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PostPosted: 19 Feb 2016, 17:13 
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I cannot remember why I got the incredible idiotic idea to start this project. I guess some small influences from here and there sort of inspired me to get on with it. There were some discussions with another member of the forum about the transistors and some checking on the web the main component, the transistor seemed to be available. A bigger concern was the resistors. How to fins a 15 Ohm/50W resistor?!

To make a long story short, I ordered transistors "real Renesa" on eBay and ended up with crap, but I had understood that would be the case as I waited for the shipment. I also ordered some from a reliable source in Germany and they did work. As I need a few components for another project I will propably be back for some more, just in case ...

OK, back to the project. With all components in place (minus the proposed choke) I could finally start trying the proposed design. Mounted (a working) transistor on a heatsink, Passive components soldered on a small breadboards (the Chinese cannot fake those ...).
I got a special made transformer (2x18V) cheaply from England (eBay), have som 10.000uF and rectifiers suitable for the job, but no appropriate chassis.

A quick setup gave good results immediately. There were no instructions how to set up the amplifier, but I guessed setting the pot in mid position would be fine for a start. Double and triple checked all connections; I managed to kill four Russian power tubes in ten minutes once, so I have learned the lesson, and learned it good.

Before showing to blurry photos taken by my semi-pro mirrorless Canon camera, a few notes. All components are according to original drawings, apart from the plastic caps across the output electrolytics. I could only dig up a pair of 2,2u, and I used 47uF caps on the bias voltage. The PSU isn't assembled as I feel I need a box to put everything in so I powered the amp by my PSU.

Here comes the pictures, as the project goes on I will send more details.

This is the experimental setup. Input grounded, PSU running at approx 24V and DMM across drain and source. All lokks perefctly well.
Attachment:
2SK1059_02.jpg


Now I have attached a potentiometer to the input, connected a speaker and my iPod and play some good music. Not that very loud but that may depend on the speakers.
Attachment:
2SK1059_01.jpg


I also want to thank KrammeAcoustics for good advices and help along the road, that was, actually really short. I have never managed to go from project start to a working device this quick. :eek:


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PostPosted: 19 Feb 2016, 19:14 
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Looks a little like my ZCA. Got a schematic?

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 20 Feb 2016, 03:22 
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Yepp! Here it is :idea: http://diyaudioprojects.com/Solid/ZCA/ZCA.htm

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PostPosted: 20 Feb 2016, 04:27 
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Soundbrigade wrote:


The guy that came up with that idea was pretty darn smart.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 20 Feb 2016, 04:44 
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Will get #2 up and running an solve the housing problem. The problem is when you have the amp parts AND off-the-shelf heatsink.; it's hard to find a chassis that suits your needs. But I have decided to try to adopt the tube-like way of mounting stuff.


A friend of mine who teached tech-stuff at a high school had his students to build a one-transistor amp. Guess he used a darlington like BDX33 or 34. Many students meant that their simple stuff sounded much better than their parents 5.1 home theatre systems from Bose.

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PostPosted: 20 Feb 2016, 07:21 
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Got an odd question in a Swedish forum - What's the purpose of the resistor ....??? :alien: How the heck would I know. :confused:

Here are some more shots of the little green board, transformer and heatsink. The heatsink isn't the biggest in the world but has large fins and should be able to keep the transistor pretty cool.

Attachment:
2SK1059_03.jpg


Attachment:
2SK1059_04.jpg


Attachment:
2SK1059_05.jpg


Attachment:
2SK1059_06.jpg


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PostPosted: 20 Feb 2016, 10:19 
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Someone who had tried something similar suggested to add another FET in a FETlington arrangement to increase gain. Sounded like a cute idea but why not combine the best of two worlds ...

Image

The 6S31B is a subminiature tube that will fit in any case. Ordered a pair of them from Russia. have to come with an idea of fixing 110V.

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PostPosted: 20 Feb 2016, 18:00 
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I came up with the MCA which is a Darlington pair - JFET and 2N3055. It sounded better than the ZCA.

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 20 Feb 2016, 18:01 
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Do you have an image of the tube?

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Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
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PostPosted: 21 Feb 2016, 01:16 
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http://www.sovtube.com/545-1168-thickbox/6s31b-r.jpg

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