i believe this is what you are looking for
http://gilmore.chem.northwestern.edu/accoustat1.gif
http://gilmore.chem.northwestern.edu/accoustat2.gif
http://gilmore.chem.northwestern.edu/accoustat1.gif
http://gilmore.chem.northwestern.edu/accoustat2.gif
Does anyone have any experience trying to build these? I had a set of the III's with the tube amps and hey were great to listen to as long as the amps ran. If they could be improved and made more reliable it would be a nice piece of 'history" to have. I still have a set of II+II's that would be fun to drive with this amp.
rt
rt
DD Amps
SY,
Great...I had a lot fo fun with the III's...bought them used in 1979...eventually bought the transformers and later regretted it...should have kept the tube amps even though they were always blowing up....just should have learned to fix them.
They were not perfect but they sure did sound sweet and imaged well when they were set up right and being fed good source material. I was doing a lot of live recording then..all acoustic small groups...folk...chamber music etc......two NAK CM-300's into a reel to reel 1/2 track....the tapes sounded sweet out of the III's!
rt
SY,
Great...I had a lot fo fun with the III's...bought them used in 1979...eventually bought the transformers and later regretted it...should have kept the tube amps even though they were always blowing up....just should have learned to fix them.
They were not perfect but they sure did sound sweet and imaged well when they were set up right and being fed good source material. I was doing a lot of live recording then..all acoustic small groups...folk...chamber music etc......two NAK CM-300's into a reel to reel 1/2 track....the tapes sounded sweet out of the III's!
rt
Yeah, I've heard a lot of negative buzz about the reliability of the Acoustat amps. One of the things I'm trying is the use of TV sweep tubes- you can get a lot of watts dissipation for not many $$$. Tubes like the PL509/519 can take 4000 volts on their plates, yet swing enough current to move the diaphragm without breaking a sweat.
I have repaired and modified dozens of these amps. In fact, at one time we offered a complete new all tube driver stage (replaced the op-amp front end that was, at best, equal to a Dyna PAT-4 in sonic quality). We don't offer the work any longer due to the amps two fundamental problems:
1) the HV power transformer fails frequently and with the trail of owner changes over the years, replacements are near impossible to find. Some customers have resorted to either buying another amp or pair for spare parts or having the transformer rewound - both expensive propositions.
2) The 6HB5 output tubes are are operating near boderline voltage rating. It is common for them to flash and ark until everything stabilizes immediately after turn-on (which by the way must be after the filaments have reached 50 % operating temp to avoid complete destruction). I haven't checked recently but the 6HB5 may have materialized into unobtainium.
That having been said and even with the poor front end they sound much better than any of the transformer interfaces.
1) the HV power transformer fails frequently and with the trail of owner changes over the years, replacements are near impossible to find. Some customers have resorted to either buying another amp or pair for spare parts or having the transformer rewound - both expensive propositions.
2) The 6HB5 output tubes are are operating near boderline voltage rating. It is common for them to flash and ark until everything stabilizes immediately after turn-on (which by the way must be after the filaments have reached 50 % operating temp to avoid complete destruction). I haven't checked recently but the 6HB5 may have materialized into unobtainium.
That having been said and even with the poor front end they sound much better than any of the transformer interfaces.
Joe,
Many thanx for posting your experience. Guess I will not attempt to recreate an original tube amp for the Acoustats. I have to agree on all counts...I was tired of the amps blowing up so I went for the transformer interface and I was really dissapointed by what I heard. However, as i stated previously, I still have a set of II+II's and would like to run them with a tube amp like the Acoustat but with better reliability and of course better sound.
SY's project sounds pretty interesting.
I also someday would like to pick up a set of III's (I still know where mine are.) just because I had so much fun with them...they were neat speakers and that alone makes it easy for me to rationalize...they had a high fun factor...especially when used for playback of my live tapes...
Any advice?
Thank you,
rt
Many thanx for posting your experience. Guess I will not attempt to recreate an original tube amp for the Acoustats. I have to agree on all counts...I was tired of the amps blowing up so I went for the transformer interface and I was really dissapointed by what I heard. However, as i stated previously, I still have a set of II+II's and would like to run them with a tube amp like the Acoustat but with better reliability and of course better sound.
SY's project sounds pretty interesting.
I also someday would like to pick up a set of III's (I still know where mine are.) just because I had so much fun with them...they were neat speakers and that alone makes it easy for me to rationalize...they had a high fun factor...especially when used for playback of my live tapes...
