Hi everybody,
Recently I just bought a used SS amp MC 245. It has a little problem with the pop noise ONLY during on and off. However, the popping noise come from all channels EXCEPT the subwoofer output. I noticed that the sub out has its own relay, but not so for the other 4 channels. Anyone be kind enough to guide me to trace the culprit??
The DC output are small, but still it's annoying. Across 4 channels, it puts out 0.4 - 0.5 v. Help😀
Thanks
Recently I just bought a used SS amp MC 245. It has a little problem with the pop noise ONLY during on and off. However, the popping noise come from all channels EXCEPT the subwoofer output. I noticed that the sub out has its own relay, but not so for the other 4 channels. Anyone be kind enough to guide me to trace the culprit??
The DC output are small, but still it's annoying. Across 4 channels, it puts out 0.4 - 0.5 v. Help😀
Thanks
Simply delay the turn on of the amp by using a 1000ufd cap on the turn on wire.
This will stop that turn on pop, by giving you a few seconds turn on delay. the pop comes from all the other stuff before the amp turning on < they produce these noise issues that you amp simply amplifies and "pops" in your speakers.
That DC offset is not the culprit. Its a general condition indicator of how old that amp is. try new outputs to lower the DC offset and fresh power supply capacitors as a start to renewal of that classic amplifier.
Enjoy 🙂
This will stop that turn on pop, by giving you a few seconds turn on delay. the pop comes from all the other stuff before the amp turning on < they produce these noise issues that you amp simply amplifies and "pops" in your speakers.
That DC offset is not the culprit. Its a general condition indicator of how old that amp is. try new outputs to lower the DC offset and fresh power supply capacitors as a start to renewal of that classic amplifier.
Enjoy 🙂
Are you measuring the DC directly across the positive and negative speaker terminals of each channel?
Is the pop a loud pop or a mild click as the amp turns on?
Does the amp produce a turn on noise/pop without a signal source connected to it?
Is the pop a loud pop or a mild click as the amp turns on?
Does the amp produce a turn on noise/pop without a signal source connected to it?
I think there's some good idea's and some not-so-good idea's.
One of the suggestions was to add a 1000uF cap to the remote turn on terminal. The only R in this RC network is the wire resistance. If the wire resistance is 2 ohms and the cap is 1000uF, the time constant will be RXC = 2ms That'd be a little quick. If you install a series resistor, to "feed" the cap, you'll do better. a 2000 ohm resistor and 1000uF cap will give you a 2 second time constant.
...this is only usefull if the DC pop is coming from your head unit. If the DC offset is static and coming from your amp, this delay of turn on wont work.
If the DC is from your amplifier, I doubt that replacing outputs will work. I mean, yeah, the output MOSFET's could be leaky but the offset should get back to <70mVDC. If the offset remain, AND the heatsink doesn't get hot (feedback trying to correct with opposite current), you probably have a power supply problem. I say probably power supply problem as the problem is affecting more than one channel. Can you post a schematic?
One of the suggestions was to add a 1000uF cap to the remote turn on terminal. The only R in this RC network is the wire resistance. If the wire resistance is 2 ohms and the cap is 1000uF, the time constant will be RXC = 2ms That'd be a little quick. If you install a series resistor, to "feed" the cap, you'll do better. a 2000 ohm resistor and 1000uF cap will give you a 2 second time constant.
...this is only usefull if the DC pop is coming from your head unit. If the DC offset is static and coming from your amp, this delay of turn on wont work.
If the DC is from your amplifier, I doubt that replacing outputs will work. I mean, yeah, the output MOSFET's could be leaky but the offset should get back to <70mVDC. If the offset remain, AND the heatsink doesn't get hot (feedback trying to correct with opposite current), you probably have a power supply problem. I say probably power supply problem as the problem is affecting more than one channel. Can you post a schematic?
