Fender Squier 15

[SpareRibs]

Hello,
       This is my first post. I live way up in Oregon so and there not much in the way of repair shops or the like in this area. I am interested in learning how to do simple repairs and improvements on my own amps and equipment.                                                                                                             I own a small squier 15 amp and would like to know if this amp worthless or are there ways to improve the sound? I have some 12" 8 OHM speakers, but I am wondering if it even has enough power to drive one of them. I would also like to know if I may be able to change any of the resistors or capacitors to open
it up so it sounds larger?
        I would appreciate any help anyone could provide. Thank You in advance!!!! 

[Enzo]

Just changing the speaker will do more to alter the sound than anything else you do to an amp.


The ONLY thing an amp circuit knows is the impedance of the speakers you connect to it.   It has no idea how many speakers there are, or their size or their ratings.   so you can take the tiniest practice amp and connect it to a 4x12 cab.  The difference in sound will be amazing.   You just have to make sure you do not wind up with too low an impedance of speakers.

Try that before you start worrying about resistors and capacitors.

[SpareRibs]

Hello,
      Thanks I will try that. I was going to build a cabinet because I have a few 12"speakers I rescued
from organs.
       I also have a 8" speaker I took from a surround sound unit, the bass part . Would that function as as amplifier speaker. The paper cone seems quiet thick. 

[J M Fahey]

The 8" audio subwoofer will be very unefficient and muffled, go for the organ 12" ones instead.

[Enzo]

Or just arrange to borrow a friend's guitar speaker cab just to listen to.

[Roly]

15 watts is actually quite a bit of power.  Many guitarists these days are turning to 15-18 watt amps for a whole bunch of reasons, not least is that with the right speakers they are more than sufficient for most small gigging (and in large gigs you mike them with the PA to give them some "legs").

What you are about to discover is that all drivers (speakers) and cabinets are not created equal.

Forget entirely about speakers that are for subwoofers, cars, or Hi-Fi.  Musical instrument speakers are a different animal.

Ex-organ speakers are a reasonable prospect for guitar.  They won't have a lot of power handling capability (but 15 or more watts is a very good bet), fairly wide bandwidth, and reasonable sensitivity (efficiency of conversion of electricity into sound).

The main drawback with amps such as this one is that the box is simply too bloody small to do the job properly, the speaker is choked so the cab can be small and more portable - which kinda defeats the reason for lugging it to the gig in the first place.

12 inch Speaker Cabinet build out with Lil Night Train
http://www.youtube.com/watch?v=y9DQhCAB0yE

(...and you've already got some speakers to try  :dbtu: )

[SpareRibs]

Hello,
      I would like to thank everyone who responded to this post. I took all of your advice and used one of the organ speakers. I already had one mounted in a cabinet, so I removed all of the inner workings from the small Squier amp and installed it into the larger cabinet. I cannot believe the difference.
      I still have a minor problem with scratchy pots but I am sure some electrical cleaner will help. I am
going to make the same change to a small RMS 200 practice amp I have.
      Thank You one and all for the help pointing me in the right direction, and preventing me from doing
more harm than good.
                                                             :dbtu:

[J M Fahey]

I cannot believe the difference.

That's the point
Glad you went straight to it. 

[Roly]

I cannot believe the difference.

Yup.  (heh heh heh).   :dbtu:

[SpareRibs]

Hello,
      OK, I moved all of the inner workings into a larger cabinet. I cleaned all the pots and it is at the very
least a 100% improvement. It is really louder and a much more open sound as a result of I guess less of
the sound being confined to the small speaker cabinet and, the larger speaker.
       Now I would like to know if there is a way to (for the want of a better term) thicken up the sound?
Are there any caps or resistors that could be changed to give it more of a tube sound. I think it would be
called sag. I know I cannot make a silk purse out of a sows ear, but it is all I have to work with at this time.
      As always any help would be greatly appreciated!!!

[Roly]

a 100% improvement

You do realise that is only twice as good, don't you?   :lmao:

As you are discovering, some rather nasty things happen when you shoehorn a speaker into a cab that is too small, but you only have to walk into any music shop to see the dominance of physics-free marketing types in commercial amp manufacturing - tiny little boxes that have no chance at all.  Back in the days when valve Hi-Fi's were the only option there was a saying about speaker enclosures that "there ain't no substitute for cubic feet", and despite everything since it's still true.

I used to work for a company that made tiny hand-held radios (that honestly sounded pretty damn shocking) and my "party trick" was to hook one of these up to whatever big guitar speaker box happened to be available, and astonish everybody with the transformation.  Bass!  And how loud only 200mW could be into a proper speaker.  The radio circuit was fine, just crippled by a 2-inch speaker in a tiny plastic box.

Are there any caps or resistors that could be changed to give it more of a tube sound.

The Holy Grail!  You want it all, now, right?  Well don't we all.

I'll let you into a little secret - exactly why valve amps sound like they do for guitar is a topic of endless ongoing debate, even among highly experienced experts.  A key element is the output transformer and its magnetics, and since solid-state amps don't have one that presents a bit of a stumbling block.

Something simple you could try playing around with are the two diodes D1 and D2.  These are the same type with the same forward voltage cut-in, and thus give symmetrical clipping of the signal.  If you change one of these, say by putting a second diode (e.g. 1N914 o.n.o.) in series with one of them you will get asymmetrical clipping which will produce more second harmonic distortion, and this might give you the "thickening" you seek.  YMMV.

Otherwise you are just going to have to build yourself a valve amp.   

[SpareRibs]

Hello,
      Yes I am aware of the ongoing debate about tubes vs solid state. Any one can start a 10 or 12 page argument just mentioning either one on any forum. I also am aware there will be no holy grail fix to make  either sound like the other. Maybe that is not the proper way to describe what I wanted to achieve now.
      I think what you just suggested is exactly what I was trying to ask for, and that will just make the sound slightly darker if that makes any sense. Sound is hard to talk about as I am sure you know. One of least descriptive and the and most talked about things are speakers and guitar pickups. All of the way the sounds are described tell you very little. To me crunch, bottom end, scooped mid range, soaring highs, is a bit much. I usually know less after I am done reading the description.
      I am going to look at the schematic and make preparations to do the mod you suggested. Thank You very much, and please know I am not a bleary eyed kid trying to turn this little practice amp into a
Marshall Double stack.

[Roly]

I usually know less after I am done reading the description.

I know exactly how you feel - "well that subtracted from the sum of human knowledge" or "there's ten minutes of my life I won't get back" or "WTF am I reading???", etc.

Valves vs. transistors is a whole other thing, calmed down a whole lot these days thank goodness; I just meant that concerning valve amps alone there is no unanimity on why they sound like they do.

One little point about the diodes; putting a couple of silicon diodes in series will be a pretty drastic change, and if you can find a germanium diode to add in series with one of the existing silicon diodes you may get better results, or failing that a Schottky diode.  It's a bit of a shot in the dark, but it should be a pretty simple thing to try.

Let's know how it goes.

[SpareRibs]

Hello,
I have a few of the Schottky diodes from disassembling various things in the past. Could you recommend a value? That would get the project back on track, as everything will be closed until Monday at the earliest. Thank you in advance.

[Roly]

You have?  Great!

Different types of diodes, silicon, germanium, and Schottky, have different forward voltage drops, silicon 0.5-0.7V, while germanium and Schottky are closer to 0.1V.  Otherwise it's whatever will physically fit, exact type number immaterial.

Your DMM will show you the forward drop in millivolts on the diode test range.

Go for it!   :dbtu: