A/V: Audio stuffs

Audio: Vintage and modern

These page will cover the Audio, and P.A. parts of my audio hobby.

Soo… I like music and audio equipment. I have rather a large amount of it, there’s at least one sound system in every room. And outside too. Much of it is vintage, although the home theater (more) is a mix of a modern Atmos preamp driving a bunch of Crown D-75 power amps.


Here’s my retro and obsolete audio media players and decoders rack.

Retro and obsolete media players

From top to bottom:

  • On top, the classic Technics 1210 MK5 turntable. Modified to play 78’s as well as microgroove moderns
  • Furman Power conditioner – the newest thing here
  • Pioneer 707 7″ reel to reel deck
  • Tascam Patch bay
  • dbx type 1 and 2 decoders. The lower one also handles dbx encoded discs
  • NIKKO BETA 30 preamp
  • Panasonic SV-3700 pro studio DAT deck
  • TEAC R400x cassette deck – one of the few decks that has Dolby B, C *and* dbx NR
  • Pioneer DV-563A multiregion DVD player, plays SACD discs
  • SAE 5000A pop and tick remover & flat phono preamp
  • dbx 3BX dynamic range expander
  • dbx 120 subharmonic synthesizer

And other miscellaneous:

My Turntables: https://farmedia.com/my-turntables/

The first affordable CD player, also portable! https://farmedia.com/sony-d5-cd-player/

That little tiny amp…  Facmogu F900 Amp

The tube line buffer investigation: Tube Audio Buffers

[ST-70]
Quick project: Why did the fuse blow in my vintage Dynaco ST-70?
(If you’re not familiar with Dynaco, you should be:  Dynaco wikipedia article)

Here’s what my rebuilt  Dynaco ST-70 looks like:

Dynaco ST-70, top side
Dynaco ST-70, under chassis

Tube amps have, well, tubes. And they wear out, eventually. This amps rectifier tube died and caused an over-current condition, presto fuse blows. Checked the other tubes and the bias current, all looks good now.

Fun fact: You can easily get more power (more then double)  if you run an 2 channel amp as mono in a bridged “push-pull” config.

The advantages are:
– Double the output power. Can more than double depending on amp design.
– Quieter, the hum and noise tend to null out.

The down sides are:
– You will need two ST-70 amps for stereo.
– The channels need to be closely matched for gain and freq response, not always the case with old tube amps.
– Halves the damping factor, meaning your bass may get flabby.
– You must invert the phase of 1 channel. (That’s 180 degrees out of phase if you’re following along at home.)

To play with this, hook a 8 ohm speaker across the 4 ohm taps and drive the inputs with a balanced “pro level” signal.  Volume trims (not included on the original dyna design) will let you exactly balance the gains for this trick. I’m doing this for my center channel amp in my home theater setup, it sounds amazing.

And now, on to the next thing!


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