Inductor Loading Adventures

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Ok, this little mystery about your not so square, square wave got the better part of me, so I decided to throw the same amp together as you have, just with a 160mH air core and 4.700uF lytic and 50uF film on the output.(ok I had most of it laying around from my previous test setup).

My memory seems to fail me, as my square wave also has some angle, but it's like the pic you posted. At the lowest freq. of interest to me, which is 30Hz, it still looks reasonable, and the sine looks near perfect.

I tried listenig using Fostex FE166e units in Abbey clones (96db/w), this setup went all the way, though the bass was better and the noise floor lower, from my diff. cascoded pair version.

Magura 🙂
 
davidallancole said:
Do you have a schematic of your differential, cascoded amp? Are you making a cascoded, diffential amp with the inductors loading the collectors of the differential amp?


No, I don't have a schematic of the current mutation of the diff. cascoded, inductor loaded amp. It is still under development, as I am experimenting with thermal control of the JFET's.

As this is a MOSFET based amp, the load is on the drain...

Take a look at the Zen v7 and Zen v9 articles, and you will see what I'm talking about.


Magura 🙂
 
Magura said:
Naah, 10 persons with interest in this was maybe an overestimation 😉 Though I still wonder where Fuling is hiding....this is right up his alley!

flg [/i] [B]How about circlotron or whomever too... [/B][/QUOTE] I just found this thread today. :) Woohoo! [QUOTE][i]Originally posted by Fuling said:
There´s a thread somewhere on this forum titled "My first ever class A amp" (or something) where member Circlotron describes his massive L-loaded follower amp. He also shows how to make chokes using cores from old MOTs.

Here it is:
click
 
As regards the frequency response of the amp this thread is all about, seeing the load is in the drain circuit, and especially seeing it is a cascode circuit, the output impedance will be very high. It is pretty much a current source so the output voltage is completely at the mercy of the load impedance. If that impedance changes with frequency then so will the voltage...

The output impedance will be almost completely under the control of the amount of negative feedback.

Someone mentioned putting a low value resistor across the choke to prevent ringing. I've got a 10R 2W + 100nF in series in mine.

Lastly, if the load was across the choke instead of across the mosfets then there would (probably) be no switch-on bump and also you could use a lower voltage coupling cap.
 
Hi!

One time Fuling asked this, but nobody answered yet:

Also, there must be a way to determine the minimum inductance needed to get the desired frequency response. A ratio between choke reactance and load impedance at 20 Hz or something like that. Please share with me if anyone knows this!

Anyway, is there any literaure of Choke loaded amp designing??

Greets:

Tyimo
 
The large choke in the class A were already wound and I only reduced the gap to get a higher inductance. They are not impregnated at all. Neither were the ones I made out of microwave oven transformers. I didn't actually do anything with those ones - just made them and looked at them.
 
Circlotron said:
Hey! I just discovered this thread and then straight away it comes to a dead stop. :bawling:

Well, I'm glad your not blaming me :xeye:
I've been a little busy with some racing and other interests. I have played with the gap on my inductor core to try to raise the inductance without promoting to much lower saturation. I need to try a little more gap and see how that performs??? I have also been playing with R loading and different Iq's to examine the charateristics of Voltage gain, as in VAS, or preamp, or headphone amp. I'm also going to try a Pathos style, L loaded EF amp. It will be interesting to see the performance with EF vs the cascoded JFET gain stage loading???
😀
 
Tyimo said:
Magura!

Would it be possible to use Led bias for the Mosfet? (irfp240)

BTW: How do you like your amp???? Did you campared with a "stock" ZV9?

Greets:

Tyimo


Why would you use LED bias ( I assume you mean LED ref. CCS)?

This is an easy question to answer, cause I don't like the upper end from amps with the aleph style active CCS. The bottom end is about the same with for both of them.

Magura 🙂
 
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