Friday, September 4, 2015

CAF

Back and recovered from the Capital Audiofest.  This year we continued to bring things that were different and had no possible chance of selling.  This time the main difference was presentability.



I'll admit it looks a bit like a late 90's projection TV but there is a reason for this look.  Once you step around back you see the 'direct drive' power amplifier neatly tucked into the base.


 For this round it was Push Pull triode wired EL34's and while this isn't technically a "direct drive" amp,  I have not come up with a better term.  The two interesting Key points are the panels are biamped through discrete step up transformers loading the EL-34's and the crossover is in the amplifier circuit allowing the transformer direct connection to the panels.


The cabinets are Walnut with some bloodwood inlay and there are a few other tricks going on inside.


The two biggest comments at the show were along the lines of 'I thought quads didn't have any bass' and 'who says quads cannot go loud'.  It was mentioned on some of the forums that we only seemed to play things that showed off these two points and neglected to play the girl on a stool with a guitar that quads are known for.  Oh well... we can change that for RMAF.  Check out what Herb has to say at the link below.

Herb on the ESL


Saturday, August 1, 2015

Binaural

This is another one I haven't seen before.


  

This nicely pigmented album only appears to have two tracks but in reality it only has one since it is a binaural recording which requires two cartridges to play it.  This means you need a tonearm with two headshells,








The arm appears to work like a linear tracker and may have been the inspiration for the Garrard zero 100.  Here is a crude video showing it in action and some liner notes.

video




Monday, June 22, 2015

B is for Boron


Best taken in 4.4mm doses.


Sunday, May 31, 2015

High Current

Lets pretend I have a friend who is in need of some 2.5V @ 25A filament transformers.


It seems you can scour the world and not find an appropriate beast when in theory it is really a pretty simple job.

video

Simple... Just take an $18 100VA antek toroid and pull off the secondary.  Then all you need is 12 turns of #9 wire and you are done.  Since the final use needs to do 2.5V @ 25A * 2,   I was a bit concerned that the extra 25VA over would be problematic.  My first go was using some #10 wire I had which gave me 10 turns for an experiment.  The next problem was how does one draw 25A of current?  since I didn't have any 0.1 ohm 100W resistors I had to make due.  Luckily in my junk bin I had a 10 pound spool of #20 nichrome wire so a few inches should do it.  Well, that got really really hot really quickly but three strands in parallel about 8" each did the trick.  The #10 showed promise but I was a few turns short so off to the "home despot" I went to get some #10 stranded house wire for round 2.

The stranded wire was a failure.  First, the nichrome wire gets really hot and copper being a good conductor of heat gladly wicked the heat back into the transformer.  For kicks I was able to flow solder into the junction of the two and the first few inches of copper got so hot that they could cut styrofoam through the insulation.  In reality, I suspect the #10 would have been fine but since I was already pushing the VA rating I decided to go for #9.  Luckily I have a few spools of #12 and a twisted pair of 12's = a single 9.


The black flecs in on the core are nichrome flakes from the making of the video but I have run the unit for an entire day with both windings drawning 25A  and it didn't get hot enough to concern me.  As an added plus the voltage didn't change as the units reached full temperature under load.


It is a bit of a shame that the #10 didn't work since apart from the "home despot" green, I also have three different types of #10 Litz wire.  Just think of all of the Audiophool Hype you could come up with as you painstakingly strip 420 strands of #36 per connection.




Friday, May 22, 2015

Audio Intersections.



I had the fortune to visit a house a few hundred feet from this intersection and thought the names quite fitting for audio.  On this visit I saw a few interesting things the first being this amp.




 That Marantz meter is really telling of the specialness of this particular amp.  This was the prototype for the Marantz model 5.  Another really cool thing was this 7C.



 The collector would probably scoff at the labeling on the back but this was Sid Smith's 7C so I suspect an exception could be made.
  

It also represents a relatively low serial number which adds to its coolness.





Friday, May 15, 2015

Resist!

So Johhny tried some 450 ohm copper resistors under his 75TL's and liked what they did so he asked for some 600 ohm versions for under the RS242 driver.




For the earlier 450 ohm versions I did both inductive and non-inductive wound versions and the non-inductive versions were preferred.  The interesting side effect of the non-inductive winding technique is a  bit of shunt capacitance but since the cathode R is bypassed, I say the more the merrier.


Monday, April 20, 2015

Solder Bars

I was getting a bit low on bar solder for my leaded solder pot so off to the 'bay I went.  The first purchase was 12 pounds of Alpha-Solder.



Unfortunately upon getting it I quickly realized it was lead free with a small 3.5% bonus.


Back to the 'bay for some good old fashioned lead solder and without thinking I bough these.


Now I have a bar of 60-40 and a bar of 55-45 that I don't have the heart to melt down.


Oh well.... To the 'bay batman....