What can I expect from a 5150 II bias mod?

  • Thread starter Thread starter Tawlks
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Tawlks

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Thinking about getting it bias modded, What should I expect?
 
Better clean tones, and an overall smoother tone imo.
 
Yeah...but not by much. It does help...and is worth it, but it isn't noticeable if you are playing it at low volumes.
 
I hear a lot of 5150/6505 players going back and forth on the mod. Why not just put a switch at the back of the amp to go from the trim pot mod to the stock resistor? Have the best of both worlds at the flick of a switch. :confused:
 
i have two block logo 5150's

one with the mod

one without.

save yourself the money. not much of a difference.


some people prefer the sound of their 5150 without the mod as the crossover distortion is a pretty integral part of the 5150 sound :rock:
 
fuzzyguitars":3f28u3qv said:
i have two block logo 5150's

one with the mod

one without.

save yourself the money. not much of a difference.


some people prefer the sound of their 5150 without the mod as the crossover distortion is a pretty integral part of the 5150 sound :rock:
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+1
 
I think the general consensus is the bias mod helps a lot.....I've never had 2 next to each other to try side by side though so I cannot comment.
 
if your gonna pay for it, I say don't bother. On the 5150II you already have a bias trim pot. The bias mod just changes one little resistor to increase the range. IF you check your bias and your still too cold with the pot maxed out you could just get a new set of tubes that are on the warm side of things. Eurotubes or any other reputable place should be able to accommodate you. They will be marked with a number(at least from Eurotubes) and you can always order new tubes with a similar warmth to them. I didn't notice any difference on my 6505+ but with the stock tubes and without the bias mod i was still running about 29Ma. So not much colder than "ideal". I had a old 5150 for a little while and that thing was running around 15Ma!
 
As was posted above a big part of what makes that amps tone is the crossover distortion, you'll be losing that if you bias it out of the mega cold range.
 
dont the 5150 II amps have a bias adjustment unlike the original 5150's ?? i thought they had one, although it still kept the bias on the cold side of things ...
 
MYLILSS":5ih82225 said:
dont the 5150 II amps have a bias adjustment unlike the original 5150's ?? i thought they had one, although it still kept the bias on the cold side of things ...
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Yeah but the range is quite small, I'm talking a bigger increase in bias.
 
Well, I would be paying for it, but my tech is pretty easy going and has always been very reasonable with cost, if it's an easy job I don't think it will really cost me very much, he'll give me a quote before hand, ofcourse.

Better cleans is what I really want, I'd like a smoother tone on the rhythm channel, the lead channel i'm not sure.
 
The bias mod on a 5150 makes a huge difference. I've seen them stock biased as cold as 7 ma per tube. Anyone that doesn't hear a difference between 7 ma and 30 ma is deaf.
The 5150II has a bias pot and the bias mod change is not as drastic. The stock bias range can get pretty close depending on the tubes in the amp.
Jerry
 
Go for it man if you don't like the way it sounds after you raise the bias you can always adjust it back down to were it was.

I see no down side to this mod
 
JerryP":3nxvvdd3 said:
The bias mod on a 5150 makes a huge difference. I've seen them stock biased as cold as 7 ma per tube. Anyone that doesn't hear a difference between 7 ma and 30 ma is deaf.
The 5150II has a bias pot and the bias mod change is not as drastic. The stock bias range can get pretty close depending on the tubes in the amp.
Jerry
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So.. would it be safe to jack up the bias using the trim pot? Which way makes it hotter? I think my 5150 II sounds pretty good as it is but I'd like nicer cleans as I use them alot for a 5150 owner. :P
 
Tawlks":28z4cvkg said:
JerryP":28z4cvkg said:
The bias mod on a 5150 makes a huge difference. I've seen them stock biased as cold as 7 ma per tube. Anyone that doesn't hear a difference between 7 ma and 30 ma is deaf.
The 5150II has a bias pot and the bias mod change is not as drastic. The stock bias range can get pretty close depending on the tubes in the amp.
Jerry
Click to expand...

So.. would it be safe to jack up the bias using the trim pot? Which way makes it hotter? I think my 5150 II sounds pretty good as it is but I'd like nicer cleans as I use them alot for a 5150 owner. :P
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Do you know what your tubes are running at now? That would be a good place to start. They might be running very cold or very close to being where you'd want them(assuming you want them in the "out of cross over dist" area). If you know what your running at now, you might already have enough of a range with your bias pot. You could also just start turning the thing and see if it sounds better to you from far left to far right. But if you don't know what your running at now it is possible to run your tubes too hot for good tube life. You'd have to have a pretty warm set in there now though. You could get a cheapie bias probe from eurotubes and a multimeter from harbor freight tools($1.99) and check. You don't even have to remove the amp from the head box.
 
Could someone describe the tonal changes with common bias and choke mods for a regular 5150?
 
Dehumanize":1v9pnne9 said:
Could someone describe the tonal changes with common bias and choke mods for a regular 5150?
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+1 This is something I'm interested in as well.
 
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