fender harmonic vibrato with MOSFETs

[cbass]

Its OK to make fun of me and or the amp . it'll look better when I'm done
Is the irf820 still the ones to get?

[matt h]

i haven't spent time searching the ixys ones RG pointed out (depletion mode, like the lnd150 just with better ratings). I'd be tempted to use lnd150 (or those ixys) for things that looked like gain stages, and irf820 (or some other enhancement mode) for things that look like cathode followers. just my personal immediate thought-light take on the options. on the whole, that'd probably mean fewer adaptions for using mosfets in the first place. extra grid, er, gate, stoppers... protection zeners throughout. but shouldn't need crazy biasing apparatuses shoehorned in.

[cbass]

Also will I need to . heatsink these or will just bolting to the chassis suffice

[matt h]

(deleted)

[R.G.]

Deleted; I'm willing to be polite.

[matt h]

RG I'm not sure why you're setting up your post as contrarian as you're agreeing with almost everything I've said.

To clarify: I was saying that adding protection zeners and gate stoppers was still necessary--but that's adding onto a circuit, not modifying, making a tube-to-sand conversion easier. Getting into biasing the enhancement mode stuff may not involve the addition of a ton of other components, but there's a larger degree of monkeying involved getting them to work right. (simulate, build, test, recalculate, adjust), and the issues of a fixed/grid bias can complicate things if, for instance, you were trying to work from a pre-existing layout. It's not that it can't be done, but if there isn't a tangible/ready benefit for going down that road, I don't much see the point.

And to spell it out more clearly, the to-92 package (or whatever the designator that the LND150 and other small ones) don't have the provision for chassis mounting/heatsinking that i'm used to seeing.

The one point actually in the disagreement game: longevity, the only thing I can say is that looking toward commercial production, with thousands of units sold, might be a more statistically useful sampling than anecdotal reports of any one builder. Yup, a lot of commercial production is run by idiots and a lot of individual builders aren't idiots. But from a sampling perspective, if these things were regularly run beyond what they can handle, they'd be expiring and we all know how prone to "FRAUD! SCAM! INFERIOR!" reviews of aftermarket boutique sales gear go. I haven't seen that erupt for the mojo or metro loops, which, current wise, should be pretty on par with the application of the fets as in the harmonic trem.

(vs the flat out bad design of the reverb add on that used them posted here recently, where it's more likely that not enough units have been produced/sold/installed to generate bad fraud/scam/inferior/itbroke reviews. Just a hunch.)

[shane]

Just out of interest, Supertex do the DN2540 which comes as a TO-220 package and according to the data sheet handles 400V and 15W, and like the LND150 is a depletion mode device.

dunno if that would be of any help.

Cheers
Shane

[matt h]

Shane, thanks for another option with a part number! for something like the trem it'd probably be overkill (my semi-informed opinion) but those sound like they'd be ideal for a reverb-driver solution if you had an amp already set up for tube driven reverb but needed to save the tube.

[R.G.]

Deleted.

[matt h]

Maybe it's a generational thing, or a cultural thing, but I find what you're doing incredibly rude. I'll keep this short so you don't have to quote much, split it into seventeen blocks of text, and pontificate much more.

[Phil_S]

Whoa! I'm not the moderator, but this sort of exchange bothers me. We were busy having fun with amps and suddenly the thread has a tone no one wants to see. What I see here is two really knowledgeable people getting off on the wrong foot. What's worse is they agree on the subject matter!

May I humbly suggest that there has been a rather innocent misunderstanding? While there are no do-overs in real life, here in the cyber-net it is possible to delete the posts that led to this. Maybe you two can back up, do that, and let this pass? C'mon fellas. Someone has to go first. Just do it.

[matt h]

May I humbly suggest that there has been a rather innocent misunderstanding? While there are no do-overs in real life, here in the cyber-net it is possible to delete the posts that led to this. Maybe you two can back up, do that, and let this pass? C'mon fellas. Someone has to go first. Just do it.

Nope, it was intentional. I'm not deleting anything and stand by my words 100%. I'm also content to leave TAG if this is the new normal.

[Structo]

Try to get along, alright?

This was a great thread until the bickering started.

[matt h]

It wasn't bickering and calling it such legitimizes unacceptable behavior. It was a one sided trollsault.

Someone can call me when this is over.

[R.G.]

So how about it Matt? Shake hands and be friends?