At this point I have adequate and matching stocks of 2SB737 transistors and PCBs for various purposes. The search for new parts is for new designs and new PCBs.
I have 2SD786 in quantities and we could swap some and then have complementary pairs
I agree with you RayCtech, I use BC327/337 from Fairchild and nxp with good results, the smd part is BC807/817, using BC327/337 in audio applications is nothing new, especially in MC phono preamps, where low noise is a must . If more than 45v is required , one must use a cascode.
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If you used your fingers to count up ALL of the commercial data sheets that EVER specifically mentioned that parameter, you would probably have enough fingers left over to grab your coffee cup (or beer mug).
Dale
Take a look at 2SC3324 / 2SA1312. Still active part.
http://www.diyaudio.com/forums/anal...smd-high-voltage-discrete-diamond-buffer.html
http://www.diyaudio.com/forums/parts/222485-lowest-noise-bjt-transistor.html
http://www.diyaudio.com/forums/solid-state/17285-ultra-low-noise-transistors.html
Patrick
http://www.diyaudio.com/forums/anal...smd-high-voltage-discrete-diamond-buffer.html
http://www.diyaudio.com/forums/parts/222485-lowest-noise-bjt-transistor.html
http://www.diyaudio.com/forums/solid-state/17285-ultra-low-noise-transistors.html
Patrick
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Hi Patrick
Just had a look at your diamond buffer.
Do the base stoppers really need to be as much as 300 ohms?
Doesn't that make the low Rbb almost irrelevant?
A really low Rbb of say 2 ohms or one even twenty times worse will still produce practically the same noise once in series with 300 ohms.
Best wishes
David
MCM Electronics: Home and Pro Audio/Video, Security and Test Equipment
search for 2sa992 and 2sc1845
The base spreading resistance of BC550 is more than 100ohms, the Rbb from BC327 is in the 30ohms, the BC327 has lower noise than BC550.
Some transistors from zetex, also have very low base spreading resistence. But they do not indicate noise parameters or Rbb values in the datasheet, I think the main reason is that the Market for low noise bjt is nowadays very small, but there are some threads about Rbb measurements in the forum.
I have buy some biss transistors from NXP to test. But as I said before I have very good results with BC327/337, very low noise, high linearity, high hfe, and also high current capable, and of course very cheap
And also significantly higher noise at low frequencies
compared to a BC109C/560C , it s not by chance that
the Tanberg and other Phillips used thoses latter ones
for the first stage of their RIAA preamps back in the 70s.
Thank you everyone who has replied. Quite a long list of parts has been drawn-up. Some parts are available, whilst others are not. I'm in the process of sourcing small quantities of the available transistors for testing and assessment......
Thinking particularly about reply #12, using small SMD parts is not a problem in itself; the problem is knowing what the parts are. The good members here have suggested a number of interesting devices. Whilst the performance of some of the application-specific audio ICs is impressive, when working on pushing the boundaries of performance beyond their capabilities, there are times when there is nothing like a really low-noise transistor.
Thanks,
Gareth.
Thinking particularly about reply #12, using small SMD parts is not a problem in itself; the problem is knowing what the parts are. The good members here have suggested a number of interesting devices. Whilst the performance of some of the application-specific audio ICs is impressive, when working on pushing the boundaries of performance beyond their capabilities, there are times when there is nothing like a really low-noise transistor.
Thanks,
Gareth.
jfet?
Hi Gareth,
You have mentioned bjt's, but the NXP BF862 jfet is a fine component to use, for very low noise front ends. It is cheap and readily available. Voltage ain't so much, for HV cases, so would need a cascode.
Fairchild FJV992 & FJV1845 are available & so is the Toshiba 2sa1312/c3324 as cascode devices.
One thing about SOT-23 is that they (industry) have finally agreed on a common footprint.
Cheers
Rick
Hi Gareth,
You have mentioned bjt's, but the NXP BF862 jfet is a fine component to use, for very low noise front ends. It is cheap and readily available. Voltage ain't so much, for HV cases, so would need a cascode.
Fairchild FJV992 & FJV1845 are available & so is the Toshiba 2sa1312/c3324 as cascode devices.
One thing about SOT-23 is that they (industry) have finally agreed on a common footprint.
Cheers
Rick
Although this thread is long finished perhaps these? 2N4401/3 2SA1085 2SA970 ? RS can supply. I think John Curl said the 2N's were switching devices that were found to be OK. I recently have increased the gain on a Quad 33 to about 600 on the phono side to suit a Denon DL110. The Quad uses BC109. It is the lowest noise pre amp I ever had. It's modest 70 dB noise figures seems less than the truth. Even with the new gain I suspect it is easilly that. My feeling is no op amp will beat this. Maybe Quad selected the devices? They use 109's though out. The less good ones higher up ? In the days of EF 86 that would be done.
