Looking for ideas - new mono blocks for stereo music

Writing up my Parasound comments, since it is so lengthy.

Stock – JC1 has a very refined sound, midrange is very smooth and refined. Emphasis is tilted slightly towards the upper midrange which causes the audio to sound just a little bit thin in the midbass area. Sound is soft. Overall, sound to me is just a little bit low fidelity. It’s very smooth and refined, but just doesn’t sing or have that effect of sounding real.

Main A/C fuse (on back panel) replaced with Furutech 15A – This significantly improved things. The attack and resolution is much better and tonal qualities are much more real. Instruments and vocals ring out with more truth. Sound is no longer tilted so much towards the upper mids and it is fuller sounding. The high frequencies are just a little bit jangly sounding (best I can describe), but overall a significant improvement. Bass is a significant improvement. It is still somewhat soft sounding.

All internal fuses replaced with Furutech (there are 6 fuses inside each JC1 that affect audio) – This is the best and most natural sounding result so far. There is no grain or jangly resonance heard in any of the frequencies. Bass is just absolutely amazing – oh my god! I cannot stress how much tight deep and strong bass you get with this particular configuration. It’s a serious “punch you in the chest” type of bass – hits really hard, but sounds natural and deep. Resolution and attack are still soft here. I think the soft attack also extends into some of the high frequencies as well.

In actuality, I discovered my Emotiva XPR-1 amps (also loaded with Furutech fuses) just beat the crap out of the JC1 with regards to resolution and detail. However, the Emotiva is not the cleanest sounding amp and I can definitely hear a slight element of grain in the sound.

So what’s really going on here? I think it’s a combination of things. I have listened very closely this weekend and I think the main thing I am hearing is that the Parasound amps have a very soft attack on midrange and early high frequencies. I believe this is mostly due to the Class A biasing. Even though JC1 is not a pure Class A amp, it is still Class A biased into 10 watts (at low bias setting). This is still enough Class A biasing to soften the attack on the midrange waveforms by smoothing out the response to the waveforms themselves. Class A circuits will tend to have a very gradual curved response when it receives a waveform spike on the input. This is less sensitive with analog preamp circuits, but when you are working with speaker level voltage, the response curve is much more gradual (based on slew rate response). This has a result of making angular waveforms (like a snare hit) more rounded or curved. Again, it depends on the engineering of the Class A circuit and how it responds to spikes on the input.

A comment on the high bias (25 watt) configuration of the JC1. The only time in my system that the 25 watt high bias Class A setting sounded good was with the stock fuses. The High Bias actually provided a more engaging sound. However, with Furutech fuses, it just made things too slow and mushy.

Another possible reason is my speakers, which are B&W 805 D3 diamonds. They are not a very fast responding speaker (they are actually hard to drive from an amp standpoint), but they are very natural sounding (the reason I went with them). So the combination of a neutral responding speed and the difficulty of pushing the drivers and magnet engines could contribute to the slow attack on the midrange and highs.

Finally, it can also be from having too many Class A stages. I have found through extensive testing with DAC/preamp stages that if you have too many Class A stages in a row, the sound becomes too slow and soft. So, my configuration:

HT Processor – Krell S1200U discrete Class A analog stage

JC1 – discrete JFET Class A input stage, MOSFET driver stage

JC1 – high biased Class A output stage

In my case, I think all of the above items contribute to a soft attack on the mids/highs. It does sound very nice and pleasant. Music is nice and pleasant (such as with a tube amp), but just doesn’t have that extra bit of attack and resolution to make things stand out. For home theater purposes, I just don’t have enough attack/detail to make movies exciting and engaging. It’s definitely not an optimum amp choice for my system.

I think the Parasound amps would work very well with speakers that are extremely fast responding and no decay. The Martin Logan panels are one example as they definitely have a tendency to sound bright/thin/harsh. They require the waveforms to be further smoothed so that it fills out the sound. Other speakers that might excel are the Monitor Audio Platinums (with the very fast ribbon tweeters) or maybe the Focals with their extremely light and fast responding midrange/woofers. Or add a JC1 if you have a very thin/bright sounding preamp/source.

