3rd gen 50 Watt

[telentubes]

I've been collecting parts for a while and am slowly chipping away at a 50 Watt 3rd generation, ala the talbany layout.

I ordered several custom chassis after reading this thread... http://ddawgamps.com/Amp_Chassis.php. I opted to have 3 different custom sizes made, which priced out at $42 apiece, shipped. They are .090, with welded corners, and top plates, and are well built.

I did a full sized layout, then started drilling.
The PT is a Hammond 290EX. The choke is a Hammond 194B, and after much deliberation, I opted for a Prosonic OT (from Angela's).

The coax is stunning RG188 from Apex Junior. It's silver plated copper and the nicest stuff I've ever used (limited experience though).

I'll let the pics do most of the talking for now, although I do have a few questions, and will have more later, mostly regarding the relay system, which is still a little confusing.

[telentubes]

Here are a few more pics.

I had the PEC pots so decided to use them.

My first question is whether the orange drop cap on the "Jazz/Rock" switch (3rd on left from the input jack) has the outer foil connected in the proper direction?

Is the .005 cap on the bass pot OK, or should I use an orange drop, or a Mallory 150, or something else?

I left the PT leads full length until I know everything is working OK. Then I'll go back in and shorten the ones that are too long. It's kind of a rat's nest on that end for now but there's nothing worst than cutting a lead and wishing you hadn't.

[steve_p]

Nice. Definitely keep us updated on how this sounds.

I am definitely thinking about a 50W ODS, although I am not sure if I want to build a 2nd or 3rd gen. I guess i need to read about the differences a bit more.

[dcribbs1412]

Great looking build...nice job on cutting/drilling the chassis. I have used a few of those...(not custom sized)for the price cant be beat, I like them...faceplates?

Not sure about the orientation of the jazz/rock cap. my ears probably
couldn't tell...not sure if it matters a lot..easy enough to switch.
Bass pot cap I've only used OD in the few builds I've done. I use what I have on hand.
Again looks great...


Darin

[Structo]

Looking good!

According to the layout I have the .005uF cap on the bass pot is ceramic.

[dreric]

Very impressive!!!!

I've thought of having Dirty Dawg make up some chassis. Depending on how you are going to mount the amp you may want to consider something on the lines of these:

http://www.ebay.com/itm/Aircraft-nutpla ... 43a81f28ce

now as they are easier to install before the amp is completed.

Looking forward to more, thanks for the pictures.

Eric

[telentubes]

dreric, The short side chassis lip is drilled for these "captive nuts" from McMaster Carr.
http://www.mcmaster.com/#catalog/117/3200/=fekf7a. They accept 1/4"/20 machine screws.

[M Fowler]

Nice build.

I have Ddawg make my chassis 19.5x8x2.5 so they fit the Gabkit cabinets intended for ceriatone perfectly. Otherwise I use 19.25 and order cab from taylor.

Mark

[telentubes]

My chassis is 19 X 8 X 2 1/2. I'll make my own box. Probably a combo, with an EV12L I've had for about 25 years.

I have a rotary switch coming for speaker ohm setting, but I may not have allowed enough room for the switch, in which case I'll wire the jacks either for 4/8 ohms, or 8/16 ohms. Anyone have an idea which would be the most useful?

[M Fowler]

4/8/16

[Structo]

As for the impedances, determine what is the majority of cabs you use, I like two 16 ohm speakers in parallel for 8 ohms.

I've never had a 1x12 that sounded good to me so I always run two or four speakers.

A 16 ohm load is somewhat rare unless you do series wiring.

[telentubes]

When looking at pics of other folks builds, I've noticed that some people are running caps in parallel with the diodes of the rectifier. I read about this in Dan Torres' book a while back. He recommends a 470K resistor, as well as a .01 1000V ceramic cap to protect and smooth out the rectifier.

Of course I noticed that this was being done after I built mine. Do you guys recommend this? I'm happy to go back in and add one or both of the components if it's a good thing to do.

[martin manning]

If you have diodes in series it is a good idea to parallel a cap with each one to equalize the voltages. It's the same principle as the balancing resistors on the series connected reservoir caps. Nice looking build, there!

[CHIP]

Great work. Very well planned out. can't wait to hear it.

[BobW]

If you have diodes in series it is a good idea to parallel a cap with each one to equalize the voltages. It's the same principle as the balancing resistors on the series connected reservoir caps. Nice looking build, there!

Hi Martin, If Im not mistaken, since the Vf is so low ~.7V, it's not a problem in the forward direction, and if using the 1N4007s, they have a Vbr of 1kV each. Aren't the caps for smoothing any spikes at the knee of the Vf, which is why FREDS are preferred?