DarqueKnight
07-24-2006, 06:48 PM
The FedEx man delivered my Parasound JC1 monoblock amps early this morning. For a while, I have been looking for something with more power and current drive. The Adcom GFA-5802, which has been my reference amp for the past five years, is no slouch in either area. But, you know, a true audiophile is never really satisfied. False audiophiles aren't that much better either. There is always something bigger, better, faster, and MORE.
My search was complicated by the fact that many of the higher powered amps (above 300 watts per channel) are bridged designs where both outputs are "live" (i.e., the negative speaker terminal is not at ground potential, but is an inverted version of the positive speaker terminal). To use such an amplifier, I would need to use an AI-1 isolation transformer, which I really did not want to do for three reasons: (1) I did not want to go to the trouble of constucting one, (2) I did not want to put another device, even a passive one, in my audio chain, and most importantly, (3) SDA's are really not designed to be isolated from each other. The AI-I is a "workaround" which defies the original design intent of the speakers. Moreover, some users of the AI-1 have said that it slightly diminished detail and some users have said that they heard no difference when the AI-1 was used. I didn't want to go to the trouble of purchasing an amplifier that required use of the AI-1 and then find that the isolation transformer was "choking" my SDA's.
The wish list for my next power amplifier consisted of:
1. "Neutral" sound character.
2. Balanced (XLR) inputs.
3. Output power of at least 500 watts per channel into 8 ohms. (GFA-5802 is 300 watts per channel into 8 ohms, JC1's are 400 watts per channel into 8 ohms.)
4. True current source capability, meaning the power "doubles down" or doubles with every halving of the speaker impedance.
5. Hybrid solid state design with MOSFET transistors in the drive stage and Bipolar transistors in the output stage. I prefer the way these devices reproduce the type of music I most frequently listen to (acoustic jazz). I like the midrange and treble characteristics of MOSFET's. I like the bass "slam" of Bipolars.
6. Bias at class A operation of at least the first 20 watts before switching to class AB operation.
7. Linear damping factor of at least 300. (GFA-5802 is 1000, JC1's are 1200).
8. Common ground design or, if not common ground, capable of having the negative channels connected together in a common ground configuration.
9. Premium parts and build quality.
10. A reputable, stable company with good customer service.
The JC1 met all of my design criteria except, maybe, for #3. However, my initial feeling is that I may be able to "get by" with only the JC1's 400 watts into 8 ohms. Although, I may actually be getting 600 watts per channel because I suspect that my SDA SRS 1.2TL's are actually closer to 6 ohms impedance rather than 8 ohms. If my suspicion is true, then the JC1's actually meet all of my criteria.:) The 1.2TL's specs state that their impedance is "compatible with 8 ohm outputs" ;). I was never able to pin Polk down on exactly what "compatible with 8 ohm outputs" really means, although I have some theories.
The JC1 is very close to what I would design for myself if I ever took the time to do it. (Someday?:) )
Operation
I had some concern about the JC1's heat generation that I had read about in several reviews. The Adcom GFA-5802 is a virtual space heater and I was not looking to have two space heaters in my living room. I called Parasound and was told that the heat sinks get up to a little over 100 degrees under moderately high listening levels. The Adcom heat sinks get up to 112 degrees under moderately high listening levels (average 90 dB), therefore I was not concerned about the heat issue. After playing for three hours at an average 90 dB, the left JC1 had a heat sink temperature of 101 degrees and the right JC1 had a heat sink temperature of 103 degrees (temperatures taken with digital thermometers). Sweet...I get more power with a little less heat generation. The JC1's probably use a better heat dissipation mechanism.
I made two 4-foot ground terminal strapping cables since the JC1's have two sets of binding posts (for biwiring). The strapping cables were made of some spare DSR Silverline 10 gauge speaker cable. One cable, which connects the unused negative binding post terminals, is terminated in Monster X-Terminator locking banana connectors. The other cable, which connects the negative binding posts that each speaker is connected to, is terminated by regular Monster bananas for quick release when removing speaker cables. It was not necessary to use two binding post strapping cables, since the binding posts of each JC1 are in parallel. I just like overkill.
Performance
Those of you who have been reading me for a while know that I favor audio components that have high price/performance ratios. Above a certain price point, you reach the point of diminishing returns where there is not a linear relationship between additional cost and additional performance. You end up paying a lot for a little more performance improvement. The JC1 pair, with an MSRP of $7000, is 3.5 times the $2000 MSRP of the Adcom GFA-5802. So....are the JC1's 3.5 times better than the GFA-5802's? No. No way, buster. I would subjectively say they are twice as good and are well worth the price they can be had for on the used market.
