Tweed Overdrive Special

[azatplayer]

I hate when that happens! I got smart and did my 5 stars pilot lamp on the concorde clone, totally forgot about the cabs valance and how it sits over the chassis. I set the stars up centred. Didnt realise it till after Larry had my cab cut out..Gotta get Jeanne to do another front for me now!
The chassis im using is in a combo i did, tweed style controls up, tubes hanging. Fixed bias. Trouble is its only got 6 controls on front, no room on the back and i dunno how to get around that. Might just have to drop the ppimv.
Hopefully have mine running in a week or so.

[M Fowler]

You maybe should have used mini pots over/under to save room.

[azatplayer]

Well as its an experiment over an old build, gotta make do. Thp i was just eying off another dead chassis on the shelf thats been a mule. Its got JTM trannies and a tube rec spot and 4 preamp tubes..hmmm O AND 7 pots with room for more!!! Maybe an EL34 version?

[andrew]

Hi, I am looking to build a TOD as a preamp only and I noticed there are some changes to the preamp on the EL-34L schematic (page 4). I'm still nuby but it looks like on the EL34L version V2b and V2a share node D. In the first schematic on this thread V1b and V2a share node E. Has anyone tried this version or can give some advice on what these changes do? Thanks

[10thTx]

IF you are building the TOS as a preamp only, then I'd not worry about whether there is a node D or node E (since you won't have that many nodes anyway).

Instead, I'd create a B+ rail that ultimately gives you around 145-165v on the 12AX7 plates of V1a & V1b. Hope that makes sense to you?

Without knowing what PT you are using and what you're using for a rectifier and how many dropping stages you have .......... it's hard to give you a useful answer.

IF it's just a preamp, you can use a less expensive PT that has lower ma current handling. I'd probably want a 275-0-275 PT and build a B+ rail from that.

with respect, 10thtx

[andrew]

Thanks 10thtx, I am going to use a 275v PT and a SS rectifier that should give me about 290v on the D node I hope. I'm working up an order now. Thanks again.

[10thTx]

I am just guessing about what dropping resistors and Node voltages would be needed for your TOS preamp & OD?

Having said that, this would probably be my starting place.

Obviously, you'd have to keep experimenting to get the plate voltages to be what you'd want.

with respect, 10thtx

[tonewood]

Edit: I am terrible with using drawing software but I think this will work with a clear plexi front. I'll add the holes for the pilot light, brite switch and input jack as I go.

Edit: I will leave faceplate making to the professionals here is my terrible job.

Mark

Mark- I would love to be able to make a face plate that nice. What software do you use & does it come with templates for the dial indicators?

Thanks

[M Fowler]

Tonewood,

I deserve no credit.

I used Visio and the faceplate visio parts file which I think is now a sticky in the Dumble files section.

Because I don't know how to set up the spacing by scale I moved each dial graphic into position and the software has a way of taking over the spacing for me. I used another graphic to indicate drill marks for the jack, bright switch and pilot light holes.

Not very creative on my part but it worked. As you can see I had a hard time getting letters centered.

I copied the art work into .pdf and then printed onto large sketch pad paper loaded in an Epson 1100 large format printer. Marked onto chassis and then used a gasket punch set to make pot holes, etc in the paper. Cut the clear window material from my local Menards building center.

A few days later at a surplus center I found a shelf full of already cut strips exactly 2.5 inches by 18 inch. So I did buy two incase I do this again.

Mark

[tonewood]

Tonewood,

I used Visio and the faceplate visio parts file which I think is now a sticky in the Dumble files section.

Mark

Thanks Mark!

[tonewood]

I am just guessing about what dropping resistors and Node voltages would be needed for your TOS preamp & OD?

Having said that, this would probably be my starting place.

Obviously, you'd have to keep experimenting to get the plate voltages to be what you'd want.

with respect, Tubenit

Hi Tubenit-

Getting ready to start a build and have questions about the differences in the schem included in your most recent post vs the previous one you posted:

Looks like the 10k on the switch would bring the cathode R down to about 1.8k-how do you like it there? Have you tried lower?

The .001 added in parallel with the .01-can you hear a difference with it?

Do you recommend no grid stoppers where you removed them (V1b,&V2a), or does the pot never get turned up all the way - acting as a stopper?

The switched 250p bypass- are you finding that useful?

Thanks!

[wicker]

Is it possible to get from this amp tone like KWS on his last album:
http://www.youtube.com/watch?v=-b0t4QQa800

[10thTx]

Tonewood,

The TOS has undergone numerous versions similar to Dumble amps have numerous versions. DaGeezer and I worked on the original in concert but took different approaches and used some different values in some places.

I think, overall, the results with touch sensitivity, sustain, harmonics and blooming still were there. In other words, the guys on the Hoffman forum that have built the TOS keep reporting similar results to what DaGeezer and I got.

So I am inclined to say they're different rather than one being better.

I think each individual's style of playing, guitar and speaker choice all factors in to what tweaks/values work best for you.

For example, I know I like mids and smoothness. I think Geezer perhaps values a little more chime and maybe brightness? He is a MUCH better guitarist and player than I am & so I can hear how his choice suits his playing style better. He is alot faster in his rifting then I am & he has phrasing skills that are remarkable and waaaay beyond my ability.

I think this is the kind of build that you start with an original schematic and foundation and simply tweak it to your personal taste.

When I read the Dumble cloners posts, it is clear that the small details can make a huge difference in tone. I don't experience this amp quite that way needing exact small details being held to strict standards.

IMO, the grid stoppers are a matter of personal taste since there were no oscillation concerns requiring them. I tried them with and without. Similar to the 250p. Just a personal taste issue.

Regarding the .01 &.001 paralleled. Yes, I could hear a difference. However, the difference may be as much do to using different type of caps as the values difference.

In other words, I would use an Orange Drop PS most of the time when using .01 or larger and then would experiment with the small caps that were paralleled. For example, I might use an OD and a Mallory. Or if it's a small value OD like a .001 to .0068, then I might parallel a silver mica cap and compare that with paralleling a ceramic cap. Sometimes there was a significant difference in tone or harmonics. Sometimes not.

I have a cap substitution and a resistor substitution box which makes tweaking and experimenting much simpler to simply determine the value.

This is more a tweaker's amp than a cloner's amp, IMO. I hope explaining some of the philosophy behind the build was helpful?

With respect, 10thtx

[tonewood]

Tonewood,

This is more a tweaker's amp than a cloner's amp, IMO. I hope explaining some of the philosophy behind the build was helpful?

With respect, 10thtx

Thanks - Great info. I can't wait to get tweakin'

Scott

[M Fowler]

Scott,

No problem here is the link in case others are looking for it.

https://tubeamparchive.com/viewtopic.php?t=1534