No NFB Headphone/Pre Amp

[VladimirK]

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.

[GoranB]

Very impressive. Di You try it like line preamp also? How it sound?

[VladimirK]

Originally Posted by GoranB

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.

[h_a]

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

[GoranB]

Originally Posted by h_a

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.

[GoranB]

Originally Posted by VladimirK

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?

[h_a]

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

[GoranB]

Originally Posted by h_a

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

[Bonsai]

Why are you avoiding feedback?

[suntechnik]

Originally Posted by GoranB

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.