Need advice on replacement amp for Altec 770a (Altec 604 Speakers)

[jim355]

I have a setup consisting of the Altec 604 e in what I believe is a Altec 612 cabinet. (It is about 6 cubic feet)

Anyway years ago when I built the box, I placed inside each one an Altec 770a amplifier.
https://www.hifiengine.com/manual_library/altec-lansing/770a.shtml
These amplifiers mount inside the speaker cabinet. So putting it there was perhaps not a great idea. As of now one is out of commission and I am not up to the $650 estimate to get it back in order.

So now I am browsing replacement amplifiers and it seems a replacement of any sort to fill the hole in the speaker cabinet does not exist.

So does anyone know of anything close to the 770a? it is a biamp plate amplifier. Everything I have found are mono subwoofer amps.

If I cant think of anything or find anything, I think my cabinets are now worthless.\

 

[asilker]

Hi Jim,
Altec 604s hold value very well. Perhaps those amps do too. If you're unable or unwilling to repair them, you might be able to sell the whole kit for a good penny and move toward something simpler.

 

[jim355]

Yeah I would probably do that. I think they could be repaired I just dont want to do it. However I am still left with a hole in my 604 cabinets. I guess the whole powered speaker cabinet died out in the 70s. I would have thought their were a couple manufacturers left but their seems to be nothing besides PA amps.

 

[bowtie427ss]

Those amps were problematic, and known to break. Frankly, i wouldn't bother with them unless you can find a competent tech willing to work for sane money. 650 to repair BOTH 770's would be absurd, that money to repair one is insane. Almost any stereo 2-way active crossover and pair of modest 2 channel power amplifiers will be an upgrade of sorts. 604's probably deserve better amplification anyway.

EDIT: it occurs to me that these particular bi-amplifiers were never suited for a 604 as their crossover frequency is switchable between 500hz and 800hz only. That's really too low to cross a later model 604. Were they modified at some point for a higher XO fequency?


Consider making filler plates for the amplifier cutouts. Many of Altec's utility and sound reinforcement speaker cabinets were built with a cutout for the 770/771 bi-amplifiers. Altec installed wood filler plates with the appropriate passive crossover chassis for the speaker model they were building. Here's a pair of examples:

 

[jim355]

Thank you... Yes I agree they are not perfect but I loved using them while they worked. Now they will be retired...

Good news is that I found what I hope is a suitable replacement without having to mod my cabinets too badly, Parts express sells stereo (or dual channel) plate amps with DSP/ customizable crossovers. They will fit into the side of my cabinet. https://icepower.dk/products/amplifier-power-modules/asx-series/ The guts seem to be made by Bang and Olufsen, so I hope the quality is there! The software seems a bit complicated but I hope to find even better sound once everything is done!

When i finish the fixes, I hope to share some pictures. The speakers are not super pretty (Homemade) but sound is what I care about

 

[bowtie427ss]

I would opine that you'd be further ahead to scratch build proven passive networks for your 604's and choose any of a myriad of well respected class AB power amplifiers(assuming you don't want to budget for classA), or even a known and respected tube amp.

Class D has come a long way. But, i'm still not sold on it for a speaker as resolving as a 604. Your mileage may vary.

There are several members here with various 604's using a variety of crossover and amplification schemes. You might consider asking a moderator to move this thread to the speakers forum or the Lansing Legacy forum where more of those members are likely to see this thread and offer input.