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Old 15th January 2009, 01:39 AM   #1
damage is offline damage  United States
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Default anyone recognize this amp?

Here is an amp I picked up on the cheap today.
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Old 15th January 2009, 03:43 AM   #2
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It's one I built.

What's wrong with it?
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Old 15th January 2009, 03:54 AM   #3
damage is offline damage  United States
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Quote:
Originally posted by Perry Babin
It's one I built.

What's wrong with it?
Nothing! Except the fact it won't multiply into two or three. I picked it up today for $20. This thing cranks!

Any recommended upgrades or maintenance I should do?
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Old 15th January 2009, 03:56 AM   #4
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Not really. It looks like a rev. B board. It's marked under the transformer.

What op-amps are in the sockets near the RCA jacks?
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Old 15th January 2009, 04:04 AM   #5
damage is offline damage  United States
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Rev B.

mc33078P/79P

The BB is an OPA2227P
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Old 15th January 2009, 04:15 AM   #6
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If you replace the 33078/79 with the opa2227 and 4227, you can probably lower the noise floor but the 78/79 are pretty quiet. You can't use the 2228 or 4228. They are not unity gain stable and will oscillate.

The BB op-amp is for the DC servo. The DC offset should be close to 0.000v.

The amp was designed to be able to take the signal from the speaker level output of a head unit (not an amp) with no line output converter. Positive speaker wires connect to the center conductor. The negative speaker wires connect to the shields. Turn the gain all of the way down. That's how most of the ones I built (less than 10) are running.
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Old 15th January 2009, 04:25 AM   #7
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If you do take it apart, get Perry to explain the clamp tightening technique. If you just tighten each screw once, it is not tight. You have to tighten each clamp about 4 or 5 times. It appears as though you would be upset if you took it apart and failed to properly tighten the clamps.
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Old 15th January 2009, 05:07 AM   #8
damage is offline damage  United States
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I don't imagine then that I will be doing any "improvements" to the amp. As soon as I saw it, I knew exactly what it was. I had visited the website before and was very excited to see it.

How many of these were made?

The amp didn't seem to have any problem being driven by my Adcom preamp. But I did have to feed more power than I normally do. Would I be able to drive it feed from the x-over of my Zapco? I'd really like to use this amp to feed the dash speakers.
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Old 15th January 2009, 05:42 AM   #9
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I don't think there would be any problems driving the amp with the Zapco preamp. I don't think there's any way that you can hurt it. When testing it, I abused it in every way I could think of.

If your amp has 1k resistors on the side of the op-amp behind the LED, you can change them to 3.3k. That's whats in the newer versions. If you can get enough output as it is, leave the 1k in it.

It's a lot of power to be driving dash speakers. Before you install it permanently for the dash speakers, try it for bass or full range duty. It's a standard 2 ohm stereo/4 ohm mono amp.

I don't know if you noticed, but there are jumpers for the high pass, low pass and full range operation.

There's a fan header in the power supply. Use it to drive an 80mm fan if it runs hot. For the power output, the heatsink is a bit undersized. Instead of reducing the power output, I provided a way to keep it cool. Set up the fan to blow into the PS end of the amp and through the fins.

I made less than 10 of them (including rev a and b). They were too time consuming to build. Rev C was laid out but I never had any boards made for it.

Use a 40 amp fuse in the B+ line.
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Old 15th January 2009, 05:25 PM   #10
spooney is offline spooney  United States
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how many watts is this amp?it looks great
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