SuperBee
5374 posts
Apr 15, 2018
6:12 AM
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I’ll have to try recording them, but haven’t yet.
This weekend I got a valve jr which had the full ‘alnicomagnet’ mod. Much of that mod is about adding a line out, adding a standby circuit and a fuse, installing some better quality parts, like a better volume pot and some bigger caps in the power supply, and ensuring the el84 is running within spec. But it also adds a tone control and some voicing mods.
The amp still has a lot of gain, unlike the lone wolf mod for instance, which reduces gain of the stock amp quite a bit by removing the cathode bypass cap on the first preamp stage.
I also put my 5F1 on the bench and changed the power supply to a lower voltage. With a 5y3 rectifier it was previously running with about 390vdc on the plate of the 6v6, and over 200 vdc on the preamp plates iirc.
Now it has 320 vdc on the power tube plate and 150-160 on the preamp plates.
I believe this would be more like the original voltages for this design.
Anyway, when I plugged in I didn’t know what I expected but I was surprised I think, that the amp didn’t seem to have lost any punch at all, in fact it seemed to have a more defined tone than before. The breakup seems less fizzy, like it would have more cut.
I had the valve jr ‘right there’ so I plugged into that to compare them and to my surprise had to turn up the jr to get near the champ, but when I had them both at a comparable volume I found it rather hard to tell them apart, at least I seemed to be able to adjust the tone of the jr to give a very similar result as the tweed champ.
I dunno, maybe I just don’t have the ears for this. Or maybe it takes longer than a few choruses of Juke and have a good time to pick the subtleties.
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