Please check my layout for my OD reverb

[jackson649]

I have just completed my layout for a OD reverb. Didn't know how to draw it using a computer program so please excuse my drawing skills.

This is my first layout drawing so please let me know if you see anything that looks wrong. Thanks

Warning, image is large, and was scanned is three parts, so some linesmight not line up.

[dogears]

Lookin' good!!!

A few suggestions.....

1) The midpot should be a 250Ka. Trust me. The .01 midcap wants this.

2) Try and get 30% tapers for the audio taper pots. You may want to use a 250K linear for the treble. Available audio tapers may be too slow.

3) Consider using 22uf on the V1a and V1b cathode bypass caps. Use your ears as both 10uf and 25uf were used in the real amps.

4) Ditch the 500k OD trimmer. I have tried it and I MUCH prefer the 100k trimmer. I asked Gil Ayan and he agrees. Only that one amp had a larger trimmer. All the other amps had 100k. I really did want it to work but not good..... Remember, the degooped amp had a modified trimmer. It wasn't 500k in any event.

5) Use the Hybrid A dropping string. 24k/2.2k into V2 and V1

6) Use a FET simulating resistor to ground off the last dropping resistor. 150k. Very very important.

7) Consider a 330pf treble cap, or use a switch to get both.

8 ) Try a 10pf to 15pf bright cap on the master.

9) ***** Use 270pf snubbers on V2. I didn't see them on the layout.

Use the PS series Orange Drops. Vishay Dales on plates.

Good luck!

[Bob-I]

My only suggestion is to try to get the tubes lined up better with the board. Some of the runs are pretty long, if you can either shift the board right, or shift the tubes left that'd be a help. If you can't do that, try to adjust the spacing of the components to better match up.

Otherwise it looks great.... oh ... and listen to Scott (dogears) he knows all.

[Normster]

Looks good. I agree with Bob about the spacing. Things will line up fairly well if you use 3/8" component spacing with the tubes 2" on center. You may want to use 1/2" spacing for the last 3 rows of terminals since you'll need room for those .1uF caps.

I'm not sure, but I think the OD trimmer should have the wiper going to V2 instead of to ground. Also, Dogears and Gary both recommend putting a 2W resistor between B+2 and the reverb tranny to isolate it from the screens. Something between 24K and 56k should be fine.

Since you've got the tubes wired for 6L6 or EL34, you may want to increase the screen resistor to 1k. I don't know how much it effects the tone, but maybe one of the gurus will jump in here and let us both know.

Anyway, looking VERY good. Happy building.

[jackson649]

Thanks guys for replying. Just to let you know this will be a first build, but I do have a background in electronics but not tubes and audio equiptment in particular.

Also thanks to Scott for the suggestions, but forgive me because I am not familiar with some of the terms you are using, and my eletronics theory went out the window when I finished school. Just to make things easy, could you please explain the following in layman's terms. Thanks

2) Try and get 30% tapers for the audio taper pots. Available audio tapers may be too slow.

(Don't really understand what 30% taper means? )

3) Consider using 22uf on the V1a and V1b cathode bypass caps. Use your ears as both 10uf and 25uf were used in the real amps.

(Are you refering to the caps with the 1.5k resistors across that connect to pin 3 and 8 cathode on V1 tube)

5) Use the Hybrid A dropping string. 24k/2.2k into V2 and V1

(Don't know where the dropping string is.)


6) Use a FET simulating resistor to ground off the last dropping resistor. 150k. Very very important.

(Again, don't know where the dropping string is, or to wire this in particular)

7) Consider a 330pf treble cap, or use a switch to get both.

(Just wondering, whats the difference between a 330pf and 270pf cap in sound?)

8 ) Try a 10pf to 15pf bright cap on the master.

(Don't know how to wire this? Across the wiper and outside lug? Don't know)

9) ***** Use 270pf snubbers on V2. I didn't see them on the layout.

(Whats a snubber and where do I put these 270pf caps.)

I know these are a lot of questions, but please keep in mind that I am an idiot.

Thanks again!

[groovtubin]

Thanks guys for replying. Just to let you know this will be a first build, but I do have a background in electronics but not tubes and audio equiptment in particular.

