Hello guys, I have a question for you. I have a Crest amp that is very low in volume. It sounds like 200 watts as opposed to 540 watts, both channels work fine. I sent it to my repair guy to have it checked out. Where would you start on a repair like this. Would you look for blown heatsinks or transitors? Would you check the output module first? I know it could be multiple things. I looked under the amp before I sent it and nothing looked burned on the boards. I just wanted to know how would you begin on a job like this. What are important parts to check out? thanks Ern
So it is possible for an amp to be delivering the full amount of wattage eventhough it sounds like it's not. I know it isn't delivering 540 watts because I compared it to my other Crest watt version of the same series. It sounds Even less than 200 watts. I read other posts and they said power amps can be very unforgiving and should be properly serviced. This amp was run day and night. It recieved alot of abuse. I understand why you guys charge alot, finding the problem can take time.
Thanks Chris
Thanks Chris
I happened to think of Crest amps in another context, then saw this thread.
1) You do not have blown outputs. Amps do not continue to function with blown output devices.
2) Amps do not lose power from being played, no matter how hard or how long. (We'll leave the question of bias drifting for another time--Crest is Class D.)
3) Do not be surprised if your amp is functioning properly. Those who think all amps sound the same are...well, let's just say they exist, and leave it at that. It's possible that this amp sounds different from what you had expected, without necessarily being defective.
4) The idea of trying to judge power by ear is foolhardy. First, note that tube amps often sound more powerful than their ratings would suggest. Second, the power supply has a lot to do with how "loud" an amp sounds. Third, 540W is not that much louder than 200W...it's a log scale, not linear.
Grey
1) You do not have blown outputs. Amps do not continue to function with blown output devices.
2) Amps do not lose power from being played, no matter how hard or how long. (We'll leave the question of bias drifting for another time--Crest is Class D.)
3) Do not be surprised if your amp is functioning properly. Those who think all amps sound the same are...well, let's just say they exist, and leave it at that. It's possible that this amp sounds different from what you had expected, without necessarily being defective.
4) The idea of trying to judge power by ear is foolhardy. First, note that tube amps often sound more powerful than their ratings would suggest. Second, the power supply has a lot to do with how "loud" an amp sounds. Third, 540W is not that much louder than 200W...it's a log scale, not linear.
Grey
GRrollins you noted it could be the power supply. I know something is wrong with the amp. I took the amp apart and cleaned it completely from the aluminum heatsinks to the fans and even the boards. I didn't see anything burned. I did notice the ceramic heatsinks were a grey light brown and a few had been replaced, but those were a bright white.
You mentioned it could be the power supply? Do power supplies go bad? This amp was run day and night in a casino, it is from the Stardust that closed down a few months ago. The seller said he didn't get to test the amp with speakers, he only turned it on. I know the amp isn't performing to it's potential because I own A Bgw that is 230 watts at 8 olms per channel. My speakers are 250 watts rms. This amp clipped at times. I needed more power. I decided to purchase a used 7001 Crest which is 550 watts at 8 olms per channel. When I tried out the Crest it was less powerful than the Bgw. I had to put the volume on the mixer up three or more notches for sound almost as loud as the Bgw. That didn't sound right to me. Even my brother noticed the amp was not perfroming to it's potential. A 220 watt Bgw can't be louder than a 550 watt Crest. This is my second Crest amp. I love the thick, tight, tube like, low end bass of Crest. My local repair shop wasn't able to find anything visably wrong with the amp. They wanted to see the schematics and told me about adjusting the gain. My gutt feeling was they were not to knowlegable about this amp. I decieded to take it somewhere else. What could be causing this problem? I am probably going to take it to Audiospecialist.com on monday to have it repaired. Thanks for the reply Ern
You mentioned it could be the power supply? Do power supplies go bad? This amp was run day and night in a casino, it is from the Stardust that closed down a few months ago. The seller said he didn't get to test the amp with speakers, he only turned it on. I know the amp isn't performing to it's potential because I own A Bgw that is 230 watts at 8 olms per channel. My speakers are 250 watts rms. This amp clipped at times. I needed more power. I decided to purchase a used 7001 Crest which is 550 watts at 8 olms per channel. When I tried out the Crest it was less powerful than the Bgw. I had to put the volume on the mixer up three or more notches for sound almost as loud as the Bgw. That didn't sound right to me. Even my brother noticed the amp was not perfroming to it's potential. A 220 watt Bgw can't be louder than a 550 watt Crest. This is my second Crest amp. I love the thick, tight, tube like, low end bass of Crest. My local repair shop wasn't able to find anything visably wrong with the amp. They wanted to see the schematics and told me about adjusting the gain. My gutt feeling was they were not to knowlegable about this amp. I decieded to take it somewhere else. What could be causing this problem? I am probably going to take it to Audiospecialist.com on monday to have it repaired. Thanks for the reply Ern
Yea, but then that would mean the amp is working to hard. The shop said they couldn't find anything visably wrong, but they still wanted the schematics and said some adjustments could be done to it.
