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Does an amplifier degrade over time?

post #1 of 22
Thread Starter 
I've got a 15-year or so old amplifier (Yamaha AX-870), which is quite heavy, and I'm wondering if it's worth buying a new one, soundwise.

I heard from a sound technican that non-tube amps degrade over time. Is this true?
post #2 of 22
Quote:
Originally Posted by Bruce Willis View Post

I've got a 15-year or so old amplifier (Yamaha AX-870), which is quite heavy, and I'm wondering if it's worth buying a new one, soundwise.

A good question that lacks a general answer.

Quote:
I heard from a sound technican that non-tube amps degrade over time. Is this true?

The best answer is that SS amps may degrade over time. Or not.

When amps degrade, there are some clearly measurable consequences.

Frequency response, especially in the bass, can be lost as capacitors degrade. The ability to produce full rated output with good frequency response and low distortion may degrade. Switches and potentiometers can start failing or become noisy.

Or, an audio component might get to be 40 years old, and still meet original spec.

YMMV.

How to tell?

A listening comparison with a similar known good piece of equipment can work if the comparison is carefully done. If carelessly done, a sound quality comparison test can be expected to create the impression that the two pieces of equipment sound different.

A thorough bench test is probably the best way to tell if a component has lost its original sonic sheen. Trouble is, you can spend more money paying a technician for a good bench test than the equipment is worth. Or close to it.
post #3 of 22
Everything degrades over time, regardless if it is solid state or tube based unit. The question is what degree. Some amplifiers from 1980s still show better measured results than you can find in new ones today. Generally you should only consider top of the line models from the past. They were designed with lifespan of 10-15-20 years in mind, and many still work perfectly. If you want to make sure that your amp works well, get it tested. But it will cost you 2-3 billable hours in any seriouse shop. It is up to you decide if it worth the expense.
post #4 of 22
Thread Starter 
Thanks for the informative replies!

Regarding the concrete reason I asked: the Yamaha stereo amp I have would costs now about $1100 I guess, taking inflation into account. It is 2x110W @8ohm, 0.015THD. It has pre in/outs.

Now I'm thinking of buying a receiver. My only source of music is my computer, and I'm expecting a substantial improvement of quality if I feed it a digital sound over HDMI 1.4.

Also, I might go for a surround system soon.

So I doubt if I should buy the cheapest receiver that has a pre-out, and use the Yamaha as end-amplifier for stereo use, or a better receiver, and not use the Yamaha at all.
post #5 of 22
Quote:


Regarding the concrete reason I asked: the Yamaha stereo amp I have would costs now about $1100 I guess, taking inflation into account.

Careful—inflation doesn't affect electronics the way it affects other goods. I'll bet Yamaha makes a similar product today for about what you paid for it.

Quote:


Now I'm thinking of buying a receiver. My only source of music is my computer, and I'm expecting a substantial improvement of quality if I feed it a digital sound over HDMI 1.4.

Why?

Quote:


Also, I might go for a surround system soon.

In that case, I'd definitely hold off until you're ready to make that decision, and you can choose an AVR based on your needs/budget.
post #6 of 22
Quote:
Originally Posted by ap1 View Post

Everything degrades over time, regardless if it is solid state or tube based unit. The question is what degree...

Entropy at work.
post #7 of 22
Thread Starter 
Quote:
Originally Posted by mcnarus View Post


Quote:
Originally Posted by me View Post

Now I'm thinking of buying a receiver. My only source of music is my computer, and I'm expecting a substantial improvement of quality if I feed it a digital sound over HDMI 1.4.
Why?

The situation is as follows: my whole movie and music collection is stored on my computer, both 100% lossless audio. The amp is connected with a cinch->thin cable->3.5mm jack to the (onboard) soundcard of the computer. So the digital signal is first converted by cheap D/A converters, and then the analog signal has to survive the connectors and the thin cable.

I think it would be better to feed the amp a digital signal and do the D/A conversion there.
post #8 of 22
Quote:


The situation is as follows: my whole movie and music collection is stored on my computer, both 100% lossless audio. The amp is connected with a cinch->thin cable->3.5mm jack to the (onboard) soundcard of the computer. So the digital signal is first converted by cheap D/A converters, and then the analog signal has to survive the connectors and the thin cable.

Well, the cheap D/A converters in your computer are probably no worse than the converters in any AVR. To be more precise, they may be measurably worse, but they won't be audibly worse. These chips are commodity products now. Even the cheapest are very, very good.

As for the connection, jeez, do we have to go through the wire-is-wire thing again? Unless that wire is dozens of yards long, you've got nothing to worry about there.

The one thing that might make a difference is if there's a lot of noise in your computer that's compromising the analog signal. Can't say, although I get the sense that problem is greatly exaggerated.

In short, if you are expecting a substantial improvement, you will be disappointed.

