+Thomas Coughran You're welcome, Thomas. We're glad the videos are helpful. In 1966, I was a college sophomore, well-versed only in beer guzzling and womanizing......sadly, electronics videos were not on the agenda :)
I don't know HOW you ever get anything done without the tremendous help of Rusty and Jack! They really make all your videos possible! Lol! ( Seriously, thanks for yet another INCREDIBLE video! [ As always!] )
It is only now that I can fully understand vacuum tubes, we only had a glimpse of it back in the school days...we are more on semi- conductors ......nice Uncle Doug....
+Cawfee Dawg Very well said. He has definitely developed into a high- and low-pass filter. As you say, any request with which he is not inclined to comply tends to be eliminated from the circuit :))
I own a Princeton for 45 years and until watching this video I didn’t understand the difference between input no. 1 and 2. I could hear it, but only now I know why. Thank you very much!
Thank you so much for this video. I've been modifying my WEM ER15 to be more like a Marshall 1974 with success but had a concerns about the changes to the input resistors. I've looked up loads of stuff, which mostly only refer to the electrical implications to the preamp valve. Your video shows me exactly what practical changes they make.
Hi Doug, the cool thing with your videos is, that you can sit down with a beer and chips end get entertained while learning! Big thanks!!! I like the explanation of the Fender input circuit. I was scratching my head to understand it, until I included the switching input jacks and sketched the to different states separately as you did.
+Murrat Osmani Greetings, Murrat. It's great to hear that the videos are helpful and entertaining, and that you took the time to diagram the Fender input circuit and study it until you figured it out. Generally the best lessons are the ones we teach ourselves. Enjoy your beer and chips :)
Doug this is great. I actually used the knowledge of tube capacitance to modify a 5f1 input which was going into severe oscillation only when there was no guitar or cable plugged in. I did not want to use a shorting input jack in this case, I wanted ultimate simplicity. What I did was use a very small cap (determined by using a 15k signal and O-scope across the input jack thus giving me a bit more of a ultra hf filter but not affecting the audio. This gave me more lattitude in the type of tube used in the first stage. Worked great! Thank you again.
Hello Uncle Doug! I've been following your videos for quite sometime now, and have rewatched them countless times, and every time I rewatch your videos, I learn something new. I just want to thank you for putting up these videos, as they've helped me immensely with my DIY guitar tube amp stuff. I couldn't understand any of the tube amp books in our local library. You've simplified this enough for non-engineers to understand, and yet be comprehensive. You have my deepest gratitude.
I want to see a video on your jukebox! Jack and Rusty can help. Your description on how tubes work is the most basic, yet complete training I've yet to see. Thanks! I've been a ham for 28 years and worked a lot with tubes, but never knew how exactly all the resistors and capacitors work together. I'm not sure what your background is, but you would be a perfect candidate for the "boat anchor" AM ham community.
Oh man, you're my savior. My recent ab763 build has weird behavior on vibrato channel, when i turn my volume pot above 3 it starts squeal and one of my 6v6 was red plating and load voltages drops and jumping between 300 and 350 volts, also i burn two 1w 470ohm screen resistors on red plated 6v6. When i watch this video i decide to play with my 68k grid stoppers and boom! now it works fine! I think it was just bad joint between resistors and wire, holy crap that little bastard freak me out for whole week.
Well that cleared up the mystery of the input stage for me. Perfectly clear. Thanks once again. Jack has pretty much finished your training now. I am guessing you do the retrieving for him off camera. And a crystal water cup, I had to quickly cover my cat's eyes when you showed that!
+Barefeet200 You're welcome, BF....glad it was clear and helpful. Yes, Jack is definitely following in Rusty's footsteps as a highly motivated performer who gives his all for every performance.....in between sips from his crystal goblet :)))
Now it all makes sense. I was looking at the resistors on the fender princeton this weekend and was struggling as to how it works. Your video is crystal clear. Thank you very much.
I found this when I searched for Grid Leak Resistor. I'm glad I did. I'll be watching your whole series now. Not just for the knowledge you impart, but also for Jack the Cat. Thanks for sharing this!
