Rob11966,
In several decades of building both transistor and tube amps, I always had trouble with some hum with the about 5 x steel chasses I tried - had to scrap some. I am at present trying to help someone with a EL84 15W amplifier with all Partridge transformers on a steel chassis, and minimal hum could only be obtained with the power transformer held at a crazy angle in space. I have also tried with several other transformers, all to no avail - that my experience.
In contrast I never had real trouble on an alu chassis (dozens of projects, some 100 watters). I am a little reckless in earthing anywhere on the chassis (close to whatever component, except for inputs), still OK. I avoid using drop-through power transformers. I cannot say that I ever particularly tried to do electrical insulation, but it is practical if some members had bad experience by not doing it.
As far as aesthetics go I use powder coating, screening earth points with stickers. Anodization could look more classy, but is quite expensive (over here, at least).
YET! Many commercial amplifiers are built quite successfully on steel chasses! But for my preference .......
Regards.
In several decades of building both transistor and tube amps, I always had trouble with some hum with the about 5 x steel chasses I tried - had to scrap some. I am at present trying to help someone with a EL84 15W amplifier with all Partridge transformers on a steel chassis, and minimal hum could only be obtained with the power transformer held at a crazy angle in space. I have also tried with several other transformers, all to no avail - that my experience.
In contrast I never had real trouble on an alu chassis (dozens of projects, some 100 watters). I am a little reckless in earthing anywhere on the chassis (close to whatever component, except for inputs), still OK. I avoid using drop-through power transformers. I cannot say that I ever particularly tried to do electrical insulation, but it is practical if some members had bad experience by not doing it.
As far as aesthetics go I use powder coating, screening earth points with stickers. Anodization could look more classy, but is quite expensive (over here, at least).
YET! Many commercial amplifiers are built quite successfully on steel chasses! But for my preference .......
Regards.
Aluminium it is!
Hi Johan,
Your personal experiences with this have been very instructive. I really need to make this as fool proof as possible and the potential 'hum' with the steel does concern me. My main reason for choosing steel was the ability to gety a nice electroplated finish but after speaking with the electroplaters today they tell me that aluminium is easier for them anyway. So aluminium it is!
Cheers,
Rob
Hi Johan,
Your personal experiences with this have been very instructive. I really need to make this as fool proof as possible and the potential 'hum' with the steel does concern me. My main reason for choosing steel was the ability to gety a nice electroplated finish but after speaking with the electroplaters today they tell me that aluminium is easier for them anyway. So aluminium it is!
Cheers,
Rob
How thick
After saying avoid alu I should clarify to say avoid flimsy cases. If you were making your amps in 2mm thick pure alu I would say that’s alright. Still some high-end audio gear manufacturers will not use alu. If you build a steel case even a thin one it is going to be stronger than an alu one. What I try and do is use 2mm die-case cases. Because I use a lot of off the shelf Jaycar stuff this often means remote supply for amps. So one case for the amp and one for the PS. They have done me a favour.
Yes they are alu but they are solid as!. Also the cases I use are cheap. This actually works to my advantage because there is all sorts of other metals in there making a heavy dense 2mm thick material. Dampen your case too. I caused a riot on another thread talking about resonance so unless you really want to know I will say no more about it here. I said resonance NOT vibration – so many try to say they are the same.
After saying avoid alu I should clarify to say avoid flimsy cases. If you were making your amps in 2mm thick pure alu I would say that’s alright. Still some high-end audio gear manufacturers will not use alu. If you build a steel case even a thin one it is going to be stronger than an alu one. What I try and do is use 2mm die-case cases. Because I use a lot of off the shelf Jaycar stuff this often means remote supply for amps. So one case for the amp and one for the PS. They have done me a favour.
Yes they are alu but they are solid as!. Also the cases I use are cheap. This actually works to my advantage because there is all sorts of other metals in there making a heavy dense 2mm thick material. Dampen your case too. I caused a riot on another thread talking about resonance so unless you really want to know I will say no more about it here. I said resonance NOT vibration – so many try to say they are the same.
Great. I am currently getting a chassis made up of 2.0mm Al. I am having it laser cut from a CAD drawing and paying well for it so I'm glad to get your feedback.
Fair enough.mhouston said:
OK. I am planning to instal a bulkhead for strength and for electrostatic shielding between the noisy half and the clean half of the underside of the chassis. In response to your comments on resonance I am thinking of also tacking some bitumen roofing strips beneath the chassis in the free areas, as this seems the logical thing to do. Come to think of it I may have seen this done before in commercial designs.
you got it
You are very much on the right track – in fact we think a like when it comes to that dirty word “resonance”. Jaycar (I see you’re from Australia) sell a plastic/rubber mate which is used to line speakers. It has barium in it which make sit heavy. Glue it every where in the case which does not get hot. Glue it under the case. There is no need to disfigure you case to do this. The amp should not only sound beautiful but look beautiful too. If you are married you will know about WAF.
