1626 Clementine with Edcor Iron

[Zap]

I've been pondering a Darling amp build for quite a while now, and I'm starting to think its time to proceed forward.

I've had great luck using Edcor iron in the past, and I'd appreciate any comments on what works best in this situation. My KT-88/6L6/6550 based amp uses the Edcor CXSE, which have an incredible sound and excellent bass. Obviously, this would be major overkill on a Darling, at only 3/4 of a watt per channel.

I'm curious if anyone here has used the XSE / GXSE series OPTs, and especially if there is any commentary on any differences between the two in this application.

Finally, I've read the other thread but am a bit confused at the discussion about a recommended Edcor power transformer, as it appears the amp being built there is the "chubby" with higher powered tubes - so it wouldn't be an appropriate match.

I greatly appreciate any comments and suggestions from more experienced builders!

[Geek]

I think there will be a consensus among the Edcor fans that you won't be disappointed by a GXSE.

Just use a 15W core and you'll have no noticeable degredation on the bottom from a CSXE with Darling bias currents and power levels.

Someone correct me if I err....

Cheers!

[Zap]

Thanks for the follow up! I'll plan on going with the 15W GXSE series for the OPTs.

I just need some input on the Edcor Power transformer and I should be in good shape to start procuring for a build!

Also, I'm curious if there are templates posted anywhere for chassis cutout for the PCB.

[Shannon Parks]

Here's an FPE file zipped up. You'll want to verify the transformer dims for certainty.

Shannon

[Zap]

Thanks for the file! I just got schooled - had no idea what the file extension was, so after searching I found FrontPanelExpress, and was stoked to find out they actually had a Mac version of their software. Makes me wish I had the option when I built my first amp a while back - the pricing is quite reasonable. The enclosure was built for me and I installed the plate into it with the PCB, transformers, etc.

Once I was able to view the file I started having questions as to what all the cutouts were for! Are there pictures anywhere of a finished amp that uses this panel template? From what I can tell, everything is installed on the plate, with screw holes for a choke to hang off the bottom and the IEC, switches, and input jacks to sit behind the transformers.

I'm still debating which route to take, as I'm not really versed enough in woodworking to build a fancy enclosure, so I may resort to using the template to cutout a chassis. I'd definitely be curious to hear thoughts from others. I was contemplating this amp to be used in a smaller space and possibly sit on a wall shelf, with the set of speakers also mounted to the wall. Jury is still out there....might just mount the speakers on the walls and leave the amp on a piece of furniture for adjustments.

[Shannon Parks]

A Clementine builder emailed me that layout awhile back, so I'm not even certain which transformers it was laid out for. I usually print a 1:1 and tile pages as needed. I then tape it together and get out my machinist rulers (I have a 6" and 12"). It helps to visualize the size of the completed amp and I can double check tranny mounts and PCB holes, too. As far as CAD programs go, I think it is super intuitive (compared to your average 2D DXF or 3D Solidworks software).

On a 300B amp I'm working with now, I plan to get one of these: http://www.hammondmfg.com/HWCHAS.htm
You can use the supplied top plate as a bottom plate and get a top plate from FPE.

Shannon

[Zap]

That's a great idea on the Hammond Chassis - I was totally considering using one of those at some point since they look so nice. Didn't think about having the panel machined and just swapping the top to the bottom - excellent idea.

Before you go buy the chassis - if you weren't aware, DigiKey is selling them for $75 - quite a nice price break from the $100 or so everyone else is asking. I'm still trying to decide if this is a budget amp, and I should keep the price down OR if I should fancy things up a bit. I was already planning on probably using botique (Auricap XOs) coupling capacitors.

I can see things following the path of my last amp - it is hard for me to cut corners anywhere (within reason - my budget is still limited, so no super exotic capacitors or iron that cost 5x alone vs the cost of a complete yet basic amp), but at the same time it is impossible to argue with the resulting sound quality.

[Zap]

And the addiction begins again - I just started contemplating the possibilities.

Consider that my KT88/6L6GC/6550 amp has:
Auricaps
Stepped Attenuator
Light-up chrome switches
Triode / UL Mode Option
Cathode Feedback Option
Tube / SS rectifier option
Edcor CXSE OPTs
Big Supplementary Power Supply Motor Run Smoothing Cap

One has to ask the question - where DO you draw the line.

If I had more cash, I'd totally consider building two amps - a stocker with no upgraded parts, and a high-line amp with better caps, stepped attenuator, upgraded transformers etc. I'm curious just how much of a difference everything makes (OPTs obviously likely being the biggest).

[Zap]

OK - so the PCB has arrived and an order is placed with Mouser for all the small parts.

I was curious what choke(s) are recommended for the amp. I have seen 1 H mentioned somewhere, but 1.5 H is on the parts list. What brand/model is recommended? I see that Edcor is selling chokes now, but they look a bit spendy compared to others I've seen.

I'm hoping to order the transformers and chassis next, but want to piggyback the choke with one of those orders to save on shipping. I think that leaves the tube sockets and coupling caps, as far as parts go.

[Shannon Parks]

Zap, I was using the Hammond 156R and the Dynaclone C354 in most of my products for years, but have basically switched to the Triad C-24X 1H choke from Mouser after someone recommended it as a cheap sub. The nice thing is can can be ordered at the same time as the PCB parts, thus saving a few more bucks on shipping. I made the change a few months after the Clementine came out, so the manual refers to the 1.5H. All three parts work fine in the design, and the extra 0.5H doesn't make much difference (due to the CLCRC PS filter). All three have the same dims. One is made in Canada, one in China and one in the US. So choose whatever works best for you.

Shannon

[Zap]

Well, shoot - I guess I pulled the trigger on the Mouser order a bit quickly.

Edcor's choke is 1.5 H / 250 mA / 17 Ω DCR @ $26.13
Basically looks like the DCR is a bit less, but otherwise the specs are about the same.

Edcor also has a 1 H / 200 mA / 21 Ω DCR @ $18.92
Current is a bit less than the Triad, Same as the C354 and the Hammond

By the time I pay separate shipping, I can probably get an Edcor at the same price, or maybe slightly less, so I think I'm going to go that route. I have read some good things about the Edcor chokes anyhow, and then all the major components are US built.

So, power supply design was never something I've schooled myself on much - any thoughts on the choke being used? I presume since some of the other recommended chokes are spec'd at 200 mA, that the 1 H should work since other 1 H chokes have been found to be sufficient. My only other concern is the lowered DCR. Will this cause too much of a voltage increase in the circuit?

Thanks! :)

[Shannon Parks]

So, power supply design was never something I've schooled myself on much - any thoughts on the choke being used? I presume since some of the other recommended chokes are spec'd at 200 mA, that the 1 H should work since other 1 H chokes have been found to be sufficient. My only other concern is the lowered DCR. Will this cause too much of a voltage increase in the circuit?

Either of those Edcor will work fine. I'm just partial to smaller chokes I can place under the chassis as it seems I'm always running out of top plate space. As far as the lower DCR, it doesn't make much difference here. Say we have 40 ohms less DCR and are running 125mA. That means we have an extra 5V B+ which doesn't affect the operation but by a small percentage.

Shannon

[Zap]

OK, great! +/- 5V could easily be attributed to part tolerances, so I'm not too worried then. I'd like the choke underneath the chassis, anyway, as I am trying to make the amp not become too large and they don't have endbells to encase the wiring.

It looks like all the part choices are starting to come together. I should start looking at the cutout again now that I know which parts I'm going with.