@bigddesign3 – this could also be the reason that the Krell Class A works so well with your Martin Logan panels. If you read Whitecamaross’s amp thread, he states that the JC1 does everything right from top to bottom. Reading further, he found that the huge Pass Labs 200 watt full Class A monoblocks were the best sound he heard (though I am suspicious of his continued “this is the best” posts). He also was listening with high end Martin Logan Panels with those two amps.

Further comment on bigddesign3's speakers.  The Martin Logan Montis is an active woofer design, meaning that frequencies under the 340hz crossover point are sent to the internal Class D amplifier.  This means that the main Krell amp does not need to carry the load of the woofer impedances.  Bigddesign3's comment that he may not necessarily need a huge amp power supply can be true here.

The JBL 1400 has a big 14" woofer.  It only drops down to about 5 ohm around 100hz, which is not too bad, but this speaker will still benefit from a huge amp power supply - to support bass strength/heft.

Bryston 7b3

Okay, here’s the low down.  The amp is actually smaller than the Parasounc JC1. It is lighter as well.  It does have a sizable transformer, but the JC1 transformer is bigger.  However, it has a larger capacitance bank in the power supply sections (16 x 10,000uf = 160,000uf!!).  Initial assumptions that it works only off a circuit breaker are incorrect.  There is actually a small 12.5A fuse on the board close to the IEC plug input.  It is covered by a rubber grommet that is easy to remove with pliers.

Stock – initial listening showed this amp as very clean.  It is definitely cleaner and faster than the Parasound.  I thought that it sounded somewhat thin, but it might sound different in other systems.  Extended initial thoughts seemed that this amp sounded a bit clinical and just a tiny bit sterile in presentation.

With Furutech fuses.  I had one 10A and one 5A that I put in these two 7b3.  The 5A is undersized, but I am not going to consume more than 600 watts of A/C for my tests, especially since these will drive my bookshelves, which are crossed over at 80hz.  With the Furutech fuses, it definitely filled in more of the midbass body.  Made things better and just a little bit more natural over all.  However, extended listening told me that this was still too clean and fast.  There was too much attack and it pushed it over the edge into the “too solid state” characteristics.  Bass was extremely clean and clear, but just bordering on a tiny bit harsh.

Isoclean 5A fuses (5A was the biggest I had).  Isoclean uses gold-plated endcaps and conductor wire.  Much much better!  The amp sounds more neutral now.  The upper mids and highs are not so push hard and it gives you a sense of tonality.  This is great because it tells us this amp can be tamed if it is too bright and hard edged.  The bass was very good here.  Overall, this was the best this amp sounded.  It does not have the slam and bass punch that the Parasound has.  I would describe this as a very gentle and delicate sound – extreme amounts of resolution and detail.  Even with the Isoclean fuses, this amp was extremely clean and resolving.

Here’s a note on others that have had extreme success with the new Bryston cubed amp series:

https://forum.audiogon.com/discussions/finally-took-the-bryston-4b-cubed-plunge

That being said, the Bryston in my system was very good, but it was still just slightly thin.  It was very clean and clear, but did not have the organic life that the Parasound JC1 had.  Since the Parasound had more body, the overall sound was fuller and, as a result, louder.  I could hear more of dialogue and voices in movies.  I think that my system is just way too high resolution for the Bryston amp.  I have rhodium plated everything.  Audioquest Rocket 44 with Furutech rhodium spades. Rhodium XLR connectors and power cord connectors.  The Krell S1200 is definitely not a warm preamp/processor.

I suspect the Bryston 7b3 would excel in a system that had a warm tube amp or something like a NAD or B&K preamp.  My Krell and cabling is just not warm enough to transfer to the Bryston.  With your Marantz processor, it might just be warm enough to give the Bryston a fully rounded signal.  However, with the Esoteric preamp, the Bryston might come out being too thin.  You’ll have to wait and see.  I will say that the Bryston is just about the highest resolution and highest resolving amp I have heard.  That being said, it will not add anything (which could be bad if you need something added into the signal).