So my advice is, put away your wallet, enjoy what you have now (it's probably fine), and save up for when you're ready to go multichannel, so you'll be able to do it right.
post #9 of 22
Quote:
Originally Posted by Bruce Willis View Post

The situation is as follows: my whole movie and music collection is stored on my computer, both 100% lossless audio. The amp is connected with a cinch->thin cable->3.5mm jack to the (onboard) soundcard of the computer. So the digital signal is first converted by cheap D/A converters, and then the analog signal has to survive the connectors and the thin cable.

I think it would be better to feed the amp a digital signal and do the D/A conversion there.

It would be a desirable situation on theoretical grounds. If you can do it for a low cost, then it could be a good idea. It would probably be the best idea if you were going multichannel.

I would not expect any sort of a dramatic or even noticable sound quality advantage unless your computer's converters are say from 4 years ago or earlier.
post #10 of 22
Quote:
Originally Posted by Bruce Willis View Post

I've got a 15-year or so old amplifier (Yamaha AX-870), which is quite heavy, and I'm wondering if it's worth buying a new one, soundwise.

I heard from a sound technican that non-tube amps degrade over time. Is this true?

I generally concur with Arny in post 2. My own personal experience in three decades of working on SS amps is that (especially earlier generation) electrolytic, and some tantalum and ceramic, caps degrade over time. I generally replace these in restorations of units > 20yo as a matter of course, especially PS caps.

The actual SS devices tend to be very reliable, providing they have not been run too hot too often, or the designer didn't run them too close to their design limits. this will vary on a design by design basis, but some googling and reading of sites like Audiokarma that tend to have a vintage bent, should indicate whether a given design is prone to aging issues.

Yamaha generally made very solid amps (I own many) and I wouldn't recommend replacing it if it is not having issues.
post #11 of 22
Quote:
Originally Posted by A9X-308 View Post

I generally concur with Arny in post 2. My own personal experience in three decades of working on SS amps is that (especially earlier generation) electrolytic, and some tantalum and ceramic, caps degrade over time. I generally replace these in restorations of units > 20yo as a matter of course, especially PS caps.

IME the PS caps are among the longest-lived, while its the small coupling caps that have the worst track record for drying up and falling down on the job.

Quote:


The actual SS devices tend to be very reliable, providing they have not been run too hot too often, or the designer didn't run them too close to their design limits. this will vary on a design by design basis, but some googling and reading of sites like Audiokarma that tend to have a vintage bent, should indicate whether a given design is prone to aging issues.

There is a long term failure mode of SS devices where overloading or overheating them causes progressive loss of current gain. First distortion rises, and then power of any kind starts falling off. Sometimes amps with multiple paralleled output devices are designed to fail safe, and keep on working even when some output devices short out. The first sign of that trouble is significantly reduced power output, particularly into low impedances.

SS device durability has improved greatly since the early 60s. In the early 60s there were actually power amps rated at say 25 wpc that used a pair of output devices with 25 watt maximum power dissipation. I don't know who would spec such a thing, unless totally desperate!

The next generation of equipment jumped to the same number of devices each rated at 4-5 times as much power. Then, amps started showing up with pairs and quads of output devices in parallel.

Between the continuing progress in SS devices, and the fact that some of the old habits were excessive even in the day, I don't see any need for power amps with literally dozens of large devices per channel. I've had one of these on my bench and in my listening situation, and they only make sense as audio sculpture.

OTOH if you have one of these old amps to work over, putting modern devices into the old sockets will increase the safe operating area by 2 or 3. Open up the protection circuits accordingly, and a marginal amp can become a winner with tough loads.
post #12 of 22
Quote:
Originally Posted by arnyk View Post

IME the PS caps are among the longest-lived, while its the small coupling caps that have the worst track record for drying up and falling down on the job.

My service and personal resto work has been predominantly inside pro amps for many years, and typically the only coupling cap(s) are in the opamp at the front end that does the Bal/SE conversion between this and the actual power amp stage input. Some designs place the PS caps too close to the main heat source, output devices and heatsinks which reduces their performance and life. It's been measuring the amp performance over years that has proven it to me.

I replace my PS caps when I have the unit apart for a long term service of an older unit (15-20yo) to save me having to do it in the nearer future and to ensure it doesn't fail earlier than expected and take some expensive drivers with it. On the )very rare these days) occasion I do a job for a paying customer, I suggest it as it will be cheaper now than paying for me to disassemble and reassemble later, if they want to use it for many more years. Their choice, and often requested outright.



Quote:
Originally Posted by arnyk View Post

There is a long term failure mode of SS devices where overloading or overheating them causes progressive loss of current gain.

Though not stated I was thinking about how close to the edge of SOA a device will be used, WRT V, I and temperature. More modern devices and designs generally have much more capability in the devices and are designed to work well within device SOA and so in my experience, overall more reliable unless abused or incompetently designed.
post #13 of 22
USB to HDMI video and audio output devices are available for under $100. I've never tried any of them, so I can't comment on their reliability. Still, if you're interested in getting into HD surround-sound audio, they're something to consider. Reasonable AVRs are available for only a few hundred dollars. Of course, you should spend several times that for quality surround-sound speakers.
post #14 of 22
Quote:
Originally Posted by mcnarus View Post

Well, the cheap D/A converters in your computer are probably no worse than the converters in any AVR. To be more precise, they may be measurably worse, but they won't be audibly worse. These chips are commodity products now. Even the cheapest are very, very good.

