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previous: Sheldon Dingwall eth, what do you mean when you say ... -- 3/10/2004 3:27 AM

Re: Fernandez Sustainer -buildable?

3/11/2004 4:33 AM
eth	Re: Fernandez Sustainer -buildable? Sheldon, Basically what I was describing... And maybe not to concisely... Was How to build a sustainer. The LM386 power amp (~400mW) is a very common chip used to build a headphone amp. For simplicity, you can get everything needed to build a sustainer at radio shack, besides a scrap pickup. The books at radio shack are really cool, but the circuit for the headphone amp in those books doesn't work. It squeels! The reason is that the inductive load of a speaker or of a homemade sustain transducer, causes enough phase shift that the amp is unstable. To rectify this problem a resistor and capacitor is put across the load to counter the inductance and stableize the output. so.... I recomend, to everyone that wants to build a sustainer, to build a 'little gem' headphone amp found over at : runoffgroove.com. His amp design has the proper compensation. Don't use the radio shack lm386 circuit! It sounds: high pitched and annoying! As far as your pre-amps are going... They probably aren't oscillating because of an inductive load... There are many reasons a pre amp could oscillate, especially if it has more than one stage, has a funky feedback loop, or is of a jFet/mosfet input design without input damping.... Among other reasons that may be less common. If you gave me more info, I'd help. Do you manufacture active pick-ups? What kind? HB? SC? High gain? later- Ethan

3/11/2004 4:33 AM

eth

Re: Fernandez Sustainer -buildable?

Sheldon,

Basically what I was describing... And maybe not to concisely... Was How to build a sustainer.

The LM386 power amp (~400mW) is a very common chip used to build a headphone amp. For simplicity, you can get everything needed to build a sustainer at radio shack, besides a scrap pickup.

The books at radio shack are really cool, but the circuit for the headphone amp in those books doesn't work. It squeels! The reason is that the inductive load of a speaker or of a homemade sustain transducer, causes enough phase shift that the amp is unstable. To rectify this problem a resistor and capacitor is put across the load to counter the inductance and stableize the output.

so.... I recomend, to everyone that wants to build a sustainer, to build a 'little gem' headphone amp found over at : runoffgroove.com. His amp design has the proper compensation.

Don't use the radio shack lm386 circuit!

It sounds: high pitched and annoying!

As far as your pre-amps are going... They probably aren't oscillating because of an inductive load... There are many reasons a pre amp could oscillate, especially if it has more than one stage, has a funky feedback loop, or is of a jFet/mosfet input design without input damping.... Among other reasons that may be less common. If you gave me more info, I'd help.

Do you manufacture active pick-ups?
What kind? HB? SC? High gain?

later- Ethan

Replies:

Sheldon Dingwall "or is of a jFet/mosfet input desig... -- 3/12/2004 1:36 PM