are there SMD replacements for k170 j74

[aspringv]

Hi all,

I thought I'd try my hand at building an (almost) all smd pass amp. Is there any sub for the jfet buffer front end jfets? I could drop a BJT diamond buffer in easily enough, but it made sense to ask first.

Edit - I'm thinking an F4 - so its a complimentary pair I need

Edit edit - I'm thinking this as i've an all smt project to build soon and I want to get some practice in!

Cheers!
A

 

[AndrewT]

lsk170 is available in sot23

The lsj74 is becoming available, so it too may appear in sot23

 

[rco3]

Linear Systems sells the LSJ74 in SOT-89-3, and the LSK170 in SOT-23-3.

 

[aspringv]

Thank you!

Is there anything a little more pedestrian and common? I ask as getting those guys down my way is likely to be problematic.

Thanks again!

 

[AuroraB]

K170 and J74 are pretty unique, albeit with a few siblings, which have also become hen's teeth......

LSJs and LSKs seems to be the only versions in current production...

 

[nigelwright7557]

I built a lateral mosfet mostly smd amplifier.
For the lateral mosfets I kept to heatsink mounted to get more power.
I use the ALF16n16 and ALF16p16.

 

[AuroraB]

BTW - are there still original 170/74s available, outside the Ebay scams ???
There used to be a member or two, but I fail to recall the names...

 

[Dennis Hui]

BTW - are there still original 170/74s available, outside the Ebay scams ???
There used to be a member or two, but I fail to recall the names...

I can think of Spencer and Alweit.

 

[aspringv]

Thanks again all - I asked about pedestrian alternatives as ...it's just a buffer! it seems quite the waste to use that sort of (these days) exotica just for its low noise, when in that application the high transconductance is somewhat moot.

 

[aspringv]

@nigel Thanks - I'll look those parts up. Cheers!

 

[jameshillj]

Try the Kuartlotron buffer (see the thread here) - uses readily available transistors and parts (from Mouser, or local RS online, etc.)

Still plenty of k170s around - can do a dcB1 buffer with/without the shunt reg

Building 'ordinary' buffers are pretty simple but getting a really 'good sounding buffer' (ie. no sound at all) to work properly isn't at all that easy and the complementary k170/j74 is one of the few simple ones, depending on the supplies

 

[aspringv]

Thanks @jameshillj - I've read through the K-buffer document before (bit over my head to be honest). I might just stick with a diamond buffer for now - it seems relatively well proven in this context.

Thanks all!

 

[AndrewT]

if you can get your Buffer to work with only Nchannel jFETs then you can use the readily available bf862.

The B1, DCB1, Calvin and D.Feucht Buffers are Nch jFET
Juma's Buffer may be Nch.

 

[WBS]

I can think of Spencer and Alweit.

Spencer is great!

Alweit's customer service leaves a lot to be desired. A number of the matched pairs that I ordered from Alweit became unmatched because of how poorly they were packaged for shipping. When I brought it to his attention the response was, "Sorry, I've heard that from other buyers as well."

 

[AuroraB]

Spencer who??? ( I found a lot of spencers here.... )

 

[Dennis Hui]

Spencer who??? ( I found a lot of spencers here.... )

diyAudio - View Profile: spencer

His site: FET Audio | Hi-End Audio Projects

Best way to contact him is through his email address on the contact
page of his site.

Cheers,
Dennis