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Solid state device rolling?


tube fanatic

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I hope I'm allowed to enter this neighborhood!  Since it's well known that some tube folks like to roll tubes, I started wondering whether the same took place in the solid state community (in my repair work I never gave it a thought).  Here's a thread in which a guy brought up the subject:

https://www.reddit.com/r/audiophile/comments/27yl0r/can_i_transistor_roll_the_way_i_tube_roll/

Is anyone on here doing that?  I would enjoy reading about your experiences in that area.

Maynard

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There is a difference between an LRU, an SRU, an FRU, and a piece part, like a resistor, capacitor, inductor, or other DIP device, etc. 

 

What you're talking about is definitely at least at the FRU level, but I'd imagine that most SS amplifier and preamplifier manufacturers consider these devices to be piece parts, not FRUs.  In other words, they didn't design the unit to be "maintained" at the opamp level, but they can be repaired if they fail at a "field maintenance" (i.e., guys like you) or "depot" level (i.e., the manufacturer's facilities). 

 

The reason why many of these firms use sockets instead of soldered connections is that the heat required to solder opamps to a board can be single point failure sites due to heating of the opamp pins during assembly.  I'm pretty sure that "rolling opamps" will void the manufacturer's warranty, since the units were not designed for periodic maintenance--inside the boxes.  If you want to "fiddle around", then you risk losing the value of warranty and the value of the unit itself if you cause it to fail.

 

A tube amp, on the other hand, is actually designed for FRUs (tubes/valves) to be replaced upon failure, which is why the tubes are usually exposed or under an easily removable cover, and which happens a lot since the MTBF of tubes are orders of magnitude less than equivalent solid state devices, and the tubes themselves undergo degradation that is audible over time.  Hence the mentality of "rolling tubes". 

 

I don't believe that I've heard or read about graceful degradation of an opamp--properly used in a circuit within manufacturer's operating parameters.  Same thing for any other semiconductor device: basically, these device types either work or they stop working, requiring either depot (manufacturer's) repair or entire LRU replacement (buy a new amp). 

 

You're mixing maintenance concepts.

 

Chris

Edited by Chris A
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Most of the time you may find yourself in trouble if you try and change transistors or opamps in a typical piece.

 

Yes, there are parts that will work much better with a few other changes, the key thing is to understand that the few other changes are a must.

 

Unless you are following a tried-and-true mod, you will need the knowledge and test equipment to insure there are no problems.

 

You might also find that the layout of the circuit board will not work with your screaming-fast super-parts, and short of designing a new board you are done.

 

I've been there, and done that.

 

I have a list of mods for the earliest McIntosh solid state amps that mainly involve capacitors if anone wants to improve their MC2300/2100/2102/2505/250 or MC2205.2200/2125/2120/502. Send a message if interested.

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  • 9 months later...

I modified the pre-amplifier input section on the MC2105 to incorporate a BJT NPN current source on the LTP differential input.  The design on the bread-board measures a decent drop in second and third order HD at 1kHz.  It's really just the addition of a few components but would require a new PC board which isn't all that difficult to source in quantities these days.  The resistor only current sources are actually quite marginal and a source of distortion in the first generation McIntosh units.  If the input differential section gets it wrong, nothing can fix it.

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On ‎8‎/‎23‎/‎2015 at 8:52 AM, Schu said:

Ive often wondered what effect using aligator clips in the capacitor portion of the circuit would cause when swapping different caps in and out...

 

In my experience, temporary connections contribute to noise. The clip moves a smidge and the %THD change by 2 or 3X.  On the small signal side of the amplifier everything is a problem when it comes to measuring %THD.  Connections need to be soldered. 

 

The "trick" is to master the use of a good solder sucker.  I have a vacuum pump driven unit but find this low cost sucker the balls out champion when it comes to stripping a proto-board or factory unit down.  Quick and clean. 

 

I have a few of them.  Radio Shack sells them.

 

sucker_2.jpg

sucker_1.jpg

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I Have had great results rolling SS. I actually tried many of the name brands, wound up the SS nirvana in my Sansui BA-F1 and CA-F1. I also rolled speaker parts..  The volti full set up is hard to beat. 

 

But individual board mounted components, that is not a good idea unless you are an Electronics Engineer with tons of measurement equipments ~ about $40,000, and the skill to use it.... or if you have lots of money and a place to put the stuff that you let the magic blue smoke escape from!   LOL

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Just saying..."rolling" is not exactly how I do it...more like "lugging" out one unit and lugging in another...mid-1970's-era solid state is HEAVY...the more complex the item the heavier it is!  For example there is a HUGE weight difference between the (relatively light...for its time) H/K 430 and the H/K 900+!

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