Greetings Doug, I have been watching your resistance videos and I finally understand what input impedance in a tube amp is and how it works. Thanks! Now onto the next two videos in the series. I have bought my first tube amp, it's in transit, and I will be using my new knowledge to measure what is going on in the new amp. As an aside, I too have an all black cat with the same amazing retrieval skills. Eric
+bullthrush I'm beginning to think there are no truly simple subjects, Andrew, even with something as seemingly basic as resistors. The more you investigate, the more you find. I start out envisioning a nice 5-minute video, and end up with four parts (so far) and over an hour and a half of dialog.....and I'm probably just scratching the surface. I think you have to finally draw the line at the point at which the information ceases to be practical and useful, and becomes arcane over-kill. Yes, Jack is a wonderful, organic example of resistance in action :)
Uncle Doug, thanks so much for letting me into your workshop to hang out with you and Rusty and Jack. You've rekindled my interest in electronics again with your videos. I'm digging out my old AC and DC circuits books. I wish you had been my teacher when I was studying it!
You're welcome, James......you're always welcome in our workshop. It's great to hear that you're getting back into electronics. Keep us posted on your progress and projects.
This is golden, I am always been fascinated by tubes and always tried multiple times in creating amps and almost always had squealing and harsh trebles, I am going to try and put a grid stopper now! Thank you and ciao!
These vids are great, just successfully build a single channel Vibroverb, almost finished with a 6V6 Plexi and then going on to design an amp ground up for my "fretless Ebow guitar". I gutted my old amp to make a tube design station if you will. Your Jack reminds me of our new and 3rd cat, black as can be, probably asian. Very playful and atheletic. ha maybe a little too much! Thanks very much!
Fascinating stuff, well presented. Nothing else like this out there. My ambition to build my own amp is kind of dulled by showing how little I know about electronics
+Stephen Gent Thanks, Stephen. If you really want to build your own amp, then study all the available info you can find on the subject and develop a foundation of knowledge upon which to build. No one was born knowing this stuff.....we all had to start somewhere. Good luck.
Thanks for an informative lesson. I play lap steel guitar and find that most steels have very high output pickups. Especially the old horseshoe pickup Rickenbachers, of which I have several. My 70's Traynor amp heads have the same input circuit as the Fender and I always use the #2 input to keep from overdriving the first preamp tube. If I use the #1 input, I can't turn the volume up much past 1 or it's way too loud. Your video finally explains why I can hear a difference in the brightness between the two inputs as well. My blue heeler, Sparky, says to say "Hi" to Rusty. They have identical energy levels.
+jflimbach You're welcome, JF. Back in the "good old days" there definitely were applications for the low-impedance input, including the example you cited. Thanks for watching and for your input.
Uncle Doug, I am very grateful for your very easy and fun explanations. I wish I had an electronics teacher half as awesome as you in college. I discovered your videos while battling through dengue fever 🤒 lol , and resting it out in bed for a week. Greetings from this nephew in Tegucigalpa, Honduras.
Yes indeed! Your videos made my recovery much more tolerable. It seems you can only get dengue 4 times in a lifetime as there are only that amount of genotypes and one develops antibodies, so its one done and three to go 😂. Luckily yellow fever has been eradicated a long time ago over here but now we have zika and chikungunya for mosquitoes to transmit. Anyways I am using all this knowledge you are sharing to improve my troubleshooting skills in amp repair. Its so much easier when I could finally understand what components are doing in the amp. Lots of love for you, Jack and Rusty.
wish I could meet you and be your house servant for a week or so in return for helping you and learning.You are one of the best I have found On youtube
It would be nice to have a giant keg party for all our viewers and subscribers, Stu, but space would be an issue. If we ever figure out a way to do it, you will definitely receive an invitation :)
I was just thinking about the role of a grid stopper today, and this video pops up!… Either, RU-vid must've somehow read my mind, or you two, (you and Jack) must've read my mind from 8 years ago, and sent it forward… If that's even possible!… I think Jack might know the answer
Again, a much needed explanation. I have been unhappy with a slightly harsh and brittle sounding treble frequencies from both the Fender & Marshall style channels of my amplifier. I have the standard 1.5k grid stoppers on the four 6L6gc output tubes but may experiment with some larger values,( ie; 5.6k grid stoppers, a value used on Marshall EL43 tubes), to help eliminate some of these harsh frequencies.
The input capacitance of a pentode/tetrode is so small that increasing the grid stoppers will have no effect on frequency response. The input capacitance of a 6L6GC is around 25pF. 1.5k grid stoppers cut frequencies above approximately 4.2MHz and 5.6k grid stoppers would cut frequencies above approximately 1.4MHz. Way too high to affect the frequency response of the amp.
My cat Raisin, who looks just like Jack, really would fetch and return a small ball for my oldest son. He would toss it down the hallway and Raisin would bring it back and dump it at his feet. Raisin also liked to play with the rings from around under the cap of milk jugs. One of his favorite toys.
