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johnnydoxx

vintage Sunn Amp test

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johnnydoxx    28

Hey GFB'rs.

I bought a vintage, brand new in box, 1969 Sunn amp Sceptre head at an auction. I tested it by running a guitar into its inputs, and running its outputs into my Crate amp's input.

Everything sounds great, I could only put the Crate on '1' or I overdrove it!

I tested it thru my Marshall amp the same way and it was fine too.

I checked with Guitar Center's tech and they said those tests were fine, and could not damage the Sunn. The Sunn has 8 ohm and 16 Ohm outputs.

Some guy from E-Bay wrote to me and said I probably ruined the Sunn.

Is there any reason to believe this E-Bay guy? I think he is just trying to cast doubt on it so the price stays low.

Thx

Johnny

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pHGTRSpider    32

There could be some truth to it being damaged as the output had no load, always best to use speakers at 8 or 16 ohms. I'd also be concerned about your Crate & Marshall. Input overload. IF they can still produce a good clean sound I'd guess no damage done. Have you got some way to get your Sunn head straight into the marshall speakers?

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johnnydoxx    28

The Sunn produced a good clean sound throughout the tests, as do my other amps - thanks for the clarification.

The Marshall is also an amp, not just a speaker. I don't have any free-standing speakers.

I don't know of any way to go just to either my Crate or Marshall amp's speakers without using their input channels.

Both of my other amps (Marshall and Crate) are OK, I backed off as soon as they got to fuzzing.

I tested on the Crate for at least 30 minutes, and the Marshall for 10 or so, and then a few minutes more on the Crate, all was fine. So I have no reason to believe that the Sunn was damaged.

What I don't want is to sell it to someone, who subsequently claims it was damaged, and tries to extort a partial refund. E-Bay somewhat leans towards buyers in that sort of situation.

Thanks again

Johnny

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johnnydoxx    28

Hey it sold to a guy who has a vintage Sunn speaker cabinet that was waiting for an amp head! He should get it this weekend, we'll see how he likes it.

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fly135    5

An amp with a tube power section can be damaged when used like that. You can disconnect the speaker in a combo and use the speaker, but that requires skills in making a speaker cable. At a minimum use a commercial speaker cable, cut off one end, and crimp on some spade connectors from the local auto supply store.

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johnnydoxx    28

Phew! The buyer says he is thrilled with the amp, it works perfectly.

The only worry he had was that UPS insisted on removing the tubes for shipment.

I warned the UPS guy that any broken tube is their problem, but he insisted.

These were the original 1969 tubes with likely very few available.

But I guess it was OK.

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fly135    5

Excuse me fly, what's the difference between guitar cable and speaker cable. Thanks in advance, cheers :brickwall:

- A speaker cable uses heavier gauge wire (thicker) than an guitar cable. The heavier wire in a speaker cable is designed to handle the higher current used to drive the speaker. The thinner guitar cable could heat up and melt internally. However, it is possible to use a guitar cable and not have a problem. Just not recommended.

- A guitar cable has a shield (foil wrap) around a dielectric material (to reduce capacitance) that encases signal wire and tied to ground. Guitar signals exist in a high impedance circuit as pickups generate a weak signal. The high impedance also allows weak induced signals from the air to enter the cable and become audible as noise. Hence the need for a shield. A speaker connection is low impedance, which means weak signals are drained to ground and there is no issue with capacitance. You could use a speaker cable as a guitar cable with no worries about damage. But if you get noise or even some loss of highs, that would be expected.

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johnnydoxx    28

Thx Fly, I had no idea about this distinction. During my live gig years, we have used many amp-to-amp connections using guitar cables, from your description that is Ok. I.e., from primary amp to monitor(s) etc.

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