Parasound Halo JC-1 for Thiel CS 5i


I have a set of Thiel CS5i's that I am running with a W4S ST1000 amp.

Would Parasound Halo JC-1 mono amps be an improvement? Why?




I believe yes, in the upper mids and highs.

Class D will equal or can even better in the bass or low bass, but from mids up the JC1's especially with the higher bias Class A switch on, should be far better that the ClassD, for these reason here I posted.

Cheers George 

Hi dsper,

The CS5i's are the first speakers I fell in love with as a young audiophile more than 20 years ago, so I hope you continue to enjoy them.  As you know, they are a punishing load for an amplifier, so you need an amp that can deliver a lot of current due to low  impedance and sensitivity.  I believe the JC-1s would make a wonderful pairing at that price point, with a balanced tonality, authority, and continuousness (in the HP sense). 

Unfortunately, I don't have experience with the W4S amps, so cannot give you a real comparison in terms of performance. However, at a broad brush level, I agree with George's characterization with respect to the B&O Icepower amps I have heard (although well implemented versions, like the Jeff Rowland, can sound sweet in the midrange / treble, although lacking in ultimate refinement).

Best of luck.

Now that I’ve seen the impedance graph of the CS5i, I would say forget the WFS and go with the JC1’s.

"Sensitivity: 87dB/2.83V/1m (equivalent to around 82dB/W/m, given the low impedance)".

I didn’t realize the CS5i is so low in impedance in the bass and lower bass, below 2ohms, Class D will not drive this as well as the JC1’s

Cheers George

Thanks for the responses and Happy New Year!
Another fan of Thiel loudspeakers here as well. These things "crave" high-current in order to really open up nicely!
You might want to check with Parasound regarding 2 ohm loads. I believe the JC-1 is spec'd for 4 ohm loads minimum.

I am driving B&W 803Ds with a pair of JC-1s, and they have a minimum impedance of about 3 ohms. No problem with those, but 2 ohms is quite a bit lower.
I don't think the JC1's will have any problems with a 2 Ohm impedance swing.

"With continuous drive, the Parasound clipped at 545W into 8 ohms (27.4dBW)—way above the specified 400W. ("Clipping" is defined, as usual, as the power level where the measured THD figure reaches 1%, and is shown in fig.7 as the horizontal magenta line.) With a low-duty-cycle 1kHz toneburst more representative of music, the Halo was a powerhouse. Its clipping power increased by 0.3dB into 8 ohms, reaching 586.5W at 1% THD (27.7dBW, fig.7, black trace), with 1154W available into 4 ohms (27.6dBW, blue), 2255W into 2 ohms (27.5W, green), and no less than 4.2kW into 1 ohm (27.2dBW, magenta). The latter is equivalent to an output current of 64.7A!"


The current was what caught my eye on the JC1's as they listed something like 135 amps for instantaneous peaks.

The W4S is rated at 40 amps. I also see that an older Krell FPB 300c was rated less than that.

Now , of course, I am not sure how to read and understand all this technical data and be able to compare continuous versus peak outputs.

However, you cannot have current without watts, so I suspect that alternatives to the W4S will be different in the higher frequency and not so much in the bass, which gets at one of the perceptions about class D.

Any thoughts on that?




The W4S is rated at 40 amps. I also see that an older Krell FPB 300c was rated less than that.

Something is very wrong with what you saw or read, as there is no way the W4S could out current the Krell FPB 300c, especially into 4-2ohm loads, where it counts with the OP’s speakers.

Where did you see this? If these were figures can you point to them?

I would hazard a guess that one was "peak" amps and the other was "rms" amps at the very least.

PS: As the next Krell up "350c" I found can do
" Specified power is 350Wpc into 8 ohms, 700 big ones into 4, and a whopping 1400W into punishing 2 ohm loads."

These sorts of figures indicate massive current/amperage, and the 600c is much more. The WFS has no chance of doing these sort of figures.

PPS: I did find these figure on the 600c

"The FPB 600 could sustain a 29.3dBW level into this load, corresponding to 3,400Wpc—an extraordinary figure.

