ValveKing "JCM" mode using Volume Boost switch
Re: ValveKing "JCM" mode using Volume Boost switch
Check your solder connections!
Charlie
Gib LP Robot 2008 Met. Red, , 5E3 Build 2014
Fend Tele Dlx2010 SPL ED w/Tron Tune
3rd Build 6G3 Br. Deluxe Head 2018
VK 112 Web OT Rotary Swit. Bias Mod
Gret. G2622 P90s,G2655T, G5034, Pro Jet, Epi WildKat 2019
Gib LP Robot 2008 Met. Red, , 5E3 Build 2014
Fend Tele Dlx2010 SPL ED w/Tron Tune
3rd Build 6G3 Br. Deluxe Head 2018
VK 112 Web OT Rotary Swit. Bias Mod
Gret. G2622 P90s,G2655T, G5034, Pro Jet, Epi WildKat 2019
Re: ValveKing "JCM" mode using Volume Boost switch
i did, went and resoldered everything, made sure all my connections were where they were supposed to be, made sure my traces were indeed cut and making no connections, and finally i made sure that the rearmost terminal of the switch was severed clean and making no connection. it actually did take most of the cutting out disappear, but there is still faint presence of this almost "noise gate" type of sound between notes when quick picking or between power chords with muting in between...CharlieP wrote:Check your solder connections!
a rough example: the intro riffage to "dont damn me" by g&r has this annoying effect in between the notes when i play this song.
the only thing about how i did my jcm mod is the fact that i did not have an actual 750k set of resistors, therefore i had to splice a couple of resistors end to end to come up with totals right around 750k (give or take a 10k difference on the meter)... would this difference be the root of my annoying problem?
Re: ValveKing "JCM" mode using Volume Boost switch
Anyone? Help please!
- 65 SG
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Re: ValveKing "JCM" mode using Volume Boost switch
The resistor values are non critical. Look elsewhere.
I can't imagine what would cause this unless there is some sneak path for the signal. It could have to do with the different PCB layouts, I haven't studied the newer PCB traces (mine is the old layout so that's what the mod was written up based on).
Are you running it in Gain Boost mode, or not, when in JCM mode?
Does the original lead channel operation (with the Volume Boost switch pushed IN) seem normal?
I can't imagine what would cause this unless there is some sneak path for the signal. It could have to do with the different PCB layouts, I haven't studied the newer PCB traces (mine is the old layout so that's what the mod was written up based on).
Are you running it in Gain Boost mode, or not, when in JCM mode?
Does the original lead channel operation (with the Volume Boost switch pushed IN) seem normal?
Re: ValveKing "JCM" mode using Volume Boost switch
The normal mode works just like the vk always has, when I toggle the jcm mode on, it does that bs cutting out, but it is obvious that there is less gain like it is supposed to do, everything works aside from the noise gate type of cutting out.65 SG wrote:
Are you running it in Gain Boost mode, or not, when in JCM mode?
Does the original lead channel operation (with the Volume Boost switch pushed IN) seem normal?
Re: ValveKing "JCM" mode using Volume Boost switch
If you connect to resistors in series to get a higher value in an audio circuit, there is a very good possiblity that unwanted noise will be created. You should try to get as close as possible with just one resistor to reduce this noise. If the resisters are of poor quality this could also create a negative effect in the circuit. When i was first learning electronics I did the same thing took me forever to figure it out.
- 65 SG
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Re: ValveKing "JCM" mode using Volume Boost switch
good point; one or more bad solder joints could also provide a nonlinearity similar to a diode junction (google "cat's whisker" or "point contact diode" for info) and that could certainly produce a gating effect.
Since it was some months ago since his post, I wonder if sebwhite got it sorted out or not???
Since it was some months ago since his post, I wonder if sebwhite got it sorted out or not???
'03 SG Special, '08 LP Special DC, '60s Dano/Silvertone, Epi Moderne, Epi EB-0, '60s Telestar semi-hollow,
Classic 20 w/6V6 mod, much modded VK112, Windsor Studio combo, Transtube Envoy II, '61 Reverberocket
Classic 20 w/6V6 mod, much modded VK112, Windsor Studio combo, Transtube Envoy II, '61 Reverberocket
Re: ValveKing "JCM" mode using Volume Boost switch
65SG is this mod to a VK100Head i can remove R150 and C117 I choose not to remove R107 What will this due Thanks Strap327 Darryl
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Re: ValveKing "JCM" mode using Volume Boost switch
Why not remove it? Re-read the instructions and/or refer to the schematic. You MUST remove R107 from the board in order for the mod to work as described.
If you don't change the value of R107, the JCM mode will be a lot lower in volume than "VK" mode. That's all.
If you don't change the value of R107, the JCM mode will be a lot lower in volume than "VK" mode. That's all.
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Re: ValveKing "JCM" mode using Volume Boost switch
Hi, all, Just joined the forum, and would like to thank 65 SG for the great mod!!!
Ive had two peavey vk212's and now have the vk112. I did a bias mod that not only allows the current to be adjusted, but I added a balance pot as well. I have never really been happy with the O/D sound, but since completing your mod its like having a different amp!!! I just love the glass like clean that easily breaks into crunch as I wind up the volume on the guitar (Les Paul standard) If anyone is in any doubt as to whether or not to do it, I can only say, GO FOR IT!!!
