why a recap makes no difference

[restorer-john]

....enter, the 1987-1990 pioneer a-717. just wow. its bass is so fluid, natural, and reverberating. you can hear some of the most delicate sounds with utter precision. i would have to imagine its close to what people like about tube amplifiers. the a-910 barely scratches the surface of the low notes that the pioneer can just flood the room with from sheer woofer movement. the pioneer made two bose 201’s send heavier low frequency tremors through my floor than the nec can with both bose 201’s and mcs 3895 bass reflex speakers. its almost as if the nec is stationed above ground trying to lift the lower frequencies out whereas the pioneer was already underneath the ground pushing the low frequencies out from underneath themselves..

so does that mean the super healthy, rotel slaying, a-910 needs a recap? or does it mean the a-717 is just a higher fidelity amplifier than the 910 and MUCH more than the rotels and EXPONENTIALLY more than anything less than the rotels that led me on this quest to better conquer my existing gear??...

I have a mint in box Pioneer A-717, bought when they were run out back in 1989/90, an A-616 (it's smaller brother) and the big one, the A-91D. It is true, they have a phenomenal bottom end, but they are ruler flat. I am about to run some tests on my A-91D as soon as I make space on my bench and practice weight lifting (it's 29.9kg).

Rotels are lovely, but they all rolloff the low octaves, regardless of their vintage- it is a Rotel characteristic- very British in their rolled off top and bottom ends.

Bear in mind, frequency response specifications can be very misleading. They are all specified at 1 Watt. What happens with many amplifiers is the bottom and top ends roll off more and more as the output power increases towards rated power. Power bandwidth specs help a little, but even they are deceptive as it is a spec where half power can be achieved, not full power.

Basically, full power frequency response tests are needed. Nobody really does them, but I can tell you, they sort the amplifiers out faster than any other test. And, in reference to this thread, it's the high power sweeps that show the differences with recaps. THD improves often very significantly with recaps, especially where VAS stage rails were getting modulated by power stage current demands.

Back to the thread subject.

There is no doubt that sensible replacement of aging electrolytic capacitors is warranted on a lot of vintage gear. Improvements in many areas of performance are easily demonstrated and measurable. Some of the more recent vintage gear will not show much if any measurable improvement, but nobody could argue that high quality brand new capacitors are preferable to 20-30 year old capacitors. Preventative maintenance.

 

[yotems]

I have a mint in box Pioneer A-717, bought when they were run out back in 1989/90, an A-616 (it's smaller brother) and the big one, the A-91D. It is true, they have a phenomenal bottom end, but they are ruler flat. I am about to run some tests on my A-91D as soon as I make space on my bench and practice weight lifting (it's 29.9kg).

Rotels are lovely, but they all rolloff the low octaves, regardless of their vintage- it is a Rotel characteristic- very British in their rolled off top and bottom ends.

i did notice that about this 717, it is very flat. i have to have the bass up all the way and the loudness on in order to bring out that low end but the thing is the amp was ok with those settings and seemed to compensate the loudness as you increased volume. the only loudness i think ive ever heard that doesnt diminish detail.

i would bet this would be the amp to buy really good speakers for

i recently sold a rotel rx-2002 (1979) and that thing had more low end than my a-910! it was another one of those amps that i feel could have been GREAT with crispy sonics but i did not feel comfortable trying to experiment with recapping it as it looked like a real headache to work on, but that thing certainly meant business.

and yeah isnt the a91d an a888 with an onboard dac? i was googling a lot of pictures of those pieces when i found this a-717. i noticed they are 60 some lbs lol 80v 28000uf caps as well i believe?

i sure would like to try those as well as some of nec’s a10 models or even an a11.. 50+ lb 60watt per channel integrateds

 

[restorer-john]

...i have to have the bass up all the way and the loudness on in order to bring out that low end but the thing is the amp was ok with those settings...

Bass all the way up, and loudness? I think you need better speakers.

