Why not noiseless-bias BSIAB2 and Pinnacle style circuits?

[darron]

So used to seeing the 470k/470p combination in series with a large pot. Would there be less noise if a follower were after the gain stages and scaled down part values were used, say scale the parts by a 10X? (47k/4.7n/50k)

the input impedance and the internal capacitance of the amplification stage must be taken into account. Unlike operational amplifiers, discrete amplifiers can be dependent on these values. I will be a bore (haha) but once again I will speak out against the idea of ​​​​Mu Amp. This design is not as well filtered as single transistors, and wave clipping is not like the class A amplification of single transistors or triodes. My verdict, Mu Amp and Jfet should have retired a long time ago (especially since they are getting harder to buy). Instead of Mu Amp, it is better to use Baja-style OpAmp, it is more predictable and flexible. If you need the behavior of a triode, look to Mosfet, it is also more predictable and flexible.

Cool. Not a bore. Definitely good thoughts. I remember when this circuit was the most highly recommended DIY build for a while. And this style of high gain FET circuits took off into a commercial race and we stopped talking about the poor BSIAB2 mostly lol.

I don't really love the sound of the MuAmp clipping. And this circuit blasts the crap out of it. The only grace is that you get the single FET recovery to compress it a bit more sensibly at the end. The 5K6 resistor doesn't ask for crazy gain out of that stage. So I always figured that nastiness and recovery was a part of how the circuit handles chuga-chuga palm muting attacks and stuff so well. I don't take it too seriously to match sounding like an actual valve amp.

I guess if it was never a great topology for clear-distorted audio, then why are we bothering to simulate it now with FETs? lol hmm... Good food for thought... Thanks.

[POTL]

http://www.geofex.com/Article_Folders/modmuamp/modmuamp.htm

here is an old but useful article. Mu Amp output like tube triode has high impedance, triode takes into account the output impedance + anode resistor, this results in the need for high value resistors. The last schematic shows a simple mod, with the addition of one resistor, which will buffer the output and make the output impedance less than one kΩ. I may be wrong, but the impedance and capacitance at the input of Mu Amp are also demanding for a large value. to be honest, a few years ago I would have given a more complete answer, I have long lost interest in circuits using Jfets due to their many shortcomings and the specificity of sound.

[POTL]

Darron

The reason why so many people love Mu Amp is simple. no need to bias the transistor, making it easy to assemble and good for commercial use. most builders don't learn how it works and just copy what works and is easier to put together. I'm much more interested in ideas Zvex Baja Johnny Reckless They can really be tuned in terms of frequencies and clipping very close (especially the last 2) Jfet and Mu Amp cannot do this. but people believe that it is possible to take the amplifier circuit, without changing the components, simply by replacing the triode with j201 and shifting it to maximum gain. although all this is gradually fading against the backdrop of temporary DSP. They are the future.

[printer2]

One more time but with feeling.

Gain stage type aside. Would there be a reduction of noise (hiss) by dropping the resistor values and scale the capacitor values along with them? 

[PRR]

One more time but with feeling.

Gain stage type aside. Would there be a reduction of noise (hiss) by dropping the resistor values and scale the capacitor values along with them? 

No. The gain is in the thousands. All the hiss is from the input (and absurd gain), not the output network.

[darron]

One more time but with feeling.

Gain stage type aside. Would there be a reduction of noise (hiss) by dropping the resistor values and scale the capacitor values along with them? 

No. The gain is in the thousands. All the hiss is from the input (and absurd gain), not the output network.

I won't feel bad about knowing I was too lazy to do the experiment now.

I think the noise levels on the BSIAB2 aren't particularly bad, considering the gain you squeeze. Having the drive knob after the first hefty gain stage helps. Maxing the drive knob is too much. But I wouldn't want to take that function away either! haha.

[printer2]

One more time but with feeling.

Gain stage type aside. Would there be a reduction of noise (hiss) by dropping the resistor values and scale the capacitor values along with them? 

No. The gain is in the thousands. All the hiss is from the input (and absurd gain), not the output network.

Good to know, thank you.