Hi there to all audiophile jents who work on P. A. ralated gear. I have a Crest 8001 power amp on my bench . the problem with this unit is : I'm injecting a -10 db square wave signal into this amp. on my scope the signal looks fine for 4/5ths of the gain level but for the last 5th as turn it up, the signal it starts to loose power . The signal strenth starts to get distorted. And this is semetrical on both channels. Power supply seems OK. But I was reading other blogs on this amp and found out that the power supply caps on the supply rails as well as other caps involved in this circuit could be the culprit. I did obtain a schematic on this amp but there is no service manule per say. Please offer any advice, if anyone can on this amp. Thanks so much.
Maybe that is actually how it's supposed to work (from their literature):
8001 protection circuitry:
- Clip Limiting prevents speaker damage with gentle gain
reduction at clip threshold.
- IGM (Instantaneous Gain Modulation) monitors connected
loads to detect conditions that may overstress output
devices, allowing safe operation into nominal 2 Ohms.
A 10Khz square wave needs 300Khz bandwidth to look really square.
Pro amps have protection to prohibit this.
Pro amps have protection to prohibit this.
To DJK : Thanks so much for your input, but I had another 8001 that I troubleshot and fixed . And when I injected the same signal into that amp the signal strenth showed no reduction in value , it contenued to show signal strenth as turned up the attenuation all the way. Maybe some amps act differantlly then others of the same make and model. But I will try my bench freq oss. insted of the behrenger 100 cable tester that I always use. The Behringer has a 400 and 1000 hz hz tone gen. in it . But it puts out a square wave signal rather a AC oss wave form. So I will try my bench freq oss. to see if that makes a differance. Thanks again for your help.
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