Any advice?
Thank you,
rt
If you are willing to accept the reasonable possibility that you may lose the (non-replaceable) HV transformer - my advce would be to try to find an original pair with working tansformer(s). There are 3 proprietary transformers in addition to the HV transformer. Two feed the filaments in the "upper" tubes and therefore need to have at least a 5KV insulation rating. The remaing transformer feeds the bottom output tube filaments and provides the lower voltages for the screen grids and op-amp supply lines.
Then change the output tubes to PL-509's as suggested earlier. I have recently redesigned the original Beveridge esl amp (using all tubes in the driver stage) using this tube in the output. There are absolutely no problems with arc-over even when the filaments are powered up at the same time as the HVB+.
You could also try better op-amps in the driver circuit. Be careful - the original op-amps were 741 vintage and the current crop of op-amps are sure to oscillate without necessary provisions.
Then change the output tubes to PL-509's as suggested earlier. I have recently redesigned the original Beveridge esl amp (using all tubes in the driver stage) using this tube in the output. There are absolutely no problems with arc-over even when the filaments are powered up at the same time as the HVB+.
You could also try better op-amps in the driver circuit. Be careful - the original op-amps were 741 vintage and the current crop of op-amps are sure to oscillate without necessary provisions.
Joe,
Thank you....more real good information!
Do you know what are the electrical characteristics of the panels..the load...that the amp is trying to drive? I assumed that someone must have characterized them. Does it make more sense to do what SY is doing...design from the ground up and hopefully be able to obtain parts a little easier?
I have to confess that I love my 'stats. the combination of the NAK mics in and the Acoustats out were wonderful when I was doing live recording and during that time I was exclusively using the III's. It may be irrational but I definitley wan to get back to just that...Tube driven Acoustats...preferably another set of III's.
I appreciate your sharing your expertise.
rt
Thank you....more real good information!
Do you know what are the electrical characteristics of the panels..the load...that the amp is trying to drive? I assumed that someone must have characterized them. Does it make more sense to do what SY is doing...design from the ground up and hopefully be able to obtain parts a little easier?
I have to confess that I love my 'stats. the combination of the NAK mics in and the Acoustats out were wonderful when I was doing live recording and during that time I was exclusively using the III's. It may be irrational but I definitley wan to get back to just that...Tube driven Acoustats...preferably another set of III's.
I appreciate your sharing your expertise.
rt
Do you know what are the electrical characteristics of the panels..the load...that the amp is trying to drive? I assumed that someone must have characterized them. Does it make more sense to do what SY is doing...design from the ground up and hopefully be able to obtain parts a little easier?
I did have the panel info at one time but after two moves including one cross country move, those documents became one of the data loss casulities of the moving company. But the panels bias at 5KV. If I were designing an amp from scratch I'd use the original output stage but set it up with PL-509's. Establish the bias operating points and insert a fixed or auto bias circuit. You can then cap couple a reasonably good push pull driver stage (e.g. tube) into it.
Getting parts may prove to be difficult - high quality HV C's and R's are not plentiful on the DIY market.
I did have the panel info at one time but after two moves including one cross country move, those documents became one of the data loss casulities of the moving company. But the panels bias at 5KV. If I were designing an amp from scratch I'd use the original output stage but set it up with PL-509's. Establish the bias operating points and insert a fixed or auto bias circuit. You can then cap couple a reasonably good push pull driver stage (e.g. tube) into it.
Getting parts may prove to be difficult - high quality HV C's and R's are not plentiful on the DIY market.
rt: Part 1 (The Frames) will get posted in the next few days. The DD amp may take a little longer; as Joe points out, parts acquisition is always an issue, though the surplus ham market can be quite rewarding. My goal is to use easy-to-get and reliable stuff as much as possible.
Joe: I sympathize. As many cross-country moves as I've made, I must have left quite a trail of papers and books. I have in mind a rather different output stage loading than the original (or that I've seen before). Is there any chance you'd be willing to discuss it privately with me and critique it before I publish?
BTW, we did cross paths many years ago, through the graces of Murray Zeligman. I'm still using some of the regulator boards you designed at that time, with FET current sources pulling across a resistor as the voltage reference.
Joe: I sympathize. As many cross-country moves as I've made, I must have left quite a trail of papers and books. I have in mind a rather different output stage loading than the original (or that I've seen before). Is there any chance you'd be willing to discuss it privately with me and critique it before I publish?