 

[c.coyle]

It's the design that matters. I think the only capacitors that can affect sound quality are those in the signal chain, and a well designed amp will have as few as possible. I know many of you disagree with this.

Still, I replace all electrolytics on old gear I pick up, because I enjoy doing it, it's my gear, it's usually cheap, and it's a pain to test individual capacitors.

 

[steveUK]

except for the power caps, the total cost of a recap is oft in the $10 range if you buy in bulk from mouser (i.e. get the 25+ price not the 1-9 price). $10 for parts that are worlds better than the ones replacing. This is so much a no brainer. its sorta like rebuilding your muscle car engine but leaving the rings in because they look good and aint in pieces.

I know this topic comes up every 3-6 months and gets beaten like an expired equine, but a refresh, refurb or restore of any machine dictates juice filled aluminum be yanked and replaced. anything less is just laziness.

Yeah, you're only mentioning the 'cost' in monetary terms there. That's the least of your worries with a big receiver. Firstly, the total time to recap can be many, many hours, and secondly, the amount of very difficult (even frightening) dismantling that very often has to be performed can be daunting and very difficult. There's no way that that lot is a no brainer. Well actually, depending on your take on the phrase 'no brainer', it may well be just that..

 

[steveUK]

Its cheap, and while you have it apart, why not? I have found enough old caps with corroded leads and even corroded to the point where the corrosion has eaten through the leads. Usually due to the glues they used to secure them. For the most part I only work on my own stuff and if I have to replace a few I just replace them all while im at it for peace of mind. If its something I'm going to keep I don't want to have to open it up later down the road. To each his own I guess. Nothing wrong with just replaceing failed componants either.

I like your general views, I like what you're saying; each to his own etc etc. Not just that, you are not trying tell or convince everyone that it is 'better'.

 

[steveUK]

ive had full electrolytic ( except a few tuner boards) recaps on 15 amps/receivers all 40-55 years old on 3 of them there was a night and day difference of the rest half pretty much sounded the same but had a lot more punch the other half sounded the same to me. None of them sounded worse. i dont know how many were bad but i dont trust 40 year old caps and i feel better having it done.

That does not prove that the 'full recap' was responsible for the "night and day difference" that you report. And as has been said many times, that 'night and day improvement' is very subjective and also subject to psychoacoustic effects. But the point is, amongst all of those caps that were replaced there were probably/maybe just a couple that were badly degraded or just plain faulty. Those are the two caps that other people would have changed and achieved the same result. Of course, you have to be a nifty audio electronics engineer to fault find complex circuits down to component level. And that's sometimes the reason why complete recaps are done; the repairer/restorer is unable to locate individual faulty components. Also pros don't want returns. None of this means that a full recap is 'better'; it is demonstrably often done for other reasons such as those mentioned.

 

[ConradH]

Everybody wants a universal applies-to-all-units rule of thumb. There just isn't one. I've seen receivers where almost every cap was bad in one way or another. I've seen others of the same age or older where none were bad. When I talk good and bad, I'm including every test you'd want to do- value, dissipation factor and DC leakage, all at full operating voltage. Done well, a full recap isn't going to hurt anything, and the unit should perform well far into the future- assuming you correct all the other problems an old unit is apt to have. Done poorly, all bets are off. I'll also say that nothing (me included) is getting any younger. A lot of equipment I might have left alone ten years ago, I wouldn't today. In general, if I pull a board for some other reason, or if the board is easy to pull to begin with, I'll invariably recap it.

 

[Chrisxo55441]

That does not prove that the 'full recap' was responsible for the "night and day difference" that you report. And as has been said many times, that 'night and day improvement' is very subjective and also subject to psychoacoustic effects. But the point is, amongst all of those caps that were replaced there were probably/maybe just a couple that were badly degraded or just plain faulty. Those are the two caps that other people would have changed and achieved the same result. Of course, you have to be a nifty audio electronics engineer to fault find complex circuits down to component level. And that's sometimes the reason why complete recaps are done; the repairer/restorer is unable to locate individual faulty components. Also pros don't want returns. None of this means that a full recap is 'better'; it is demonstrably often done for other reasons such as those mentioned.

i didnt say a full recap was better i was just stating the results that i got from full recaps. and half didnt make any difference. electrolytic's have a limited life, can you go through a receiver and check them all and if they are good does that mean they wont fail in a year or two? i would think as long as your in there its just as easy to replace them all and not worry about it in the future . Im not a tech but think having one check to see if they are up to spec even if it could be done would cost just as much as just replacing them. What i said was that it makes me feel better not having to worry about it so i just have them all replaced and i got a few WOW moments in return.