If trannies don’t get hot grommet mount them. I grommet mount my cct. brds in my valve preamps and then use self adhesive computer mounting feet. Jaycar sell heavy brass isolation feet ($30). I don’t use the double sided sticky rubber pads they provide bolt them direct into the case. Use isolation plates under your amp. I have too favourites. ½” glass plate on thick silicon feet and the other ½” Italian marble on silicon feet. Both 300 X 400mm. I also use silver wire in the audio path. This is pure silver .7mmm thick and I cover it with spaghetti or cotton insulation. It is cheap and generally you don’t use much.
I could go on for hours but I will bore you. Let me know if I can make some more suggestions or just disagree with me as so many other have done.
You are very much on the right track – in fact we think a like when it comes to that dirty word “resonance”. Jaycar (I see you’re from Australia) sell a plastic/rubber mate which is used to line speakers. It has barium in it which make sit heavy. Glue it every where in the case which does not get hot. Glue it under the case. There is no need to disfigure you case to do this. The amp should not only sound beautiful but look beautiful too. If you are married you will know about WAF.
If trannies don’t get hot grommet mount them. I grommet mount my cct. brds in my valve preamps and then use self adhesive computer mounting feet. Jaycar sell heavy brass isolation feet ($30). I don’t use the double sided sticky rubber pads they provide bolt them direct into the case. Use isolation plates under your amp. I have too favourites. ½” glass plate on thick silicon feet and the other ½” Italian marble on silicon feet. Both 300 X 400mm. I also use silver wire in the audio path. This is pure silver .7mmm thick and I cover it with spaghetti or cotton insulation. It is cheap and generally you don’t use much.
I could go on for hours but I will bore you. Let me know if I can make some more suggestions or just disagree with me as so many other have done.
Re: How thick
Oh please. I do not like the sound of that comment (see below).
Ye-e-e-s OK. But also keep in mind that transformers on alu help keep resonance at bay. I have used 16 gauge with cross-bars under-chassis, with no noticeable problems (see my above comment) when thick alu was scarce and pricey. But not criticising; if feasible you are right, of course.
My sympathy. One has to bear with those ignorant of the basics of motion of mass. If I am allowed a brief lesson: I once called a Buro of Standards expert on lubricants, regarding uncertainties about what should not be mixed. The man cut my well-prepared speech short in his lovely Scottish accent: "Laddy, ya shouldna listen to all the old wives' tales ya hear." Amen!
But to broaden my horizons: Pray, what the @#%$* is it that is supposed to be seen or felt or heard or measured or experienced in whatever psychic way about chasses, that I have missed over half a century in the business? (Naturally not thinking of flea-size thickness.)
Regards
mhouston said:
Oh please. I do not like the sound of that comment (see below).
Ye-e-e-s OK. But also keep in mind that transformers on alu help keep resonance at bay. I have used 16 gauge with cross-bars under-chassis, with no noticeable problems (see my above comment) when thick alu was scarce and pricey. But not criticising; if feasible you are right, of course.
My sympathy. One has to bear with those ignorant of the basics of motion of mass. If I am allowed a brief lesson: I once called a Buro of Standards expert on lubricants, regarding uncertainties about what should not be mixed. The man cut my well-prepared speech short in his lovely Scottish accent: "Laddy, ya shouldna listen to all the old wives' tales ya hear." Amen!
But to broaden my horizons: Pray, what the @#%$* is it that is supposed to be seen or felt or heard or measured or experienced in whatever psychic way about chasses, that I have missed over half a century in the business? (Naturally not thinking of flea-size thickness.)
Regards
jnb said:
NO! Some common sense is required here.. LOL In an application like this the regulator should be mounted on a heat sink on a small, well isolated pcb or piece of vector board far away from any possibility of contact while operating. I use this technique only for filament supplies and others operating at less than 50V.
Hammond offers chassis that are already black powder coated, at a cost of a few dollars over a "bare" chassis. Of course, one needs to use a lot of care with these to keep them looking good after punching and drilling. Although your color choice is limited to Henry Ford's favorite, it's less expensive than having it done at a local shop.
Case paint
I do all my drilling first then spray colours on last. Lately I have been using an acid etch primer, again in spray form.
Once the final coat is on (give the primer at least 24 hours depending on weather) the finish is thick and rich in luster. It takes a little more time but the finish is very pro. and tough?
I do all my drilling first then spray colours on last. Lately I have been using an acid etch primer, again in spray form.
Once the final coat is on (give the primer at least 24 hours depending on weather) the finish is thick and rich in luster. It takes a little more time but the finish is very pro. and tough?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.