Driven on a toneburst equivalent to peak program duty at 8 ohms, it reached to touch the 1000W line, while at 4 ohms it attained 1850W, and for 2 ohms 3530W. And for 1 ohm—wait for it—an amazing 6000W!

Cheers George

Hi George,

Of course I cannot find the reference to which I referred in my earlier note.

However, googled the Krell web site and looked at the Krell Solo 575 Mono Power Amplifier featuring Krell iBias Technology. The output is listed as 575 W RMS at t 8 Ω and  900 W RMS at 4 Ω. The output current is listed at 22 A peak.

The W4S ST1000 is rated at 570W at 8 Ω and 1140W at 4 Ω with a maximum output current of 40A.

I am sure that there is some dissimilarity in the specs but any amp that can double into 4 ohms from 8 ohms cannot be  a slouch and simply run out of gas for 1 to 2 ohm loads. Or can it? And if so, why?

If the watts are there, you have to get the current, correct?

I am the OP on this thread and I can tell you that the W4S is powering the Thiel CS5i's with a lot of dynamics and texture in the bass. If there is a shortfall with the amp, it is probably in the treble where on certain CDs the high notes can get edgy. But then that could be the specific recording and not the amp.

For what it is worth, I use the same amp with my Maggie 3.6's which are not as bad a load as the Thiels. I am hearing a lot more resolution throughout the audio range with the Thiels over the Maggies with the same amp.

My thinking was the 135 amp peaks with the Parasound JC1's would do a better job on the bass. However, an earlier contributor to this thread suggests that the bass will not be  a lot different but the highs would be better with the JC1's. 

We all know the answer to this question will be for me to try some other amps and see what I like. Being on a budget limits my ability to get at the real high end stuff so.....!?






It's about more than just current and power.  I think until you have a chance to properly audition the JC1's you'll never be able to answer your question.

I've owned switching amps in the past, and was very impressed with them - but I haven't heard anything (within my budget) that wants me to replace my JC1's.

It's also not just about better highs or bass performance, it's about the whole.  The JC1's do everything very well, and do it in a cohesive manner.  It's hard to put into words, but easy to hear.

Can you audition a pair?

Here is a great new amp from Accuphase if you can afford it, that will drive those Theil’s without breaking a sweat. Not as cheap or as high wattage as the JC1’s but just as brutal with it’s ability to drive low impedances.

"Accuphase’s head of engineering, Masaomi Suzuki, introduced the company’s new P-7300 flagship class-A/B stereo power amplifier ($32,000). The amp outputs 125Wpc into 8 ohms. Its versatility extends to outputting 800Wpc into 1 ohm, which means that loudspeakers with challenging, amp-wilting impedance curves should not present insurmountable problems."

Cheers George

JC 1 would be MY recommendation.
George, My Lexus GS350 only cost 38K used! Dsper

I agree stupid money, but what I’m sort of getting across is the JC1’s are maybe just as good (with more watts) and I’ve seen them for $3k for a ruff pair, these are $4k. in Australia they are around $16K

Cheers George

This may not help but I run the halo a21 on my Thiel cs2.4,s and it works great. I also use a BAT VK-3ix tube pre and I believe a tube/ss combo is the ticket for Theils. I don't think the JC will disappoint. 


My local stereo store has loaned me an A21 for an in home trial so I will get a listen and see what comes of it.

Here is the interesting thing. It was suggested to consider the A31, which is three channel because, in a two channel setup, the third unused channel would add to the two channels in use, like give more power to the two channels being used in stereo mode. 

I am having trouble understanding this and am thinking that it might not be correct.

Is there anyone who has the technical expertise to comment on this?



That A21 should be fine as well, not as good as the JC1 monoblocks but should do the trick.

As it is also a JC design with bi-polar (BJT) output stage, which should give good current ability as well.

As for the A31 adding power from the third to the two channels if the third is not used?????? (bit of sales bulls**t there) I think this is just a powersupply taxing thing not a bridging thing, as how can a signal channel be split to add to two separate channels???? (It can’t)

I’d stick to the A21, if you can’t afford or get the JC1’s.

Cheers George


Well, here is the latest on the great experiment with the Parasound A21.

