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Post subject: Greta Tube Change out
Posted: Thu Aug 23, 2012 9:45 am
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Hey I dont have a Greta yet but I want to get one to use as a Harp amp. I was wondering if switching the 12AT7 tube that came with it with a 12AU7 would hurt the amp? I've heard these tubes give a "fatter" tone?
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Post subject: Re: Greta Tube Change out
Posted: Thu Aug 23, 2012 3:17 pm
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Why don't you wait until the amp arrives and you take it for a "shakedown cruise" before you attempt any nebulous hot-rodding? You may find that it sounds just grand right out of the carton.

In any case, the 12AU7 is an extremely low-gain dual triode (approximately one fifth that of the ubiquitous 12AX7/7025). If the Greta's V1 is a 12AT7, I *might* experiment with a 12AY7, which has roughly 15% less gain than the 12AT7. A 5751 might also offer some sonic advantages.

But wait until you hear the amp in stock trim first.

HTH

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Post subject: Re: Greta Tube Change out
Posted: Thu Aug 23, 2012 3:26 pm
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Thanks for the reply. I will give it a go stock, I may get to try one out before I buy. But I was basically curious about changing tubes and I didnt want to damage anything if I wanted to experiment.
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Post subject: Re: Greta Tube Change out
Posted: Thu Aug 23, 2012 3:29 pm
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There's virtually no chance of damage to the amp by swapping out pre-amp tubes so long as you get them correctly seated in the tube sockets. The amp must be switched off when changing bottles.

Arjay

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Post subject: Re: Greta Tube Change out
Posted: Thu Aug 23, 2012 3:47 pm
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Actually, the Greta uses the 12AT7 as the power output tube:

http://www.fender.com/products/pawnshop ... 2303000000

A 12AX7 is used as the preamp tube.

I believe there are some very low power amps that use a 12AU7 as the power tube, but I would not swear to that. In any case, I don't know what the affect would be of replacing the 12AT7 with a 12AU7.

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Post subject: Re: Greta Tube Change out
Posted: Thu Aug 23, 2012 6:34 pm
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bluesky636 wrote:
Actually, the Greta uses the 12AT7 as the power output tube:

http://www.fender.com/products/pawnshop ... 2303000000

A 12AX7 is used as the preamp tube.

I believe there are some very low power amps that use a 12AU7 as the power tube, but I would not swear to that. In any case, I don't know what the affect would be of replacing the 12AT7 with a 12AU7.


Do you think it would be dangerous? Sorry for the lame questions but I don't want to do something stupid. It just might something I won't even fool with. Thanks for the replies anyhow.


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Post subject: Re: Greta Tube Change out
Posted: Thu Aug 23, 2012 8:05 pm
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dbush_4 wrote:
bluesky636 wrote:
Actually, the Greta uses the 12AT7 as the power output tube:

http://www.fender.com/products/pawnshop ... 2303000000

A 12AX7 is used as the preamp tube.

I believe there are some very low power amps that use a 12AU7 as the power tube, but I would not swear to that. In any case, I don't know what the affect would be of replacing the 12AT7 with a 12AU7.


Do you think it would be dangerous? Sorry for the lame questions but I don't want to do something stupid. It just might something I won't even fool with. Thanks for the replies anyhow.


Without looking at the the specs for both tubes, I wouldn't try it. Maybe someone else here has the specs handy. I don't right now.

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