I recently put back together a denon amp after it blew a fuse. It turns out it needed transistor insulators. It looks like the tuner went out as well. I also had to replace the subwoofer cable since it hummed when nothing was connected to it. I used a yellow rca cable since that's what I had on me. Anyway, I'm having a problem where the bass just isn't there anymore. The sub volume sounds way too low on the default setting of 0.0 db. It wasn't like this before. I went on audiocheck.net and there seems to be frequency drop in the 120hz range even with the subwoofer but when it goes to a lower frequency, the bass is full. Can someone help me out?
With no details of your subwoofer, you're asking a very broad question that reads like; "how do you fix the crossover of bass from speaker to subwoofer". I'm sure you know that most subs have adjustable upper frequency roll-off controls and integrated power amplifiers also have bass roll-off controls. Together, these can be used to control the crossover between the two types of speaker. However, if the phase of the subwoofer signal is reversed for some reason, the bass from both speakers will cancel at the crossover frequencyand appear as a dip or "suckout" at the bass crossover frequency of the two speaker systems.
Sometimes there is a phase switch on the sub. to invert its input signal (correcting the phase), sometimes not but if your cable wiring is wrong, you may have caused this problem with your substituted "RCA cable". You should refit the original cable, checking the hum stops when it is fitted correctly between the amplifier and sub. and compare results. Even dead shorted, the cable doesn't cause hum of itself, only if the connection is broken which you can test with any cheap mutimeter or even a battery and lamp.
BTW, powered subs, like any amplifier, do hum when nothing but the interconnecting cable is connected to them. The unterminated lead is an aerial for any electromagnetic noise in the environment so you hear predominantly mains power noise. If yours doesn't, I'd suspect your cable is wired wrongly.
Sometimes there is a phase switch on the sub. to invert its input signal (correcting the phase), sometimes not but if your cable wiring is wrong, you may have caused this problem with your substituted "RCA cable". You should refit the original cable, checking the hum stops when it is fitted correctly between the amplifier and sub. and compare results. Even dead shorted, the cable doesn't cause hum of itself, only if the connection is broken which you can test with any cheap mutimeter or even a battery and lamp.
BTW, powered subs, like any amplifier, do hum when nothing but the interconnecting cable is connected to them. The unterminated lead is an aerial for any electromagnetic noise in the environment so you hear predominantly mains power noise. If yours doesn't, I'd suspect your cable is wired wrongly.
Thanks for the response. I should've stated this happens when the speakers are set to large and the subwoofer output is turned off, as well. The subwoofer is kinda old, it's from 2002 but it was new old stock when I got it several years ago. As for the cable hum, it's strange that you say it hums when not connected to anything. The RCA cable I'm using is fairly thick, could that be the shielding blocking the emi interference. The cable used prior to this was very thin.
Despite all of this, I'm convinced it's the amplifier at this point though. I have to turn it up higher than before to get the same output, -30 db used to be plenty loud but now it isn't. A few transistors may have been damaged when it blew it's fuse. I might just look into getting a class d amplifier and calling it a day. No way I'm importing these heavy receivers, high shipping cost.
Despite all of this, I'm convinced it's the amplifier at this point though. I have to turn it up higher than before to get the same output, -30 db used to be plenty loud but now it isn't. A few transistors may have been damaged when it blew it's fuse. I might just look into getting a class d amplifier and calling it a day. No way I'm importing these heavy receivers, high shipping cost.
I'm unsure what you refer to when you say it needed insulators but if it's what I think you mean and you reassembled the power amplifier without insulators beween heatsink and power transistors, you sure could have done some damage - probably more than what caused the fuse to blow initially.
Wouldn't it be cheaper and better to get your amplifier repaired professionally? You may resent paying for something more than once but DIY repairs are only good if you really know what you're doing and that part doesn't come easy.
Wouldn't it be cheaper and better to get your amplifier repaired professionally? You may resent paying for something more than once but DIY repairs are only good if you really know what you're doing and that part doesn't come easy.
