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Hartley Thompson Amp Schematics


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Hi all.

I have a Hartley Thompson stereo amp/preamp and slave and have unfortunately lost the channel footswitch. Originally the footswitch connected to the amp via a canon connector (amp side is male), and this enabled switching between the Red and Green channels of the amp/preamp.

There are some issues which complicate matters though:

1. The amp uses an LED which changes colour from Red to Green, and as far as I can remember, so did the footswitch.

2. I have been able to get the channels to switch just by connecting a female canon to the male canon, with only a pair of leads coming off it, presumably one + and the other -. This works, but produces a loud thump as the wires are brought into contact and the channels switch, so I imagine that just putting a DPDT switch in line with this circuit will produce the same effect. So I am guessing that there needs to be some sort of supression circuitry in the footswitch, and I have not the slightest clue about electronics, as you can probably tell :D

I would also like to obtain a copy of the schematics for this amp, as I would like to be able to rebuild both the pre/power amp and slave amp into a new 19" rack sized enclosure, as presently it is quite a bit wider than rack size.

Originally, for those who are unfamiliar with this amazing amp, this is the mos-FET amp made famous by Allan Holdsworth, and is the only amp I have owned that comes even close to his sound. This particular amp is the one used by Steve Topping on the Level 42 tour that he took over from Allan Holdsworth, so it is really a prototype and features switchable 'sustortions' on either channel. You could look upon the HT as a forerunner of the Pearce amps as it has a very similar format.

The amp/pre-amp was combined in a 2x12 cab as a combo, but with an output to provide a stereo image to the slave amp, which was also housed in a 2x12 combo format. That made the entire setup both heavy, unwieldy and impractical, because both cabs were wedge shaped, making side by side transport very difficult - so when I moved to Spain from the UK, I lost the cabs and only kept the innards of the amp and slave. In any case I was unhappy with the Goodmans Powermax speakers that came with the amp and slave, so once I complete the rack rebuild, I will start to look at building a pair of cabs, probably using Celestion G12s or similar.

The design of these, being triangular, allowed me to find a way of bolting them together back to back, that actually forms an elongated square, as seen from the sides, but as I say, the width precludes rack-mounting, which is why I am trying to find a means to rebuild the internal circuitry etc into a 3 or 4U rack format enclosure. Presently the structure of the enclosure is not very deep, so with the additional depth offered by a 19" rack, I see no problem in getting everything to fit, especially as the slave amp only uses about half of the physical space taken up by the enclosure.

I apologize for my verbal description, but I can post photos if that is any help...

Here in Spain it is not as easy to get anyone to help with this as it would have been in the UK, and I also want to find a physically lighter alternative to the folded aluminium construction of the enclosure.

Any help would really be appreciated.

Thank you for taking the time to read this post. :D


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