Hello all,

I have an Ashdown MAG 300 head that has a very boring tone. I would like to re-tune the EQ to match the frequencies that an Ampeg SVT has. The amp will not suddenly sound like an SVT I know, but I always feel the controls are better placed in an SVT in terms of the tonal spectrum.

I've found a schem for my amp here at the bottom of this page;

http://music-electronics-forum.com/t28046/#post307779

On the Ashdown, there are five EQ controls. They are, and their frequencies are;

Bass - 100 Hz
Mid - 650 Hz
Treble - 7 kHz

Lo Mid - 340 Hz
Hi Mid - 1.6 kHz

This doesn't seem like an ideal spread to my ears. I always feel that Ampeg gear has a sweeter mids response.

Ampeg frequencies are;

Bass - 40 Hz
Midrange (switchable at) 220 Hz, 450 Hz, 800 Hz, 1.6 Hz and 3 kHz

Treble is at 4 kHz

Ideally I would have the Ashdown 'retuned' so that the bass control was at 40 Hz, the mid control at 800 Hz 'lo mids' at 300 Hz, the 'hi mids' at 1.2 kHz or so and the treble at 4 kHz.

Is this possible just from substituting the caps and resistors affiliated with each control on the schematic?

Thanks in advance,
Kobaia

Quote from: phatt on August 03, 2013, 07:10:11 AM
Good to hear you got it working the way you wanted. :tu:

Just be aware that tweaking is very addictive
Phil.

I've been addicted to tweaking for a while...


...that came out wrong...

Well now...

I chanced C14 to 0.047uF, C12 to 2200pF and C13 to 0.1uF (or 0.094uF as I had to put two 473 caps in parallel). This works!

The shrillness is gone. In a weird way I slightly miss it. As somebody pointed out, the stock amp is good for 'country clean', and this is probably why they love it on TDPRI. With these mods, I can turn up the treble without it getting shrill, and I can turn up the bass without it flubbing out. It sounds more Marshally, though I'm not going to kid anybody with that really. The good thing is I can swap between humbuckers and singlecoils now without getting harsh single coils or muddy doubles. Great!

Thanks everybody for the help. I urge at least one other Pathfinder owner to do these mods!  :dbtu:

Quote from: J M Fahey on July 31, 2013, 04:07:34 PM

QuoteAny ideas how to shift the bass control up a little as well? It is boosting bass in an area I don't need the bass boosted. I ran this amp into an 8 ohm Ashdown bass cab I have here, and ran my bass into it, and it works quite well as a bass amp. Too much bass!

What you write sounds like a contradiction.

As it stands I can use my Pathfinder 15R as a usuable bass amp if I run it into a bass cabinet.

As it is meant to be a guitar amp it seems to have too much bass on tap. I haven't had any luck modelling the tone stack in the SD tonestack calculator yet, but it seems that the bass control on the Pathfinder currently boosts bass around too low a frequency for 1) guitars in general and 2) a wee practice amp with an 8' speaker.

In my head, I think the amp would be better if the bass control boosted higher frequencies, roughly what bassists would call 'low mids' (though guitarists still call them bass frequencies). I guess around 300 Hz or so. I don't want to lose the fundamental note of the lowest string of my guitar, but I don't want the farty flubby mess that the Pathfinder currently produces. In my mind they should have brought the treble and bass controls closer in terms of frequency cut and boost, and used a bit more aggressive LPF and HPF to keep things within the confines of what such a speaker (and cab) can realistically reproduce without sounding bad.

Thanks for the advice guys! That Youtube video highlights some of my grief, just in micro detail. If nothing else, that is not how you play The Wind Cries Mary. Life in the Fast Lane is a bit rough as well.  :trouble I think the Les Paul tones especially reveal the 'skuzz' I'm trying to remove.

I'm surprised that VR2 and VR3 are the treble and bass controls because I was counting knobs left to right, and figured they would be VR 3 and VR4. Thanks for setting that straight!

Any ideas how to shift the bass control up a little as well? It is boosting bass in an area I don't need the bass boosted. I ran this amp into an 8 ohm Ashdown bass cab I have here, and ran my bass into it, and it works quite well as a bass amp. Too much bass!

Fair shout!

The link is here;

http://www.fenderforum.com/userphotos/index.html?recid=69518

Its a big image, probably exceeds bandwidth rules on here at a guess.

I've modded my Pathfinder to have a louder reverb as well. Anybody interested in these mods?

Hello all,

I live in Edinburgh, Scotland and I'm 24. I've played guitar since I was ~13 or so. I've always had SS amps of various types. At the moment I have a vintage HH VS Musician 212 combo at my parents' house which I've done some work on.

When looking for a smaller amp, I chanced upon a Vox Pathfinder 15R in a pawnbrokers. Having liberated it, I've enjoyed the tones from it ever since. I've done the common LED mod, though I'm not 100% sold on it.

What I would really like to do is mod the tonestack. I would like to make the amp overall less bassy, and more tight sounding. I would also like to maybe reduce the brittle high treble content a smidge. I understand this can be done through the tonestack. I found a thread on here regarding the Pathfinder 10, but it seems that the circuits don't directly translate.

Using the commonly found schematic, I presume that VR3 and VR4 control bass and treble. However these are not near each other, topologically, which makes me wonder how this circuit works. Can anybody shed any light on this area?

It looks like C12, C13, C14 comprise something that looks, to my untrained eyes, like the Vox diagram in the Duncan tonestack calculator. However the bass control is located near C20, if I'm reading the circuit correctly.

Any help would be appreciated. I realise I cannot expect anything too great here, but I feel the tonestack is slightly less than optimal in the 15R, especially given that it is a 2-band EQ. I feel that the bass has become 'flubby' since I removed the LEDs.