I found these on Amazon.



Lightweights but will be here this week. I might even swap out the Edcors in my Zkit1 build when the point to point is up and running. Then put the 5 watters in the Zkit1 and power a set of Tiny Radials in the office.

Now off to the local tin shop to find some 16 gauge steel for the chassis. Looks like February is going to be busy around here!

John

Yes OPT is the final link in an amp like the amp is to the system. Steve definitely over built these amps and chose to forgo getting every once of power from the parts. The amps purr like a kitten and convey the same comfort as petting one.

I entertained the thought of getting Transcendar to wind a couple out of silver. Then looking at the latest prices of 5n silver wire quickly change that route. Prices have went up 50 percent in a year.

Thanks for your input on the different OPTs you tried Bobc. I figured a 5 watter should do well as long as it is not pushed too hard. I usally listen around the 12 oclock position.

John

The base has been assembled, glued, and clamped. The base will serve two purposes. One, as a platform to assemble the circuits. Two, as a finished base for the completed amp.

John

Yesterday was layout day. Today drilling, cutting, grinding, and finishing the steel plate. Tommorow the parts will be mounted and a plan of attack created.


John

Things are going to get tight as can be seen by the preview pic above.




Got this far. Will definitely have to power her up before a 25th anniversary mod is applied!

John

Curious why you turned the input tube?

Looks good.

I use a set of old kiosk 8 ohm speakers(info commercial tvs used in retail stores the turn of this century) to test equipment. Last night there was a hum present that was mostly fixed by some wire and capacitor adjustment. This morning the phone was plugged in and all seemed good. Considering the power output of the phone and small 15 watt speakers volume was low. Took her into the Chariot this afternoon and was instantly amazed at the increase of soundstage. Almost overwhelming. Everything seem to be good, but after 20 minutes or so things started going south. Some distortion was starting on the right then the left further increasing to the point I jumped up and switched it off. Took her back in the shop to find everything was OK. No burnt resistors, visible shorts, solder joints look fine. Hmmmm! Hooked up the phone/speakers again and all sounded fine. Hook it back up to the Crystals and same distortion was present. Tried different tubes. No change. Turned the CSP2 volume down low and all sounded good again. By now it is starting to hit me that the transformers are not up to the task when the Crystals are yanking on SE84. So, I hooked up my Pyramid HT speakers and now the room is full of distortion free music. But sadly not sounding like the ZKIT/Crystals.
Well the lightweight transformers did the intended job of confirming the operation of the clone. The case can be finished. Be best to wait until I aquire some new trannies before installing the anniversary mods. Be nice if some UFOs slid into the mail box . In reality, this will give me some time to study up on laminated trannies and possibly build my own.

John

Hey, thought I'd share my version. I was messing around and driving my B&W 702 with the clone. the watts there are are very sweet, and the amp deals well with the complex impedance. Windows aren't rattling, but ~85db peak.

Impressive metal and wood work!

I had the plate laser cut and had a friend help with the frame from repurposed picture frame.

I eliminated the 3.3uf divider network on the preamp power, and used 2x56k resistors. Also 47uf in the power supply. 6.5K custom transcendar opt.

Yes, very nice Bob. I like the reclaimed picture frame base. I was thinking of a stainless plate but decided against it because it is very hard to drill. Laser cut is the way to go. Kind of wish my was wider but keeping to Decware size will fit into the scheme of things around here.

Is Transcendar still in business? I called but just get a number disconnected message. I see Edcor orders are pushed forward into June. Might just swap out trannies and keep looking.
I put in the Miflex oil coupling caps and the amp sounds pretty damn good right off the bat. Bass is a little flabby highs are crisp.



John

Super nice, John!

Too bad those OPTs didn't work out.  I'm thinking I'll have to get all my ducks in a row and order a couple of handfuls of Edcors for all the projects I'm planning.  Sure, I'll have to wait at first, but then I'll already have the rest on hand.

