2. amps-preamps
  3. 1173351750

Break in period

I have just acquired the Conrad Johnson CT5 preamp and CJ LP70S power amp. Would appreciate inputs /advice of fellow a'goners regd optimal break in period and is the break in period dependent on playback volume or amount of
gain. The reason I ask is coz a Stereophile review of the CT5(July 2006 ?)mentioned that the preamp was left in continous play mode for a week, that translates to 150 hrs.Given that i listen max 2hrs/day and more on weekends, that translates to a break in period of nearly 2 1/2 months !!
Have huge issues leaving the system running 24/7 coz of erratic power supply and neighbour's privacy etc
Would appreciate any/all advice
Cheers
sunnyboy1956

Showing 5 responses by gregm

gregm
3,411 posts
 
Jeff sez
If the results are audible, shouldn't they also be measurable
Should be, I guess. BUT what would one measure? Once measured a diy phono equaliser with a friend (for other purposes) at ~2month intervals with a scope. Zilch.

Note however, that the caps had already been "treated" with a variac before they were mounted. Likewise with critical path resistors (components are important for the equalisation curve). Also, first measurement was well after first power up (a couple of hours or so).
gregm
3,411 posts
 
Pauly
Did you measure distortion levels and how do you know it is harmonic distortions
Actually there is -or used to be- some ATC measurements available s/where re, linear & nonlinear distortion on their models. Unfortunately haven't found it-sorry. I do remember seeing this though... if you're actually interested.
gregm
3,411 posts
 
Shadorne -- that mustn't be what I'm referring to. I distinctly remember them comparing distortion figures (3%) I think between two ATC models at specific spl levels...Oh well.

the higher output impedance of a tube (with ouput transformer) coupled with a typical bumpy speaker load. This results in a different frequency response/presentation from a tube/speaker combo versus an SS/Speaker combo
Normally, yes. But one thing that is important in a spkr -- and one thing we do NOT know -- is the strength of each driver's magnet. A very "strong" driver (e.g. a Lowther, etc) paired with a SS will be overdamped and sound like Donald Duck unless tamed (i.e. at xover level). A hi output impedance paired to a very strong (i.e. electrically damped) driver may provide the optimum marriage...
gregm
3,411 posts
 
Drubin notes
the system was on, playing in the background. At one point during the evening, I began to notice extraordinary detail and elegance from the system. My brother noticed it as well. The amp sounded great!
Well, yes. The circuit will stabilise under normal operating conditions, as you yourself noted earlier
it's that individual circuit components (resistors, capacitors, wire perhaps) undergo some change during the initial hours of their use
However, you go on to note
This may not show in measurements but I think most of us agree that measurements alone do not the whole story tell
Not the whole story -- but some of it. Measuring the complete circuit during operation (DON'T really do this, for goodness sake :)-- I mention this only in discussion context) you may discover things... One easy component to track down is a phono equaliser. The components' tolerances can affect the de-emphasis; many of the ("good")resistors used are +/- 5% i.e. 10% total rated shift...
gregm
3,411 posts
 
If I may "explore" Shadorne's comments above, we may find similarity rather than disagreement:
My point was that audio engineers [would aim to] design things to sound consistent and significant audible changes ascribed to [any number of parametres, one of which is] lengthy burn-ins (after months of listening) (...)[may] not be very desirable [since it could result in performance variations between otherwise identical pieces of equipment]
.
I wouldn;t think anyone is doubting that -- if I catch Shadorne's drift.

The fact that there IS some change in performance is all the more interesting.

A note about wires, referred to by Atma above: one of the most boringly annoying such situations must be changing the tonearm wire. Once changed "for the better" the new wire often takes an PIA time to "settle"/burn/break or whatever it is or takes for it to sound normal/itself...
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