Well done, this is useful input for those of us contemplating similar action. I would be particularly interested to know what you chose to replace the main rectifiers and the side board rectifiers with. Will also post some comments on your blog.
The main rectifiers are 36MB80A
http://gr.mouser.com/ProductDetail/Vishay-Semiconductors/VS-36MB80A/?qs=CDqwynd4ZNrHFe0BvPgjyQ==
For the side boards
http://gr.mouser.com/Search/ProductDetail.aspx?R=RC206virtualkey58300000virtualkey583-RC206
Hope that helps
http://gr.mouser.com/ProductDetail/Vishay-Semiconductors/VS-36MB80A/?qs=CDqwynd4ZNrHFe0BvPgjyQ==
For the side boards
http://gr.mouser.com/Search/ProductDetail.aspx?R=RC206virtualkey58300000virtualkey583-RC206
Hope that helps
I recently bought a lightly-used HCA2200 II and I am wondering if there are any companies like Big Sky that are doing the modifications noted.
I might can do the mods myself but I am not an electrical guru like most of you guys so I would likely need a lot of hand holding to get it done myself.
I might can do the mods myself but I am not an electrical guru like most of you guys so I would likely need a lot of hand holding to get it done myself.
Regarding the R125 resister, I was unable to locate any of the old HOLCO resistors that John Curl noted but I did find some of these:
Roederstein (ERO) MK3 1R~10M 0.5W 1% Metal Film Resistor (Vishay, NOS)
I am pretty sure this is the one that John Curl recommends as a replacement so I bought a dozen of them from overseas and they should be here in January.
Now regarding all those film caps...........There is a guy in Greece that posted his mods to a 2200 II on the whatishifi blog but it seems to me that he quoted from John Curl for mods to both the 3500 and the 2200 II in his 2200II mod which has me just a little confused: There are a LOT of the white film capacitors in the 2200II. Some appear to be in parallel to other capacitors (board B1420) and not even specified in the schematic but most of them are actually in the original specs and there is even a place for those on the board (B1421). So I can see why the ones that are piggybacked in parallel onto other caps might can simply be cut out as being superfluous, but I wonder about all those on top.
On my unit in particular, it looks fantastic on the inside. There are no leaking caps or other repairs needed. So I am thinking of just replacing the R125 resistor and cutting out all those redundant film caps. These 2 mods seem fairly straightforward as long as I know which film caps I should be removing and which I should be removing and replacing with others.
I already have the 2200II in my system replacing an HCA1500A and I can say it already was a big improvement over the HCA1500A.
Any help is greatly appreciated.
Will
Roederstein (ERO) MK3 1R~10M 0.5W 1% Metal Film Resistor (Vishay, NOS)
I am pretty sure this is the one that John Curl recommends as a replacement so I bought a dozen of them from overseas and they should be here in January.
Now regarding all those film caps...........There is a guy in Greece that posted his mods to a 2200 II on the whatishifi blog but it seems to me that he quoted from John Curl for mods to both the 3500 and the 2200 II in his 2200II mod which has me just a little confused: There are a LOT of the white film capacitors in the 2200II. Some appear to be in parallel to other capacitors (board B1420) and not even specified in the schematic but most of them are actually in the original specs and there is even a place for those on the board (B1421). So I can see why the ones that are piggybacked in parallel onto other caps might can simply be cut out as being superfluous, but I wonder about all those on top.
On my unit in particular, it looks fantastic on the inside. There are no leaking caps or other repairs needed. So I am thinking of just replacing the R125 resistor and cutting out all those redundant film caps. These 2 mods seem fairly straightforward as long as I know which film caps I should be removing and which I should be removing and replacing with others.
I already have the 2200II in my system replacing an HCA1500A and I can say it already was a big improvement over the HCA1500A.
Any help is greatly appreciated.
Will
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Hoping this thread is not dead but it is beginning to appear so ....
