I have a 1970 Hiwatt DR103 which I run through a 2x15 Fender cab with EV speakers. It sounds great, but I don’t like to drive the amp too much because it loses the clean sound that I love. I recently bought a STA 200 Hiwatt slave amp to get some more power to drive the 300 watts of speaker I have. How do I link up the DR103 to the slave amp if there is no slave output? If some sort of power soak is required, can you suggest a good product?
-Tim
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Tim,
I would say the easiest way for you to accomplish this would definitely be with a power soak. There are many power attenuation devices on the market, but you need to make sure that for your application the unit you choose has a line level output, as some do and some don’t. A couple of quality units out there that feature a line level output are the THD Hot Plate and the Tube Amp Doctor (TAD) Silencer. These units will let you run the DR103 as your main amp while utilizing its output in a couple of different ways.
First, you could simply connect the output of the DR103 to the input of the attenuation device and set the device to function as a “load” only. This would safely load the output of the amplifier, taking the place of your speaker cabinet, while providing you with a line level signal to send to the STA 200. Assuming that you only want to use one speaker cabinet, this would be the setup for you. Use quality speaker cable to connect between the amp and the load, and quality musical instrument cable to connect the line level signal from the load to the slave amp.
Another option, requiring two speaker cabinets, would be useful to get the most power out of your rig for the biggest venues. Simply connect the attenuator between the DR103 and one speaker cabinet and set the device for 0db attenuation. This will give you full power transfer from the DR103 to the speaker cabinet. You can then take the line output from the attenuator and send it to the STA 200 slave amp, the output of which you would connect to a second speaker cabinet. This gives you the full output of each unit through its own speaker cabinet. Since the main amp and the slave amp are produced by the same manufacturer, you’ll hopefully not need to be concerned with the amplifier outputs being out of phase. This can be a problem at times when using different amplifiers, but can usually be corrected via the use of a super-secret “phase correction speaker cable” (hot and common reversed at one end … oops, there goes the secret!).
Now go forth and produce many decibels of clean Hiwatt power.
I just received a JMP 800 100-watt Marshall from Italy. The main selector switch, and ohm selector switch have been rewired on the inside, bypassing the switches. I understand that these switches are a bad design and why the previous owner rewired it, but I need to rewire the amp for 110, because I am sure Italy runs 220. My question is as follows:
The input transformer has blue, orange, and yellow wires. The yellow wire is disconnected and taped. The blue and orange wires are twisted together. What do I need to do and what wires go where for 110?
The output transformer has black, purple, and green wires. I take it that this is what was soldered to the main selector switch. The purple and black wires are twisted together, and the green wire is disconnected. What color wire is for what ohm?
The power cord has a 220 plug, and I need to hook up a 110 plug. Will the same color code on the 220 plug be the same for a 110 plug? I just want to cut off the 220 plug at the end of the cord, and add one of those 110 plugs that you get at the hardware store.
-Rick
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Rick,
Short of telling you how to repair the amp, here are the stock wire color codes you’re looking for. Personally I’d have to recommend that you take the amp to a qualified service tech. You mention that the AC mains blue and orange wires are twisted together, and if you mean that they’re connected together, that doesn’t seem correct. Anyway, here you are:
AC mains:
Orange – common,
Red – 120V,
Blue – 220V,
Violet – 240V
Output:
Brown – common,
Black – 4 ohm (with violet feedback wire),
Yellow – 8 ohm,
Green – 16 ohm
AC line cord (Euro vs.US w/ screw colors):
Blue=White=Common (silver),
Brown=Black=Hot (gold),
Green/Yellow=Green=Ground (green)
Jeff BoberCo-Founder and Senior Design Engineer – Budda Amplification
jeffb@budda.comwww.budda.com©2007 Jeff Bober