Help me NOT blow my 5150

[Pierre]

Re: Help me NOT blow my 5150

in a class AB amp, the bias is set at idle. The current flow will rise a lot as the amp is wound up. This is the big difference compared to class A amplification, in which the power stage runs full current all the time, regardless of how it is being used. If the original post refers to he current measurement (in MilliAmps) going 'well out of range' when the amp is turned up, that is perfectly normal.

The figures usually given are for the idle state. Think of it like tuning a car engine....the tune-up specs would probably say to set the idle speed at 1,000 RPM or something similar. When you drive the car, the accelerator pedal allows you to adjust the RPM anywhere you want for the speed you want, but when you release the pedal, it should return to it's 1,000 RPM idle speed. That idle speed sets the foundation for all other performance.

Bias on a class AB amp is the same. Dial all the knobs to zero. Set the bias then play for a while and keep an eye on the tubes. Maybe re-check the bias after that. Bake in a moderate oven for 35 minutes and serve with a side salad.

Oooops ok well I'm totally wrong about it then :laugh2: Thanks!

 

[JB_From_Hell]

Re: Help me NOT blow my 5150

I don't know if I laughed harder at the mouth thing, or odie saying Holla :laugh2:

 

[theodie]

Re: Help me NOT blow my 5150

I don't know if I laughed harder at the mouth thing, or odie saying Holla :laugh2:

LOL!!!!!!!

I think not matter how hard he tried, he could not pull it off. It would take someone like Mick Jagger, Steven tyler, or sandra bernhardt to be able to do what he wants to do to his amp. Or does he not want to do it????? LOL!

 

[Virtual Kevorkian]

Re: Help me NOT blow my 5150

5150's are biased incredibly cold from factory... It's part of the 5150 sound. With it biased hotter, it's warmer and has more dynamics, but it's not as tight/chuggy and doesn't have as much grind on the top end.

 

[That90'sGuy]

Re: Help me NOT blow my 5150

Yeah, it's a good idea to buy a bias tool, like the one I have in my Vault thread on biasing the Jubilee. I paid $15-$20 for it off Ebay. Also, own a volt/amp/ohm meter.

Sometimes, when biasing an amp, the amps starting fluxuating when you're turning the bias pot on a live amp. If that happens, turn off the amp for half an hour, and start again. The goal is to get a steady reading of about 32 mA, no matter where the volume is set on the amp. 32mA for 6L6's and 36-38mA for EL-34's. With E-34L's, you can get away with a bit more, like 30-40mA.

The problem with a stock 5150 is that it doesn't have a bias pot, so just pop the tubes in, and they should be within range, as set by the factory, using a resistor instead of a pot.

+1,000,000.

 

[theodie]

Re: Help me NOT blow my 5150

5150's are biased incredibly cold from factory... It's part of the 5150 sound. With it biased hotter, it's warmer and has more dynamics, but it's not as tight/chuggy and doesn't have as much grind on the top end.

...you ever blown one though?

 

[Mr 9finger]

Re: Help me NOT blow my 5150

...you ever blown one though?

EVH musta been a mans man cuz he blew quite a few. :laughing::laughing:

 

[SizzleSale.com]

Re: Help me NOT blow my 5150

5150 doesnt have a bias pot

 

[Virtual Kevorkian]

Re: Help me NOT blow my 5150

5150 doesnt have a bias pot

It does if you get it modded - Jacob purchased his pre-modded.

 

[theodie]

Re: Help me NOT blow my 5150

EVH musta been a mans man cuz he blew quite a few. :laughing::laughing:

If ya look at his mug, he fits into the Jagger, Bernhardt, Tyler catagorey too. LOL!!!!!!!!!