Would it be practical or worthwhile to build a tape delay that uses cheaper and more commonly available components than what you see in the echoplex sort of units?
In order from cheapest to most expensive, you have...
Audio Cassettes.... you can get the tape heads & the tape virtually free, the only tough part is hooking it up mechanically and getting the record signal level to an optimal point.
8-track... tapes & players alike are at goodwill stores all across the country. Again the mechanical aspects are probably the most difficult. I didn't know if maybe you could get a higher quality here since it's a wider band of tape.
vintage reel-to-reel players... Ebay. The mechanics would be easiest here. But it's the most expensive. This route might not be any better than buying a broken Echoplex and fixing it.