The Sound
The Adcom GFA-5802 is in no way "shamed" by the JC1 monoblocks. The GFA-5802 is a great design and gives me everything I like in an amplifer. However, the JC1's give me MORE of everything: More bass slam, more holographic 3-dimensional sound, more clarity, more details. There was no difference between the soundstage dimensions thrown by the GFA-5802 and the JC1's, nor was there a difference in the placement of instruments and sounds within the soundstage. There was a big difference in the "solidity" and clarity of instruments and sounds within the soundstage. The bass notes of the JC1's hit harder, although they measured no louder on a sound meter. There was more of a sense of real people playing in the room. I could also hear more reverberant artifacts of the recording space with the JC1's.
Using "Tiptoes" aluminum isolation cones under the JC1 made no audible difference like it did with the GFA-5802. I may leave them there because it allows more air to get under the amps, plus, it raises them up so that the cool blue light behind the power switch is not obscured behind the audio cabinet doors.
To sum it up: The Adcom GFA-5802 kicks ass, but the JC1's kick natural ass.("Natural" is pronounced nat'-Chul.)
I will provide a more detailed quantitative listening analysis after I have lived with the JC1's for a few weeks.
What I Do Not Like About the JC1's
1. The heat. They don't run as hot as the Adcom, but since I have two of them, the cumulative heat is a little bit more. Fortunately, I do not get a lot of heat buildup in my audio cabinet because there are 5.5 inches of clearance above each JC1 and the cabinet doors and side panels are steel mesh. The cabinet back is open.
2. Those DAMN PLASTIC BINDING POST NUTS. Really, what were they thinking? Why couldn't I have some nice Cardas or at least some sturdy Vampire all metal posts? Is that really too much to ask of an amplifier of this quality? Was that much money saved by using the cheapie binding posts? I'll certainly be changing those out soon. I always keep a bunch of nice Cardas and Vampire posts around just for such situations.
Further Thoughts
The Adcom GFP-750 preamp is staying in the system for the time being. I like it a lot because it sounds like.....nothing. I'll probably get a nice SACD player, once there are more than two or three SACD titles I'd like to own. For now, my well modified Sony CDP-XA7ES CD player serves well, especially after the power cord, the master clock, and a couple of cheap op amps in the balanced output section were replaced with much higher quality parts. I have no desire to sell the GFA-5802 and it is going on reserve duty. Eventually, I'll get around to applying the tweaks that I have read about on various other audio forums (yeah, sure).
The FedEx man is bringing me a turntable and phono preamp tomorrow morning. My love/hate relationship with vinyl continues. I don't listen to records a lot, but I have a lot of obscure recordings that are not and probably never will be on CD, so I'm stuck. We'll see if the Music Hall MMF-9 is able to retire my beloved modified Yamaha PF-800 turntable that I have used for the past 17 years. I suffer from upgradeitis like many others, but I think I manage it rather well.
More later.
My search was complicated by the fact that many of the higher powered amps (above 300 watts per channel) are bridged designs where both outputs are "live" (i.e., the negative speaker terminal is not at ground potential, but is an inverted version of the positive speaker terminal). To use such an amplifier, I would need to use an AI-1 isolation transformer, which I really did not want to do for three reasons: (1) I did not want to go to the trouble of constucting one, (2) I did not want to put another device, even a passive one, in my audio chain, and most importantly, (3) SDA's are really not designed to be isolated from each other. The AI-I is a "workaround" which defies the original design intent of the speakers. Moreover, some users of the AI-1 have said that it slightly diminished detail and some users have said that they heard no difference when the AI-1 was used. I didn't want to go to the trouble of purchasing an amplifier that required use of the AI-1 and then find that the isolation transformer was "choking" my SDA's.
The wish list for my next power amplifier consisted of:
1. "Neutral" sound character.
2. Balanced (XLR) inputs.
3. Output power of at least 500 watts per channel into 8 ohms. (GFA-5802 is 300 watts per channel into 8 ohms, JC1's are 400 watts per channel into 8 ohms.)
4. True current source capability, meaning the power "doubles down" or doubles with every halving of the speaker impedance.
5. Hybrid solid state design with MOSFET transistors in the drive stage and Bipolar transistors in the output stage. I prefer the way these devices reproduce the type of music I most frequently listen to (acoustic jazz). I like the midrange and treble characteristics of MOSFET's. I like the bass "slam" of Bipolars.
6. Bias at class A operation of at least the first 20 watts before switching to class AB operation.
7. Linear damping factor of at least 300. (GFA-5802 is 1000, JC1's are 1200).
8. Common ground design or, if not common ground, capable of having the negative channels connected together in a common ground configuration.
9. Premium parts and build quality.
10. A reputable, stable company with good customer service.
The JC1 met all of my design criteria except, maybe, for #3. However, my initial feeling is that I may be able to "get by" with only the JC1's 400 watts into 8 ohms. Although, I may actually be getting 600 watts per channel because I suspect that my SDA SRS 1.2TL's are actually closer to 6 ohms impedance rather than 8 ohms. If my suspicion is true, then the JC1's actually meet all of my criteria.:) The 1.2TL's specs state that their impedance is "compatible with 8 ohm outputs" ;). I was never able to pin Polk down on exactly what "compatible with 8 ohm outputs" really means, although I have some theories.