To justonemoreamp:
The idea of adding a capacitor on the turn on wire doesn't appeal to me since, it's not how the amp designer intended to be. However, I would consider using such method as my last resort, thanks though 🙂
Simple question: Would changing the output on the four channels and replacing caps on the power supply eliminates the pop? Prior to having this pop noise, the sub output blew and I replaced all TIP142/147. The sub channel is working fine now and by the way, can the sub output handle 2 ohm load??
To Perry Babin:
YES, I measured the DC directly across the positive and negative speaker terminals of each channel. The pop is rather mild and it produces DC spike without any signal source connected to it. I haven't tried testing it without signal source while connected to speaker. I would assume it would produces noise due to DC spike.
To mrshow4u:
How can pinpoint the problem area in power supply (assuming it's the problem)??
I haven't been able to post a schematic, but still working on it
😀
The idea of adding a capacitor on the turn on wire doesn't appeal to me since, it's not how the amp designer intended to be. However, I would consider using such method as my last resort, thanks though 🙂
Simple question: Would changing the output on the four channels and replacing caps on the power supply eliminates the pop? Prior to having this pop noise, the sub output blew and I replaced all TIP142/147. The sub channel is working fine now and by the way, can the sub output handle 2 ohm load??
To Perry Babin:
YES, I measured the DC directly across the positive and negative speaker terminals of each channel. The pop is rather mild and it produces DC spike without any signal source connected to it. I haven't tried testing it without signal source while connected to speaker. I would assume it would produces noise due to DC spike.
To mrshow4u:
How can pinpoint the problem area in power supply (assuming it's the problem)??
I haven't been able to post a schematic, but still working on it
😀
Post #5
To justonemoreamp:
The idea of adding a capacitor on the turn on wire doesn't appeal to me since, it's not how the amp designer intended to be. However, I would consider using such method as my last resort, thanks though
Actually I stole that idea from Phoenix Gold, Its in there hand book of problems and solutions, and FAQ's. Concerning turn on thump and the use of delayed turn on for the power amp to resolve the issue.
Simple question: Would changing the output on the four channels and replacing caps on the power supply eliminates the pop? Prior to having this pop noise, the sub output blew and I replaced all TIP142/147. The sub channel is working fine now and by the way, can the sub output handle 2 ohm load?
2 ohms ? I really doubt that it will live a long and healthy life unless you respect the fact that it is running at it utmost rating. By this I mean that this amp was built in the early years of car amps, and even if it was rated at 2 ohms, you will be placing it under a fair amount of stress at 2 ohms per channel, and should you decide to bridge, Well here again your looking at 1 ohm per channel loading, and I would give this amp maybe 5 minutes on a cool day at those load levels before your removing it to go to the shop for restoration.
As for replacing aged and stressed components like caps and outputs. While my experience says this is a good idea, I don't believe it will solve your issues. A delayed speaker connection relay setup would be the best I could suggest. I know for a fact this will resolve your issue without tampering with your amp internally at all. Clean, quick, outboard of the amp, and something you could implement without too much issue, or support from a service tech.
You said the thump is present even without RCA input applied to the amp, correct? And this problem was not present before the amp was repaired ??
If the above is true, then there may still be something overlooked during its last repair...
Good luck on your quest 🙂
To justonemoreamp:
The idea of adding a capacitor on the turn on wire doesn't appeal to me since, it's not how the amp designer intended to be. However, I would consider using such method as my last resort, thanks though
Actually I stole that idea from Phoenix Gold, Its in there hand book of problems and solutions, and FAQ's. Concerning turn on thump and the use of delayed turn on for the power amp to resolve the issue.
Simple question: Would changing the output on the four channels and replacing caps on the power supply eliminates the pop? Prior to having this pop noise, the sub output blew and I replaced all TIP142/147. The sub channel is working fine now and by the way, can the sub output handle 2 ohm load?
2 ohms ? I really doubt that it will live a long and healthy life unless you respect the fact that it is running at it utmost rating. By this I mean that this amp was built in the early years of car amps, and even if it was rated at 2 ohms, you will be placing it under a fair amount of stress at 2 ohms per channel, and should you decide to bridge, Well here again your looking at 1 ohm per channel loading, and I would give this amp maybe 5 minutes on a cool day at those load levels before your removing it to go to the shop for restoration.
