A $10 digital test meter will tell you this as well.

The CURRENT rating is often not so much of an issue and the only real danger is that you could bugger the supply. Naturally, if the device being fed is rated at 1amp (= 1000 milliamps aka mA) the supply should be at least that but a 2 amp or even bigger supply will not hurt anything.

..............Noobs! Did you get the point about BUYING A FEKKIN' METER???

Dave.

 

[mjbphotos]

Just pick up a "art tube mp" off use guitar center. Got it to turn on (light up) but no signal using 1/4th input or XLR. I am using a 9v DC power supply even though it calls for 9vAC because that is all i got right now. Does it make sense that I would not be getting a signal because i am using DC instead of AC? or is it something else?

-j

Well, you got it at GC, just bring it back for your money, an dtell them you didn't use it, decided you didn't need it anyway. I've read (here) that those ART MPs are not worth the money anyway.

 

[ecc83]

Well, you got it at GC, just bring it back for your money, an dtell them you didn't use it, decided you didn't need it anyway. I've read (here) that those ART MPs are not worth the money anyway.

Doh! It has just clicked, how come he bought a pre amp WITHOUT the proper supply? Even if GC were selling a used or B grade product it should still be complete.

In fact I suspect it is illegal to sell a product without the correct mains adaptor? "As seen" at an auction or pawn shop would be different.

Dave.

 

[ecc83]

Don't believe it's illegal (in the US) and perhaps if it is stated in the sale "No power supply included", they're covered anyhow.

or........
The sales chap at GC probably thought it took batteries

Oh well! If it's in the Wild West I guess it is ok! Good job you don't have proper lekktrik or you would be dropping like flies.

Heh!
Dave.

 

[jay Burd]

Thanks! yea it did not come with a power supply and I Didn't realize that it called for AC instead on DC. Hopefully it still works once I get an AC power supply.

 

[Tadpui]

Did you get it used? It should have come with a power supply if it was purchased new.

 

[ecc83]

From looking at the schematic it should be OK with the new power supply.
I bought a used piece of gear once from GC from their used website. They sent the wrong item and when I called the store that it came from, the manager wasn't sure how to process a return. I finally got it returned after a few phone calls. Not inclined to buy anything else used from GC.

Tis the modern disease Mark. Stores don't want to pay for any technical staff or the ability to do in house servicing. "We" could not get any guitar shops to even swap a pre amp valve that was obviously borked (white) when there was a short term problem with them arriving with cracked bases.

I bought a 22" TV from Sainsbury a few months ago and the paperwork said in effect IF it goes wrong DO NOT contact the store but the manufacturer's service agent. This is in flagrant contradiction of UK consumer law where the retailer has the first responsibility for any fault.

Mind you, consumers have brought this condition upon themselves. Like little birds going "cheep! Cheep!"

Dave.

 

[mjbphotos]

I bought a 22" TV from Sainsbury a few months ago and the paperwork said in effect IF it goes wrong DO NOT contact the store but the manufacturer's service agent. This is in flagrant contradiction of UK consumer law where the retailer has the first responsibility for any fault.

You see the same thing here for many items.