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Messages - Dimi Pana
« on: April 20, 2012, 12:52:54 PM »
It sounds like there is something defective with your amp or speaker or maybe both. Again I am no expert, take my advice with "a grain of salt" and only if the other members here in the forum agree with what I say.
If I were you I would try to find a known functional speaker of 4Ω (8Ω will also work) rated at least 8W or more and start with the gain at zero and the volume at very low. See if a different speaker has any improvement. If yes, then the original one is shot (That's my educated guess!). If not then the circuit it self has been tampered with, or compromised or even broken by the previous owner's use (most likely abuse). I would also try to run it with a power supply just to compare, or put in fresh batteries. In both cases, (i.e. attaching an external speaker and power make sure you observe the cable polarities.
My experience with my amp is that it can be (as is, with no mods) a very basic but decent practice amp, period. I use both the clean and the "dirty" sound with acceptable results, but again remember I have somewhat lowered my expectations.
I have an Epiphone ES-175, this guitar (unamplified) is so loud, almost as an acoustic. I use the amp -satisfactorily- to a level where the amp sound level is masking (covering) the guitar's acoustical level. I play in my finished basement with carpeting and furniture, not much sound reflection to create feedback, I play about 10 feet away from the amp. I use the Volume to dial a clean (no Gain) sound and play with the amps Tone to achieve jazzy (rolled-off) or rock (all the way up) sounds. I then turn up the Gain to introduce distortion up to a -somewhat- musical level. In my case anything more than 50% up Gain is unusable. Once I am satisfied with the amp's settings I then use the guitar's controls to "tweak" my sound a little more. One can only do so much with this amp though, keep that in mind. I also play MP3s via my TV's speakers and use that to jam along. I am pretty happy with the results, my girlfriend often complains I am getting too loud (go figure?!).
Basically, I paid $3.95 (+ tax) at ToysRUs and I bought nothing more than a toy amp that still allows me to practice alone or even with two of my buddies (bass + drums) at acceptable and -thankfully- non deafening levels. At that price, it's a no brainer... We pretend we are a trio power group and knock ourselves out, covering well known tunes. Again, the key word here is pretending. (lol)
If your experience is nothing like that then there is something wrong with what you got. Ideally, you should have asked to try it before you bought it , but I understand this was a garage sale. Can you take it back? I do not know how I can help you more. Oh, and just to clarify, I asked you if you are in the US, because electricity is different from country to country and a power supply made for one place might not work right in another, but then I realized you are using this amp with batteries not a p/s. Sorry...
« on: April 20, 2012, 09:28:41 AM »
I am not an electronics expert but I own this amp (similar to yours) for about 6 months now. I agree with your statements, but in my case, I have been able to use its "clean sound" at low volumes without problems but I have lowered my expectations as well. What is exactly that you experience? If all you get is (unmusical) distortion at pretty much any settings combination then I am inclined to believe that your unit might have been defective or simply broke while used by the previous user hence sold at a garage sale? If I am not being nosy , how much did you pay for it? It really is not worth spending too much fixing it, other than (if you have the time and $$) to try a different speaker and perhaps swap some of the components (already suggested in the beginning of this thread) with different values, until you get (somewhat) what you want. But in my opinion it is not worth it, time or money. You can always try using a power supply instead of batteries, and thanks for the specs, it confirmed what has been discussed here all along, BTW, are you in the US, where? Cheers!
« on: April 19, 2012, 11:31:30 PM »
Certainly the MA1248 that I have and the one you bought (MA2039) are similar (I would say identical in design and purpose) but their PCB layout -clearly- look different. I was involved with this mod back in late fall 2011, but I was not able to get it to sound any much better so I got discouraged. I did lift the diodes but lost most of the gain control functionality. I then had a health issue and dropped everything else, so over the past few months I have not spent too much time with this. Once I am fully recovered I will probably try the mods in the order they were suggested from the beginning of this thread and see how it sounds. If I get it to behave better, so be it, if not I won't waste my time. Currently I play with the Volume at 25%, the gain at 20% or less and the tone at full 100%. I then adjust using volume/tone pots and pickup selection on my guitar (Epiphone ES-175). I have managed to tame it without that much messing with it. I have also changed the wal-wart to one with higher volts and amps (24 V, 1.5 A) I think it helped the original humming but only by a little bit. Overall, this is a cheap toy amp, it's OK for non demanding practices/jams but will disappoint you in every other situation beyond that. Again this is not an amp this is a cheap toy, at one point back in December ToysRUs was selling these for $3.95 ea, probably just to empty the selves at the warehouse. Good luck!
PS: One quick question I have for you: Do you know, can you read the specs on the speaker? Did your amp come with any manual etc. Mine did not and the speaker has no info on it at all. I have to assume these amps are using 4Ω speakers rated at 8Watts but I cannot 100% be sure. Any thoughts? Thanks!
« on: November 13, 2011, 04:19:36 PM »
OK, if you have not had enough of me today, just one last question, which I should have asked from day one:
What would be a FREE, easy to use, i.e. no steep learning curve, PC program to draw schematics with?
I mean, I've tried MS paint but -obviously- this program is not made for that.
