Parasound Halo JC 1+ monoblock power amplifier

Soon after I took over preparing Stereophile's biannual Recommended Components listing from the magazine's founder, J. Gordon Holt, in 1986, I ran into a problem. With so many products listed, the magazine was running out of the necessary pages to include them all (footnote 1). To solve this problem, I looked at how long a typical product remained on the market before being updated or replaced. The answer was 3–4 years. I therefore implemented a policy that unless one of the magazine's editors or reviewers had continued experience with a product, it would be dropped from Recommended Components after three years.

But what about a product that continues unchanged in production for years, or even decades? Consider Parasound's Halo JC 1 monoblock power amplifier, designed by legendary engineer John Curl and originally reviewed by Michael Fremer in February 2003. The JC 1 took up residence in Class A in Recommended Components in the April 2003 issue and remained there through the October 2018 issue. Every year for 15 years, either someone from the review team or I would drag the amplifiers out of storage and compare them with whatever we were using to determine if they were still worth recommending—they were.

However, Parasound's Richard Schram announced in the summer of 2018 that a revised version of the Halo JC 1, with significant reworkings by John Curl of the circuit and parts, was coming down the 'pike. I put my name down for a review.

External differences
The original JC 1 cost $6000/pair in 2003, and by the end of its production life the price was $8990/pair. (According to an online inflation calculator, $6000 in 2003 is equivalent to $8531 in 2020 dollars, meaning the increase in the amplifier's price tracked inflation.) As the JC 1+ costs $16,990/pair, it is significantly more expensive than its predecessor in real terms, but still less pricey than many other high-power, high-end amplifiers Stereophile has reviewed in recent years.

The Halo JC 1+ is rated as being able to deliver 450W into 8 ohms, 850W into 4 ohms, and 1300W into 2 ohms, these powers slightly greater than those offered by the original amplifier. Viewed from the front, the JC 1+ looks very similar to the two-channel Halo A 21+ that Kal Rubinson favorably reviewed in March 2020. The only visible changes from the JC 1 are Curl's signature printed on the front panel, the absent THX logo, a subtler blue LED in place of the original bright red one, and aluminum end caps with gold highlights.

520para.bac

From the rear, the JC 1+ still has two pairs of loudspeaker binding posts, these of higher quality than the original's; a switch to select Normal or Low output-stage bias; and the usual turn-on and 12V trigger switches and connectors. While the new amplifier still has single-ended RCA and balanced XLR input jacks, along with a switch to optimize the input circuitry for each, there are now pass-through output jacks. In place of the original's ground-lift switch, there is now a switch to allow the amplifier's gain to be set to Normal or Low, the latter reducing the gain from 29dB to 23dB for use with preamplifiers whose volume controls can't be used in their optimal positions or when the user's speakers are sufficiently sensitive that hiss can be heard.

At 83lb, the JC 1+ is 30% heavier than the JC 1. All the other differences reside inside the chassis.

Internal differences
A detailed explanation of all the changes and improvements incorporated in the Halo JC 1+ can be found on the Parasound website. To summarize these:

• In almost all amplifiers, the input stage power supply is shared with the output stage supply, which can affect the input-stage behavior when the output stage is subject to heavy demands for current. The original JC 1 had additional secondary windings on its power transformer to feed the input and driver stage. The JC 1+ has a separate R-core power transformer that supplies ±89V to high-speed, soft-recovery bridge diodes and Nichicon filter capacitors totaling 22,400µF. An R-core transformer has minimal capacitive coupling between its primary and secondary windings, which should reduce AC noise. In addition, the JC 1+ uses a pair of Bybee Music Rails, which are patented active, high-frequency noise filters.

• The new amplifier's printed circuit boards were designed by Carl Thompson, who was responsible for the boards in John Curl's Vendetta Research phono stage, as well as for the JC 1 and other Parasound products. The JC 1+'s shielded input- and driver-stage circuit boards use an FR408 substrate, a substance that was developed for ultra-high-speed applications in supercomputers and aerospace.

