Vox Pathfinder mods

[role_65]

Help

Hi Rob,
I own a Pathfinder 15R, and I agree it's great value for the money, still, I couldn't keep myself from performing some mods.

I replaced the original op-amps with 5532s ( and it did help in lowering the noise, are you sure your 5532s are not crappy chinese fakes? ) and added DIP sockets for a quick replacement, but as a matter of fact I did the major mods on the PS and PA sections.

I replaced the original PT with a toroidal PT, with a slightly higher voltage and a better current rating, then I changed the rectifier to a 4 Amp bridge, this allowed me to increase the filter capacitors' value ( to improve the dynamic range ). I also added voltage regulators for the preamp section ( to avoid early clipping on the op-amps due to voltage drops when the amp is driven hard ).

I substituted the output chip - seems to me it was a TDA 2030 - with a TDA2040 and changed the original 8" speaker, putting in a 10" Celestion I salvaged from a wrecked Cambridge 30.

Hope this helps

Best regards

Bob

Bob
Do you have a part # for the PT. I 'm gonna use the 2050 but was unsure about the appropriate Pt i know you suggest 50W any advice appreciated. I'm kinda/ somewhat new to the Mod thing my dad has an electro/mechanical degree and helps alot if i get in trouble. It's sad for a 28 year old to have to call dad when a circuit keeps faulting lol...I also was wondering did the OP amps help smooth the "breakup" out, or just reduce some minor noise? thanks
Ryan

PS did this do anything to the sound, or just amplify it?

[role_65]

hmm

Is it Toroidal # 707.062 a 56 watt PT. Also is there any other brands?
Ryan

[Robert M. Martinelli]

Bob
Do you have a part # for the PT. I 'm gonna use the 2050 but was unsure about the appropriate Pt i know you suggest 50W any advice appreciated. I'm kinda/ somewhat new to the Mod thing my dad has an electro/mechanical degree and helps alot if i get in trouble. It's sad for a 28 year old to have to call dad when a circuit keeps faulting lol...I also was wondering did the OP amps help smooth the "breakup" out, or just reduce some minor noise? thanks
Ryan

PS did this do anything to the sound, or just amplify it?

Hi Ryan,
I used an Italian-made transformer, so I don't think its P/N could be of any use.

The original output IC (TDA2030) calls for a +/- 18V supply, and therefore a 13-0-13 VAC (25/30VA) transformer is adequate.

If you move to a TDA2040, you need +/- 20 V, so a 14-0-14 VAC (40VA) transformer will be OK.

If you plan to use a TDA2050 instead, it calls for a +/- 25V supply, so you will need a 17.5-0-17.5 VAC (50VA) transformer (18-0-18 is still OK).

The main improvement I had using different op-amps (5532s) was about noise reduction, while the sound was not affected.

The improved bridge rectifier/filter cap section helped a lot with dynamics IMHO, as I noticed that, before modding the thing, while playing power chords at higher volumes the amp seemed to "squash" the sound somewhat....now the power chords are more "open" and the notes' attack seems no longer "squashed". The added power changed the amp from a home/studio thing into a rehearsal/small gigs/club amp, not bad for an amp of this physical size (and weight).

If you go for a 2040, you can leave the original speaker in place, but, should you opt for a 2050, I strongly suggest to move to a better (and bigger) speaker (you'll need to put the soldering iron aside for a while and use a saw, a rasp plus some sandpaper instead).

Hope this helps

Best regards

Bob

[role_65]

Looks like i might stick with modding the bridge and the Caps, what flavor of caps did you use? sorry to be a pest just starting my modding frenzy recently, I will be using this in a studio. depending on noise i might swap OP amps. Honestly i don't really love the sound a little harsh sounding to me so maybe some different value caps can change the tonality of the thing, but my first mod is to enclose the back. I thought about just getting an alinco speaker and closing it up to see what that does. sorry for all the questions and THANKS!
Ryan

[Robert M. Martinelli]

Hi again Ryan,
since you're going to use the amp for studio work, I'd change all the op-amps and move to 5532s; only, be sure to buy them from a reputable parts seller because there are a lot of fakes around. Adding DIP sockets is always a good idea as it allows an easier replacement.
I also glued a brass plate on the inner part of the electronics' back cover, this makes for an almost perfect Faraday cage, reducing the change for the amp to pick up unwanted noise.

As to the PS filter caps, I used standard electrolytic capacitors.

If you're going to tinker with caps along the signal path, poly capacitors will do just fine. Be aware though, that, in order to obtain a mellower sound, it could be enough to alter the feedback capacitor(s) in the preamp section (C7 for IC1B and C19 for IC2A). Those caps should be ceramic ones if memory serves me well, and by increasing their value(s) you will reduce the amp's highs content. Try a 330 or 390 pF (C7) for starters.

As to the speaker, remember that, with a properly sized PT and PS section (I threw in a 4 amps rectifier bridge ad 2x4700 uF filter caps), your TDA2050 will put out 28 W RMS, and the amp's ability to respond to loud transients will be improved, so it's advisable to use an over-sized (40-50 W) speaker.

