New to Forum - Beginning First Build

[prspastor]

Hello to everyone. I joined the community a few months ago and have been digesting all of your wisdom. Thank you all for the fantastic community you have here. I've studied tube amp design for years but I've never had the courage to build anything as of yet.

I am building an Express and I wanted to get some feedback from you all. I've got about 90% of my parts in and have wired up most of the circuitry on the turret boards. I still need to order some parts from Mouser, thus the missing parts on the power board.

I have made one mistake that I know of thus far - the chassis I bought is about 2" shorter in depth than Ken's chassis. I'm attempting to make it work, thinking about where leads are going to go and trying to eliminate as many possibilities of hum as I can.

I've included photos below of my proposed layout. I know that the PT and the OT need to be at 90 degrees to one another. Right now, I've got the OT sitting on the outside of the chassis where the filter caps will be on the inside of the chassis. There is enough room between the primary and secondary taps inside the chassis to silicone in those filter caps. The OT primary will come out near the B+ distribution turrets on the tone and PI board and have a straight shot to the power tubes. The secondary taps of the OT will run beside or underneath the power board at a right angle to the B+ coming off the power board.

I'm hoping that this won't create a humming nightmare. Your thoughts?

One other change I'm planning is to have three speaker jacks and not use a Stackpole switch. I'll create a common bus and have a 4, 8, and 16 ohm jacks. I realize this is not following in Ken's footsteps - my apologies... I just don't like those switches all that much.

I'm thinking of using Amphenol jacks for in and outs. I follow Mike Zaite of Dr. Z amps and he seems to have had trouble with Switchcraft jacks of late. My Route 66 has an Amphenol jack in it and it seemed to be a good alternative.

A couple other questions regarding transformers:
1) I'm assuming I can cut off the unused PT taps and put heat shrink tubing on the ends of those taps to terminate them?

2) Are the taps on these Heyboers still:

HTS-5199
300 - 260 - 0 - 260 - 300
Yellow Yel/Green Yel/Red Yel/Green Yellow
6.3 volts are the brown
5 volts are gray
120v mains are black on the primary.

HTS - 9384
Primary:
Blue is center tap
Purple and green to the power tubes
Secondary:
Black = common
4 ohm = red
8 ohm = yellow
16 ohm = gray


Thanks all, and I look forward to more discussion.

Best,
John

Pics:
Here is my proposed chassis/transformer layout with tone/pi board laid on top for scale:
[img:400:300]http://lh6.googleusercontent.com/-Uqecg ... M_0114.JPG[/img]

Tone Board:
[img:400:300]http://lh3.googleusercontent.com/-JlFI3 ... M_0115.JPG[/img]

Incomplete Power Board:
[img:400:300]http://lh4.googleusercontent.com/-R1o3G ... M_0118.JPG[/img]

[Jana]

If it was me, I would spin that PT 90 degrees, spin the OT 90 degrees and move the OT to the left so it is centered under the two power tubes. Keep the PT as far to the right as possible (and still clear the cabinet bracing, etc.). Keep the center lines of the PT and OT lined up.

[LarryLarry]

All I would suggest is using the headphone trick (just search for it) before you actually bolt down the OT. You want to make sure you have as little hum as possible even if it means the PT/OT orientation isn't a perfect 90 degrees.

[Reeltarded]

OMG NOOOO NOT ANOTHER NEW GUY!!!!! GOD HELP US!!

Just kidding. Hey!

[prspastor]

Thanks Jana - Something like this?
[img:640:480]http://lh6.googleusercontent.com/-RDLbf ... M_0122.JPG[/img]

I'm assuming that the secondarys coming off the OT can be routed (braided together) under the tone board's biasing section without problems?

I've not drilled the tube socket's holes yet - so I can move them around too.

Thanks! This looks good!

LOL - yeah, another new guy.

Thanks for the headphone trick lead, Larry.

John

[John_P_WI]

You may wish to buy a larger chassis, the current one can always be used for another project. After all, you can't build just one amp.....

[Jana]

Yes, that is exactly what I meant. It wouldn't hurt to verify with the "headphone trick" but this orientation has never failed for me.

[prspastor]

I appreciate all of the help, everyone. I think I'm going to just order a 17x8x2 chassis to avoid problems with tuning the amp later on. One of the members here sent me a helpful link on where I can order one. Thanks William!

John

[prspastor]

Ordered a chassis from Gainmaster (Dirty Dawg Amps) this morning, here on Amp Garage. Really nice guy...

I'll see if I can get this other chassis cut down at the local community college and make it the size I'll need for an Airbrake.

As far as the unused transformer taps, am I right to just cut them off and put heat-shrink tubing on the ends?

Thanks for helping a newbie.

John

[LarryLarry]

I personally don't cut unused taps short, just in case... The trade off is ugly wires! I coil them up, tie-wrap them and heat shrink the ends. Up to you!

[M Fowler]

I also keep my unused taps long just in case I decide to do something different later and yes I have gone back in and performed surgery using those unused taps on some builds.

You can't go wrong with Brian's chassis good call but I personally though you had more then enough room with the current chassis.

Mark

[DaveMon]

hmmm.... my transformers are even closer together than his.. Jana, can you elaborate on the benefits of rotating the OT and PT? I understand separating them.....cant figure out why which way they are facing matters?

[M Fowler]

I though that the winding should be facing out as in the first photo but I have done it both ways.