That is exactly what they told me. I saw some adjusters that require a philips screw driver on each board attached to the aluninum heatsinks, but I'm not about to mess with those. I'm going to let the techi handle it.
The shop said they couldn't find anything visably wrong, but they still wanted the schematics and said some adjustments could be done to it. That is exactly what they told me. I saw some adjusters that require a philips screw driver on each board attached to the aluninum heatsinks, but I'm not about to mess with those. I'm going to let the techi handle it.
"Yea, but then that would mean the amp is working to hard."
At the risk of repeating myself:
You are confusing gain with power.
You are like the person that is driving their car at 120 mph and has the pedal half way to the floor, and you think: Boy if I push it all the way it will go 240 mph.
Have the shop measure frequency response and gain. I doubt there is anything wrong with the amp.
If both amps have the same gain, the mixer will have to be turned up to make the bigger amp play louder.
If the BGW has more gain, then the mixer will have to be turned up MUCH louder to get the Crest to put out full power.
At the risk of repeating myself:
You are confusing gain with power.
You are like the person that is driving their car at 120 mph and has the pedal half way to the floor, and you think: Boy if I push it all the way it will go 240 mph.
Have the shop measure frequency response and gain. I doubt there is anything wrong with the amp.
If both amps have the same gain, the mixer will have to be turned up to make the bigger amp play louder.
If the BGW has more gain, then the mixer will have to be turned up MUCH louder to get the Crest to put out full power.
I think the BGW's only need .775 volt to get full power and I believe the Crest amps need 1.4 volts input to achieve full power.
I checked both the BGW and Crest site to verify my information. Some amplifiers have a gain switch that can be changed to effect gain.
Both DJK and GRollins have hit the nail on the head here with their answers. You are thinking there is a problem because you believe the Crest isn't as loud as the BGW is. Well, the problem lies with the gain needed by the amplifier to achieve full power.
One solution would be to have a competent technician build a pad for the BGW amplifier so that it would require the same input signal as the Crest to achieve the same power output. This is a common fix in commercial installations that require different amplifiers. Another common fix is to use a DA(distribution amplifier) and this would allow you to match the gain needs of both amplifiers and achieve matching output levels.
I guess we shouldn't rule out common sense here either. With your knowledge of sound system products maybe you should have consulted with a professional for an opionion to find out if the amplifiers would be compatable with each other or if modifications or changes were needed.
No, your NOT going to be able to judge power output based on what you think you might be hearing. Noted experts in the field have tried to answer your questions and you haven't paid attention to their answers. I suggest that you put your faith into people that have the knowledge instead of relying on what you preceive to be correct in your own mind.
I suggest that you either have a technician built an input pad or purchase a DA in order to match gains if you are using both the BGW and Crest in your system.
I checked both the BGW and Crest site to verify my information. Some amplifiers have a gain switch that can be changed to effect gain.
Both DJK and GRollins have hit the nail on the head here with their answers. You are thinking there is a problem because you believe the Crest isn't as loud as the BGW is. Well, the problem lies with the gain needed by the amplifier to achieve full power.
One solution would be to have a competent technician build a pad for the BGW amplifier so that it would require the same input signal as the Crest to achieve the same power output. This is a common fix in commercial installations that require different amplifiers. Another common fix is to use a DA(distribution amplifier) and this would allow you to match the gain needs of both amplifiers and achieve matching output levels.
