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Need advice on my Parasound JC 1

Please everybody I need some help or rather some advice & feedback from all you JC 1 owners out there.

I bought my pair of JC1s in Feb 2004 & at that time I spoke to Bob (Mr. Crump) about the apparent lack of bass that I felt with these amps. Bob helped me out more than any one can ever ask for!
He explained that my 2 units were from the very 1st initial batch and 2 resistors on the output board for each amp needed to be swapped out. Bob even mailed out the 4 resistors to me in Calgary, Canada & they were replaced by me. Bob if you remember we exchanged many emails between us and thanks for all your advice & help. You are an awesome person to turn to for advice!

Now my system which comprises of the JC1 power amps, Moon P-5 pre-amp, Sony SCD-C555es SACD player & Energy Veritas 2.4 speakers (which are Canadian) still seem to lack bass at times.

Now only for the past 6 weeks I have been passing a signal from my tuner 24/7 thru these amps to burn them in. Since I bought them I have always had them on. However I read in these forums that in order to properly burn them in you have to feed them a signal 24/7 & merely keeping them on won’t burn them in. Is this true? As I have crossed 1400 hours quite sometime back but they were not fed a constant 24/7 signal.

Also I have a feeling that since these Energy Veritas 2.4 speakers have 6 ½ inch woofers (3 per side) & given the JC1s unusually high damping factor, the JC1s are over damping the bass from these speakers, I maybe wrong. What speakers are you guys using with your JC1s and do you think that the next speakers I buy should have 8 or 10 inch woofers. Also I want to get 2 new PC and a pair of new Balanced ICs between my Moon & JC1s, any suggestions. Should I change the Moon & go for a different pre-amp, what pre-amps are you people using?........I am really really confused? Most of my friends who come over seem to comment that the base is lacking, there seems to be no synergy in my system & that’s why I hardly listen to music anymore. Please this is driving me insane all help is welcome.

Also my bias is drifting & the amps are operating differently temperature wise. This has nothing to do with the bass problem as the bias issue is recent and I have always had the bass problem. However I am not happy at all with this bias issue & fail to understand why Parasound could not use better bias pots. I want to change out those bias pots & put better quality ones. Any ideas which make to buy & Bob can you please give me the values so I can adjust them.
jiya3600
11 responses Add your response
fcrowder
191 posts
 
I am using the JC-1's with Acapella Campanile Highs and have had absolutely no problems with either bass or dynamics. Three suggestions, i) if at all possible, borrow some balanced interconnect as the JC-1's sound significantly better in the balanced mode. ii) do try different power cords, again they make a difference, and iii) put the amps on a dedicated circuit. They like to see plenty of power from the AC.
drhst20
71 posts
 
Have you tried changing your speaker placement. The jc-1's should drive the heck out of those 6 1/2's.
cytocycle
1,043 posts
 
JC-1's don't lack bass when I've heard them. You can only move so much air with 6 1/2" drivers.

But it sounds like your listening position is in a bass null. Move your seating position and speakers.

I owned a Sim W5 amp and 4070 model and found those lacking in bass with my NHT 3.3 speakers even though the reviewers claimed they were excellent on the bass.
bpwalsh
1,207 posts
 
Yes, the feedback resistors were changed from the first batch, but I don't think it is unrelated to bias issues. I had an early pair as well and didn't have any problems with bias. Parasound solved a few glitches in early units and reports excellent reliability in more recent production runs. I hope you're aware the ten years parts, five years labor warranty is valid only to the original purchaser and when purchased from an authorized Parasound Halo dealer This policy is pretty common in the industry - it is always advisable to call the manufacturer to ask, if considering purchasing used or from a non authorized seller.

You are correct, merely leaving the amps turned on isn't enough to break them in, you need to be running signal through them at all times. Knowing that, go ahead and break them in and see if you don't notice some dramatic improvements at around 1200 and 1400 hours. I agree with others suggesting there should be no lack of bass in your system when set up optimally.

Brian
bpwalsh
1,207 posts
 
John Curl informs me the resistors you spoke of were step down resistors used to drop the 115V from the driver stage to 15V for the servos, not feedback resistors.

Brian
jiya3600 OP
15 posts
 
I live in an apartment building with average line voltage of 114 to 115 volts, I have checked it out with my fluke multi meter. So can’t run dedicated lines to them yet. Also I have not tried the balanced route and will definitely change to that type very soon.

The listening room that I have has a lot of echo and maybe also a bass trap I have to play with the speaker placement. Also might have to buy some sort of room treatment products like echo busters.

Brian these were bought from an auth dealer/store & not from any individual. My Bias is drifting and I have to re adjust them. I need the values otherwise I cannot do them. Also I would like to change those bias adjusting pots (which are the cheaper ones) on the JC1s to the encapsulated type & would also need values to buy the right ones. I know the feedback resistors are not related to the bias issue.

Also shouldn’t this posting appear on the Parasound discussion forum on the Audiogon site? Still waiting to hear from you guys which PC to buy for these amps!

Thanks a lot everybody
bpwalsh
1,207 posts
 
If you are having an issue with bias I suggest you contact your dealer first - that's his job, as support doesn't end when the check clears. If you're not getting any satisfaction then contact Parasound service, 866-770-8324 toll free. I recommend having Parasound or an authorized representative do the work.
jiya3600 OP
15 posts
 
I never spoke to John Curl ever, Bob & I emailed couple of times last year & he helped me out a lot. They were Mills Resistors (forget the value) black in colour and I had to install 2 of them on the output board of each amp
(4 Total). I dont think it has anything to do with 115V or servos as this is the output board I am talking about.

I also dont know if they pertain to as feedback resistors, you mentioned them as such after reading my first post, so i presumed thats what they were. I am a mech eng not an elec eng but am an audiophile at heart and am damn good at soldering & can read elec circuits to a certain extent. Brian you or Bob maybe can let me know how to adjust the bias.

Also I shouldn't say my bass is not there at all, its just that I don't feel it as how the other Audiogeners describe about the JC1's
jiya3600 OP
15 posts
 
I Live in Toronto now and the JC1's were bought in Edmonton, Canada. The service center here in Toronto informed me that they have not done any bias adjustment on JC1's yet but if i bought them in they could try to do so. The problem is the weight and hassle of carting them around, so I prefer to do this myself if possible.

By the way my line votage is 117V now, I just checked.
jafox
1,457 posts
 
Hmmm, I thought SS amps were supposed to be maintenance free. Now I don't feel so alone with constantly tweaking the bias pots on the CAT amps. 8-)
suzy
30 posts
 
Maybe you are expecting too much bass from a 6.5" woofer? Or it could be your room? I just finished a review of a pair of speakers with 8" bass units. They had plenty of bass in my main listening room. After the review, I moved the speakers to a smaller room that I am in the process of setting up as a second listening room. The same speaker had almost no bass in that room. So I contacted Echo Busters and they sent me a bass trap for each corner. Now the bass is back and then some. Seriously, consider room treatment. I reviewed an early version of the JC-1. That amp should have plenty of deep bass as long as your speakers (and room) are capable of reproducing it.
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