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回覆 (142): SIT-1 SIT TIGHT!
Thanks for the info. This V-fet is something new to me. I will try to see if possible to hear one.  
 
Btw, I never really like ss designer that tries to make ss sound "warm" and "tube-like". This is like pretending to be something that it is not. Better yet, "warm" and "tube-like" sound more like distortion to me than merit.  
BenYC
13-08-14
13:13:41
回覆 (141): SIT-1 SIT TIGHT!
Ah! thanks Dr.  
 
Would be nice if he was willing to show the distortion characters of each output devices.  
 
If there is a correlation between distortion and bias current. The meter couldnt show anyway.  
 
The one thing I always tend to dislike is when a designer try to bring in the topic of subjective listening with objective measures. I sometimes feel this topic always contains a certain level of bull shit which only further mislead customer lor!
bobui
13-08-13
11:09:20
回覆 (140): SIT-1 SIT TIGHT!
take a look at this article. it is where nelson talked about different output devices.  
https://www.passdiy.com/project/articles/arch-nemesis
drwkng
13-08-13
10:44:15
回覆 (139): SIT-1 SIT TIGHT!
Ah, forgot the mention that the one and only output resistor is near the far end of the left hand heat sink with three legs. And that I think is what Derek refer as the V-fet or V-fet alike.  
 
bobui
13-08-13
10:33:45
回覆 (138): SIT-1 SIT TIGHT!
Its kind of an interesting product. If you look at the open lid picture posted buy Kris on "#125" below. The many transistors on the heat sink are actually not output transistors. They only have two legs and I beleive they are resistors for bias adjustment. There is a knob on the front panel which you can see is connected to the panel meter and that should be the bias knob.  
 
The amp operate with only one V-fet or V-fet alike transistor. The V-fet loadlines look very similar to a triode except its not as linear as the best output valve without feedback.  
 
Personally, I am interesting to learn or see more V-fet circuit or product but not too excited to spend that kind of money on a Pass SIT first watt. As said, the per watt price is rather too over the top for me.  
 
In terms of spec, the V-fet doesnt look any more linear than a good triode valve. The simple circuitry and no requirement for an output transformer can be nice features for some.
bobui
13-08-13
10:28:38
回覆 (137): SIT-1 SIT TIGHT!
Ben, I haven't heard the SIT-1 yet, but if they are V fets, then it's a different animal. With the limited experience I had with V fet, sound is obviously not tubey, & nothing like the ordinary SS we've encountered.
Derek2A3
13-08-13
09:38:39
回覆 (136): SIT-1 SIT TIGHT!
Just curious... if my speaker can get away with few watts, why not just keep it simple and run on tube SE amp? Or is SIT a totally different sounding animal?  
 
BenYC
13-08-12
22:49:50
回覆 (135): SIT-1 SIT TIGHT!
Pass always claimed to employ the classic single-ended Class A topology, but then all their current amps are balanced design! I have no idea what that means!  
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it is more likely what they super symmetry circuit patented by pass lab . it is a balanced design consisting two gain blocks. may be that is why it only uses P-type.
drwkng
13-08-05
13:35:12
回覆 (134): SIT-1 SIT TIGHT!
>is it a single end design<  
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Pass always claimed to employ the classic single-ended Class A topology, but then all their current amps are balanced design! I have no idea what that means!  
 
 
thekong
13-08-05
12:44:36
回覆 (134): SIT-1 SIT TIGHT!
But you haven't put in your labor cost! :-)  
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As always, just a few cans of beer would do.
bobui
13-08-05
12:36:23
回覆 (133): SIT-1 SIT TIGHT!
silicon-carbide  
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Can also be found in ultra expensive bicyle ceramic brake disc and bearings which is a tech borrowed from cars for its light weight and durability.  
 
bobui
13-08-05
12:28:37
回覆 (134): SIT-1 SIT TIGHT!
Dr King, any idea about those P-Mosfet? I remember reading somewhere, possibly by Nelson Pass himself, that only a few pairs of them could made 200-300W!  
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no idea what they are but then a few pairs of most power mosfet can make 200W. why just P-mosfet? is it a single end design. my use only P-Mosfet but then my amp is circlotron.
drwkng
13-08-05
12:25:22
回覆 (132): SIT-1 SIT TIGHT!
 
 
silicon-carbide  
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This material, more commonly known as Sic, is widely used in making ring guides for the high end fishing rod, due probably to its ultra low friction and unparalleled durability.  
 
 
limage
13-08-05
12:17:30
回覆 (133): SIT-1 SIT TIGHT!
Dr King, any idea about those P-Mosfet? I remember reading somewhere, possibly by Nelson Pass himself, that only a few pairs of them could made 200-300W!  
 
