Friday, September 18, 2020

Doc Hoyer's garage door opener.

 It would seem that something as trivial as a garage door opener would never find its way to these pages but often it is the trivial that gives a glimpse into who a person really was.

This seemingly Rube Goldberg approach to automatically opening a garage door is a testament to the cleverness that was Dennis R. Hoyer.  I have no idea when this was constructed but given that they date back to 1926 my guess is going to Sears was not an acceptable option for Dennis.

The key to the operation is the drive mechanism and when I first looked at it I simply thought motor pulled the door open and the casters and gravity did the trick to lower the door with the motor providing some resistive force.  Upon further inspection I realized something different was going on since the casters were pointed in the wrong direction.

A closer look at the casters quickly refuted my first idea and for a second I though that the outside collar would spin around but when I realized that it was fixed it became clear that this simply operated like a ball screw on a CNC machine.

The motor turns the shaft and the casters on the collar were clamped tightly enough and set at a pitch to move the mechanism up or down at the desired rate based on motor speed.  There was a stop at full open and closed but no other safety procedures in place. According to his cousin Damian, if anything were accidentally left in-between the open and closed positions, the results were not pretty.

Most people would have simply driven to Sears but thats not how some of the truly great ones rolled.

Saturday, August 15, 2020

New Math


THERE! I said it, and I have been trying to say it for years.  Now I am going to use my junkie pulpit to try to explain it in simple terms.

The basic rule of transformers is that the transform the load by the turns ratio squared.  This simple function allows an 8Ω speaker to present a 3200Ω load to a 300B by using a transformer with a 20:1 step-down ratio.  This makes the world an easy place to live in and keeps everyone sane UNTIL someone then asks a poor transformer winder for a 10K:600 linestage transformer and a hole is ripped into the space-time continuum.  The conversation typically goes like this:

Customer:  I need an 10K:600 lineout.

Dave:  What will this be driving?

Customer: Interconnects and the input of the amplifier.

Dave:  Do the interconnects have a 600Ω resistor soldered across them?

Customer: No.

Dave:  Does the amp have a 600Ω input impedance?

Customer:  Of course not.

Dave:  What is the amplifier input impedance?

Customer:  I dunno... 100KΩ... 10KΩ worst case.

Dave:  Then what is the purpose of the 600Ω secondary designation?

Customer:  A 5KΩ:10KΩ transformer would have a 1:1.4 step up ratio and I want a 4:1 step-down ratio to lower the output impedance.

Dave:  A 4:1 transformer loaded with 10K will load the tube with 160kΩ

Customer:  No I want 10K.

Dave:  Head hits table.... nappy time.

This is the thing that urban legends are made of.  Everyone treats transformers as if they all are used to deliver power to a load.  This is perfect for the vacuum tube output transformer since the entire purpose of the transformer is to take the high voltage high impedance anode of a tube and get it to a low voltage low impedance to drive a loudspeaker.  Universally applying this to every audio transformer simply leads to confusion and needless conversations like the one above.  I will categorically state that the worst thing you can do to a transformer sonically is to load it.  In the case of the tube-speaker interface this loading is a necessary evil. In just about every other case in audio, transformers are used to deliver voltage to a high impedance and not current to a low impedance.

I do not begrudge the really smart guys from Bell Labs who did the telephone grid at 600-900Ω.  I tolerate the audio engineers who borrowed the 600Ω impedance as a standard so everything played well together when any mismatch could prevent people from properly hearing Duane Allman at the Fillmore East.  Using those numbers today in audio where systems are meticulously curated is just begging for confusion and mediocrity.  

So back the the 10K:600 step down transformer.  The one place in audio where this transformer will really will be loaded with 600Ω is when used to drive the Pultec LCR Riaa module.  For everything else in audio, the 10K:600 has little if any relationship other than being a convoluted way to say the device has roughly a 4:1 turns ratio.  You will find many who insist that the transformer needs to be terminated with its characteristic impedance in order to work as designed.  With vintage stuff, that is often the case, but that is simply due to the fact that it was designed with the intent to be loaded with 600Ω.  

Lets assume a 4:1 ratio transformer is needed.  I can come up with two very different designs based on its intended use.  99 times out of 100 the actual secondary load will be the grid of a tube so the transformer will be operating essentially unloaded.  Rather than use an incorrect device designed for a 600Ω load, why not simply use a device designed to operate into the actual load? 

The proper (according to me) way to specify a transformer that operates in the voltage realm is to state the source impedance, turns ratio and expected load and then the proper device can be wound.  Using this approach takes what many call a black art back to the nicely ordered oblate spheroid we live on.


Saturday, July 11, 2020


I have been playing with cartridges lately and one of the central points to any cartridge is the magnet.  I built this charging coil to re-magnetize the alnico magnet in a denon 103.

For s sense of scale here it is in relation to a charge coil for the magnet in a Sequerra ribbon.

