Help with a possible mod on an Ibanez Tube King TK999US

[100 watt]

Just aquired an Ibanez TK999US. Did a tube swap & got it sounding a bit better (still gonna try some lower gain tubes) but was wondering if there are some other tweaks (aside true bypassing) that may be done.

 

Would like a little more "punch" on chords and a bit more on the bass side / make things "tighter"

 

Was also curious about either replaceing the zener diodes with LEDS (Ive done this on some pedals before & liked the results. Seemed a little less fizzy & to have a bit more "definition" .

 

Im not good with schematics. Here's a schematic for the TK999US.

 

http://www.dirk-hendrik.com/ibanez_tk999_us.pdf

 

What could be changed up in the EQ section to get a little more "oomph" out of the bottom end?

 

Which diodes are the clippers?

 

Any other thoughts on possible improvements would be appreciated.

[Mr.Grumpy]

There aren't any clipping diodes, all the diodes are either polarity protection (D3, D4) or to protect the TL072 op-amps from static discharge (D1A, D2, D5, D6).

[WRGKMC]

Best upgrade for an amp to get the tone and clarity is the speakers.

Higer SPL speakers will give you more headroomand let you run the amp with less gain.

[MadSkillzMan]

If you play with the following Caps:

 

C25A

C8A

C21 (your midrange cap)

 

You can shift what frequencies get rolled off/cut off. Your "bass" frequencies on the EQ right now are wide open and based on this circuit's EQ, and your Mid/Treble simply boost/cut off bass from the original signal, but HEY WAIT, the original signal is still there, the bass pot just turns up/down all the original frequencies. R32 and R33 help "smooth' them out. Adding a cap would let you isolate your mids/trebles from your bass...start with the usual guitar tone pot values.

 

I'm not seeing any clipping diodes here. This is an op-amp circuit.

 

C8A and R16 deal with rolling off and "smoothing" frequencies during the gain stage.

 

Look at u2.B (op amp). Below you have C9, at 47p and then VR1 500k for gain. You COULD add diodes here (in between the two) for a soft clipping, or, right at the output (make the clipping pair, then tie to ground) before the resistor which will add hard clipping. Or hell both! have at it man.

 

Dont mess with the Zeiners. Theyre to help isolate the op amps.

 

Whats the voltage of your adaptor for this? I'm just kind of eyeballing the whole thing right now, no math involved, hence why I'm saying play with it. Looking to me like another starved plate circuit, no massive voltage across the tube lol but, it will still make an impact on the tone. Just change ONE CAP at a time until your liking.

[100 watt]

 

If you play with the following Caps: C25A C8A C21 (your midrange cap) You can shift what frequencies get rolled off/cut off. Your "bass" frequencies on the EQ right now are wide open and based on this circuit's EQ, and your Mid/Treble simply boost/cut off bass from the original signal, but HEY WAIT, the original signal is still there, the bass pot just turns up/down all the original frequencies. R32 and R33 help "smooth' them out. Adding a cap would let you isolate your mids/trebles from your bass...start with the usual guitar tone pot values. I'm not seeing any clipping diodes here. This is an op-amp circuit. C8A and R16 deal with rolling off and "smoothing" frequencies during the gain stage. Look at u2.B (op amp). Below you have C9, at 47p and then VR1 500k for gain. You COULD add diodes here (in between the two) for a soft clipping, or, right at the output (make the clipping pair, then tie to ground) before the resistor which will add hard clipping. Or hell both! have at it man. Dont mess with the Zeiners. Theyre to help isolate the op amps. Whats the voltage of your adaptor for this? I'm just kind of eyeballing the whole thing right now, no math involved, hence why I'm saying play with it. Looking to me like another starved plate circuit, no massive voltage across the tube lol but, it will still make an impact on the tone. Just change ONE CAP at a time until your liking.

 

 

Im running it at 12 volts. the standard Ibanez 9v adapter sounded thin & fizzy. 12 sounds alot better. I'm tempted to try 18 volts (if it wont kill the pedal). Did a tube swap & it got better (subsituted a JJ's 12At7. Sounded better than the stock chinese 12ax7 & the Tung Sol reissue 12ax7 (too much gain).

 

I'll try messin with those caps. Thanks for the reply. Hard finding much info on the tk999us.

[MadSkillzMan]

I'd be leary of 18v, only cause i don't have the thing in front of me to be able to tell you for sure. I can't see the tube adding that much "gain" probably just more clipping. Heck try a 12AT7 if its too fizzy. Like i said, its starved plate, so your not getting true "tube sound" here, but, it does have an impact on the circuit.

 

Lemme know how these mods turn out. Like i said i was just eye ballin' it, so i'd be real curious how this works out for you.

[100 watt]

I'd be leary of 18v, only cause i don't have the thing in front of me to be able to tell you for sure. I can't see the tube adding that much "gain" probably just more clipping. Heck try a 12AT7 if its too fizzy. Like i said, its starved plate, so your not getting true "tube sound" here, but, it does have an impact on the circuit. Lemme know how these mods turn out. Like i said i was just eye ballin' it, so i'd be real curious how this works out for you.