I have seen some mods from others where they have removed all of the film caps from the power boards (B1421 l/r) and did not replace them with anything - just left the boards empty. I have also seen where others have replaced them with 1 cap of the same total value as the ones removed and then I saw another mod where only 2 were left on the board. Then I read Big Sky Audio's upgrade mod sheet and they went a completely different direction and removed them all and replaced them with just 2 resistors!
Being a novice here I am guessing that the film caps have something to do with noise reduction and JC recommends removing most of them but what is the best course of action: Remove them all, remove only some (which ones?), replace with same total value?
Also, does anyone have an opinion as to why Big Sky Audio recommends replacing them with 2 resistors (YAGEO, ES 5.6 OHM 5% 2W AXIAL, metal oxide) instead of capacitors?
Thanks.
I have seen some mods from others where they have removed all of the film caps from the power boards (B1421 l/r) and did not replace them with anything - just left the boards empty. I have also seen where others have replaced them with 1 cap of the same total value as the ones removed and then I saw another mod where only 2 were left on the board. Then I read Big Sky Audio's upgrade mod sheet and they went a completely different direction and removed them all and replaced them with just 2 resistors!
Being a novice here I am guessing that the film caps have something to do with noise reduction and JC recommends removing most of them but what is the best course of action: Remove them all, remove only some (which ones?), replace with same total value?
Also, does anyone have an opinion as to why Big Sky Audio recommends replacing them with 2 resistors (YAGEO, ES 5.6 OHM 5% 2W AXIAL, metal oxide) instead of capacitors?
Thanks.
Not all mods are improvements. A lot of them are well meaning, but based on superstition, someone else said so, or well intended uninformed guess. And some are brilliant! It helps to filter bright ideas through a Spice model and background reading of Cordell, Self, Curl, Pass, Didden... A lot of what causes a sonic signature is not easy to model. The experience of the masters counts. Hints on quality of parts is a good example.
Then, are you trueing to tune a sonic signature, or eliminate one? That is not an easy question! Some may want it to be as clean as a Benchmark, others may want to upset the LTB balance and boost even order harmonics. To each their own.
My SOP these days is to swap the main filter caps with banks of smaller caps. It is a tossup if one should isolate each cluster form the other channel. What I am going to try is 4 caps on each rail, the first two common to both channel rails, the second two isolated. So the transformer sees the same load, but some isolation between channels. Maybe crazy, but easy to try. Of course, in my little amp, I have 3 times the capacitance so a bigger rectifier. To increase the caps in the 2200 you might need a soft start. I also put a pi-filter on the rails feeding the VAS and IPS. I forget how the 2200 was wired. Anyway, in my MOSFET, I get 1/8 the ripple for the same DC drop to the low power stage. As it is a toroid main, I might add an internal DC blocking to the power line and a little of filtering. If you were to double the bank, separating the first half with a couple ohms will reduce line ripple a ton but may not help ripple from the audio as much as a bigger lower ESR bank.
If you want to start an argument, bring up snubbers.
In retrospect, I wish I had kept my 2200's. They were very very good amps. But I did not need monsters any more so I switched to a modified Hafler 120 (modifications from some insightful hints from John) Years went buy and the old MOSFET started humming along with the music, so I bought a new 2125. What a huge mistake. So re-capping the Hafler and just spent a week with LTSpice re-evaluating the Bode plot and ratios of local vs global feedback. I converted it to Miller compensation last time, but will be going to two pole now. Even better stability margin and lower HF distortion. On paper at least. Then I might pop open the "new classic" and see what is so harsh. It did get better burned in, but still pretty bad. Hope I can find a schematic as drawing one is a PITA.
I don't know what Big Sky is up to, but I am a firm believer in cascading caps to where the draw is. In the digital world, we but a bypass as close to the transistor( chip) that is drawing power. Then a bigger cap at the end of the row to re-supply the smaller bypass. A bigger one where the power feeds th aboard to recharge the rows, and of course, the main filter caps wherever the supply is. The goal is to minimize parasitic impedances between the bypass caps and the transistor. I see no reason this does not apply to analog, though the transients are not as abrupt. ( except the outputs). The app guides from National etc., talk a lot about that in their op-amp guides.