« on: November 13, 2011, 03:25:46 PM »
Has anybody been able to open the MA104Final.png attachement Koreth has posted in the very beginning of this topic?
I am trying to compare his schematic with the one I have traced from my MA1248 amp and I cannot open the file, every program I tried say things like "invalid format", "corrupt file", etc.
Can anyone repost this file please?
Also, Koreth, is this your
final, I mean FINAL, version?
I've compared my MA1248 with the MA107 (schematic posted earlier by DartPlayer170) and even a novice like myself can see there are differences, e.g. some R,C values are different but over all they are very similar.
I also know for a fact that the MA104 and the MA1248 are identical, at least two units I compared recently side by side. Koreth has mentioned that his is using the TDA2003 while mine is using a TDA2030 (and yes, as stated before this is not a typo) plus from another schematic (posted here: http://music-electronics-forum.com/attachments/7178d1260175055-ma104.png
) it appears it's using two JRC4558 instead of one. So I am inclined to believe that the MA104 Koreth bought back in 2009 is slightly different than a MA104 currently sold by first act.
I reviewed both data sheets:
and other than 4Watt ouput power difference, both seem similar to me.
So what I am trying to do is compare side by side three schematics:
1) Koreth's (year 2009) MA104
2) DartPlayer170's MA107
3) Mine MA1248
Once I have the closest match I can produce a final version of the MA1248 schematic, which will help with all future discussion.
Anyway, is is possible -anyone- to repost the MA104Final.png schematic, please?
Thank you all!
« on: November 10, 2011, 03:32:59 PM »
I do not mean to distract you from this very interesting conversation, I just have a quick question for all but especially for Enzo and what he said here:
Most FX loops are simple breaks in the signal path through the jacks. Some fancier ones have a little drive circuit for the send.
I have a very cheapo practice amp I am experimenting with and being a novice, destroying basically a toy is not the end of the world.
It appears that this amp is build around a JRC4558 for the preamp and a TDA2030 for the power amp (please show mercy I use the terms loosely.
. There is also a FET at the amp input acting -I think- as a buffer.
The toy-amp has one Volume, one Gain, and one Tone control.
Assuming that I can identify the point
where the signal is handed-off from the preamp to the power amp and given the cheap-o-ness (read: simplicity) of the design, is it safe to assume that simply by cutting into the pcb trace at that point[/u] and inserting two 1/4" audio jacks as SEND/RETURN will provide me with a crude yet functional FX Loop ?
From Enzo's post, I understand that some (more sophisticated) FX loops use a drive stage at the output (i.e. return) to compensate for any signal loss. In my case, this is not applicable, I can't build a drive stage plus I think I do not need one.
I plan to use an FX unit that has separate stereo in/out level controls, plus a mix pot DRY/WET and -if the unit documentation is not lying- a true bypass foot-switch.
So, what my diy FX loop will be lacking, the FX unit will provide thus compensating for the crude hack.
I tried to put the FX unit first, e.g. after the guitar and before the toy-amp but it sounds, well, just bad...
Again, sorry for the intrusion, aoresteen
is doing exactly what I want to do (of course mine is extremely simplistic) so I was hoping to ask if this would work.
« on: November 08, 2011, 12:46:24 AM »
Very interesting thread, I wish more will contribute. Funny thing is I was recently looking at this --> http://www.tubesandmore.com
website while researching on cabinet speakers.
I have a parallel question to what you're discussing here.
Say you have to chose between a single speaker or a combination of 2 (or more) speakers to achieve the desired Ω resistance for your amp. If -for example- a 2X8" combination has -almost- the same (cone) area as a 1x12", or to make the question more ..."provocative", if a 4x4" has exactly the same area as a 1x8", why the 1x12" would be the choice of most people. Is it the better bass response of the larger 12" speaker or what?
I am not sure how I come up with these questions, probably because for the last few days I've been sick as a dog and have too much free time just lying in bed fighting this nasty cold.
« on: November 03, 2011, 10:15:50 PM »
I can't say I have a lot of experience playing different amps, I started with classical and switched to acoustic pretty quick after that. Now I am slowly treading into electric territory which requires (duh!) an amp. I spend enough time at -usually- Guitar Centers playing different amps with -usually- hollow body/archtops. I have to say that my ears are telling me there is a difference but can't tell for sure if I like tubes more than SS. However, solid state amps win hands-down when it comes down to price, maintenance and of course the amount of abuse an amp will take before it refuses to cooperate anymore. So, I'd say I am an SS guy because: I am not rich, I am not a professional musician and sound-wise I am easily satisfied, I can buy an OK sounding mini amp for under $50 kick it around pretending I am Pete Townsend without being afraid that I'll break the tubes. Yes, SS works for me, for now.
« on: November 01, 2011, 02:04:30 PM »
ΟΚ, this is probably a waste of time for you all, it was a good exercise for me.
Here's what's going on:
There are two build versions posted by BeavisAudio. One is a PCB based one the other is the RadioShack (RS) version. BTW, I am building the RS version since at this point I do not have what it takes (knowledge and tools wise) so I cannot print and etch my own PCB.
