tom trim Posted January 1, 2017 Report Share Posted January 1, 2017 Hello All, I am new to this forum and was hoping you guys could answer some questions for me (please). I did use the search engine to try to get some answers but could not find much on the ADS PA-1's. I am an ADS enthusiast and own quite a bit of their equipment including a pair of L1090's in walnut (that I recently refinished), a pair of M12/90's in black lacquer, and three pairs of L1290's, two are Series 1 (one pair in pristine condition and the other in good condition) and a pair of Series 2 (somewhat beat up but sound great), all in walnut. I also recently acquired a pair of ADS PA 1 Bi-amplifiers at what I thought was a good price ($500 for the pair). Both pair of the series 1 L1290's have the cavity in the rear for the amps, the series 2 does not. I have only tried them on one set of the L1290's and they sound really good. Now for the questions. 1) Although sounding really good, one of the amps cuts out after playing music at moderate levels for a few hours. It will play fine again after the amp is off for awhile, but will then cut off again after some length of time. I assume there is a thermal device somewhere in the power supply circuitry that is tripping at some level of internal heat but since I did not receive any documentation with the amps, I can not verify this. Can anyone help? 2) The set of L1290's I am using (the good condition pair) had their internal crossovers modified by Audio Proz in Massachusetts due to a forwardness of their midranges (a common series 1 issue). I was still not completely happy with the sound... has an overall megaphone sound but the midranges are no longer forward sounding. I also had the tweeters and midranges rebuilt by Richard So in Arizona (former ADS Technician). This improved the sound further but there was still a slight megaphone tint to the sound. Anyway, on to my question. Does anyone know if the crossovers internal to the speakers are completely eliminated when the Bi-amp switch on the rear of the speaker is activated or does some of the signal still pass through the internal crossovers? It sounds to me like maybe the signal is completely bypassed since I do not seem to hear the megaphone sound anymore. But without documentation, I really do not know for sure. 3) Does anyone know where I would be able to find the User's and Service Manuals for the ADS PA 1 Bi-amplifiers? I would definitely be willing to pay for them as long as the price somewhat reasonable. I know these Bi-amps are rare so I fully expect that the documentation would be hard to find also. BTW, I am currently using a Adcom GFP-565 as a preamp for these amps and a Philips/ Magnavox CDB 650 CD player (using the unfiltered outputs) along with my new addition, an echo dot playing Amazon Prime Ultimate collection (I know, I know, MP3 files vs lossless audio... not quite there yet on that decision). The PA-1's are running on my second system that formerly employed an Adcom GFA-555 MK2 amp for power along with the preamp, cd player and the L1290's mentioned above. My main system consists of an Adcom GFP-750 (in passive mode), an Adcom GFA-5500 amplifier, a Musical Concepts modified Philips/ Magnavox CDB 650 CD player and a Denon DP-15F entry level turntable. I also employ an REL Storm sub with this system for the extreme lows on some recordings. I mostly use the M12/90's with this set up but sometimes switch out to the pristine pair of L1290's. Both pair sound great but the M12/90's hold a slight edge in imaging. I would like to try the PA 1's in the L1290's on this system soon after fixing the cut out issue. I am a mid-fi guy who loves the sound I get from ADS, Adcom and Philips equipment so I am not looking to change that, at least at this point anyway. Any help you guys could give would be greatly appreciated. Thanks. Tom Link to comment Share on other sites More sharing options...
Glitch Posted January 1, 2017 Report Share Posted January 1, 2017 Tom, Congratulations on finding a set of PA-1’s. I hope to be able to acquire a pair of these for myself someday. Unfortunately, I can’t help you with the PA-1 documentation. In bi-amp mode, the woofers are connected directly to the secondary set of binding posts and the woofer crossover circuitry is bypassed. The midrange/tweeter are driven from the primary set of binding posts and retain the midrange band-pass and tweeter high-pass circuitry. One thing that you may want to check for with the PA-1’s is that they have not been modified for use with L-1590’s. From what I’ve read, there are a few resistors that can be modified to lower the PA-1 crossover frequency to match the L-1590 drivers. I don’t think that this would affect you since the passive crossovers in the L-1290’s would filter out anything extra that the PA-1 modification would let through, but it might be worth a quick look. Google “ADS PA1 Resistors.pdf” for more info. Glitch Link to comment Share on other sites More sharing options...
