The B2 looks nice, it's from a time when wires heatsinks and transformer were used in audio gear. It should sound alright on account of that alone.
Can someone request a quote for 2500 jfets? It shouldn't be so hard to get 100 people needing 25 pieces.
Can someone request a quote for 2500 jfets? It shouldn't be so hard to get 100 people needing 25 pieces.
I smell Groupy Buy.
This club is 1 big gangbang, gimme 25.
(i'm probably the only one that gets a headache from the highs of Yamaha gear, their engineers always find a way to screw things up. The Sumo Andromeda was in the same pricerange and time frame as the B2, and beat the Yamaha by a longshot)
This club is 1 big gangbang, gimme 25.
(i'm probably the only one that gets a headache from the highs of Yamaha gear, their engineers always find a way to screw things up. The Sumo Andromeda was in the same pricerange and time frame as the B2, and beat the Yamaha by a longshot)
Steve Eddy said:
The 2SK18/2SJ60 (or is it the other way around?) have a 5A Id and 63W Pd limit which is small by today's power FET standards. But, for an application like NP's latest creation I would think that is enough.
Jan Didden
Steve Eddy said:
Funny you should mention, I built a nice little pair of channels
earlier this year using 50 2sK389's per channel biased at 1 amp
with a current source at 22 V supply.
Worked fine.
😎
Mr Pass,
mind if i ask what the reason was for placing 50 of such relative pricy devices in parallel ?
mind if i ask what the reason was for placing 50 of such relative pricy devices in parallel ?
Nelson Pass said:
Coolness!
Doug ("Digger") told me about a small amp you'd made at Threshold yearsa go that used a boatload of small signal bipolars (A42s and 92s I think). Said it ultimately worked, but stability-wise it was twitchier than a crack *****.
So, by 50 2SK389s, you're ultimately talking about 100 JFETs total seeing as it's a dual JFET device, yes?
se
I managed to buy 50 2SK389, but it was like pulling teeth to get the BL. With that in mind, it would take all of my stock to build one channel. However, I think it would be fun to try. Maybe I should dredge out an old mono recording to listen to.
I've also managed to get 2SJ109BL, though not as many. Unfortunately, I've never managed to locate 2SK170BL or 2SJ74BL. All I've been able to source is GR for either of those.
VI of any of them? Forget about it. Jam sent me two 2SK389VI back before he turned to the dark side. (Thanks, Jam.) Unfortunately, only having two, I'm saving them for a special occasion. What, you ask? No idea. I suppose I will know when I get the inspiration for the circuit.
A better candidate than the 2SK/2SJ, current-wise, would be the J310/J271 JFETs. Note that they are both single devices, not duals. The J310 minimum Idss is--I think--25mA and goes up to 60mA, although the ones I've got tend to cluster in the 30-40mA range. The fly in the ointment is the Idss for the J271, which starts at something like 6mA instead of 25--thus you have to buy more devices in order to have a chance of matching the Idss. Once you're past that hurdle, you're in fair shape for building a massively parallel amplifier with complementary devices as long as you don't overdo the rail. (Quoting from memory, the J310 is 25V; the J271 is 30V.)
Besides, I think it would it would look cool.
Depending on the rail/currrent you might be able to get by without heatsinks, which would be kinda fun. Also, setting aside the power supply, you could fit the circuit into a 1U rack chassis, which would be nifty.
Hmmm...I'd better watch it. I'm on the verge of talking myself into something, here.
Grey
I've also managed to get 2SJ109BL, though not as many. Unfortunately, I've never managed to locate 2SK170BL or 2SJ74BL. All I've been able to source is GR for either of those.
VI of any of them? Forget about it. Jam sent me two 2SK389VI back before he turned to the dark side. (Thanks, Jam.) Unfortunately, only having two, I'm saving them for a special occasion. What, you ask? No idea. I suppose I will know when I get the inspiration for the circuit.
A better candidate than the 2SK/2SJ, current-wise, would be the J310/J271 JFETs. Note that they are both single devices, not duals. The J310 minimum Idss is--I think--25mA and goes up to 60mA, although the ones I've got tend to cluster in the 30-40mA range. The fly in the ointment is the Idss for the J271, which starts at something like 6mA instead of 25--thus you have to buy more devices in order to have a chance of matching the Idss. Once you're past that hurdle, you're in fair shape for building a massively parallel amplifier with complementary devices as long as you don't overdo the rail. (Quoting from memory, the J310 is 25V; the J271 is 30V.)
Besides, I think it would it would look cool.
Depending on the rail/currrent you might be able to get by without heatsinks, which would be kinda fun. Also, setting aside the power supply, you could fit the circuit into a 1U rack chassis, which would be nifty.
