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-   -   SS Vintager has dwindled volume (http://www.diyaudio.com/forums/instruments-amps/222546-ss-vintager-has-dwindled-volume.html)

TestTones 30th October 2012 08:50 PM

SS Vintager has dwindled volume
 
My amp is about 1/4 as loud as it was when we bought these. Happened to my nephews as well.

I've heard it's likely my power amp transistors but would like to confirm.
It's a 6 or 7 year old Behringer Vintager. It lost volume after about 3-4 years then just caved in all at once in a year's time.
Some of their gear is exceptional, some of it is garbage. This is an exceptional design but with garbage parts.
They are SMD.
WORST thing you can do is build a piece of instrument equipment with SMD.

I'm a shredder and symphonic instrumentalist but, I prefer the sound of chips or hybrids 10 fold over pure tube so it would be nice to salvage the unit. I suppose if all else fails, I can gut the power amp and replace it. I am just suspecting if it is my power amp stage transistors, some upgrades won't collapse nearly as fast as the stock did.

bear 30th October 2012 10:17 PM

Best bet is to buy a new one or else send it to a repair station that is familiar with the unit.

It's likely not "power amp transistors" since if one of them fails the amp ceases to work in most instances. That's if they short. If they open, the volume remains the same, but the current capability falls, so it can fry (overheat and have the transistor fail) the remaining output devices.

SMD devices are not a problem per se, but there can be various reliability issues depending on construction methods and parts quality.

_-_-bear

TestTones 31st October 2012 03:49 AM

Maybe my supply voltage has dropped?
I haven't had the time to pull it apart but, there's 3 of these amps in the family and all 3 dwindled in volume after a year or two. The preamp performance is untarnished. I swapped speakers, obtained a tremendous rise in volume but it still shouldn't be so mediocre with the stock Jensen MOD speaker. Maybe a gootched resistor in between preamp and power amp?
Maybe a decoupling cap slowly dropped value but isn't quite dead?
I had that happen on some P.A. amps for the decoupling cap it runs through when you bridge them.

I also haven't pulled it apart because of the way Behringer has the Chinese assemble stuff. They make it difficult and in some of their stuff, it's designed so you'll destroy it trying to get it apart. I will get to it but I have a lot of projects stacked up aside from my schoolwork which is priority.

My comment on SMD in preamps however is definitely accurate. The parts are so tiny it takes very little for them to distort and when they do, it's very unpleasant. When I hear the sound, I know before I even open up the piece of gear it's loaded with SMD. It even sounds the same in home and car audio gear. I've got a couple pedal and amp circuits of my own I am planning to put into production on the commercial market.
I don't care how much it would increase my profit margins, I would never use SMD!:eek:

bear 31st October 2012 04:52 AM

Well I am unfamiliar with the particular product.

If it has electronic or digital volume or similar stuff in it, that may have gone bad.

As far as SMD, might as well get used to it because through hole components are being phased out. Some parts that were commonly used are pretty much impossible to source already.

And yes, Behringer uses surface mount for the most part.

Who knows what has gone south in these amps... have you checked the web, if it has happened to more than one of the same units that you own, it may be a common failure and it may be written up?

_-_-bear

TestTones 31st October 2012 06:34 AM

In standard audio gear I see some SMD but in musical equipment it's still not popular unless you're talking digital. I do however see a lot of the subwoofer and full range amps in car audio are finally making the switch to SMD. The more digital we see, the more popular SMD will become.

But I still see primarily through hole construction in your respected pedals and amps. Behringer just isn't respected! lol
But maybe it's the brand of equipment you're used to?
I have easily a dozen amps and maybe a dozen pedals.
Good stuff is never SMD man. Boutique brands are not only making it into commercial retailer's inventory but we still use the hardcore stomp switches and die cast enclosures. You'll never see one of us use SMD and the day you do, you know the guy's designs are garbage.