As for replacing aged and stressed components like caps and outputs. While my experience says this is a good idea, I don't believe it will solve your issues. A delayed speaker connection relay setup would be the best I could suggest. I know for a fact this will resolve your issue without tampering with your amp internally at all. Clean, quick, outboard of the amp, and something you could implement without too much issue, or support from a service tech.
You said the thump is present even without RCA input applied to the amp, correct? And this problem was not present before the amp was repaired ??
If the above is true, then there may still be something overlooked during its last repair...
Good luck on your quest 🙂
To Bayiganteng:
To see if the power supplies aren't balanced and might be causing the pops. I'm not familiar with that amp and unbalanced supplies doesn't necessarily mean that the amp will pop. ...but
I would look at the front-end circuitry. The op-amps the filter and buffer the input signal. Look for (probably ) quad op-amps and look to see if their power supplies are symmetrical. You should have equal but opposites voltages at Vdd and Vss. If they are not, it could indicate that the power supply filters are opening. Most(all) powerful car amps have switching supplies, so an oscilloscope is handy for seeing the High Frequency ripple. The "pop" sound may indcate that one of the rails (Positive, or negative) may be coming up to it's filtered working voltage slower, causing the amp to be unstable at turn on. Perhaps the Subwoofer output doesn't pop because it has a mute circuit? ....I don't have the schematic so I don't know.
There is some possibility of some bad news here. Could it be that that model amp might pop by design? Not to say that the pop was the designer's intention, but just sloppy design??
If you can post the schematic and have an o'scope, I think this problem could be nailed in a straightforward manner (famous last words
)
Good luck,
Jon
To see if the power supplies aren't balanced and might be causing the pops. I'm not familiar with that amp and unbalanced supplies doesn't necessarily mean that the amp will pop. ...but
I would look at the front-end circuitry. The op-amps the filter and buffer the input signal. Look for (probably ) quad op-amps and look to see if their power supplies are symmetrical. You should have equal but opposites voltages at Vdd and Vss. If they are not, it could indicate that the power supply filters are opening. Most(all) powerful car amps have switching supplies, so an oscilloscope is handy for seeing the High Frequency ripple. The "pop" sound may indcate that one of the rails (Positive, or negative) may be coming up to it's filtered working voltage slower, causing the amp to be unstable at turn on. Perhaps the Subwoofer output doesn't pop because it has a mute circuit? ....I don't have the schematic so I don't know.
There is some possibility of some bad news here. Could it be that that model amp might pop by design? Not to say that the pop was the designer's intention, but just sloppy design??
If you can post the schematic and have an o'scope, I think this problem could be nailed in a straightforward manner (famous last words
)Good luck,
Jon
Hello,
Soundstream made a lot of MC-245's in the late 80's. It was the first 5-channel amp on the market and was made in the USA.
This was a common issue with the amp. At the end of production, Soundstream installed a small relay board that took care of this problem. You cannot buy it off the shelf. It was made by Soundstream a long time ago and only the last production units had them...maybe less than 100 of them had it installed. If you can find one...it would be a very rare find indeed!
The sub channel did have a relay but the other 4 channels did not. Most of the amps had a very slight noise.
Adding a cap to delay the turn on POP is OK, but the main defect is the amp. Way too much detail to go into now but, yes...it is the amp that is the real issue here.
Thanks
pugdogs
Soundstream made a lot of MC-245's in the late 80's. It was the first 5-channel amp on the market and was made in the USA.
This was a common issue with the amp. At the end of production, Soundstream installed a small relay board that took care of this problem. You cannot buy it off the shelf. It was made by Soundstream a long time ago and only the last production units had them...maybe less than 100 of them had it installed. If you can find one...it would be a very rare find indeed!
The sub channel did have a relay but the other 4 channels did not. Most of the amps had a very slight noise.
Adding a cap to delay the turn on POP is OK, but the main defect is the amp. Way too much detail to go into now but, yes...it is the amp that is the real issue here.
