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bass tone control
http://www.diyaudioprojects.com/Forum/viewtopic.php?f=10&t=5560
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Author:  boonin [ 24 Apr 2016, 14:18 ]
Post subject:  bass tone control

is their a bass tone control for the mx 50 amp sold on ebay ?

Author:  kulamario [ 09 Aug 2018, 19:11 ]
Post subject:  Re: bass tone control

you can use something on 2 x NE5532
available on ebay

Author:  Yungman [ 11 Aug 2018, 16:26 ]
Post subject:  Re: bass tone control

Looking at the pcb, I don't think so, there's no provision for a potentiometer. Power amp usually don't have any tone control. You do tone control in preamp.

Author:  kulamario [ 11 Aug 2018, 19:25 ]
Post subject:  Re: bass tone control

I do not know what you want to get
would you say why you need this preamplifier , would be beautiful
it looks like you want to use it for some subwoofer or something
if you want to a subwoofer then you need a preamplifier with a low pass filter
to cut unwanted frequencies

Author:  Yungman [ 12 Aug 2018, 00:20 ]
Post subject:  Re: bass tone control

I personally don't want preamp or any tone control. I used to have preamp and power amp separate, but I am at the process of putting the input selector into the power amps and only have a passive motorized volume pot from input to the power amp.

Some of the Chinese amps have the right idea, they put a volume pot in the power amp so people don't even need to use a preamp and hook the CD or other source directly to the power amp. Mine is the same idea except I also have input from video sources and select and output to the tv at the same time, it's basically a AV amp. with two channels only.

If you think you don't have enough bass, there are other issues that can affect the bottom, I had this problem and turn out to be grounding issue in the amp. I used to feel I don't have enough bottom, I even slightly enhance the frequencies below 300Hz or so about 10%. But since I fix the grounding, I don't need that anymore.

If you build your own amp, the grounding can be tricky. It is more critical than normal electronics. I don't want to get into too detail as I am still doing R&D on this. Don't want to give out wrong information. I can only tell you how critical it is.

I can assure you if everything is working correctly, you should have plenty of bass or bottom with straight into power amp from the CD or other source. You might want to look at other things. AND if there is a problem, adding a sub or crank up the bass is not going to fix it. I tried. Now I can turn off the sub and have plenty of bottom ( just not the floor shaking boom in the movie).

Author:  Yungman [ 12 Aug 2018, 12:41 ]
Post subject:  Re: bass tone control

Here is an article by Hifisonic that might be of interest if you build the amp:
http://hifisonix.com/wordpress/wp-content/uploads/2018/07/How-to-wire-up-an-amplifier_3.pdf

This article only talk about hum, BUT how you do it affect the sound. I am actually surprised by this. Getting rid of the hum is easy, I did it and never have hum. But I only discovered how the ground can affect the sound only like a month or two ago. It mainly affect the bottom. ( I don't want to call it bass as you can have loud bass but no bottom for the lack of words. ). I tried with very good sub and it did not help.

You don't have to read the full article if you don't want to, most are theory about EMC design. Start reading from p53 to p58 on how he did it. He is talking about eliminating hum, but this change the sound too. Attached is the notes that highlight the part the change the bass for me.

Attachment:
Hifisonic grounding.JPG


It is very important the speaker return to that point.

The Hum break resistor needs to be lower to about 1ohm. 15ohm will make the bass weak ( lack of bottom). I don't want to bore you with theory.

Note that this is very basic, I am working on much more involve and advanced than this. But it's a good place to start.

Author:  kulamario [ 12 Aug 2018, 18:18 ]
Post subject:  Re: bass tone control

I am sorry but I replied to boonin
he ask "is their a bass tone control for the mx 50 amp sold on ebay ?"
so i answer yes
I know it's best to no have a preamplifier just pot

Author:  Yungman [ 12 Aug 2018, 20:30 ]
Post subject:  Re: bass tone control

kulamario wrote:
I am sorry but I replied to boonin
he ask "is their a bass tone control for the mx 50 amp sold on ebay ?"
so i answer yes
I know it's best to no have a preamplifier just pot



Yes, I reply to OP also, nothing to do with your posts.

I am spending a lot of time in this very thing right now. All started out with weak base ( no bottom ).

Author:  kulamario [ 13 Aug 2018, 07:06 ]
Post subject:  Re: bass tone control

I know this MX50 amplifier because I have this set myself
and he really does not have much bass
In this amplifier the top is more exposed and the bottom is not too much
Generally, this amplifier is not the best design

Author:  Yungman [ 13 Aug 2018, 11:56 ]
Post subject:  Re: bass tone control

kulamario wrote:
I know this MX50 amplifier because I have this set myself
and he really does not have much bass
In this amplifier the top is more exposed and the bottom is not too much
Generally, this amplifier is not the best design


I don't have the schematic, but it's hard to believe there is anything in power amp circuit that limit the low frequency. They usually are flat frequency response within the audio frequency.

I have been designing power amps for a few years, I just discover how critical the grounding is. The same amp I designed got so much better bottom by improving the grounding and lower the isolation resistor as described in the article. If you build your amp, you might want to check that also. Take a look starting at page 7 of this article:

http://hifisonix.com/wordpress/wp-content/uploads/2018/07/Amplifier-PCB-Design-Guidlines-for-Minimizing-Hum-1-1.pdf

People usually think grounding is just to eliminate hum, but there's a lot more to it. The article talk about ground loop emitting EMI that couple to the other part of the circuit, I feel it's more than that. Ground current cause slight potential change on the ground even if you have ground plane on the pcb or using big wires. I have been working on this very thing for the last two months, the improvement of the bottom is staggering without changing any other part of the circuit EXCEPT the HRB ( hum break resistor) from 22ohm to 1ohm. This resistor is very effective to reduce hum, BUT it will cause the bottom to be very weak.

I don't want to get into detail as I am still experimenting and looking at the theory, but this is where I am at.

Yes, MX50 is a cheap circuit, don't expect too much, but from my experience, there should be room for improvement without spending a lot of money.

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