Now, Pass doesn't mention P-Mosfet in any of their Xs amps materials, so maybe they changed to some other output devices in the final design!  
 
 
thekong
13-08-05
12:17:07
回覆 (132): SIT-1 SIT TIGHT!
>Even my poorly made ugly looking little 811-3 mono blocks cost HK$933.- per watt (cost of all parts HK$14,000 divided by 15Watts). <  
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But you haven't put in your labor cost! :-)  
 
 
thekong
13-08-05
12:10:14
回覆 (131): SIT-1 SIT TIGHT!
silicon-carbide devices that are exclusive, we believe, to Pass Labs for use in audio  
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no. the device by semisouth was not even originally intended for audio. i think nelson might have something to do with that being used for audio. now that semisouth has gone south. others have to look for other similar silicon carbide devices. my power amp is also going to use this type of devices.
drwkng
13-08-05
12:08:41
回覆 (131): SIT-1 SIT TIGHT!
the Xs300, at 300W and a mere US$85,000 per pair is just dirt cheap! :-)  
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Thats USD283.3 per watt or HK$2,204.- per watt. Relatively cheap lor!  
 
Even my poorly made ugly looking little 811-3 mono blocks cost HK$933.- per watt (cost of all parts HK$14,000 divided by 15Watts).  
 
bobui
13-08-05
12:03:11
回覆 (130): SIT-1 SIT TIGHT!
If $7,800 per watt can be considered a bargain, then Pass’ new flagship, the Xs300, at 300W and a mere US$85,000 per pair is just dirt cheap! :-)  
 
While I can't find any information now, I seem to remember the output device was some huge P-Mosfet, with which large output could be achieved with a relatively low number of output devices.  
 
Anyway, according to Wayne, the co-designer with Nelson Pass:  
 
“ the design was based on the results of an examination of transfer characteristics of a diverse set of gain devices, including tubes and SITs (silicon-carbide devices that are exclusive, we believe, to Pass Labs for use in audio). The output stage was designed to reproduce the transfer characteristics preferred by a panel of listeners, who lived with a variety of different output stages for a lengthy period of time. “  
 
thekong
13-08-05
11:40:35
回覆 (129): SIT-1 SIT TIGHT!
overpriced turkeys out there from Lamm, Ongaku, FM Acoustic....etc.  
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Home audio in general are over priced la! When a reputable name is attached to a product. There is no way you can justify the price from its function and construction.  
 
An average Alain Mikli or Starck eyewear frame cost about HK$4,500.- plus lens. Final billing expect to be no less than HK$6,000.- A special edition frame can cost as much as HK$120,000.-  
 
Who care about function anway? Meet the eyes is what matter most lor!
bobui
13-08-05
11:13:13
回覆 (128): SIT-1 SIT TIGHT!
So they are Vfets!
Derek2A3
13-08-05
10:38:44
回覆 (127): SIT-1 SIT TIGHT!
 
 
 
 
Morning doc, think I saw somewhere that Nelson paid a hefty sum for the stock. Btw, the list price for the SIT-1 is around $78,000 HKD. If you have the speakers for it, the $7,800 per watt is still a bargain compare to many of the overrated, overpriced turkeys out there from Lamm, Ongaku, FM Acoustic....etc.  
 
 
 
 
kris
13-08-05
10:03:19
回覆 (126): SIT-1 SIT TIGHT!
nelson must have loads of SEMIsouth FET. i only managed to get a quad before it folded.
drwkng
13-08-05
09:35:44
回覆 (125): SIT-1 SIT TIGHT!
 
 
 
 
 
Here's an insert on Static Induction Transistor (SIT) from First Watt - by Nelson Pass............  
 