 

[steveUK]

Indeed. The quality or goodness of the caps after 40 years depends to some extent on the lifestyle that they (and the host set) have led. If the set has been used in a red hot bakery with high humidity it (and the caps) will likely be in a much worse state than the set that has sat on the sideboard in a nice clean house, no smokers, 'no extremes of weather', never played too loud, etc etc for the past 40 years. And then of course, just to buck the trend, you get a set that looks like it has been through WW3, is covered in dust and smoke residue and works perfectly.

 

[steveUK]

i didnt say a full recap was better i was just stating the results that i got from full recaps. and half didnt make any difference. electrolytic's have a limited life, can you go through a receiver and check them all and if they are good does that mean they wont fail in a year or two? i would think as long as your in there its just as easy to replace them all and not worry about it in the future . Im not a tech but think having one check to see if they are up to spec even if it could be done would cost just as much as just replacing them. What i said was that it makes me feel better not having to worry about it so i just have them all replaced and i got a few WOW moments in return.

But it's not a simple matter of "..as long as your in there its just as easy to replace them..". It is not like that, it is not "easy" by any stretch of imagination. Normal levels of restoration do not generally require the same amount of dismantling as is needed to perform a recap. By your own admission, you're not a tech, some of these large sets are like a large, complicated Rubik's cubes to 'crack' and break down into individual assemblies in order to access PCBs. And even if it was 'that easy' I personally wouldn't perform a recap for the sake of it; future proof reasons, whatever. But people do, that's fine. As for 'wow moments', you get just the same effect when you change a (single) faulty cap.

 

[drumbum]

Indeed. The quality or goodness of the caps after 40 years depends to some extent on the lifestyle that they (and the host set) have led. If the set has been used in a red hot bakery with high humidity it (and the caps) will likely be in a much worse state than the set that has sat on the sideboard in a nice clean house, no smokers, 'no extremes of weather', never played too loud, etc etc for the past 40 years. And then of course, just to buck the trend, you get a set that looks like it has been through WW3, is covered in dust and smoke residue and works perfectly.

I think "high humidity" would actually help with length of service life.

 

[blhagstrom]

it's a fact that e-caps age
they are Chemical based to keep the aluminum clean.
they are sealed but do dry out
I have seen rotted off legs, either the chemical or glue or just age.
I've found enough failed ones in "working, sort of" gear that there is no question that they are the weakest link.

if a recap makes no difference in sound, either the unit was still working well or your ears are not working well.

fwiw, a total recap does not make it sound stunningly better.
the difference can be minor unless the cap was totally failed.

if your source material and or speakers are lousy, a recap won't do much.

 

[steveUK]

I think "high humidity" would actually help with length of service life.

Well, for the caps yes, because they dry out with heat and time combined. Saying that, I don't think that truly high humidity levels would do them much good, the legs would corrode etc. And equally bad for other things such as switch contacts, pots, PCB tracks etc.

 

[Chrisxo55441]

But it's not a simple matter of "..as long as your in there its just as easy to replace them..". It is not like that, it is not "easy" by any stretch of imagination. Normal levels of restoration do not generally require the same amount of dismantling as is needed to perform a recap. By your own admission, you're not a tech, some of these large sets are like a large, complicated Rubik's cubes to 'crack' and break down into individual assemblies in order to access PCBs. And even if it was 'that easy' I personally wouldn't perform a recap for the sake of it; future proof reasons, whatever. But people do, that's fine. As for 'wow moments', you get just the same effect when you change a (single) faulty cap.