I wonder if it's a trait of black cats, Michael ? Leaking filter caps will create excessive current flow (to ground), overheated power transformer and rectifier, and general havoc. Unless there is a fuse to blow, a fire could result.
Appropos your remark below on how far to go in depth in these lessons, it's been my experience that the deeper you go the easier the subject matter is to remember. A complete understanding makes electronics (or anything) seem less like magic. So if your going to err then err on the side of comprehensiveness.
This video has come with great timing. I'm having to debug my homebuilt JTM 45 input circuits (blows the mains fuse when I jumper the inputs) and has helped with understanding how the various components interact. Havent fixed it yet but we'll get there. All thanks to Uncle Doug.
+Andy Wragg I wonder if jumpering the inputs may be allowing the strong input signal to overdrive the output tubes and cause them to draw excessive current. If you're using a current limiter and can get the amp to stay on with no signal, strike a chord and see if the bulb flares up.
I've been playing it jumpered in the last hour whilst running through the current limiter. I can see the current usage on the bulb. I'm normally quite an aggressive Strummer - we play a lot of pop punk in the band - and I can see this reflected in the bulb intensity. Thinking back to when I first jumpered the inputs, this was also the first time I ran the amp straight into the mains. I'll try a F2A fuse tomorrow and see if that changes things. I still can't find a problem with the wiring.
I assume that when un-jumpered, the bulb doesn't flare up as much when you play, and the fuse doesn't blow. It would appear that jumpered inputs will require a higher value fuse (i.e. 2A). Most of my push-pull amps tend to use 2A fuses to start with.
Uncle Doug, I'm the doing unthinkable- posting a comment on youtube. Your lectures are absolutely fascinating, getting to the working principles in a clear concise and easily understandable manner. If Jack or Rusty were ever out of work I'm certain you could sell this series on DVD to make up the shortfall. Like all your students I'm very grateful the three of you have taken the time to share your well honed knowledge and expertise with us. Best wishes from the UK. Dave
Great explanation of the Miller effect. I didn't realize how much of a difference the value of the grid stop resistor made on frequency. That explains why the two overdrive 12AX7 tube stages in my Ceriatone Overtone Special (Dumble clone) amp have 68K and 180K ohm grip stop resistors - to reduce the high frequencies.
+Tony Manns Thanks, Tony. Yes, since resistance is in the denominator of the frequency cutoff formula, it had an inverse effect on the cutoff frequency.....higher resistance = lower cutoff, and vice-versa.
+Edu "Turupá" Sánchez You're welcome, Edu. Like Pink Floyd said, each thing you learn is just "another brick in the wall" of knowledge. Glad the videos are helpful.
Thanks Uncle Doug, Rusty and Jack! I greatly appreciate your time, effort and knowledge that you guys share on this subject. I always look forward to watching your channel for the latest and greatest videos. Hello my name is Tyler, ..... and I'm an amp-o-holic!!!
+Tyler Pesta You're welcome, Tyler, and welcome to our channel. You're in good company. Just about all of us are confirmed ampoholics, and our 12-Step Program involves acquiring, restoring, repairing, and using every tube amplifier we can get our hands on :))
Been watching your interesting and entertaining videos for some years now. (I should qualify my opinion by adding that I also enjoy listening to Garrison Keillor. And having said that, have lost the reader for the next comment). So now that we're alone I can gush with impunity over this latest video installment. I've always avoided much thought about the deceptively mysterious Fender input circuit, except for the time I mixed up my 100 ohm virtual ground resistors and my 1meg ohm input resistors and experienced first hand the consequences. Now, thanks to your clear and clever video, another little but significant heretofore foggy corner of my amp understanding has begun to crystalize. Let me echo so many of your other commentors on a job well done.
Jack is so cool! I have a black named Echo. They are identical, even the eye color. It's like I'm watching Echo on your video. Echo likes a plastic spring(for cats) for retrieval, and wire ties. Gotta love the animals!
It's interesting that your (identical) cat also likes to retrieve items.....which is an unusual trait in cats. I wonder if that tendency is genetic in these black (Bengal) cats.