 
" In the mid 1970's a special variety of Jfet invented in Japan called a Static Induction Transistor (SIT) found its way into the “Vfet” power amplifiers produced by Yamaha and Sony. These amplifiers were produced for several years and then discontinued, but are still highly regarded in the high end audio community.  
 
SIT devices have a unique characteristic which is of particular value for audio amplifiers. Quoting inventor Nishizawa's patent abstract, “(The) drain-current to drain-voltage characteristic simulates the anode-current to anode-voltage characteristic of the triode vacuum tube very closely.” They have found use in radar and other exotic applications, but after Sony and Yamaha ceased production, versions suitable for audio power amplification have been highly prized and difficult to obtain.  
 
Recently there has been renewed interest in SITs, partly because two audio companies have stepped up to the plate and spent the money required to fabricate new devices suitable for audio power amplifiers. The first of these is Digital Do Main in Japan, which has produced two audio amplifiers based on newer versions of original Yamaha Silicon parts. The other is First Watt, which arranged for a production run of a new SIT device using a newer Silicon Carbide process by SemiSouth. "  
 
 photo SIT1med.jpg  
 
 photo first-watt-sit1_1.jpg  
 
 photo firse-watt_sit1_rear.jpg  
 
 photo proto_big-1.png  
 
 
http://firstwatt.com/sitintro.html
kris
13-08-05
08:54:49
回覆 (124): SIT-1 SIT TIGHT!
 
 
 
Morning everyone.  
 
 
Over the weekend, after a successful escape from a Jamo R-909 demonstration (disappointing! almost as dull as the R-907), I snuck into a brief audition with Nelson Pass' latest SIT-1 (SIT = Static Induction Transistor), the very first mono-block under First-Watt. The fact that I am waking this thread from a 2 years coma is unequivocal confirmation that SIT-1 made quite a debut!  
 
Unlike Bob Carver's patented  "tracking downconverter" design in the 90s (groundbreaking at the time), squeezing thousands of brute watts into a tiny compartment - truly an inspiration for Class-D amps and LFE subwoofers. The SIT-1, I believe, changes the actual metamorphoses in sound for Class-A amplification as we know it. Felt like listening to a Solid-state version of a single-ended  OTL amp. Though, I only spent an hour or so with the SIT-1 (and probably not under ideal set-up), the tumbling effect from this "10 Tsunami Watts"  is far from over.   
 
Among the many impressive attributes, the SIT-1 delivered "bloom and sparkles" on each note unfolding from what appeared to be a black & bottomless background with ample sound stage (nothing like tube!). The details never scream at you, just sounded organically natural. In short, the SIT-1 possesses the kinda 'rare magic' that makes you want to replay all your old recordings over again. The mission of a great amp!  
 
More to come..............  
 
 
note: the loudspeakers used for the audition was a pair of 89 dB Evantus Phobos (with Solution Preamp 520 I think?).  
 
 photo IMG_1706.jpg  
 
 photo IMG_1708.jpg  
 
 photo IMG_1715.jpg  
 
 photo IMG_1710.jpg  
 
kris
13-08-05
08:48:28
回覆 (123): Class A - the Recycle Condom way...........
Oh my God.........
http://cgi.audiogon.com/cgi-bin/auc.pl?ampstran&1296959183
icefox
11-01-29
03:04:16
回覆 (122): Class A - the XA way...........
 
 
That is if I win the lottery ;-)  
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No need. Just get 老狐狸 to buy the whole enchilada, and you'll do the run in for him.
kris
11-01-26
09:54:54
回覆 (121): Class A - the XA way...........
 
>You have my full support on that. Spiritually speaking of course :-] <  
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The Fullrange needs to be at least bi-amped, so 2 pairs is the bare minimum. For an all out assault, probably should go for 3-ways active with 3 pairs of XA160.5, or better yet XA200.5! That is if I win the lottery ;-)  
 
thekong
11-01-26
09:51:14
回覆 (120): Class A - the XA way...........
 
