I consider myself pretty lucky to have found a Fluke 407 at a Hamfest for $25. Brought it home, fired right up. That Fluke, and hp 710 or 713 (Got one of those too, on a trade) and a Lambda 71 are the classic flaming beasts of this realm. Of course I love this gear, but in many respects they sit unused more than one might imagine. I used to have a Lambda 71 but it arrived with enough freight damage to make it something I didn't want to fix for what it would have cost. I also have a KEPCO HBK that I bought for $100 because it had 4 nice 6550's in it and I sold the tubes for $200. (Works with 6L6 just fine, somewhat reduced current capacity)
That's another angle: Sometimes these supplies are found with valuable output tubes, 5881, 6550, 6L6, that have as much or more value than the supply as a piece of gear. You can use crappy old 6L6's pulled from amps in these just fine.
There are also other brands of these types of lab supplies: Power Designs, Oregon Electronics, Dressen-Barnes, Lambda and certainly 3-5 more that are perfectly usable for this application. And the Heathkit and EICO ones are fine.
Just some random thoughts: Many of these supplies only go up to say 325 volts (VERY common on Lambda) and only go to 100 ma. That/those a bit problematical if indeed your aim is to breadboard higher power amps. Yet IF you are building high power guitar amps, it's pretty danged rare to have those amps have regulated supplies. INSIDE a 325 volt lab supply you will probably find unregulated B+ up to 450 volts. Yes, I know, in our rather inexact world of guitar amps, the lab bench supply is meant more for super-convenience as to dialing in and metering an exact voltage / current rather than its regulating action. Finally, if your aim is to prototype preamps, then who needs a huge supply for 5 mils?
I would also suggest, if it's at all interesting, to look for old junk lab-type tube gear; many items had regulated supplies for their innards, which means you can buy the $20 UHF generator and get a box with an internal supply, rip out whatever isn't the supply, and build something inside. No, it won't have the nice meters, etc; but with the ability to buy $3 LED voltmeters on ebay, this is a nothingburger. Virtually ALL of these supplies (as built into equipment) have a similar tube complement, big pass tube or two and gas regulator or two. The bowling-pin shaped gas regulator tube is a giveaway.
If you spend some time at google images looking for "Lambda tube supply" or "high voltage supply" or those brand names you'll get some pictures in your mind of what these look like and some day you'll be in a junk shop and find one.
So you'll get no criticism from me if you would like to own and use one of these beauties, even if you want to rush out and (IMO) overpay for it. All I would say is, if you want to build/proto tube amps, don't let the lack of one of these stop you. Have patience, keep your eyes open for a cheap one and by all means, buy a $35 special, but don't think you have to rush out and spend $300++ when with TWO salvaged tubish transformers; one on a variac, the other not....you can get all those voltages (and your bias) without any great engineering effort. No, it won't have nice meters and nice box.
Topic: bench power supply for amps (Read 9849 times)