Al also experiences forces with mag fields - ever see the jumping ring eddy current loop demo?
I think most of the claims of steel causing audio distortion are over hyped - not really a big effect if you twist leads for current loop minimization for other very good reasons
Audio Precision uses steel chassis - Hofer had to add a thin Al sheet to the inside of the steel cover right over the audio oscillator circuit to get rid of ppm distortion from the steel hysteresis
I think most of the claims of steel causing audio distortion are over hyped - not really a big effect if you twist leads for current loop minimization for other very good reasons
Audio Precision uses steel chassis - Hofer had to add a thin Al sheet to the inside of the steel cover right over the audio oscillator circuit to get rid of ppm distortion from the steel hysteresis
No. A transformer will induce currents into either type of chassis, but more into aluminium because it has better conductivity. A transformer injects magnetic field into a steel chassis, which may then induce currents elsewhere.HiFiNutNut said:
You may be confusing safety ground with signal ground. Bad grounding will cause problems whatever chassis material is used. Good grounding will solve problems whatever chassis material is used.
To be more precise - They have not been able source (or design) aluminum chassis for the target price, and turned that into marketing crap.
Sad but true. I commented earlier with my recollection of a magazine article from a long time ago. My intention was to imply that the subject is always good for a discussion but there was no universal answer. Engineering is the art of compromise.
Agreed, but trying to avoid the wrong conclusion here. Better conductivity also means a better shorting effect - the chassis is a plate of some area, not a conductive 'coil' turn. It will therefore also dissipate whatever is induced without more ado. This reminds of the copper foil 'turn' round the outside of a power transformer including all of the steel legs. This dissipates whatever leakage magnetism there is with the effect of less induction in nearby electronics. Mounting a transformer directly or not on a chassis: I have never had any detrimental effect, even with 500VA power transformers bolted in contact with a chassis, but others may not have been so fortunate.
A steel chassis seem to generate potential differences between points on the chassis by the electromagnetic effect and depending on the power transformer used, affecting earthing at various points. I have never fully investigated, but have in the past just about always had hum problems with steel chasses, not so with alu chasses. This was mostly when using the chassis as convenient earth plane, but also when using wire star earthing or whatever other preferred way. (It was worse with drop-through power transformers.)
Yes, many products used and still use steel chasses with success; not saying it can't be done. Only as the saying goes: 'Once bitten, twice shy.' Also where alu welding techniques have been refined these days, I prefer alu for chassis material - enough other pit-falls!
Regarding the 'sound' of a chassis .. er .. no offense, but I cannot see much more than urban legend there. Obviously not some construction that wobbles up and down with every oompha, but other than that
The "Sound" of the Chassis
Several different possibilities here.
(1) Current movement through the chassis which affects signals within and without.
(1a) nonlinear aspects (reactances?) to the current movement (e.g., I think this is why Audio Precision used an inner aluminum layer above steel chassis to reduce oscillator distortion).
(2) Magnetic effects which generate (1,1a), or cause other magnetic effects causing (1,1a), and so on.
(3) Physical chassis vibrations, stimulated internally by vibrating transformers, alternating magnetic fields, etc., to the degree the vibrating chassis creates an audible sound.
(4) Physical chassis vibrations stimulated externally by external sounds such as that from speakers
(5) 3&4 above are concerned with direct sound radiation of the chassis. But vibrating chassis can also cause effects on specifically microphonic parts
(6) The effect of chassis vibration on disparate signal currents flowing through wires and devices causing them to have varying rather than constant unintended effects on each other. This is the kind of thing that causes degrees of audiophilia nervosa, but most likely has negligible effect.
It's always been my suspicion that first #3 and then #4 is the key thing that makes massively overbuilt equipment sound better. It has nothing to do with the electronic operation. And you may want to eliminate all the other coincidental thin metal resonators in the listening space also following the same reasoning. However, then some people add ringing metal balls and such to improve the sound. If you are building part of chassis out of wood, that may help damp vibrations, but then different woods have their own characteristic sounds, and so on. I'm with those who say thick aluminum or brass, and maple have the best characteristic sounds of their own.
(7) The sound you get when you knock on the equipment, a kind of feel good thing.
Several different possibilities here.
(1) Current movement through the chassis which affects signals within and without.
(1a) nonlinear aspects (reactances?) to the current movement (e.g., I think this is why Audio Precision used an inner aluminum layer above steel chassis to reduce oscillator distortion).
