Another simple amplifier, this one from North of Europe

[destroyer X]

The language i have read, seems that it should be somewhere near Norway.

One word....Jackaard...gave me this idea.

This circuit is interesting to Diy...it may work with 47 volts simetrical.

And will be not difficult to reach 180 Watts at 4 ohms...maybe more than a hundred watts over 8 ohms.

It is simple, beautifully bootstrapped (i like those circuits, Yamaha and Kenwood use them often now a days), do not use hard to find or expensive parts, and it seems that will produce a nice sound.

No!..i did not construct it....but i am thinking about, but first will be the Molerkamp.

Please, post your modifications suggestions, tell us if you already heard this one. how it sounds and those things.

This is all fun!

regards,

Carlos

[lineup]

Tell us if you already heard this one.

not easy to tell anything

we dont know name of amp
we dont know who designed
we dont know any websource

we only know a schematic with some missing data
might be your own drawing, circuit even ....


Carlos
If you want some input
you have to give me a little more to refer to
At least if you want my opinion


regards
lineup

[destroyer X]

I was in the WEB surffing and trying to have different PC power supply schematics when some new power amplifiers schematics appeared....because i have typed POWER supplyes....and they appear, as they are power.

I know the same as you know...just offering to people that want to try, or know something to make comments, or tell us what they feel observing the schematic.

Those things.

I cannot tell you anything my dear...i am sorry for that.

regards,

Carlos

[bigpanda]

I've seen the schematic in several places and that is one of them :

http://www.pablin.com.ar/electron/ci...p260/index.htm

I had always been wondering why it nees no idling currrent adjustment? I think it's related to this also :


http://www.brunt.de/KE/Elektronik/28...erstaerker.htm

Is it really good for the power it claims to provide?

[destroyer X]

The 82 ohms resistor can be substituted by a trimpot (100 ohms) to adjust the bias.

They made this way as will work with 99 percent of the parts used...those three diodes will produce 1.8 volts....0.6 volts each one, and the resistor will increase into 3.6 volts, that will be interesting.


I think that will be more intersting to use 5 diodes and the trimpot, as will be needed 1.8 volts positive and 1.8 volts negative related the output line...biasing all those transistors adequately.


The sittuation in the schematic may underbiased that output units.

Also i think that those darlingtons need 220 picofarads (minimum) from colector to base to avoid oscilations.


Carlos

[Upupa Epops]

Carlos, you have rare talent, still find again and again " stone age " connections... Whatabout sometimes to visit patent office and look there, how is modern amp... I recomment to you, that you will be very surprized...

[AndrewT]

Hi Carlos,
you manage to post yet more rubbish.

Who ever heard of Re=47r, then the 100pF Miller comp capacitor
and the negative rail with the 100r voltage dropper with 47nF. What are we to think?

[Eva]

Hey, this is actually a VAS bootstrapped in both ends. It improves transistor linearity altough not as much as cascoding, while still providing rail to rail output. However, while the VAS strongly benefits from that, the linearity of the input LTP is reduced unless it's cascoded.

Involved components are 270ohm 1W resistor, 47uF 40V capacitor, 100 ohm resistor, and 47nF capacitor. The latter is required to prevent oscillation due to positive miller feedback at RF, and I know because I have tried it and I ran into the same pitfalls.

Output resistors are .47 ohm but the "." appears to be lost due to low-quality image conversion.

[Ultima Thule]

Carlos,

only you have shown up those schematics here on diya with light-blue background, isn't it so that you are trying to construct an amplifier and just want fool to us with the originator because you want others opinion without make a fool of your self?
Or else where did you find it, please give us the adress to the greate source of yours!

The circuit have one bootstrapp for driver and output stage, the other botsrapp on the low side is counteracting both LTP and VAS BD139, is this good???

And those miller cap on both side to rail is not good for PSRR!
If they are added to prevent oscillation it would be better to add base stoppers to output transistors first.

Cheers Michael

[teemuk]

Originally posted by Upupa Epops
Carlos, you have rare talent, still find again and again " stone age " connections... Whatabout sometimes to visit patent office and look there, how is modern amp... I recomment to you, that you will be very surprized...

I think a little bit of "back to the stone age - attitude" is always quite healthy. For example, modern circuits do perform better but they tend to be very complex. Complexity causes issues that might actually start to degrade performance. Constant current sources and other "modern" stuff are nice but the increased performance that they bring isn't really THAT huge. In my opinion, the circuit that Carlos posted is after a bit of tweaking a very good performer in some applications where too much modernism just isn't worth it.

Finally, here's some food for thought: I ran a ltspice simulation of bootstrapped quasi complementary stage and a ccs symmetric complementary stage. Sort of a "stone age" vs. "modern" test, though not 100% reliable... Attached is the FFT graph of both amps when they clip mildly. Green graph is the bootstrapped circuit.

Teemu K