ANY input, when not "loaded" with a source, will naturally show signs of hum, because it's "wide open".
It doesn't matter if there's a cable connected to the input jack, or just nothing - it NEEDS a load to ground as any source would provide.
And any cable with a less (under a fraction of an ohm) than solid ground/shield will also allow hum into the system.
This is simply the nature of the beast in electronics.
Not all subs power up when they are switched on. Mine at least, won't until a valid signal is fed to them but with a bit of coaxing from a bass signal, they start amplifying until auto power down if there is no input for some time. A cable helps turn them on when there is no signal as it increases sensitivity to 50Hz hum in my case.
Auto power on/off is a safety feature on subs for people like me who forget to turn all their audio system off when they can't see any light or hear anything and have a fire risk as a result. Otherwise, a 12V trigger control voltage is now used to turn everything off when the amplifier is in a compatible 12V triggered audio system. See the blog article. Blog - Subwoofer Controls: What Do All Those Knobs Do, Anyway? | Axiom Audio
I realise this is off-topic for the OP's underlying problem but commercial subwoofers aren't all the same and some features need to clarified, though recent models tend to be more universal and standardised. Speaking of the OP, where are you located that you are unsure of whether there are any repairers within reach, Mark 461?
Auto power on/off is a safety feature on subs for people like me who forget to turn all their audio system off when they can't see any light or hear anything and have a fire risk as a result. Otherwise, a 12V trigger control voltage is now used to turn everything off when the amplifier is in a compatible 12V triggered audio system. See the blog article. Blog - Subwoofer Controls: What Do All Those Knobs Do, Anyway? | Axiom Audio
I realise this is off-topic for the OP's underlying problem but commercial subwoofers aren't all the same and some features need to clarified, though recent models tend to be more universal and standardised. Speaking of the OP, where are you located that you are unsure of whether there are any repairers within reach, Mark 461?
All that is good information of course.
In general, the sub power supply is ALWAYS ON, it HAS to be, in order to "sense" if an incoming signal happens.
The relay connecting the subwoofer speaker opens during "standby", thus making it silent.
However, the unit is still drawing power.
One sub that I have (BIC Venturi) actually draws a full 50 watts in standby!
It's big power transformer is always connected to the line, even if the switch (off-on-auto) is set to OFF.
I said to heck with THAT arrangement! - and installed a power switch to kill its drain when not in use.
You hook an AC wattmeter to a sub's power cord, and you see for yourself if it's still draining power when in standby - you might be surprised.
I see. Well that's plain enough. Now I also understand why you do need to repair things yourself. That's the true DIY attitude but if you are starting from scratch without some training or mentoring of some sort, it's going to take a long time and burn up a lot of gear in the of course of becoming proficient. Perhaps you could check out some on-line videos of repairs by guys who know what they're doing with audio amplifiers and the like. You-tube isn't often full of high quality info but guys like John Audiotech do discuss some features of parts and fitting them that I find useful.
Yup, I appreciate the advice and I have watched videos on receiver repair here and there on youtube. I'll need specialized equipment, possibly an oscilloscope and something for those mini connectors between each pair of transistors, to calibrate it. Oh, well not worth it, potentially fun project though.
I can understand the "DIY" aspect of things, I myself have to straighten some things out to save some money, and insure I'm not getting "ripped off" by contractors AKA plumbing, house wiring, etc.
Seems like a lot of contractors (certainly not all) these days want the the jobs, cash, but perform sloppy sub-standard work.
The mentalty towards "pride" and "craftsmanship" isn't what it used to be.
But electronics repairing - successful repairing, not "tinkering around" - requires proper schooling, including learning the fundamentals like the Ohms Law stuff, the Theory part, countless weeks of Certified Instructional Training, understanding the operation of testing equipment, etc.
I went through it all, on and off training for decades, with some specialized training as well.
