Jase01 wrote:Just tried to bias my new "Matched" TAD str EL84's from the TubeStore.com and one reads 22ma and the other is 18ma? WTF? I did it using the method in the video on the last page, have I fucked up or are these tubes haywire?
Put my JJ's back in and there's less than 1 difference... Looks like they're staying there.
I am guessing those new tubes aren't as matched as they claim. My stock tubes had a difference of 8mA...One would read 20mA while the other just a hair above 12mA. The new tubes I bought are Mesas (tested and matched) and they are less than 1mA apart in readings (20mA and 19.2mA)...If it is the video I think it is I am the one who posted it on the last page. I am using the same method and Jay had confirmed it is indeed the correct way to bias these amps using a DMM. If your new tubes are off 4mA then I would suggest trying to return them for another set or trying a different brand all together. Why did you try to replace the JJ's anyway? Not the sound you were looking for?
No real reason, just experimenting that's all, I liked the description Just disappointed that the store made all these claims and even charged me extra! I live in a small town in rural Australia and have no access to any stores, even electronic ones, everything I buy is ordered over the net, even things like resistors and caps. It's just frustrating getting excited about mods and then having to wait for parts!..... Sorry, just my little cry for the day. haha
Jay wrote:Well, if you want a little more gain, try putting a 1uF cap in parallel with R4. You can also put it on a switch for when you don't want the extra boost. A lot of the 20H guys do that and get really good results. If you need more after that, we can do some more stuff.
For the NFB resistor switch, was that just ther XL mod for the Hotrods and Lead60?
Thanks I'll try that. Do I use a dpdt switch? And do I just solder the cap to the switch and run wires from R4 to the switch? ( could you please do a simple diagram?)
Not sure about the NFB mod, it was suggested as an alternative to a switchable slope mod, but I was thinking of doing both.
Oh yeah, whats the best type of capacitor to use?
I'll try and do a simple diagram. Give me some time to find/make a decent illustration though. lol
A 2 position DPDT will work. As for caps, you can use a 63v or 100v cap. I'm going to use the Vishay/Roederstein MKT1813 for my next build, or you can try the Vishay MKT368, which is very comparable to what the SLO uses. A good "poly" type will be your best bet.
Okay, try this. I hope this diagram works for you. It's my first time doing an illustration. Don't laugh. You want the capacitor to have a voltage reference, or you will get popping when you switch it on or off.
Cheers for that!! Is it pin 3 or 8 for the cathode?
Whats the value of the resistor?
R4 should be a 2.2k resistor.
Should it come from V1? I was looking at the 22h schematic and it looks like R4 is tied to V1. By the way, nice diagram!
This is from the HC forum "For the 22H, I recommend to change the stock 47k NFB resistor (at 8 Ohm) by a 56k (or 68k - just check it out). With 56k, you will get quite the same NFB as the stock 39k (at 16 Ohm) on the 50H/100H/100HDM.
It's really a good improvement to do that. The amp gets less "wooly" and "flubby" sounding, a bit more aggressive - think of going a step further in Mesa Rectifier direction."
Any help to make this switchable would be awesome (another cool diagram? haha?) I can't seem to find this NFB resistor on the schematic.. Help.
Jay wrote:Well, if you want a little more gain, try putting a 1uF cap in parallel with R4. You can also put it on a switch for when you don't want the extra boost. A lot of the 20H guys do that and get really good results. If you need more after that, we can do some more stuff.
For the NFB resistor switch, was that just ther XL mod for the Hotrods and Lead60?
Thanks I'll try that. Do I use a dpdt switch? And do I just solder the cap to the switch and run wires from R4 to the switch? ( could you please do a simple diagram?)
Not sure about the NFB mod, it was suggested as an alternative to a switchable slope mod, but I was thinking of doing both.
Oh yeah, whats the best type of capacitor to use?