At 11 o'clock on the preamp while playing Fleetwood Mac "Rumors", the A21 one started to clip and went into protection mode. 

I routinely run the W4S ST1000 at 2 o'clock with no problem.

The answer is 400 watts into 4 ohms is not going to cut it with the Thiel CS 5i's.

Any other suggestions beside the Parasound JC1's?


^I'll hazard a guess that it's not the 4 Ohm load that's the issue.

As I posted earlier: Krell.

dsper Hi, Well, here is the latest on the great experiment with the Parasound A21.

At 11 o’clock on the preamp while playing Fleetwood Mac "Rumors", the A21 one started to clip and went into protection mode.

I routinely run the W4S ST1000 at 2 o’clock with no problem.

The answer is 400 watts into 4 ohms is not going to cut it with the Thiel CS 5i’s.

Any other suggestions beside the Parasound JC1’s?



Input Sensitivities.

Parasound A21 =1v

WFS ST1000 =2.95v (yours)

WFS ST1000 mkII = 1.31v

These are the input voltages needed into to make each amp reach it’s maximum output (watts) before distorting or shutting down or blowing up.

Now you can look back at your 11 o’clock and 2 o’clock preamp statements and see what’s happening.

And as I said the A21 will drive them but the JC1’s are the real deal, as for the WFS it’s class D, ?

Cheers George


Do you own JC-1s?  You're always recommending them?

No I don’t, wish I could, in Australia they are over $18k. And to buy a s/h pair in the US is cheap enough, but shipping for me is a huge cost, and then I’d need to convert them to 240v, but this could be just a primary transformer tap change if lucky.

I have something similar two pairs of ME850’s (long out of production) but very similar topology to the JC1’s.

My reviewer friend Edgar Karmer for HiFi Australia, 6Moons, and who also owns Audio Esoterica magazine has a pair of JC1's, and they were the best thing (beside an ME1500 also out of production) we found from many to drive his Wilson Alexia’s with, which are also a bitch to drive.

Cheers George

W4S ST1000 are class D

Yes I know, that was a tongue in cheek question mark, with eyebrows raised.

Let’s just say I like Class D for >4ohm bass/sub duty)

Cheers George

I used to own a pair of JC1s, and still regret selling them. They were a very complete amp and could drive almost anything. But I got sucked into the typical "upgrade" carousel and let go of them for a song. I don't need nearly that much power with my current speakers, but if I did, I'd snag another pair in a heartbeat.

Ok...I borrowed a Mark Levinson 433 from my dealer who had let me try the Parasound A21.

The ML 433 is very good - better texture to the bass and more refined treble compared to the W4S ST1000. And was able to play at high volume without clipping like the A21.

My question is now why would the A21 clip and the ML 433 would not given the same speakers and set up? Is this due to the power transformers and capacitance of the amps?

One day I may actually know something about this stuff!


A point I failed to make in my earlier post is that I am now understanding that I do not need to have a 500 watt amp to power the Thiels so this opens up a host of choices, I think.

But how do I go about eliminating those where the specs would indicate that they are probably not a good match?

Lugging 100 pound plus amps to my home is not fun. The dealer has used Krell and Pass amps that I could try.....

Excellent thread guys. I scored my pair of Thiel CS 2.4SE this week.
Now the fun part of picking/choosing the associated gear for them!

Keep me posted & Happy Listening!
Second note;
Thiel guys, how do you clean/maintain the fit + finish on your speakers?
^Thiel used to recommend one only use "Endust". Most everything else will leave dreaded fisheye. I apply the Endust to a soft cloth not directly to the cabinets. Be careful, especially with older models, cleaning the grill cloths, as it's possible to either push in the domes or if vacuuming to detach the voice coils. Except for the CS 2's (and perhaps other models?) which use an adhesive in addition to the screws to attach the grills to the cabinet, it might be wise to remove the grills before cleaning the grill cloths.

dsper, with the CS 5's it's the amps capability into 2 Ohms that is most relevant. I would only consider amps that could double down and down again into that load. I would recommend by starting with amps spec'd with the capability to deliver at least 400 Watts into 2 Ohms, and ideally 800 to 1600 Watts into 2 Ohms. After that it comes down to the sonic characteristics of the amps under consideration and personal preference.