 

so far, I just tried some caps across the mid & treble resistors. That helped alot. I may try some diffrent values on those before I change any caps out. Mine doesnt have the caps & resistors marked on the board, so Im gonna have to do some research to find out where some stuff if.

 

I'd like to get ahold of another one to experiment with. Preferably one in need of repair, or in rough shape. Perhaps add some switching options, etc to see what all it's capable of. Possibly make one more "metal" oriented. Either that, or make it where I can run it mixed with an "almost stock" one. (one to run all the time..the other as a boost).

 

As for now, if I can get just a little more "oomph" out of it, and clean up the drive just a hair (so I can turn the gain up more without it getting fizzly) , I'll be happy.

[Mr.Grumpy]

 

Im running it at 12 volts. the standard Ibanez 9v adapter sounded thin & fizzy. 12 sounds alot better. I'm tempted to try 18 volts ....

 

 

18 volts? I wouldn't do it. The power supply jack is connected directly to the tube heaters, which are designed to run at 12 volts, probably why it sounds better than 9 volts. 18 volts would be 150% of the design voltage, that could shorten the life tube.

[MadSkillzMan]

Im not so worried about the tube, as much as i am the rail voltages on the op-amps.

 

Im working on a dreaded engineering ethics paper for class (blah!) Ill take another gander at the schematic later. Like i said, try a 12AU7, they have higher headroom. Ill go through it again, we'll screw with a few feedback resistors. Possibly limit the voltage on the heaters so we can increase the rail voltage on the op amps...

 

Can you post me pics? maybe i can tell you which caps are which on the unlabeled ones.

 

Did you just put caps in parallel with existing? or did you remove 1 leg of a cap and solder the new one in?

 

You could add clipping diodes and add a switch to that, for your more metal pedal.

 

Wonder if i can "capture" these schematics and play with them in Multisim. (my SPICE software of choice) though i believe OrCAD does this better...would let me totally play with your pedal from a mathematical standpoint and give you the best options before you even tinker with it.

 

Out of curiosity, are you setup for recording at all? Id love to hear before/after clips. Especially cause im just sittin here lookin at the schematics..All that college education Hey if it comes out awesome i can modify these schematics and post for everyone.

[100 watt]

I just soldered the caps over the resistors

 

I'll TRY to get a pic of the guts to it when I get a chance. Been scouring for pics, but theres only a few that show up.

 

Yeah..the clipping diodes. I may add those. Maybe a mix of LEDs & germanium (thats what I put in my Boss SD1 mod)

 

feedback resistors... didnt think about that. I know th enegative feedback resistor in a Marshall amp can make big diffrences in tone / feel.

 

I'll see if I can get some pics.

 

 

No access to recording, other than my camera. A friend of mine has a studio I can use whenever I want, but Im saving that favor for when Ive got some stuff down that I want to record. (I havent been in a band situation since 06-07.

[MadSkillzMan]

I hear ya on the recording man. Dont sweat it. Was just curious to hear

 

If you add a cap in parallel right across your clipping diodes (and i mean a really really tiny one, like pf) you can "smooth out" some of the fizzyness in a pedal, especially useful for Germanium diodes.

 

Which marshalls specifically do you mention the feedback resistor for? i have an AVT50 sittin here i always liked. Havent had much time to be a musician due to college, but now that im sittin here eyein that thing up..maybe its time to find some schems n take 'er apart. Then again i have a vox cambridge 30 sittin in m basement in need of tracing and repair.

 

There is also op amp "Stacking" but ill have to get back to you on that. Might actually be what your looking for, might be too obnoxious. I can tell you changing out the op amps wil totally give the pedal completely different characteristics. Gotta look at response curves, rail voltages, etc etc.

[WRGKMC]

You can try 5751 tubes instead of the 12A versions.

It's what Stevie Ray and others used to clean up the preamp amp gain and get more punch.

http://tubedepot.com/5751.html

I used them in my Marshall Valvastate to clean up the crunch channel that sounded like dirt.

I'd use them in my Fender but my Blackface Bassman is clean enough as it is.

[Rick-enHrL]

Hi, can anyone help me with a problem? I want to try to run my tk999us off batteries. Is this possible? Thanks.

[ewizard]

Possible yes, but it won't run for long. The tube eats up a bit of current. It will single handedly run the battery dead within minutes.

 

To the OP I would try working with the EQ section slope resistor. That should be the 3k3 R34 resistor before the bass knob. The R1 4K7 resistor may also yield results. Usually the slope resistor will have more bass when you lower it. This design is a little different than your standard FMV tone stack, but check out http://www.duncanamps.com/tsc/index.html . Those two resistors form a voltage divider and will delegate how much goes to each part of the tone stack.

[schwa6970]

I have this same pedal and the jack for the power cord is broken. I hardwired a power supply to it for a while but it was really noisy and would really like to replace the power jack. If anyone could help with this- There is a yellow and black wire going from the pcb to the jack. Any thoughts on where each goes on a new power jack. I will probably be replacing the wires into the pcb as well because there isnt enough length to them to wire in a new jack. I dont want to replace it with an original as it really was a terrible jack and want to upgrade it to something that wont fall out if I look at it wrong.