Hmmm...I'd better watch it. I'm on the verge of talking myself into something, here.
Grey
Steve Eddy said:
Yes, at 10 mA/device. The boatload of TO-92's worked fine, but
realistically, neither of these are practical approaches.
Give my regards to the boys.
😎
I once started something I called The Lily Guilder's Society. Its members were those not content to leave well enough alone.
The primary requirement for attempting to guild the lily is imagination.
The thing about imagination is that some people have none. Some people have a little. Others have quite a bit.
There is another parameter. If imagination is the gas pedal, then there is a nay-saying power to counteract it that is analogous to the brakes. Again, some people have more...and some have less.
You get all the possible permutations, but the people who change the world are generally the ones with a lot of imagination and little or no self-restraint.
That's assuming that they don't blow themselves up or get burned at the stake by those less visionary.
Grey
The primary requirement for attempting to guild the lily is imagination.
The thing about imagination is that some people have none. Some people have a little. Others have quite a bit.
There is another parameter. If imagination is the gas pedal, then there is a nay-saying power to counteract it that is analogous to the brakes. Again, some people have more...and some have less.
You get all the possible permutations, but the people who change the world are generally the ones with a lot of imagination and little or no self-restraint.
That's assuming that they don't blow themselves up or get burned at the stake by those less visionary.
Grey
Steve Eddy said:
Yes. TO-3. I have several amps that use them, and I also have a bunch of spares, just in case. The TA-7 uses them in a cascode setup. The difference with the setup from NP is that firstly, they are push-pull, and secondly, the JFETS are used as the cascode device and there is a fast, low voltage bipolar as the main amplifier device. Just the other way around....
Jan Didden
Finally found the datasheet for the 2SK389. I think the 2N6550, which I'd been looking at for some time already would be a better choice. It has just slightly higher input capacitance, but it has a much higher IDSS and each device can dissipate 400mW in free air compared to the 200mW per device for the 2SK389.
Which means I should be able to get by with about half the number of actual JFETs as Nelson used and reduce the input capacitance by nearly half in the process. Not to mention that the 2N6550 is still being produced by at least two companies (InterFET and Crystalonics).
se
Which means I should be able to get by with about half the number of actual JFETs as Nelson used and reduce the input capacitance by nearly half in the process. Not to mention that the 2N6550 is still being produced by at least two companies (InterFET and Crystalonics).
se
janneman said:
Ah, ok. Yeah, I'd been looking around a bit to try and find a few of those to play with. Just looking to do a simple, single-ended, choke loaded follower.
se
There is guite a bit of interest in Sony and Yamaha VFET amps on the AudioKarma site. In addition, lots of good information on this site:
http://www.thevintageknob.org/
Yamaha had the B-1 and B-2 amplifiers. Sony had a first generation with the TA-4650, TA-5650, and TA-8650 integrateds and the TAN-5550 and TAN-8550 amplifiers. These use the VFETs as the power transistors. Sony also had a second generation with the TA-F7 or TA-F7B integrateds and the TA-N7 or TA-N7B (the 'B' designates a different colored front panel) amplifiers. As mentioned above, these are a hybrid design in which the VFET devices are in a cascode arrangement with BJT devices. Prices on all of these on ebay have gone up quite a bit over the last couple of years.
Steve.
http://www.thevintageknob.org/
Yamaha had the B-1 and B-2 amplifiers. Sony had a first generation with the TA-4650, TA-5650, and TA-8650 integrateds and the TAN-5550 and TAN-8550 amplifiers. These use the VFETs as the power transistors. Sony also had a second generation with the TA-F7 or TA-F7B integrateds and the TA-N7 or TA-N7B (the 'B' designates a different colored front panel) amplifiers. As mentioned above, these are a hybrid design in which the VFET devices are in a cascode arrangement with BJT devices. Prices on all of these on ebay have gone up quite a bit over the last couple of years.
Steve.
Steve Eddy said:
Not such a good choice. Assuming you are using them as followers (a reasonable assumption for an output stage) then the 2N6550 has 3x the input capacitance at 10 Vds. You are completely overlooking the transconductance, which is extremely important for this application. At 10 mA (a reasonable value for this application), the 2N6550 might have a bit more transconductance, but nothing like 3x.
A better choice would be the 2SK170. It's still in production, is also rated at 400 mW, has a slightly higher voltage rating than the 2N6550 and has a complement available (2SJ74) if you want one.
By the way, I've been thinking about doing this for the last 10 years, but have never actually built the thing. If we ever do, please don't accuse me of copying Nelson!
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