Hi Uncle Doug, this clarifies a few areas for me and will no doubt send me back out to the shed to experiment. All this talk of resistors reminds me of a time when my sister went to a car wreckers(auto salvage yard) and said, "I need a resistor!" And the fellow behind the counter said, "You can't have one", she sais, "why not?" And he said, "Well I'm resisting you aren't I!" Anyway, Jack looks like he's spoilt rotten:)
+charris939 Greetings, Colin.....glad the video was interesting. I think Jack studied at the same school as the counter man at your salvage yard. Like a spoiled kid (or very typical teenager) he tends to do exactly as he wishes. Fortunately, it's often rather amusing to watch.
Thank you So much Doug. Not only for making these very enjoyable videos. But making them to where I can understand what is going on with and around the the Vacuum Tube, I have learned a 100 times more than all the reading, I have done over the last 40 years. Much respect to you ! Molly is like Jack to a T Even the rolling thing. :) I didn't see Rusty and hope he is well. All my very best Doug. Can' wait till the next video. Bobby
+Bobby Tectalabyss You're welcome, Bobby. I'm glad the videos are clear and helpful. Rusty is doing fine, but I made this video in the house, where Jack lives, instead of the workshop, and he wanted to help out. Regards to Molly.
In the very early '70s, when I worked in General Aviation (small planes) avionics, a customer brought in a comm radio (from the 1950s) that had no receive audio. I identified the offending stage and started making voltage measurements around that tube. When I put the VTVM (11 megohm input resistance) on the grid the audio came back and stayed on a few seconds after I removed the probe. Shut the radio down, found the 1 megohm grid leak resistor was open. The grid was building up charge and shutting itself down. Never saw a grid stop resistor in my couple decades of tubes but I never worked on music preamps. In RF power amps - usually the home-brew types from my ham days - series resistors on the control grids were sometimes added to stop parasitic oscillations. Those oscillations were produced by plate to grid capacitance in power triodes. It is more common in power FETs in RF applications.
The grid stopper has multiple functions. In addition to stopping radio frequencies entering the input stage, they are used to prevent parasitic oscillation and to control blocking distortion.
I think the low impedance input is great for jazz playing where you sometimes want pristine clean sound. I use it quite often. I never knew all this though. Dangit those Fender engineers are literal geniuses.
Long time ago the people said... "The people are ignorante and don't now nothing, becouse don't had chances to acess the culture". The internet proves the oposite... The people stay ignorant becouse they want... Thank you Uncle Doug ,big hug.
Outstanding instruction Uncle Doug. So well taught that a low-grade surgeon like me can understand. I do have some feedback for you. I noticed that there have been about 43,000 views and 990 of those people rated your video with their electronic thumb. About 0.6% have thumbed you down. I'd like to help you remedy those scathing reviews so you can sleep tonight and no longer cry in the shower. My ideas are these: Drop your pants so that your underwear shows in the back, cuss a great deal more, discuss the Kardashians more frequently, give your opinions on a subject of which you have little knowledge. These are only a start, but I want you to have that 0.6 % back. One day soon, Sir, you'll build your self-esteem back.
Thanks so much for those helpful hints, JG. I was going to try some drunken clog dancing, but your suggestions seem far more appealing. Let's hope the elusive 0.6% will give me another chance :)
& if none of these ideas work, try this, hang a good sized photo of caitlyn jenner in the shop & once or twice an episode make a quick scan of the pic while your in process of highlighting some other ac/dc type stuff (!?). let that sink in for few weeks then next video, maybe have purple nails, next week get a shot of maybe lipstick tube on bench etc.. continue with this caitlyn-isms until thumbs go in the right direction.
Uncle Doug, I am not sure how often the problem of Grid Emission becomes severe enough to become noticeable in tube-type amplifiers, but it results from the cathode material (which is chosen to emit lots of electrons when it is heated) boiling-off of the cathode sleeve and then collecting onto the [nearby] grid structure. It is still exposed to some heat from the cathode, which tend makes the grid go somewhat positive. The tube will conduct more and more, going into thermal runaway, in severe cases.
Uncle Doug, I've never learned more about amps and electronics than from your crystal-clear video's ! There is one thing that confuses me in this Input Circuit schematic : the path taken by the "Input to Ground" shouldn't it rather be pointed from the grid towards the ground (instead of the jack input) ? I have trouble understanding these 2 different flows from the input jack, one to the grid and one to the ground.
The incoming signal has two pathways, Alex. Going to the pre-amp tube grid, or going to ground. You have to be sure the balance is correct or you will either overwhelm the tube (distortion) or "underwhelm" it (poor volume and tone).
Uncle Doug thank you ! I think I understand now : the less signal can go to ground, the more signal is allowed to the grid, thus results in more gain and vice versa. Makes all sense now.