This is a piece of more contemporary audio history.  JC built the charger for Dick Sequerra to charge the magnets for his ribbon drivers.

 The charger uses an ignitron (yes I insist on mercury even in my cartridges) to dump up to 14,000µf @ 600V into the charge coil.

While running it through its paces I was able to reverse the field in a N52 Neo magnet and in my attempt to see if I was reaching maximum charge this happened when I set the voltage to 400V and got a larger "POP" then expected.

The coil was 10 turns of #16 wire encased in JB weld.  The wire broke into several parts and the JB weld was nowhere to be found.   I have always heard stories how they would often vaporize the charge coil in big magnets.... never thought I would experience it first hand.

Wednesday, June 17, 2020

R.I.P. Art

It has been two months since Art left us and Janet reached out to me to help re-home the Step-Up that he was rotating through his system with his Denon 103.  This is the exact copper 1:15 H that he reviewed in Listening #176.   He preferred the sound of this copper unit compared to the identical silver version.  It has a 1:15 step-up ratio and is suited for cartridges with internal impedances from 20Ω to 50Ω.  The price at the time of review was $2400 and $1800 seems fair.  Payment will go to Janet Dudley directly and the SUT will ship from me with full support.  Physically this unit has been around the block so to speak but the function and sound is 101%.  Current pricing for this version in copper is $2700.  Pop me an email to discuss if this is a suitable fit for your system and by all means spread the word.  (SOLD)

a final reminder of Art's appreciation of the finer / furrier things in life

Tuesday, June 9, 2020

Doc Hoyer

Audio lost another of its treasures last week when Dennis R. Hoyer passed away in Milwaukee.  If you had a vintage transformer that needed help, Doc was the person to call.  On a recent trip to Milwaukee where I grew up I had the chance to visit his lab as 60+ years of his work was being dismantled.  As I was admiring his winder his cousin Damian put his license plate from 1980 in my hand and suddenly I got all choked up and truly knew who Dennis was.  

His files are a Who's Who of tube audio history

His winder was CNC controlled and built by him

I can't imagine driving around Milwaukee as a teenager seeing that bright yellow TESLA on the back of a Ford station wagon and not realizing I was behind someone truly ahead of his time.

Thursday, May 28, 2020

SUT Writeup.

I figured it was time to jot down some ideas on how step-up transformers are best applied to MC cartridges.  Hopefully the info at the link is easy to digest and not too much of a veiled ad.

Moving Coil Step-Up Transformer Design Considerations.

as a teaser here is the venerable peerless 4722 compared to a SUT that follows the practices I have laid out.  Please leave comments with any critiques.

Friday, May 22, 2020

New Stuff.

Sheltering at home has lead to a few new things in the intact arsenal.  First is a low ratio Speakerformer.  These units offer 1dB-6dB of attenuation in 1dB steps and the shunt resistor is changed with each setting to keep the impedance the crossover sees a constant 8Ω or 16Ω.  These will handle 20W of input and are designed for crossover frequencies of 100hz and above.

Next is something that fits in the middle ground between the Elmaformer and the basic autoformer modules.  Many customers have been asking for an alternative to the plastic shaft found on the entry level units without the cost of the Elma switched version. These are based on a 23 position Blore Edwards switch and offer a good compromise between cost and performance.

It should be noted that all of the autoformers are wound identically to each other and the only difference between the various versions are in switch type.

Sunday, May 17, 2020

From the Archives

The archives in this case being a dust covered cardboard box on a bottom shelf in the far corner of the 'Lab'.

The chassis work by Melissa & Doug represents the 'Early Davey Functionalist' era that predates the 'Drug thru the Hudson' look of the early 21st century.

It is a simple remote controlled 100K linear pot attached to some RCA plugs used explore loading options for MC cartridges.  At one point the concept piqued the interest of a well known Stereophile reviewer but upon borrowing the unit, he was terrified to plug it in to his system so into the archives it went.

The remote controlled pot was the handy work of of our good friend John Chapman and the concept evolved into the Opti-Load which replaces the pot with a relay controlled resistor matrix.

Tuesday, April 28, 2020

ERC in the NY Times

We love to see it when friends get the credit they deserve!  The NY Times did this nice piece on what Pete Hutchison is doing in London with his Electric Recording Co.

Pete also owns peace frog records for a slightly more contemporary vibe.

Sunday, April 19, 2020

Shameless Plug.

I updated the Intact SUT page to better represent the current state of affairs of what is going on inside the Intact and EM/IA MC Step-Ups.

