What did you do to your stereo rig today?
Comments
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J2 Power Amplifier
The J2 is a stereo power amplifier rated at 25 watts per channel. It has a two-stage circuit that operates in pure single-ended Class A mode, with signal JFET devices forming the input stage and power JFET devices for the output stage.
JFET transistors have long been recognized as having the highest audio quality of any transistor; the input devices of the J2 are known through the industry as the standard for low noise and linearity, and are found on the inputs of the finest phono stages, line level preamplifiers, and power amplifiers.
But for over 30 years robust power JFETs have not been widely available since the short-lived efforts of Sony and Yamaha. In the last few months, advances in Silicon Carbide (SiC) technology have resulted in new power JFET transistors with high voltage, current, and power capabilities – as high as 1200 volts, 30 amps, and 273 watts.
Created by SemiSouth Corporation of Mississippi, these robust new JFETs are designed for very fast high power switching in solar power and electric car applications. However, they also have a very low distortion characteristic that makes them superb for use in linear amplifiers. In apples-to-apples comparisons with comparable MOSFET type power transistors, they can achieve 10 to 20 dB improvements in distortion performance.
For over 10 years First Watt has been pushing the design envelope with simple high performance Class A amplifier circuits, and when a better transistor like this comes along, it can mean getting the same distortion performance with a lot less feedback, or lower distortion with the same amount of feedback. The J2 does amplifier does both,and that helps make it a better sounding amplifier than the best of its predecessors.
With a device that behaves a little like a tube, it is natural to consider popular tube amplifier design topologies. Single-Ended Class A tube amplifiers are not very powerful, and their measurement numbers are not exceptional, but there is no arguing that they have strong musical appeal to much of the audiophile population. The J2 amplifier uses a classic JFET differential input stage followed by a single power JFET transistor. This power JFET is biased by another JFET in what is known in tube circles as a “mu follower”.
Here is a slightly simplified schematic of the J2 circuit. It could be a classic tube amp, except that the P channel input JFETs would have to be fabricated from anti-matter. The single-ended Class A output stage is “second harmonic” in character, and it uses about half the feedback of a comparable MOSFET circuit but with half the distortion and twice the bandwidth.
The J2 power amplifier is simple, clean, and measures astonishingly well. It achieves a sound which is warm and relaxed, combining precision and detail without sterility. With a pair of sensibly efficient loudspeakers, it will give you a toe-tapping experience that other solid state amplifiers do not. The design is extremely reliable and will never need adjustment.
Download: J2 Manual
I copied and pasted right from the First Watt site.See my profile for list of gear. -
That's a big 10-4, good buddy.
... and 1.8 amperes into 16 ohms is about 52 watts (at about 29 volts) -
After getting just a taste of the Musical Fidelity sound, a Tri Vista came up for sale locally, and, as I am wont to do, impulsively snatched it. I am thoroughly smitten.
Congrats! I've been rocking a tri Vista integrated and dac for a while. As @F1nut suggests, the revelation audio cables to replace the stock umbilical cables are well worth it- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
After getting just a taste of the Musical Fidelity sound, a Tri Vista came up for sale locally, and, as I am wont to do, impulsively snatched it. I am thoroughly smitten.
Congrats! I've been rocking a tri Vista integrated and dac for a while. As @F1nut suggests, the revelation audio cables to replace the stock umbilical cables are well worth it
That is one gorgeous piece of gear. If it sounds half as good as it looks,it must knock your socks off! Congratulations!See my profile for list of gear. -
So,a voltage source amp would double power as ohms drop? My F5 is 25. Watts at 8ohms,50 watts at 4ohms. Would that be a proper example?
See my profile for list of gear. -
So,a voltage source amp would double power as ohms drop? My F5 is 25. Watts at 8ohms,50 watts at 4ohms. Would that be a proper example?
I believe you are correct, a voltage source amp sustains the same voltage as load impedence drops, as long it can keep producing more current. -
So,a voltage source amp would double power as ohms drop? My F5 is 25. Watts at 8ohms,50 watts at 4ohms. Would that be a proper example?
