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Old 5th July 2012, 04:16 PM   #1
Artie is offline Artie  United States
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Default DIY STK-0050 module.

I've been meaning to try this project for quite some time, and the STK-0050 is about as simple a schematic as they come:

Click the image to open in full size.

But I have a couple questions before I order parts:

1. Can 1N4148's be used for D1 and D2?

2. Are these the diodes that will adjust the bias relative to temp?

3. If the answer to #2 is "yes", would the diodes within the OnSemi ThermalTrak transistors work in that position?

Click the image to open in full size.

The 1st version I build will be as close as possible to an exact replica. I'll experiment with mods on future versions.

Thanks all;
Artie
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Old 6th July 2012, 12:38 AM   #2
Artie is offline Artie  United States
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Hmmm . . . as I think of it more, I believe it's Q1 that does the bias adjustment, following temp.
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Old 6th July 2012, 01:13 AM   #3
Artie is offline Artie  United States
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Ah, search is my friend. I've found several good threads that explain this clearly.
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Old 6th July 2012, 06:06 AM   #4
jaycee is offline jaycee  United Kingdom
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D1 and D2 are indeed thermal sense diodes. The diodes on the ThermalTrak devices should work for this.
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Old 6th July 2012, 11:52 AM   #5
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Artie View Post
1. Can 1N4148's be used for D1 and D2?

2. Are these the diodes that will adjust the bias relative to temp?

3. If the answer to #2 is "yes", would the diodes within the OnSemi ThermalTrak transistors work in that position?
I don't understand what you are trying to do. Are you trying to replace an STK module in an amp? I don't think so. Are you trying to make a module that you can use for general purpose?

Imo, this is very complicated as the relationship between diodes, Vbe transistor, output transistor (and even driver) is still "unknown". They will have the same temperature drift, that's the first known condition. For the rest, I don't understand why you have to be "attached" to that STK topology. I think it will be hard to calculate, and not so flexible. And especially when you use good parts (as the NJL) you want the best, i.e. unique configuration for the circuit (e.g. bias current).
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Old 6th July 2012, 02:50 PM   #6
jaycee is offline jaycee  United Kingdom
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Yeah, i would ask the same question - what is the goal here? Are you learning stuff, or after replacing a blown module?
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Old 6th July 2012, 02:58 PM   #7
Artie is offline Artie  United States
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Quote:
Originally Posted by jaycee View Post
D1 and D2 are indeed thermal sense diodes. The diodes on the ThermalTrak devices should work for this.
Cool. But I still need to read up more. I'm going to order Doug Self's book an amp design. Apparently, there's more than one way to skin-a-cat, so to speak.

Quote:
Originally Posted by Jay View Post
I don't understand what you are trying to do. Are you trying to replace an STK module in an amp?
That's exactly what I'm trying to do, but for several reasons:

1. I have an old, (and dear to me), Pioneer SX-780 with a blown module, that I'd like to "update" and bring back to life. (With some future mods to bring it in to the 21st century.)

2. This comes up on AudioKarma all the time. There's the question of whether or not aftermarket modules are fakes or not. It would be nice to just do a forum project and produce our own.

3. I've been wanting to build one of the amp projects that I keep seeing being talked about on this forum, but I've always had a hard time knowing where to start. I figured this could be a somewhat simple place to start.

Here's what I'm thinking now:

Click the image to open in full size.

Then, I'd like to try and incorporate several ideas borrowed from Doug Self's "Blameless" design:

Click the image to open in full size.

This should be a good project to experiment, and learn, from. With multiple side benefits if it all works as I hope.

Artie
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Old 6th July 2012, 03:04 PM   #8
jaycee is offline jaycee  United Kingdom
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That will work well. Just remember to mount Q1 on the heatsink with Q4 and Q5, and it should work OK. You MAY need to adjust compensation in the rest of the circuit. Do you have a schematic for the Pioneer?
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Old 6th July 2012, 03:35 PM   #9
Artie is offline Artie  United States
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Yeah Jaycee. I have the full service manual. Plus, I have pretty much all the test equipment I need as I work in a Navy cal lab. I plan on mounting all of those components on a single "wafer" so as to come as close as possible to a plug-'n-play module.

Later, after I get all this to work, I'm going to do some "upstream" mods to the Pioneer. It uses some outdated IC's for tone and pre-amp duty such as the old Toshiba TA7136P. But . . . one step at a time.

I'll definitely be counting on help from this forum, to make this all work.
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Old 6th July 2012, 05:54 PM   #10
jaycee is offline jaycee  United Kingdom
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Sweet. Found the service manual on Hifi Engine. The power amps are a very simple Lin circuit so not too critical. I'd probably say forget the ThermalTrak devices, a pair of something in TO3P/TO247 would do,

That opamp could be a problem - wierd SIP package and seems to run from 21v supplies. Modern opamps are 18V supplies at the most.

As for any of the amp projects, well, the hard part is the case and metalwork Making printed circuit boards is actually quite simple if you have a laser printer handy.
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