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Adjustable Ultra Linear Linestage

Posted Today at 05:48 AM by ballpencil
Updated Today at 08:06 AM by ballpencil

This circuit is to fulfill my curiosity of hearing the sonic differences between pentode, ultra-linear and triode gain stage. As with any line stage, this circuit can also be the input part of a power amplifier. I'm considering a single ended amplifier where both the input and output stages have adjustable ultralinear percentage.. I'll show the output stage design on another post.

Anyway, i'm not sure there will be an audible difference between each mode other than gain.. but until i actually build this circuit, i can't really be sure.
Click the image to open in full size.

The idea is to use a pot to replace R5+R6. Dual 250K linear pot should do for both channel. You then adjust the screen feedback percentage by adjusting the ratio between R5 and R6. Here's how you obtain each mode:
1. Pentode mode is by making R5 = 200k and R6 = 0R. This will keep the screen grid at at fixed voltage regardless of plate swing.
2. Triode mode is...
Attached Files
File Type: asc Ultra Linear Linestage.asc (3.6 KB, 3 views)
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Super Triode Cascode SRPP Hybrid Amplifier

Posted Yesterday at 06:04 PM by ballpencil
Updated Today at 03:13 AM by ballpencil

Such mouthful blog title.. The idea is nothing new: to get the so-called "tube sound" from a hybrid amp. Tube sound for me comes from these two factors:
1. Triode-like linearity
2. Low to moderate damping factor
Personally, i believe number two is the main reason for tube sound. Any solid state amplifier manipulated to get a damping factor of around 1-2, instead of the typical SS amp DF that falls into the tens to hundreds, will sound like a tube amp. This is because with such low damping factor, the amp ceases to ignore the speaker impedance curve and start to become less of a voltage source and more of a current source where the bumps of speaker impedance curve will affect the amp's output.

Without further ado.. here it is:
Click the image to open in full size.

Some notes:
1. Ignore the transistor and MOSFET type. I chose them because that's what i have in LTSpice. The small signal BJT can use BC547 for...
Attached Thumbnails
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Name:	Super Triode Cascode SRPP Hybrid Amplifier_2.jpg
Views:	5
Size:	63.9 KB
ID:	1978  
Attached Files
File Type: asc SuperTriode Inverted Cascode SRPP_v5.asc (4.8 KB, 3 views)
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Posted in Uncategorized
Views 44 Comments 0 ballpencil is offline


Posted Yesterday at 03:25 PM by ballpencil
Updated Yesterday at 03:51 PM by ballpencil

I joined on Nov 2013 and that's pretty much when i started this hobby. Maybe "restarted" is a better term as i played with diy amps, tin and soldering iron back when in junior high but somehow stopped. That being said, it should be obvious that i am just a beginner and with that:
1. There will be mistakes/misinformation. Feel free to correct me. It will be much appreciated.
2. There is no guarantee any schematic shown works in real life, unless mentioned otherwise. Basically once LTSpice shows that it works, i'm 80-90% sure it should work in real life.
3. There will be updates and revisions as i learn more, hopefully with your help!
4. There will be language barrier. English is not my first language so bear with me!

Click the image to open in full size.
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Views 13 Comments 0 ballpencil is offline
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