True, but soon they'll be imported from China, available on late night TV; Just dial 1-800-ATOMIC "But wait, you also get..."chascode said:
Off topic, but a handy way to dispose of those projects that didn't quite live up to the expectations.
I found this NEMP generator on the web. It suggests 2 hours to set up. However its pretty intrusive and not small so really only for the specific tasks its meant for. There is also a lot on NEMP on the web including some interesting myths debunked (tube circuits are not immune and solid state stuff can be hardened pretty easily once the problems are understood).
Next Off Topic issue- I will do some extensive testing of MOV's in the next few weeks and post what I learn about the nature of them and how they decay. I will do the same if I can get some Transorbs (and Sidactors etc.) although the tests will be a little different. I have gas tubes and have used them extensively. they work, they have a high flashover point, one that is sensitive to risetime. Off, they are just small caps.
Back on topic- how much do all these noise issues from outside the box influence the sound? The Blowtorch was built into a solid block of aluminum. I have built preamps in similar blocks of Delrin w/ airtight seals on the cable entry points and the controls. All seemed to make a big difference. Or was I deluding myself to justify the hassle of getting Delrin machined? How much lower than the native noise floor of the system do we need to keep the external "disturbers"?
Next Off Topic issue- I will do some extensive testing of MOV's in the next few weeks and post what I learn about the nature of them and how they decay. I will do the same if I can get some Transorbs (and Sidactors etc.) although the tests will be a little different. I have gas tubes and have used them extensively. they work, they have a high flashover point, one that is sensitive to risetime. Off, they are just small caps.
Back on topic- how much do all these noise issues from outside the box influence the sound? The Blowtorch was built into a solid block of aluminum. I have built preamps in similar blocks of Delrin w/ airtight seals on the cable entry points and the controls. All seemed to make a big difference. Or was I deluding myself to justify the hassle of getting Delrin machined? How much lower than the native noise floor of the system do we need to keep the external "disturbers"?
1audio said:
don't know about you, my hearing is very narrow-band
20k noise bandwidth doesn't cut it for me.
It's pretty much impossible to tell. Almost all locations have EMI fields, some more, some less, they should not be allowed to influence the sound from your system.1audio said:
While aluminum doesn't block magnetic fields it does significantly attenuate AC fields due to eddy current losses. So a metal box represents reasonably priced insurance. If you have as much invested in your system as most audiophiles the cost of a metal box is low.
1audio said:
I would be curious as to the static field remaining in the Delrin box after machining and what effect it might have on the circuitry inside. I'd be surprised if you did measure it; mostly because its not on most peoples radar, and actually facinated if you did. Did the preamp have a unique sonic signature you could atribute to the enclosure? I know you were focusing on controlling the environment the circuit operated in but I can't help wondering...
Regards, Mike.
Terry Demol said:
Of course it doesn't always slip past every designer's radar. It is just that some are commercially driven to earn a living making products and protect their hard earned research and others like to share it for free on DIY forums for personal recognition and egocentric reasons.
Degenerated bipolar transistors are more noisy than non-degenerated quality jfets, especially with medium to high source impedances, such as pots. All in all, jfets are really better.
1audio said:
Hello demian,
Isn't Delrin a kind of plastic? I used to have tool handles made from it IIRC.
What's the effect in the audio application of a Delrin case?
Jan Didden
janneman said:
Hi Jan
Delrin is a Dupont polyacetyl, has about the same dielectric constant as mylar (3.2), not as good as PP, PS (2.2-2.5) or teflon (2.0), but not horrible. Good mechanical properites, we used it for self-lubricating spline adapters, then went to vespel.
chascode said:
I guess my comment was off topic.
What's really interesting about Delrin (and most plastics) is that if you rub it, with lets say your shirt tail, it retains an electric charge/field that is detectable (conservatively) a foot away and measures in the thousands of volts in the near field. It takes a long time for the charge to dissipate.
In my comments on machining I was wondering whether the charges built up during the machining process in conjunction with the friction and heating of the material might lock in a permanent charge in the plastic chassis, i.e. an electret type effect and what signature it might impart to the sound.
The mention of machining a preamp chassis out of Delrin raised the question in my mind as to what affect it might have on the sound. The question about the effects of machining is easy enough to answer.
Regards, Mike.
I used Delrin for its density (greater than wood) its stability and it being non-conductive. The case was built from 1" Delrin and quite heavy. It seemed to help the sound to keep unnecessary metal away from the circuitry. Static on the surface isn't really an issue here, the humidity is too high. The effect of the case seemed to be a lower noise floor (or so we thought, noting measurable).
1audio said:
That's a valid observation. I guess what I was wondering was whether the Delrin chassis had a marked sonic signature relative to the same (relative to your experience) circuit in a standard chassis. The lowering of the noise floor observation is interesting because the effects of close proximity metal relative to the effect of a close proximity (possibly) charged dielectric would be the variable.
One comment on the effects of high humidity, if the charge was, for a lack of a better term, locked into the Delrin by the machinin g process (an electret effect) the humidity would not disapate it.
I can very easily answer this by getting a sample from the machine shop at work and measuring it.
One way of looking at this is any charge would be static in nature and benign in it's affect.
Like I said, your experience raised a question. Thanks for your observation.
Regards, Mike.
How would you check for the electret effect? Sounds like you would need an electrostatic voltmeter to measure it. I used a black Delrin in sheet form. I don't have any here or I would check its resistivity.
This is an interesting subject.
On the one hand we have John Curl who spends 1000's of dollars on each BT amp case to mill it from a solid billet of aluminum, for its screening properties that improve the sound.
On the other hand, Damian maintains that a Delrin case hold unnecessary metal away from the circuit which improves the sound.
Help!
Jan Didden
On the one hand we have John Curl who spends 1000's of dollars on each BT amp case to mill it from a solid billet of aluminum, for its screening properties that improve the sound.
On the other hand, Damian maintains that a Delrin case hold unnecessary metal away from the circuit which improves the sound.
Help!
Jan Didden
- Status
- Not open for further replies.