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Topic: Is this a good amplifier? (Read 8258 times) previous topic - next topic
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Is this a good amplifier?

So I was cleaning my basement up and found an old amplifier my father bought in the 80's. He used it for his vinyl set up but I cannot obtain his old speakers.

It's a "Realistic SA-1000A LL33479" and the model number is 31-1980. I think it's an integrated amp and it also has phono inputs and outputs.

Anybody know if this a good amplifier for both a digital and vinyl set up?

Is this a good amplifier?

Reply #1 –
I can't find any specs on it - do you have any?  Otherwise only one way to find out: try it.
Was that a 1 or a 0?

Is this a good amplifier?

Reply #2 –
It is good enough if it sound good enough. Realistic was never high-end, but the distortion specs are probably adequately low. Having been setting a long time, it might have leaky capacitors, which will produce hum. Another thing to look at is the phono preamp noise level. Hook up any passive speakers and some input sources, and see what you get. If it needs repair, and you can't do it yourself, it is unlikely to be worth the cost.

Is this a good amplifier?

Reply #3 –
Quote from: DigitalMan on
I can't find any specs on it - do you have any?  Otherwise only one way to find out: try it.


I googled some up in a flash. Also, there is an archive of Radio Shack catalogs going back to the early 1950s.

The specs are paraphrased here, along with a pictureL

Radio Shack amp details and picture

The real question is whether or not the usual problems, like electrolytic caps drying out, have happened.

One of these days I should write a piece about how to bench test regular audio gear with a sound card.

Is this a good amplifier?

Reply #4 –
Just to add one small note about electrolytic capacitors...if they are left unused for long periods there can be a gradual degrasation in their characteristics which is separate from the drying out problem. There is some degree of "self-healing" once you apply voltage to them again, over a period of hours or days. So don't judge their quality immediately after turning the equipment on but allow a day or two before deciding that they need to be replaced.

Is this a good amplifier?

Reply #5 –
Beware of bad non-linear distortions if your hearing is sensitive to them: a “less than 1% THD from 20-20,000 HZ” cited in
Radio Shack amp details and picture
http://www.canuckaudiomart.com/details/234...nice_condition_
is a very high non-linear distortion ratio for “modern” “SOLID STATE” amps (because of the spectral “repartition” of their distortion products very different from the “tube” amps) since about 30 years… Especially that it’s cited for 40 watts and may be higher at low power levels where one with critical hearing listening to “critical” sound material (clear female voice, clear piano chords and passages etc. from surely excellent sound sources) may suffer from “squeaking”, “squeaky”, “creaking”, “crunching”, “rasping” etc. sound…

Therefore, you’d listen to some “critical” sound material cited, at low and medium levels, and  carefully analyze the sound…

Is this a good amplifier?

Reply #6 –
I agree that if it works, this amp should be fine!  One other problem you could run into is noisy (scratchy) controls.  If that happens it can usually be fixed by removing the cover and spraying some Tuner Cleaner[/color] into the controls.

Quote
I think it's an integrated amp and it also has phono inputs and outputs.
Yes! An integrated amp is a combination preamp/power amp.  (Or, it's like a receiver withour the tuner).
The multiple switches & controls on the front panel (and multiple input/output connections) indicate the functions of a preamp.  The speaker outputs indicate a power amp.

Quote
a “less than 1% THD from 20-20,000 HZ” cited in
Radio Shack amp details and picture
http://www.canuckaudiomart.com/details/234...nice_condition_
is a very high non-linear distortion ratio for “modern” “SOLID STATE” amps (because of the spectral “repartition” of their distortion products very different from the “tube” amps) since about 30 years… Especially that it’s cited for 40 watts and may be higher at low power levels
  Maybe...  Or, the distortion may be lower!  It says "less than", and this is a power specification, not a distortion spec or a frequency response spec...  The purpose is to tell you that the 40 Watt measurement is real...  That you can put-out 40 Watts over the full audio range without clipping.

I won't to get into a "tube vs. transistor" discussion, but I will reveal my opinion/bias.  As an engineer I appreciate the simplicity, low cost,  elegance, energy efficiency, and quality, of solid state electronics.  And, I have an aversion to passing audio through transformers (required for tube power amps).

