Uncertainties
The guy who worked on my interface may have already replaced those capacitors. He mentioned he had been in touch with the best experts he could find and 'they' had suggested certain items were the most likely problem. He showed me the ones he took out of my unit, and my recollection is that they looked a lot like the illustrations of the Vishay 564R30TSD33 capacitor. There may have been five of them. So it seems strange that they would be going bad again while the ones in the other unit have no audible problem.
Interestingly, we had a few days of tropical weather over the weekend, so I closed up the house and turned on the A/C. I had previously had to turn the balance control on my pre-amp well to the left along with turning up the volume to get a good, balanced output. This morning, I put on a CD and found the music was not only way too loud but badly skewed to the left. I had to adjust the volume down and the balance control considerably back toward the middle in order to regain proper balance and dynamics. This is in the context of fairly stable performance through the winter months followed by progressive deterioration of output in the left speaker as the weather became warm and humid in June.
As mentioned previously, this is the third summer I've had this problem with that same interface unit. Last year I swapped it from the right speaker to the left one, changed nothing else, and found the problem had moved from the right speaker to the left one. It's hard to believe the guy I took that interface to would have neglected to clean the board if it was obviously dirty, and the problem seems exactly the same as before he worked on it. He had that interface for more than three months. It worked OK when I got it back, but it was already well into autumn by then, and his shop is air-conditioned. He told me he wasn't equipped to measure the device's output because of the energies involved, so he was flying blind. Under the circumstances, I'm not eager to take it back to him (if he's even still in business).
Sure wish there was somebody with the skills and availability to really diagnose this problem; shipping the interface unit would not be a big deal in this context.
The guy who worked on my interface may have already replaced those capacitors. He mentioned he had been in touch with the best experts he could find and 'they' had suggested certain items were the most likely problem. He showed me the ones he took out of my unit, and my recollection is that they looked a lot like the illustrations of the Vishay 564R30TSD33 capacitor. There may have been five of them. So it seems strange that they would be going bad again while the ones in the other unit have no audible problem.
Interestingly, we had a few days of tropical weather over the weekend, so I closed up the house and turned on the A/C. I had previously had to turn the balance control on my pre-amp well to the left along with turning up the volume to get a good, balanced output. This morning, I put on a CD and found the music was not only way too loud but badly skewed to the left. I had to adjust the volume down and the balance control considerably back toward the middle in order to regain proper balance and dynamics. This is in the context of fairly stable performance through the winter months followed by progressive deterioration of output in the left speaker as the weather became warm and humid in June.
As mentioned previously, this is the third summer I've had this problem with that same interface unit. Last year I swapped it from the right speaker to the left one, changed nothing else, and found the problem had moved from the right speaker to the left one. It's hard to believe the guy I took that interface to would have neglected to clean the board if it was obviously dirty, and the problem seems exactly the same as before he worked on it. He had that interface for more than three months. It worked OK when I got it back, but it was already well into autumn by then, and his shop is air-conditioned. He told me he wasn't equipped to measure the device's output because of the energies involved, so he was flying blind. Under the circumstances, I'm not eager to take it back to him (if he's even still in business).
Sure wish there was somebody with the skills and availability to really diagnose this problem; shipping the interface unit would not be a big deal in this context.
You can try contacting Roy Esposito in Florida. acoustat.service.usa@gmail.com. Roy is a former Acoustat employee from before my time with the company. So I don't know Roy, and cannot personally vouch for his work, but I have heard good reports on his work. Be patient - this is a part-time endeavor for Roy and he may not respond immediately.
That does make sense as a ballpark figure. Looking at the schematic I have I see there is some segmentation, so the second segment is isolated by 300k or so.
Another issue is the parasitic cap of the heater supply of the top tube of the SRPP (like) circuit. That can easily be another 100pF and for the amp looks like a load to ground through the heater-cathode capacitance.
I think.
Jan
Another issue is the parasitic cap of the heater supply of the top tube of the SRPP (like) circuit. That can easily be another 100pF and for the amp looks like a load to ground through the heater-cathode capacitance.
I think.
Jan
The capacitance of the Acoustat speakers vary considerably depending on whether you are talking about the older series(which drive panels uniformly) or newer Spectra series with divided the panels which drove different sections thru increasing resistance depending on how many panels the model had. If you are interested in a particular model, let me know and I can get you a schematic and more details.
- For the older series, the panels are roughly 400pF. So a Model 1 was 400pF. A Model 2 or Model 1+1 was 800pF. The Model 2+2 was 1600pF etc… Some of the models like the 3 and 4 did use slightly narrow panels that were about 350pF instead of 400pF for central panel(s).
- For the newer Spectra series, only half of one panel(200pF) is directly driven from the transformer for the single height models like Spectra 11, 22, 33. The double height models like 44 & 66 had two of these sections in parallel, so 400pF directly driven from the transformer. All other panels have some resistance in series with them.
Note also that all the Acoustat interfaces and amplifiers have EQ built in to boost the bass by as much as +15dB to equalize the dipole roll-off. There is also a boost in the top octave to correct the roll-off from diaphragm mass. (see links below for more details)
Open CLS II stators - the best way to do it?
All Acoustat panels can give
- For the older series, the panels are roughly 400pF. So a Model 1 was 400pF. A Model 2 or Model 1+1 was 800pF. The Model 2+2 was 1600pF etc… Some of the models like the 3 and 4 did use slightly narrow panels that were about 350pF instead of 400pF for central panel(s).
- For the newer Spectra series, only half of one panel(200pF) is directly driven from the transformer for the single height models like Spectra 11, 22, 33. The double height models like 44 & 66 had two of these sections in parallel, so 400pF directly driven from the transformer. All other panels have some resistance in series with them.
Note also that all the Acoustat interfaces and amplifiers have EQ built in to boost the bass by as much as +15dB to equalize the dipole roll-off. There is also a boost in the top octave to correct the roll-off from diaphragm mass. (see links below for more details)
Open CLS II stators - the best way to do it?
All Acoustat panels can give
Here's my attempt to set up a sim for the Acoustat direct drive amp. The stability very much depends on C9, the AC feedback cap. In the original schematic it is 4.7pF but of course there are parasitic capacitances in the real thing that also impact this.
I did notice that the response falls off after 8k or so.
Delete .txt on the asy file name.
Have fun!
Jan
I did notice that the response falls off after 8k or so.
Delete .txt on the asy file name.
Have fun!
Jan
Hello everyone.
I need to find 4/6 6HB5 valves (Servo Acoustat Monitor 4), the problem is that I am in Italy and each valve costs me a total of 30/40 euros cost + shipping + duty.
Someone could get me 4/6 6HB5 and send me a single shipment (of course I would pay all expenses in advance)
Thank you all.
I need to find 4/6 6HB5 valves (Servo Acoustat Monitor 4), the problem is that I am in Italy and each valve costs me a total of 30/40 euros cost + shipping + duty.
Someone could get me 4/6 6HB5 and send me a single shipment (of course I would pay all expenses in advance)
Thank you all.
I got similar tubes, 6HS5, from Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes! at $ 7 each with $ 20 shipping. Ask for Dale.
Jan
Jan