Just bought a vox pathfinder 10 and I was wondering what sort of mods you can do on these. I will be cutting the led or use a switch to go from different diodes to bypass, but I’m sure there must be more. I have heard somewhere that more watts is possible by changing the op amp, is this true?
When searching for mods of the amp the bencraven site seems to have some information, the diystompboxes and music-electronics-forum forums for some more (pathfinder 15). I read about the increase in power from 15W to 20W, if that is the only power gain it is not all that much of an increase. If from 10W to 20 then maybe worthwhile. Here is the schematic. Also tdpri form has stuff on it.
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Thanks for the replies. All makes sense now.
If I wanted to get the most out of the op amp swap, what transformer would I need? What would stacking op amps achieve (this is something I like doing to some pedals)?
Also, what could I do about the speakers in the cab? Would it fit a larger speaker, or maybe I could make a new baffle for two 6.5” speakers?
This is a pathfinder 10 by the way.
If I wanted to get the most out of the op amp swap, what transformer would I need? What would stacking op amps achieve (this is something I like doing to some pedals)?
Also, what could I do about the speakers in the cab? Would it fit a larger speaker, or maybe I could make a new baffle for two 6.5” speakers?
This is a pathfinder 10 by the way.
Forget modding the amp, even if you double the power output it will only give you a 3dB increase in loudness. A more efficient speaker, or a larger speaker, or multiple speaker drivers will make getting you what you want a lot cheaper, and easier too.
Mike
Thanks for the replies.
What is the maximum watts I could get out of this amp? Would getting a big transformer with stacked op amps achieve this?
I suppose I could get another cab, but I like the idea of also having a good little combo setup so I think I’m going to try to squeeze in another speaker by making another baffle, maybe out of very thin spruce? What are some good 6” speakers?
What is the maximum watts I could get out of this amp? Would getting a big transformer with stacked op amps achieve this?
I suppose I could get another cab, but I like the idea of also having a good little combo setup so I think I’m going to try to squeeze in another speaker by making another baffle, maybe out of very thin spruce? What are some good 6” speakers?
Obvious error around U1a.
If this amp isn't big enough, trade-in on a bigger amp. You can't reasonably mod a Malibu into a Corvette. Put in a bigger engine and bust the gearbox. Put in a bigger gearbox and you can't keep the tires from spinning. Bigger tires and moving everything to get the weight on them.... you can buy a dented 2001 Vette for less time trouble and cash. Same in amplifiers.
Leave Pathfinder as-is and build a *guitar* powered cabinet, you´ll need:
* 1 power amp module. An LM1875 will add 20/25W RMS ; a TDA7294 or LM3886, from 60 to 80W RMS
* 1 Guitar speaker (Jensen Mod are excellent and very reasonable price) . Must match or surpass power amp rating.
* buy/build/beg/modify a cabinet to mount everything.
From unpainted chipboard to modified IKEA flowerpot to hole-cut-in-luggage to dead amp cabinet to custom build oiled walnut (whatever carpenter GrandPa can lovingly build
)
Then you drive it from your little Vox ... same sound and distortion but at smashing loud output ... and way fatter.
this one is battery powered:
nothing new under the Sun, this is how *old* Gibson amoplifiers (think 1940s) used to be built:
* 1 power amp module. An LM1875 will add 20/25W RMS ; a TDA7294 or LM3886, from 60 to 80W RMS
* 1 Guitar speaker (Jensen Mod are excellent and very reasonable price) . Must match or surpass power amp rating.
* buy/build/beg/modify a cabinet to mount everything.
From unpainted chipboard to modified IKEA flowerpot to hole-cut-in-luggage to dead amp cabinet to custom build oiled walnut (whatever carpenter GrandPa can lovingly build
)Then you drive it from your little Vox ... same sound and distortion but at smashing loud output ... and way fatter.
this one is battery powered:
nothing new under the Sun, this is how *old* Gibson amoplifiers (think 1940s) used to be built:
Vox pathfinder R8 mod headroom issue?
Yesterday day I performed the led and the R8 mod on my pathfinder. I am happy with the sound but I think maybe the R8 mod has lost some headroom? It might not have, but if (on the clean channel) I have the volume set to 3 o’clock and the gain at 12 o’clock, there is a fair amount of overdrive, I think it is mainly coming from the power amp as when the volume is lower it doesn’t distort. What ways could I increase headroom? Would stacking the op amp work?
Yesterday day I performed the led and the R8 mod on my pathfinder. I am happy with the sound but I think maybe the R8 mod has lost some headroom? It might not have, but if (on the clean channel) I have the volume set to 3 o’clock and the gain at 12 o’clock, there is a fair amount of overdrive, I think it is mainly coming from the power amp as when the volume is lower it doesn’t distort. What ways could I increase headroom? Would stacking the op amp work?
You've already said it: instead of clipping in the LEDs you're now clipping an OP amp, which (usually) sounds worse, hence "less headroom".
Not sure where R8 is: the schematic posted earlier is postage stamp sized on the useragent-du-jour.
I've got a 15R which is going to get a center-off DPDT for the LEDs: one position they'll be in; center position will be no limiter; and position three will be an asymmetric and (initially) soft limiter. Still messing around with values.
While it's apart I'll also add the boost bypass pot,
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It's all relative, if you modify R8 to increase the overall preamp gain at that stage then of course it will distort at an earlier gain pot setting.. in this case 12 o'clock There is the tone stack and then another op amp stage where it (and possibly the TDA) are starting to distort. So you may need to play around with a value of R8 that will start distorting at high gain pot setting. Possibly ending up where you have close to the original value. Stacking op amps won't help if that is what you refer to. More output watts means either a BTL power amp or just build a bigger power amp with bigger power supply) like many suggested and keep the preamp as original.
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