AMPLIFIER beginner questions..

[ToyPick]

Hey guys,

Been fiddling a lot with electronics, mostly sound oriented and have a pretty strong background and comprehension of the sort.

I have this REALISTIC SA-800 amplifier that I bought in a garage sale couple of years ago I used it for a while but got sick of the fact that it just sounds like ****.

Basically everything works but it feels like it just can't produce clear bass, anything that pushes the amp a little over the top just makes everything sound like distortion. The sound is very "MID RANGED" if you see what I mean it sounds like an old radio.But yet I know it probably CAN be a lot better than this. Where can I start to look for defective internal parts?

The amplifier has RCA INPUTS, but what makes me wonder is that it has RCA OUTPUTS and weird connectors aswell for the speakers... both these connectors are in parallel so its ONE OR the Other , does this change anything I mean does it say anything about the OUTPUT it is meant to have.

It's got Channel A and B and a 'QUATRAVOX' option also...

Anyways I wan't to make it sort of a project of upgrading it or finding the culprit. So what sorts of values should I be looking for with my multimeter to see if anything is wrong?

Thanks a lot!

[sreten]

Hi, its not the sort of thing you can turn into a killer hi-fi amplifier, rgds, sreten.

Very impressed with a Pioneer A-300X picked up relatively cheap for a friend :



Effectively a passive pre with power amplifier and a good phono stage.
Needless to say, I'm pretty sure it will slaughter the Realistic on sound quality.

Rest of the system I bought for my friend :
above amp £70 (used)
Systemdek IIX turntable, Rega RB250 arm , Ortofon 520 cartridge, £200 (used)
Marantz quality CD player £30 (used)
Vendor of the above threw in a good Technics tuner and great Technic double cassette deck, £0, (used)
Ebay phono cables - good ones for around £5 to £10 a pair
Around £1.30 a metre decent speaker cables
Wharfedale CR30.4 speakers, floor standers £130 (new)
glass shelf 4 tier hifi rack £100 (new)

One hell of a system for the total cost, easily the best quality per $ I've put together.

[ToyPick]

The picture you posted is an earlier model, mine is the old WOODEN one I agree I'm not expecting hi-fi sound from it I just know it's not meant to be playing this bad. And part of the fun I'm having is trying to "frankenstein it" so to say. I would like to play around with changing some internal parts to have it meet some higher standards and I'm just doing this for fun to see what affects sound levels, quality which is why I'm asking to know what internal parts to look at first in these types of scenarios.

Thanks

Ya that Pioneer amp looks good I'm new to the concept of 'PRE and normal AMP'

PREAMPS have no treble,bass,mid and etc. adjustments? They just power and send to a standard amp?

[ToyPick]

I mean if I replace the caps, pop in some new transistors am I supposed to expect some improvement? I don't want it to wake the neighbors I just want it to play 'right' I don't think it came out of the factory with such poor sound quality?

[sreten]

Hi,

Your chasing your tail IMO. Replacing all electrolytic caps might help.

rgds, sreten.

[sgrossklass]

Is this really an SA-800, not the STA-800 receiver? 'cause I'm drowning in service docs for that one, and it would seem to be the right kind of vintage.

As mentioned, it is likely to need a new set of 'lytics.

[ToyPick]

Well unless my eyes are screwed, the front panel clearly states SA-800.

Why am I chasing my tail ?

Replacing the caps could be an idea, but that seems to be the common troubleshoot for any amp, is there anything else that can partially fail?

I donno if this helps but when I turn the power off the sound fades away into a distortion before completely coming off does this point straight to the caps?

[ToyPick]

So the main CAPS are 2 x 4700MFD they are 'grey' written UNICON JAPAN

If I replace them with the same values with no regards to the type or "volume size" just as long as they are both 4700MFD what parameters may I mess up and what other things can be messed up by capacitors with the right value but not necessarily same type.

Keep in mind this is a learning experience I don't really care if the amp is out of spec after I just want to see and learn a bit here..

Thanks

[sofaspud]

I donno if this helps but when I turn the power off the sound fades away into a distortion before completely coming off does this point straight to the caps?

That doesn't seem like correct operation to me, and suggests caps are involved somehow. I can't pinpoint an exact failure though.

[sreten]

Originally Posted by ToyPick

Why am I chasing my tail ?

Hi,

Because quality comes from good circuitry and good layout.
Loads of mediocre amplifiers sound like that due to layout.

If some of the electrolytics are duff, replacing them will improve things.

Whilst I am of the opinion amplifier differences are often grossly exaggerated,
I am also of the opinion there are large differences between budget amplifiers.

TBH in the above system IMO the Pioneer performs flawlessly and a better
amplifier* simply isn't needed, the system could easily take far more expensive
speakers, though the ones used IMO worked very well for what they are, and
for the price look very nice, which is in the end part of end user satisfaction.


1" tweeter, 6.5" mid/bass, 6.5" PR.

Again JMO but that amplifier would ruin that system, no matter how I modded
it. Its simply not up to the job, its cheap bells and whistles, not hifi IMO.

I was surprised at how well the total system turned out, how good it is
to listen to for a total budget of £500 (ignoring the £100 stand) for a
turntable, arm, cartridge, cd player, fm tuner, double cassette deck,
amplifier and all cables including a mains distributor.

Every source is really good to outstanding for the price, very nice.
Good music doesn't have to be that expensive, with good choices.

I told the guy I put it together for, who could have spent £2000,
lets just see what the cheapest good stuff we can put together
does, he is extremely happy, the quality exceeds his expections.

That amplifier in the above system would degrade everything, not good.
As a system the amplifier cost ~ 1/7, you need the best quality per £.

rgds, sreten.

* or phono stage .....