Have you tried the ART SLA-1 amp yet?

d911,
I just visited your website, and would like to ask a question about your reference upgrade. As I understand it, it includes your standard mods, plus dual mono attenuators to replace the stock detented potentiometers. Are these Shallco based attenuators a ladder design or series design?

Thanks in advance,

Pm: You forgot about the best sounding attenuator type i.e. the "shunt" method. This places only one resistor and far less solder joints / points of contact in the signal path at any given time. Obviously, this results in the shortest signal path possible. Ric from EVS came up with this approach and several manufacturers have adopted it. Sean
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Sean,

I believe we simply has a difference over nomenclature. By ladder I'm referring to an attenuatior which switches both a single series resistor and a single shunt resistor for each attenuation level. This has a number of benefits in that it minimizes the total number of contacts through which the audio signal passes. It also requires a doubling of the poles/decks used in each attenuator. It also has the benefit of of choosing either a constant input or output impedance, but not both. The ultimate attenuator would be a T configuation which offer both constant input and output impedance.
If I understand you correctly, the shunt configuration you are referring to is a single series resistor and and a variable series shunt configuration, with either a switched series of resistor via a switch or a potentiometer. This offers neither this the constant input impedance of a classic series attenuation. Regardless, I would not dispute that the shunt configuration you suggest is not the 'best' configuration for a given price, and that the the L(adder) or T configuration offers insuffient benefit considering their inherent incremental costs. The SLA purchaser also has the option (given the assumption that the input to the existing pots are driven by an opamp of sufficient drive capabilities), of adding/changing a series resistor and configuring the pots that are there as a variable shunt element. For others who aren't familiar with this, please look at the following thread on diyaudio.com -
http://www.diyaudio.com/forums/showthread.php?s=cc0a06ce413d87f170148c94b6919c22&threadid=2608

If indeed, Mr. Nance is offering a shunt or ladder attenuator, is he providing those same 42 levels of attenuation? Given the cost of Shallco switches, he is either compromising on the type and/or the granularity of the attenuators. I personally, find a attenuator with less than 40 positionss unusable, but many others are content with 12-24 positions.

This would all be moot, if d911 hadn't posted on his site -
"These attenuators are the very best I know how to design and make use of Roderstein MKII resistors".

Notice he did not add - "within the constraints of cost/profit."

If the attenuators are not L or T configuration, I can only conclude that Mr. Nance is not a particularly competent engineer, specifically with regards to what is "...the very best I know how to design...", or that he continues his diengenuous ways....

From d911's website -

"This is the mod that has to be heard to be believed. It is quite extensive and employs new sheet metal, computer grade capacitors huge chokes, 20 amp breakers, Cardas binding posts and RCA's and many more additions."
http://www.dn-audio.com/id11.html

20 amp breaker? This as a replacement for the <=10amp fuse?
Its a truly wonderful idea iff'n you want your insurance company to tell you to take a leap (or look to those deep pockets of DNA Audio) when your house burns down.

Admittedly, a 20amp rocker breaker will replace the switch and existing fuse and offer substantially lower resitance under heavy current draw. But, in any and all countries electrical codes, this is the equivalent of putting a penny in as a replacement for a fuse. So, you put in a 20amp breaker on a device that would typically plugged into 15amp house circut. What exactly is the point?, other than a continuing display of engineering 'expertise', from someone who claims and Electrical Engineering degree?

No doubt, Mr. Nance will now change his website, but I've saved this page on my computer, so I will always have this 'gem'. Truly amazing......

Pmkap, you wouldn`t be related in any way to Occam over on Audiocircle would you? You two seem to talk the same talk, makes one wonder if you walk the same walk? I`ll be really curious to hear D911`s answers to inquiring questions, like your ever going to have Dandy Don do any modding for you. LMAO Regards, Robin