Yes, but to do that, it has to deliver twice the current into a 4 ohm load as it would into an 8 ohm load.
25 watts into 8 ohms equates to 14.1 volts at 1.8 amps (rounding off a bit)
If the load changes and the output voltage of the amp stays constant, the output current of the amp has to change
14.1 volts into 4 ohms is 50 watts, and requires 3.6 amps
14.1 volts into 16 ohms is 12.5 watts, requiring 0.9 amps
Here's where it gets interesting
Don't (ever!) forget that virtually all real loudspeakers are not even close to constant impedance devices. The actual impedance changes as a function of frequency. Today's highly complicated, hightly tweaked crossovers can present wildly varying impedance curves to the poor amplifier they're hooked to.
All of which, to my mind, illustrates how useless, or at least misleading, output power can be as a specification/measure of amplifier performance in the real world
I also think it illustrates why some amps and speakers are better combinations than others.
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Very good comment there, Doc. And this is why it’s really important to listen to amps with your particular speakers. Another reason to lament the disappearance of brick-and-mortar stores, where that may be possible.
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@VR3 Trust me, I'm on the lookout for those RAL umbilicals whenever they may pop up. Just can't justify $1000 to buy those new. With how good this amp sounds stock, they must really be great cords. -
mhardy6647 wrote: »
So,a voltage source amp would double power as ohms drop? My F5 is 25. Watts at 8ohms,50 watts at 4ohms. Would that be a proper example?
Yes, but to do that, it has to deliver twice the current into a 4 ohm load as it would into an 8 ohm load.
25 watts into 8 ohms equates to 14.1 volts at 1.8 amps (rounding off a bit)
If the load changes and the output voltage of the amp stays constant, the output current of the amp has to change
14.1 volts into 4 ohms is 50 watts, and requires 3.6 amps
14.1 volts into 16 ohms is 12.5 watts, requiring 0.9 amps
Here's where it gets interesting Don't (ever!) forget that virtually all real loudspeakers are not even close to constant impedance devices. The actual impedance changes as a function of frequency. Today's highly complicated, hightly tweaked crossovers can present wildly varying impedance curves to the poor amplifier they're hooked to.
All of which, to my mind, illustrates how useless, or at least misleading, output power can be as a specification/measure of amplifier performance in the real world
I also think it illustrates why some amps and speakers are better combinations than others.
This right here is why this forum is so valuable. You can't beat the knowledge base and experience we have here. Despite the horrible format, I'm really glad this forum is back. -
mhardy6647 wrote: »
So,a voltage source amp would double power as ohms drop? My F5 is 25. Watts at 8ohms,50 watts at 4ohms. Would that be a proper example?
Yes, but to do that, it has to deliver twice the current into a 4 ohm load as it would into an 8 ohm load.
25 watts into 8 ohms equates to 14.1 volts at 1.8 amps (rounding off a bit)
If the load changes and the output voltage of the amp stays constant, the output current of the amp has to change
14.1 volts into 4 ohms is 50 watts, and requires 3.6 amps
14.1 volts into 16 ohms is 12.5 watts, requiring 0.9 amps
Here's where it gets interesting Don't (ever!) forget that virtually all real loudspeakers are not even close to constant impedance devices. The actual impedance changes as a function of frequency. Today's highly complicated, hightly tweaked crossovers can present wildly varying impedance curves to the poor amplifier they're hooked to.
All of which, to my mind, illustrates how useless, or at least misleading, output power can be as a specification/measure of amplifier performance in the real world
I also think it illustrates why some amps and speakers are better combinations than others.
This right here is why this forum is so valuable. You can't beat the knowledge base and experience we have here. Despite the horrible format, I'm really glad this forum is back.
