pustelniakr said:
Uh, uh, uh... :nono: :nono: :nono:
This is just a "Pioneer" competition.
Retro
Pioneer SX-1980 Transistor Modification
- Thread starter EchoWars
- Start date
Uh, uh, uh... :nono: :nono: :nono:
This is just a "Pioneer" competition.
Retro
Retro Stereo said:Uh, uh, uh... :nono: :nono: :nono:
This is just a "Pioneer" competition.
Retro
But...but...but...
Rich P
crooner
Tube Marantzed
I wouldn't trust those old magazine reviews too much. That graph is somewhat misleading. It's measuring IM vs power output, IIRC.
There's obviously some degree of current limiting applied to the design. Otherwise the outputs would self-destruct. I am sure the Marantz 2600 has some form of current limit, otherwise output at 4 ohms would have to double.
There's obviously some degree of current limiting applied to the design. Otherwise the outputs would self-destruct. I am sure the Marantz 2600 has some form of current limit, otherwise output at 4 ohms would have to double.
bond said:
crooner
Tube Marantzed
Also, I am sure Glenn has superior test equipment than Julian Hirsch, CBS Technology Center, Len Feldman and other testers/reviewers of the late 70s.
Proof is the THD+N figures. Back then it was impossible to measure the low figures EchoWars got (i.e. "270wpc @0.0085% THD+N (1KHz)").
The fact that the unit tests so well is a testament to it's excellent design.
Proof is the THD+N figures. Back then it was impossible to measure the low figures EchoWars got (i.e. "270wpc @0.0085% THD+N (1KHz)").
The fact that the unit tests so well is a testament to it's excellent design.
Most of the distortion analyzers in use today are of the same vintage as the gear we are testing. I can't speak for EW's gear.crooner said:
Rich P
crooner said:
Well, the IM shoots straight up at 240 watts (4 ohms), so one must assume that clipping is very near the 240 watts IM distortion, making the SX-1980 one of the few large amps that cannot even equal its 8 ohm power output into 4 ohms. Even the 2385 (185 watts into 8 ohms) had an offical FTC rating of 250 watts, 4 ohms @ 0.1 IM distortion, putting it at the SX-1980 level in terms of 4 ohm output. The SX-1250 had an official FTC rating of 200 watts @ 0.1% IM, so even that receiver is too close for comfort to the SX-1980, which (on paper) appears to be a massive improvement (270 vs. 160 watts) to their old TOTL, but could only be 20-40 watts greater at 4 ohms than the 1250.
I guess what I am saying is that (in my opinion), Pioneer took advantage of the 8 ohm rating system (specsmanship) to make the SX-1980 appear to be a massive powerhouse, when it actually performed surprisingly poor into real world loads below the 8 ohm dummy resistor load. Virtually every speaker dips below the 8 ohm point somewhere in its frequency range - let alone running any 8 ohm speakers in parallel (I measure 2.2 DCR for my setup). This is not normal current limiting, its a current inadequacy - all modern amps should at least equal their 8 ohm ratings into 4 ohms. Furthermore, the dynamic headroom was a mere 1/4 db! according to the lab, so no reserve here either, its basically a hard limit at 300 watts clipping into 8 ohms (+/- 20 watts depending on AKer's tests or mag test), with virtually no peak reserves even at 8. If someone had traded their SX-1250 for an SX-1980 and had 4 ohm speakers, the actual power difference would be inaudible! (0.8 db difference between 200 and 240 watts and that is assuming the SX-1250 barely meets its 200 watt, 4 ohm spec, it probably has at least 10-20 watts headroom from the rating, placing it within 20-30 watts of the SX-1980).
With the power transistor mods, I was really curious if the poor 4 ohm performance improved since he changed both the drivers and outputs and I think these were responsible for the low current output. If one can mod an SX-1980 so its 4 ohm output could be increased dramatically, it would be worthwhile to toss the (still good even) outputs and replace per his mods, like removing the critical path holding a design back.
As for the difference in test equipment - old or new, both can detect clipping equally well..........
Bond
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You know, I often wondered why my AR-9's (4 ohm speakers) sucked the juice right out of my SX-1980, but my SPEC 2 could give them a proper ride. This would be a good explanation of that phenomena.
Retro
Retro
My dummy load is made up of four 4-ohm 200W resistors. I normally run two of them series for each channel to give me 8 ohm 400W capability. I can parallel these two pairs for 4 ohms @ 800W and test one channel, but...
1. I'd be very suprised if the 1980 could not produce well over 300W into 4 ohms, and
2. Unless I can load both channels with a 4 ohm load, I don't feel the test is valid, so I shan't bother, and
2. I don't care one way or the other. Curious maybe, but not overly so.
1. I'd be very suprised if the 1980 could not produce well over 300W into 4 ohms, and
2. Unless I can load both channels with a 4 ohm load, I don't feel the test is valid, so I shan't bother, and
2. I don't care one way or the other. Curious maybe, but not overly so.
EchoWars said:
C'mon Glenn, this has come up a few times before and I think it needs to be addressed once and for all. Keeping that in mind, I'm donating $50 towards the purchase of more dummy loads for you. If we can get a few more people to pony up a few $$$ we will never have to wonder again. By the way, how many more dummy loads do you need, four? And how much would they be?
