|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
63.246.168.59
In Reply to: Re: Here's what I found... posted by slowburn on March 10, 2007 at 17:30:11:
Maybe I was too hasty regarding the brand stamp. Even before I read your post, I was thinking that painting the chassis isn't such a big deal, and that the stamping could be filled if necessary. Too bad it prevents using it in a natural aluminum finish; I like that look for some projects. Incidentally, I do most of my own cutting using hand tools. I also have limited access to a small machine shop at work, so it might be possible to use a mill to clean up the welds and cut down the flanges on these cake pan chassis.My main concern right now is whether the pans on Surfas' Web site are the same ones you're buying in the store. A thickness of .065" is great for preamps and small amplifiers, but for larger iron, .090" or more is needed. I have sent an e-mail asking them to confirm the thickness and brand of the pans, just to make sure I get the right ones.
I like your DIY'er of the month project - very inventive! Unless I missed one, Hagerman phono preamps are all 9-pin, so I assume you designed the octal version yourself. I use octals wherever possible, and particularly with octal output stages. Even where I don't use octals, I almost never mix the two types on the same chassis. Tubes like 6BQ5s generally get driven with EF86 / 12AX7 / 12AU7 / 7044 types, with 6SL7 / 6SN7 / 6BL7 octals (and 12V counterparts of the first two) reserved for use with 6V6s, EL34s, 7591s and large SETs. There are always exceptions, but this is how I generally attempt to keep a sense of order in the designs.
About the aluminum chassis, I am currently building a few guitar amplifiers. I have a fair amount of vintage hi-fi iron that's well suited to this purpose, but it's heavy. That's why I need to confirm that the chassis on Surfas' site are in fact 1/8". I have to say, I really don't understand what Hammond is thinking, making .040 and .050 chassis. Those boxes wouldn't last a week in a guitar amp. Even many of Hammond's own transformers would collapse their boxes. Could it really cost that much more to use .080"-.090" material?
Thanks for all your help and good ideas on this. If you come up with more info on the exact chassis your buying at Surfas, please let me know.
Follow Ups:
Here's another link to what I believe are the same pans.I used a 13x9x2 for the Cornet. And by the way, while I'd like to take credit for the octal version, I'm afraid I can't. Mr. H posted the schematic on the Hagerman Discussion Board. It's all his circuit. The only thing I changed was the chokes. I plan to remove the second choke, too, as it didn't drop the noise floor. I'll cover up the gaping hole with another plate--in which, I'm putting a stand-by switch.
Speaking of which. Wha'd'ya think's the best way to implement a stand-by switch? I think I'm going to put a SPST on/off toggle on the power trans' center tap. I'm terrible with the simplest electrical logic but it seems that simply lifting the ground on the HV winding will kill the supply to the tube plates. Make sense?
I understand your concern about the flimsy thing. I just measured the Cornet's flange thickness and it's 1/8". That's .125 inch and I think it's plenty stiff.
The iron on my example is an NOS Stancor, electrostatically shielded, 300/0/300 @ 120mA, 6.3 CT @ 5A, 5V @ 3A, so it's plenty heavy. Both chokes are old iron, 15 and 10 Henrys.
The power trans is horizontal orientation so it require a big, rectangular cut out for one half of the winding to drop below the chassis deck.
Altogether, a lot of aluminum cut away in a small area and it's still strong, pretty stiff. Lord knows I've plugged it in, unplugged it, carried it to-and-fro for a hundred tests and mods. Every time I lug it I feel it not flex, think of that Hammond I'm glad I sent back. (and which I'm eternally thankful that partsconnexion's vicki agreed to take back!)
My guess is that if you put a power trans and a couple OPTs on a bigger pan, it'd hold tough. If you thought it wasn't quite up to snuff for a guitar amp that'll get knocked about, you could always slap another chunk of 1/8" aluminum under the trannies. Quarter-inch of aluminum would be strong as hell and pretty light, too.
Do you know the stock number of the 9 x 13 pan you purchased at Surfas? They haven't answered my e-mail, and I'm really confused about the source of your 1/8" pans. The link in your last post goes to a page listing Magic Line pans, but I just measured those at my local supplier. They are only .065" (1/16"). Many outlets on the Web also list Magic Line with a description stating that the pans are 14 gauge (approx. .065"). What the heck are you buying?? Help!
"What the heck are you buying?"For my thickness quote, I'd measured a scrap that I thought was the cut-out from the power transformer. Just now, I dug in the scrap box and found evidence that it was possible that I'd measured the wrong scrap of aluminum.
Well, I just pulled the actual Cornet off the shelf...
Good lord, this is embarrassing. It is 1/16-inch, which is why they're telling you it's .065 inch. Man-O-man am I sorry.
Here's the good news, though. It is tough stuff and it absolutely outclasses any of the Bud or Hammond boxes that I've tried.
I see, now, how I confused myself. In order to banish even the thought of having to order something from Hammond again, I've been experimenting (duh!) with all sorts of readily available products. The chunk I measured, then swore to you was 1/8" thick, was a piece of a commerical COOKIE SHEET.
Yes, it appears that I'm a serial bakeware mutilator.
I sincerely apologize.
Here's what I think you should do, though. Indeed, Magic Line is the ticket. Go ahead and order one. I know you're a penny pincher but so am I. I can't bear to order a nice chassis for $75 and that's how I ended up with these things. I arrived at the cake pans via commercial aluminum bakeware that I'd scored in thrift stores for cheap. (same place I got my other experimental materials) These turned out to be so ideal that I went ahead and bought a new one (horrors!). See, by the time a bakery or restaurant tosses them to the thrift, they are--how shall we say?--less than presentable.
Sorry again. Although you may feel misled, I assure the mistake is insignificant. Like I posted earlier, I must have 12-15 pounds of iron on that thing, as well as four octal holes and their surrounding vent holes. Still stiff as a board. The corner welds, while not perfect, posed no problem that I couldn't easily remedy with hand tools.
I do agree about the finish, though. I'd liked to have polished the raw aluminum, sealed it with clear coat. You know what they say, though. Fast, cheap, and good; pick two.
This post is made possible by the generous support of people like you and our sponsors: