Is fairchild SS9014 a good LTP choice. ??

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ostripper

ostripper

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Joined 2008
Came across this good deal at Mouser... ss9014

My intent was to search/source an equivalent for the MPSA18 low noise input pair and be able to buy 100 at a price that would allow for a mistake. With 100, one can be assured to at least find several that are close matches. For 4$/100 , why not.

The device has almost the same NF as the mpsa (.9db) a Ft of over 200mhz , and a lower Cob of 2.7pF. I am all cascoded in my designs now so I can "play" with a lot of low voltage/ low noise devices. Would there be any attribute in the datasheet - http://www.fairchildsemi.com/ds/SS/SS9014.pdf
to disqualify this for my main input pair choice ??

thanks. OS
 
CBS240

CBS240

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Joined 2005
If you cascode why not use J-fets? If you must use BJTs, although there is a significant difference in price, why not use something like this? Guaranteed match every time.:D

I don't see anything particularly special with those devices other than under certain circumstances they may exhibit a lower noise. Max NF is 10dB with a fairly large Rs for the test, seems like a significant range in the datasheet.

The thing you will lack with the THAT transistors is current gain, but for an input stage this is not really a factor.
 
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ostripper

ostripper

Member
Joined 2008
CBS240 said:
If you cascode why not use J-fets? If you must use BJTs, although there is a significant difference in price, why not use something like this?

I don't see anything particularly special with those devices other than under certain circumstances they may exhibit a lower noise. Max NF is 10dB with a fairly large Rs for the test, seems like a significant range in the datasheet.

The thing you will lack with the THAT transistors is current gain, but for an input stage this is not really a factor.
Click to expand...

I bought some Jfet's ,too. And the smd's will likely be at least my next generation input stage. The SS's were just so cheap , would they not be any better than the ksa992/ksc1845's ??

"lab handouts" (your link) :D that's funny... I also bought some of the mpsa18's. Noise is my last imperfection on my amps , most of the other distortion mechanisms have been addressed. That "max / min" NF is suspicious , does that mean some will be ultra quiet and others can be noise SOURCES ??

OS
 
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ostripper

ostripper

Member
Joined 2008
Krisfr said:
ok

Thanks

I am about ready to make some PCB for a KO amp, That is a Keantoken-OStripper
Click to expand...

Kool , :cool:... when mouser gets to me next week , my "spree" will start , a lateral board, 2 "KO" type amps and 2 of the updated/cascoded "Carlo's DX ES" type amps. Some sort of "double blind" A/B "shootout". I will try both at first with the best SS9014's I can pick out of the 100. Good luck on your builds , we should be the first ones.. :D
OS
 
Krisfr

Krisfr

Member
Joined 2007
Yeah

I am behind you on the parts and I have got to hope that the shunt I used for the front end works too, but I can cut it out if it does not. I did four pair and a little more stuff. I had to assume that the front end shunts need a pre-regulator too.

Thanks
 
ostripper

ostripper

Member
Joined 2008
Krisfr said:
Yeah

I am behind you on the parts and I have got to hope that the shunt I used for the front end works too, but I can cut it out if it does not. I did four pair and a little more stuff. I had to assume that the front end shunts need a pre-regulator too.

Thanks
Click to expand...

I'm just sweating the details now , I've left all my designs "open ended" enough to allow for changes but still retain that pro look. These input pairs are just one of the "NEW" parts I ordered and I will try them all. I'm glad "Capt. Grogg" LOL :D
has actually used these 9014's as I will have one dang long tape of them.
The 9014's have a "mate" , the ss9015. This will make them good for my leach amp voltage board (LX) with its complimentary cascodes.
OS
 
CBS240

CBS240

Member
Joined 2005
ksa992/ksc1845 are not devices that I would choose for input transistors. If professional is what your after I do recommend the THAT devices, although I do not think they come in pairs, just quads. 4 matched NPN, THAT300; 4 matched PNP, THAT320; and matched comp pairs, THAT340 (2 matched NPN & @ 2 matched PNP)

I use these as the input devices in my latest amp model and they work great, but in the future I am looking to use ALD1105 matched Mosfet arrays. They happen to be quite a bit cheaper but have a voltage restriction of only 10 - 12V and operate with much less current, so they will require special circuit conditions.*

All of these devices are available through Mouser, that is where I order most of my components as well.
 
S

sng001

Member
Joined 2009
Tayda in Thailand

ostripper said:
I think SNG001 knows that one. I just searched and shared :happy2:.
OS
Click to expand...

Hi Krisfr,

Their website looks quite professional & I googled & could not find any negative reviews on Tayda. I checked their ebay store & they have 100% positive feedback out of 9600 transactions.

They do have a refund policy:
"All our products are brand new. We import 95% of our inventory direct from manufacturers. We provide manufacturer names, manufacturer part numbers and datasheets for all the products listed in our online store.
Buy with confidence. We sell all our products with 100% satisfaction guarantee, any damaged or malfunctioning product will be fully refunded including shipping costs without any hassle."

I need more 2S types (ECB pinout) SSTs, so I ordered $43 worth of parts & the shipping is only $5.40. They calculate the shipping by weight: approximately 1.3c per TO92 & 10c per TO3P device.

They shipped my order on the next business day & I have not yet received my order and they said that would take 7 to 12 days to ship to Australia.

BTW, I also bought some J162/K1058 & the price is very reasonable. I will build a proven design to test these L-mosFET as I have not listened to a L-mosFET amp before.


Cheers, Stanley
 
ostripper

ostripper

Member
Joined 2008
CBS240 said:
ksa992/ksc1845 are not devices that I would choose for input transistors. If professional is what your after I do recommend the THAT devices, although I do not think they come in pairs, just quads. 4 matched NPN, THAT300; 4 matched PNP, THAT320; and matched comp pairs, THAT340 (2 matched NPN & @ 2 matched PNP)

I use these as the input devices in my latest amp model and they work great, but in the future I am looking to use ALD1105 matched Mosfet arrays. They happen to be quite a bit cheaper but have a voltage restriction of only 10 - 12V and operate with much less current, so they will require special circuit conditions.*

All of these devices are available through Mouser, that is where I order most of my components as well.
Click to expand...

I do notice they (1845/992's) are not the quietest , good for CM's and cascodes , but the input pair is critical (scope tells all :) ) Can see room "garbage" and noise on the scope that can barely be heard on the speakers.
The noise as seen on the scope's nV range dropped to 1/4 with the MPSA18's , BTW... it was harder to match them little buggers (higher gain).. :eek:

I'm not ready just yet for SMD , a couple months down the road , different story. I will add the Thats to my documentation, they are contenders (smd wise).
OS
 
S

sng001

Member
Joined 2009
2SC1815/SA1015

Hi OS,

I bought a bunch of Toshiba 2SC1815 from Tayda:

2SC1815
Audio Frequency Voltage Amplifier Applications
Low Noise Amplifier Applications
High breakdown voltage, high current capability
VCEO = 50 V (min), IC = 150 mA (max)
Excellent linearity of hFE
hFE (2) = 100 (typ.) at VCE = 6 V, IC = 150 mA
hFE (IC = 0.1 mA)/hFE (IC = 2 mA) = 0.95 (typ.)
Low noise: NF = 0.2dB (typ.) (f = 1 kHz).
Complementary to 2SA1015

They look like good choice for low-noise input pairs, I may ask you to do a special VB layout for me to test out these transistors.

Cheers, Stanley
 
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