DIY Decware ZKIT thread

bjlefebvre

Super Member
Starting to prep for a build of the Decware ZKIT, a DIY version of their SE840 amp. Still waiting to hear back from the company whether they’ll sell their UFO output transformers to me to use in building the kit. If that doesn’t pan out, will use Edcor transformers all around. One thing I’m wondering and maybe the crowd can educate me on - the output impedance on the OPTs. Decware’s parts list suggests 6 ohms. My Zu speakers are rated at 12 ohms. Is it better that I choose a 12-ohm output impedance on the transformers? Or just leave well enough alone? And the Edcors are advertising an 8-week lead time before delivery. Yikes.

Otherwise, some parts upgrades I’m considering: a pair of Jupiter cryo beeswax caps for the signal paths and Cardas speaker terminals. Still mulling whether to use two Canadian military spec single- potentiometers - one for each channel - as suggested by @jdsalinger . I personally like dual volume pots, but still going back and forth on it.

Box: Brazilian cherry wood. Top plate: Might order from Landfall, as I did with my Tavish phono build.

I’ll update this thread with pics and maybe any dos/do nots I may run across. And probably will have plenty of pesky questions for @jdsalinger and @13stoploss as I continue. I’m now decently versed in the “how” part of DIY - soldering, sawing , etc. Now I’m dipping my toes into the “why” part of things.
 
Last edited:
You can run those speakers, but the output will be less. I've run 8 ohm speakers connected to 4 ohm output tranys on old Magnavox amps pulled from consoles. They sounded good. But the output was lower by about half.
 
Ok. Edcor offers the same transformers with output impedance of 8 ohms and 16 ohms. Maybe I'll go for the 8 ohms....
 
Ok, so Decware won't sell the UFO transformers. Instead, they said they could supply their in-house EM0493 OPT. Would be twice the price as the Edcors. Have to see if there' any info out there to compare the two.
 
edcor trafos always take a long time:)
i built a zkit; would do a lot of things differently now. i would probably not include the volume pot, eg. i did upgrade the caps; will look to see what i used. sounds really nice but it has a pesky left channel hum i need to tackle... the russian tubes they recommend sound really nice!
 
Wonder if the Decware transformers would be any kind of an improvement from the Edcors. Any thoughts on the secondary impedance, given I'll be driving 12-ohm speakers?
 
12 ohm speakers should be easier to drive than 8 or 6 ohm speakers. problem is when you go the other way: trying to run 4 ohm speakers on 8 ohm taps, etc.
 
For future reference, the Decware EM0493 transformers are for 8 or 16 ohm speakers and have a 3300 ohm primary.
 
I won't be able to help you with Why. Except that I went with monoblocks because my speakers are 6ohm. Upgrading parts for one stereo amp should be great with your 12ohm ZUs.

Still need to reply to your email... :whip:
 
Ordered the Edcors, and decided to go with Audyn True Copper caps in the signal path. I read some stuff posted by online folks who rate this kind of thing, seems the Audyn sound quality is very good for hi-fi, maybe not as great as the Jupiters but pretty damn good for a lot less money. Now it's the waiting game for those transformers.

:boring:
 
Last edited:
Lesson in patience. While waiting for the transformers and other parts, I bought some wood and took it with me on a family trip to visit my folks in Michigan. My dad has a small wood working shop - power mitre saw, router and a table saw - so I thought I'd cut the wood using the measurements for the Hammond aluminum top plate I ordered. Cuts came out nice, used a 45-degree bevel cut for the corners and rounded the top and bottom edges with the router. Stained the wood and glued in some runners to screw the top plate into. I knew it was stupid to make the cuts before the top plate arrived, but I figured if the aluminum were cut to spec, I'd be safe and have the use of a bunch of power tools I don't have at home.

Well, the top plate was delivered while we were away. As you can see, I got an extra 1/4 inch on the box width. So now the question is whether to live with two 1/8" grooves along the top edge, order a new top plate from Landfall measured to fit the box, or start over. The first choice looks unprofessional, either of the second choices puts me out another twenty bucks or so.

The aluminum plate came with a white adhesive protective sheet. Using that to play around with possible layouts....

IMG_20180825_122932.jpg IMG_20180826_193322.jpg PSX_20180826_194030.jpg IMG_20180826_193335.jpg
 
Last edited:
Mouser was nice enough to refund me for the aluminum plate without my having to ship it out. Ordered a new top plate from Landfall and received it - so that's a total wash money-wise. That was nice. Landfall top plate fits like a glove, and I'll use the Mouser plate for the bottom. If there's enough room, I might position the board at a 45-degree angle so the tubes poke out of the top in V formation.

Cut out holes for IEC socket and on/off rocker switch for the back. Gotta touch up two holes I mistakenly started drilling (don't ask - I was thinking of putting the RCA jacks in there, then realized at 3/8" inch wood thickness, ain't no RCA jacks going to be long enough) - a little wood filler and some future staining should take the worst out of it.

IMG_20180902_185017.jpg IMG_20180902_184906.jpg

Edcor alerted me that the transformers are on the way. Now I'm just waiting for an attenuator from Taiwan and a trio of tube sockets made from somewhere behind the former Iron Curtain.

I'm also mulling whether/how to bypass the attenuator. A guy on the Decware forum added a second pair of inputs that were wired to bypass it. There has to be a way to do this that would just use one (or I guess even two) input that, with a flip of the switch, would bypass the attenuator, no? Like, a DPDT switch, where one output goes the attenuator and the other bypasses it?
 
Last edited:
Eddies are here. Did a quick fit yesterday. This box is going to be crowded....
One possible problem - I cut the holes in the top plate for everything. But my measurements were a teeny bit off for one of the speaker jacks. The underside of the jack brushes up slightly against one of the output transformer's housing (I plan on bolting the OPTs to the underside of the plate). It won't be a wiring problem, but if the jack's screw-nut is touching the OPT even slightly, any chance for hum or other SQ problems?
IMG_20180910_212600.jpg IMG_20180910_212532.jpg
 
Bought a new top plate and some silver-coated copper 24awg wire. Finally got a few days where I could work on this for a couple of hours. Everything is installed and wired up (well, still gotta screw that one ground lug in and place a sticker or something over those two wood-filler goof holes on the back. Might sand the box edges a little, too, but sometimes I kinda like slightly rough edges, and I figure the provide "free" venting). Now just have to turn it on and hope it doesn't explode or have wicked ground hum. That'll be tomorrow.
Two inputs - one goes through the attenuator, one bypasses it (or that's the plan, anyway). It's kind of a PCB/ P2P hybrid. More the former than latter obviously, but had to do quite a few workarounds to add the a hardware I wanted in the layout I wanted.
Still trying to decide whether I like the chicken-head volume knob or aluminum circle better. Leaning toward the latter.

IMG_20181020_212207.jpg IMG_20181020_212234.jpg IMG_20181020_212241.jpg IMG_20181020_212350.jpg IMG_20181020_212303.jpg
 
Wow such a timely thread for me as I am getting the parts together to build the zkit1 myself. I wanted to take my first dabble into tubes to run the high frequency portion of my biamped jbl L200's.

The plan is to build one unit and run it stereo for the >1200 hz portion. If I like the sound i would probably build a second and make them monoblock.

Will look forward to the advice and progress! :lurk:
 
Back
Top Bottom