 
 
 
 
So, 2 pairs of them would probably be enough for the Apogee Fullrange ;-)  
 
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You have my full support on that. Spiritually speaking of course :-]
kris
11-01-26
09:33:05
回覆 (119): Class A - the XA way...........
Morning Kris,  
 
Ah...MRA…the real beast, claimed to be able to deliver 8,000W into 1ohm, and 16,000W into 0.5ohm :-O I think it is probably the only audio power amp in history that can do that! However, I don’t think it is really pure Class A in the classic sense, as Krell was already using what they called the Sustained Plateau Bias technology, which could automatically adjust the bias according to the signal demand!  
 
The Pass XA.5 series may also be considered as not a pure Class A design. Take the XA30.5 as an example, according to the measurement by Stereophile, while it could deliver 30W in Class A, it could actually reach 130W into 8ohm and 195W into 4ohm. The higher figures are in Class AB I assume.  
 
As such, I would also estimate that the XA160.5 can delivery something like 500W into 8ohm, and 800W into 4ohm. So, 2 pairs of them would probably be enough for the Apogee Fullrange ;-)  
 
thekong
11-01-26
09:22:58
回覆 (118): Class A - the XA way...........
 
 
 
 
 
Think Koay also did something similar with his rig as well?!  
 
Photobucket
kris
11-01-26
08:40:08
回覆 (117): Class A - the XA way...........
 
 
 
 
 
 
 
The manly one's like to date lusty Apogees also :-)  
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kongmester, these big boys in the lusty Apogees pic look like the XA 200 /160, squeezing that kind of power in pure, uninhibited Class A mode definitely is a world of it's own. Remember our Malay encounter with Ben's 1000 watts Krell MRA, how our scape were shacking during Bach's organ Toccata?? In order to liberate this level of brut Class A power, the actual power feed into the house is no picnic. Legal or not, think Ben pulled directly from the street, 60A (X4) straight up into the ass of the MRAs!!! The way it should be:-o  
 
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kris
11-01-26
08:34:40
回覆 (116): Class A - the XA way...........
>I recall seeing some post in AA saying that using Class A Watt to fry eggs, it reduces the cholesterol by half......<  
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With the price and electricity bills that you have to pay for Class A amps, you probably need to cut down on food consumption, so further reduce your cholesterol level :-)  
 
In return, you get a really "大lam覓" system ;-)  
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One stone kills TWO birds!!! What can you ask for more?
icefox
11-01-25
12:20:56
回覆 (115): Class A - the XA way...........
 
>I recall seeing some post in AA saying that using Class A Watt to fry eggs, it reduces the cholesterol by half......<  
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With the price and electricity bills that you have to pay for Class A amps, you probably need to cut down on food consumption, so further reduce your cholesterol level :-)  
 
In return, you get a really "大lam覓" system ;-)  
 
thekong
11-01-25
12:08:52
回覆 (114): Class A - the XA way...........
I recall seeing some post in AA saying that using Class A Watt to fry eggs, it reduces the cholesterol by half...... sounds like another good use of Class A Watt. ^__^  
 
Frying eggs like this is really CHOK!!!!
icefox
11-01-25
11:51:14
回覆 (113): Class A - the XA way...........
Yes, you would; there isn't any turntable there ;-)  
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I have plenty !!! but of course I can make another one ^__*
daiwok
11-01-25
11:39:57
回覆 (112): Class A - the XA way...........
 
>I would not say no to a system like this ^__^ <  
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Yes, you would; there isn't any turntable there ;-)  
 
 
thekong
11-01-25
11:29:38
回覆 (111): Class A - the XA way...........
I would not say no to a system like this ^__^
daiwok
11-01-25
11:11:36
回覆 (110): Class A - the XA way...........
>The trouble with pure Class A watts is that they're stingy and like to date high sensitivity speakers.<  
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The manly one's like to date lusty Apogees also :-)  
 
thekong
11-01-25
09:37:43
回覆 (109): Class A - the XA way...........
 
 
The trouble with pure Class A watts is that they're stingy and like to date high sensitivity speakers. I have a funny feeing that pumping them into these Podium horn dipole panels may be an interesting date:-)
kris
11-01-25
08:14:48
回覆 (108): Class A - the XA way...........
 
 
The the old Aleph.....
kris
11-01-25
08:06:56
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