I guess we shouldn't rule out common sense here either. With your knowledge of sound system products maybe you should have consulted with a professional for an opionion to find out if the amplifiers would be compatable with each other or if modifications or changes were needed.
No, your NOT going to be able to judge power output based on what you think you might be hearing. Noted experts in the field have tried to answer your questions and you haven't paid attention to their answers. I suggest that you put your faith into people that have the knowledge instead of relying on what you preceive to be correct in your own mind.
I suggest that you either have a technician built an input pad or purchase a DA in order to match gains if you are using both the BGW and Crest in your system.
In the simplest of terms. as this person does not understand the difference between gain and volume.
The BGW requires less input volume to reach full power, and the Crest requires more input volume to reach full power.
again, the BGW may only require you to turn your mixer fader up 1/3 of the way to produce enough signal from your mixer to run the BGW to full output.
Where as the Crest, may not have as sensitive of an input and may require more voltage, meaning you have to turn your mixer fader up father to run the Crest to its full power.
To use DJK's analogy,
Lets say you climb in your Honda, and lets say that 100mph is the fastest the car will go. you hit the freeway, you may only have to push the pedal down 1/3 of the way to get the car to 100mph.
Now lest say you climb into a corvette. Lets say it has a 150mph top speed. because the throttle may not be calibrated the same way, you may have to push the pedal half way down to get the car up to 100mph. and it may require you to push the pedal even further to get to top speed of 150mph.
at 100mph Both cars going the same speed even though the pedal is in a different posistion. same difference with your amplifiers. not every amplifer is the same. and knob posistion doesnt mean diddle squat in relation to output power.
You could have an amplifier that is only 10 watts, but has a very sensitive input stage that only requires you to turn your knob up to 1, that does not mean it has more power then your Crest, just that it is not set up the same way internally.
You could have a 10,000 watt amplifier and have to turn your knob up to 11 and still not be able to get the amp to full power. again that doesnt mean anything other then the input section is not as sensitive as another amplifiers.
To test your amplifiers output power.
Your tech should be able to connect an large 8 ohm load resistor (rated for at least the amplifiers full power), an AC RMS reading voltmeter and an ocsilliscope to the amplifier speaker terminals.
then use a signal generator connected to the input and set for say 60 to 100hz and turn the volume of the signal generator up and watch the O-Scope until the wave form starts to flatten out. at that point back the signal generator volume down just enough so that the signal looks normal and there are no flat spots on the tops or bottoms of the wave.
Read the AC RMS voltage at that point. then use this simple formula to figure out output power.
RMS Voltage divided by load resistance = amps
Amps times RMS voltage = output power.
So lets say your tech measures 40 volts RMS(NOT PEAK!)
40/8= 5 amps,
5 amps x 40 RMS volts = 200 watts
at that same time your tech could also measure how much signal is coming from the signal generator to get that amp up to full power.
Your output power reading should be close to the amplifiers rated output. the voltage at the outlet that the amp is plugged into may sag and not stay constant under load like that and may effect power readings but you should be able to get close enough to know that your amplifier is working correctly.
performing this test for both amplifiers will give you an idea of the differences in power and how much input signal it takes to get the amp to full volume.
Hope that helps understand what these guys have been saying.
Zc
The BGW requires less input volume to reach full power, and the Crest requires more input volume to reach full power.
again, the BGW may only require you to turn your mixer fader up 1/3 of the way to produce enough signal from your mixer to run the BGW to full output.
Where as the Crest, may not have as sensitive of an input and may require more voltage, meaning you have to turn your mixer fader up father to run the Crest to its full power.
To use DJK's analogy,
Lets say you climb in your Honda, and lets say that 100mph is the fastest the car will go. you hit the freeway, you may only have to push the pedal down 1/3 of the way to get the car to 100mph.
Now lest say you climb into a corvette. Lets say it has a 150mph top speed. because the throttle may not be calibrated the same way, you may have to push the pedal half way down to get the car up to 100mph. and it may require you to push the pedal even further to get to top speed of 150mph.
at 100mph Both cars going the same speed even though the pedal is in a different posistion. same difference with your amplifiers. not every amplifer is the same. and knob posistion doesnt mean diddle squat in relation to output power.