So you you can check the specs of all the capacitors in an amp or receiver without pulling the boards? i didnt know that i assumed they needed to be removed. but then ive never asked to just have them checked, live and learn. still doesnt change how i feel about 40+ year old caps, dont trust them never will

 

[steveUK]

So you you can check the specs of all the capacitors in an amp or receiver without pulling the boards? i didnt know that i assumed they needed to be removed. but then ive never asked to just have them checked, live and learn. still doesnt change how i feel about 40+ year old caps, dont trust them never will

No, no. The overall performance of the set tells you if there's a fault. Then you find the fault or faults. It doesn't have to be a cap.

 

[leesonic]

Human beings are not pieces of test equipment. What tests the same may not sound the same, otherwise how would you explain how two different amplifiers that test the same but sound different? All these "doesn't need to be recapped" threads just serve to further cheapen the hobby and put people off paying other people fair money for their time to restore this stuff. I have personally tested known and respected brand caps that are WAY off spec, the sound performance of the equipment surely MUST have suffered because of these. If you're going to pull a cap to test it, why put the 30 year old one back? If it doesn't fail or drift out of spec today, maybe it will next week, or next year? Some of the most respected people on here do this kind of restoration work : @markthefixer, @avionic, @Hyperion, @Leestereo to name but a few. Are you tell me they are ALL wasting their time?



Lee.

 

[yotems]

yeah to capitalize on the “while youre in there” theory... ive sold some beloved units because they were of size and complexity i didnt see myself ever feeling comfortable or motivated enough to subject myself to the task of recapping them. the amp i recapped was a 33 lb integrated amp that seemed built to come apart for service and it was so straightforward and simple.

my speakers and source are not good by any means but ive got gear that can make them sound good. when i did the recap i didnt just listen to the amp i recapped to get a before and after of it alone. i compared it to all of my other amps for a long time and would swap it back and forth between a few that their sound had become predictable for me so i had more references to compare to.

as in set up a blindfold test where you played an mcs 3285 or rotel ra-971 through one of my listening spaces i could easily tell you which it is

i do think it got better but like i said i was just expecting it to surpass or at least reach the same level of crisp as those i compared it to.

i think the conversation now becomes, recap? ...or research a better piece of gear?

 

[llwhtt]

OR the unit has other problems. Capacitors are NOT a cure-all for all problems. This is where many people here on Audiokarma and other forums fall short NO TEST EQUIPMENT! I've been doing this a long time and can honestly say I would be lost without my test equipment. Maybe you can hear some distortion but what type of distortion? Test equipment will tell you what is going on visually. Throwing parts at a unit is a waste of time, you may or may not fix it and you definitely won't learn anything.

 

[yotems]

OR the unit has other problems. Capacitors are NOT a cure-all for all problems. This is where many people here on Audiokarma and other forums fall short NO TEST EQUIPMENT! I've been doing this along time and can honestly say I would be lost without my test equipment. Maybe you can hear some distortion but what type of distortion? Test equipment will tell you what is going on visually. Throwing parts at a unit is a waste of time, you may or may not fix it and you definitely won't learn anything.

even with my limited abilities i dont feel the whole recap was a waste of time by any means. it was actually entertaining at the time and it fine tuned my soldering skills as well as my overall ability to be attentive to detail. i personally dont feel im hearing anything wrong with the amp as it runs very cool on both channels seemingly healthy and reads very healthy dc offset wise. i just think im hearing the amplifiers age. i cant imagine amplifiers of the 70’s were as good at many things newer amplifiers were/are simply because the music of the time did not demand for such performance

but i did start this thread based on the idea that there may be other components within the amplifier responsible for the aged sound.. so i guess going further in depth with that would stay a bit more true to the OP

considering these old nec batwing transistors were pretty much phased out before the 80’s i have to imagine they could be improved upon.. but i doubt its simply a matter of swapping outputs and drivers and firing it up