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New ZKIT 230V build (Read 2589 times)
holg
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New ZKIT 230V build
05/05/23 at 21:27:26
 
Hi everyone,

after months of learning about tube amps, studying the ZKIT-1 SE84DIY circuit (rev 10-2021), going through parts lists, suppliers, etc. etc. I'm finally at a point where I have a physical point-to-point layout that could actually work.

Here is my sketch in case anyone is interested. It's not a super accurate technical drawing, but very close in terms of how big my components would be, where they would be and how they would be connected with each other.




I upgraded some parts, but didn't change the schematic, other than
- adding an input selector switch
- connecting a LED pilot light across the 6.3VAC with a 1kOhm resistor in line
- adding a thermistor across one line of the power switch
- adding a 2nd fuse for the other line in case polarity gets switched by plugging the power plug in the other way round


Other things to note:
- after much consideration and no clear answers I decided to use GXSE10-8-8 as output transformers instead of the GXSE10-6-8 (short answer: I'll only ever use this with 8 Ohm speakers)
- the ground buss is yellow in the drawing, connected to chassis at only one point close to the IEC
- the input signal cables are all shielded and shield is connected at the other end of the buss, at the same point as ground from the potentiometer


I'm still waiting for some parts, then I'll start to prepare the chassis and go through this layout mentally a little more to see if I can find ways to improve.

Will keep you updated and if you have any questions please be my guest!
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holg
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Re: New ZKIT 230V build
Reply #1 - 07/02/23 at 23:10:30
 
Moving along with the build rather slowly, as expected, but no major surprises so far. I made the chassis, painted it, installed most of the hardware and am now almost done wiring up the power supply. Pilot light is already working, which keeps me motivated Smiley




Here’s the chassis progress (after painting):


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holg
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Re: New ZKIT 230V build
Reply #2 - 07/10/23 at 21:18:33
 
Finished wiring up everything except for the inputs (to input selector - to pot - to tube).

Next step after wiring everything up is double checking and doing measurements.

I am feeling pretty uneasy about doing the voltage measurements described in the ZKIT handbooks without speakers connected, I quote:

Quote:
Before hooking the amplifier up to a pair of speakers, and before hooking up the inputs, turn the amp on, volume all the way down. Let it warm up. Check the following DC voltages at the following locations:


I always thought a tube amp like this needs the load of the speakers connected to not risk damaging the electronics? Well, maybe one of you knows more, maybe I'll just find out.

Here's the current state:

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4krow
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Re: New ZKIT 230V build
Reply #3 - 07/11/23 at 03:23:19
 
Man, I would want to see you go that far with parts and labor just to find out that the will be destroyed without speakers connected. Not all amps are that way, but this is not the best way to find out.
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holg
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Re: New ZKIT 230V build
Reply #4 - 07/11/23 at 12:28:39
 
Thank you for taking the time – you’re absolutely right, better safe than sorry it is!
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dank
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Re: New ZKIT 230V build
Reply #5 - 07/11/23 at 20:45:26
 
1)  The Zkit1 can run w/o speakers, no problem.

2)  It is not advised to fuse the neutral unless "the protection circuit ensures both hot and neutral wires are interrupted at the same time in the event of an over current".  I think the fear is an over current blows the "N" fuse first, there by protecting the "H" fuse, and you are left with a hot (dangerous) amplifier.

Dan
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holg
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Re: New ZKIT 230V build
Reply #6 - 07/11/23 at 23:15:41
 
@dank

As for 2) … and there I thought I was making it extra-safe by ensuring the hot side fuse blows no matter which orientation you plug the power plug in the socket – hence the DPDT and fuse before it on both lines.
So what’s the solution? Make sure which line in my socket is neutral and which is not and also make sure to plug the amp in in the right orientation?
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holg
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Re: New ZKIT 230V build
Reply #7 - 09/03/23 at 17:09:16
 
I finished building the amp! It sounds really good with my Pioneer HPM-60 and volume certainly isn’t a problem for me.
The voltages measured a little out of spec, and the potentiometer/volume control is too steep (I have to turn it a tiny bit for a huge increase in volume, and it maxes out at maybe 20-25% turning of the knob).

Otherwise… I got some listening to do  ::)




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Lon
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Re: New ZKIT 230V build
Reply #8 - 09/03/23 at 17:24:03
 
Congrats! Very nice looking build!
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ArtMan
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Re: New ZKIT 230V build
Reply #9 - 09/03/23 at 19:25:32
 
That is one sweet looking homemade amp. As far as listening, I suspect you are having a great time right about now.
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holg
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Re: New ZKIT 230V build
Reply #10 - 09/04/23 at 08:16:36
 
Thank you guys! I’m already thinking about another one to use as “mono blocks” with this one. Not because I’m not satisfied with the output and sound of this one alone (I’m very impressed actually!), but because it was so much fun building it Smiley
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bhenriks
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Re: New ZKIT 230V build
Reply #11 - 09/16/23 at 21:03:46
 
Very sharp looking homemade amp, congrats!  Thanks for the layout drawing, very helpful.  Now go for the monoblocks!
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holg
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Re: New ZKIT 230V build
Reply #12 - 09/16/23 at 23:24:26
 
Thank you for the kind words!

As for the monoblocks… still trying to figure out a thing or two (see other thread), but once that’s cleared up I’ll build a preamp or another ZKIT1  [smiley=50.gif]
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