Revisit #0183 with 5-piece chassis

[gonzomode]

Very impressing build! Possibly you can‘t go further in terms of cloning..
There seem to be an additional grounding point for the loop jacks. What‘s the difference in grounding them at this spot?

Thank you.

I am not sure of the effect other than it possibly eliminates a ground loop at the EFX send/return. I copied this directly from an original specimen just a few serial numbers earlier than #0183 and based on everything that I can see and match up between that amp and the pics I have of #0183, they are pretty much identical in wiring and layout. Both send/return jacks are isolated and there is a separate ground wire for each running to that ground point

Thank you, that makes sense. I assume the PI ground goes also to this point?

[ijedouglas]

Very impressing build! Possibly you can‘t go further in terms of cloning..
There seem to be an additional grounding point for the loop jacks. What‘s the difference in grounding them at this spot?

Thank you.

I am not sure of the effect other than it possibly eliminates a ground loop at the EFX send/return. I copied this directly from an original specimen just a few serial numbers earlier than #0183 and based on everything that I can see and match up between that amp and the pics I have of #0183, they are pretty much identical in wiring and layout. Both send/return jacks are isolated and there is a separate ground wire for each running to that ground point

Thank you, that makes sense. I assume the PI ground goes also to this point?

Actually, it's grounded at the input ground along with V1 and V2

[ijedouglas]

That makes more sense that he was grounding it to the baseplate. In the real Dumble he still grounds the speaker jack to the chassis (back panel) as well as the safety ground...

That makes a lot of sense, but why not take the same approach for the safety ground and speaker (OT secondary ground)? Maybe HAD's loop and input jack treatments were also a fix for a noise problem?

No idea. Maybe keep sensitive grounds on the baseplate?

[gonzomode]

Ah ok It’s interesting to see so many little differences between the layout and original pics (and your build), noval sockets turned 180 degrees etc…
One more question. Are these nte caps metalized polyester? I just started my own 183 build and try to find subsitudes similar in composition an construction.

[ijedouglas]

Ah ok It’s interesting to see so many little differences between the layout and original pics (and your build), noval sockets turned 180 degrees etc…
One more question. Are these nte caps metalized polyester? I just started my own 183 build and try to find subsitudes similar in composition an construction.

Yeah, the layouts are a great starting point but I always reference the actual pics (when available).

The NTE caps are 630V Mylar (polyester film).

[GAStan]

Looking at your photos it looks like your power tube screen (edit: i mean Control Grid) resistors are 500 ohm 5% (black-green-red-gold)? The layout and schematic call for 5k6. Please correct me if I'm mistaken.

If I'm correct, what affect does this have on the tone? I understand the theory, basically less resistance provides more current and voltage to screen.

I'm curious because I'm at the point of my own build where I'm installing screen (Control Grid) resistors and have a choice of NOS 4k7 or current production Yageo 5k6, both CF. I'm curious what the 4k7 would sound like vs the 5k6 not accounting for NOS vs current production.

Screenshot_20231228_095446_Gallery.jpg

[jabguit]

Looking at your photos it looks like your power tube screen resistors are 500 ohm 5% (black-green-red-gold)? The layout and schematic call for 5k6. Please correct me if I'm mistaken.

I see 1k5 screen resistors. You mean grid resistors @ 5k6?

cheers,

[martin manning]

The g1 resistors look to be 1k5’s to me.

[GAStan]

Looking at your photos it looks like your power tube screen resistors are 500 ohm 5% (black-green-red-gold)? The layout and schematic call for 5k6. Please correct me if I'm mistaken.

I see 1k5 screen resistors. You mean grid resistors @ 5k6?

cheers,

Yes I meant Control Grid, I made an edit to my post.

Thanks for the correction

Screenshot_20231228_095446_Gallery.jpg

[GAStan]

The g1 resistors look to be 1k5’s to me.

First band looks black on my phone screen but 1k5 makes more sense, not sure I've seen a black first band before (not to say its never been done).

Still my question stands.

Again, the correction is appreciated

[ijedouglas]

Looking at your photos it looks like your power tube screen (edit: i mean Control Grid) resistors are 500 ohm 5% (black-green-red-gold)? The layout and schematic call for 5k6. Please correct me if I'm mistaken.

If I'm correct, what affect does this have on the tone? I understand the theory, basically less resistance provides more current and voltage to screen.

I'm curious because I'm at the point of my own build where I'm installing screen (Control Grid) resistors and have a choice of NOS 4k7 or current production Yageo 5k6, both CF. I'm curious what the 4k7 would sound like vs the 5k6 not accounting for NOS vs current production.

I used 5K6 (green/blue/red/red/yellow band) (see attached). Before I found the 5K6 I had used 4K7 and I really could not tell a difference. It may have been a bit brighter but that may have been some other changes to be honest. If you have NOS Q-line 4K7...use em!!!

Screenshot 2023-12-29 063623.png

[GAStan]

I can see the green blue red in the pic you just posted. Odd, must be my screen or I'm just getting old lol.

The 4k7's I have are Draloric I believe, from Jelle. I will use them, thanks for the recommendation.

As always I'm grateful for the reply!

BTW beautiful work wrapping the leads around the hookup wire, not an easy thing to do well.

[martin manning]

I can see the green blue red in the pic you just posted. Odd, must be my screen or I'm just getting old lol.

Looked black or brown on my screen too, and messing with the color balance didn't help.