Audio gear of basically any purpose is almost always through hole. I have some $12 car and marine Chinese amps, all through hole. The popular tripath class-D digitals are usually a mix of SMD and through hole. I guess that is somewhat common in consumer audio products as opposed to musician audio and instrument equipment.
Most SMD stuff I have seen over the years is in small gadgets like cell phones, children's toys, video game systems, TV's. SMD is known to be unreliable so even with it being cheaper, it also tends to be put in devices that aren't known for a long life span. Things that really can't be upgraded or repaired like laptops which are throw away computers.

I still think something in the amp is just low quality and has cost us volume over time. My nephew couldn't even play with his drummer where as before, the amp was loud enough to give you ringing ears the next morning. If it becomes too much hassle trouble shooting, I'll just swap speakers for the easiest fix.
I was mostly asking because for some stuff, there's just a commonly known cause of unusual symptoms.

Enzo 31st October 2012 06:40 AM

Hi TestTones, I must say you have some unusual idea on this.

As was said, not likely your output transistors, and no, it is not likely your power supply voltage is fading away, though I suppose anything is possible.

The Vintager is model AC108, for anyone trying to look up the drawings. In fact this amp doesnl;t even have output transiswtors, at least not discrete ones. This amp uses the common TDA2030 power amp IC.

As a Behringer service center here, I have to point out the Behringer stuff is assembled like any other brand. The CHinese-ness of it is not a factor. Sometimes ANY brand may have the chassis stick in the cab because the tolex stuck to the chassis, or because someone didn't realize there were a couple more screws. But this and all the others have the chassis come out by removing some screws and maybe the handle. Then the circuit board is held in like anay other - the control and jack nuts along the panel and some chassis mounting screws.

Surface mount may be more difficult for YOU to work on, but in a commercial shop it is just everyday service work. SMD stuff is actually a LOT more reliable than through hole stuff. Your cell phone is made of SMD, as is the computer you are communicating with. Most modern electronic equipment is made with it. A 10k resistor is a 10k resistor, the size of it on the board really has no effect on it distorting.

You want to know what THE single most common cause of dropping volume is in any amp? Jacks. In your case, this is a very basic little amp, and that headphones jack is just screaming "check me check me." IN fact, while playing through the amp at the faded volume, just poke some plug in and out of the phones jack real quick and see if it wakes up the amp. FX loop jacks are the most common, but your amp does not have an FX loop.

Your amp also has a tube in it, easily changed, though it is running on very low voltage, of all the electronic components in there, the tube will be the least reliable.

bear 31st October 2012 02:18 PM

Not "headphone jack" - input jack or output connector.

They might or might not all fail the same way. Sounds like they have.

He also says that there are no discrete transistors in the ouput, it's a "brick".

The guy said he was a Behringer service center, maybe he knows something?

I'll agree with you TestTones that SMD/T whatever you call them devices can and do fail due to vibration and so have solder cracks on the joints. I'm not happy about that, I have seen more than I would like of that. I strongly doubt that SMD gear will have the 60+ year life cycle that old school point to point wiring can have.

Enzo, when you say
Quote:

A 10k resistor is a 10k resistor, the size of it on the board really has no effect on it distorting.
, you're partially wrong and partially right. For most situations it makes no difference, but the facts are that there are different distortion spectra produced by different resistors... and in general higher wattage for a given application will yield less distortion. Of course that distortion is very low in level and matters pretty much when we're talking about minimizing distortions in an already low distortion circuit (like an amp or preamp or opamp, etc...). FYI.

Enzo 31st October 2012 11:10 PM

TestTones, seriously, do you want to trade sarcasms, or do you want to solve your problem?

Thank you for updating the model number, it makes it much eassier to look up the circuit. Yes, the GM110 is even less involved than the AC108, with no tube.

"I don't know what laws of physics you live under but a drop in voltage is going to drop volume. Less voltage = less current = less wattage.
How the hell is that unusual?"

