Bias Part 2 - Steve Carr Gets Technical

[nickdrivinby]

Really Awesome video. Explained alot. I have a little 37 watt ceriatone I built a while back and I was wondering about the bias. Didnt know there was such a thing as fixed bias using the resistor. And I just got done staring at the schematic wondering what they did there with that resistor. Thanks Again!

[RJNeXon]

hey man you're the best a magnificent explanation Congratulations and thank you very much because I've removed the doubts I had about the tubes d-(=. =)-b

[glennc100]

First time this made sense to me. Thank you!  BTW, my rambler is incredible!

[Kalkaekie]

Very helpful, thanks.

[carramps1]

Hello guys

I am very happy you enjoyed the video - we will do more soon.

Generally when I hear Cascaded I think of modding Marshalls so the two preamp inputs will run into each other in series for more gain - this would be on a classic 4 input Marshall.

So Cascading is running one gain stage into another for Overdrive - usually!

[someprat]

Thanks, I've been looking for a vid like this, i have a question, when people talk about having their amp cascaded what does that mean? 

[hermeticoguitar]

Thanks a lot for this video. It's one of the clearest explanations I've ever seen about that monster called BIAS.

Great teacher!

[TheInboil]

excellent video. thanks so much

[hangfire13]

This was right out of "Back to the Future" I was waiting for an explanation of how many gigbites were needed for the flux capacitor...

[GMeyers1231]

I have a Randall RM100M, check it out if you want, but it has a bias adjustment, for the user, and it is factory shipped around 35-40 voltage, so I was wondering if that is a little low, I play metal, and I heard its better for metal players to run the tubes hot, around 80-90. So I just wanted your opinion on it.

[vmc37]

Awesome! I have an old Dukane PA which is basically a 5e3 circuit 2 6v6 cath bias..I met go for a fixed bias switch mod. Thanks!

[carramps1]

@vmc37

I am glad you fellows have enjoyed the videos!

I need to do more - perhaps today!

Best

Steve

[ChadAbdulJabar]

Thanks! Good stuff.

[iorixs]

In view B, the positive-going signal is applied to the grid. This causes increased conduction through the tube, which attempts to drive the cathode to +20 volts. But notice that the top of Ck is still at +10 volts The top plate of Ck is, in effect, 10 volts negative in relation to the top of Rk.

[iorixs]

The only way that Ck can follow the signal on the top of Rk (+20 volts) is to charge through the tube back to the source, from the source to the lower plate of Ck. When Ck charges through the tube, it acts as the source of current for the cathode. This causes the cathode to remain at +10 volts while the capacitor is charging.

[iorixs]

has anyone asked you about the Ck capacitor in parallel with the Rk resistor. im really struggling with that one.

great vid

[ulbrandt]

@iorixs The Ck capacitor is a separate path for the A/C signal, which is originating from the ground, to bypass the Rk resistor and reach the cathode. The Ck capacitor will resist the A/C current coming from ground through its capacitive reactance, which is a function of the ripple voltage and frequency of the A/C signal. The size of the capacitor (pico- or micro- farads) ultimately will effect certain frequencies of the A/C signal.

[ulbrandt]

...Therefore the Ck cap is put into parallel with the Rk resistor to provide a certain band of frequency (within the A/C signal) a quicker path from ground--than the Rk resistor is offering-- to the cathode, and thus will help tonal shape the sound characteristics of the amplification of the A/C signal.

[iorixs]

@ulbrandt thanks, i copied it down in a notebook

[barrycasebeer]

Thanks so much for posting this (and all your other videos) Steve. It is very helpful for us novice builders to have these resources from guys like yourself who are willing to share their craft, cheers!!

[benellidown]

Steve: Great amps, great videos. As I stated on your first vid, its great to see someone with that knowledge put on a level where anyone can understand. Super job. You hit points other so called 'techy's" miss which is why other vids get people in trouble.

if anyone wants a great amp, get a Carr!

[kijifled2]

You did an outstanding job explaining tube biasing great video. The way you explained it was great I think just about anyone could understand biasing after watching your video. 5 star lots of people like these types of videos with someone who knows what they are doing. Keep it up I like your videos!

[lidesnowi]

Thank you for this video!

Very helpful!

When i got the money I buy one of your amps !

[grandedog]

Thank you for this video! Some of us would like to know how this works' instead of just plugging a pile of tubes in our amps! Thanks, Steve

[prharleys]

I own a cathode biased amp with el84's. How do i know if the resistors are ok or they need service? Or if it's biased correctly?

[MrRoundel]

Very illustrative video. Biasing is now much less a mystery to me. That said, I probably will watch it a few more times to absorb the details.

I've been looking at perhaps purchasing a Carr Rambler. Your video has made this purchase more likely. Thanks.

[bzean123]

Very informative Steve. Thanks for making the video!

[carramps1]

Hello Chip

It all depends on the amp and the tubes.

If the tubes are a hot set that will draw a lot of current and require a high bias voltage and you put them in an amp set for a low current draw set the tubes could overhead and fail.

You can put them in and watch the plates for s while to see if they start glowing red - turn the amp off if this happens.

If the opposite situation happens and the tubes are very cold bias wise the amp will sound anemic.

Best

Steve

[Chipstastegood]

how damaging will it be if i put a quartet matched 6l6s in my tube amp without biasing it??