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New TO-3 Output Transistors

Sorry for bringing this thread back to life, but there was one notable omission from Echowars list of amps that 2ST5949/2ST2121 may be good for... and maybe for good reason, so I have to ask the question.
Does anyone here know of a good reason why the new 2ST5949/2ST2121 would not be suitable replacement for 2SA1065/2SC2489 (kenwood KA-907 - 50Mhz)? It seems to me that these would be a good substitution, but there are far more knowledgeable engineers here then I.

before I chuck these into one of these units I thought I would ask.
 
Hyperion said:
Some of the 'crowd' ARE interested and have been reading this thread with interest. :yes:

:lurk:
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Some read... and re-read... and make notes! :yes: :D
This is one of those threads that are informative, genuinely useful, and motivating/inspirational! Thanks to all who contributed :ntwrthy:, from another who
... :lurk:
 
These are interesting. I am planning an amp build using a 2x60 secondary toroidal tranny and am thinking of using an lme49811 chip for first stage, would a pair for each channel of these work for a current stage?
 
megawatt said:
Sorry for bringing this thread back to life, but there was one notable omission from Echowars list of amps that 2ST5949/2ST2121 may be good for... and maybe for good reason, so I have to ask the question.
Does anyone here know of a good reason why the new 2ST5949/2ST2121 would not be suitable replacement for 2SA1065/2SC2489 (kenwood KA-907 - 50Mhz)? It seems to me that these would be a good substitution, but there are far more knowledgeable engineers here then I.

before I chuck these into one of these units I thought I would ask.
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I answered your PM way back when, but I'll do so again here. These would be fine for the KA-907. Even at 25MHz. they are still only about 1/2 the speed of the originals (which were some seriously rare Panasonic devices, IIRC).
epoch5 said:
EW is this something a total idiot as myself could do? :D
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On the L-07MII's? The bias has to be set, and it's a bit technical to do right on that amp. Plus, it's messy. The old thermal grease has to be cleaned off the heatsinks, and it's a sucky job.
rob29 said:
These are interesting. I am planning an amp build using a 2x60 secondary toroidal tranny and am thinking of using an lme49811 chip for first stage, would a pair for each channel of these work for a current stage?
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High-speed amps are not easy to get right for DIY, but consider that if you're building something for yourself there's not a lot of reasons to stay with the steel TO-3 package. Also, consider that in the plastic packages super high-speed is fairly common. I don't know if the plastic versions of these transistors are any faster, but if they aren't, they wouldn't really be anything to raise an eyebrow about. It's fast devices in the TO-3 package that makes these special, and if you're DIYing, then the TO-3 sucks to work with (but does have real advantages when power dissipation is considered, if it matters in your application).
 
Be careful when comparing fT's of transistors :nono:

The fT of a transistor varies with collector-emitter voltage and collector current and the highest value of fT is usually quoted in the data sheet and usually obtained at an amp or so of collector current and not the typical 20 mA of quiescent current in most amps. fT is much lower at these lower currents !!

When comparing fT's it is recommended to look at the fT verses Ic chart rather than just compare the one figure of merit.

Also the fT of a PNP is usually lower than it's NPN compliment.

For example the Sanken 2SC2922 has a quoted fT of 60 MHz @ Ic=2A but at Ic=20 mA fT=20MHz
 
EW installed a set of these transistors in a pair of my L-07MII. IMHO it is worth doing. To me it changed the definition and the complextion of the music output. All for the better. It is not dramatic but very very noticeable. It you have a set of L-07MIIs it will bring them to spec. and carry a big surprise, just my opinion. As always EW does a superior job on these kind a things. :music:
 
Hypothetical...I have two G-9700's. One has most of the original Sanken 2607/1116 outputs either shorted or open and the other has a full set of originals in operational condition. I'm keeping one and selling the other. Which unit do I put the new ST Micro outputs in? The keeper or the one I'm selling?

I have had nothing but good experiences with modern replacement outputs as recommended here by the experts, all the gear works well and sounds excellent. But some believe that nothing but the original outputs will equal original sound. I believe that nothing is as reliable as a new device assuming it is from a quality vendor like Digikey etc.

Opinions please....:scratch2:
 
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Do the one you are selling, (i.e. the broken one) but if you think there might be something different about them when repaired - do a listening test - see if you can tell them one from the other? (I doubt you will be able to tell them apart)

Also
It depends who you sell it to, you will, in all probability sell it to someone who wants to know and cares what outputs/work has been done to it. For the purist, the 'original' one will hold the most value - despite the suggestion that it just might not be as reliable (output transistor wise) in the long term. (I am on the fence on this one)

Just my 3 ha'pence worth.
 
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The fT spec on the 2SA745 is 15MHz. The OnSemi MJ21193 replacement is 4MHz. These STMicro parts are 25MHz, should I go with the ST because it specs better? Or is oscillation a danger whenever you go over fT spec?

(Sansui BA-2000)
 
This is EW's list, deviate from it at your peril...

Sansui BA-F1
Sansui AU-919
Sansui G-9700
Kenwood L-07MII
Kenwood L-05M
Kenwood KR-9050

EchoWars said:
I'd not recommend using these in anything except those amps that are designed to use ultra-fast output devices. For these more common amps, On-Semi is likely to carry good substitutions for the foreseeable future...such as the MJ21193/94/95/96, the 140V 20A MJ15003/04, and the MJ15024/25. Much safer.
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Just my 3 ha'pence worth
 
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I sent a message to Digikey, asking why the part is in the catalog, but shows up as MIA on the web (even parts that Digikey doesn't carry at all, or parts that have been discontinued for years will show up in a search of their inventory). I figured this HAD to be some sort of web glitch. Anyway, this is the response I got:
Good Evening,

I looked both on the internet and in my system that I am working on, and you're right. The part 497-6953-ND doesn't show up on the internet. This could be a simple glitch with the system, we could be updating it and it is messing with the website (since we are constantly changing things and updating them for more efficient use), or it could be something that I simply cannot explain.

The good news is that, yes, I do show that we carry both of the parts and that they are both in stock. I will pass on the information that the one part is not showing up on the internet and see if they can look into it and fix that.

Please let me know if you need any more information in regards to these parts, if not I hope that I did answer your question to your needs.

If you have any questions feel free to contact us in any way you feel comfortable.

Thank you,
Megan

Have a great day,
Megan ******
Digi-Key Corporation
Inbound Sales Representative
1-800-344-4539 ext ****
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So they still carry it, but there's an issue with web ordering for this part right now. Hopefully it'll be remedied soon, but in the meantime you could order them on the phone.
 
From what I've read in the past few months, the metal cased TO-3 version is being discontinued. :tears:
 
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