Do you know if the Hazen mod has any ill effects on tubes with an internal connection between supressor and cathode (EL84, 6P14P)?

I've ordered the parts for the 100R/330R conversion.  It will be interesting to hear the differences.

I'm looking forward to hearing more about your build!

One more note to share. There was always a slight hum in the zkit. You know, hum that can be heard until music starts playing. Removing the Edcor covers made that hum completely go away! I really think that steel screws running thru the laminations is the reason. Not sure why but will ponder on it.

Thanks for the kind words Bobc, Lin, and Rex.

John

One of these days I am going to keep a written log of what is done during a project one of these days....

Changing the cathode resister to 150 ohm instantly increased volume and weight so much so that lead 🎸 riffs are utterly amazing!

One of these days...one of these days

Thanks

John

So you changed your grids from 1k to 150r and really like the change?
My zen is in my office pushing a pair of tiny radials, so I don't sling solder on it much anymore.
It seems plenty loud now as it is.
I may consider it when I do the anniversary upgrades.

[size=20][/size]This morning the anniversary mods were added.


The case will be about 2 3/4" high when finished. About a 1/4" higher then the rest of my Decware equipment.



I have but 5 hours with anniversary mods 10 total since the amp came to life. It sounds very good and will get better with time. Tomorrow I will finish the cabinet.

John

bobc,

But now to be fair to pentode you need to put in another switch for some type of feedback (Schade?).

Got her done! 12 hours and the music is sounding new, different, wider, deeper, blacker, and detailed. Still a bit of strain in the high end, bass not as detailed as I became custom to with the Zkit. It will all come around in time. Guess all I have to do is play music! Yeah right, next up isolation platform reorganization which will involve shoptime. Then some of Steve's TRs for the office.




John

Thanks Geno! Happy to hear it looks good on the PC. I used the phone camera. Almost got the SLR out.

Bobc I did not check voltages on the outputs. Did a B+ check and it was under 300v with the 100 ohm resistor. I might add front inputs for the purist approach.
About the transformer, bolts thru the laminations were rubbing the first lamination that pinched the thread because it was not lined up correctly. When reinserting the bolts, I may have shorted a few more laminations which caused quick saturation with music playing. In short the Edcors sounded like the 5 watters. I just pulled the bolts and all is well with a no hum bonus!

John

I had a plan for this morning of rearranging the bookshelf in the office putting a few things away to make room for the Zkit. Woke up at 1:30 am...yes just about last call at the local taverns...and had SE84 on my mind. I went downstairs without even starting the morning coffee pot. Turned on the clone and listened 5 straight hours! Spent last evening doing the same 5 hour shift. Why? Well the system sounds different with the clone. There is more detail in the midrange for sure, more throat sounds from singers, sharp notes off of string instruments, sharp piecing notes coming from throats of horns, drums are room filling, and on and on. But, there was this nagging thing that most likely got me out of bed and down the steps without blinking-a-eye. Vocals were not right. There seem to be a nagging sibilance from time to time. Not the Sssssss associated with a hot mike but more like the type of distortion one would hear on worn vinyl. The hiss of splutter. It did not occur all the time but it did occur often enough to get my attention. It was still there this morning. What could be causing this I wondered. The vocals were always clear on the Zkit.

So the more it happened the more I dwelled on it thinking did the Hazen mod caps get too much heat? After all this is the second go around for the .01uf caps use coming from the Zkit after the anniversary couple caps upgrade. The leads are short after being used on the circuit board and it took some finagling to get it soldered up. Nope, probably not I thought. Maybe the input 1K grid resistor added for some reason. I do not know why but it was put in! A volume control was not needed because the CSP2+ will do that work. Could it be that foot long low noise cable I repurpose from the ZP3 that someone left in the case after moving the inputs to the front of the chassis. Very possibly! I also notice the clone seemed kind of veiled, on the dim side, missing vibrancy which I was blaming on breaking in issues. It has been 22 hours now and the bass was starting to tighten a bit and high end was getting less edgy. The sibilance was not letting up and the veil was ever present. What could be going on here?