(2) Magnetic effects which generate (1,1a), or cause other magnetic effects causing (1,1a), and so on.
(3) Physical chassis vibrations, stimulated internally by vibrating transformers, alternating magnetic fields, etc., to the degree the vibrating chassis creates an audible sound.
(4) Physical chassis vibrations stimulated externally by external sounds such as that from speakers
(5) 3&4 above are concerned with direct sound radiation of the chassis. But vibrating chassis can also cause effects on specifically microphonic parts
(6) The effect of chassis vibration on disparate signal currents flowing through wires and devices causing them to have varying rather than constant unintended effects on each other. This is the kind of thing that causes degrees of audiophilia nervosa, but most likely has negligible effect.
It's always been my suspicion that first #3 and then #4 is the key thing that makes massively overbuilt equipment sound better. It has nothing to do with the electronic operation. And you may want to eliminate all the other coincidental thin metal resonators in the listening space also following the same reasoning. However, then some people add ringing metal balls and such to improve the sound. If you are building part of chassis out of wood, that may help damp vibrations, but then different woods have their own characteristic sounds, and so on. I'm with those who say thick aluminum or brass, and maple have the best characteristic sounds of their own.
(7) The sound you get when you knock on the equipment, a kind of feel good thing.
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I was lucky enough to grab a 2x3 foot piece of .050" thick titanium sheet from being scrapped. It will most likely have to be machined professionally but when polished will make one heck of an amp chassis
They build military aircraft structural members and control surfaces out of titanium so that new tube amp with the titanium chassis will fit right it next to the heads up display.
in my case i use a central buss wire #14 or #12 copper wire where all ground connections go, in one place......
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hello,
Once i start changing the power supply caps i will check how everything is connected. If i remember well there are two tagstrips connected to the chassis to hold the resistors used in the power supply way from the chassis. one 10000µF cap is connected to the chassis using the bolt attaching the tagstrip to the chassis. The other cap is uses the other tagstrip.
These are the caps used for the output stage.
The caps used for the input and driver stage? I am not sure where they are connected.
The centre tap of the transformer '' feeding '' the output stage uses one of the tagstrips.
Will have to take a closer look when i have more spare time.
Greetings, Eduard
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not sure if you are reffering to my amp, but those hookup wires are gage #22 stranded wires that are stiff enough to form like they were solid wires...
Hi Eduard, a copper ground buss,using the #14 or #12 solid copper is an old tactic used extensively in the past...it is still relevant today..
Hi Eduard, a sopper ground buss is an old techic used extensively in the past...it is still relevant today..
I will have to spend some time to find out how things are connected.
If i am right the centre tap from the transformer is connected by a kind of ''rivet '' together with one of the poles of the big cap. The pole of the other cap that needs to be joined with the centre tap and the pole of the other cap that is allready connected to the centre tap. So the chassis is used to connect the negative pole of one cap to the positive one of the other.
This could be improved if i will change the caps.
I dont know how the caps of the other power supplies in this amp are connected.
It looks likes there are several locations where ground is connected to the chassis.
Greetings, Ed
P.s If i will change the simple cap( 10000µF for each rail) supply to a CLC with 10000µF 200mH 0,85 ohm choke and 2*10000 µF will i need to change the diodes. ( maybe reduce the cap before the choke in value?)
I will have to spend some time to find out how things are connected.
If i am right the centre tap from the transformer is connected by a kind of ''rivet '' together with one of the poles of the big cap. The pole of the other cap that needs to be joined with the centre tap and the pole of the other cap that is allready connected to the centre tap. So the chassis is used to connect the negative pole of one cap to the positive one of the other.
This could be improved if i will change the caps.
I dont know how the caps of the other power supplies in this amp are connected.
It looks likes there are several locations where ground is connected to the chassis.
Greetings, Ed
P.s If i will change the simple cap( 10000µF for each rail) supply to a CLC with 10000µF 200mH 0,85 ohm choke and 2*10000 µF will i need to change the diodes. ( maybe reduce the cap before the choke in value?)
I am looking at a Hammond aluminum 15"x7"x3" and a 16"x8"x3" steel chassis. The aluminum is 1.3mm thick and the steel is 20 gauge. My only concern is that the total weight of my components (over 15 pounds) may result in sagging or deforming of the chassis. I have no concept of strength between aluminum and steel. Could somebody advise which of these cases is stronger? I think I might prefer the aluminum, but not if it prone to said issues.
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