I used BC327/337-40 as my general purpose devices.
I used BC327/337-40 as my general purpose devices.
Hi Nigel,
Thanks for your reply; the thread is old, but the interest in trying to find low noise transistors is still active.
Your post encouraged a check on the RS website. They have unfortunately discontinued the 2SA1085 and 2SA970. They do seem to stock 2N4401 and 2N4403.
Thanks again,
Gareth.
Thanks for your reply; the thread is old, but the interest in trying to find low noise transistors is still active.
Your post encouraged a check on the RS website. They have unfortunately discontinued the 2SA1085 and 2SA970. They do seem to stock 2N4401 and 2N4403.
Thanks again,
Gareth.
Hi Gareth. Give this a try.
This is a do everything low noise device of very high voltage and gain. Buy them now. A BC560 on steroids. Possibly non ROHS so not automatically given.
Buy Bipolar Transistors 2SA1085E PNP Bipolar Transistor, -100 mA -120 V HFE:400 V 90 MHz, 3-Pin TO-92 Renesas Electronics 2SA1085E online from RS for next day delivery.
This is a do everything low noise device of very high voltage and gain. Buy them now. A BC560 on steroids. Possibly non ROHS so not automatically given.
Buy Bipolar Transistors 2SA1085E PNP Bipolar Transistor, -100 mA -120 V HFE:400 V 90 MHz, 3-Pin TO-92 Renesas Electronics 2SA1085E online from RS for next day delivery.
The 2N4401-3 are old devices that worked well at the time for low Z sources. They will still work in general, but they have low beta that will limit their usefulness. The BC109 has even higher voltage (low Z sourced), but OK current noise (high Z sourced). It is also old and virtually obsolete. I would compare it to the 2N5089.
Hi Guys
BC413-415 were out of production many years ago, as far as I know, they were certainly difficult to get in north America for the past decade or so. Thier noise spec is identical to BC550C-560C, at least as far as tabled data goes, with a 2dB NF. Most BJTs listed for audio are 5-10dB.
2SC3324-2SA1312 is listed in the 1991 data books and is still current production. It's production future must have some assurance since Bryston uses it in their new amp models. Its data suggests it is one of the lowest noise BJT sets ever made. But... it's surface mounted as others have posted. They had the BC413-415 made in their own part numbers for over twenty years and are switching the new designs over to the Toshiba SMs.
The BC550/560 is periodically "phased out" inasmuch as manufacturers change part numbers to reflect lead-free and then Rohs, with some going to SM versions only.
There were many 2SA/2SC dual BJTs in 5-pin SIPs that had 1.5dB NF, used for amp front ends. For those who cannot build an amp without emitter degeneration on the input stage, these are of little use, but excellent devices. I used them in lots of amps following the examples of many OEM designs.
Digital audio is much cheaper and less expensive - not the same thing - so a lot of the good jfets pairs and BJT pairs are being EOLed. Contrasting this is a small expansion of very good output BJTs. The current form of the MJL1302AG-MJL3281AG states that the devices are constructed to a tight gain tolerance within 10%. These were al;ways more highly complimentary than Motorlola's own device line, but now they are even moreso. of course, this improvement of fabrication methods has spilled into the MJL21193-6 line.
One still has to be wary of super-high Pa ratings in standard packages. All those 300W+ mosfets need liquid cooling and have no real application in linear.
For input stages and basically all things I construct, I will stay with through-hole construction. SM is beyond my visual range and working with a magnifier is not for me. Besides, I like things that can be serviced.
Have fun
BC413-415 were out of production many years ago, as far as I know, they were certainly difficult to get in north America for the past decade or so. Thier noise spec is identical to BC550C-560C, at least as far as tabled data goes, with a 2dB NF. Most BJTs listed for audio are 5-10dB.
2SC3324-2SA1312 is listed in the 1991 data books and is still current production. It's production future must have some assurance since Bryston uses it in their new amp models. Its data suggests it is one of the lowest noise BJT sets ever made. But... it's surface mounted as others have posted. They had the BC413-415 made in their own part numbers for over twenty years and are switching the new designs over to the Toshiba SMs.
The BC550/560 is periodically "phased out" inasmuch as manufacturers change part numbers to reflect lead-free and then Rohs, with some going to SM versions only.
There were many 2SA/2SC dual BJTs in 5-pin SIPs that had 1.5dB NF, used for amp front ends. For those who cannot build an amp without emitter degeneration on the input stage, these are of little use, but excellent devices. I used them in lots of amps following the examples of many OEM designs.
