Do you need specifically NPN? And yes, details on application would help.hoodun said:Does anyone know of a replacement transistor for 2SC2545? I am looking at 2N5961. Is there something better out there made for low noise audio. I prefer to pay less than $1.
I don't understand. You ask for a transistor that's specifically designed for low noise at high collector current (>1mA) with low impedance sources, and these two products are transformer-based, thus providing a rather high source impedance (about 10k). This is typically the domain of more traditional LN transistors, designed to operate at about 50-100uA collector current, of which there are plenty e.g. BC560.hoodun said:Futurlec is out of them. So they are pretty much absolete unsless you want to pay up to $15 a transistor on ebay.
I would be using them for mic pres. Langevin am-16 replacement and PM1000 replacements. MPSA-18 looks like it is the best I can do at the moment.
abbey road d enfer said:I don't understand. You ask for a transistor that's specifically designed for low noise at high collector current (>1mA) with low impedance sources, and these two products are transformer-based, thus providing a rather high source impedance (about 10k). This is typically the domain of more traditional LN transistors, designed to operate at about 50-100uA collector current, of which there are plenty e.g. BC560.hoodun said:Futurlec is out of them. So they are pretty much absolete unsless you want to pay up to $15 a transistor on ebay.
I would be using them for mic pres. Langevin am-16 replacement and PM1000 replacements. MPSA-18 looks like it is the best I can do at the moment.
That's not what I wrote. There is a nuance. There are many LN transistors that are intended for low-Ic/medium source Z applications. That was what transistors were capable of at the beginning. After, when processes improved, there were some transistors that were optimized for lower Z at the cost of increasing the operating current. 2SC2545 is precisely of that type. There was time where manufacturers found interest in these applications and introduced remarkable designs such as 2SB737 (lowest Rbb' in the universe for a single transistor) or LM394 (2x50 paired transistors monolithic)hoodun said:abbey road d enfer said:I don't understand. You ask for a transistor that's specifically designed for low noise at high collector current (>1mA) with low impedance sources, and these two products are transformer-based, thus providing a rather high source impedance (about 10k). This is typically the domain of more traditional LN transistors, designed to operate at about 50-100uA collector current, of which there are plenty e.g. BC560.hoodun said:Futurlec is out of them. So they are pretty much absolete unsless you want to pay up to $15 a transistor on ebay.
I would be using them for mic pres. Langevin am-16 replacement and PM1000 replacements. MPSA-18 looks like it is the best I can do at the moment.
You seem to understand much better than I do. So in transformer based pre amps there is no benefit for low noise transistors?
Don't believe everything you read on forums!I've read the contrary though Im just going off of diy forums.
In general no. The transformer provides the initial low-noise amplification, after that it doesn't matter much.hoodun said:So in transformer based pre amps there is no benefit for low noise transistors?
Indeed. They are surprisingly low-noise, considering they are not advertised for it. There are no noise specs for them. How did you get the info about Rbb'? Did you compute it out of measurements?merlin said:In general no. The transformer provides the initial low-noise amplification, after that it doesn't matter much.hoodun said:So in transformer based pre amps there is no benefit for low noise transistors?
But if you care, the BC337/327 is always my go-to transistor. It has Rbb around 30ohms which is remarkably quiet for a cheap, general purpose device.
Transistors designed for switching significant current will have low Rbb to manage internal resistive losses. Historically transistor processes were not very clean so low Rbb devices were not always free of other noise contamination. Back in the day some designers would secretly screen medium power transistors to use in low noise applications. Since then the semiconductor processes have gotten a lot cleaner so I expect any number of medium power devices may be low noise. Another aspect of dedicated low noise devices is high beta so medium power devices may be good but still not optimal for low noise design.abbey road d enfer said:Indeed. They are surprisingly low-noise, considering they are not advertised for it. There are no noise specs for them. How did you get the info about Rbb'? Did you compute it out of measurements?merlin said:In general no. The transformer provides the initial low-noise amplification, after that it doesn't matter much.hoodun said:So in transformer based pre amps there is no benefit for low noise transistors?
But if you care, the BC337/327 is always my go-to transistor. It has Rbb around 30ohms which is remarkably quiet for a cheap, general purpose device.
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