22V Power Supply died on me. Are they still available?

Discussion - HT Pedals. Heavenly Boxes.
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bordonbert
Posts: 6
Joined: Tue Jul 05, 2016 5:20 am

Mon Apr 08, 2019 10:51 am

Hi guys. I've just got may hands on a HT Dual which is turning out really well. However the PSU has just crapped out on me. It's designated ADA-006 and is labelled 22V/1.0A. At that current it may be a tad underpowered for the Dual which I have seen specd at 1.1A-1.5A. I've been searching for about 4hrs and still haven't found a simple PSU! Looking for an original one online is an impossible task and I can't even find a knockoff copy.

Does anyone know if these are still available from Blackstar? If they are not then I'm sure I can run the pedal from an iRobot Roomba 22.5V 1.25A charger. As with any PSU the voltage is the key thing to match fairly closely. As long as the supply current capability is above the unit's requirements then any supply should be fine.

As an easier alternative, has anyone tried to run the Dual from a standard 24V switched mode supply? As the pedal regenerates its own internal supply lines it may be fairly tolerant of a slightly higher input voltage.

bordonbert
Posts: 6
Joined: Tue Jul 05, 2016 5:20 am

Mon Apr 08, 2019 1:54 pm

Just an update. I've just had a nice chat with Matt in Blackstar Sales/Support. These supplies are still available from them but it sounded to me like there weren't too many knocking about. I ordered one direct from them at (£13 + £3 p&p) + VAT. It came to just over £19 in total and it should get here tomorrow courier willing! Not cheap considering the quality and size of the supply but cheap in terms of what it might be as it is a specialist item. Now I describe that as "good customer service"!

If anyone finds this during their own search for a new supply and there aren't any original supplies left then I strongly suggest you look into the iRobot Roomba option. Those are described as chargers but they are basically 22.5V 1.25A power supplies as far as we are concerned. If they don't massively "overvoltage" and supply a higher voltage level than that they should be fine. It is worth noting that some poorer designs of switched mode supplies do not regulate down to their voltage until a minimum current is drawn. If you drop below that current the voltage increases. It's not usual for that to happen nowadays but older types may show it.

Another option is to look for any 24V power supply unit of the switched mode perforated aluminium cased type. These usually have a trimming pot available next to the terminals which gives about +-10% adjustment, enough to get down to 22V. I have seen people recommending named brands of these but these are cheap and generic and available just on ebay. Like anything else nowadays, the named brands are likely produced in the same factories as the cheap generic versions. Those will do the job perfectly well though they need to be cased in some way. A cheap ABS box is fine and all connections are screw terminal so it is easy for anyone with just a little bit of diy ability.

I also spoke to Blackstar technical department who were amazingly helpful! They DO NOT recommend that we run these pedals from anything above the 22V they supply. 24V may seem close enough but it is on a nasty borderline. The circuitry inside generates the 300V line for the valve stages from that supply. If you plug in 24V that is multiplied up proportionally and will end up with close to 330V which may be too much for the valve board. (Note that is other circuitry on the PCB not just the valves themselves.) So if you go that way you do it at your own risk. Likewise going down to a lower voltage may compromise the action of other circuitry inside though it would not be as risky as going higher. His advice was, you can try it at your own risk but it definitely isn't optimal and they obviously wouldn't officially recommend it.

Before any spitstorm of responses regarding the horrid "sound" of these PSU devices I would consider what is going on here. As I described, the 22Vdc line in is being used to generate a 300V line for the valve stages so it has complex intervening stages to reconstitute that, which means good isolation from the 22V. It also has to produce what is probably a 12.6V (dc most likely) heater supply which is not particularly sensitive to high frequency noise, the type most often associated with SMPSUs. It will probably just require something like a cheap IC regulated line which also would mean increased isolation. The control and switching stages could be fed from the 22V also and being non-signal do not have any great effect on sound. Remember, this is a unit specifically designed to produce large percentages of distortion in a signal. The level of additional distortion generated in the preamp circuitry by the typical 22V switch mode PSU is vanishingly small in comparison to that. This is guitar work not HiFi!!! ;)

bordonbert
Posts: 6
Joined: Tue Jul 05, 2016 5:20 am

Tue Apr 09, 2019 1:41 pm

True to their word. Delivered just after lunch the day after I ordered it. Their service was spot on in this case.

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