As for the connection, jeez, do we have to go through the wire-is-wire thing again? Unless that wire is dozens of yards long, you've got nothing to worry about there.

The one thing that might make a difference is if there's a lot of noise in your computer that's compromising the analog signal. Can't say, although I get the sense that problem is greatly exaggerated.

In short, if you are expecting a substantial improvement, you will be disappointed.

So my advice is, put away your wallet, enjoy what you have now (it's probably fine), and save up for when you're ready to go multichannel, so you'll be able to do it right.

I agree with everything mcnarus said, except for the expectation thing - most users who jump in and expect to spend thousands of dollars will come back and go on and on about how much of a substantial, night and day, earth shattering improvement - where the soundstage widended, the bass tightened, and whatever other stock standard audiophile poetry you'd like to blast out comes true.

Again, I fully agree.

Very likely there is no need to purchase new equipment, and it almost certainly will do nothing for you, but let you spend more money and come back and tell us about it.
post #15 of 22
Actually the capacitors start drying out over time, which causes them to no longer retain the charge as they are supposed to do, which causes other problems when they go.
post #16 of 22
Quote:
Originally Posted by mcnarus View Post

Well, the cheap D/A converters in your computer are probably no worse than the converters in any AVR. To be more precise, they may be measurably worse, but they won't be audibly worse. These chips are commodity products now. Even the cheapest are very, very good.

I was quite surprised to hear that my AVR sounds audibly better playing songs from its local flash drive than over optical connection from my computer's onboard sound. I think any person would hear it if s/he listened closely.
post #17 of 22
Quote:
Originally Posted by SaviorMachine View Post

I was quite surprised to hear that my AVR sounds audibly better playing songs from its local flash drive than over optical connection from my computer's onboard sound. I think any person would hear it if s/he listened closely.

It could be a problem with audio software stack in your computer. Unless you verified that what you get out of optical cable is exactly what was in the file, you can't come to any conclusion.
post #18 of 22
Quote:
Originally Posted by A9X-308 View Post


Yamaha generally made very solid amps (I own many) and I wouldn't recommend replacing it if it is not having issues.

As you probably know, but others may not, Yamaha gear and some others used glue, often referred to as DSBG (dreaded SonyBond glue) to help hold some of the larger capacitors in place. Over time, this glue tends to become corrosive and will damage the component leads it is in contact with.

Older gear should be inspected for DSBG and it should be cleaned up and damage corrected if the unit is going to be kept in good order.

Here's an example where you can see the corrosive effects on components and bus bar around where the two larger caps have already been removed.

post #19 of 22
Quote:
Originally Posted by ap1 View Post

It could be a problem with audio software stack in your computer. Unless you verified that what you get out of optical cable is exactly what was in the file, you can't come to any conclusion.

You know, you're not the first person to say this. I just don't know where to begin looking because I don't seem to have much control over the sound driver on my board. I think the problem is there because it's the same regardless of the application that's playing the sound (such as media players or games).
post #20 of 22
Quote:
Originally Posted by SaviorMachine View Post

I was quite surprised to hear that my AVR sounds audibly better playing songs from its local flash drive than over optical connection from my computer's onboard sound. I think any person would hear it if s/he listened closely.

Do tell us about how you matched levels, synchronized the music within a few milliseconds and established this with a blind test.

Otherwise, the perception of audibly better sound could be completely a matter of unconscious expectations, or simply a need to choose something.
post #21 of 22
Quote:
Originally Posted by arnyk View Post

Do tell us about how you matched levels, synchronized the music within a few milliseconds and established this with a blind test.

Otherwise, the perception of audibly better sound could be completely a matter of unconscious expectations, or simply a need to choose something.

No, I didn't do anything like that. I'm not pretending to be an expert about anything, just reporting my perception. As I mentioned, more than one person has advised that, because it's such a complex signal path between the bits and my listening position, I may be premature in blaming my onboard audio for the weaker bass and less defined midrange I hear when I listen to my PC's sound. I'm biased toward blaming my PC because it's 'common knowledge' (which is often wrong, of course) that onboard sound always sucks.

Do you use your PC as a source?
post #22 of 22
Thread Starter 
As a result of the info in this thread, I decided to get me the cheapest available AVR with preouts, and use the stereo as a power amp. It's a Yamaha RX-V771 (500 euro). Should arrive in a couple of days.

It has a second HDMI out, which is very useful for me as I have both a TV and a projector.

I bought it both because I want to have surround, and because the ease of cabling and use. I don't expect much of the AQ, but the amps will only be used for the surrounds.
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