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Old 19th March 2011, 06:47 PM   #1
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Default No NFB Headphone/Pre Amp

This is a modified Follower-99 based schematics, with the front amplification stage (Ku=11) and output impedance 1,5 Ohms. Almost perfect reproduce 500kHz square wave signal, time delay between input and output sine signal is 34ns (0,034us).
Output capacitor is made of 9pcsx100uFx63V Elna Silmic II + 15uFx400V Solen Polypropylene cap.
Separate shunt power supply is used for the front stage.
Signal pictures (input and output signals) are 200kHz, 500kHz , 1MHz square wave, and 1MHz sine wave.
Attached Images
File Type: jpg Schem Headphone Flwr.JPG (115.2 KB, 1225 views)
File Type: jpg prototype.jpg (127.1 KB, 1112 views)
File Type: jpg 200kHz_res.JPG (94.1 KB, 931 views)
File Type: jpg 500kHz_res.JPG (90.3 KB, 817 views)
File Type: jpg 1MHz_res.JPG (106.7 KB, 758 views)
File Type: jpg 1MHz_Sine_res.JPG (127.3 KB, 65 views)

Last edited by VladimirK; 19th March 2011 at 06:51 PM.
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Old 19th March 2011, 07:13 PM   #2
GoranB is offline GoranB  Poland
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Very impressive. Di You try it like line preamp also? How it sound?
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Old 20th March 2011, 05:59 AM   #3
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Quote:
Originally Posted by GoranB View Post
Very impressive. Di You try it like line preamp also? How it sound?
I have not make listening still, plan to do it with my Sennheiser HD595 headphones, although this model is not probably a high-end one.
It should also good serve as a preamp, with more than 20dB voltage amplification and 50V peak-to-peak undistorted voltage swing, with 1,5Ohms output impedance it is capable to drive any "difficult" power amp or output stage.
More definitely, after testing of this version, I plan to extend it to an integrated class A amplifier, by removing output capacitors and adding an output stage, based on 2SK1529 matched transistors, similar to the present second stage.
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Old 20th March 2011, 07:25 AM   #4
h_a is offline h_a  Europe
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Nice little radio amp you have here

By the way, from a short look at your schematic it appears the ground-symbols are not where they belong to.

It's not eco-friendly to short +60V to ground

Hannes
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Old 20th March 2011, 07:38 AM   #5
GoranB is offline GoranB  Poland
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Quote:
Originally Posted by h_a View Post
Nice little radio amp you have here

By the way, from a short look at your schematic it appears the ground-symbols are not where they belong to.

It's not eco-friendly to short +60V to ground

Hannes

All is fine with ground simbols here.
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Old 20th March 2011, 07:51 AM   #6
GoranB is offline GoranB  Poland
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Quote:
Originally Posted by VladimirK View Post
More definitely, after testing of this version, I plan to extend it to an integrated class A amplifier, by removing output capacitors and adding an output stage, based on 2SK1529 matched transistors, similar to the present second stage.
So it should be an integrated SE amplifier. Im very interested how it will sound. Im using a tube preamp to drive My Follower99, (little tired of that sound).
So, according You, this preamp should work well as a gain stage for PF99 also. I would like to build this preamp and see how it sound. Do You have any plans for modifications or further improvements?
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Old 20th March 2011, 08:35 AM   #7
h_a is offline h_a  Europe
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Look at input at the left side; upper input point is connected to ground, whereas same connection goes to +60V at the right side.

Lower input should be grounded; same as the source of VT2.

Hannes
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Old 20th March 2011, 08:54 AM   #8
GoranB is offline GoranB  Poland
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Quote:
Originally Posted by h_a View Post
Look at input at the left side; upper input point is connected to ground, whereas same connection goes to +60V at the right side.

Lower input should be grounded; same as the source of VT2.

Hannes
Yes I can see it, its a ground of input signal, output and chassie. Its nothing wrong to use that kind of aproach.



schematic.info : Power Follower 99
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Old 20th March 2011, 09:37 AM   #9
Bonsai is offline Bonsai  Taiwan
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Why are you avoiding feedback?
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Amplifier Design and Construction for MUSIC! http://hifisonix.com/
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Old 20th March 2011, 09:48 AM   #10
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Quote:
Originally Posted by GoranB View Post
Its nothing wrong to use that kind of aproach.



schematic.info : Power Follower 99
Yes amp it is possible deign a workable amp with negative cathodes and grounded "B+" (very strange approach however).

But ground is 0V and should be marked 0V not +60V since its misleading. Above schematics should be corrected with appropriate voltages accordingly.
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