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Practice Amp Suggestions?

Started by Bakeacake08, August 01, 2014, 02:52:47 AM

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Bakeacake08

I'm wondering if anyone has any recommendations for a good practice amp.


. . . electrical modification practice, that is.  8|


I've been looking at various second hand websites, and I've discovering that one can buy any number of entry lever guitar amps dirt cheap (<$20 US). I was thinking it would be fun/educational to pry one of these open and try to make some changes to it. Is there any particular amp(s) that stand out as being commonly modified to improve the sound a little? Not necessarily improve the sound, but make it somewhat at least noticeably different (e.g., doing something to reduce the hum). I figured I could work on my circuit skills, and worst case scenario I bought a bin of parts useful for twenty bucks.

Your thoughts?

J M Fahey

Good idea   :dbtu:

Since most go for that price, and knowing what you want them for, I'd choose a "known brand" one, say Peavey/Fender/Crate/etc. instead of mystery ones , simply because schematics are easier to find and they will use standard parts, say TDA2030 , TL072 , etc. for which datasheets are easy to find.

While data on First Act, Esteban, etc. are impossible to find.

Enzo

I agree with Juan, look at one you can find a schematic for.

However, for the most part, inside those small amps, things are pretty much the same.  Most of them use a TDA2030-2040-2050 type power amp. Most have one or maybe two op amp ICs.  So the brand and model don;t matter a lot.

J M Fahey

There is one specific model which I have already seen under a hundred brands (not kidding), it´s always the same with: jack input - distortion pushbutton - treble - bass - headphone out and the telltale " 6"/6.5" speaker "  and they are usually labelled 10W.
It´s the typical amp which comes bundled with the cheapest guitar.
Hey!! I even saw one of these paired with a "Metallica guitar" and Kirk Hammett himself pushing it !!

Never had the schematic but I´m certain they have 1 dual Op Amp, a TDA2030 , basically the same as the next higher 15W version, and they spec them as 10W simply not to cut on sales on the 15 watters, which typically have heavier 8" speakers (and a few even 10").
I imagine a huge factory churning just these for anybody who wants them.

Bakeacake08

Well if Metallica uses it, it must be good, right?  :cheesy:


Yeah, I've seen a lot of those types around recently. Pretty much exactly what I was looking for. Though I did see someone selling a beat up Marshall 15DFX for $20, which I used to own and really liked (I sold it to help pay for my wedding), so that one has had my eye for a couple of days now. It's a really nice day today though, so I might go out and see what all the yard sale people have to offer.

BrianS

I posted an ad on Craig's list looking for broken solid state amps just for this purpose.  I specified that I would pay no more than $25.

I got two replies right away...one was an old Heathkit TA-16 and the other was an 80's era Yamaha B-115 bass amp.  I paid $20 for each, no cabinets or speakers, just the chassis and electronics.  Both have been good "practice" amps and the Yamaha will be re-appropriated into a guitar power amp soon. 

Point being, try CL if you can...you may find some gems for cheap.

J M Fahey

#6
Cool !!!
You got more than you bargained for, much better than typical beginner´s amps.

The TA16 is a classic oldschool discrete amp and one was repaired here (or in MEF) short ago, search for the thread.

The Yamaha is a killer "real"  amp and chassis/heatsink/transformer are worth way more than $20 ... even better bargain if you actually repair it original.

As of the Marshall, it´s a very good sounding amp , so if you have spare $20 ... go for it.

And then stop, or your home will look like mine: impossible to walk through because of towering mountains of junk which *may*  be repaired ;)

.......... someday :(

g1

JM:  that thread about the TA-16 was by BrianS, (not the OP of this thread) so he already fixed the amp in that thread  :).
http://www.ssguitar.com/index.php?topic=3511.0

Roly

The price of a second hand amp (or just about anything actually) is simply demolished by a fault, yet in most cases the faults are minor and easily fixed.  The vast majority of "trove" amps I've been given/roadside hard rubbish/dumpster diving/tip scrounge have gone to new homes and not one in ten has turned out to be really worthless junk.

The Yamaha in particular looks like a real find.
Yamaha B-100-115 service manual;
http://elektrotanya.com/yamaha_b100-115.pdf/download.html
If you say theory and practice don't agree you haven't applied enough theory.