Also thanks to Scott for the suggestions, but forgive me because I am not familiar with some of the terms you are using, and my eletronics theory went out the window when I finished school. Just to make things easy, could you please explain the following in layman's terms. Thanks

2) Try and get 30% tapers for the audio taper pots. Available audio tapers may be too slow.

(Don't really understand what 30% taper means? )

3) Consider using 22uf on the V1a and V1b cathode bypass caps. Use your ears as both 10uf and 25uf were used in the real amps.

(Are you refering to the caps with the 1.5k resistors across that connect to pin 3 and 8 cathode on V1 tube)

5) Use the Hybrid A dropping string. 24k/2.2k into V2 and V1

(Don't know where the dropping string is.)


6) Use a FET simulating resistor to ground off the last dropping resistor. 150k. Very very important.

(Again, don't know where the dropping string is, or to wire this in particular)

7) Consider a 330pf treble cap, or use a switch to get both.

(Just wondering, whats the difference between a 330pf and 270pf cap in sound?)

8 ) Try a 10pf to 15pf bright cap on the master.

(Don't know how to wire this? Across the wiper and outside lug? Don't know)

9) ***** Use 270pf snubbers on V2. I didn't see them on the layout.

(Whats a snubber and where do I put these 270pf caps.)

I know these are a lot of questions, but please keep in mind that I am an idiot.

Thanks again!

Believe me dude EVERYONE at this forum, and i do mean EVERYONE was an IDIOT BEFORE DE-GOOPED PIX!! LOL! Go EASY on yerself, just build and have fun, aint NO-ONE here in Howards league, NO-ONE LOL!

[Bob-I]

2) Try and get 30% tapers for the audio taper pots. Available audio tapers may be too slow.

(Don't really understand what 30% taper means? )

The taper is how much the resistance changes as you sweep the pot. 30% means that the wire is at 30% total resistance at the mid point.

That said don't fret over it, it helps smooth out the controls a little but it's not overly important.

3) Consider using 22uf on the V1a and V1b cathode bypass caps. Use your ears as both 10uf and 25uf were used in the real amps.

(Are you refering to the caps with the 1.5k resistors across that connect to pin 3 and 8 cathode on V1 tube)

Yes.

5) Use the Hybrid A dropping string. 24k/2.2k into V2 and V1

(Don't know where the dropping string is.)

In the power supply there's resistors between the filter caps. This is called the power supply rail (PS rail), and the resistors drop some voltage along the rail. So the "dropping string" is this series of resistors.

Try to adjust these resistors so that V1 and V2 plates read as close to 200V as possible. V1 will be slightly lower, maybe 195, and V2 may be slightly higher, but 200V seems to be the sweet spot between harsh *too much voltage) and spongy (too little voltage)

6) Use a FET simulating resistor to ground off the last dropping resistor. 150k. Very very important.

(Again, don't know where the dropping string is, or to wire this in particular)

Dumble used an FET input powered from the PS rail. It's resistance is approx 150K so place a 150K 5 watt resistor from the final filter cap to ground. This helps to adjust the voltages to the above mentioned voltages.

7) Consider a 330pf treble cap, or use a switch to get both.

(Just wondering, whats the difference between a 330pf and 270pf cap in sound?)

They cost about $.10. Buy some and experiment. The 270pF will be somewhat brighter.

8 ) Try a 10pf to 15pf bright cap on the master.

(Don't know how to wire this? Across the wiper and outside lug? Don't know)

Wiper to the hot (not the ground) lug. It passes some high end around the volume pot which tends to tighten up the bass, less farty.

9) ***** Use 270pf snubbers on V2. I didn't see them on the layout.

(Whats a snubber and where do I put these 270pf caps.)

"Snubber" is a small cap that drops some of the extreme highs. You connect it from plate to cathode, directly on the tube socket. There's a thread I started on how this works with a ton of good information.

I know these are a lot of questions, but please keep in mind that I am an idiot.

Thanks again!

No you're not, these are valid questions. I wish there'd beena Dumble forum when I started building my first. I learned most of this stuff from dogears, normster and glassman, great resources and great guys.