Bummer is, don't break it. I don't think you can get some of the good parts like the input FETs. They are very ESD sensitive so beware.
I have never seen any machine I could not figure out how to tweak.
Then, are you trueing to tune a sonic signature, or eliminate one? That is not an easy question! Some may want it to be as clean as a Benchmark, others may want to upset the LTB balance and boost even order harmonics. To each their own.
My SOP these days is to swap the main filter caps with banks of smaller caps. It is a tossup if one should isolate each cluster form the other channel. What I am going to try is 4 caps on each rail, the first two common to both channel rails, the second two isolated. So the transformer sees the same load, but some isolation between channels. Maybe crazy, but easy to try. Of course, in my little amp, I have 3 times the capacitance so a bigger rectifier. To increase the caps in the 2200 you might need a soft start. I also put a pi-filter on the rails feeding the VAS and IPS. I forget how the 2200 was wired. Anyway, in my MOSFET, I get 1/8 the ripple for the same DC drop to the low power stage. As it is a toroid main, I might add an internal DC blocking to the power line and a little of filtering. If you were to double the bank, separating the first half with a couple ohms will reduce line ripple a ton but may not help ripple from the audio as much as a bigger lower ESR bank.
If you want to start an argument, bring up snubbers.
In retrospect, I wish I had kept my 2200's. They were very very good amps. But I did not need monsters any more so I switched to a modified Hafler 120 (modifications from some insightful hints from John) Years went buy and the old MOSFET started humming along with the music, so I bought a new 2125. What a huge mistake. So re-capping the Hafler and just spent a week with LTSpice re-evaluating the Bode plot and ratios of local vs global feedback. I converted it to Miller compensation last time, but will be going to two pole now. Even better stability margin and lower HF distortion. On paper at least. Then I might pop open the "new classic" and see what is so harsh. It did get better burned in, but still pretty bad. Hope I can find a schematic as drawing one is a PITA.
I don't know what Big Sky is up to, but I am a firm believer in cascading caps to where the draw is. In the digital world, we but a bypass as close to the transistor( chip) that is drawing power. Then a bigger cap at the end of the row to re-supply the smaller bypass. A bigger one where the power feeds th aboard to recharge the rows, and of course, the main filter caps wherever the supply is. The goal is to minimize parasitic impedances between the bypass caps and the transistor. I see no reason this does not apply to analog, though the transients are not as abrupt. ( except the outputs). The app guides from National etc., talk a lot about that in their op-amp guides.
Bummer is, don't break it. I don't think you can get some of the good parts like the input FETs. They are very ESD sensitive so beware.
I have never seen any machine I could not figure out how to tweak.
In case anyone else intends to modify their 2200II, I decided to follow John Curl's recommendations.
1. The "majority" of the film capacitors on the B1421 power boards (1421L and 1421R) can be removed.
I removed all caps from C510/C515(C610-C615), C516-C521(C616-C621) and C522-C527(C622-C627) - total of 24 caps with total capacitance of 1.02 K per channel..
I left C528(C628) and C529(C629) on the board - these 2 per board have a total capacitance of .44 K. I also left the 2 caps at C508-C509(C608-C609) on the board.
I installed 1 each Nichicon QXK series (1uF) film cap at C527 (C627).
Note that I have seen where others did not install anything - and I even saw where 1 mod done left C522 & C527 on the board.
2. Remove the "tacked on" or "paralleled" caps on the B1420 input board.
I removed all of the "tacked on" film caps on C117-C118 (C227-228), C122-C125 (C222-C225) - a total of 12 caps with total capacitance of .24 K
Note that I left all of the underlying cylindrical caps at these locations on the boards - I think this is what John Curl meant when he said "leave one at each board location".