Each version includes (at least) the following:
1. Parts List
3. Parts Layout
Here's what the error is (regarding the V, G and T pots):In the PCB version:
The "Parts List" agrees with the "Schematic" and both disagree with the "Parts Layout" In the RS version:
The "Schematic" agrees with the "Parts Layout" and both disagree with the "Parts List".
Of course, all this is immediately recognizable by all you experienced people, unfortunately in my case it is a "show stopper" since I realize the discrepancy but I am unable to distinguish between RIGHT and WRONG.
However, by reading your posts and doing some research myself, here's what I will do:
VR1 = Volume = 10KΩ
VR2 = Gain = 1KΩ (*)
VR3 = Tone 100Ω
Νow, because, RS do not carry a 1KΩ pot, and since phatt(*)
already suggested to change it with a 10KΩ, is it OK to use -instead- a 5KΩ ( just happen to have one) so I do not have to buy it? I do not want an explanation why (to save you time) just a YES or a NO.
Last question for today: This design calls for a 100nF "poly film" capacitor at C3. JMF suggested I change it to a 10μF (right?). I cannot find this value in film but I can in electrolytic. Can I substitute film with electro? Again, I am asking for a YES or NO answer, obviously I'm interested in the WHY, please answer only if you have a short and simple one, anything longer just post a link on the net, let me then do the reading.
How am I ever going to pay you all back for your patience, kindness and your hard-acquired knowledge offered for free? My family owns a small "Bed & Breakfast" motel in the Greek island of Santorini, so if you ever visit my country, please drop me a line, I might (actually for sure) be able to work something out for you. But please hurry, given the current financial instability and judging by the (poor) quality of the Greek politicians, I am not sure if in the near future Greece will still belong to the Greek people or owned by some big, inconspicuous financial conglomerate.
« on: October 31, 2011, 07:10:06 PM »
Hey, how about this:
Looking in the NC schematic (RadioShack build or PCB build):
VR2 is the Gain pot, rated for 1KΩ
VR3 is the Tone pot, rated for 100KΩ
Looking at the parts list (in both builds) it appears that these values have been inadvertently reversed:
Gain is still VR2 but rated at 100KΩ
Tone is still VR3 but rated at 1KΩ.
So which is correct? The Schematic or the Parts List?
(Pls, see attached!)
« on: October 30, 2011, 02:47:27 PM »
Ι was building the NC today and I think I got a little impatient (i.e. careless) towards the end, I believe I "fried" the MPF102 with too much soldering heat. I wish I'd bought a socket for it, just like I did for the LM386 IC. I mean there is a socket for this part, right?
I bought my parts from RS (radio shack) and that particular store did not have a socket for the transistor. I mean the attendant in the store I went (Rt. 83 in Des Plaines) probably knew less about electronics than -even- me... I don't know, from the first time I stepped into a RS, it did not feel right somehow.
So, anyone from the Chicagoland area? Do you know a decent and novice-friendly (yes, that's me!) retail electronic parts store?
« on: October 29, 2011, 04:51:47 PM »
We are in DIY SSGuitar here, want to keep things within our average Memberīs reach.
Funny, probably while you were typing your last message, I found this:http://recording.org/diy-pro-audio-forum/43122-tips-making-guitar-output-splitter-please-2.html
<-- (look at the last post of that thread)
I was about to ask you if that's what you meant BUT you beat me to it!
I learned a lot today, I am getting off of my computer NOW, or I 'll be abusing your kindness.
« on: October 29, 2011, 04:38:10 PM »
C3=10μF and no pin7-5 circuit at all.
Shall we say this is FINAL?
(at least for today?)
« on: October 29, 2011, 04:16:58 PM »
EDIT: 1st Schematic removed as not correct and all relevant discussion, from this post.
I am posting three designs I found in case anyone would care to comment on their pros and cons. I would n't mind the passive design and the loss of treble, I'm not a pro musician, so I do not really care. Nevertheles, these 3 are definitely beyond my building capabilities.
« on: October 29, 2011, 02:58:37 PM »
Δημήτριος would be Dimitrios
Παναγιωτίδης would be Panationis
του this one beats me
Γεωργίου would be Georgiou
You got 3 our of 4, that's impressive!
The "του" word is a declension of the singular form of the masculine article, in the genitive case (i.e. possesive). It basically means "of the". Thus my name is: 1st name Dimitrios (meaning, I was named after the Christian orthodox Saint Dimitrios), 2nd name Panagiotidis (that's my family name which -simplified- means the decendants of Panagioti who was my great-great grand father) and 3rd name (of the) Georgios (meaning that my father's 1st name is Georgios). According to Greek culture we name our children after their grand father/mother's names, which -you guessed- creates ever more complicated combinations.
I agree about the external quality or the greek women, and I am with you 100% on their pointless and futile desire to look less "Hellenic" and more American. But what can you do? Nothing... Can't live with can't live without them. Luckily, for the time being I am taking a hiatus from Greek women. Living in the US -definitely- gives one the advantage to be ethnically more ...selective.
BTW, any comments on the modified schematic? Let's not forget what we're here for eh!
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