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Dirty-South Blues Harp forum: wail on! >
Attenuator Added - Thanks 5F6H
Attenuator Added - Thanks 5F6H
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MindTheGap
182 posts
Jan 26, 2014
7:13 AM
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I added an attenuator to my 5W amp, and many thanks to Mark 5F6H for his advice with this.
I used a continuously variable wirewound L-Pad device, rated at 50W and intended I think to balance speakers in hi-fi cabinet, although the wiring diagram that came with it also showed it being used as a single-speaker setup like this. I chose 50W so it would be highly derated so hopefully no issues with overheating. It's quite chunky so a bit of a trick to fit elegantly in a little cabinet, but a made an internal shelf to hold it.
Now I can play the thing at a domestic friendly volume, probably a fraction of a watt, and also with others at any level up to full volume. Nice. Mark suggested that the tone might suffer but even at this level it's not bad and got that characteristic grit to it.
In this recording the amp is at the sort of volume you would listen to music on the radio, and to give an idea you can hear the drumsticks about 6ft away.
A little while ago I tried out a Blackstar 1W all-tube amp in a shop, and yes indeed it was quiet, but didn't sound like the attenuated 5W amp at all. It was nice with guitar, but with harmonica the distortion was very soft, smooth and refined. Not gritty and sharp edged. I wonder why this is.
My only concern with this is if the thing fails even momentarily and goes open circuit - we will see.
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Last Edited by MindTheGap on Jan 26, 2014 7:37 AM
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5F6H
1740 posts
Jan 26, 2014
8:33 AM
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Good news.
The attenuated amp sounds nice & crisp, even at the low volume.
The Blackstar 1W amp is push-pull (think 2 same sized people on a see-saw), the 12AU7 power tube is really 2 power tubes in one, whereas your amp has one power tube doing all the work (one person at one end of a see-saw jumping up & down on their own). Either can sound good (I have 4/5W amps in both formats), but the push-pull aspect often smooths off raspier harmonics, plus the 12AU7 will compress off piercing highs more than a 6V6.
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