There's so much speculation about the influence of chokes vs resistors, the results of this surprise me as well, but this is a very useful video, thank you.
this is a fantastic thing to test, though i'm wondering if some of the test conditions here didn't make it difficult to clearly hear key differences the choke can make. for example, a peavey 6505 is a decent amp for some uses, but it is far from ideal for testing this component, mostly i think because the power supply architecture using silicone rectifiers and larger filter caps doesn't allow a normal choke do the heavy lifting it's well suited for. also, piping a finished mastered song that's already had brickwall, volume-maximizing limiting applied is going to reveal the least of the choke's effect even if the amp were an ideal type for this experiment. for reference, the ideal setup in my estimation should be one with a modest tube rectifier such as a 5R4, with series resistance either before the rectifier's plates or after it's cathode's output, and with appropriate sized filter caps of say 10u-25u, and a choke of 5H-10H, and with an appropriate bleeder resistor at the end of the PI filter (not just for cap discharge, but because this also regulates the voltage somewhat), and the sounds put to the amp should be what the amp normally sees such as a guitar or turntable playing sounds with some intact dynamics. what we *should* be hearing in this sort of test is how the choke can make the entire amp seem to breathe and project the sounds organically and smoothly. like, it's hard to taste the water when you're drinking it from a firehose. you can still hear some of what's going on with the choke vs resistor, but i wouldn't expect any differences are going to even be audible on most systems. also the analyzer being set to 10s of smoothing means virtually no differences in the microdynamics (where the biggest differences will be present) can be seen visually. it's got to be tracking (i think) down to the 20-400ms range, or even 1second. it's a sort of dynamic effect similar to what vintage-style compressors do; these sound clips and their lack of dynamic range would make even a Fairchild 670's different settings hard to differentiate. the whole point of the choke is not just the virtue of it's own effects, but more importantly the synergy of its interaction with the PI filter's caps and the rectifier. this part of the amp is where most of the amp's unique sound originates. this setup we've got in this video is akin to putting a 900hp firetruck engine into a mack truck, and trying to feel how the response of the gas pedal changes depending on the type of hose the fuel pump is connected with. i would LOVE to hear this test done under some more favorable conditions. "A" for effort though. keep working on it!
I don't think you're gonna see much of a difference when playing metal on a cranked amp but as we saw on clean there starts to be difference. But could it perhaps give a bit more "attack" on cranked amp too? I mean resistance to sag, because it's an energy reservoir.
Was the amplifier loud enough? What is the DCR of choke and the replaced resistor? You need to measure the amplifier near the maximum power, when there's a significant screen current - that's were the difference might be. But we're still talking 'bout 20W 2x EL84 PA, not 100W 4x EL34 ;)
choke is hamond 156G with 300 ohms DCR to replace the stock 390R resistor. Amp was pretty loud, but far from maximum power. might try turning it up alot more tomorrow, will report on the results ;)
@@le0_fx if you want to hear a difference changing the choke on a 6505, you must first change the rectifier from silicone diodes to a tube rectifier such as a GZ34 or a pair of 5U4's in parallel, and also change the first two filter caps to no more than 10u-20u. you'd also want to relocate the output tube plate feeds just after the choke and add a small resistance (300~1000 ohms) between the plate and screen feeds. the modern high gain amp's Achilles heel is thoughtless design overkill. the effort to be loud enough on stage was achieved in the late 1960's, yet most modern amp "designers" are like traumatized vietnam vets who "never really came home", unknowingly sacrificing touch sensitivity and character in the name of loudness. today any amp over 15 watts is probably overkill (and a tremendous waste of money on tube costs).
Great video, I have replaced the resistors with a choke of equivalent resistance on two amps 1) Marshall dsl40c and 2) crate bv-120h. Both amps had more than 6 henries in the coke, due to the high resistance. The difference in tone was barley noticable on the Marshall. The difference in tone was was huge and in a positive way on the bv-120h. Both amps were significantly quieter after the choke install (no hiss with the gain high). I need to ask: did you mic a cabinet for this video or go though a reactive load box/PC interface? I bet if it was a cab with decent volume you'd hear what is happening. The coke needs to go to the plates of the preamp tubes and the screens of the power tubes in a push pull amp like in your video, the power going thru the coke can go other places too of course, but the aforementioned is where it adds it's benefits. Where did you add the coke? Also it seems the graphic eq was like dampened, there was no life in it, use your ear, not what your PC seems to think... There was some seriously low resolution on the screen capture on the video, I don't know if that is misleading you. Respectfully, Steve.