Is this a good amplifier?

Reply #7 –
Quote from: DVDdoug on
Quote
a “less than 1% THD from 20-20,000 HZ” cited in
Radio Shack amp details and picture
http://www.canuckaudiomart.com/details/234...nice_condition_
is a very high non-linear distortion ratio for “modern” “SOLID STATE” amps (because of the spectral “repartition” of their distortion products very different from the “tube” amps) since about 30 years… Especially that it’s cited for 40 watts and may be higher at low power levels

It says "less than", and this is a power specification, not a distortion spec or a frequency response spec...  The purpose is to tell you that the 40 Watt measurement is real...  That you can put-out 40 Watts over the full audio range without clipping.

Totally agree.
But in some cases even far BEFORE clipping, the sound MAY be unacceptable.
Quote from: DVDdoug on
Maybe...  Or, the distortion may be lower!

Yes. But it may be much higher! That a potential customer cannot know without measurement of the THD ratio throughout the frequency range at, say, at least three power levels: 1/100 nomimal, 1/10 nominal and nominal power…

I base my opinion on my own experience I had many years ago just in the beginning of a “listening test” of a “solid-state” integrated amplifier “claiming” 0,1% (or if you wish, 0.1%) THD at nominal power, when I couldn’t listen to it for 3 minutes, so crying were its distortions at low listening levels: not only clear vocals, piano passages etc. were “creaking”, but even male voice was “rasping”… There was no need to measure its real distortion ratios…

And a “solid-state” integrated amp with 0,007% THD (within 20…20000 Hz range) in its papers gives me great pleasure in listening at home to any kind of high quality sound programs for years, by its crystal-clear sound at any power level reasonable (with HQ sound programs, of course)…

As, by the way, it was, when listening, in “good old times”, to well-designed “tube” ultra-linear push-pull control amps driving huge 3-way control monitors… Ah, “old times”…
 

Is this a good amplifier?

Reply #8 –
Quote from: Fedot L on
Beware of bad non-linear distortions if your hearing is sensitive to them: a “less than 1% THD from 20-20,000 HZ” cited in
Radio Shack amp details and picture
http://www.canuckaudiomart.com/details/234...nice_condition_
is a very high non-linear distortion ratio for “modern” “SOLID STATE” amps (because of the spectral “repartition” of their distortion products very different from the “tube” amps) since about 30 years… Especially that it’s cited for 40 watts and may be higher at low power levels where one with critical hearing listening to “critical” sound material (clear female voice, clear piano chords and passages etc. from surely excellent sound sources) may suffer from “squeaking”, “squeaky”, “creaking”, “crunching”, “rasping” etc. sound…


Ironically, the relatively high THD spec might even be good news!

First off, the idea that this component would include a risk of having audible distortion is probably a misapprehension. As others have pointed out, a component  that is rated  at 40 watts  "less than 1% THD from 20-20,000 Hz could probably just as easily be rated at "30 watts at less than 0.1% THD from 20-20,000 Hz.".  At typical operating levels and signals, the actual THD might be 0.03% or less.

I did some more checking and found the SA1000 in the 1975 Radio Shack Catalog at 1975 Radio Shack Catalog please see page 15. 

In 1975 solid state was pretty well sonically perfected, but (and this is the good news) it was before manufacturers started trying to build equipment specified to have less than say 0.02% THD.  You'll notice that today, manufactuerers as a rule do not spec equipment at 0.02% THD. This is because in the day (ca. 1985)  0.02% THD was often obtained at the expense of hard-to-spec but important real-world features like "Stable into a reasonable selection of different kinds of load".

Today, your typical SS power amp might have 0.02% THD as long as you don't drive it into clipping. However, the equipment is intentionally speced for far higher levels of distortion so that the power ratings can be inflated. 

One of the most frustrating questions to answer is from someone who wants to know whether to buy amp A that is speced at 0.05 % THD or amp B that is speced at 0.08% THD. In all liklihood, if you run them at slightly lower power levels, they'd both have less than 0.02% THD.  This is all about squeezing the last watt onto the spec sheet, while 10 or even 20% differences in actual power output have minimal to no audible real-world effects.