As always, this is an excellent series of videos that's straightening me out on a lot of things. I'm nearly dangerous now! (Just traded a license of my synth software for an old analog 'scope too! Hameg HM-203.) Thanks Doug!
+Admiral Quality Thanks, AQ, and congratulations on your acquisition of an oscilloscope. If you don't already have an audio frequency generator, you will need to get one. Best of luck mastering the use of these instruments.....they can definitely streamline the diagnostic and "tune up" process.
+Uncle Doug Just got a Heathkit 3600 power supply 0 to 15V, 0 to -15V, 15/-15V AC, and 200 Hz to 20kHz square/sine signal generator from the same guy. Breadboard on it too. Also a logic learning project board. Mastertech Labs "Microlab 1" with all kinds of gonkulating goodies on it. Also has a proto breadboard on it. Okay, NOW I'm dangerous! :)
+Uncle Doug Will do! Current project is trying to figure out what's wrong with an old Casio CZ-230S mini-synth that doesn't power on (but speaker makes a thud when it's powered on and off so something's happening in there). www.vintagesynth.com/casio/cz230s.php
There's a little known 1992 movie starring Brad Pitt and Tom Skerritt called A Current Runs Through It, they forgot to touch upon on the subject of grid leak and grid stop resistors. Another +1 for Uncle Doug!
+kcrmson I watched it when it was still called "A River Runs Through It", which just shows how old I am. I chatted with Brad about the title and I'm glad they changed it to make it more relevant to my videos. He's an OK guy when he's away from Angelina :))
Thanks for the lessons Uncle Doug. I guess once you know, or know knowing the right questions to get an answer you want, its just fine detective work, in a manner of words.I know its not rocket science but, it seems about as complex to many of us just the same. :-)
thank you once again Uncle Doug. I am continuing to learn how my amplifiers work and why the parts I install give me what I want. I have a small suggestion. when you show the tube connections, can you put the PIN numbers on the diagram. I loose a little understanding in the video when we are talking grids, plates cathodes, anodes etc. thank you once again for your time. PS you are a great teacher. Bob
+starlingave You're welcome, Bob. We're glad the videos are helpful. I generally try to add the pin numbers to schematics, because I (like you) can follow the circuit better with them, but occasionally I forget to do so. Thanks for watching and posting such nice comments :)
+Uncle Doug I would be interested in hearing how the impedance of a stage affects the prior stage... I have heard that if the impedance is too low it can make the prior stage work too hard.
The only place that I'm aware of such an issue is with the output transformer, matching the high impedance tubes with the proper impedance speaker. Perhaps there is more information available with a Google search. Good luck.
Uncle Doug thanks again for great videos...I was hoping with this video you might address the noise produced by grid stoppers. What I have come to understand is that the resistors in the Fender circuit contribute to what is called Johnson noise, a characteristic white noise I believe. I my particular case I have a 67 Fender Deluxe reverb that sounds wonderful. But it has in my opinion too much white noise coming from the first preamp stage. When the volume is down the noise is still there just a bit and when I raise the volume it comes in pretty strong. If I short the first preamp stage grid temporarily at the point where the two 68k resistors meet by the input jacks the noise disappears obviously. If I pull either preamp tube the amp becomes super quiet so I feel the trouble has to be in the first preamp stage. Also removing other tubes for reverb and tremolo don't affect this noise. I have tried three sets of tubes with pretty much the same results. The noise is consistent in amplitude whether using the normal and vibrato channel. This led me to believe that the power supply 10K 1W resistors were noisy so I change those also (the old power supply electrolytics were change out months ago and their good) but this did nothing. I have changed the old leaky capacitors in the tone and bias circuits and I have changed the 100K plate resistors in the first two preamp stages. But I still have the noise. Today I substituted two brand new 68K grid stoppers in parallel to simulate what the input is with nothing plugged in and still the noise is there. I appreciate any advice you might have for this. Note that recent I built a new amp with very same input style except the grid stopper resistors were spec'd at 47K. This amp has virtually no noise in this first preamp circuit. So I am a bit stumped but optimistic that it can be fixed.
It seems to me that you have ruled out all the usual suspects, Tom. Are you using carbon resistors, or metal film? The metal films are generally quieter. That's about the best I can do, long distance and sight unseen. Best of luck.
I am using new carbon composition (not NOS)i which I know are a bit noisier but still this seems a bit more noise than other amps using the same type. I'll continue to play around with it. Thanks.
