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Post by sergea on Jul 3, 2021 19:03:41 GMT -7
Hi folks, first time post here. I realize this topic has been discussed ad nauseam, but I'm hoping someone might provide some clarification. I have an M12 1x10 with 5y3 rectifier and el84. Happy with the sound but I'm looking to experiment with a little less headroom and lower output for living room fun. I've read a lot about the Steve Miller mod, and have a pair of jj el844 and a sovtek 5ar4 on the way. Will I accomplish what I'm going for simply by installing the el844s and not the 5ar4 rectifier? If I decide to also install the 5ar4, will I need to swap the bias resistor? I've read conflicting info about thus, with Dr. Z suggesting to change it, but in another forum saying it wasn't necessary. Any guidance would be greatly appreciated.
- Serge
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Post by pcns on Jul 3, 2021 19:06:16 GMT -7
I recomend following the Dr's orders. š
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Post by sergea on Jul 3, 2021 19:56:30 GMT -7
It was Dr. Z himself saying the M12 could accommodate the tube swap without bias resistor swap in the other forum. "For a nicer lower volume, higher drive tone on the M 12 install a Sovtek 5AR4 rectifier, then swap in JJ EL 844 output tubes, no bias needed, cuts overall wattage and increases break up. The M-12 can be ordered that way from the factory. DR.Z" www.thegearpage.net/board/index.php?threads/dr-z-m12-earlier-breakup-option.1717831/
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Post by jhen86 (jordan) on Jul 3, 2021 21:25:37 GMT -7
If you want more drive at lower volume the hotter bias resistor is not a good idea. And you are correct, you donāt have to change the bias resistor either way. It will just bias the amp hotter for more power/wattage. Read that as more loud. And tubes die faster
Given the nature of what you want to do, you may not be able to get more drive and less volume at the same time from the M12 without an attenuator. I have a secret rectifier I like that gives good drive and still sags (better than 5AR4). But still more volume/power.
Iād say start with the 5Y3 and EL844ās. See if you like it. If not, do the 5AR4 and some sort of attenuation.
if attenuator isnāt an option, a lower efficiency speaker could help. Or just get a good overdrive pedal with good crunch and low volume. The M12 eats dirt pedals all day.
Actually, a variac could also be an option. Run the M12 at 100v if youāre here in US. Could be fun.
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Post by sergea on Jul 4, 2021 2:56:07 GMT -7
Thanks Jordan. I'll do some experimenting. Just to make sure I understand correctly, a 150 Ohm 10 watt bias resistor will run the amp hotter, louder, and eat tubes faster as compared to a 180 Ohm 10 watt resistor? Or is it the other way around? Thanks.
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Post by jhen86 (jordan) on Jul 4, 2021 6:12:20 GMT -7
Correct. 150 ohm will produce the opposite of what you are wanting. Leave it stock 180 ohm. P
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Post by bubs42 on Jul 11, 2021 17:44:56 GMT -7
Iād go with the tube / Rec swap and depending on what speaker your using a speaker swap. If your using a Fang, or a Z Stock speaker a lesser efficient 10ā will drop the volume and at a little grit.
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