Do we need Zobel with chip amps?

[Peter Daniel]

Regarding 1K series input resistors. Could a smaller value be used (like maybe 220) or 1K is there for a reason?

[Peter Daniel]

OK, I tried Zobel in my reference system and I have no doubts it degrades the sound. THe soundstage collapsed and the liveliness is gone, although highs "might" seem to be smoother.

Also, in this system the cables are probably an easier load, as in the first one I was using 1" copper foil, while here a more conventional cable is used, from DH Labs (Q10 if I remeber correctly).

I'd say, try Zobel for yourself, if it works for you, but don't assume it's really required because National's designers are using it

[Jamh]

Originally posted by Fred Dieckmann


No...... you're second guessing the guys at National and other competent amp designers know what a Zoble network does it put it in an amplifier for a reason.

What is a fast speaker cable? In terms of inductance, capacitance, and
dieletric constant of the insulation. What difference does being thick make to the speed?

Thick as in gauge, and low inductance. My experience comes from trying and using my ears, as opposed to "accepting" competent engineers at National. You complain about the extra solder lead but don't wince at adding 2 extra components. I don't mean to say that Zobel networks don't have their place. If you find they help, by all means, go for it. In my system, the amps sound better without it. For what is worth, I use Jordan full range drivers with a 22 gauge 5N silver wire.

[Jamh]

I sound exactly like Peter! I didn't read his reply until I posted mine

[Fred Dieckmann]

"You complain about the extra solder lead but don't wince at adding 2 extra components."

They are not extra parts.......... they are part of the design.

* I hear that a lot from guys who know nothing about design. Unfortunately it's about issues where design choices make a difference. The Zobels belong in the design. One of the actual designers of amps based around these ICs has told me about all the problems people had have thinking that they can just leave the network out. I guess the next guy who trys this and has the amp oscillate can call you to tell him how to fix it without using the Zobels that are part of design.

'I'd say, try Zobel for yourself, if it works for you, but don't assume it's really required because National's designers are using it"

Just assume PD knows more than the guys that designed the IC. Here's someone else to call when your amp oscillates.........

[Peter Daniel]

Originally posted by Fred Dieckmann
One of the actual designers of amps based around these ICs has told me about all the problems people had have thinking that they can just leave the network out

That is interesting. I am an actual designer of amps based around those chips as well, and I can't tell you about the problems people have with amps oscillating.

Could it be that I'm using slightly different parts or different layout? Or maybe my grounding techniques are simply better? Or maybe it's just a pure lack, that a not experienced designer for some reason experiences once in a while?

It's not like I've built one or two amps. Those amps have been sold in quite substantial number, and I can assure you that there was no problem because Zobel was missing. We had the amps at the shows, we had them sent for reviews, the kits were built using the basic design, and I don't hear people have problems.

So what is your problem?

[Peter Daniel]

Why it all this starts to remind the Aleph X thread, when Grey presented his schematic? You also said it won't work. Hundreds of people built it and it works fine. I'm really desappointed with your expertise.

And I don't care what National's designers suggest to use with the amp. I'm building amps my way and it shouldn't be your concern what my actual choices are. Buy it and try it out. Then talk about it.

[dfolson]

National may recommend the Zobel to cusion the specifications of the op-amp. There have been and will always be designs that do not follow a manufactures reccomendations. This does not imply a poor design or an instable one either. It only requires care that you do not over drive the chip beyond its physical limits. I know a famous designer that did design his circuit outside the mfg specs, and even worked with the mfg to ensure it was a safe design. 20 years later my purchased model of this commercially produced amp is still going strong. (Wardsweb may know who I mean) There is an incredible amount of gamesmanship when it comes to a mfg writing a spec sheet.

Peter - keep on going!

Regards, David

[Fred Dieckmann]

There are people who have been building and selling Chip amps a lot longer than you have that have told me repetedly about the problems people run into by leaving the Zobel out of the design. If you actually look at a few schematics you will see that many amps use Zobel networks. I have buit chip amps. The LM1875s I built sounded better with a Zobel. I can only offer advice based on listening and sound engineering choices. I have a hard time believing you have sold hundreds of amps by the way. What you do with your own stuff is one thing, but offering design advice that will help insure the people have stable amps with many types of speaker loads and cables since to be good advice to me. But your the amp designer..... I guess you know best as usual. What do I know I am just a lowly EE who actually listens,measures, and advocates consistent performance and reliability . And, BTW I have been building and designing audio for about 30 years and was using parts that you seem to think are new discoveries, ten years ago. But then again I am not part of the Chip amp cult were building a circuit from the ap notes (and not even doing that right sometimes) in the data sheet makes one an amp designer.

[karma1968]

i have one of peters amps and its been working for a few years now with no problems

now if i could just get it off my kid that would be nice