Try a new preamp tube, or try swapping the tube with one of the other similar tubes in the amp. If that doesn't help, then unless you actually need two inputs, remove the 68k grid stoppers and install a 10k metal film grid stopper resistor from the input jack and connect it close to the grid, preferably after the 1M grid leak as in Uncle Doug's hand drawn schematic which appears in the video at 2:15. You could connect the resistor using screened cable with its screen connected to ground at the input jack. Add a 680pF capacitor from grid to ground for r.f. rejection.
Thanks Uncle Doug! As always, very well explained! My understanding of my amps has improved exponentially since I've been studying your videos. Now if i could just work out why my previously, super reliable tweed twin is shorting out the minute I try to connect the rectifiers to the rest of the B+ circuit. OT gone bad maybe?
You're welcome, Jim. Two possibilities come to mind: The polarity of the electrolytics must be correct (generally - to ground), and one of them may have an internal short. The OT is a long shot......they rarely fail, and if they do, it's generally open not shorted.
Hi. (7:27) one manifestation of parasitic oscillation could be that the amp "shuts down"- ie: no audible signal gets through. It is operating, but putting out frequencies beyond the human range of hearing.
Hey Uncle Doug. Love your channel and your content. I'm a studio engineer but i'm trying my hand at building a tube amp.. I'd be completely lost if it weren't for your channel. So thank you, you deserve a youtube award. I have a question. After watching this video I looked up the capacitances of the tubes I'm using for my amp. I'm seeing 1.6 pf for the 12AX7 not 151pf. I know it's a minuscule difference as far as capacitance goes but it's pretty significant when using the low-pass formula from the previous video. My questions: Am I missing something or reading the datasheets wrong? and Am I obsessing over shit that doesn't matter? Did I hear "low-pass filter" and get too excited because it was something familiar to me? haha maybe so. Anyway, thanks again. Your channel is seriously among the best I've seen.. Cheers Uncle Doug!
The 1.6pF of grid to plate capacitance plus any stray capacitance is multiplied by the gain of the stage plus 1. This is known as the 'Miller Effect'. You can see a full explanation of the Miller effect and the calculation resulting in 151pF at: www.aikenamps.com/index.php/what-is-miller-capacitance
Hi Doug, another fantastic video, really enjoying the series. I wanted to ask a quick question if I may. Recognizing that the Grid Stopper and tube capacitance together form the components of a low pass filter, the arrangement seems to me is different than the analogy you make to the low pass filter. The capacitance of the tube is across the plate, not to ground as the filter is which to me suggests that any HF noise makes its way through the tube to the next stage, not away from the circuitry as in a filter arrangement. I am learning an immense amount from your video series and really enjoying them. Thanks so much. Laurence
You're welcome, Laurence. Filters can be used in different ways. If a low pass filter is connected to ground, it will allow the low frequencies to leave the circuit, thereby accentuating the high frequencies....as in a treble control. If, however the low pass filter is inserted in the signal path, it will have the opposite effect, allowing low frequencies to pass and blocking the high frequencies.....as in a bass control.
There is a capacitance between plate and grid and also between grid and cathode. There is a path to ground for the AC signal at the plate via those two capacitances in series and the low value cathode bias resistor to ground. The capacitance between plate and grid is multiplied by the gain of the stage due to a process known as the 'Miller Effect'. It's the total capacitance between plate and grid that forms the low pass filter in conjunction with the grid stopper.
A very interesting and thought provoking video Uncle Doug. Do you think Fender actually expected musicians to use Input #2 by itself when they came up with the design? In my previous analysis - I had always assumed that the Fender input circuit design was oriented to providing a relatively balanced input for the scenario of using BOTH inputs at the same time - and that the input characteristics of using input #2 by itself was just sort of an in-escapable consequence of that design ?? Consequently - With my 5E3 builds - I just used a single input and a 32K Grid Stop and a 1 Meg grid leak resistor !! Your thoughts ??
+Donald Filbert You could be right, Donald. Using #2 as a single input doesn't seem to make much sense, unless your input signal was too strong for #1.....and I can't picture that. Since most people use only a single input, your solution sounds good to me, with optimum grid stop and grid leak values.
The video surprises and reveals again! Just like a great teacher will!..... So, DOES each gain stage move the "Q" or bandwidth of the harmonics we hear.?....and at such (very high) frequencies!? Whew! shaping tone(z) and herding cats.....hmmmm... Mr. D, I tried a lot of great references and pricey tube amp "lesson" DVDs ----but I look forward to each presentation each weekend...thank you, thank you.