And it's not easy, and not supposed to be, although I've had some help by doing extensive reading from textbooks as a kid in my teens, so I had some "background experience".
Heck, I built tube amps when I was 15, with help from an elderly neighbor, and my grandfather - both great mentors - RIP y'all.
What amuses me are those that act like and believe that they don't need such tedious training - in other words, sidestepping what I had to go through - and insisting that things like youtube, online blogs ran by self-proclaimed faux "experts" of questionable experience, and picking up a book at Lowes or Home Depot, is the "fix all" solutions.
Nah, sorry, it don't work that way.
As Ian Finch mentioned, without the proper education, you'll wind up destroying a lot of things along the way.
It's a shame, guys like me are a dying breed anymore.
Years ago, you'd take your broken stuff to a shop, pay the man, and be done with it.
Seems like a lot of contractors (certainly not all) these days want the the jobs, cash, but perform sloppy sub-standard work.
The mentalty towards "pride" and "craftsmanship" isn't what it used to be.
But electronics repairing - successful repairing, not "tinkering around" - requires proper schooling, including learning the fundamentals like the Ohms Law stuff, the Theory part, countless weeks of Certified Instructional Training, understanding the operation of testing equipment, etc.
I went through it all, on and off training for decades, with some specialized training as well.
And it's not easy, and not supposed to be, although I've had some help by doing extensive reading from textbooks as a kid in my teens, so I had some "background experience".
Heck, I built tube amps when I was 15, with help from an elderly neighbor, and my grandfather - both great mentors - RIP y'all.
What amuses me are those that act like and believe that they don't need such tedious training - in other words, sidestepping what I had to go through - and insisting that things like youtube, online blogs ran by self-proclaimed faux "experts" of questionable experience, and picking up a book at Lowes or Home Depot, is the "fix all" solutions.
Nah, sorry, it don't work that way.
As Ian Finch mentioned, without the proper education, you'll wind up destroying a lot of things along the way.
It's a shame, guys like me are a dying breed anymore.
Years ago, you'd take your broken stuff to a shop, pay the man, and be done with it.
Repairs are great fun if you occasionally have some success. However, you don't really need an oscilloscope to do general repairs which often show as obvious problems just in the voltages you learn to expect at key points in the circuit. By comparing good with bad channels in a multi-channel amplifier for example, you soon get the picture of what's critical and what follows if it isn't correct.
At a beginner level, a 'scope just helps to illustrate circuit behaviours that we don't fully understand. It really comes into its own when we consider the design itself and how well it works in practice. Now that the simulation of circuits is a dependable design tool, the scope is a little less essential there.
A lot of repair work is done by just a few observations, voltage checks against service manual schematics, specs and past experience with similar products. Then there are known suspect components such as old electrolytic capacitors, switch and relay contacts that corrode, hidden fuses and safety circuits that fail and confuse you too. These are problems that we may need help with. Experience is the key and that means a mentor to get you started, like maybe an amateur radio enthusiast? I'd expect there to be a few at least in your location so perhaps you could ask around.
I've done amateur repairs of domestic audio gear since the days of tubes but I wasn't able to afford or justify a decent quality 'scope until approaching retirement. Funny, that
At a beginner level, a 'scope just helps to illustrate circuit behaviours that we don't fully understand. It really comes into its own when we consider the design itself and how well it works in practice. Now that the simulation of circuits is a dependable design tool, the scope is a little less essential there.
A lot of repair work is done by just a few observations, voltage checks against service manual schematics, specs and past experience with similar products. Then there are known suspect components such as old electrolytic capacitors, switch and relay contacts that corrode, hidden fuses and safety circuits that fail and confuse you too. These are problems that we may need help with. Experience is the key and that means a mentor to get you started, like maybe an amateur radio enthusiast? I'd expect there to be a few at least in your location so perhaps you could ask around.
I've done amateur repairs of domestic audio gear since the days of tubes but I wasn't able to afford or justify a decent quality 'scope until approaching retirement. Funny, that
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