Hey Steve, I actually mic'd a real cab for this video, but all of the audio in this video was at rather low volume. Because someone else mentioned the volume-thing, which makes perfectly sense, I did the same again with rather high volume, but this made absolutly zero difference... The choke replaced the first series resistor right after the bridge rectifier of the main voltage supply. PT plate is unaffected, but Screen and all B+ voltages are. the slow reacting and smoothed EQ-plot was a choice I made, hoping the visibility of the results would be improved. I thought this should display any actual systematic difference in volume for any frequency range, and the visible results kinda match what I am able to hear - no real difference with or without a choke in the 6505mh. Really cool to hear that your crate amp reacts more audible to the choke! could it be due to a more saturating power amp? Greetings, L
One thing that came to mind after reading your reply was maybe Peavey did it right, and the choke wasn't necessary. I'm glad you did this to your amp before we all do it to ours. Fantastic findings friend, Rock! I have learned the hard way, you cannot significantly change the character/dynamics or tone of an amp with one or two simple mods. You have to like the amp you start with before modding it; if you don't, you're changing allot of things and it sometimes gets worse, not better after all is said and done.
@@amateurism1 haha i started modding my 6505mh thinking some minor changes would lead me far enough, but now, a few years later, i touched almost every single resistor and cap in the whole preamp and it's nowhere near the stock circuit anymore. cool to see you doing similar stuff on your channel!
@@le0_fx it makes sense to me that these amps would make it extremely hard to hear any differences made by modding components. the reason is stemming from the rectifier and power supply section. leave those as they are and you'll never hear small changes anywhere else in a modern high gain amp. if you ever get a chance to mess with a point-to-point wired tweed-era small combo amp, changing any one component will make a HUGE difference in entire amp's sound and feel, and this is i think down to how the whole circuit is operating in a more narrow and delicate window of balance, particularly with the rectifier and filter sections. there's a reason hifi snobs and audiophiles are so obsessed with low-power, triode driven tube amps with no global feedback, tube rectifiers and lots of iron; it's nothing to do with wattage or "headroom" (i defy you to find a guitar center employee who can define this term clearly btw). it's not even the speakers...it's that the bulk of modern high gain amplifiers are churned out by people who are snagging designs from amps with overbuilt power sections. and i want to say too, i'm a big fan of high gain guitar sounds. the issue i see arises from all the smashing of the dynamics that happens these days in a normal recording setup. it's simply not an environment friendly to a broad dynamic range. these factors are also why so many guitar players listen in horror as their sound just gets drowned and lost while playing with their band.
Replace the stock OT with ClassicTone 40-18020 or ClassicTone 40-18025 and then tell me the difference you've heard. Actually it's not the best amp to mod. It's already have pretty dry distortion grain and not all-tube signal path - transistor loop/phase inverter can't be bypassed.
The OT will make a difference for sure, because it's actually involved in the signals path, not just the power supply. But I'm surprised that there is so much talk about the effect of the choke, and it is so inaudible. And I don't see how those transistors and op-amps in the signal chain could be causing this. technically, there is nothing wrong with them and their audio quality.
Sadly, ClassicTone recently had to shut down operations, so they are no longer in business. The only stock left available is what their resellers have on the shelf.
So here is my test with the Big 6505 Sister (She is called Jacqueline btw.) ruclips.net/video/snKEnr_Lo6k/видео.html
I thought there is something wrong with me that could not hear any difference . Luckily you mentioned it at the end :D
What a great video, total hidden gem!
There's so much speculation about the influence of chokes vs resistors, the results of this surprise me as well, but this is a very useful video, thank you.
Nice, work man! No difference in tone. Just noise reduction as expected from a power supply component.
