Hi all,
I am using cheap car amp and i really want to learn what things can be done to improve its sound.
I know it might be a wise decision since the amp itself is not really a genesis, audison or other expensive brand. The keywords here are "learning" and "hobby"
So here's the guts:
- Electrolite cap before toroid: 2 * 1000 mF
- Electrolite cap after toroid: 2 * 4700 mF
- Rectifier bridge: 2 * YG 225D2
- Amp transistor D718 & B688 (made by KIA?)
- Coupling cap: couldn't find any ???
Now... I need a guidance on what can be replaced with higher quality without too much modification to the circuits.
I am thinking to replace the electrolites with higher value and higher quality such as panasonics or elna to improve bass.
I don't have a deep knowldege about electronics but I think the transistor is not mosfet type. Is it possible to upgrade it to better type?
Anymore suggestions?
I am using cheap car amp and i really want to learn what things can be done to improve its sound.
I know it might be a wise decision since the amp itself is not really a genesis, audison or other expensive brand. The keywords here are "learning" and "hobby"
So here's the guts:
- Electrolite cap before toroid: 2 * 1000 mF
- Electrolite cap after toroid: 2 * 4700 mF
- Rectifier bridge: 2 * YG 225D2
- Amp transistor D718 & B688 (made by KIA?)
- Coupling cap: couldn't find any ???
Now... I need a guidance on what can be replaced with higher quality without too much modification to the circuits.
I am thinking to replace the electrolites with higher value and higher quality such as panasonics or elna to improve bass.
I don't have a deep knowldege about electronics but I think the transistor is not mosfet type. Is it possible to upgrade it to better type?
Anymore suggestions?
I'm about to replace the input op-amps and decoupling caps in my car amp
it's noise is around -105 dB or so - far too noisy for SQ
I'm hoping to get it below 120dB - to at least come close to the 24/96 feed to it
I'm pretty sure it's the input chips because I can 'turn down' the noise by reducing the input sensitivity.
The caps are to spice up the sound a bit - the depth is a little shallow, and lack well-defined bass
it's noise is around -105 dB or so - far too noisy for SQ
I'm hoping to get it below 120dB - to at least come close to the 24/96 feed to it
I'm pretty sure it's the input chips because I can 'turn down' the noise by reducing the input sensitivity.
The caps are to spice up the sound a bit - the depth is a little shallow, and lack well-defined bass
Simple amp mods?
Hi
You should first get or trace a schematic of the amp before modding so you really know what each components function is.
If you haven't done so already, you should read up on the "objective" causes of NFB amp distortion first to see the complexities involved in what you are trying to do. Simple parts swapping of output devices is usually not possible without redesigning the amp, increasing bias, affecting thermal stability, etc.
Here's a DIY source for the power transistors. Sanken LAPT's are considered the best but you will need to redesign to use them.
http://www.ampslab.com/components_power.htm
The same applies to the SMPS. You can easily cause things to "blow up" in a hurry there.
I am not saying mods can't be done but you really need to know what you are doing, almost to the point of becoming an amp designer yourself! So if you want a challenge here you go:
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm#2
I don't agree with everything he says but he provides a good foundation to build on.
A simple mod that D.Self suggests on that page is to increase the size and voltage of the "feedback network blocking cap". He also uses a diode across it but I haven't experimented with that yet.
If your amp uses a cap in the feedback network (most do) it may be too small and will cause significant distortion in the bass. This will be clearly audible "subjectively" Don't skimp here go BG NP or OS-CON since it's only one cap/channel.
I cant recommend messing around with the power supply output caps becuase they are spec'ed along with the toroid to provide the best transient response. If you want to improve the supply of "instantaneous" current to the output stage you could add low esr caps close to the output transistors so as to keep them from greatly affecting the power supply caps. But to do this as others have mentioned may require a 'scope to make sure the power supply or amp doesn't do "funny" things when heavily loaded.
Another thing you may want to try is to make a "composite" cap bank that will provide better line regulation for your amp. This cap must be wired in between the fusing and the power supply.
By "composite" cap I mean a bunch of small identical caps wired in parallel to provide much better discharge current and speed than a larger stiffening cap. To be effective many caps 10 - 40 need to be used depending on the needs of the amp. Because of space constraints amp manufacturers don't leave enough room in the amp for you to do this mod "inside" the amp so you will be forced to make a box that sits under your amp that contains the caps.
If you are still interested I can elaborate further...
Hi
You should first get or trace a schematic of the amp before modding so you really know what each components function is.
If you haven't done so already, you should read up on the "objective" causes of NFB amp distortion first to see the complexities involved in what you are trying to do. Simple parts swapping of output devices is usually not possible without redesigning the amp, increasing bias, affecting thermal stability, etc.
Here's a DIY source for the power transistors. Sanken LAPT's are considered the best but you will need to redesign to use them.
http://www.ampslab.com/components_power.htm
The same applies to the SMPS. You can easily cause things to "blow up" in a hurry there.
I am not saying mods can't be done but you really need to know what you are doing, almost to the point of becoming an amp designer yourself! So if you want a challenge here you go:
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm#2
I don't agree with everything he says but he provides a good foundation to build on.
