Awesome video!!! I have been designing Vacuum tube guitar amplifiers for 28 years since getting my Degree in Electronics. I was a guitarist and loved their tone and dynamics there was little academic emphasis on tubes during formal education most of my knowledge I gained searching out "Old Timers" and discovering the Radiotron Designer's Handbook 4th Edition, which I notice you reference is a "Goldmine" It's nice to see somebody knowledgeable! Best Regards
@stormriderkaos Жыл бұрын
Someone likely mentioned this in the comments already but... faulty old filter capacitors are definitely a source of hum in tube amps and not a rare issue in vintage tube guitar amps.
@ryanybos3 жыл бұрын
Now here's some good usable knowledge thank you Jim !
@kevinbeckenham38728 ай бұрын
Thank you for explaining how get rid hum, in my ferrograph series 4 valve reel to reel tape recorder
@robertholley21952 жыл бұрын
bless you mr whiteside
@pkontopoulos16 күн бұрын
Excellent and extremely useful educated info into hum of tube amps. A question please. I have a class A SE UL stereo amp I am designing that has a NFB from speaker 16Ω tap to the 12AX7 preamp cathode. I get a light hum that peaks at 100Hz and 150Hz acoustically analysed. If I input 1000Hz I see the envelope of the output modulated possibly by this hum. If I do your nice advice I will probably have two signals added at the cathode of 12AX7 (one is NFB and the other fro R hum resistor). Will that work? I will certainly try but is it possible?
@jedishaw67713 жыл бұрын
Great info! Thanks for doing the video!!
@dumpsterchicken62874 ай бұрын
I have a question. My output tube cathode has the parallel resistor/capacitor, but not the other resistor to the cathode. Can I attach R hum directly to the cathode? Thank you.
@xaz70883 ай бұрын
could it be done in a PI to PP output stage?
@Joshua-to5bl2 жыл бұрын
Awesome amazing masterful!
@pipercherokee85986 ай бұрын
Would the same steps apply to trying to diagnose 180Hz hum? Not entirely sure where it is coming from, but it is present with all knobs at minimum and nothing plugged in. The hum then increases with the REVERB knob, even with volume at minimum. Interesting. And, it is present even if the reverb tank and footswitch are disconnected entirely. Thoughts? '65 Princeton Reverb clone. Thank you, your channel is very informative!
@deepblueharp6 ай бұрын
Please send me an email (see my KZfaq channel). I am going to need some more information and maybe a sound clip for analysis.
@johnston.scott642 жыл бұрын
I believe this would be applied to the output power amp section. I have a hybrid Marshall. A 12AX7 preamp with a solid state output. I'm not quite sure if rewiring the preamp with a triode tube would produce any quantifiable results.
@deepblueharp2 жыл бұрын
A solid state output has other issues, so this isn't applicable. Also, a triode power tube is much less prone to hum and should not need this neutralizer in most cases.
@deuce-way1440Ай бұрын
I still have hum in my push pull build using this setup, any other tips for dc elevated heaters?
@deepblueharpАй бұрын
I will share some general information because I don't have a photo of you chassis. If you still have hum, the top issue is generally wiring. The wiring must be absolutely neat. If you look at a Fender Deluxe, you will notice all the wires are no longer than required to connect between 2 points. There must be NO EXCESS wire. Excess wire acts like an antenna to pick up noise from the B+ or Heater wires. All the wiring needs to be laid flat against the metal chassis so the chassis can absorb and ground out any interference that is causing the hum. If a wire needs to cross another wire it must cross at a 90 degree angle. Also, do not run any wire along the side of a component (cap, resistor, etc.) Wire must cross over the component at a right angle or not at all. Wiring at a socket or a pot is a challenge because that last inch at the lugs requires running wires in parallel. (UGH), but just 1/8 inch of separation can make the world of difference. Tube amp wiring is challenging.
@Attic-Toy-Design3 жыл бұрын
Excellent video. Could you please explain how to get rid of hum on the Marshall 18 watt lite amp from preamp? Thanks .
@deepblueharp3 жыл бұрын
The most common solution to that amp is to elevate the heater. There are several schematics online showing how. Basically, it involves connecting the heater centertap to the cathode of the power tubes. That raises the heater centertap to the bias voltage of the power tube and quiets the residual hum.
@davidbolus3 жыл бұрын
Great video and tutorial - thank you very much for the information. How would you handle a fixed bias push pull circuit such as a Princeton 6g2 layout? Any suggestions regarding the Inversion and injection point into the 2 power tubes?
@deepblueharp3 жыл бұрын
Thanks for watching. It is a solution for single-ended amps only. Because: Rule 1: PP configurations are hum canceling circuits. Rule 2: The PP tubes have grounded cathodes, which makes the PP configuration absolutely & positively deathly quiet. If not, then 1) one or both of the tubes is/are getting old, 2) the power filter caps on the 5Y3 are suspect or 3) the preamp tubes are the problem: old tubes or the connection to the input jack is creating a hum (ground loop issue).