Thursday, April 9, 2020

Random Says.....

this is where it gets crazy,  I just sent a 90 pound shipment to Ngan and the cost was $230 using fedex great rates.  This was nearly double the $130 I was quoted for my initial guess of 120 pounds so I started asking questions.  Turns out there is currently a price break at 110 pounds so adding 20 pounds of "weight" dropped the shipment cost to $118.  I asked if I could just claim 110 pounds and ship 90 and they replied my rate would be declined and I would be charged full price at 90 pounds which is like $1800.  This meany I needed to start throwing weight into the box and a pair of the 1dB speakerformers was part of that weight.  I figured some would say the fix was in since the units are already in Hong Kong so I hit up random again and Jason gets to see if they go to 11.

I must say that jason is one fine looking guy so shoot him a congrats if you see him floating around the interwebs and tell him to send me his address.

Thursday, April 2, 2020


Ok... poor play on words.  I just updated the Speakerformer page with some more fake news on why you need them.  I also added a "Rshunt" calculator and two new tapers.  One is a middling version that does -6 to -15.5dB and an "I don't know what I need" version that does from -1 to -20dB in 1dB steps.

Up for grabs is a pair of the 1dB per step versions pictured above just wash your hands for 20 seconds and leave a comment with your name or some sort of identification and will pic a winner in a week.

stay safe

Wednesday, March 25, 2020

The worst resistor ever?

I wound some 2KΩ copper wire resistors for DHT Rob a few years back and he used them to bias a 10.   He reached back out to me to do some 1300Ω to bias an AD1 @ 35ma.  

These got the slightly nicer package pictured above @ 25mm X 25mm. One of the biggest problems with the copper resistors is the value is not stable with temperature.  My solution to this for this case is to let them make some heat to stabilize them when in operation.  These units have a cold DCR of 1140Ω when cold and 1302Ω after an hour at 35ma.   Since these are intended for cathode bias it must be noted that the tube will run a bit hot initially before the temperature comes up and things stabilize.

The units are wound to be non-inductive and that results in a fair bit of parallel capacitance.  Since there will be a bypass cap in parallel with the resistor anyways, that is of little consequence.   In a crazy world one could use them unbypassed to compensate for loss of HF info elsewhere in the amplification chain like Kondo did with the Ongaku.

The other use for this idea is the loading of MC cartridges.  Since the proper way to load a cart is at the primary of the SUT, the values are typically much lower.  Knowing that it is also at a point where linearity of value across the audio band is a concern.  Here are some units that I wind onto an RCA plug for ease of termination and use.

These have much better bandwidth and are flat through the audio band.  Unlike the 1300Ω units which go capacitive at high frequencies, these go slightly inductive. 

The big question is why go to these insane lengths when there are plenty of off the shelf options are available?  Well if you look at it on the most basic level a resistor is simply a really crappy conductor. Given the extremes we go to for the quality of our signal wiring it isn't beyond reason to me that a longer length of a superior conductor with all of the baggage that it comes with may be better than an alloy specifically done to impede conductance.  Or you could just listen and damn if they don't sound good.


Wednesday, March 4, 2020

Sincere thank you for the write-up, Eddie!

We also had a lot of fun... glad you could make the trip....


Thursday, February 20, 2020

For Sale: very early Altec Lansing 604 in "furniture cabinet"


as Lisa knows.. I have a problem... I just cannot pass up beautiful and well-built items from the past... I love them... listen to them.. learn from them... but Joe warned me about this... long ago warned me... "Jackson, do not accumulate these things that belong in museums. You will be beholden to them." .. and how often is Joe Roberts wrong?  well, do not ask Joyce that question... but I am now far off-topic...

this beauty used to sit at one end of our dining room... the 16a sat at the other.... and it was what we listened to during family dinner.. or if one of us was sitting at the old farm table working on a project... but it has not been used in several years.. and that just is not right... so it is time to move it to a new home.. 

I love so many of the details on this... the pillows!!  and that wrinkle paint... sets my heart aflutter... 

the original label that is on the rear of the cabinet

one "oops"... from loading it... the veneer flaked up.. could be fixed by any woodworker, if desired... it is small.. and I tend to let old things just be.. 

but pretty clean for 1947.. that is seventy-three years old!

and look at that... 16a making a sneak appearance in the background... 

more pillows!

and then the driver in all of its minty details

"voice".. holdover from "field" days?  I dunno... 

20 Ohms.. Hollywood, CA

model 604... not 604B... or later... 

the driver has never been removed.. and I am not about to crack those screws.. 

N-2000-B crossover... and shockingly little dust for a 73 year-old..

original wiring.. they twisted and taped the wiring..

paper accordion surround... yep, early.. 

original cone (duh)

and that patination on te screws.. clearly untouched in a long time.. 

I think I am going to slowly just put things up on the blog... I will try not to make it a used hifi store, but focus on things that are blog worthy in themselves... 

oh, yeah.. I used to drive this directly from the headphone output on my phone... yes, seriously.. 

available unless marked sold.. 

US$4k, but accepting offers.. pickup in Rhinebeck is preferred, but I will drive this baby to a good home if needed.. and build a proper crate for shipping if I must..


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