BrianS

#9
QuoteI was actually going to start "repurposing" this amp yesterday, but after staring at the chassis...for what seemed like hours...trying to figure out how to re-cut and re-bend it, or just remove everything and try to make a new chassis, I decided that I will just refurbish the amp and build a new cabinet for it. 

So yesterday I purchased a "Tiny Giant" amp kit.  Not nearly as nice or as powerful as the Yamaha would have been, but hopefully it will suit my needs (power amp for a Tech 21 Fly Rig 5).
Why rehouse the 100W Yamaha?
You trying to fit it in a pedalboard or even worse, your guitarcase, like in the Flyrig ad?  :o
Don´t think so.  8)

And the Tiny "Giant" is really ... tiny .... and does not even have its own power supply which when added will also add its own space needs and weight.

And anyway you´ll also need a speaker cabinet (no pedalboard sized ones that I know of) , so I guess the least bulky/heavy yet loud usable anywhere solution would be to build some kind of "combo" or powered cabinet housing, say, a good 12" speaker or 2 x 10" ones and the Yamaha chassis inside.

For minimum size you might even include the chassis in the back (top or bottom your choice) á la Tech 21 Power Engine but in a similar size yet *louder* pack.
How´s that?

Of course, if your hands itch with building the Tiny Giant, go ahead, it will be an excellent intermediate project before tacking the larger one  :dbtu:

BrianS

^Yo!  Why was my post messed with?  Just to be clear:

The above post (#9) was altered by someone (JM Fahey?).  The only part that is attributable to me is the part that is quoted, which if memory serves was the original post. 

As to the questions that have been inserted into MY post, I've answers for them, but I'm a little confused as to how this is all going down right now, so I think I'll wait to respond.

joecool85

My guess is that Juan click "modify" instead of "quote" and didn't realize his mistake.  I will wait and see what he says though before making any other changes.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

J M Fahey

#12
¿¿¿¿¿¿¿¿¿ ?????????:o   :o   :o
Don't understand, FWIW I *answered*  a post in my own words, it's clear from the text itself; don't have the faintest idea why the answer is labelled or signed by Brian S.
Maybe it was "glued" and pasted covering Brian's post?
No clue.
Only thing I think *might* be related to it is that I often have 5 or 6 windows open, jump to a new one to answer (usually search for a schematic or picture, *might* have read a thread suggested as related) and pasted my answer in the wrong window.
*If* anybody has the original text (often sent in the post update notification by email) please post it here so we replace it.
I have no idea of what it said.
Sorry if I messed something  :'(

EDIT: AFAIK I *quoted* Brian S , that's clear to see, and then continued with my own answer.
¿¿¿Maybe I clicked the Modify button instead of the Quote one which lives just by it???
But then why does the "quote" label and corresponding greyed rectangle appear around Brian's text?
Maybe  joecool can check that .
Oh well, delights of fingertip driven netbook touchpads  :(

phatt

Oh No harm done, Lets hope BrianS understands we are all human and even the best of us make mistakes.  8)
I once answered the wrong post with another post answer so the answer made no sense at all and to make it worse I went to bed and only realised my mistake a day or so later.
Oh boy that made me feel very stupid. :-[

I recall a friend who finally got his Dad to embrace the internet and when He recieved his first Email from Dad it was empty. ???
He then realized that Dear Dad had written the whole Email in the *Subject header*  so took quite a while to read it all. :lmao:

I'm not much farther ahead sometimes, doubt I will ever fully grasp the internet and how all these software programs work.  :loco
Phil.

Roly

"Man, woman, child, all up against the wall of technology."

As journalist say "if you have to chose between a conspiracy and a stuff-up go for the stuff-up every time, they are much easier to organise".   :lmao:


To return to the OP; I don't know how much you can plan this sort of thing, ask your friends, keep your eyes open around second-hand/thrift/op-shops, garage sales, fêtes and fairs, hard rubbish collections, dumpster bins (particularly outside houses where people are moving out), recycling centres, the "tip shop" at your local dumps, and such.  Some junk will come to you but mostly you have to ferret it out.  Then tinker with what turns up - it's all grist.

I think most of the experienced techs here would agree that most of the time you can't get a circuit and have to fly by the seat of your pants, and that's an important skill to learn/acquire, but that only comes with practice and exposure to lots of gear.  Also remember that many faults are "off-circuit", pot cleaning, broken socket connections, dirty contacts, etc.

"Your eyes are your best service instrument".
If you say theory and practice don't agree you haven't applied enough theory.