I'll try and do a simple diagram. Give me some time to find/make a decent illustration though. lol
A 2 position DPDT will work. As for caps, you can use a 63v or 100v cap. I'm going to use the Vishay/Roederstein MKT1813 for my next build, or you can try the Vishay MKT368, which is very comparable to what the SLO uses. A good "poly" type will be your best bet.
Okay, try this. I hope this diagram works for you. It's my first time doing an illustration. Don't laugh. You want the capacitor to have a voltage reference, or you will get popping when you switch it on or off.
Cheers for that!! Is it pin 3 or 8 for the cathode?
Whats the value of the resistor?
R4 should be a 2.2k resistor.
Should it come from V1? I was looking at the 22h schematic and it looks like R4 is tied to V1. By the way, nice diagram!
This is from the HC forum "For the 22H, I recommend to change the stock 47k NFB resistor (at 8 Ohm) by a 56k (or 68k - just check it out). With 56k, you will get quite the same NFB as the stock 39k (at 16 Ohm) on the 50H/100H/100HDM.
It's really a good improvement to do that. The amp gets less "wooly" and "flubby" sounding, a bit more aggressive - think of going a step further in Mesa Rectifier direction."
Any help to make this switchable would be awesome (another cool diagram? haha?) I can't seem to find this NFB resistor on the schematic.. Help.
Oh! You're right. R4 is on V1. Sorry, I wasn't sure if it's V1A or V1B.
As for the NFB resistor, thats R42 on the 22H. And here's a diagram.
Unsolder one side of R42. Solder the 56k or 68k resistor onto the remaining leg of R42. connect some wire lengths to the two resistors and solder them to the outside lugs of a SPDT or one side of a DPDT switch. Solder a wire to the center lug of the switch and solder it to the open hole of where R42 was. Switchable NFB. If you did the Depth mod, you can also replace that pot with one of a similar value, but get one with a push/pull, so you can keep it stealthy.
Jay wrote:Well, if you want a little more gain, try putting a 1uF cap in parallel with R4. You can also put it on a switch for when you don't want the extra boost. A lot of the 20H guys do that and get really good results. If you need more after that, we can do some more stuff.
For the NFB resistor switch, was that just ther XL mod for the Hotrods and Lead60?
Thanks I'll try that. Do I use a dpdt switch? And do I just solder the cap to the switch and run wires from R4 to the switch? ( could you please do a simple diagram?)
Not sure about the NFB mod, it was suggested as an alternative to a switchable slope mod, but I was thinking of doing both.
Oh yeah, whats the best type of capacitor to use?
I'll try and do a simple diagram. Give me some time to find/make a decent illustration though. lol
A 2 position DPDT will work. As for caps, you can use a 63v or 100v cap. I'm going to use the Vishay/Roederstein MKT1813 for my next build, or you can try the Vishay MKT368, which is very comparable to what the SLO uses. A good "poly" type will be your best bet.
Okay, try this. I hope this diagram works for you. It's my first time doing an illustration. Don't laugh. You want the capacitor to have a voltage reference, or you will get popping when you switch it on or off.
Cheers for that!! Is it pin 3 or 8 for the cathode?
Whats the value of the resistor?
R4 should be a 2.2k resistor.
Should it come from V1? I was looking at the 22h schematic and it looks like R4 is tied to V1. By the way, nice diagram!
This is from the HC forum "For the 22H, I recommend to change the stock 47k NFB resistor (at 8 Ohm) by a 56k (or 68k - just check it out). With 56k, you will get quite the same NFB as the stock 39k (at 16 Ohm) on the 50H/100H/100HDM.
It's really a good improvement to do that. The amp gets less "wooly" and "flubby" sounding, a bit more aggressive - think of going a step further in Mesa Rectifier direction."
Any help to make this switchable would be awesome (another cool diagram? haha?) I can't seem to find this NFB resistor on the schematic.. Help.
Oh! You're right. R4 is on V1. Sorry, I wasn't sure if it's V1A or V1B.