tom trim Posted January 1, 2017 Author Report Share Posted January 1, 2017 Glitch, A Happy and Heathy New year to you! Thanks for your prompt reply. I did take a look at the resistors and they are set up for the L1290's. Thanks for the heads up though. I was glad to find these amps but I am a little concerned about the one that is cutting out I removed the back cover this afternoon and could not see anything obvious. Of course, I could not see all the solder joints as they were hidden for the most part and without further disassembly, I can not identify if there are any cold joints. I did notice that the power cord fit on that amp was somewhat loose. When the amp cut out, I immediately unplugged the power cord from the back of the amp and plugged it right back in. I could hear the relay reset and the amp started playing again. I'm not sure what that means but I thought changing to a newer power cord I had laying around might be worth a try. I will have to use the amps for a few of hours to see of it made any difference. It is interesting about the Bi-amp switch... I did not know it would still use the midrange band-pass and tweeter high-pass circuitry. I am now anxious to try the amps on the other L1290's that reside in my main system. The crossovers in those speakers have not been modified in any way. There might be a significant difference in sound. If the amp does not cut out tonight, I might give that a try sometime tomorrow. It would still be nice to find some documentation on these amps. Happy New year to all! Tom Link to comment Share on other sites More sharing options...
tom trim Posted January 15, 2017 Author Report Share Posted January 15, 2017 So after playing these amps using various sources, I determined that the one amp was cutting out due to a bad power cord. The original power cords were not included in the deal but the seller did supply two used 14 ga power cords. One of the times the amp cut out, I wiggled the cord at the connection on the amp and the relay reset and the amp started working again. I then replaced both power cords with 16 ga and the amps have been working fine ever since. I have listened for hours on end with no issues. These PA1 bi-amps sound awesome... the more I listen the better they sound. They are truly designed to compliment the L1290's (and I'm sure the L1590's also). They sounds better than either of my Adcom amps, along with other amps I have tried. I will now try them in my pristine pair of L1290's where I hope they find a permanent home. An added bonus; When casual listening to amazon prime music, I don't need to turn the amps on since I leave the power switches in the auto position. I can just tell Alexa to play something and it will turn the amps on and start playing. They then turn off automatically when I am through listening. Of course I have to leave the preamp on all the time, but I do that anyway because I think it sounds best when left on. The Adcom amps tend to chew up some KWH's if left on all the time. Tom Link to comment Share on other sites More sharing options...
Glitch Posted March 6, 2017 Report Share Posted March 6, 2017 Tom, Have you had any luck locating manuals for the PA-1's? I found a service manual for the Braun PA-1 on this website. http://www.vintageshifi.com/repertoire-pdf/Braun.php It is most likely identical to the ADS version except for the logo. I'm still trying to locate a user manual. Glitch Link to comment Share on other sites More sharing options...
DavidDru Posted March 6, 2017 Report Share Posted March 6, 2017 Keeping my eyes peeled for these. There is a CList add for the ADS subwoofer system up here but the seller did not leave any comntact info! Although I guess that system isn't all that. Link to comment Share on other sites More sharing options...
Glitch Posted March 8, 2017 Report Share Posted March 8, 2017 The Braun service manual has the most comprehensive information that I've seen yet about the PA1's. My German is pretty weak, but with the help online translators I've been able to figure out most of what I need to know about the amps. I did notice the the Braun version of the amp has a +-3dB range of the bass equalization, where the ADS version has a 0 to +6dB range. I was hoping to be able to figure out what frequency the bass filter is centered around. One could calculate it from the values given in the schematic, but since the design of the bass filter appears to be different, whatever frequency is found might be different anyway. What ADS subwoofer did you see on CL? What city? Link to comment Share on other sites More sharing options...
DavidDru Posted March 8, 2017 Report Share Posted March 8, 2017 It is the ADS 1500 with control module. $300 looks like new. Like I said, it was a CList posting but the lister left no contact info anywhere. I sent the notice of such that CList provides in this case numerous time to no avail. Link to comment Share on other sites More sharing options...
ST Santa Fe Posted January 1, 2018 Report Share Posted January 1, 2018 I just want to say congratulations on owning the whole package. I used to sell high end audio, and the AD 1290 Bi-amps were my favorite, especially when paired with the Nakamichi components we used to sell. Anything with high dynamic range was stellar. I actually liked them more than the Mac speakers we had. Glad I joined this site. Link to comment Share on other sites More sharing options...
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