Changing Tubes on Vacuum Tube Amplifiers : How to Correct Crossover Distortion on a Tube Amp

Posted by  in Tuesday, March 30th 2010   
Topics: Pro Audio    
expertvillage asked:


Learn how to correct crossover when changing the tubes on a vacuum tube amplifier in this free video. Expert: Jeff Naylor Contact: www.Mtroniks.com Bio: Jeff Naylor is the owner and operator of Mtroniks Engineering in Mesa, Arizona. Filmmaker: Eric George

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25 Comments

lantyboy said in April 1st, 2010 at 4:37 pm    

@melonheed3 i just get the shop to do it now lol only 20quid so its a bargin for the amount of time this needs done.

melonheed3 said in April 4th, 2010 at 9:41 am    

@lantyboy not that this helps too much but, i know there is a way to bias your amp using a voltage meter. still, another peice of equipment but i’d bet my bean bag that it’s cheaper than buying a fucking ociloscope.

djematrix said in April 6th, 2010 at 11:36 am    

If replacing tubes is it nessasery to bias the tube’s every time or can the tube simply be replaced.?

soverign60 said in April 7th, 2010 at 12:53 pm    

Not all tube amps have an adjustable bias pot. Many older amps have a resistor that must be located in the circuit. Then the tech needs to figure out the correct value for the installed tubes.

It is best to have a tech set up the bias on a new set of tubes if you don’t know how to do it. Every set of tubes will bias at a different point – even groove tubes that have a bias number. You may be able to get by without doing a bias job, but your amp may run too hot or too cold.

lantyboy said in April 10th, 2010 at 4:49 am    

So does this mean i cant do this myself??? how the **** am i ment to bias them with out all that gear???

henryflint123 said in April 12th, 2010 at 10:09 pm    

that is a sine wave

steelwizard said in April 13th, 2010 at 2:37 am    

Would be quite interesting hearing what crossover distortion sounds like

Kes1e said in April 13th, 2010 at 11:32 pm    

180 would just invert the wave, it would need pi/2n to match the zero crossings

Kes1e said in April 14th, 2010 at 12:21 am    

well changing the period would just change the frequency ( period = 1/frequency ), a phase shift would change the initial displacement so the difference between a sine wave and cosine wave is 90 degrees making them equal. In the electronics world most people just refer to any oscillating wave as a sine wave.

unragamuf said in April 14th, 2010 at 12:33 am    

u mean same amplitude and wavelength different period

Kes1e said in April 15th, 2010 at 8:04 pm    

there both the same wave just a phase shift of pi/2

DethDaeNossi said in April 19th, 2010 at 1:35 am    

Yea cuz there are local tube amp shops all over the place.

laitela01 said in April 19th, 2010 at 1:27 pm    

Because it contains high levels of suck

unragamuf said in April 21st, 2010 at 10:14 pm    

that is a cosine wave not sine

coronet67 said in April 24th, 2010 at 7:42 am    

Oh ****. I cant find my sine wave generator. I think I left it in my other pants.

madamerotten said in April 25th, 2010 at 10:08 am    

Why not use transistors?

epicLalonde said in April 27th, 2010 at 3:14 am    

HAHAH LMFAO !

guitarlad24 said in April 28th, 2010 at 3:37 pm    

amen to crilledisst

crilledisst said in May 2nd, 2010 at 12:22 am    

I think Jack Black and Jim Carrey had a baby. This baby is now grown up and posting vids on youtube about biasing…

scaleop4 said in May 2nd, 2010 at 11:36 am    

thanks man.

Someguytarhero said in May 5th, 2010 at 9:37 am    

ahh yeah cuz every has a cathode ray osilloscope…..lol imma bring my amp to skewl nd hook it up to theirs

diggy3746 said in May 7th, 2010 at 10:27 am    

Wow thanks for much for these videos on the biasing. My current major in mathematics and I think its awesome how sine waves come into play with this :D

Charliemusslewhite said in May 10th, 2010 at 4:32 pm    

Thanks. Maybe it does matter in a PP Amp if the low-signal (near middle/zero) cutoff is balanced on both sides, I would expect a little cutoff on both sides would sound better than a higher-level cutoff at one side and very small or none on the other side. To have a bit low-signal (near middle/zero) cutoff could be useful for harmonica to have a noisegate = anti feedback. Just a thought…

takitezy7 said in May 11th, 2010 at 12:49 am    

It sounds like you got 2 overlapping distortions thats not in sync. Very undesirable!

PutItAway101 said in May 14th, 2010 at 4:17 am    

Thanks for this great video.

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