Very cool comparison! with choke sonds less compressed and more clean than resistor to my ears.
this is a fantastic thing to test, though i'm wondering if some of the test conditions here didn't make it difficult to clearly hear key differences the choke can make. for example, a peavey 6505 is a decent amp for some uses, but it is far from ideal for testing this component, mostly i think because the power supply architecture using silicone rectifiers and larger filter caps doesn't allow a normal choke do the heavy lifting it's well suited for. also, piping a finished mastered song that's already had brickwall, volume-maximizing limiting applied is going to reveal the least of the choke's effect even if the amp were an ideal type for this experiment. for reference, the ideal setup in my estimation should be one with a modest tube rectifier such as a 5R4, with series resistance either before the rectifier's plates or after it's cathode's output, and with appropriate sized filter caps of say 10u-25u, and a choke of 5H-10H, and with an appropriate bleeder resistor at the end of the PI filter (not just for cap discharge, but because this also regulates the voltage somewhat), and the sounds put to the amp should be what the amp normally sees such as a guitar or turntable playing sounds with some intact dynamics.
what we *should* be hearing in this sort of test is how the choke can make the entire amp seem to breathe and project the sounds organically and smoothly. like, it's hard to taste the water when you're drinking it from a firehose.
you can still hear some of what's going on with the choke vs resistor, but i wouldn't expect any differences are going to even be audible on most systems.
also the analyzer being set to 10s of smoothing means virtually no differences in the microdynamics (where the biggest differences will be present) can be seen visually. it's got to be tracking (i think) down to the 20-400ms range, or even 1second. it's a sort of dynamic effect similar to what vintage-style compressors do; these sound clips and their lack of dynamic range would make even a Fairchild 670's different settings hard to differentiate.
the whole point of the choke is not just the virtue of it's own effects, but more importantly the synergy of its interaction with the PI filter's caps and the rectifier. this part of the amp is where most of the amp's unique sound originates. this setup we've got in this video is akin to putting a 900hp firetruck engine into a mack truck, and trying to feel how the response of the gas pedal changes depending on the type of hose the fuel pump is connected with.
i would LOVE to hear this test done under some more favorable conditions. "A" for effort though. keep working on it!
I have an old 5150 that I had modded with a choke back in 2010, same thing happened, no change in tone but massive cut to background noise and hiss
Agreed choke has less noise, but otherwise identical.
I don't think you're gonna see much of a difference when playing metal on a cranked amp but as we saw on clean there starts to be difference. But could it perhaps give a bit more "attack" on cranked amp too? I mean resistance to sag, because it's an energy reservoir.
Was the amplifier loud enough? What is the DCR of choke and the replaced resistor? You need to measure the amplifier near the maximum power, when there's a significant screen current - that's were the difference might be. But we're still talking 'bout 20W 2x EL84 PA, not 100W 4x EL34 ;)
choke is hamond 156G with 300 ohms DCR to replace the stock 390R resistor. Amp was pretty loud, but far from maximum power. might try turning it up alot more tomorrow, will report on the results ;)
turned it up to channel volume 6 + master volume ~8, and there is still no difference between the choke and the resistor :(
@@le0_fx if you want to hear a difference changing the choke on a 6505, you must first change the rectifier from silicone diodes to a tube rectifier such as a GZ34 or a pair of 5U4's in parallel, and also change the first two filter caps to no more than 10u-20u. you'd also want to relocate the output tube plate feeds just after the choke and add a small resistance (300~1000 ohms) between the plate and screen feeds. the modern high gain amp's Achilles heel is thoughtless design overkill. the effort to be loud enough on stage was achieved in the late 1960's, yet most modern amp "designers" are like traumatized vietnam vets who "never really came home", unknowingly sacrificing touch sensitivity and character in the name of loudness. today any amp over 15 watts is probably overkill (and a tremendous waste of money on tube costs).
Great video, I have replaced the resistors with a choke of equivalent resistance on two amps 1) Marshall dsl40c and 2) crate bv-120h. Both amps had more than 6 henries in the coke, due to the high resistance. The difference in tone was barley noticable on the Marshall. The difference in tone was was huge and in a positive way on the bv-120h. Both amps were significantly quieter after the choke install (no hiss with the gain high).