As for the NFB resistor, thats R42 on the 22H. And here's a diagram.
Unsolder one side of R42. Solder the 56k or 68k resistor onto the remaining leg of R42. connect some wire lengths to the two resistors and solder them to the outside lugs of a SPDT or one side of a DPDT switch. Solder a wire to the center lug of the switch and solder it to the open hole of where R42 was. Switchable NFB. If you did the Depth mod, you can also replace that pot with one of a similar value, but get one with a push/pull, so you can keep it stealthy.
Hope this helped.
~Jay
You my friend are my hero! Does it matter which leg? and where does C22 come into it? Sorry for my Stupidity.
JCA 100H JCA 5212RC (converted in stack) Blackstar Serie one 2x12 Gibson Les Paul DC Pro Musicman Luke II Limited Edition Fender Stratocaster 1964 Fender Telecaster Richie Kotzen Signature PRS CE 24 Charvel Pro Mod Wild card SR Guitars Les Paul Custom Valley Arts Strat
Jase01 wrote:You my friend are my hero! Does it matter which leg? and where does C22 come into it? Sorry for my Stupidity.
Technically it doesn't matter which leg. And C22 was just for reference. On side of R42 goes towards the OT for the feedback signal, and the other side of R42 goes towards the phase inverter, which C22 is in that junction.
It's not a stupid question, either. We're all here to help each other with this.....um....sickness. haha.
I haven't noticed any changes in 'tone' per se, but it has become just a little clearer, and a touch more aggressive/ballsy. I don't notice added gain, but rather a slight increase of definition, so I'm able to back off the gain from where I normally have it (currently at noon, usually at 6).
I have to tell myself beforehand that I'm not going from a Fender Twin into a Mesa Triple Rec, so the noticeable changes will be slight, if any. Having said that, the changes and time spent are well worth it. Also, I redid the depth mod and just de-soldered the two spliced wires and ran a single wire on each side of the pot. I'm glad I have a little OCD because it will help with build quality when I eventually start doing it full scale.
My biggest obstacle so far, is how in the world do you join multiple wires to one solder joint? It's hard enough to keep one wire from moving on you when soldering it, but more than that is proving to be a hell of a challenge to a novice like me.
Resident thread killer
I know nothing
Sterling AX40 x3 PRS SE245, SE Paul's Jet City amps - all of them modded 2204s Bogner XTC 3534 Kemper rack
OCD for the win. It definitely helps. I suffer from it as well.
What kinds of solder joints are you referring to? When I solder a wire to a wire, I always wrap the wires around each other first, like when you cross you laces as you tie your shoes.
The 4 ohm jack, for example. There are 3 wires leading to it - one from the OT, one from the NFB, and one that connects it to the other 4 ohm jack. I de-soldered the NFB wire to send to the depth pot, and instead of re-soldering the return to that same jack I just soldered it to the other 4 ohm output, since it's in parallel (right?)
Resident thread killer
I know nothing
Sterling AX40 x3 PRS SE245, SE Paul's Jet City amps - all of them modded 2204s Bogner XTC 3534 Kemper rack
sahlomonic wrote:The 4 ohm jack, for example. There are 3 wires leading to it - one from the OT, one from the NFB, and one that connects it to the other 4 ohm jack. I de-soldered the NFB wire to send to the depth pot, and instead of re-soldering the return to that same jack I just soldered it to the other 4 ohm output, since it's in parallel (right?)
Thank you very much for helping this guy with the nfb resistor thing. I haven't seen it sooner.
To get an idea of how the nfb works, you could also try to unsolder the nfb wire - just to hear the difference. Without nfb, the amp will be a lot louder and goes into direction of mesa rectifier in modern mode.
To find out, which nfb suits your personal taste most, you could also use a pot instead of a resistor and turn it until you like the sound best, then unsolder the wires and check the value at this point with a dmm. Then put in a resistor with this value. Just an idea. : )
Jay wrote:This one is what I used for my SLO Clones and a few other projects.