A simple mod that D.Self suggests on that page is to increase the size and voltage of the "feedback network blocking cap". He also uses a diode across it but I haven't experimented with that yet.
If your amp uses a cap in the feedback network (most do) it may be too small and will cause significant distortion in the bass. This will be clearly audible "subjectively" Don't skimp here go BG NP or OS-CON since it's only one cap/channel.
I cant recommend messing around with the power supply output caps becuase they are spec'ed along with the toroid to provide the best transient response. If you want to improve the supply of "instantaneous" current to the output stage you could add low esr caps close to the output transistors so as to keep them from greatly affecting the power supply caps. But to do this as others have mentioned may require a 'scope to make sure the power supply or amp doesn't do "funny" things when heavily loaded.
Another thing you may want to try is to make a "composite" cap bank that will provide better line regulation for your amp. This cap must be wired in between the fusing and the power supply.
By "composite" cap I mean a bunch of small identical caps wired in parallel to provide much better discharge current and speed than a larger stiffening cap. To be effective many caps 10 - 40 need to be used depending on the needs of the amp. Because of space constraints amp manufacturers don't leave enough room in the amp for you to do this mod "inside" the amp so you will be forced to make a box that sits under your amp that contains the caps.
If you are still interested I can elaborate further...
I think he meant bridge each one on its own.
The answer is 'it depends' and without even giving us any model numbers how do you expect us to know? The best way is to read the manual, or if you don't have it have a look on where the speakers connect and see if there is any markings for where to connect a bridged load.
The answer is 'it depends' and without even giving us any model numbers how do you expect us to know?
The best way is to read the manual, or if you don't have it have a look on where the speakers connect and see if there is any markings for where to connect a bridged load.
sq_guy said:Hi all,
I am using cheap car amp and i really want to learn what things can be done to improve its sound.
I know it might be a wise decision since the amp itself is not really a genesis, audison or other expensive brand. The keywords here are "learning" and "hobby"
So here's the guts:
- Electrolite cap before toroid: 2 * 1000 mF
- Electrolite cap after toroid: 2 * 4700 mF
- Rectifier bridge: 2 * YG 225D2
- Amp transistor D718 & B688 (made by KIA?)
- Coupling cap: couldn't find any ???
Now... I need a guidance on what can be replaced with higher quality without too much modification to the circuits.
I am thinking to replace the electrolites with higher value and higher quality such as panasonics or elna to improve bass.
I don't have a deep knowldege about electronics but I think the transistor is not mosfet type. Is it possible to upgrade it to better type?
Anymore suggestions?
Cheap sound usually comes from cheap design. Upgrading transistors and caps (unless they are damaged) may not help that much. However, if you cut the bandwidth to low frequency sub-woofer band, use it for a sub, then buy a smaller more expensive (better quality) amp for the mids and highs, cut that BW to it's respective frequency range (no bass), the overall sound will improve greatly. I recomend a good quality EQ also. Sometimes you just have to spend $$ for quality.
I second cunningham's comment. Most car amps (save for the few expensice ones designed for quality as opposed to megawatts of make believe power) are fairly cheaply designed. They use the bare minimum components to get the job done. The design is also not high quality - sometimes they can be designed pretty stupidly - since the amp OEM manufacturer did not spend money on the good engineers. I recommend using a high powered (real power, irregardless of how many fake "car amp watts" the amp pretends to have) amplifier for the subwoofer. This amp need not be of spectavular quality. Then you should use a smaller, but high quality, amplifier for your midrange and trebble speakers. Not much power is required here.
I don't think that you would gain much in a car amp by swapping around components for more expensive ones. The only ones I might take a look at would be the large lytics, and some of the stuff around the input (if it's noisy).
You might also want to check your bias. measure between the emiters of the two power transistors. there should be a coupla millivolts between the two emiters, accross the emitter balast resistors. I have this really cheap BOSS "500 watt RMS" (car amp watts, not real watts - the unit was fused at 15A) that had no bias (totally class B) with some quite bad crossover distortion on the output at low levels. The board did have provision for plaing the vbe multiplier next to the power devices, but they never bothered to mount that transistor so that it touched the heatsink. I didn't mess with the bias since it was set by fixed resistors and this was just going to be used to power a sub in a friend's "entry level, I don't want to spend anything to get slightly better than stock sound" system.
I don't think that you would gain much in a car amp by swapping around components for more expensive ones. The only ones I might take a look at would be the large lytics, and some of the stuff around the input (if it's noisy).
You might also want to check your bias. measure between the emiters of the two power transistors. there should be a coupla millivolts between the two emiters, accross the emitter balast resistors. I have this really cheap BOSS "500 watt RMS" (car amp watts, not real watts - the unit was fused at 15A) that had no bias (totally class B) with some quite bad crossover distortion on the output at low levels. The board did have provision for plaing the vbe multiplier next to the power devices, but they never bothered to mount that transistor so that it touched the heatsink. I didn't mess with the bias since it was set by fixed resistors and this was just going to be used to power a sub in a friend's "entry level, I don't want to spend anything to get slightly better than stock sound" system.
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