Parasound JC1 Mono Amplifiers - First Impressions
DarqueKnight
Posts: 6,765
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 ****, but the JC1's kick natural ****.("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 ****, but the JC1's kick natural ****.("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.
Proud and loyal citizen of the Digital Domain and Solid State Country!
Post edited by DarqueKnight on
Comments
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No suprises here, enjoy the new kids.CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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Wow, that's awesome. They certainly have some nice stats, and they look huge! Looks like each one is almost as big as a RB1090; now that's big!
In UseGeorge Grand wrote: »
PS3, Yamaha CDR-HD1300, Plex, Amazon Fire TV Gen 2
Pioneer Elite VSX-52, Parasound HCA-1000A
Klipsch RF-82ii, RC-62ii, RS-42ii, RW-10d
Epson 8700UB
In Storage
[Home Audio]
Rotel RCD-02, Yamaha KX-W900U, Sony ST-S500ES, Denon DP-7F
Pro-Ject Phono Box MKII, Parasound P/HP-850, ASL Wave 20 monoblocks
Klipsch RF-35, RB-51ii
[Car Audio]
Pioneer Premier DEH-P860MP, Memphis 16-MCA3004, Boston Acoustic RC520 -
I think I need to change my pants.
Very nice. I have always liked the looks of the Halo gear. -
Very nice! How can you be absolutly sure it is ok to use those with SDA's? Just wondering.
madmaxVinyl, the final frontier...
Avantgarde horns, 300b tubes, thats the kinda crap I want...
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A very interesting reading. Thanks!
I think the MMF-9 will be a very pleasant surprise. My MMF-5 retired my hot rodded Technics I've had for over 30 years with Mayware Formula IV tone arm and ADC XLM cartridge. I upgraded the stylus to the Goldring G1042, a quantum improvement.
Like you, I can't walk away from four decades of small label and regional recordings on LP. All that aside, I thoroughly enjoy the spatial and temporal "clues" that vinyl seems to impart.
Enjoy! -
You had me at 'the Fed-Ex man delivered'
BDTI plan for the future. - F1Nut -
Very nice! How can you be absolutly sure it is ok to use those with SDA's? Just wondering.
madmax
I called Parasound's technical support department and explained my speaker situation with the need for common ground amps. The guy I spoke to said the only problem he could think of was that I might get some "crosstalk" between the two amps. Ummmm....I can see getting crosstalk when the two channels are in close proximity in the same chassis and there is some chance of electromagnetic coupling. However, I didn't think that the JC1's would generate a strong enough EM field that would allow them to be "coupled" through a 4-foot cable while sitting 2 feet from each other. And anyway, my speakers have "crosstalk" cancellation by design. I have been listening all day and have not heard any unwanted "crosstalk".
I must tell you though, my paranoia did get the best of me and I did break out my volt/ohm meter and test for ground continuity in each individual amp and between the amps while they were connected. I tested for ground continuity in both powered and unpowered states, because some amps are completely different animals in their energized states. Next, I did listening tests on a spare pair of SDA CRS+'s prior to hooking them up to my monoliths. No problems in any scenario.:)
I would get six more JC1's for my HT system, but the additional monthly cost for electricity to run the amps and to constantly run the ac would be prohibitive. Besides, six JC1's would not fit in my current HT cabinet. :eek:Proud and loyal citizen of the Digital Domain and Solid State Country! -
BlueMDPicker wrote:Like you, I can't walk away from four decades of small label and regional recordings on LP. All that aside, I thoroughly enjoy the spatial and temporal "clues" that vinyl seems to impart.
Enjoy!
Even if some (or all) of my well-recorded favorite oddball records did magically appear on CD one day, I know that, in most cases, the transfer recording quality would suck compared to the original record. So, once again, I would be stuck.
BTW, I am trying the MMF-9 with the PS Audio GCPH phono pre that you have. The GCPH seems to be very highly regarded. Even better than that, they show up very frequently on Audiogon and on PS Audio's website "B Stock" section in like new condition and at hundreds off the MSRP. I want to be into vinyl enough so that I enjoy my records, but not into it so much so that I am taking out a second mortgage.Proud and loyal citizen of the Digital Domain and Solid State Country! -
From what I've heard the failure mode starts as a current between the grounds at a fairly low voltage. When I tried to measure the current between my carvers I wasn't getting any reading but that never did truely satisfy my curiosity. Six for the HT? I would say 8, that way you can bi-amp the fronts...
Vinyl, the final frontier...
Avantgarde horns, 300b tubes, thats the kinda crap I want... -
madmax wrote:From what I've heard the failure mode starts as a current between the grounds at a fairly low voltage. When I tried to measure the current between my carvers I wasn't getting any reading but that never did truely satisfy my curiosity.
If something blows up, I've got the name, rank, and serial number of the Parasound guy who told me everything was gonna be o.k. Hmmmm....maybe I should call back and record the conversation. You're making me (more) paranoid.madmax wrote:Six for the HT? I would say 8, that way you can bi-amp the fronts...
I don't know. I would be afraid people would "talk" if I had an HT with eight monoblocks and bi-amped SRS fronts. I don't want to be stigmatized as overindulgent. So-called "normal" people who come to my house already think something is wrong with me because of all the audio/video stuff. On the other hand, I was pleasantly surprised to find that the HT is a better chick magnet than a Porche. Go figure.Proud and loyal citizen of the Digital Domain and Solid State Country! -
DarqueKnight wrote:I was pleasantly surprised to find that the HT is a better chick magnet than a Porche. Go figure.