• As in the JC 1, the JC 1+ input stage uses hand-matched pairs (footnote 2) of Toshiba 2SJ74 P-channel and 2SK170 N-channel J-FETs. Parasound and, I believe, Ayre Acoustics have invested heavily to secure an ample stock of these no-longer-manufactured, low-noise J-FETs. While the JC 1 driver was a single-stage circuit, for the JC 1+, John Curl designed a two-stage, cascode driver that would have some of the favorable attributes of vacuum tubes.

• As the number of high-performance loudspeakers with impedances that drop below 2 ohms is on the increase, Curl increased the number of Sanken NPN and PNP bipolar output transistors from 18 to 24. The output-stage circuit boards are now mounted vertically rather than horizontally, which should result in more effective heat dissipation. To deal with the increased current, the copper traces on the amplifier's main circuit board and the output-stage circuit boards are twice as thick as on the JC 1.

• The peak output current is specified as 180A, supplied by Nichicon Gold Tune capacitors, two more than the JC 1. Richard Schram says that although the Gold Tune capacitors were discontinued years ago, Nichicon continues to manufacture them exclusively for Parasound.

520para.top

Listening
As the JC 1+ operates in class-A up to 25W into 8 ohms when its bias is set to Normal, it runs hot. After a few hours of playing music, its top panel measured 105.6°F (40.9°C), the heatsinks 119.2°F (48.4°C). This amplifier needs to be well-ventilated, though if space is at a premium the output-stage bias can be lowered with the rear-panel switch, which reduces the class-A power to 10W into 8 ohms. In order to be able to use my PS Audio DirectStream D/A processor's volume control set sufficiently high so that its resolution would be preserved, I set the gain switches of the JC 1+ monoblocks to Low. I left the gains at Low when, for some listening sessions, I used the sample of Parasound's Halo JC 2 preamplifier, also designed by John Curl, that I reviewed in March 2008.

Primary loudspeakers were the floorstanding Vimberg Minos that I reviewed in April 2020, though I also used my KEF LS50 minimonitors for some of the auditioning.

Having let the Parasound monoblocks warm up, I started listening. My initial impressions reminded me of the first time I heard a Krell class-A amplifier, in the early 1980s: low-frequency authority combined with superbly precise stereo imaging and a deep, stable soundstage. Those early Krells could be a touch grainy-sounding in the treble, but the Halo JC 1+'s high frequencies were smooth and clean.

Tidal pulled up "Private Investigations" from Dire Straits' Love Over Gold. Back in the fall of 1982, I had obtained a prerelease CD of this album and was playing it at an English audio show, with a system featuring Arcam-driven Celestion SL6es, to give audiophiles a taste of CD sound. On the Vimbergs powered by the Parasounds, this atmospheric track sounded way better than my almost-four-decades-old memory would have predicted. I know, I know, different mastering perhaps; yes, digital playback has improved a lot over the years; and I can't remember what I had for dinner last Tuesday, let alone anything other than a broad-brush overview of what happened 38 years ago. But what I was now hearing with this track gave no clue to its early-digital provenance.


Footnote 1: A problem that continues to this day, now that Jim Austin prepares the listings.

Footnote 2: J. Gordon Holt and I visited John Curl in 1987 and witnessed him hand-matching small-signal FETs for use in the Vendetta phono preamplifier.

COMPANY INFO
Parasound Products, Inc.
2250 McKinnon Ave.
San Francisco, CA 94124
(415) 397-7100
ARTICLE CONTENTS

COMMENTS
Bogolu Haranath's picture

May be JA1 could keep the JC1+ for a while (or, the Classe Delta monos), and review the new Magico A5 speakers :-) ........

Jim Austin's picture

I (JA2) was scheduled to review the A5 for our August issue, but when California was shut down, my review pair had not yet been built, so the review was postponed indefinitely.

Jim Austin, Editor
Stereophile

Bogolu Haranath's picture

Hopefully, they could be built during the 3rd quarter ........ Hopefully, you (JA2) could review and publish that review before the end of the year ....... My guess is, they are worth the wait :-) .........