The JC1 is very close to what I would design for myself if I ever took the time to do it. (Someday?:) )
Operation
I had some concern about the JC1's heat generation that I had read about in several reviews. The Adcom GFA-5802 is a virtual space heater and I was not looking to have two space heaters in my living room. I called Parasound and was told that the heat sinks get up to a little over 100 degrees under moderately high listening levels. The Adcom heat sinks get up to 112 degrees under moderately high listening levels (average 90 dB), therefore I was not concerned about the heat issue. After playing for three hours at an average 90 dB, the left JC1 had a heat sink temperature of 101 degrees and the right JC1 had a heat sink temperature of 103 degrees (temperatures taken with digital thermometers). Sweet...I get more power with a little less heat generation. The JC1's probably use a better heat dissipation mechanism.
I made two 4-foot ground terminal strapping cables since the JC1's have two sets of binding posts (for biwiring). The strapping cables were made of some spare DSR Silverline 10 gauge speaker cable. One cable, which connects the unused negative binding post terminals, is terminated in Monster X-Terminator locking banana connectors. The other cable, which connects the negative binding posts that each speaker is connected to, is terminated by regular Monster bananas for quick release when removing speaker cables. It was not necessary to use two binding post strapping cables, since the binding posts of each JC1 are in parallel. I just like overkill.
Performance
Those of you who have been reading me for a while know that I favor audio components that have high price/performance ratios. Above a certain price point, you reach the point of diminishing returns where there is not a linear relationship between additional cost and additional performance. You end up paying a lot for a little more performance improvement. The JC1 pair, with an MSRP of $7000, is 3.5 times the $2000 MSRP of the Adcom GFA-5802. So....are the JC1's 3.5 times better than the GFA-5802's? No. No way, buster. I would subjectively say they are twice as good and are well worth the price they can be had for on the used market.
The Sound
The Adcom GFA-5802 is in no way "shamed" by the JC1 monoblocks. The GFA-5802 is a great design and gives me everything I like in an amplifer. However, the JC1's give me MORE of everything: More bass slam, more holographic 3-dimensional sound, more clarity, more details. There was no difference between the soundstage dimensions thrown by the GFA-5802 and the JC1's, nor was there a difference in the placement of instruments and sounds within the soundstage. There was a big difference in the "solidity" and clarity of instruments and sounds within the soundstage. The bass notes of the JC1's hit harder, although they measured no louder on a sound meter. There was more of a sense of real people playing in the room. I could also hear more reverberant artifacts of the recording space with the JC1's.
Using "Tiptoes" aluminum isolation cones under the JC1 made no audible difference like it did with the GFA-5802. I may leave them there because it allows more air to get under the amps, plus, it raises them up so that the cool blue light behind the power switch is not obscured behind the audio cabinet doors.
To sum it up: The Adcom GFA-5802 kicks ass, but the JC1's kick natural ass.("Natural" is pronounced nat'-Chul.)
I will provide a more detailed quantitative listening analysis after I have lived with the JC1's for a few weeks.
What I Do Not Like About the JC1's
1. The heat. They don't run as hot as the Adcom, but since I have two of them, the cumulative heat is a little bit more. Fortunately, I do not get a lot of heat buildup in my audio cabinet because there are 5.5 inches of clearance above each JC1 and the cabinet doors and side panels are steel mesh. The cabinet back is open.
2. Those DAMN PLASTIC BINDING POST NUTS. Really, what were they thinking? Why couldn't I have some nice Cardas or at least some sturdy Vampire all metal posts? Is that really too much to ask of an amplifier of this quality? Was that much money saved by using the cheapie binding posts? I'll certainly be changing those out soon. I always keep a bunch of nice Cardas and Vampire posts around just for such situations.
Further Thoughts
The Adcom GFP-750 preamp is staying in the system for the time being. I like it a lot because it sounds like.....nothing. I'll probably get a nice SACD player, once there are more than two or three SACD titles I'd like to own. For now, my well modified Sony CDP-XA7ES CD player serves well, especially after the power cord, the master clock, and a couple of cheap op amps in the balanced output section were replaced with much higher quality parts. I have no desire to sell the GFA-5802 and it is going on reserve duty. Eventually, I'll get around to applying the tweaks that I have read about on various other audio forums (yeah, sure).
The FedEx man is bringing me a turntable and phono preamp tomorrow morning. My love/hate relationship with vinyl continues. I don't listen to records a lot, but I have a lot of obscure recordings that are not and probably never will be on CD, so I'm stuck. We'll see if the Music Hall MMF-9 is able to retire my beloved modified Yamaha PF-800 turntable that I have used for the past 17 years. I suffer from upgradeitis like many others, but I think I manage it rather well.
More later.