Thanks
pugdogs
Hello again,
While looking for something else in my vast "Closet of Mystery", I found a Relay board for the MC-245. I still have two MC-245's in my collection but I am willing to list one of the Relay boards on eBay. I do not ship outside of the US, but I am willing to ship it to a third party if you are interested. I have a copy of the original hand-drawn wiring diagram too. You will need a soldering iron, Phillips head screwdriver and a slotted screwdriver in order to do the modification. You will also need to secure the relay board with thin double-sided tape of hot glue to hold the relay board in place on the main PCB. You will also need to place some kind of insulator on the cover to avoid the connections from coming in contact with the cover. Mylar material is fine. It must have some kind of adhesive. It mounts upside down on the main board. (Relays down) There is very little room inside the amp, but it does fit. The wires are all cut to length and it is a very simple mod. I can send you a picture of the relay board and a PDF of the layout drawing if you are interested.
Let me know if you are interested and send me your email address.
I will not list it until I have heard back from you!
All for now....
pugdogs
😀
While looking for something else in my vast "Closet of Mystery", I found a Relay board for the MC-245. I still have two MC-245's in my collection but I am willing to list one of the Relay boards on eBay. I do not ship outside of the US, but I am willing to ship it to a third party if you are interested. I have a copy of the original hand-drawn wiring diagram too. You will need a soldering iron, Phillips head screwdriver and a slotted screwdriver in order to do the modification. You will also need to secure the relay board with thin double-sided tape of hot glue to hold the relay board in place on the main PCB. You will also need to place some kind of insulator on the cover to avoid the connections from coming in contact with the cover. Mylar material is fine. It must have some kind of adhesive. It mounts upside down on the main board. (Relays down) There is very little room inside the amp, but it does fit. The wires are all cut to length and it is a very simple mod. I can send you a picture of the relay board and a PDF of the layout drawing if you are interested.
Let me know if you are interested and send me your email address.
I will not list it until I have heard back from you!
All for now....
pugdogs
😀
Excessive output DC is usually due to small electrolytic capacitors in the signal path becoming leaky with age, bad solder joints resulting from strong vibration over years or just plain bad design... I think that the third cause has a lot to do with this amplifier, though.
The same reasoning is also valid for loud turn-on thumps, provided that they are still produced when the amplifier is turned on with preamplifier inputs disconnected.
BTW: You can blow the remote driver of some headunits and cause other more advanced ones to self protect and turn remote off if you ever connect a 1000uF capacitor between remote lead and ground.
The same reasoning is also valid for loud turn-on thumps, provided that they are still produced when the amplifier is turned on with preamplifier inputs disconnected.
BTW: You can blow the remote driver of some headunits and cause other more advanced ones to self protect and turn remote off if you ever connect a 1000uF capacitor between remote lead and ground.
Eva said:
The cap should go inline not across the turn on lead lol lol I was quoting the Phoenix Gold Tech tips 101 file on that one, and every turn on lead I ever saw was rated at 100 MA typical max current draw so Yes care should be exercised when connecting anything to a current limited line like this 😉 I must have fixed 10,000 of them back in the day....until people got smart and started using a single Bosch relay hooked to the deck to turn on all the extra stuff in the system.
Inline with the turn on lead will use the charge time effect to slow down the turn signal to the amp allowing the other units to thump all they want and settle before the amp sees turn on signal VIOLA no thump. FYI this has been done without issue since 1989 or there abouts... And is still done by older tech's that have seen their time in the cars. So nothing new or crazy here, just old timey knowledge from the past.
Myself I use a DD-10 by PG... 10 outputs with instant and delay variable timed with all 10 lines fused at 3 amps, Lots of pretty leds also.. DD-5's are still on e-bay for about $90 each, these are the last ones left of this design, alas they make them not anymore...I got mine lol
Pugdogs has the correct factory fix, and the original factory part to do it with also, "You the Man Pugdogs"🙂 🙂 🙂 🙂
Thanks Eva and C,
Yes, you are both right as it is a design issue and not an issue due to time or abuse. The amps had this problem right off the production line.