You could have an amplifier that is only 10 watts, but has a very sensitive input stage that only requires you to turn your knob up to 1, that does not mean it has more power then your Crest, just that it is not set up the same way internally.
You could have a 10,000 watt amplifier and have to turn your knob up to 11 and still not be able to get the amp to full power. again that doesnt mean anything other then the input section is not as sensitive as another amplifiers.
To test your amplifiers output power.
Your tech should be able to connect an large 8 ohm load resistor (rated for at least the amplifiers full power), an AC RMS reading voltmeter and an ocsilliscope to the amplifier speaker terminals.
then use a signal generator connected to the input and set for say 60 to 100hz and turn the volume of the signal generator up and watch the O-Scope until the wave form starts to flatten out. at that point back the signal generator volume down just enough so that the signal looks normal and there are no flat spots on the tops or bottoms of the wave.
Read the AC RMS voltage at that point. then use this simple formula to figure out output power.
RMS Voltage divided by load resistance = amps
Amps times RMS voltage = output power.
So lets say your tech measures 40 volts RMS(NOT PEAK!)
40/8= 5 amps,
5 amps x 40 RMS volts = 200 watts
at that same time your tech could also measure how much signal is coming from the signal generator to get that amp up to full power.
Your output power reading should be close to the amplifiers rated output. the voltage at the outlet that the amp is plugged into may sag and not stay constant under load like that and may effect power readings but you should be able to get close enough to know that your amplifier is working correctly.
performing this test for both amplifiers will give you an idea of the differences in power and how much input signal it takes to get the amp to full volume.
Hope that helps understand what these guys have been saying.
Zc
mechaboy1,
No one is born knowing all this stuff. You have to learn it as you go along, whether it's in a formal classroom setting or by the seat of your pants. That said, it would help if you'd take your fingers out of your ears.
1) Yes, power supplies can go bad. No, yours hasn't gone bad. The amp wouldn't work if it had.
2) "I know something is wrong with the amp" means different things depending on who utters the words. If Nelson Pass or John Curl says it, you'd better get your meter out. But coming from someone who says 'it doesn't play as loud as I want it to' doesn't exactly qualify. Heed well the difference between power and gain. I could chime in here with yet another analogy, but I fear that it would be wasted words.
3) Repeating that the amp was run hard doesn't exactly impress people with your technical knowledge. Repeat after me: Amps don't run down. Period. They either work or they break. They don't lose power over time. There's not a timeline over which an amp 'uses up' an allotment of power that was put in at the factory.
Relax. It sounds as though the amp is fine. You have some expectations that need to be unwound so that you can give the poor thing a loving home.
Two options suggest themselves. One is to get a good book on electronics and learn a bit about what's going on. The other is to sell the amp, since you seem hell-bent on hating it.
Grey
No one is born knowing all this stuff. You have to learn it as you go along, whether it's in a formal classroom setting or by the seat of your pants. That said, it would help if you'd take your fingers out of your ears.
1) Yes, power supplies can go bad. No, yours hasn't gone bad. The amp wouldn't work if it had.
2) "I know something is wrong with the amp" means different things depending on who utters the words. If Nelson Pass or John Curl says it, you'd better get your meter out. But coming from someone who says 'it doesn't play as loud as I want it to' doesn't exactly qualify. Heed well the difference between power and gain. I could chime in here with yet another analogy, but I fear that it would be wasted words.
3) Repeating that the amp was run hard doesn't exactly impress people with your technical knowledge. Repeat after me: Amps don't run down. Period. They either work or they break. They don't lose power over time. There's not a timeline over which an amp 'uses up' an allotment of power that was put in at the factory.
Relax. It sounds as though the amp is fine. You have some expectations that need to be unwound so that you can give the poor thing a loving home.
Two options suggest themselves. One is to get a good book on electronics and learn a bit about what's going on. The other is to sell the amp, since you seem hell-bent on hating it.