Enquiring minds want to know..... :scratch2:
Retro
crooner
Tube Marantzed
I doubt the SX-1980 or Marantz 2600 would be considered "modern amps", they are nearly 30 years old!
As I said before I would take those measurements with a grain of salt. Leonard Feldman of Audio Magazine in his review of the SX-1980 (Sept 1978, page 73) states a measured IHF Dynamic Headroom figure of 2.3 dB which translates to 460 watts per channel of momentary output. Far more than the figures from High Fidelity. Given that the IHF measurement standards were devised mainly by Mr. Feldman, I tend to agree with his findings even though both are probably far from accurate.
As I said before I would take those measurements with a grain of salt. Leonard Feldman of Audio Magazine in his review of the SX-1980 (Sept 1978, page 73) states a measured IHF Dynamic Headroom figure of 2.3 dB which translates to 460 watts per channel of momentary output. Far more than the figures from High Fidelity. Given that the IHF measurement standards were devised mainly by Mr. Feldman, I tend to agree with his findings even though both are probably far from accurate.
bond said:
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crooner
Tube Marantzed
Too bad the SPEC 2 was never reviewed by the audio mags of the day. I would have loved to see the IM vs Power graph for it.
But guessing from the lack of 4 ohm FTC ratings, it seems a similar degree of current limiting was employed in it as well.
I do have a 1978 review of the later SPEC 4 by High Fidelity magazine and (apparently) they found it produced peaks of 350 watts into 8 ohms without clipping. This puts it right there with the SPEC 2 in raw power delivery.
But guessing from the lack of 4 ohm FTC ratings, it seems a similar degree of current limiting was employed in it as well.
I do have a 1978 review of the later SPEC 4 by High Fidelity magazine and (apparently) they found it produced peaks of 350 watts into 8 ohms without clipping. This puts it right there with the SPEC 2 in raw power delivery.
Retro Stereo said:
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crooner
Tube Marantzed
I don't see what your point is in trying to knock down the SX-1980 in a SX-1980 thread.
I believe the Marantz 2600 is a nice design. If I see a thread about it, I try to be constructive. I even suggested a mod to prolong the life of the scope on a recent one. I could have gone on and on reciting an old Pioneer ad bashing the Marantz. But I never worked for Pioneer, I have no interest in doing so. And my thoughts and opinions are basically my own. Not entirely from old magazine reviews.
I was even wondering if you were related somehow to that fella Trevor Wilson of Audio Asylum fame!
I believe the Marantz 2600 is a nice design. If I see a thread about it, I try to be constructive. I even suggested a mod to prolong the life of the scope on a recent one. I could have gone on and on reciting an old Pioneer ad bashing the Marantz. But I never worked for Pioneer, I have no interest in doing so. And my thoughts and opinions are basically my own. Not entirely from old magazine reviews.
I was even wondering if you were related somehow to that fella Trevor Wilson of Audio Asylum fame!
bond said:
crooner said:
One of the reasons I'd like to help buy Glenn some more dummy loads is exactly what you're alluding to here. You see, I own two SPEC 4's as well, and there is no way they even come close to the 4 ohm overhead that the SPEC 2's have. I'll bet the farm on it, but the only way to prove it, is to have them properly rated by Glenn.
Retro
crooner
Tube Marantzed
I guess we will have to wait until Glenn measures one.
Based on your experiences with the SPEC 4, it seems there was something amiss with the way High Fidelity magazine (or CBS Tech Center for that matter) was testing this equipment. With the SX-1980 they basically underrated it. The SPEC 4 review seems overly optimistic!
I said it. Read the old reviews strictly from an historical perspective. Accurate they are not!
Based on your experiences with the SPEC 4, it seems there was something amiss with the way High Fidelity magazine (or CBS Tech Center for that matter) was testing this equipment. With the SX-1980 they basically underrated it. The SPEC 4 review seems overly optimistic!
I said it. Read the old reviews strictly from an historical perspective. Accurate they are not!
crooner said:
Actually I have owned a 2600 since 1979, with #2 2600 a few years ago - so my thoughts about it (them) are based on 27 years of ownership, not magazine specs
This is a constructive post as well - my first really good piece of brand new gear was the SX-1250 and I loved it (paid 520.00 in 1977).
I do like the looks of the sx-1980 and think EchoWars is in a position to shed some light on whether a major performance increase can be had with just a modest amount spent in parts for the SX-1980. Very rare opportunity to see what an SX-1980 can do with different output section.
Bond
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crooner said:
I know you're probably not referring to me. I am curious more than anything else. Having owned all these units and running them into the same pairs of speakers for a number of years, I know which amps/receivers have the 4 ohm overhead, and which ones don't, but who would believe me without properly rating what I hear. It can be done, so why not do it.
All that needs to be done is to rate the SX-1980, SPEC 2, and SPEC 4 at 8 ohms and 4 ohms. I know Glenn will be getting another SPEC 2 soon from Army, I can send him one of my SPEC 4's, and I'm sure he'll have an SX-1980 soon enough. Piece of cake right Glenn?
Retro
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