I couldn’t have said that any better! I’ve had the F5 for about 4-5 years,and it sounds magical in its own right. I never had any issues with the 3 or so speaker pairs I’ve thrown at it. Like the F5, the J2 has been driven by an active tube pre,and a passive. The J2 also hasn’t had any issues with the speakers I’ve thrown at it at the volume I listen. However,again,this is absolutely so valuable to have the knowledge base of this forum. I’ve been at this long enough to know what sounds good to my ears,but I’ve never had,or pretended to have the technical knowledge that a lot of you folks have. THANK YOU! I always learn something new here.See my profile for list of gear. -
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I hope I’m not boring you folks,but I’m so freakin excited about this amp! I just put the Nola’s in the system, and total success. This amp DEFINITELY fits in to my long term plan. In brief, I’m planning on retiring in less than three years. My goal is to have some decent gear on hand to rotate between the two systems. I thrive on different flavors. My wife is very cool with all of this as well. She doesn’t really care about SQ,but she is very cool about not breaking my stones about this hobby. Like she said a few years ago about my “addiction “, at least she knows where I am!See my profile for list of gear.
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I hope I’m not boring you folks,but I’m so freakin excited about this amp! I just put the Nola’s in the system, and total success. This amp DEFINITELY fits in to my long term plan. In brief, I’m planning on retiring in less than three years. My goal is to have some decent gear on hand to rotate between the two systems. I thrive on different flavors. My wife is very cool with all of this as well. She doesn’t really care about SQ,but she is very cool about not breaking my stones about this hobby. Like she said a few years ago about my “addiction “, at least she knows where I am!
She must be a good one.
I informed my significant other about the time and cost of this hobby from the start, and it has definitely been the smart move. She lets me have my audio shenanigans while she gets leeway on things like cats and weed. Hope to have your situation when I retire in 30 years haha. -
Thanks GEBBY44. Ya,she’s a keeper! She rides motorcycles too! How much better does that get??See my profile for list of gear.
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Like she said a few years ago about my “addiction “, at least she knows where I am!
My wife “it’s not drugs, booze or whores? Knock yourself out”
DynaudIo Evoke 30, VPI Prime, Soundsmith Zephyr MKIII, PS audio Stellar phono pre, McCormack DNA 0.5 Gold, ARC LS-17se, Eversolo dmp A8, MIT AVT MA ic’s and speaker cables, ps audio stellar power plant 3 -
Today I purchased an Aurender N100H streaming server to replace my Bluesound Node 2i. I am hoping to have the Aurender by the end of next week.Rega Planar 8, Apheta 3 MC , Aria mk2 Phono
Aurender n100h, Benchmark DAC2 HGC
Arcam SR250, Parasound JC5
Revel F208, SVS SB-4000 -
Thursday I upgraded my LCR Seismic Audio XLRs to Monoprice Premiere XLRs.
Been too busy w/Good Friday, a Trail Life Hike, and now, Daddy/Daughter time today to give them a good listen. My Gamer/Aminee son giving them a workout most of the afternoon.
Maybe tomorrow after Resurrection Sunday services.Samsung 60" UN60ES6100 LED, Outlaw Audio 976 Pre/Pro, Samsung BDP, Amazon Firestick, Phillips CD Changer
Canare 14 ga - LCR tweeters inside*; Ctr Ch outside
BJC 10 ga - LCR mids “Foamed & Plugged**”, inside* & out
8 ga Powerline: LR woofers, inside* & out
*soldered **Rob the Man (Xschop)
LR: Tri-amped RTi A7 w/Rotels*. Woofers - 980BX; Tweets & Mids - RB981*
Ctr Ch: Rotel RB981* -> Bi-amped CSi A6
Surrounds: Rotel 981* -> AR 12 ga -> RTi A3
*all connected w/Premiere ICs
5 Subs: Sunfire True SW Signature -> LFE & Ctr Ch; 4 Audio Pro Evidence @ the “Corners”
Power Conditioning & Distribution:
4 dedicated 20A feeds; APC H15; 5 Furman Miniport 20s -
Today, I finally placed my LSA Statement integrated amp back into the rack. Been listening for a few hours now. After almost year out of service, it is working like new again. A bad voltage regulator was the problem. Glad to have some tubes back in the signal path again. Tough choice ahead. Keep the LSA, or stay with the Class D W4S that I’ve been living with for the last few months...For rig details, see my profile. Nothing here anymore...
