300b lovers

The HK Citation gear was the most razor flat sounding, and the Fisher receivers were actually quite good.   The Scott gear was also quite good, and my favorite small integrateds were the Sherwoods.   Their little EL84 based integrated was quite good if rebuilt.  None of these are as good as the really good modern tube amps, but only the really good gear.  The transformers in the much of the old gear were really good, but they didn't have the quality signal path parts we have today.  Also, they had all sorts of features that robbed signal quality, like miles of wire in the signal path to support things like stereo/mono and phase reverse switches, and of course tone control circuitry.   Very long signal paths in many of the old integrated amps and preamps.

The Dynaco ST 70 had good transformers, but the driver section was barely adequate and if you replace it with one of the more modern boards, especially the all octal tube ones, the amp is greatly improved.  The small chassis limited the quality of the power supply you could fit in there though.  Still, if modded, the ST70 is a great little amp for the money.

Playlist

Here’s what I’ve been listening to for the past year. Probably zero percent overlap with Don Sachs, and only 10% overlap with the folks at Spatial. It’s a mix of dense heavily-produced rock, London Sound, and German techno.

Joywave: Traveling At The Speed of Light (7:34 version)

Joywave: Smokestacks

Big Data: Unglued

Big Data: Put Me to Work

Disclosure: Help Me Lose My Mind (featuring London Grammar)

Soul II Soul: Keep On Movin’ (demo quality)

Elderbrook: Inner Light

Elderbrook: I’ll Find My Way to You

Ulrich Schnauss: Far Away Trains Passing By (whole album)

Phosphorescent: Song for Zula

Tears for Fears: Elemental

Tears for Fears: Woman In Chains (demo quality)

Preferred Listening Format:

* Shadow Vector, Surround Master, or DTS Surround system

* Open-back planar headphones

* DHT triode system

Probably half these songs would get me thrown out of most hifi show demo rooms ... certainly the first four, for sure. They’re all really emotionally intense, which is why I listen to music. Both "Keep On Movin’ " and "Woman In Chains" have an unworldly beauty unlike anything else, and Ulrich Schnauss’ "Between Us and Them" is quite a sonic excursion.

I’ve been lucky enough to have several experiences that changed my life ... when I was ten years old and heard stereo for the first time, and heard a live performance of The Messiah the same year ... fifteen years later, hearing Shadow Vector quadraphonic for the first time ... twenty years later, hearing the Ongaku and Reichert DHT amplifiers on my new Ariel speakers ... and ten years after that, my own Karna amplifier. Profound, deeply moving, out-of-body experiences.

That’s why I find audiophile discussions of "accuracy" to miss the point. I don’t listen to music to sip a single-malt whiskey, smoke a Cuban cigar, scratch my chin, mark up a twenty-point checklist, and write long reflective essays about this or that subjective aspect of the sound. That’s silly. What’s the point? Who cares what XYZ critic thinks?

It either gets me flying or it doesn’t ... and if it does, how high?

 

From this distance, I wonder about circuit stability.

@lynn_olson They were quite stable and reliable. But the circuit is carefully designed around some serious issues with phase margin, which is why you really don’t want to try any serious mods other than updated coupling caps unless you do the math and think it thru.

The Dynaco ST 70 had good transformers, but the driver section was barely adequate and if you replace it with one of the more modern boards, especially the all octal tube ones, the amp is greatly improved. The small chassis limited the quality of the power supply you could fit in there though.

@donsachs The real weakness of the ST-70 is the rectifier. Its not got enough current and so is the most likely tube to fail in the amp. If you replace it with solid state the B+ will be too high. It is possible to use dual rectifiers but you have to replace the power transformer to do so. Triode Electronics of Chicago makes a power transformer that drops into place. You can use the filter can location for the other rectifier; the power supply caps can be installed beneath the chassis.

There are adapter sockets on ebay that allow you to run a 6GH8 in lieu of the 7199; that gets you a far more common tube that also runs the amp with a bit lower distortion.

I’ve said it before and I’ll say it again. This is such a great thread.

Oh! And hi @eddie138 ! Nice of you to drop in!

@atmasphere Actually, I have rebuilt a few ST-70.   I agree, the rectifier is inadequate, but so is the driver section, which is at clipping at or just before the output section clips.   I have heard a couple of drop in boards and the octal version was by far the best.  Much better amp with 6sn7 input tube and 6sn7 drivers.   Still, the small case keeps you from installing a really nice C-L-C supply built with only film caps rather than lytics.  When modded it is a cute little amp, but hardly worth the trouble compared to other designs in my book.  I recall another vintage amp or two that used 6GH8 or similar for driver section, probably Scott, but too long ago.  Yes, we re-wired the sockets to take more common variants of the triode/pentode combo tubes.  They are all nice little amps, but not in the same universe as the topologies we are discussing in this thread.   However, would make nice little systems though with good speakers.  

I recall a Fisher flagship el34 amp that was really rare that actually sounded quite good when restored as well.  So long ago I forget all the model numbers!  When I was doing all the vintage work I could probably have rattled off the model...