What to do?

Good morning!

Newbie here. I've had a pair of Dyna ST-70s since the late 1970s. I used them in stock form, set to mono and cross-wired, to drive a pair of AR 4-Xs for many years. I fed them with a PAS-II or III, I don't remember for sure. In 1991, Kevin Kennedy (KTA Audio) modified them to bi-amplify a pair of Audio Concepts, Inc. Sub-1s and Little Vs. After 32 years, including 6 years of dormancy, the system needs work and I've moved on.

I've isolated the various problems with my system, however. One of my ST-70s I was using to bi-amplify the ACIs has issues. It won't bias up and it hums, Tube swaps don't help, so I suspect it needs to be recapped. I rigged the other two amps (one of which uses one channel in triode mode for the LV and the other channel in ultra-linear for the Sub-1, and the third amp, which is set up in stereo triode mode to drive another set of satellite speakers), to test all four speakers. I've determined the drivers are done after 32 years, including 6 years of dormancy--when I press on them with my fingers, they feel stiff and make a crunchy sound.

Fortunately, my hand-made, tube preamp (also KTA) is still a gem, and It now feeds a used but new-to-me Mac MC152, which drives a pair of Revel M106s. I think I'm happy with the new gear, and the 33-year-old REGA II with the 19-year-old Semiko Blue Point Special EVO III is still remarkable! Vinyl really is the best!

So, my question for the brain trust is this: What do I do with 3 heavily modified ST-70s (the front end boards are designed and made by Kevin and utilize one 12ax7 and two 12Au7s), two Little Vs, and a pair of Sub-1s with crossovers modified for bi-amplification?

Thanks, Folks!

Heavily modified 60 year old amps that don't work?
I'd give them away to a DIY person that wants to use the parts to build something else.
Sounds like they're done.

Dave_in_Va wrote:Heavily modified 60 year old amps that don't work?
I'd give them away to a DIY person that wants to use the parts to build something else.
Sounds like they're done.

I've used the triode, stereo amp to drive new, Revel M106s and it sounds quite good. One of the ultra-linear/triode mono amps also works fine.

settador wrote:Good morning!

Newbie here. I've had a pair of Dyna ST-70s since the late 1970s. I used them in stock form, set to mono and cross-wired, to drive a pair of AR 4-Xs for many years. I fed them with a PAS-II or III, I don't remember for sure. In 1991, Kevin Kennedy (KTA Audio) modified them to bi-amplify a pair of Audio Concepts, Inc. Sub-1s and Little Vs. After 32 years, including 6 years of dormancy, the system needs work and I've moved on.

I've isolated the various problems with my system, however. One of my ST-70s I was using to bi-amplify the ACIs has issues. It won't bias up and it hums, Tube swaps don't help, so I suspect it needs to be recapped. I rigged the other two amps (one of which uses one channel in triode mode for the LV and the other channel in ultra-linear for the Sub-1, and the third amp, which is set up in stereo triode mode to drive another set of satellite speakers), to test all four speakers. I've determined the drivers are done after 32 years, including 6 years of dormancy--when I press on them with my fingers, they feel stiff and make a crunchy sound.

Fortunately, my hand-made, tube preamp (also KTA) is still a gem, and It now feeds a used but new-to-me Mac MC152, which drives a pair of Revel M106s. I think I'm happy with the new gear, and the 33-year-old REGA II with the 19-year-old Semiko Blue Point Special EVO III is still remarkable! Vinyl really is the best!

So, my question for the brain trust is this: What do I do with 3 heavily modified ST-70s (the front end boards are designed and made by Kevin and utilize one 12ax7 and two 12Au7s), two Little Vs, and a pair of Sub-1s with crossovers modified for bi-amplification?

Thanks, Folks!

My advice : rebuild them according to the dynaco manual. All parts are available ( you need the board, and as 7199 is unavail get the board for 6U8 / 6an8 / ecf80.

When they are original they are sellable for a higher value.

Thanks, peterh. I do understand that, but at this stage of my life time is more valuable than $. I will be happy with whatever the market dictates. The speaker cabinets are in good shape, and someone who wants to replace the drivers and repair the bad amp good have some good sound for little money, comparatively speaking.

PeterH response is always spot on. However I understand your issue as well. Under the first sticky post above you can list all of your stuff for sale. Let the next owner restore them properly.

WLT wrote:PeterH response is always spot on. However I understand your issue as well. Under the first sticky post above you can list all of your stuff for sale. Let the next owner restore them properly.

What do you all think these amps are worth? What are my chances of finding someone to take the 3 of them and the speakers too? All guesses welcome!

I sent you a PM. Pictures would help on condition of the amps. Inside and out. Do they have the covers and are the original circuit boards included? The more info we get the more we can give a better estimate.

Yes, they have the covers. No, I do not have the original parts, nor do I have the 1299s. As I get closer to listing them, I'll take good photos.

Hi folks, I'm back.

I would like them to go to a good home: Modified ST-70s; one is operational and the other hums and won't bias up. Amps are set up to bi-amplify Audio Concepts, Inc. Sub-1s and LV speakers also available. Cabinets are in excellent condition. Wonderful sounding, custom pre-amp with developing power supply issue also part of the kit. Pick-up in Seacoast NH. I'll consider a reasonable offer for good ST-70 cores and fine speaker cabinets. ACI wall speakers thrown in for fun! Detailed pictures available.

OK Is just the pre for sale and are you shipping? Thx. Dale

Hi Dale,

Yes, if nobody wants the whole kit after a while, I will sell the components separately. I can ship the pre-amp most easily too, when the time comes. Have you seen the pictures on the for sale listing?

Also, reading back through my original posting, I want to tell you that the system has changed yet again. That solid-state Mac amp and Revel speakers? Yeah, not my sound, and that stuff is long gone..........

What neck of the woods are you in?

Seacoast New Hampshire, 15 minutes west of Portsmouth.