The ah-ha moment finally came after a short sleep coffee less morning. It would be the fix for sure. It had too be. First that 1K grid resistor had to go. It is not needed and must be adding its signature to the music. Second, I have 4' of 5n 22 gauge silver in the coiffeurs left over from the interconnects built last spring. The silver wire can replace the low noise 2 conductor copper shielded cable. I got a plan!

At this point feeling the pain of not eating breakfast, sleep deprivation, and no coffee fix, I took care of these issues before finding all that would be needed to get this clone singing a tune. Feeling somewhat rejuvenated I set out to assemble the silver cable with some salvaged copper shielding, teflon tubing, and clear shrink tubing. The clone has a silver plated copper ground buss from the mains ground all the way up to the input tube area so an addition ground wire was not needed in the cable. The silver wire was threaded thru teflon tubing twice and the resulting two wire assemblies were threaded thru the copper braded shield. The cable was then inserted into the shrink tubing. The 1k resistors were removed with one end of the new cable soldered to the input tube socket pins. The shield was cut back about an inch and sealed in the shrink tubing. The other end was connected to the input jacks with the braiding attached to the inputs ground. Shrink tubing will be heated and job complete.



More to come because it did not go well for me but great for the clone.
Hint, both pics show obvious errors. Can you find them?


John

PS
Thanks Rex!
 

Wiring is easy.

Finding something looks good and is "right" is harder. in the MA range. These are cheap Chinese eBay that work. Ideally I wanted something higher end.

You can switch them in / out, or wire in with the cathode resistor.

These are 100MA meters that have 2 ohm resistor across terminals. So my cathode value is actually 152 as they are wired in line. The meters have a coil too, which in theory may affect sound too. I listened both ways, the meters did not affect sound to my ears. Wire meter between resistor to ground, and the bypass cap directly to ground.

You can switch in a 100mv meter across a 1ohm resistor.. In this case mv=ma. Cathode bias is 151 in this case. Wire this same way, at the "bottom" of the resistor. You can also do this with "any" meter, ohms law and math, by shunting a resistor across the meter to change its range. Check out the 25th thread for some pics, you can see this amp has a shunt resistor across the meter.

They are very useful. I know immediately if I bought a bad output tube, or something funky in the input stage tube. Meter indirectly reflects B+ value as a higher B+ (say a solid state rectifier, line voltage or whatever) results in higher bias current.

NOTE: ALSO despite what I typed to illustrate bias resistor value if you want to do separate bias and meters for each output type use a 300R resistor (2x150) bypassed with 1000uf. You can do this with or without a meter if you think that this is "better" (some say it is).

I just finished up a 300B amp, and I used a switch, cut the internal resistor and switched the meter across some 2ohm power resistors I put in series with the "main" cathode resistor. Middle is off, left - left tube etc. So in both cases my cathode bias is a few ohms off (call it tolerance).

You can see the amp clip when the meters move. These meters  dont "dance" just sag a little to confirm what your ears hear.

There are some very high cost "audio" MA meter you can use too. Yamamoto makes one I think. Was looking at Simpson meters too, but many of these meter companies seem to be OEM oriented. My cheap meters work, a high end jeweled movement with ballistics would satisfy my soul, but I dont think would affect function or sound one way or another.

I hope all this made sense.

Good luck.

Wow, those are nice!  Any idea where to get them or how much they cost?  The ZMA meters are the standard all plastic cheapo kind seen everywhere.  Assuming the Yamamoto don't cost more than the amp, they'd be a great upgrade.  

Thanks.  I emailed for a quote but then I did some measuring of my current meters and they are bigger.  So, no go.

Gmidstokke,

I've been blown away with mine at times with the right material. My biggest fear is getting totally wrecked after visiting Decware in Peoria someday!

John