I have to make a correction though. I just pulled out my schematics and the original production release date for the MC-245 was December 1990.
Thanks for all the great input everyone. I'm very rusty here in the audio world these days as I have been out of the loop for over 8 years!
pugdogs
😀
Yes, you are both right as it is a design issue and not an issue due to time or abuse. The amps had this problem right off the production line.
I have to make a correction though. I just pulled out my schematics and the original production release date for the MC-245 was December 1990.
Thanks for all the great input everyone. I'm very rusty here in the audio world these days as I have been out of the loop for over 8 years!
pugdogs
😀
Desperate messures
After 2 attempts by so called professionals,repairing my Sounstream MC-245 I am taking this unit (from Canada) to Europe were ""school buddy""" has a repair shop to have him repair it. Schematic for this unit would be greatly appreciated by anyone who has one or advise me where I could obtain one.
Due to one side design (inputs and outputs) this unit is absolutelly imperative to have it working, otherwise I have to re-design my car's interior.
Please please anybody????
Thank you in advance
After 2 attempts by so called professionals,repairing my Sounstream MC-245 I am taking this unit (from Canada) to Europe were ""school buddy""" has a repair shop to have him repair it. Schematic for this unit would be greatly appreciated by anyone who has one or advise me where I could obtain one.
Due to one side design (inputs and outputs) this unit is absolutelly imperative to have it working, otherwise I have to re-design my car's interior.
Please please anybody????
Thank you in advance
Pugdogs has lots of experience with these , take my word for that statement I know this person very well, and I trust his word.
Other than that there is Pugdogs and mine and Perry Babin's friend, <Jaime>at JandR electronics is the only other certified and bonifide SoundStream repair source your gonna find my friend.
JandRelctronics < located in Sacramento Ca.> you can't go wrong with Jaime, he has a E-bay web-site so you can buy SoundStream parts straight from a SS person from the good old days...
Sorry to hear you been having tech troubles, but your answers are posted above... and I will swear by that fact.
Other than that there is Pugdogs and mine and Perry Babin's friend, <Jaime>at JandR electronics is the only other certified and bonifide SoundStream repair source your gonna find my friend.
JandRelctronics < located in Sacramento Ca.> you can't go wrong with Jaime, he has a E-bay web-site so you can buy SoundStream parts straight from a SS person from the good old days...
Sorry to hear you been having tech troubles, but your answers are posted above... and I will swear by that fact.
Hello,
Thank you Mr. "C" for the very kind words.
Yes, I was employed at Soundstream from 1985 to 2000 (Employee # 8) and saw a lot of amps over the years. I worked every position from assembly to Service Manager and everything in between. I also worked in the R&D lab for many years as well developing the Reference Series and the Rubicon Series amps. We had a lot of great people working for us then. Folks from NAD, Dolby Labs, JVC and other companies. Lots of very talented Engineers.
I am NOT an expert here anymore!(PLEASE NOTE!) My day is done.
Any amp repairs should be done by the ONLY person I trust in the world.
JandRelectonics. Jaime is your man! He ROCKS! BIG TIME!
Thanks Mr. "C" and Jaime.
If you need your amp fixed right the FIRST TIME...call Jaime!
pugdogs
Thank you Mr. "C" for the very kind words.
Yes, I was employed at Soundstream from 1985 to 2000 (Employee # 8) and saw a lot of amps over the years. I worked every position from assembly to Service Manager and everything in between. I also worked in the R&D lab for many years as well developing the Reference Series and the Rubicon Series amps. We had a lot of great people working for us then. Folks from NAD, Dolby Labs, JVC and other companies. Lots of very talented Engineers.
I am NOT an expert here anymore!(PLEASE NOTE!) My day is done.
Any amp repairs should be done by the ONLY person I trust in the world.
JandRelectonics. Jaime is your man! He ROCKS! BIG TIME!
Thanks Mr. "C" and Jaime.