Hope this helps

Best regards

Bob

[mod_squad]

Robert quick question and I should add I'm a complete noob to ss amp design,

I haven't looked inside, but the TDA2030 is rated at 8W at 8 Ohms which appears to be the stock speaker rating. Is the amp using 2 chips bridged to achieve the advertised 15 watts? It would seem a TDA2040 would be necessary to achieve around 15 watts at 8 ohms? Or maybe the 15 watt advertised rating is simply optimistic?

[Robert M. Martinelli]

Hi and welcome to the forum!

Maybe the rating is optimistic, anyway, the 2030 inside the Pathfinder 15 is supplied at its maximum permissible voltage, and the 8 W figure is the "worst case" one. I'd say the "stock" power is something in between 11 and 14 W, it doesn't make much of a difference though, because to "hear a difference" you need a +3dB increase ( the minimum audible difference the human ear can perceive ), which can be achieved only by doubling the output power.
FWIW I find the stock Pathfinder is pretty loud for home use, it needs a power increase only if you plan to use it on rehearsals or small gigs.

(JM2CW)

Cheers

Bob

[mod_squad]

Hi and welcome to the forum!

Maybe the rating is optimistic, anyway, the 2030 inside the Pathfinder 15 is supplied at its maximum permissible voltage, and the 8 W figure is the "worst case" one. I'd say the "stock" power is something in between 11 and 14 W, it doesn't make much of a difference though, because to "hear a difference" you need a +3dB increase ( the minimum audible difference the human ear can perceive ), which can be achieved only by doubling the output power.
FWIW I find the stock Pathfinder is pretty loud for home use, it needs a power increase only if you plan to use it on rehearsals or small gigs.

(JM2CW)

Cheers

Bob

Thanks for the response! Agreed the amp is more than sufficient for home usage. My goal with the amp is really to experiment and hopefully learn something beefing this puppy into a giggable amp and potentially converting it into a head unit. Based on your above statement, to get a significantly more juice it seems an upgrade to the 2050 (~32W, double the 2030) is the best route as the 2040 (~20W) would be a fairly subtle increase in output. In the second post you stated an upgrade to a 2040 but you also state swapping in a 2050. Did you try both?

[Robert M. Martinelli]

Yup,
I first subbed in a 2040, then moved to a 2050 ( modifying the PS section because of the 2050's greater current demand ).

As already stated, if moving to a 2050 a speaker upgrade would also be advisable.

Good luck with the mods, I really hope you'll have fun in the process and I also hope the results will be satisfactory.

Cheers

Bob

[lowfiataca]

please help

hallo guys. Im new in here and i have a little question for you. you all seem experts in the subject of Vox Pathfinder . I have my pathfinder 15 R since 3 years with no problem, until today. I just wired the pathfinder to a 2x12 cab thru the external cab out in the rear panel of the amp. the thing is that te amp sounded but something inside started to smell like freid circuits and then the amp just died.... well, not compleatly, the led in the amp says that the amp is still alive, but no sound comes from the speaker, nor signal fron the headphones plug or anything else. i think it can be that the problem could be the the power amp chip, the tda2030. what do you think guys? please some one help meee!

(im so sorry for my english)

[Robert M. Martinelli]

Hi and Welcome!

According to the symptoms you described, yes, it's possible that you fried the 2030.
My guess is that the cab's impedance was too low (4 Ohms? Did you check it before connecting the cab to the "ext speaker socket"?) and the 2030 has been forced to operate well above its ratings (The internal speaker is an 8 Ohms one). If you've been lucky you'll find only the 2030 has gone south....

Cheers

Bob

P.S. - To help keeping the forum well organized, and to make the "search" function more effective, I suggest you to start a new thread instead of "hijacking" an existing one - this will make life easier for all the people needing help on similar problems.

[JakaJ]

tda2040 or tda2040a or tda 2040v

Dear all,

I realize this is an old thread, but I hope someone can clear things up for me.

I am not a tech and have thus far only ever modded guitars and replaced speakers in amps - well I built an extension cab - that's the limit of my experience. I am curious to make the next step- and apart from trying the led mod on the Pathfinder 15r I am also curious to try to replace the tda2030a with a tda2040,

In following the above posts it seems to me that I can just drop in replace one for the other?

Also is there a difference between tda2040 and say tda2040a - and tda2040v? If so what should I (but a musician) keep in mind?

I may be changing the stock speaker later as well - but as far as I can guess the stock speaker will not blow unless I drive it full throttle (I like the headroom and better dynamics of a higher wattage amp) - Or will the stock speaker blow?

I thank any and all who are willing to help me out.

Best regards,

Jaka

[Blueshobbit]

Hello everyone, I've been enjoying all of the Pathfinder mods listed here for awhile. Thank You to every one that has listed their input. One mod I'd like to do is to drop the amount of boost when the "boost" botton is ingaged. Either by changing the voice or amount of gain. As is I find the switch unuseable as a lead/ boost option. Anyone have any ideas?

[Blueshobbit]

I was looking at a pathfinder schematic & wonder if changing the value of resister R10 from 4.7K to a larger value would help tame the Boost any or maybe changing the input resister R13 from 150K to +/- 300K. Any one have an opinion?

[littlericky]

With help from the folks at the ssguitar forum I was able to put a boost volume pot in