Project 11.1 from Slone "High-Power Amplifier" Book

[Christer]

Originally posted by The golden mean
David of Lede audio seems to be a nice man. FWW A quote from a mail from him when I asked about the Optimos or the Totem Pole as a sub-amp:

"The Totem Pole would be my best selection for the job and if you run it to it's full capacity I expect the police will be around for a few drinks."

Maybe David can supply you with the schematics?

http://www.ledeaudio.com/about_us.html

Well, I am not that anxious to see the schematic that I want to beg for it. But just a brief explanation of the major differences between the amps would be interesting. Probably Slone would answer that if mailing him, but I wouldn't want to bother him with it. Sooner or later we'll probably find out, one way or another.

I think the answer you got gives a hint that more power and ruggedness might actually be the main difference.

[Fanuc]

Originally posted by megajocke
But that capacitance doesn't swing the whole output at +-50V as it's the gate-source capacitance. It will only swing +-10V - and that is if the amp is close to current limiting - effectively reducing gate source capacitance to 100pF as seen by the VAS. Gate-drain capacitance is only 8pF! Total capacitance of output stage as seen by VAS: ~300pF. 28mA into this -> 100V/uS. Bad devices will be worse of course OTOH gate voltage swing will be less than +-10V if driving an 8 ohm load

I am not sure the capacitance figures are right you mention. As this is load and frequency dependant irrespective of driver topology. Mosfet Zin and transconductance plus a capacitive load etc. I have never seen slew rates mentioned with non resistive loads etc. I think those slew rates for the output devices can only be acheived for the output stage by buffering with a follower ie. a much lower Zout follower upto HF than a VAS stage. Switch on and switch off capactance is likely to get worse at HF also.
imo. hope for the best but plan for the worst and buffer it!

Originally posted by bear
oh, yeah... BJTs do many things very well.
The thing that I do not like about them is that they "hard" clip - which is audible, very audible. Mosfets for whatever reason seem to be a bit "softer" on the edges (of the clipped waveform) and do not sound the same (better to my ears) when clipped... try to build an amp that does not ever get driven into clipping, get back to me on that one...

Very good points there esp. with electrostats and ribbons. Had a amp with BJT outputs with stats and it was horrendous when clipping. It must be designed for the job period. Cheap amps with small current delivery won't do. Am sure BJT's could do a good job here but has to designed well. Regarding clipping one way is to use baker clamps and/or different rail voltages. If the output stage is run slightly higher (a few volts) than the input/driver stage this may work.

An interesting comparison would be to use a generic Lin type and different outputs and compare clipping sounds and different techniques to minimise it.

Regards

Kevin

[djk]

BJTs drive E-stats just fine, if they're designed properly.

A Baker clamp will keep BJTs from going into common mode conduction when driving a capacitive load into clipping.

An APT Model One is a good example of and output and driver stage with such a clamp.

[HiFiNutNut]

Yes, please keep the "secrete" among just a few of us in the diyAudio forum.

My understanding is David from Ledeaudio got the rights from Mr. Randy Slone to sell the kits. This happened before the Canadian company bought some (possibly rather exclusive) rights from Mr. Slone.

So we are lucky that we can still get these wonderful designs in kits. Let us not to cause trouble for anyone.

I bought the Optimos kits from David 3 years ago. When the Totem-Pole was just released, I asked David if there would be any sonic difference. Daivd possibly had not built the Totem-Pole at the time but he told me it was designed for more power, more rugged for professional use but he suspected the Optimos would sound at least as good. I don't have more information than this.

[Christer]

Originally posted by HiFiNutNut

My understanding is David from Ledeaudio got the rights from Mr. Randy Slone to sell the kits. This happened before the Canadian company bought some (possibly rather exclusive) rights from Mr. Slone.

Very possible, but as I pointed out before, Zus is obviously involved in the kits too since their logo appears on the Totempole pcbs. Maybe Slone had already sold rights for the kits so his deal with Zus included Zus taking over the rights for the kits too?

[rckbrwn]

Amazon is advertising the new edition of the High-Power Audio Amplifier Construction Manual, due out in Nov 2008. It has info on the totem pole and class g amps. $26.37.

Rick

[Karl71]

Rick -

Thanks for the update.

Since I started the thread a few months ago, I have changed my speaker design goals and have returned to dynamic drivers.

I may pick the new edition up for Christmas.

Regards,

Karl