Direct wiring instead of a driver board?

[parabellum]

Hello all,

This is my first post here. I am close to deciding to build an ST70 clone as my first tube amp project.

I would like directly wire everything as oposed to buying a driver board. Its not a matter of money as it is me wanting to really build everything myself.

Are there any (non obvious) dissadvantages or problems in doing it this way?

Right now I am in the process of collecting the information and am reading all these build manuals and comments. Its all a bit too much for my head but hopefully I will digest it soon. Kinda worried about these rectifier problems and other issues.

Anyhow thats it for now, if I start this project you will be hearing a lot from me most likely.

[TomMcNally]

Hi - welcome to DIYTube.

There is no reason you can't handwire, it's just very complex to hand
build a push-pull driver. There are many components, and it's kind
of hard to lay them out neatly. One of the major things to be
concerned with when building an audio amp is layout of components
to avoid hum and noise. It's much easier to do on a circuit board
than by hand.

Here are two examples of amps I've built ... this one is push-pull
by hand wiring ...



and here is one with a circuit board ...



There are a lot of parts to mount !

More pix of my stuff at: http://tmamps.com

Good luck with the project - yell if you need help or wanna show us how it turns out !

... tom

[TerrySmith]

I did a '70 a few years ago that I made a plate to replace the PCB, and used a 6SL7 and two 6SN7's wired like an Eico HF-89.

It sounded great except for all the ground loops causing hum.

[Slartibartfast]

Hi - welcome to DIYTube.

There is no reason you can't handwire, it's just very complex to hand
build a push-pull driver. There are many components, and it's kind
of hard to lay them out neatly. One of the major things to be
concerned with when building an audio amp is layout of components
to avoid hum and noise. It's much easier to do on a circuit board
than by hand.

I guess that is why the footprint of that H.H. Scott, model 340A vacuum tube receiver is so large. Well that and the fact that there is 18 tubes in that receiver. It is all point to point wiring, including an FM stereo section. Yellow_Light_Colorz_PDT_20

[mesherm]

When you point to point wire I find its very helpful to decide ahead of time where your ground bus bar will go. Star gounding is great but when you have components all over and many ties to ground I usually work out an "L" or "U" shaped "bar" of 16 gage solid copper as a bus for grounding al the different components.

[parabellum]

Thanks guys!

Since I am not rebuilding an old st70 I can afford to go with a bigger casing and spread things up within it. Tom I checked out your site before I even registered :) some very cool stuff there.

What are some of the things I should watch out for to minimize the possible hum? Mesherm thats a good idea of creating a bus for grounding.

I guess if this goes well and I really get bitten by the "bug" and want to keep making new amps then I will eventually get the equipment for making my own circuit boards. And that would be pretty damn cool.

[parabellum]

forgot to mention that I am thinking about using the Ned Carlson's tubezone ST70 manual that I found in the documentation thread for a blueprint. Any issues with that?

[TomMcNally]

Notice the bus wires in my pix ... I used to use copper house wire - 12 gauge ... I have some smaller tinned bus wire now that's nice. Run it end to end in the middle and only ground to the chassis at one point. I've yet to have a hum problem with that technique. The ST-70 manual should be good ... Shannon's has the Mouser "BOM" which makes ordering parts painless.

[parabellum]

Excellent.

Other then the different tubes is there any difference between the two manuals? From a casual glance they look identical other then the tubes used. So the parts list should be the same?

[TomMcNally]

Yep - it's Shannon's board with Ned's mods ... so either manual is fine

[parabellum]

So its basically just a matter of personal choice on which tubes you want to use?

hmmm I am kinda partial to the 12AX7 though ...

[TomMcNally]

Yep - the DIYTube ST-70 driver board was designed with the ability
to experiment a little ... people have their favorites and want to use
them or at least check them out.

[kheper]

Looking at the diytube driver board, there
are 2 transistors for the CCS and 2 pc
mount pots for the fine tuning of the bias
supply. These components might give
you some trouble wiring point to point.
You could sub for the pots, but the
transistors are fragile, 3-legged, and
have short leads. You would probably
need a terminal strip to mount them.

[TomMcNally]

Here's how I did it in the 6EM7 Push-Pull I built a few weeks ago -
see the CCS to the left of the gold resistor ....

[parabellum]

You guys are great. I really appreciate your help.