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:
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?
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
An externally hosted image should be here but it was not working when we last tested it.
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?
An externally hosted image should be here but it was not working when we last tested it.
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
Hmmm . . . as I think of it more, I believe it's Q1 that does the bias adjustment, following temp. 
D1 and D2 are indeed thermal sense diodes. The diodes on the ThermalTrak devices should work for this.
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).
Yeah, i would ask the same question - what is the goal here? Are you learning stuff, or after replacing a blown module?
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.
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:
An externally hosted image should be here but it was not working when we last tested it.
Then, I'd like to try and incorporate several ideas borrowed from Doug Self's "Blameless" design:
An externally hosted image should be here but it was not working when we last tested it.
This should be a good project to experiment, and learn, from. With multiple side benefits if it all works as I hope.
Artie
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?
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. 🙂
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. 🙂
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.
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.
I saw your schematic post on another thread. Looking from the compensation schemes, this amp has been very hard to stabilize (I guess the module has been broken down due to oscillation?).
Many old integrated amps have good amp section, terrible IC-based preamp section and do not have pre-out. Yeah, you can add "amp in" and drive it with external preamp.
Thats definitely one of the "mods" I'm going to do to this unit - pre-out/main-in jacks. My primary reason for doing that is so I can gauge the value of other mods as I go. I can A/B my mod against known preamps and amps that I already own. For example, I'll test the first STK module clone using my Proton preamp. And I can test the Pioneers preamp mods using the amp section my Sony TA-5650 VFET amp. (An old standard for me.)
Overall, I think this is going to be a fun project.
Overall, I think this is going to be a fun project.
This is a great project. STK-0050 is a module I come across all the time in my vintage travels, and every once in a while, it is blown. Knowing how to make one would surely help a lot of people.
The STK-0050II is a drop-in replacement with 20dB less distortion and built in Baker Clamp diodes. They sell for $8.86 (including shipping) on eBay.
This will also replace the lower rated and quasi modules, all with 52mm hole spacing.
This will also replace the lower rated and quasi modules, all with 52mm hole spacing.
Well, I just went ahead and replaced with STK0050-II. I just ensured the central 4 pins are not soldered. And the receiver is back in action.
I think I can conclude they are compatible...🙂
Dear:
Floated this topic, because I would be very interested to find a good quality substitute for STK 0050, I have a SX 780 currently operating but replacements of dubious quality and would like to find a definitive solution.
Artie, have you been able to finish and try this project?
Best regards
Mariano
Hi Mariano! Un saludo! Alguna novedad sobre la versión con componentes individuales para el STK0050? Any news regarding the STK 0050 module with discrete components? I'd like to try Artie's idea but have no idea of resistor values R1, R2, R3= R4 and R5.
Thanks in advance, un abrazo y gracias!
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