I need to ask: did you mic a cabinet for this video or go though a reactive load box/PC interface? I bet if it was a cab with decent volume you'd hear what is happening.
The coke needs to go to the plates of the preamp tubes and the screens of the power tubes in a push pull amp like in your video, the power going thru the coke can go other places too of course, but the aforementioned is where it adds it's benefits. Where did you add the coke?
Also it seems the graphic eq was like dampened, there was no life in it, use your ear, not what your PC seems to think... There was some seriously low resolution on the screen capture on the video, I don't know if that is misleading you.
Respectfully, Steve.
Hey Steve, I actually mic'd a real cab for this video, but all of the audio in this video was at rather low volume. Because someone else mentioned the volume-thing, which makes perfectly sense, I did the same again with rather high volume, but this made absolutly zero difference...
The choke replaced the first series resistor right after the bridge rectifier of the main voltage supply. PT plate is unaffected, but Screen and all B+ voltages are.
the slow reacting and smoothed EQ-plot was a choice I made, hoping the visibility of the results would be improved. I thought this should display any actual systematic difference in volume for any frequency range, and the visible results kinda match what I am able to hear - no real difference with or without a choke in the 6505mh. Really cool to hear that your crate amp reacts more audible to the choke! could it be due to a more saturating power amp?
Greetings, L
One thing that came to mind after reading your reply was maybe Peavey did it right, and the choke wasn't necessary. I'm glad you did this to your amp before we all do it to ours. Fantastic findings friend, Rock!
I have learned the hard way, you cannot significantly change the character/dynamics or tone of an amp with one or two simple mods. You have to like the amp you start with before modding it; if you don't, you're changing allot of things and it sometimes gets worse, not better after all is said and done.
@@amateurism1 haha i started modding my 6505mh thinking some minor changes would lead me far enough, but now, a few years later, i touched almost every single resistor and cap in the whole preamp and it's nowhere near the stock circuit anymore. cool to see you doing similar stuff on your channel!
@@le0_fx it makes sense to me that these amps would make it extremely hard to hear any differences made by modding components. the reason is stemming from the rectifier and power supply section. leave those as they are and you'll never hear small changes anywhere else in a modern high gain amp. if you ever get a chance to mess with a point-to-point wired tweed-era small combo amp, changing any one component will make a HUGE difference in entire amp's sound and feel, and this is i think down to how the whole circuit is operating in a more narrow and delicate window of balance, particularly with the rectifier and filter sections. there's a reason hifi snobs and audiophiles are so obsessed with low-power, triode driven tube amps with no global feedback, tube rectifiers and lots of iron; it's nothing to do with wattage or "headroom" (i defy you to find a guitar center employee who can define this term clearly btw). it's not even the speakers...it's that the bulk of modern high gain amplifiers are churned out by people who are snagging designs from amps with overbuilt power sections. and i want to say too, i'm a big fan of high gain guitar sounds. the issue i see arises from all the smashing of the dynamics that happens these days in a normal recording setup. it's simply not an environment friendly to a broad dynamic range. these factors are also why so many guitar players listen in horror as their sound just gets drowned and lost while playing with their band.
Was there any improvement with hum? Was the amp more quite with the choke? Or no real difference....
Indeed there is an improvement, check the last clip! Low end noise is about 6dB quieter.
What's the value ofvthe R & wattage? Thanks
hey, original resistor was 390 ohms, 6 watts.
Replace the stock OT with ClassicTone 40-18020 or ClassicTone 40-18025 and then tell me the difference you've heard. Actually it's not the best amp to mod. It's already have pretty dry distortion grain and not all-tube signal path - transistor loop/phase inverter can't be bypassed.
The OT will make a difference for sure, because it's actually involved in the signals path, not just the power supply. But I'm surprised that there is so much talk about the effect of the choke, and it is so inaudible. And I don't see how those transistors and op-amps in the signal chain could be causing this. technically, there is nothing wrong with them and their audio quality.
Sadly, ClassicTone recently had to shut down operations, so they are no longer in business. The only stock left available is what their resellers have on the shelf.
@@southerner66 bummer.
Just sounds like a bunch of rubber bands to me. Tune your guitar.
Thx lol