Jim Austin's picture

I await them eagerly. Meanwhile, I'll have to make do with the M2s I have here at the moment. :-)

Jim Austin, Editor
Stereophile

Bogolu Haranath's picture

You could compare them to M2s and also, the Revel Salon2s :-) .......

Bogolu Haranath's picture

You (JA2) could do follow up review(s) of the JC1+ and/or the Classe Delta monos with M2s, while waiting for A5s :-) .........

Bogolu Haranath's picture

If you (JA2) do a follow-up review of JC1+, may be you could also do a review of the Parasound top model, JC2 BP pre-amp ($4,500) :-) .......

John Atkinson's picture
Bogolu Haranath wrote:
If you (JA2) do a follow-up review of JC1+, may be you could also do a review of the Parasound top model, JC2 BP pre-amp ($4,500) :-)

Kal Rubinson reviewed the Halo JC2 BP in 2011. See www.stereophile.com/content/music-round-47-page-3.

John Atkinson
Technical Editor, Stereophile

Bogolu Haranath's picture

Thanks ...... I missed that review ....... JA2 could still do a follow-up review of JC2 BP with JC1+ :-) ........

Pritam's picture

Thanks for a great review, John - I thoroughly enjoyed reading your write up. I have had a few Parasound products over the years and currently own a P6 paired with a JC 5 power amp. The latter is the
best power amp I have ever owned and paired with a pair of Monitor Audio Gold 300s, the sound is sublime! I wonder how different a pair of JC 1+ would sound in my current system; anyway, Well done, Mr. Curl is all I want to say as well for delivering the JC 5 - simply a most fantastic amplifier. Someday maybe I will own pair of the the JC1 + :) ..
I must also say, that the Gentlemen I have had the pleasure to interact with at Parasound, mostly for
product knowledge and to leverage their general audio experience, are simply wonderful.

Ortofan's picture

... comparison with the JC 1+ a ~17-year-old unit?
If so, was any effort made to determine (as by measurement) whether or not its performance had deteriorated with time?
It's not inconceivable that a nearly 20-year-old amplifier might need to have certain parts (such as electrolytic capacitors) replaced.

It's also disconcerting to find out that Mr. Curl/Parasound decided to incorporate obsolete devices into a new/updated product offering. None of the companies I've worked for would tolerate such a situation. Obsolete parts are only to be inventoried for use as service spares, not for current production units.

Herb Reichert's picture

in what engineering realm does "no-longer-manufactured" mean "obsolete" ???

Why do you think so many great/legendary amp designer's stockpile these JFETs (and other extra-ordinary parts)?

https://www.stereophile.com/content/gramophone-dreams-26-nelson-pass-harmonic-distortion

hr

Bogolu Haranath's picture

Ortofan's 'weaponized adjectives' are mild compared to some others, on Stereophile website :-) .......

Ortofan's picture

... really HR? That characterization seems a tad extreme.

"No-longer-manufactured" means "obsolete" in every engineering "realm" I've been associated with for the past 40 years.
Just one example of the usage of that term:
https://www.analog.com/cpsearch/crossreferencesearch.aspx
Would you find the phrases "not for new design" or "end of life" less offensive?

Why do "so many great/legendary amp designer's stockpile these JFETs (and other extra-ordinary parts)?"
Likely because they would rather not go to the expense and effort required to find suitable replacement devices, redesign circuits and circuit boards as necessary, possibly reprogram the assembly equipment if automated assembly is used, update the documentation, get the products re-certified by regulatory agencies, and so on. Maybe the companies for which these "great/legendary amp designers" work don't have a sustaining engineering department whose function includes the redesign of existing products when certain components become "obsolete". For a relatively low volume application, making a "lifetime buy" of "obsolete" devices may be the more economical and expeditious route. However, that's never been considered an acceptable practice for any of electronic products with which I've ever been involved.

Bogolu Haranath's picture

JA1's review of Classe Delta monos is coming soon in Stereophile ....... May be JA1 describes how the new, more modern Classe, class-A amps are designed ...... and, how the Classe monos compare with JC1+, in sound quality :-) .......