A couple of things I would point out regarding safety are:-
(1) to ensure the high voltage capacitors are drained, turn on the power, wait a few mins to warm up, then turn ON the standby and turn OFF the mains switch. the valves (tubes) will continue to draw current until the heaters cool and will discharge the capacitors. Remove the power connector before working on the amp and remember to turn the standby OFF again before you next power up to prevent cathode stripping the valves.
(2) If you add 1ohm cathode resisitors to monitor the bias, these should be 3watt wire wound. If the O/P valve should develop a short, metal film or carbon resistors could burn out and leave the test point at a dangerously high voltage, you could get a shock or damage your meter if its set to measure a low voltage. Ideally the fuse should blow before the resistor burns out.
Once again, thanks for the info 65 SG
Ive had two peavey vk212's and now have the vk112. I did a bias mod that not only allows the current to be adjusted, but I added a balance pot as well. I have never really been happy with the O/D sound, but since completing your mod its like having a different amp!!! I just love the glass like clean that easily breaks into crunch as I wind up the volume on the guitar (Les Paul standard) If anyone is in any doubt as to whether or not to do it, I can only say, GO FOR IT!!!
A couple of things I would point out regarding safety are:-
(1) to ensure the high voltage capacitors are drained, turn on the power, wait a few mins to warm up, then turn ON the standby and turn OFF the mains switch. the valves (tubes) will continue to draw current until the heaters cool and will discharge the capacitors. Remove the power connector before working on the amp and remember to turn the standby OFF again before you next power up to prevent cathode stripping the valves.
(2) If you add 1ohm cathode resisitors to monitor the bias, these should be 3watt wire wound. If the O/P valve should develop a short, metal film or carbon resistors could burn out and leave the test point at a dangerously high voltage, you could get a shock or damage your meter if its set to measure a low voltage. Ideally the fuse should blow before the resistor burns out.
Once again, thanks for the info 65 SG
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Re: ValveKing "JCM" mode using Volume Boost switch
Hi, is this mod supposed to get rid of the clean channel? because my clean channel is gone. I'm certain I have followed the instructions perfectly. The only other mod I did while I had it open was change the LED from red to blue. I doubt that would have anything to do with my clean channel. Any ideas or is that the way it is?
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Re: ValveKing "JCM" mode using Volume Boost switch
Hi, no, your clean channel should still be there, check all your wiring again, check that if you unplug the footswitch that the clean/OD switch on the amp still works. Are you sure you cut the print next to the switch properly, and the pin is cut as shown? Just go over everything again and you will most likely find you've made a mistake. Ive done this mod to two VK112's and a VK212 with complete success.
Let us know how you get on, good luck
Let us know how you get on, good luck
Re: ValveKing "JCM" mode using Volume Boost switch
I picked up a VK112 today for $200. The clean channel alone is worth that much! Both the normal and 'bright' modes are great to my ears. I really like the Texture control too. I was surprised at how well it sounds at 'family-friendly' volumes.
The lead channels is (as everyone says) lacking in livelyness.
I got curious, and had a look inside, and it is indeed the version 1. Once I get some free time, I'll probably try this mod.
The lead channels is (as everyone says) lacking in livelyness.
I got curious, and had a look inside, and it is indeed the version 1. Once I get some free time, I'll probably try this mod.
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Re: ValveKing "JCM" mode using Volume Boost switch
So I did this on my mesa modded VK 112 today. Not gonna lie, I'm a little underwhelmed. I think that is because I have already done the mesa mod and that impacts the character of the distortion a great deal. I removed C117 and put 470pF in for C149. The mesa mode really just sounds like a slightly thinner version of the JCM mode- doing the switch literally just adds bass from what I can tell. Did I do something wrong, or is this what it is supposed to be like?
Recall that the Mesa mod means that I've gotta take out R122, so gain boost is always on- maybe that's why. Also, I used a 1M resistor and a ~500k resistor. the 500k bridged the channel switch, and the two channels are of roughly equal volume, though both are quite loud!
edit: I'm gonna double check my work tomorrow and make sure I didn't forget to remove a resistor or something. Pretty sure I did everything right though. Honestly it currently does feel slightly like it's still doing a volume boost and thats all lol.
Recall that the Mesa mod means that I've gotta take out R122, so gain boost is always on- maybe that's why. Also, I used a 1M resistor and a ~500k resistor. the 500k bridged the channel switch, and the two channels are of roughly equal volume, though both are quite loud!
edit: I'm gonna double check my work tomorrow and make sure I didn't forget to remove a resistor or something. Pretty sure I did everything right though. Honestly it currently does feel slightly like it's still doing a volume boost and thats all lol.
Re: ValveKing "JCM" mode using Volume Boost switch
Success! Thanks 65 SG! My $200 amp just got a whole lot better.
I managed to complete Phase 1 of this mod without killing myself or the amp!
Does it sound like a JCM? I have no idea.
Both Lead channel modes sound much better than the old sound. MUCH better. I'll have to wait until tomorrow before I can really crank it up, but at low volumes it really sounds nice. I dig the JCM mode with just a dash of the gain knob a lot.
Pics or it didn't happen!
I'll do Phase 2 next time I get my hands on a 750k resistor and a few minutes of non-playing time.
I managed to complete Phase 1 of this mod without killing myself or the amp!
Does it sound like a JCM? I have no idea.
Both Lead channel modes sound much better than the old sound. MUCH better. I'll have to wait until tomorrow before I can really crank it up, but at low volumes it really sounds nice. I dig the JCM mode with just a dash of the gain knob a lot.
Pics or it didn't happen!
I'll do Phase 2 next time I get my hands on a 750k resistor and a few minutes of non-playing time.