Hi everyone.
I set-up my first hifi yesterday, a Pioneer 400 with a pair of Mission 751s.
I have two issues:
1) The volume doesn't scale smoothly, it goes from extremely quiet to very loud before even making it to the first volume position, meaning that I have to have my source turned down very low and I'm at constant risk of blowing out my speakers.
2) The lefty speaker is way, way quieter than the left below volume position 3, then it evens out. I can compensate at lower volume positions using the balance control.
Does anyone have any idea as to where the issue might be? I'm really hoping it's not a broken pot.
If you recommend cleaning the pot, what should I use? I have access to IPA alcohol spray.
Thanks for any help!
I set-up my first hifi yesterday, a Pioneer 400 with a pair of Mission 751s.
I have two issues:
1) The volume doesn't scale smoothly, it goes from extremely quiet to very loud before even making it to the first volume position, meaning that I have to have my source turned down very low and I'm at constant risk of blowing out my speakers.
2) The lefty speaker is way, way quieter than the left below volume position 3, then it evens out. I can compensate at lower volume positions using the balance control.
Does anyone have any idea as to where the issue might be? I'm really hoping it's not a broken pot.
If you recommend cleaning the pot, what should I use? I have access to IPA alcohol spray.
Thanks for any help!
Welcome to the forums 🙂
Question... you say you have to have the source turned down very low. What sources are you using ?
Your problem sounds like you are simply feeding to high a level into the amp and as such you are using the control at the lower end of its range.
Also, its quite common for "cheap" pots to have quite a channel imbalance as the two resistive tracks don't track equally. This is particularly apparent at low levels. That's easily fixed by either an external attenuator such as,
Attenuators
You can make your own for buttons 😀
You could also look at adding the attenuators inside the amp if needed.
Question... you say you have to have the source turned down very low. What sources are you using ?
Your problem sounds like you are simply feeding to high a level into the amp and as such you are using the control at the lower end of its range.
Also, its quite common for "cheap" pots to have quite a channel imbalance as the two resistive tracks don't track equally. This is particularly apparent at low levels. That's easily fixed by either an external attenuator such as,
Attenuators
You can make your own for buttons 😀
You could also look at adding the attenuators inside the amp if needed.
Wow thanks, interesting reading.
I've tried my Nexus 5 phone, Nexus 7 tablet and PC, all of which produce the problem, only the PC adds a huge amount of noise as an added bonus which I was hoping an external sound card might help.
Do you think these devices (being of a similar ilk) are all producing too much gain?
I've tried my Nexus 5 phone, Nexus 7 tablet and PC, all of which produce the problem, only the PC adds a huge amount of noise as an added bonus which I was hoping an external sound card might help.
Do you think these devices (being of a similar ilk) are all producing too much gain?
At the very least, I would suspect an issue with disconnected ground at the volume pot. If there even is an abrupt jump in volume, I'd say bad pot. Any signs of transport damage?
No, it was exceedingly well packed in many layers of large bubblewrap and then cardboard around the amp. The box isn't new so I can't judge by its appearance.
They could be. Also, these types of device often use Class D (switching amplifier) output stages and can need a load resistance to emulate the effect of headphones which in some cases form part of the Class D filter stages.
Can you try the amp with a "normal" hifi separates component such as a CD player or cassette deck, tuner etc and see what its like.
All I could put my hands on is a DVD player with RCA outputs which reproduced the same problem.
I'm having a couple of adjustable attenuators delivered tomorrow so will report back after giving them a go. I think they will help/be useful even if they don't solve the problem.
Thanks to you both for your input so far. 🙂
No, but the amp obviously does. Normally you should get a nice comfy listening volume at about the 9 o'clock pot setting with digital sources running at full blast. Mission 751s aren't exactly huge and highly efficient speakers, and I assume you don't have them glued to your head. but rather at some semi-normal listening distance.
You didn't use the Phono input by any chance? 'cuz that one has a lot of extra gain... We've all been young and foolish at some point, right?
Firstly my Electro skills knowledge is scant at best 🙂
However I cured... eventually, a Similar balance and odd volume issue by replacing the Volume pot .
Despite suggestion that it wasn't likely the problem source.
Fitted a Cheap Chinee Clone Aps blue pot (12$ delivered 🙄
Instant (once fitted) fix.
However I cured... eventually, a Similar balance and odd volume issue by replacing the Volume pot .
Despite suggestion that it wasn't likely the problem source.
Fitted a Cheap Chinee Clone Aps blue pot (12$ delivered 🙄
Instant (once fitted) fix.
I'm back at last!
A huge thanks to Mooly for the attenuator advice! I bought variable ones and with them set to 20db, they don't cure the problem but make the amp useable.
Now I can run my sources at 100% and use the volume. Unfortuently the balance is still out below position 4 but at least I can use the amp just fine until I have some holiday when I can open the amp up and clean the pot/take resistor reading etc.
The ground-loop/noise issue from my PC I fixed with a toslink into a toslink to RCA convertor. However, I have to keep my PC at low volume as it has the same gain problem. Might get some more atenuators.
If it's the pot that needs replacing then I'm out of luck as from what I've read it's not practical to replace the volume pot unless you have one out of another A400 due to its unique design.
Could faulty components in the input circuit be the source of this rediculous gain?
Thanks to everyone who's contributed to the thread.
A huge thanks to Mooly for the attenuator advice! I bought variable ones and with them set to 20db, they don't cure the problem but make the amp useable.
Now I can run my sources at 100% and use the volume. Unfortuently the balance is still out below position 4 but at least I can use the amp just fine until I have some holiday when I can open the amp up and clean the pot/take resistor reading etc.
The ground-loop/noise issue from my PC I fixed with a toslink into a toslink to RCA convertor. However, I have to keep my PC at low volume as it has the same gain problem. Might get some more atenuators.
If it's the pot that needs replacing then I'm out of luck as from what I've read it's not practical to replace the volume pot unless you have one out of another A400 due to its unique design.
Could faulty components in the input circuit be the source of this rediculous gain?
Thanks to everyone who's contributed to the thread.
If it is still very loud with the attenuators, i.e. you still don't need turn it up all that much, then maybe you need even higher attenuation for your sources. 20 db means that 1 volt in gives 0.1 volt out. .
I'm sure you won't have a problem with any of the components as such with the obvious exception of the pot and inherent poor tracking between the two gangs.
I'm sure you won't have a problem with any of the components as such with the obvious exception of the pot and inherent poor tracking between the two gangs.
As sgrossklass already suggested - are you sure you are using the right inputs? It looks very much like it's Phono to me as well...
- Status
- Not open for further replies.