955 acorn tube headphone amplifier

It’s been a while since my last update and things are a mess right now….

Since we have prepared for the move, we have packed and moved some smaller items. My system has been dismantled and I even lent my amps to my friend as he tries them out.

We were supposed to move house last July but just a week before moving in, something happened and we couldn’t move house. Fast forward today, we are still in the same place.. and it seems like we are still 6 months away from ready to move in.

Current system – reduced to computer ->discrete monica -> headphone amplifier

Anyway, life has to go on and I got the itch again.

As I have these cute little 955 acorn tubes, I just want to build something with it. So why not build a headphone amplifier? If 2 tubes are cool to look at, how about 4? How about a push pull headphone amplifier? I don’t think these are popular out there?

So I asked my friend Mr Ew to cast his magic again. He promptly wound me a permalloy 10k : 32 push pull output transformer. It comes in such a little package, I could hide them under the chassis, leaving only the tubes peeking out.

If you recall, the last amplifier I built was the 6688 headphone amplifier. It was a 2-chassis construction, with power supply in a separate chassis, connected via an umbilical cable. So why not reuse this? Since the B+ is about right too?

don’t I look good?

Since I built push pull amplifier with the Ultra Compact concept before this, why not try something different? So this time I used an input transformer as a phase splitter – Sowter 3575 ( 1:1 ct).

showing just one channel. power supply as of the 6688 headphone amplifier

The construction is pretty clean this time as I managed to isolate the grounds at the input side. The input “ground” side of the Sowter is tied to its shield, and not connected to the “ground” side at the output, as shown in above schematic. Obviously, if you build such an amplifier and it hums like hell, you may need to connect both “ground” sides together.

proud of my rat’s nest wiring!

Okay, okay, how’s the sound?

Oh my, none of that “vagueness” or “fog” of a push pull amplifier. From what I know, that could be attributed to that horrible phase splitting circuitry used.

This fell’s very quiet, very detailed, very musical.

It has none of those irritating features that drives one to stop listening

It has those attributes that make you want to listen more.

Guess what I’m saying is, I don’t hear much of the sins of omission nor addition. If this makes sense…

I’m listening via Spotify these days and even with such “non-audiophile enough resolution”, I’m perfectly happy. Yeah, it could be because of my discrete monica, or it could be that this amplifier isn’t adding hash/rubbish/junk.

We audiophiles sometimes can be quite a pain in the ass, and want to nitpick on just about anything.

If “Spotify -> discrete monica -> 955 push pull headphone amplifier -> headphones” can make one happy and concentrate on the music, what more can one ask for?

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