Can you get some measurements for me? Body diameter, shaft diameter, smooth or knurled shaft?
It appears the JCA100H pots are the latter of the two:
The pots you referenced a couple posts above are the same size as what I usually buy, but that requires drilling a larger hole and a bigger footprint on the chassis (made the depth mod a fine challenge shoehorning that thing between the chassis panel and the capacitor!)
Resident thread killer
I know nothing
Sterling AX40 x3 PRS SE245, SE Paul's Jet City amps - all of them modded 2204s Bogner XTC 3534 Kemper rack
That pot looks perfect. If I recall, the Alpha minis have those dimensions: 16mm body and 8mm shaft.
I would want to see the board up close to check into the loop bypass, but I would be thinking that those 3 wires would be better off staying on the board. I'm thinking that the cable is shielded somehow.
Welp, I completed the Brown Eye mod...and it frigging works. I hooked up the preamp gain pot backwards though (easy fix).
On super low volumes it definitely sounds like a hotrodded Marshall. I will do a write up with pics and stuff. It won't be that detailed though because I just got tired of jerking with my camera.
VERY complicated mod though. Not as easy as swapping out a resistor or two.
Jay wrote:Well, if you want a little more gain, try putting a 1uF cap in parallel with R4. You can also put it on a switch for when you don't want the extra boost. A lot of the 20H guys do that and get really good results. If you need more after that, we can do some more stuff.
For the NFB resistor switch, was that just ther XL mod for the Hotrods and Lead60?
Thanks I'll try that. Do I use a dpdt switch? And do I just solder the cap to the switch and run wires from R4 to the switch? ( could you please do a simple diagram?)
Not sure about the NFB mod, it was suggested as an alternative to a switchable slope mod, but I was thinking of doing both.
Oh yeah, whats the best type of capacitor to use?
I'll try and do a simple diagram. Give me some time to find/make a decent illustration though. lol
A 2 position DPDT will work. As for caps, you can use a 63v or 100v cap. I'm going to use the Vishay/Roederstein MKT1813 for my next build, or you can try the Vishay MKT368, which is very comparable to what the SLO uses. A good "poly" type will be your best bet.
Okay, try this. I hope this diagram works for you. It's my first time doing an illustration. Don't laugh. You want the capacitor to have a voltage reference, or you will get popping when you switch it on or off.
Just double checking. Does this apply to the crunch channel on my 22h or the OD channel? Also, is there a way to make the presence control on the 22h more responsive?
Jay wrote:Well, if you want a little more gain, try putting a 1uF cap in parallel with R4. You can also put it on a switch for when you don't want the extra boost. A lot of the 20H guys do that and get really good results. If you need more after that, we can do some more stuff.
For the NFB resistor switch, was that just ther XL mod for the Hotrods and Lead60?
Thanks I'll try that. Do I use a dpdt switch? And do I just solder the cap to the switch and run wires from R4 to the switch? ( could you please do a simple diagram?)
Not sure about the NFB mod, it was suggested as an alternative to a switchable slope mod, but I was thinking of doing both.
Oh yeah, whats the best type of capacitor to use?
I'll try and do a simple diagram. Give me some time to find/make a decent illustration though. lol
A 2 position DPDT will work. As for caps, you can use a 63v or 100v cap. I'm going to use the Vishay/Roederstein MKT1813 for my next build, or you can try the Vishay MKT368, which is very comparable to what the SLO uses. A good "poly" type will be your best bet.
Okay, try this. I hope this diagram works for you. It's my first time doing an illustration. Don't laugh. You want the capacitor to have a voltage reference, or you will get popping when you switch it on or off.
Just double checking. Does this apply to the crunch channel on my 22h or the OD channel? Also, is there a way to make the presence control on the 22h more responsive?
This mod is just for the crunch channel.
To make your presence more responsive, you can change the 25k pot to a 10k. In my SLO clones, I preferred the 10k over the 25k by a long shot.