Digital audio is much cheaper and less expensive - not the same thing - so a lot of the good jfets pairs and BJT pairs are being EOLed. Contrasting this is a small expansion of very good output BJTs. The current form of the MJL1302AG-MJL3281AG states that the devices are constructed to a tight gain tolerance within 10%. These were al;ways more highly complimentary than Motorlola's own device line, but now they are even moreso. of course, this improvement of fabrication methods has spilled into the MJL21193-6 line.
One still has to be wary of super-high Pa ratings in standard packages. All those 300W+ mosfets need liquid cooling and have no real application in linear.
For input stages and basically all things I construct, I will stay with through-hole construction. SM is beyond my visual range and working with a magnifier is not for me. Besides, I like things that can be serviced.
Have fun
It is such a shame Rbb- isn't listed for transistors. Vbc that is I never have found very useful. Am I wrong to think Vceo more important ?
I would guess any power transistor is likely to be worth trying. BC639/140 should be doing something as they are mini power types ( BD 139/140 it is said ). BC337/327 also are reasonable. My tests of cheap 2N3055 showed them to be modertate, I had hoped for more. This was where 2 A was the test limit.
It is interesting about lineartiy. The data often says switching and nothing about audio. I have always found it hard to know why a transistor is only good for switching. If a loop feedback design I never give it a second thought. However in a Blomley 50 watt design it stresses the need for switching types! I find it hard to beleive any 100 to 300 MHz type wouldn't be suitable for " switching ".
I could imagine BF 720/721 OK. These might be the old BF469/470 in SMD. If so how nasty to not make in TO126. These devices are in the Folklaw as being special. The TO126 will allow cooling so perhaps better than MPSA42/92. It would be interesting to know if any of those go below 1 nV. I see transistors as better pentodes. When people say a transistor is more linear I feel a bit lost. We seldom use them open loop so why get excited ? I guess gain verses linearity is the question.
That being true. What is the optimum gain/voltage/noise compromise from phono to 200 watts RMS ? I dare say 9 V , 24 V , 120 V . The 9V for 75 uS to output level 50 mV rms. 24 V right up to VAS. The need for +/- comes into it. Some say the input transistor of the power amp should be very low noise. Why not as it is not difficult to find them. 2SA1085 is a strange device, fast, quiet, moderate Ft, can cope with a bit more heat and high voltage plus high gain. The ultimate long tail pair device and 0.55 nV if memory correct?
Here is a question. If looking for the ultimate linearity, gain and noise would not a collector bootstrap from a low noise PSU be best ? A simple op amp type circuit where this device looks like a VAS might be OK ? This would make the device think it is driven from much higher voltage. One could take the bootstrap out in seconds to hear how good it is. A CCS is a noise source. CCS is like antibiotics these days. Used when not required. Bootstrap vitimin C?
I would guess any power transistor is likely to be worth trying. BC639/140 should be doing something as they are mini power types ( BD 139/140 it is said ). BC337/327 also are reasonable. My tests of cheap 2N3055 showed them to be modertate, I had hoped for more. This was where 2 A was the test limit.
It is interesting about lineartiy. The data often says switching and nothing about audio. I have always found it hard to know why a transistor is only good for switching. If a loop feedback design I never give it a second thought. However in a Blomley 50 watt design it stresses the need for switching types! I find it hard to beleive any 100 to 300 MHz type wouldn't be suitable for " switching ".
I could imagine BF 720/721 OK. These might be the old BF469/470 in SMD. If so how nasty to not make in TO126. These devices are in the Folklaw as being special. The TO126 will allow cooling so perhaps better than MPSA42/92. It would be interesting to know if any of those go below 1 nV. I see transistors as better pentodes. When people say a transistor is more linear I feel a bit lost. We seldom use them open loop so why get excited ? I guess gain verses linearity is the question.
That being true. What is the optimum gain/voltage/noise compromise from phono to 200 watts RMS ? I dare say 9 V , 24 V , 120 V . The 9V for 75 uS to output level 50 mV rms. 24 V right up to VAS. The need for +/- comes into it. Some say the input transistor of the power amp should be very low noise. Why not as it is not difficult to find them. 2SA1085 is a strange device, fast, quiet, moderate Ft, can cope with a bit more heat and high voltage plus high gain. The ultimate long tail pair device and 0.55 nV if memory correct?
Here is a question. If looking for the ultimate linearity, gain and noise would not a collector bootstrap from a low noise PSU be best ? A simple op amp type circuit where this device looks like a VAS might be OK ? This would make the device think it is driven from much higher voltage. One could take the bootstrap out in seconds to hear how good it is. A CCS is a noise source. CCS is like antibiotics these days. Used when not required. Bootstrap vitimin C?