Grey
Thanks guys I am now undertsanding, Thanks for the anology zero cool and Djk. I feel like I'm taking an online class and the teacher is knocking on my nogin. I learned the amp isn't getting enough amps to run at it's proper gain or the gain needs to be put up higher on the mixer. The Bgw requires less amps to reach it's full potential. Like burnedfinger said 1.4amps for the Crest and .775 amps for the BGW. The Bgw also has a more sensitive input than the crest which requires more amps and signal. I tried what you guys said, I put the gain on the mixer all the way up. Then I put the volume up. I heard a lot of snow. It was a little louder, but my eq was in the yellow jumping into the red. I am running the Crest and the BGW one at a time on a 20 amp circuit with no other lights or electronics connected to it. I have a 30 amp ciruit outside for my brothers band equipment, Should the amp run better on that plug? For my amp I run 12 guage quality extension cords mostly 25 footers no longer than 50 ft. Is my mixer putting out enough signal for the Crest. It is rated at .775v and a max of 8.0Vrms. Thanks Ern
Here are the specifications for the Crest
http://crestaudio.com/media/pdf/7001_3-25-97.pdf
Here are the specifications for the Crest
http://crestaudio.com/media/pdf/7001_3-25-97.pdf
Actually what I said was the BGW needs .775 VOLTS and the Crest needs 1.4 VOLTS to achieve full output.
Just so you are clear on this ... signal in volts and not amps.
I would guess your extension cords are large enough to carry the current. I would turn on the mixer and source gear first followed by one amplifier and then the second amplifier. I would guess your program signal is not going to make you blow the circuit breaker.
Have you said what brand and model of mixer you have? Maybe I just missed it. Rack mounted mixer or small table top unit?
Not meaning to help beat your head against the wall. Just trying to help you. The solution to your problem is to purchase a distribution amplifier. Take the output from the EQ into the DA and take one output from the DA into the BGW and a second output from the DA into the Crest. Set the output of the DA feeding the BGW to unity gain or to be simple...no gain or loss.
The output of the DA feeding the Crest will be turned up somewhat to provide the necessary gain so that the output of the two amplifiers are matched.
This will solve the problem without having to turn up your mixer all the way and hearing the hiss and noise associated with it.
Just so you are clear on this ... signal in volts and not amps.
I would guess your extension cords are large enough to carry the current. I would turn on the mixer and source gear first followed by one amplifier and then the second amplifier. I would guess your program signal is not going to make you blow the circuit breaker.
Have you said what brand and model of mixer you have? Maybe I just missed it. Rack mounted mixer or small table top unit?
Not meaning to help beat your head against the wall. Just trying to help you. The solution to your problem is to purchase a distribution amplifier. Take the output from the EQ into the DA and take one output from the DA into the BGW and a second output from the DA into the Crest. Set the output of the DA feeding the BGW to unity gain or to be simple...no gain or loss.
The output of the DA feeding the Crest will be turned up somewhat to provide the necessary gain so that the output of the two amplifiers are matched.
This will solve the problem without having to turn up your mixer all the way and hearing the hiss and noise associated with it.
Thanks burnedfingers, so the Da is used to balance the gain of the two amps, I looked them up and they are pretty expensive, but this is not what I want to achieve, I am trying to run only one amp, the Crest. In my mind it didn't sound like it was pushing my 250 watt speakers enough so I decided to compare it to my back up Bgw amp. The Bgw was louder. I took my equipment outside and ran a 25 foot 12 guage extension cord and connected it to the 550 watt 8olm Crest amp. It made no audible difference. The gain on the amp and mixer was adjusted all the way up and the volume was also almost all the way up I didn't want to send to much distrotion to my speakers. I disconected the Crest and then tested the 220 watt 8olm Bgw it was still louder than the Crest. I put the gain all the way up and the volume almost to the top. So when both amps are tested at seperate times with full gain and volume up the 220 watt amp is louder than the 550 watt amp and each was tested to a 30 amp curcuit. This didn't make sense to me. The mixer is a vintage 1775 ppd numark mixer from 82 or 83. It has cleaned volume slides and is very good working condition, never a problem. I don't want to run two amps only one. That is why I wanted to have the Crest looked over by a Tech. I should have explained it better. Thanks Ern
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