What chick could turn down an awsome movie! Well, maybe a chick flick movie anyway.
Overindulgent? You? I don't know anyone on this board who is overindulgent. Vinyl, the final frontier...
Avantgarde horns, 300b tubes, thats the kinda crap I want... -
DarqueKnight wrote:So-called "normal" people who come to my house already think something is wrong with me because of all the audio/video stuff.
I went to a friends house awhile back and he had a little TV on one side of the room and one of those record player/8track/am-fm combos on the other side of the room complete with the little 8"x12"x3" speakers. That is his total life commitment to the audio-video world. Might have been a SoundDesign from the early 70's come to think of it. It made me feel kinda sick.
madmaxVinyl, the final frontier...
Avantgarde horns, 300b tubes, thats the kinda crap I want... -
DarqueKnight wrote:On the other hand, I was pleasantly surprised to find that the HT is a better chick magnet than a Porche. Go figure.
American Pie and Austin Powers seem to work pretty well for me on the plasma.
Also, thanks for the info on the JC1's.
WesLink: http://polkarmy.com/forums
Sony 75" Bravia 4K | Polk Audio SDA-SRS's (w/RDO's & Vampire Posts) + SVS PC+ 25-31 | AudioQuest Granite (mids) + BWA Silver (highs) | Cary Audio CAD-200 | Signal Cable Silver Resolution XLR's | Rotel Michi P5 | Signal Cable Silver Resolution XLR's | Cambridge Audio azur 840C--Wadia 170i + iPod jammed w/ lossless audio--Oppo 970 | Pure|AV PF31d -
Congrats! Enjoy the new amps Raife! Thanks for your impressions of the JC1's.
I own a Halo A21 (250 wpc @ 8 ohms). This amp can be bridged and I was thinking of getting another, using the A1-1 interface that I have. By doing this I would have 500 wpc at a lot lower price. I bought my Halo A21 for $1,100 (used). I'm sure I could pick up another for about the same price. This is a lot less money than the 2 JC1's.
Did you consider two bridged amps as an option?Carl -
No, I did not consider amps that were bridgeable by flipping a switch. I did consider amps that were self contained "bridged" designs.Proud and loyal citizen of the Digital Domain and Solid State Country!
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DarqueKnight wrote:BTW, I am trying the MMF-9 with the PS Audio GCPH phono pre that you have. The GCPH seems to be very highly regarded. Even better than that, they show up very frequently on Audiogon and on PS Audio's website "B Stock" section in like new condition and at hundreds off the MSRP. I want to be into vinyl enough so that I enjoy my records, but not into it so much so that I am taking out a second mortgage.
I really can't say enough good things about it. I'm running it balanced, through the Carver Lightstar Direct preamp, passive. Madmax has heard the MMF/GCPH setup and (perhaps he was flattering me) said it sounded as good as his vinyl rig. -
Congrats on the sweet new gear! I've heard the JC1s with both Legacy Signature III's and Thiel CS 7.2's. They sounded exquisite with both speakers (whether Vinyl, CD, or SACD - it didn't matter) and that's no small feat with the notoriously hard to drive Thiels! I'm pretty sure the Thiels dip down to 3 ohms in spots. I remember they sounded very neutral, accurate, liquid, and musical - all at once - with both pairs of speakers. Honestly I wish I could acquire a pair for myself
Maybe in a year or two. They're well worth the money over the more budget priced amps I've heard, IMO. They're also probably the only SS I've heard that didn't leave me wishing I was listening to tubes instead. Tannoy Dimension TD10, SOTA Star Sapphire, Heathkit W4A's, McIntosh MC2100, Eddie-Current Zana Deux, Singlepower SDS, Sennheiser HD650, Audio-Technica L3000, Sony Qualia 010 -
BlueMDPicker wrote:Madmax has heard the MMF/GCPH setup and (perhaps he was flattering me) said it sounded as good as his vinyl rig.
No flattery, it really did. To be brutally honest, the MMF/GCPH, while having its own amount of characteristic sound (meaning I could hear the results of the combo added to the sound on the lp) it was every bit as smooth and pleasing while having the ability of grabbing hold of the speakers in a very dynamic way just as my system does. It far exceeded my expectations and given the cost had me wondering why I went with my setup. Of course I told myself it just had better synergy with the equipment and the room.
madmaxVinyl, the final frontier...
Avantgarde horns, 300b tubes, thats the kinda crap I want... -
Wow. Considering the vinyl setup Max has, that's quite a compliment.Proud and loyal citizen of the Digital Domain and Solid State Country!
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Madmax is audio insane, just FYI. He's the Maxwell Smart of the Polk audio world.
When it comes to vinyl....he's a pussycat when it comes to the K.CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint. -
Congrats and enjoy!Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Omg....Magico M2, JL113v2x2, EMM, ARC Ref 10 Line, ARC Ref 10 Phono, VPIx2, Lyra Etna, Airtight Opus1, Boulder, AQ Wel&Wild, SRA Scuttle Rack, BlueSound+LPS, Thorens 124DD+124SPU, Sennheiser, Metaxas R2R
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DarqueKnight wrote: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 ****, but the JC1's kick natural ****.("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.
thanks for the woinderful review.my Adcom GFA-5802 arrived today.and i feel confident that ill be pretty happy with it.