Bogolu Haranath's picture

Some people take the 'don't mess with success' approach :-) .......

John Atkinson's picture
Ortofan wrote:
Why do "so many great/legendary amp designer's stockpile these JFETs (and other extra-ordinary parts)?" Likely because they would rather not go to the expense and effort required to find suitable replacement devices...

When I discussed the subject with the late Charley Hansen some years ago, the problem is that there weren't any replacement parts. Apparently the semiconductor fabs no longer manufacture high-performance but low-profit, complementary, small-signal J-FETS that get anywhere close to the performance of those used by Parasound, Ayre, and others. Charley therefore spent a very large sum buying up as much as he could afford of the world's supplies of these devices.

John Atkinson
Technical Editor, Stereophile

Ortofan's picture

... totally stymied if a favorite component becomes "unobtanium"? If they are, indeed, truly "great/legendary", shouldn't it be well within their capability to develop an alternate design that uses more readily available devices?

ROHM once made fabulous bipolar transistors, with exceptionally low base spreading resistance, that were ideal for a moving-coil cartridge phono preamp. In the days of CRT-type HDTV sets, Sanyo and Panasonic produced high-voltage transistors, with very low collector output capacitance, that were well suited for use in the driver stage of an audio power amp. Those specific parts are all gone and they're not coming back. Linear Systems presently makes some low-noise JFETs and Sanken makes some transistors for audio driver applications. Neither are necessarily drop-in replacements for "obsolete" devices, so some redesign effort could well be required to convert to their use. Marantz's Ken Ishiwata used to comment on the matter of staying on top of device obsolescence and identifying acceptable replacements, while performing redesigns, as needed.

I've seen more than one case where the last-time-buy didn't last a lifetime. Those involved took the easy (or lazy) way out and hoped that they would no longer be working at the same company - either because they had changed employers, retired or died - by the time that the "lifetime" supply was exhausted.

Again, it's disappointing to see that a decision was made to incorporate obsolete devices into a newly updated product offering - especially one that seems to be on a decades long life cycle. It's curious to note that some tube amp consumers, by comparison, seem to have no qualms about the use of new-old-stock/out-of-production parts. Maybe that trend is spreading into the solid-state "realm"?

CG's picture

Two comments:

1. There are precious few companies making JFETs these days. The market just isn't there. This is especially true for P-channel devices, which are harder to make with low noise properties. Most of the JFETs available now are based on decades old processes that have been kept alive for some high priority customers. That doesn't include the audiophile product business.

Linear Systems has really done yeoman's work in providing JFETs for specialized industries. At least in the JFET world relevant to this discussion, much of their activity has been to clone the Toshiba designs. It's hard, again especially for P-channel devices. Toshiba had the process knocked, and produced them by the freight car load. There was that much demand and the prices were quite literally pennies per transistor. Linear Systems doesn't have that available market, so the prices are inevitably going to be much higher, both due to basic economics and the yield challenges. (You make a zillion devices and you learn the subtleties of the recipe.)

The trend now is for entire systems to be built into a single chip. That's where the money is. If a company gets a design win for a single cell phone audio system, that's bigger for that semiconductor company than if they got every sale of every semiconductor for the entire specialty audio market. By a large factor.

Something to consider...

2. Along the same lines, consider the age demographic of the guys (it's almost exclusively men) who are doing analog design for audio. It pretty much parallels the age demographic of the people who buy the finished product. What will happen when they decide to retire?

When I was in college, at your basic nerd school, it seemed like every EE major wanted to go into the audio business. Of the entire student body when I was there, as far as I know a total of three did go into the audio business. They all were management engineering majors, and the three focused on the business subjects that were part of that curriculum.

With the consolidation of system functions onto a single chip, that means that far fewer analog design guys are needed. That's been the trend for a while. The semiconductor providers also do much of the design work so that their customers don't need many analog design guys, not only for audio but for any analog application. That's probably a good thing, in a way, since the young people studying electrical engineering mostly aren't all that interested in analog or RF design. It's the circle of supply and demand.

Something else to consider...