If you need your amp fixed right the FIRST TIME...call Jaime!
pugdogs
Hello again,
One thing I forgot to mention...
If you are still trying to "fix" your amp for turn-on-noise you are chasing your tail and wasting your time and money.
There is only one cure for your amp at this point and that is the "ORIGINAL" Soundstream Relay Board that I mentioned a long time ago.
Unless you plan to re-design your amp from the ground up...and spend lots of $$$$, you are totally wasting your time.
I can send you a "Hard Copy" of my original schematic but I do not think there is a Technician out there that can fix your issue with a slight tweek of a cap or something. Trust me on this!
I have reviewed the schematics many times and see several fixes that "may" decrease the DC offset at turn-on but it can only be proved by testing it out. I do not have the time to do this anymore. All of my MC245's have the Relay Boards installed with no issues.
Food for thought.
Peace,
pugdogs
One thing I forgot to mention...
If you are still trying to "fix" your amp for turn-on-noise you are chasing your tail and wasting your time and money.
There is only one cure for your amp at this point and that is the "ORIGINAL" Soundstream Relay Board that I mentioned a long time ago.
Unless you plan to re-design your amp from the ground up...and spend lots of $$$$, you are totally wasting your time.
I can send you a "Hard Copy" of my original schematic but I do not think there is a Technician out there that can fix your issue with a slight tweek of a cap or something. Trust me on this!
I have reviewed the schematics many times and see several fixes that "may" decrease the DC offset at turn-on but it can only be proved by testing it out. I do not have the time to do this anymore. All of my MC245's have the Relay Boards installed with no issues.
Food for thought.
Peace,
pugdogs
Wow, it amazes me that this thread is still alive and obviously I'm not alone.
I would like to thank everyone who has helped me over the time. The amp is fixed and not a single popping noise (thump) and it's now working great, and what I did was just add an aftermarket relay and glued it onto the PCB 😀
Without everyone's contribution, my SS amp would probably still be sitting on a work bench and become a piece of furniture. So, once again. THANK YOU ALL!!
This site has helped me in a big way, being that i'm half way across the world.
🙂 🙂
I would like to thank everyone who has helped me over the time. The amp is fixed and not a single popping noise (thump) and it's now working great, and what I did was just add an aftermarket relay and glued it onto the PCB 😀
Without everyone's contribution, my SS amp would probably still be sitting on a work bench and become a piece of furniture. So, once again. THANK YOU ALL!!
This site has helped me in a big way, being that i'm half way across the world.
🙂 🙂
Super good news!!!
Thank God it is working now. All my best to you and I hope you will enjoy your MC245 now!
pugdogs
Thank God it is working now. All my best to you and I hope you will enjoy your MC245 now!
pugdogs
Dear Pugdogs:
You have mentioned in your post, about MC 245's DC Relay board's problem at turn-on of the unit. If my memory serves me right, that relay board was design for a subwoofer to turn on few seconds later in order to prevent sudden current surge to the power supply. That is not my problem with the unit, crackling and poping at higher volume however is.
You have mentioned that you have a hard copy of schematic for this unit . What would it take for me to obtain that schematic from you????? It would be greatly appreciated. Trust me on this.
P.S. I do have another Sounstream 245 amp working flawlesly for years and I wouldn't swith it for all the tea in China, exept maybe for a Crown car amp .
Can you help me with a schematics???
Thank you in advance
You have mentioned in your post, about MC 245's DC Relay board's problem at turn-on of the unit. If my memory serves me right, that relay board was design for a subwoofer to turn on few seconds later in order to prevent sudden current surge to the power supply. That is not my problem with the unit, crackling and poping at higher volume however is.
You have mentioned that you have a hard copy of schematic for this unit . What would it take for me to obtain that schematic from you????? It would be greatly appreciated. Trust me on this.
P.S. I do have another Sounstream 245 amp working flawlesly for years and I wouldn't swith it for all the tea in China, exept maybe for a Crown car amp .
Can you help me with a schematics???
Thank you in advance
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