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Today, I finally placed my LSA Statement integrated amp back into the rack. Been listening for a few hours now. After almost year out of service, it is working like new again. A bad voltage regulator was the problem. Glad to have some tubes back in the signal path again. Tough choice ahead. Keep the LSA, or stay with the Class D W4S that I’ve been living with for the last few months...
Why not keep both? It's always nice to have a spare.See my profile for list of gear. -
Removed the eye bolts that I inflicted upon my 7B's out of necessity when I was a young college student in a small dorm room, and a neophyte audiofool, in order to hang them from the ceiling with chains. I turned (8) 3/4" hardwood dowels to 0.217" for a push fit and prepainted the ends matte black. Tapped them in with a little carpenters glue in the holes first. One less eyesore.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
I already have two spare receivers. Don’t really need to have more than one integrated amplifier. Either I stick with the LSA (which I always thought would be my last amplifier) or go thru a nasty postmortem/resurrection divorce and go for the younger technology! If I stayed with class D, I’d probably sell the Sti and mate some Wyred monos with a decent mid range tube preamp.
Why not keep both? It's always nice to have a spare.
For rig details, see my profile. Nothing here anymore... -
Just bought a new tt and speakers so I set that up and listened for 10 hours to records I’ve not played in years. Some of them I haven’t played in over a decade. It was nice.
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Buzzfuzzwuzz wrote: »Just bought a new tt and speakers so I set that up ...
Howdy!
Say more, please.
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Samsung 60" UN60ES6100 LED, Outlaw Audio 976 Pre/Pro, Samsung BDP, Amazon Firestick, Phillips CD Changer
Canare 14 ga - LCR tweeters inside*; Ctr Ch outside
BJC 10 ga - LCR mids “Foamed & Plugged**”, inside* & out
8 ga Powerline: LR woofers, inside* & out
*soldered **Rob the Man (Xschop)
LR: Tri-amped RTi A7 w/Rotels*. Woofers - 980BX; Tweets & Mids - RB981*
Ctr Ch: Rotel RB981* -> Bi-amped CSi A6
Surrounds: Rotel 981* -> AR 12 ga -> RTi A3
*all connected w/Premiere ICs
5 Subs: Sunfire True SW Signature -> LFE & Ctr Ch; 4 Audio Pro Evidence @ the “Corners”
Power Conditioning & Distribution:
4 dedicated 20A feeds; APC H15; 5 Furman Miniport 20s -
@gp4jesus On the tweeter felt, I beveled the dome opening to a 30deg angle with scissors (120deg inclusive) and punched the holes for the 8 screw heads. On the MW ring I trimmed the flat at the top (which then went on top of tweeter felt) to allow it to mate with the tweeter felt, beveled the inner circle to 45deg, and trimmed a small arc at the bottom to mate with the passive radiator flange.
Trey and his trusty CNC laser cutter did the rest George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
ok so...Gardenstater wrote: »@gp4jesus On the tweeter felt, I beveled the dome opening to a 30deg angle with scissors (120deg inclusive) and punched the holes for the 8 screw heads. On the MW ring I trimmed the flat at the top (which then went on top of tweeter felt) to allow it to mate with the tweeter felt, beveled the inner circle to 45deg, and trimmed a small arc at the bottom to mate with the passive radiator flange.
Trey and his trusty CNC laser cutter did the rest
What about the sound?
Samsung 60" UN60ES6100 LED, Outlaw Audio 976 Pre/Pro, Samsung BDP, Amazon Firestick, Phillips CD Changer
Canare 14 ga - LCR tweeters inside*; Ctr Ch outside
BJC 10 ga - LCR mids “Foamed & Plugged**”, inside* & out
8 ga Powerline: LR woofers, inside* & out
*soldered **Rob the Man (Xschop)
LR: Tri-amped RTi A7 w/Rotels*. Woofers - 980BX; Tweets & Mids - RB981*
Ctr Ch: Rotel RB981* -> Bi-amped CSi A6
Surrounds: Rotel 981* -> AR 12 ga -> RTi A3
*all connected w/Premiere ICs
5 Subs: Sunfire True SW Signature -> LFE & Ctr Ch; 4 Audio Pro Evidence @ the “Corners”
Power Conditioning & Distribution:
4 dedicated 20A feeds; APC H15; 5 Furman Miniport 20s -
ok so...