Bogolu Haranath's picture

Five to ten years from now, all audio amplifiers are gonna be class-D ...... Five to ten years from now, people will be listening to wireless speakers with built-in class-D amps, in addition to various Bluetooth devices :-) .........

TJ's picture

Thanks CG, nice points

CG's picture

Dunno!

If you're paranoid enough, you could make the same arguments about bipolar output devices suitable for audio use, too. And a bunch of the other parts. Maybe that's not paranoia - just being realistic. I bet the tube guys had similar thoughts back in the boom days of tube based amplifiers.

In any case, if there's nobody interested in designing new gear, it won't matter, will it?

Ortofan's picture

... is that many (small-signal, and even medium power) devices, that were once available in leaded/through-hole packages, may now only be produced in surface-mount packages. Aside from the need to create new circuit board layouts and have SMT/SMD assembly capability, certain audio companies would have us believe that leaded/through-hole parts are "good" and that surface-mount parts are "bad".

If those companies have no choice other than to switch to using at least some surface-mount parts, then they would need to retract their previous assertions about the alleged inferiority of surface-mount technology.

CG's picture

I'm not sure that is accurate.

Many audio companies have already switched to surface mount semiconductors where the package is available.

The problem has to do with some of the passive components. There just isn't the ready availability of film caps in the varieties found with through hole components. Some will likely never be available in surface mount packages due to not only the size, but also the thermal constraints during surface mount soldering. Also, there is far less of a selection of low noise, low distortion resistors in surface mount packages. (Bruce Hofer, who certainly can be considered an expert on the topic, has written about this.) That inferiority is not "alleged"..

So, companies are then left with the choice of sonic compromise or to use mixed manufacturing technologies. Combining both surface mount and through hole components on the same printed circuit board assemblies can certainly be done, but it costs more. I'm sure audio companies would like to save money where they can, IF it gave them the same or better results.

Ortofan's picture

... quite adequate, unless you want to specify a particular boutique brand of capacitor in order to help validate your creation or lend it a certain cachet in the marketplace.

Likewise, for resistors, unless perhaps you're in the business of building test equipment. Funny how the tube amp makers all seemed to manage when resistors were mostly of the carbon composition type.

CG's picture

Well...

You are certainly entitled to your opinion on this. I disagree. Try finding polystyrene caps in surface mount. Not so easy. These types of caps have been measured to provide lower distortion in many circuit locations.

In general, I've noticed from you a certain hostility toward everybody in what I'll call the high performance audio business. This is shown in almost all of your posts. Again, you are completely entitled to your own thoughts on the business and the people who work in it.

This is not a good discussion. I hope you don't take offense when I decline to respond further.

JHL's picture

Well said.

Ortofan's picture

... to the function of your design, or might PPS type capacitors - available in SMT for from WIMA and Panasonic, to name two - be satisfactory?

Over 30 years ago, Hafler introduced the XL-280 power amplifier and claimed that it had the lowest residual according to a bypass test. To my knowledge, no one has ever stepped up to challenge that claim. The XL-280 accomplished that feat without resorting to the use of any exotic components. If an output capability of about 160W@8Ω/225W@4Ω was insufficient, there was the more powerful XL-600. An XL-600 would clip at about 370W, 680W and 900W into 8Ω, 4Ω and 2Ω, respectively. The XL-600 sold for $1,200 - or about $2,800 as adjusted for inflation today.

Similarly, QUAD has been producing its "straight wire with gain" amps for decades with out using exotic parts, either.

Essentially, do you want your amplifier to exhibit a certain subjective sound quality, or do you want it to be as neutral and self-effacing as possible? If you want a neutral amp, then it's been demonstrated that the use of exotic types of components is not a requirement to achieve that goal.

Bogolu Haranath's picture

Probably, the Benchmark AHB2 is similar in concept, as those Hafler amplifiers :-) ..........

Bogolu Haranath's picture

The new Hafler company still makes power amps ........ See, their website for details :-) .........

Bogolu Haranath's picture

Ortofan, Rotel says, in their Michi amps they use 'patented slit foil, low ESR capacitors' ........ Do you know anything about them? :-) .......