These speakers amp requirements is perhaps the only reason I don't own them. Driven properly, they are wonderful!

Krell ;-).

I use a micro fiber cloth to remove finger prints on the black baffle and expect any good paste wax will be good fro the wood sides and back.

I had a tweeter cap fall off and ordered speaker glue from Simply Speakers. It cost $10 and I probably used 17 cents worth. It is white, rubber based, and will flex. I suspect Elmers rubber cement at a third of the cost for 4 times as much would work just as well, although the thin spigot on the Simply Speakers bottle was a way to not over apply.

One other thing I forgot to mention about the ML 433 is that it felt like it was at room temperature at the 12 o clock position after a couple of hours which makes it a viable candidate for a cabinet install.

WAF will create problems with a big amp sitting on the floor with exposed wires, etc.

Not sure that anyone cares but I took the ML 433 back to my dealer and he loaned me a Pass X350 that has new caps. In my opinion much better than the ML 433.

Bass may not be quite as tight as the ML 433 but the Pass has a nicer, sweeter high end with better decay and deeper sound stage - at least in my set up. Also the Pass is warmer. Finally, the Pass sounded effortless at high volumes compared to the ML.

This may be the difference between 200 watts and 350 watts into 8 ohms.

So, I rank them with the Thiel cs5's:
1. Pass
2. ML
3. W4S
4. Parasound A21

And it looks like I have a lot more to check into before I decide on this.

As an owner of Thiel cs 5i, I have driven them with parasound amp. The sound is dry and anemic until I substitute them with krell ksa 250 . I started to like them.  Add a tube preamp , it is unbelievable!!!! at 1 ohm , the krell put out 2000 watt!!!!! It makes the  theil sings. 
I certainly care- dsper.

I, too, am in a similar situation as you, my audiophile friend.
My short-list also has both Pass Labs & ML gear.

I will consider older gear as skfy57 suggested.

Keep me posted and Happy Listening!

Last week we had a very enjoyable day up in the mountains trying different things on Ed (Edgar)Krammer’s (reviewer for 6 moons, Australian hifi and Audio Esoterica) system which consists of an AMR CD-777 flagship CDP a pair of Parasound JC1’s and a pair of Wilson Alexia’s.

Preamps we had on hand were Supratek Grange, Nuforce all discrete flagship Reference P20, and a passive preamp.

All were used via the rca inputs on the JC1’s as we were only using 2mt interconnects and also didn’t want the extra circuitry of balanced inculded the signal path, as the AMR is tube output and TDA1541 convertor and therefore really single ended anyway even though I think it has token balanced outputs.

The one that came out on top was the passive, by quite a margin, for top to bottom transparency, dynamics, drive, and top (delicacy) to bottom (tight) extension.

The JC1’s controlled those hard to drive Alexia’s like they were born for it, with the extended Class A switched to on they were delicate, sweet and extended when needed, holographic midrange with real body to it, and controlled slamming subterranean bass to the depths of the earth.

.Cheers George

Here is my latest critique of my in home auditions of stereo amps with Thiel CS5's. I use a Prima Luna Dialogue Premium Preamp, Cullen interconnects, and a Rich Schultz modified Oppo105. Not running vinyl right now.

The Thiels are three feet from the facing wall, ten feet apart, two feet plus and four feet plus from side walls. I am sitting 10 - 11 feet away from the speakers with 15 feet behind me.

Pass X350 - most weight but not the best bass. Detailed and nuanced but slightly polite. Sweet high end

Krell Evolution 302 - Compared to Pass - slightly less weight with more forward/presence, tighter bass, just as detailed but with less nuance, Sweet midrange. BUT Hiss through speakers. I could live with the Krell except for the speaker hiss.

Hegel H20 - less weight compared to the first two but good bass. Lots of detail but slightly congested. Warm but not sweet. less presence than the Krell

Proceed HPA2 - Less weight than the first two, in your face, edgy treble, pretty good bass, misses some of the detail

Still have not heard one, but am thinking about pulling the trigger on a McCormack amp. Would cost less than the Pass or Krell.

Any further comments?