Tiny Coils

I thought things were getting a bit out of control when I was seriously considering mounting a microscope on my lathe.  Never mind that I am attempting to keep 0.01mm precision and doing other silly things like spending $16 on a 0.2mm diameter cutoff wheel for a dremel.

Seems like 1997...

Dave is testing Sovtek 6B4G's and building push pull amps.... Dear god say it ain't so.

In his defense the DHT's are replacing triode wired EL-34's and the outputs are 49% nickel (soon to be 80%)

Big (ger) Amorphous.

The old "Big Amorphous" cores have been downsized.  They were perfect for a 10W from a 300B or a 75TL but the requests for 20W at gobs of current keep coming in.  Sure I can gang up multiple cores or add an offset winding but the winding window gets small quick. 

 

 

The new option takes up a 6" cube and stay tuned to see what gets built from them.

A nice small system.

Not everybody has all kinds of room to dedicate to audio and one of our friends put this together.

I really like the way things are laid out and the use of steel and wood for the rack.

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

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.

B is for Boron

Best taken in 4.4mm doses.

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.

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.

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.

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.

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....

New Toy

I always found it frustrating to be working with an automated limit of ~90Kz from my 192 sound card since the good stuff, particularly with SUT's always seems to happens above 100kHz. 

 

I have seen the Velleman pcsgu250 with its claims of Bode plots to 1mHz for some time and asked about experiences on a number of forums with no response.  I finally sent $150 to newegg last year and procured one.  Flash forward several months and i took some time to rewrite my excel macro's to import the data and I must say I am quite happy with the results.  Sure it is no Audio Precision but it is a million times better than manually entering 100 sets of coordinates per trace on the test bench.

Name that SRA.

I'd call it close enough to 92 degrees but the sound wasn't the greatest.  It was sounding really good until things abruptly went bad and a quick visual inspection explained the problem.

Note to self... hot glue and field coils do not play well together.

Hudson Valley hiking in March...

.

means hiking *on* the river...

as you know I moved to the Hudson Valley from Memphis before last winter... quite a weather shift... I heard from locals that last year was the coldest they could remember in decades.. "what winters used to be".. or "what winters are supposed to be"... it was cold... well, that was before this year came... we set a record in February - average temperature = 9 degrees Fahrenheit... not average low... average *temperature*.... whew... but you know what?  it is good for working.... and this past Friday when the sun came out, having long eclipsed forty hours in the shop, a few of us took off for a hike in the sun... it was wonderful...

we started off from the house.. hiked down Burget Creek... then onto the Hudson.. all the way down to Catskill Creek... and finally back to the Mill to finish up the day's work...

notice the crazy ice breaks.. the Hudson is tidal... and that makes for some really cool ice breaks...

obligatory HiFi Heroin photo:

peace,

me

finally got his 16-A....

... and Elmore James has never sounded better... 

initial placement

it is a Subaru thing

road trip!

yep... pile o' parts

random barn photo

final setup

repro 16a (better bends than any original I have seen)

original WE555's, single Coral tweeter

rebuilt amp (globe 50's), 416's bi-amped

shocking how good this sounds... you just sit there with your mouth agape... 

so much detail.. transients... and then you end up dancing!

*so* much fun....

peace,

me