Just Curious - Aluminum or Steel

[stokes]

Didn't Marshall use aluminum chassis in their amps?

Read somewhere that this is one of the keys to their tone? Any truth to this?

I have used both steel and alumunum,and never noticed any big advantage tonewise between the two.The big difference is the reasons already mentioned,ease at cutting holes etc.,stiffness and the ability to support the trannies and overall weight.I use Greenlee punches so cutting holes is not a problem in either.As for conductivity and "magnetic shielding",I've never had a problem with either steel or aluminum.I think if the builders from the "golden era" were on to something using a combo of both,we would see more high end manufacturers doing the same.It may make a difference in Hi-Fi audio,but guitar amp tech is not as exacting a science,and I think either is good enough.As for rust in the steel,the black or grey coated chassis seem to alleviate that.Just my 2 cents.

[Bruce / Mission Amps]

Very good... no reason for anyone to get upset in a self help DIY site like this.
Keeping it friendly and helpful is what keeps it alive.

[mooreamps]

Bruce,

Thank you for your vote of confidence. Apology humbly accepted.

-g

[bob p]

i think that one of the reasons that experienced amp builders can get by with either steel or aluminum is because they're experienced enough to know what to do with both. by getting the layout right (or by just copying a good layout), and by using good wiring techniques, you can avoid most of the problems, and your choice of steel or aluminum won't make a significant impact on your guitar amp build.

OTOH, if you don't have a good design, you're more likely to run into the problems that led people to start using aluminum in the first place. laying a PT down on a steel chassis so that the lams are parallel to the chassis will couple some noise into the chassis, but there are ways to address the problem, and the adverse effects of that kind of layout may not be critical in an MI application.


regarding the superlatives of high end HiFi gear -- I don't place as much faith in the tube stuff that's being designed today as the stuff that was designed during the "golden era." In the golden age, money was spent on things that mattered, and HiFi cosmetics weren't as extreme as High End cosmetics are today. In today's high end, a disproportionate amount of money is spent on cosmetics, and costs get cut to enhance profitability in places where the customer can't see the corners being cut.

I've repaired a few high end products that were absolutely beautiful objects d'art on the outside. The boxes looked like a machinist's pride and joy. The external quality and fit and finish were so impressive that merely looking at the product would inspire confidence in the customer. The boxes are so good that they sell the product, because people who buy today's High End are often buying things that they want to look at and display in their home.

On the inside, however, some of these "high end" amps had poorly manufactured PCBs that were stuffed and soldered in a third world country. The insides of some "high end" tube HiFi gear is marred by the same construction techniques that we despise in our MI amps: tube sockets that mount directly to PCBs by solder joints; large numbers of snap-in lytic caps that are crammed up against one another in a honeycomb pattern and can't dissipate heat; poor lead dress, and flimsy PCBs without through hole traces.

Looking at the "high end" stuff of today, its very pretty on the outside, but a fair number of pieces are prettier on the outside than they are on the inside. In the "golden era" the opposite was true -- things may not have been as pretty as they are today, but internally they were very well made.

If the cheesy internals on some of today's high end stuff is any indication of how far most purveyors are trying to push the envelope, then I'm not to inclined to look to today's high end gear to define what's best for tube technology. Yesterday's efforts may have been better. In today's marketplace, I think that there is more pressure than there ever was to cut corners to make things profitable, even at the high end. To an extent that I think is not insignificant, buyers of today's High End products are often played for suckers.

I was really disappointed when I repaired a broken Sonic Frontiers EL34 HiFi rackmount stereo amp. With its machined aluminum and gold anodized faceplates, it was definitely prettier on the outside than it was on the inside. I was also disappointed to see some of the construction techniques in the Audio Research "reference series" of amplifiers. When I took the topcover off of an AR reference series monoblock and saw the tube sockets mounted tot he PCB with solder joints, I felt like that I had pulled back the curtain only to find that the man behind the curtain was not the Wizard of Oz.

These "High End" amps of today haven't brought anything new to the table in terms of tube amp design. They're conservative, traditional designs that follow conservative operating parameters that were established in the 1950s. The difference is that they're manufactured with today's construction techniques. On the outside, they are absolutely beautiful, but on the inside they use construction methods which most of us DIYers are less than enamored with. I'll go one step further, and say that for "high end" products, their construction techniques are objectionable. The idea of plugging tubes into sockets that mount to PCBs on solder joints just irks me, and it doesn't seem appropriate to find that kind of stuff in a pair of monoblocks that sell for five figures. It just doesn't make sense to spend that kind of cash for "high end" when you can DIY equivalent 1950s "HiFi" for a small fraction of the price. But then I guess that's what makes us Ampagers, eh?

[stokes]

Bob,I didnt mean to infer that todays amps,regardless of Hi-Fi or guitar amps,can hold a candle to the vintage amps.I am a big fan of the "golden era" products,and do not like to work on many current production amps for all the reasons you pointed out (pcb's,pcb mounted tubes etc.).Was merely commenting on the alluminum versus steel chassis point,and the observation someone pointed out about the use of a combination of both steel and aluminum in one chassis.For my money,anything built in the '50's can kick the snot out of anything made today,and my experience is with guitar amps,as I dont deal with Hi-Fi equip.as much as you do,but even with my limited use of Hi-Fi,I would bet that a competent DIYer can build a better point to point mono-block than the pcb crammed,"high-end" stuff made today.

[bob p]

i never doubted that we'd agree on that. more than anything else i was making a point that opening up a High End amp today and looking inside is pretty good evidence that alot of today's hifi customers are being played for fools. that makes me think that we can't expect the same companies that make these amps to be doing serious tube R&D. even the biggest, most respected names are just applying today's cheap manufacturing technology to classic circuit designs, and putting the stuff in a fancy box. you know, nice packaging makes people feel good about taking out that second mortgage to buy a High End amp.

[Le Basseur]

the ideal chassis is made of copper,

I thought nobody'll mention that!
I use copper extensively in every Hi-End DIY project or order I get,assuming that the future owner agrees for a more costly chassis material.The only problem with copper is that it has to be protected IMMEDIATELY after polishing.If not,it goes spotty in a few minutes.
Both steel and aluminium have pros and cons...as it's already said,steel is prone to electromagnetic havoc and rust.On the other hand,aluminium is flawed with that thin oxide layer....every time when I have to determine with my scope the best/the quietest ground bus placement (altough,a simple but time-consuming procedure) on an aluminium chassis,I have to scratch the inner chassis' surface a few dozens of times...not very pleasant.
Back to the topic:I'd go one step further by saying that the ideal chassis material is...silver-plated copper!
....but,again,who can afford this on a bigger scale....
Regards,