@davidbolus3 жыл бұрын
@@deepblueharp Makes sense - thanks for the response!
@NickAnanas3 жыл бұрын
Hi, very interesting technique. I wonder why does V2 has two resistors, is to implement correctly? because usually there is only one resistor with a capacitor. Secondly, does it need the filter capacitor on the cathode resistor or it will still work without the capacitor? Thank you
@deepblueharp3 жыл бұрын
On the cathode: one resistor is 1 ohm to take a direct measurement of the current the other sets the bias. The cathode does not need a bypass capacitor for this to work.
@NickAnanas3 жыл бұрын
@@deepblueharp thank you!
@CraigHollabaugh7 жыл бұрын
Nice work, there's multiple things going here, raising the filament supply, adding feedback to V1's cathode which might contain 60hz because of filament raising, and not introducing phase shift with coupling capacitor. Getting out my tattered RDH4 now to see what it says. I'll keep your handy dandy tip ready for future designs. Thanks
@dcbluez48838 жыл бұрын
Putting a 12.6vdc regulated heater circuit would also help also. At least on the preamp section. Power tubes 6.3vac no problem since they cancel out.
@dcbluez48838 жыл бұрын
Even if there is a voltage rise on V1 cathode this could be adjusted back down with resistor value changes on the V1 cathode and or plate resistor.
@lroy7307 жыл бұрын
Great Video. I've ben using similar cicuits for years. In some amps I can even get a boost on some frequencies... Funny how most well know Amp Mod Guru's don't know anything about Noise Canceling Inverting Loops. These work well and you don't need to add a big cap.
@fisherterrell7143 жыл бұрын
i guess I am pretty randomly asking but do anybody know a good site to watch newly released movies online ?
@eugenejavion86863 жыл бұрын
@Fisher Terrell Flixportal :)
@fisherterrell7143 жыл бұрын
@Eugene Javion Thanks, I went there and it seems to work =) Appreciate it!
@eugenejavion86863 жыл бұрын
@Fisher Terrell Happy to help :D
@dcbluez48838 жыл бұрын
Very nice idea. I will give it a shot. From what I can see from your schematic is coming off V1 cathode, use a 470K to the cathode of V2, or power tube. Is this correct? Would like to see the waveform after the resistor is added. Thanks much
@christopherchirico81707 жыл бұрын
It works! Thank you for posting. I have one question though. Could you put a variable 20k resistor in place of the Rhum?
@deepblueharp7 жыл бұрын
+Christopher Chirico Yes, you can if you have space. Thanks for watching and I am glad it worked for you.
@christopherchirico81707 жыл бұрын
HI, I am going to try the 20k pot today. I just wanted to clear up something first, If you have time. I did not have a center tap on my 6.3 v secondary and used the 2 x100ohm to create one. This center tap lead would then go to the wiper on the pot and the 1 and 3 would go to the respective V1 and V2 cathodes directly on the tube pins. Correct?
@jfrheavy18 жыл бұрын
hi your video help me a lot, but my circuit only have preamp, can i do it whit only 12ax7? ( sorry for my English I'm peruvian )
@deepblueharp8 жыл бұрын
+Jonathan Fernandez yes.
@thatsfunnyjimmy13518 жыл бұрын
How would you use this technique on a class AB push pull tube amp where the cathode is grounded on the power tubes ?
@deepblueharp8 жыл бұрын
I had this question sent to me last week and I have had time to think about it more. I really wouldn't suggest doing this with power tubes of a AB amplifier. The cathode will need to elevated and the RC filter needs to be rated for 7 watts. However, it can be done. The cathode of the power tube needs to be elevated to 2VDC to 5VDC and a resistor (10W rated) connected from the cathode to the output of the preamp (generally the second stage). It is the preamp that is normally the source of the hum that needs corrected. So... What would be better is to elevate the ground on the preamp section. Connect the centertap of the 6.3VAC filiment to the RC filter of the preamp second stage (it is normally at 1VDC). Then connect a resistor from there to the cathode of the first stage of the preamp.
@martynshaw72143 жыл бұрын
@@deepblueharp can you do a schematic for this
@Echo_III7 жыл бұрын
Sir, let's say I want to use oscilloscope on my computer (PC software). Can I hook amp an amp (Speaker taps) to a PC? How one can do that?
@deepblueharp7 жыл бұрын
No, you cannot hook your PC to an amp or any other high voltage device. It will require an interface that will isolate your pc from the devices (like the amp or speaker). The isolation devices will output safe voltage levels for the pc (under 5 volts). I have no recommendations for you. I use an oscilloscope that has outputs to send to a pc to safely acquire data.
@Echo_III7 жыл бұрын
Okay, thank you. Any advice about parameters which good oscilloscope should have?
@deepblueharp7 жыл бұрын
I would suggest looking at the Hantek HT6022BE20MHz 6022be PC based usb digital storage oscilloscope's specifications. Also, it is really inexpensive.