Crest 8001 - Value

We know tha hold there price,

Edited by Dub Specialist Sound - 22 February 2017 at 11:40am

8001 was my favourite amplifier to drive the bass. Of course it was about 20 years ago. I don't agree, with Viktor, this amplifier has very good sound, it was well designed, bullet proof build.
We had about 20 pcs. and we lost only 2 channels in 4 years, even with heavy disco usage. It was easy to repair, and even easy to make it more powerful :)
Agree, that the capacitors are expensive, but it's quite checp to replace them with the new snap in version, with a small pcb.

Sajti

Better start a Crest breakers yard then :)

From the guy who loves pkn

The Crest 8001 is a 2x 1200W (4Ohm) amplifier as far as I remember. May deliver 1800W peaks on 4R load for short periods... Its weight is ~40kg, consumes 3 or 4 rack unit spaces, has terrible power factor, poisoning mains with injected current peaks, its power valid only rock solid 220Vac due non regulated power supply..
Despite its large number of output transistors, did not perform very well on certain speakers because the output stage did not like largely shifted output current vs. voltage due heavy dissipation in the endstage.
As I remember it has a momentary U*I dissipation protection per output transistor arm and causes terrible sound effects when acted sometimes ;_)
So let us say the linear amp has made to deliver 50A peaks but if you have just half the output Voltage the output momentary current shall not exceeds 25A, which is typical with resistive loads.
Unfortunately the real speakers like to act as motors//generators so sometimes the maximum source and/or sinking current capability of endstage is required not only at time of peak Voltage events..
Here most of the linear amplifiers fall and properly constructed class-D win, which can deliver (or sink) its nominal output current at ANY output Voltage without the risk of exceeding momentary dissipation limits of the output power devices. This small trick is the secret sauce of good speaker control, what nobody tells you.

U.Viktor wrote: Most of you thinking about only Electrolyte capacitors what seriously defines lifetime of power electronics (amplifiers). Unfortunately this is not so simple in practice, power semiconductors also have "wearing out " effect which depends on how many and how big heating up and cooling down cycles received. In the analog amplifiers the dissipated energy of the power semiconductor is modulated by twice of the frequency of the amplified signal. Sharp temperature changes in the junction layer making some changes in the crystalline structure of the semiconductor, which may results failure sooner or later. This effect is present in switching-type of semiconductors (sw MOSFET, IGBT) too , but their structures have been designed to better handle this issue. Sorry to say this but the time has well went over the type of dissipative circuitry (analog, AB, classH), their linear transistors have never evolved to those levels like the switching couterparts. It means that the available low number of linear power devices are lagging ~20years back of today's "conventional"  power switching devices, in terms of power cycling capability, reliability, maturity of crystalline structures.

Mein Gott, I 100% agree with one of Victor's posts!!!


Edited by levyte357- - 21 February 2017 at 12:45pm