Gain Clone failure modes - Peter, et al?

[mgreene]

Hi,

About to fire up my battery powered "geen cloone" tonite. Will do initial testing on expendable speakers - but something has been plaguing my mind re the long-term deployment of the GC in my main system.

I have recently completed a very expensive speaker project and to protect it I have been thinking of installing mute switches or a DC sensing circuit for times when the GC is powered up but being not attended by myself.

Given the experience of those here with the LM3785’s self- protection circuits, if all checks out well on power up (offset, etc.), do I actually have anything to worry about?

thanks

Mike

[Ropie]

I lost a pair of nice TLs a few weeks ago thanks to my valve buffered LM3875 Gainclone. Now it has a £15GBP speaker protection kit from Velleman installed within; this has no noticeable effect on the sound and gives me peace of mind.

If you ask me, your "very expensive speaker project" would be a big loss, so if in doubt fit some speaker protection and stop worrying It will protect your speakers from any nasties and can have a switch installed so it can act as a mute circuit.

[Peter Daniel]

It's up to you, but I'm not using any protection on my speakers and didn't have a failure. The amps run constantly for over a year now.

But to have a peace of mind, a protection system wouldn't hurt anything, I guess.

[HDTVman]

If we assume (ya I know. It's that word.) that every thing checks out OK at first power up and continues to function normally into load resistors for up to an hour. Then I would think you would be OK. The best insurance is to be very careful during the construction. Check everything over, then check it again the next day before you power up the amp.

If your build quality is good and the amp checks out and runs on the bench for a while I think you are good to go. These are very simple circuits, at least the part on the outside of the chip. If you are careful and pay attention to details you will be fine.

Later BZ

Adding other circuits as part of the amp circuit require that the reliability of those circuits be taken into account as well. If an other part of the system causes the output of the chip amp to do something odd, it's not the chips fault, is it? (Tubes warm up slowly and can have large voltage swings in the process. How it this the 3875's fault?)

[mgreene]

Ropie,

I notice that Velleman has two kits - one is K4700 and another cheaper one that is unpowered. Which one are you using?

Thanks

Mike

[mgreene]

HDTVman,

That's pretty much what I figured and I have been careful - yet the possibility of a failure still nags.

Pete,

I take your point - I can't really see how anything can go wrong, I haven't worried about this on any tube amps I have built - but better safe than sorry, I guess.

Mike

[tiroth]

In my opinion, you don't need protection circuitry with a basic gainclone. These chips are extremely well protected by the internal circuitry. Now, if you put a buffer or preamp in front of it that is DC coupled, and your buffer blows up or latches to the rails, that isn't the gainclone's fault.

[Ropie]

Hi Mike,

I'm using the K4700

[wytco0]

Ropie, where did you get the K4700 from? I cant find it in maplin or CPC which the vellman site staes as UK sellers?

Thanks.

[Nuuk]

Ropie, where did you get the K4700 from? I cant find it in maplin or CPC which the vellman site staes as UK sellers?

Not Ropie but I know somebody who bought one from Maplin last week. Give them a ring and ask if you cannot see them on the site.

PS I just went to the site, typed Velleman into the search box and it came up half a dozen items down on the results page. Order code VE24B.

Now don't all rush guys, but these are seemingly under-priced by about 50%!