BTW, we did cross paths many years ago, through the graces of Murray Zeligman. I'm still using some of the regulator boards you designed at that time, with FET current sources pulling across a resistor as the voltage reference.
Murray's place was where you would run across anyone and everyone. Dave Berning, Ike Eisenson, Tony Cordesman, Allen Edelstein, Gordon Holt, Lew Johnson... Though our philosophies and paths have diverged, the years I spent working with him were incredibly valuable. I've heard some of the Nova speakers he's designed recently and I have to say he hasn't lost his touch.
Joe: I sympathize. As many cross-country moves as I've made, I must have left quite a trail of papers and books. I have in mind a rather different output stage loading than the original (or that I've seen before). Is there any chance you'd be willing to discuss it privately with me and critique it before I publish?
Sure. I notice you're in Napa Valley - I'm in the South Bay. Just show up (call ahead) with a bottle or two of a fine Merlot and we can discuss your design all day. Or just feel free to call anytime.
Murray's place was where you would run across anyone and everyone. Dave Berning, Ike Eisenson, Tony Cordesman, Allen Edelstein, Gordon Holt, Lew Johnson... Though our philosophies and paths have diverged, the years I spent working with him were incredibly valuable. I've heard some of the Nova speakers he's designed recently and I have to say he hasn't lost his touch
I haven't seen Murray in about 10 years - maybe more. Nonetheless, I have never met anyone that had both his vast knowledge and ability to think beyond any biases. Murray was open to any approach. He never got bogged down with "the perfect component" (e.g. brand A magic capacitor) or single "best circuit topology" (e.g. SSRP). All components are imperfect, some more than others, but the best are only variations on a theme. He had a profound impact on my work and opened my thinking to recognize that the most musically successful and enjoyable designs deploy not only well engineered topologies but need to be supported with carefully chosen components to achieve the most truthful and musical result.
Sure. I notice you're in Napa Valley - I'm in the South Bay. Just show up (call ahead) with a bottle or two of a fine Merlot and we can discuss your design all day. Or just feel free to call anytime.
Murray's place was where you would run across anyone and everyone. Dave Berning, Ike Eisenson, Tony Cordesman, Allen Edelstein, Gordon Holt, Lew Johnson... Though our philosophies and paths have diverged, the years I spent working with him were incredibly valuable. I've heard some of the Nova speakers he's designed recently and I have to say he hasn't lost his touch
I haven't seen Murray in about 10 years - maybe more. Nonetheless, I have never met anyone that had both his vast knowledge and ability to think beyond any biases. Murray was open to any approach. He never got bogged down with "the perfect component" (e.g. brand A magic capacitor) or single "best circuit topology" (e.g. SSRP). All components are imperfect, some more than others, but the best are only variations on a theme. He had a profound impact on my work and opened my thinking to recognize that the most musically successful and enjoyable designs deploy not only well engineered topologies but need to be supported with carefully chosen components to achieve the most truthful and musical result.
Hi all again,
I just asked for a schematic, I didn't hope to generate a so exciting and impressive discussion. It seems to me that a so deep knowledge and experience should not be losen, but it could be useful and beautiful to collect it and to share it with less expert people, like me, for instance.
I'd like to promote a challenge, whose results could be very interesting to a lot of people. Here it is. By your very deep experience, why not design and project a complete system (amp + ESL ), "state of the art", sharing all your knowledge and suggestions? It is my opinion the results could be amazing.
By the way (this is for everybody reading, but especially for SY), my area is full of delicious wines (red like Merlot, Cabernet, Franconia, Pinot, etc.; white like Tokaj, Riesling, Traminer, Pinot, etc.). If you want I try to organize a special ESL convention, here I am at disposal.
Cheers
Milo
I just asked for a schematic, I didn't hope to generate a so exciting and impressive discussion. It seems to me that a so deep knowledge and experience should not be losen, but it could be useful and beautiful to collect it and to share it with less expert people, like me, for instance.
I'd like to promote a challenge, whose results could be very interesting to a lot of people. Here it is. By your very deep experience, why not design and project a complete system (amp + ESL ), "state of the art", sharing all your knowledge and suggestions? It is my opinion the results could be amazing.
By the way (this is for everybody reading, but especially for SY), my area is full of delicious wines (red like Merlot, Cabernet, Franconia, Pinot, etc.; white like Tokaj, Riesling, Traminer, Pinot, etc.). If you want I try to organize a special ESL convention, here I am at disposal.
Cheers
Milo
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.