Ortofan's picture

... slit-foil type electrolytic capacitors for quite some time.
You can read about the technology here:
http://www.dnm.co.uk/capacitors.html

The slit-foil caps were originally sourced from BHC, which was acquired by Vishay/Kemet. Kemet still offers some parts of that type:
https://content.kemet.com/datasheets/KEM_A4029_ALC10S.pdf
https://sh.kemet.com/Lists/ProductCatalog/Attachments/632/KEM_A4030_ALN20S.pdf

According to the DNM site, the slit-foil caps may also be available from Taiwanese company Supertech:
http://www.supertech-elec.com.tw/electronic/ECAPS/Audio-2T.htm
http://www.supertech-elec.com.tw/electronic/ECAPS/Audio-4TTN.htm

DaveinSM's picture

That total capacitance figure of 22,400 on page 1 sure seems low. Are you sure it’s not 224,000?

Pryso's picture

I owned a pair from about 2006 to 2019 and used them with two different highly regarded speaker systems. No other amp delivered as much musical enjoyment as the JC1s with either speaker. I utilized the low bias setting for background music and hi bias for active listening. Heat was never an issue.

The only reason I no longer own them is because they have far more power than now needed, plus at my age they were becoming a little heavy whenever I needed to move them. I can only imagine the new model must be exceptional.

TJ's picture

Thanks John, great review. Any thoughts about how the SQ compares to your Pass Labs XA60.8 amps?

Jim Austin's picture

Any thoughts about how the SQ compares to your Pass Labs XA60.8 amps?

JA1 doesn't have the XA60.8s. JA2 does.

Jim Austin, Editor
Stereophile

Bogolu Haranath's picture

Which begs the question, 'any thoughts about how the SQ compares to your Pass labs XA60.8 amps' JA2? :-) ..........

Jim Austin's picture

Regrettably, I haven't had the opportunity to hear the JC 1+. Hopefully I will at some point in the reasonably near future.

Jim Austin, Editor
Stereophile

TJ's picture

at the same price but much lower weight

Bogolu Haranath's picture

Bridged AHB2s cost less than Pass XA60.8 or JC1+ :-) ........

TJ's picture

yes a lot less, I was thinking of the JC5

Bogolu Haranath's picture

Comparison between bridged AHB2s and JC5 would be interesting :-) .......

georgehifi's picture

Probably better than any other $17k amp/s around.

Cheers George

michelesurdi's picture

an exemplary review.when shall we see its like again?

georgehifi's picture

Not if Class-D and the environment has anything to do with it.
Maybe the Technics SE-R1 had a shot?

(Bit like exotic V8 V10 V12 muscle cars) I'm now driving a 2lt twin turbo buzz box, JUST NOT THE SAME!!!

Cheers George

Bogolu Haranath's picture

You can still buy a V8 Mustang, Camaro and Corvette :-) .........

georgehifi's picture

In Australia that'll cost you a kidney a lung and left testicle. $$$$$$$$$$.

Cheers George

Bogolu Haranath's picture

So, in Australia, if some one wants to buy an Aston Martin Vanquish or Lamborghini Aventador with V12 engines, that would cost them both kidneys, both lungs and both testicles :-) .......

georgehifi's picture

And if you want the Veneno Roadster, your body and soul is the price.
https://cdn.motor1.com/images/mgl/A80qL/s1/2014-lamborghini-veneno-roads...

Bogolu Haranath's picture

Poison ......

Venenosaurus :-) .......

Bogolu Haranath's picture

Armando the racing pigeon sold for $1.4 million in 2019 :-) ..........

georgehifi's picture

Nothing a BB gun wouldn't take care of.

David Harper's picture

All box speakers with dynamic drivers in them have distortion levels at least ten times that of any power amp. Therefore it is impossible to hear amplifier distortion thru this type of speaker. The amp's distortion is completely masked by the much greater speaker distortion. This is why discussions about the "sound quality" of amps are absurd. What these reviewers are actually hearing are the speakers, not the amp.

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