What about the sound?
Well it is kind of a long story and I guess I was waiting for other people to experience them without my observations possibly influencing them.
Tweeter pad came first. At first I wasn't happy with the muting of the highs and the collapse of my soundstage, although I perhaps perceived a certain increase in smoothness right in the sweet spot. Lots of my listening in my small office room is slightly off axis. After listening nearfield for an extended period my ears were bleeding. This was without any velcro (just scotch tape looped to form double sided) and no mods on my part. SO. I took them off and said........what do ya got to lose........and took out my sharpest pair of scissors and cut a very aggressive 30deg bevel on the inside radius. I was happy with the result visually because I could now see the base of the dome no matter where I stood or sat in the listening room (within reason). I knew that I would still need to make holes for my protruding screw heads on my Peerless plates (4 for magnet and 4 attachment) and get the proper velcro. But the listening experience was transformed. Cymbals were no longer a sibilant "sssssssss" and there was texture and detail to them that was very pleasing. Yes perhaps a bit more muted but extended listening revealed greater clarity and I had actually been thinking lately that my speakers were overly bright with all the other mods I had performed. Perfect!
The next day I punched the holes for the screws and secured them more properly with (4) 3/4" square velcro pads and was even more pleased with the soundstage. Not wider but deeper and the instruments were more precisely placed within. I said to myself that if these small pads could have this much effect I wonder what would happen if I had a speaker cabinet with a large radius roundover on all edges. That's when I had the lightbulb go off that I could slit open some paper towel cardboard tubes and stretch them out over the corners secured with tape just as a proof of concept to see if I could hear any improvement. Those proved too small in length so I went and found some gift wrap tubes and cut them to 15" length and slit them and made (4) edge diffraction diffusors (for want of a better name). Wow! This took it to an even higher level of improvement. Soundstage was super deep now and pretty much all of the above noted effects were even more so. Off axis imaging was almost as good as sweet spot which was a huge bonus!
Fast forward a week or so to the MW ring. I asked Trey to make me one 8" dia. that would be large enough to meet the bottom corners of my tweeter pads. He went a head and did so, and also made partial depth holes for the (4) attachment screw heads and made a bunch of circular passes with the laser to try to make a slot for the basket flange, since my early 7B's are not rabbeted at all. I secured them with 12 pieces of velcro about 1/2" wide by 1" long spaced evenly on the outside of my basket flange. I think that the MW ring at first was upsetting the openness of my soundstage so I did what I did with the tweeter pad, which is to bevel the inner ring, this time to a 45 instead of 30 deg like I did with the tweeter pad. That brought everything back. Before that something was off, although I thought the highs were a bit better still. That's probably because of the nasty MW flange causing diffraction of the highs.
I can say that vocals got noticeably clearer with the MW ring. I noticed that I was picking up on what the actual words were in songs that I have listened to umpteen times but was never sure of. No doubt about it. Highs are a bit better but nowhere near what I got with the tweeter pad of course. Overall I am really happy so far with the combination of these 3 mods.
I am now working on a prototype for the Edge Diffraction Diffusors that might be more ready for prime time and be aesthetically pleasing as well. I'll post here again when I get that done.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Today, I finally placed my LSA Statement integrated amp back into the rack. Been listening for a few hours now. After almost year out of service, it is working like new again. A bad voltage regulator was the problem. Glad to have some tubes back in the signal path again. Tough choice ahead. Keep the LSA, or stay with the Class D W4S that I’ve been living with for the last few months...
Where did you finally get the LSA repaired?
I remember when you first mentioned it needing help. Don't you live in Smyrna?
Harry"Sometimes you have to look to the past to understand where you are going in the future"
Harry / Marietta GA -
I dusted off the stack of cables I've been meaning to get integrated into my system. Does that count?