3. The last suggestion that he had was to make sure the feedback resistors at R125(R225) are Resista or Holco "old". My 2200II appears to already have the old Holco installed from the factory. I saw a 1990s advertisement when Parasound was marketing this amp that said "Precision 1% tolerance Holco and Resista metal film resistors" were used so I am just guessing that at some point perhaps the factory starting to substitute other types? Hence the suggestion by JC to check this particular important one. It wouldn't surprise me that the factory did this - after seeing the fairly sloppy craftsmanship inside this particular amp.
So, if anyone is counting, I removed a total of 36 caps! Yikes.
Listening tests to follow and I have pics that I can post if anyone wants them.
1. The "majority" of the film capacitors on the B1421 power boards (1421L and 1421R) can be removed.
I removed all caps from C510/C515(C610-C615), C516-C521(C616-C621) and C522-C527(C622-C627) - total of 24 caps with total capacitance of 1.02 K per channel..
I left C528(C628) and C529(C629) on the board - these 2 per board have a total capacitance of .44 K. I also left the 2 caps at C508-C509(C608-C609) on the board.
I installed 1 each Nichicon QXK series (1uF) film cap at C527 (C627).
Note that I have seen where others did not install anything - and I even saw where 1 mod done left C522 & C527 on the board.
2. Remove the "tacked on" or "paralleled" caps on the B1420 input board.
I removed all of the "tacked on" film caps on C117-C118 (C227-228), C122-C125 (C222-C225) - a total of 12 caps with total capacitance of .24 K
Note that I left all of the underlying cylindrical caps at these locations on the boards - I think this is what John Curl meant when he said "leave one at each board location".
3. The last suggestion that he had was to make sure the feedback resistors at R125(R225) are Resista or Holco "old". My 2200II appears to already have the old Holco installed from the factory. I saw a 1990s advertisement when Parasound was marketing this amp that said "Precision 1% tolerance Holco and Resista metal film resistors" were used so I am just guessing that at some point perhaps the factory starting to substitute other types? Hence the suggestion by JC to check this particular important one. It wouldn't surprise me that the factory did this - after seeing the fairly sloppy craftsmanship inside this particular amp.
So, if anyone is counting, I removed a total of 36 caps! Yikes.
Listening tests to follow and I have pics that I can post if anyone wants them.
Hi. I'm a retired engineer, and I already did numerous upgrades to Parasound amps. My upgrade goes far beyond the description above. First, all caps are Nichicon audio grade. I replace all film caps with Wima mkp. I replace resistors in the music path with high-end prp pr9372. And, I replace all bridge rectifiers, both in driver stage and main power supplies to ultrafast/soft recovery, higher voltage and amperage type of rectifiers. If interested in that upgrade txt me to 786-751-1189.
You get a better soundstage, clearer, more separated sound, better resolution and wider sounds Tage
You get a better soundstage, clearer, more separated sound, better resolution and wider sounds Tage
concerning ultra fast/soft recovery rectifiers check out this URLs:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwinlKS9r52FAxV27LsIHcF9A9kQFnoECBAQAQ&url=https://www.diyaudio.com/community/attachments/quasimodo_jig_reva-pdf.373155/&usg=AOvVaw1m8lRqZhALOjXNigBGRVpA&opi=89978449
https://www.diyaudio.com/community/...rmer-snubber-using-quasimodo-test-jig.243100/
https://www.desmith.net/NMdS/Data/Linear Audio - Soft Recovery Diodes Lower Transformer Ringing by 10-20X.pdf
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwinlKS9r52FAxV27LsIHcF9A9kQFnoECBAQAQ&url=https://www.diyaudio.com/community/attachments/quasimodo_jig_reva-pdf.373155/&usg=AOvVaw1m8lRqZhALOjXNigBGRVpA&opi=89978449
https://www.diyaudio.com/community/...rmer-snubber-using-quasimodo-test-jig.243100/
https://www.desmith.net/NMdS/Data/Linear Audio - Soft Recovery Diodes Lower Transformer Ringing by 10-20X.pdf