It is unusual in that that is not how amplifiers wind up with diminished output. yes, if we dialed the power amp down to 5v rails, it would be a lot less loud. But in real life amp repair, that doesn't happen. One could also suggest that the speaker might have gone way up in impedance and so derive a lot less power. In terms of physics that would be the result, but in real life speakers do not do that.

"I guess they've never heard of Ohm's Law where you're from!
Haha thanks for like many regs on this forum, assuming I'm ignorant. I really don't understand why so many of you insist on being condescending while swearing it's me not you. "

Is that necessary? I don't assume you are ignorant, I think you have made some faulty assumptions and based your analysis on them. And I don't believe I have been hostile.

"However the PCB's in some Behringer gear are set in so you'll damn near destroy the equipment getting it apart.
Ever dismantled a Behringer V-Amp Pro?"

Yes I have, in fact I have one on the shelf nearby. My shop is authorized by most of the major brands, I work on them all, and the Behringer stuff is assembled like any other brand. I have never had to damage a circuit board in one of their products just to get it out of the chassis. There is no secret to it. Behringer will no more give you instructions on servicing their products than General Motors will tell you how to do a valve job or change a water pump.

"THREE amps do the exact same thing in the exact same pattern and it be the result of a headphone jack?
That makes zero sense considering the switch inside the jack is either opened or closed. I often suspect most of you aren't so much helpful as you are looking to belittle less educated people but I'm no longer one of them."

As a matter of fact it is not at all unusual to find two or three amps in a days work all with failing FX loop jacks or other jacks with cutouts (like headphones jacks).

Yes, the switch inside is either open or closed, and when closed, it completes the circuit for the speaker. What happens when that switch contact becomes dirty or oxidized? It becomes resistive, and that resistance then is in series with your speaker, reducing its power. I am not making it up, it is a COMMON problem in amps with headphones jacks.

"Behringer gear, plenty of it is assembled so it self destructs if you don't have access to the service manual showing you the bizarre, unconventional methods they mounted it with."

Behringer provides service centers with schematics, period. NO service manual, especially not for small guitar amps. On some more complexs gear like DSP signal processors there may be a few service tips, like "C108 ries out in the SMPS". Disassembly is not covered, but there is nothing unconventional about it.

"They also won't issue the schematics or service manuals. Partly because they have authorized service centers but also because a lot of their products are known rip offs of stuff"

Not all companies issue schematics outside of their service networks. Try getting one from Line6 or Nady. Behringer steals circuits, yes, but that has nothing to do with it, other than they lost a big lawsuit with Mackie a few years back, and got real tight fisted after that. Loud Technologies (Mackie, Crate, Ampeg) will share schematics but makes you agree not to post them. At the far end of the scale, Peavey will send out any of their schematics to anyone who asks for them.

ANd as to your GM110 amps, the output IC is a 4701 rather than a TDA2040, so still no transistors. But it still has a phones cutout. You may think I am nuts, but if one measures the cutout contact resistance and it is more than half an ohm, it needs to be burnished or replaced or otherwise cleaned. And this model DOES have an FX loop, insert jacks. The simple test is to plug a spare cord from send to return - an external bypass sorta. If that wakes the amp up, then the return jack needs service to its cutout contact. ANother test is this: PLug the guitar into the FX return or INSERT return. If the output is still diminished, then the problem is in the power amp or speaker. If that is strong and clear, those are OK. And finally, you have three selector switches that I see, Amp, Mode, and Speaker. ANy one of these switches can cause a loss of sound if they get dirty or contacts fail.

Enzo 1st November 2012 12:06 AM

I apologize for interfering with your efforts. I hope you find solutions to your problems.

unclejed613 1st November 2012 12:49 PM

if the output chips are linear, then another possibility is that the DC correction cap in the output chip's feedback network is dried out or open. i see it in a lot of different amps, and exactly fits the symptoms, slow loss of volume until now you get next to nothing.


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