[jackson649]

Thanks Bob and Normster, I've made some updates to the layout as suggested. Can you guys tell me if these updates look right, ie) snubber and dropping resistors. Again, please let me know if anyone else has any more suggestions or sees anything that looks funny. Thanks

[Bob-I]

The snubbers, dropping string and tone stack values are correct now, and the cathode bypass caps match the dogears values (jury's still out for me on these but I trust Scott)

Why the diodes on the power tubes? I've never seen this on a Dumble and they tend to be very stable. I've never had a correctly wired Dumble oscillate or exibit any other nastyness.

Remember that the dropping string is a starting point, you may need to adjust some values, especally the 22K, to get the right voltage on the preamp plates.

Also I'd move that 150K at the end of the power rail to parallel the 47uF caps just for the sake of a clean layout.

Looks excellent, get started!!

[dogears]

Bob,

THis layout has the 100k/1.5k combination. 10uf is a certainty and maybe 22uf is better. On the later era plate/cathode values, I like 5uf on CL1 and 10uf on CL2.

The snubbers, dropping string and tone stack values are correct now, and the cathode bypass caps match the dogears values (jury's still out for me on these but I trust Scott)

[Normster]

Why the diodes on the power tubes? I've never seen this on a Dumble and they tend to be very stable. I've never had a correctly wired Dumble oscillate or exibit any other nastyness

Bob, the diodes are a Ken Fischer mod that's supposed to protect the tranny if a power tube shorts out.

[Bob-I]

Bob,

THis layout has the 100k/1.5k combination. 10uf is a certainty and maybe 22uf is better. On the later era plate/cathode values, I like 5uf on CL1 and 10uf on CL2.

Of course it does, I knew that.... yea... I knew that

[jackson649]

I'm starting to compile a parts list and have a couple of part selection questions.

1) Planning to buy the power and output transformer from Weber. With this particular layout, can I use a super reverb power and twin reverb output tranny combination. I'm asking because both power trannys have different secondary votages coming off the reds. The Hybrid A schematics say 345V-0-345V. I assume that means it needs 690V peak to peak. From the diagram of the weber trannys, the super and the twin voltaes off the red leads on the secondary are 720V and 640V. Please help me out with this as I don't want anything to blow up when plugging it in the first time.

Check out these trannys W022798 and W022756 on the link

https://weberspeakerscom.secure.powweb. ... gnetic.htm

2) A lot of people here build their clones based on Robben Ford sound with humbucker. I use a strat with single coils and want more a SRV sound, raw sounding. Are there any componets that I can replace to go with my style and guitar?

Thanks

[Bob-I]

I'm starting to compile a parts list and have a couple of part selection questions.

1) Planning to buy the power and output transformer from Weber. With this particular layout, can I use a super reverb power and twin reverb output tranny combination.

Yes


I'm asking because both power trannys have different secondary votages coming off the reds. The Hybrid A schematics say 345V-0-345V. I assume that means it needs 690V peak to peak. From the diagram of the weber trannys, the super and the twin voltaes off the red leads on the secondary are 720V and 640V. Please help me out with this as I don't want anything to blow up when plugging it in the first time. [/quote]

You won't blow anything up. These Weber xformers have 120 and 125V primary taps. If you connect to the 125V tap you'll drop the 720 slightly. You'll be in range.

Check out these trannys W022798 and W022756 on the link

https://weberspeakerscom.secure.powweb. ... gnetic.htm

These are the power xformers. Either is fine. You really don't need the Twin PT since you're only using 2 output tubes the Super PT will supply enough current.

2) A lot of people here build their clones based on Robben Ford sound with humbucker. I use a strat with single coils and want more a SRV sound, raw sounding. Are there any componets that I can replace to go with my style and guitar?

Thanks

Robbin Ford also uses a Tele in the clean channel, not really SRV tone but a great tone in itself. For SRV type tones you'll be using the clean channel, the OD channel is just too much distortion/gain for SRV type tones.

I wouldn't change a thing until you're up and running, then adjustments can be made.

[jackson649]

Please help me, I do not know what the function of some of the controls on this layout. On this layout, please discribe what the circled pots and swtiches do. Thanks