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Linn LK280 Decoupling the first stages from output stage

M

Marc Legare

Member
Hello
I'm new here. I recently acquired a LINN LK280 with Spark. I really like the sound I hear from this amp. I would like to upgrade the LK280. I thought decoupling the V+ and V- that goes from the output stage to the first stages. Did someone tried that with simple regulators ? Also I thought upgrading the rectifier diodes to MUR860 or Hexfred HFA08TB60. Some mentioned that the hexfreds works ok in tube gear but not with transistor gear. Any recommendations for this amp ? Thanks
 
I am sure there are both lm317 and lm337 in the circuit so perhaps they are regulators for the front end?
 
These regulators use pass transistors and they feed all the amp. The output stage and the front end. There's no decoupling between output stage and input stage.
 
It’s an interesting idea. If anyone’s got a faulty 280 for me to butcher/repair I’d be interested in messing.
 
You have to cut two PCB tracks that go between input- and output-stage. They run at the outer sides of the PCB from back to front. Then you can feed the frontend separately.
The regulated rails run at around 40-41 V. You can built a LM317/37 supply with provisions for the higher voltages. Commercially available are Burson regulators, they can make 3-pin regs up to 50V if you ask them. Neat little package, bit don‘t know about the quality.

I have a LK280 on the bench as well right know. They are really fun amps that are not expensive. I will convert two of them to something like a Mono-Spark. Thought about regulating the frontend separately as well. I use Qspeed LQA diodes, they seem to work.
 
Yes, that's easy to fit in a Spark LK280 because there's a lot of place left because the transformers are in the Spark. When you mention QSpeed LQA diodes seemed to work, can you describe me what it does to the sound ? Also is there a part number you used ?

The LK280 with the Spark are really special. In the Spark there's rectifiers and caps bank. V+ and V- goes to the amp but they are again rectified (???) + another cap bank before going to the regs. Why rectify again Dc V+ and V- . I really don't understand this way to do or the benefits it can do.
 
The second bank of rectification is redundant and a remnant of the unsparked 280. You could link them out.
 
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