new build choice, 2nd gen 50w

[norburybrook]

Marcus what schematic and layout are you using? This layout? http://ampgarage.com/forum/viewtopic.ph ... 70#p140259
There is no schematic in that thread... I know one exists, but I don't know where it is.

Martin.

Yes that's the one. I'm going to use the fact I've built a few later amps as a grounding in putting this together from just the layout. I didn't see anything except the relay wiring that caused me any concern. I always have some issues with the relays/foot switch wiring so I'm expecting no less with this [emoji3].

I will do the OD relay with a voltage regulator and 5v omron relay as on my other builds so I'm hoping I can work out how that translates to this fairly easily by just using the supply board from the later builds.

My mouser and tube town order are arriving Monday so I'll probably make a start next week as I'm home from the first week of my tour.

I do love a new build.

Marcus

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[norburybrook]

I built a hybrid #40 with a master for the OD channel and integrated Dumbleator. Footswitchable FET boost. Best Dumble circuit I've ever built for singelcoil pickups!



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I love mine too! Best sounding built with clean and overdrive for strat.

Marcus, a 4 pin cable is fine. I got mine with 5 pin but also have a pab.

On the PI: the values for the plates are designed to work with 12AT7. The Miller effect on a 12At7 is less so you got a little more highs. Also the Nfb resistor coming from the ot sec. is smaller(more Nfb!).
You might want to change that to 4k7 instead of a 3k3.

Erwin, I'm going to go with the AT7 and see how I like it. I think anything that makes it different from the later amps is a good thing for me as I'm after something different.

Marcus

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[fred.violleau]

[I'd love to do an on board loop, I might look into it on this build. Did you put everything on the main board or hang stuff off terminal strips near the valve?

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Hey Marcus,

When wiring my internal D-lator, I realized you need a small board + all the terminal strips connections and it then space is cluttered anyways.

I wish I had seen that little board earlier in the process so I would have had everything on one single board. Easier to troubleshoot and organize, and you just need to solder the cables to the tube socket.

My two cents here [emoji6]


Humble and Dumble,

Fred.

[dbeasley]

I used to have a drill template layout for a Dumble circuit with integrated D lator somewhere....

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[erwin_ve]

Here http://ampgarage.com/forum/viewtopic.php?f=4&t=30186 is a layout of HRM with dlator on the board. Printed in 100% it's a drill template . With a few twists you can do the 2nd gen.with it.

[norburybrook]

THanks Erwin/Fred

Just got home yesterday to my two packages from Tube town and Mouser. I've got the wrong slide switches...that's the problem with a data sheet that covers about 100 switches rather than an actual data sheet/photo of the switch you want! and I've got the wrong size pots too. So an expensive postage order again to get the correct switches!

Also the footswitch connecter is only 3 pin so I can't think of a way to make that work with two relays, so I'll be building it 'stock' #40 ...as HAD intended

Marcus

[Mark]

Keep the photos coming Marcus. I look forward to seeing your build.

[Aaron]

Keen to hear it when it’s done. Are you doing the standard funky OD input? I did a 2nd gen build with a 12AT7 PI, but couldn’t gel with the funky input and went with the 100k trim/220k.
Also, I’ll be visiting the U.K in June

Thanks,
Aaron

[norburybrook]

Aaron,

I'm going to build it exactly as it is on the layout. I tend to do that with a new build and then tweak if I don't like it.

Quick question, what sort of jack does the FET use as I've never used one before? From the layout it looks like a stereo socket but it has two sets of sprung contacts/switch. I can only find standard stereo sockets , nothing like those.


M

[martin manning]

The layout shows a Switchcraft 14B stereo jack. My preference is 13E, with isolated break contact.

[norburybrook]

Thanks Martin,

I think I have a 14B so I'll use that.

M

[mojotom]

THanks Erwin/Fred

Just got home yesterday to my two packages from Tube town and Mouser. I've got the wrong slide switches...that's the problem with a data sheet that covers about 100 switches rather than an actual data sheet/photo of the switch you want! and I've got the wrong size pots too. So an expensive postage order again to get the correct switches!

Also the footswitch connecter is only 3 pin so I can't think of a way to make that work with two relays, so I'll be building it 'stock' #40 ...as HAD intended

Marcus

The slide switches HAD used on the 70's amp were quite bigger than the actual type of switch available today.
I was able to find some at a local store (with lots of old school components stock) but they haven't been as reliable as toggle switches (they feel cheap when you use them, full plastic construction and could make some noise too).
I remember a picture from a 70's converted to toggle switches (he made little rectangular metal adaptator bolted to the 6 slide switches holes and drill for toggles).

Anyway quite logical for you to receive "smaller" slide switches from Mouser are these are the norm now.
I would consider converting to toggle even if I prefer the amp bright off, depth off, rock on so I don't use them often.

Regarding the FET I used an open metal switchcraft jack for it but if I have to do it again I would find an enclosed plastic one for the FET switching like HAD did as I don't trust the switching reliability of those open jacks.
It was OK 15 years ago but they must have change tooling or process or materials as I didn't have any issue before.
A Mil spec version is available, maybe correcting the issue.

On mine I had switching issues after 2 years or so. If I was rebuilding it (I should) I would put a plastic one (still from switchcraft).

[martin manning]

Marcus, what are the dimensions of the slide switch mounting screws (c-c), and the cut-out (hxw) in the chassis?

[norburybrook]

Guy's

Tube town have the perfect thing, should have ordered there first!


https://www.tube-town.net/ttstore/Switc ... :4305.html



And they're on sale

[norburybrook]

So, made my boards today. I got hold of some Paper/Phenolic resin material that was recommended for high voltage applications. Seems quite 'retro' so I thought it would be perfect for this build. It cuts easily but can get a bit ugly when drilling if you're not careful due to the paper laminations.

Didn't have a 3k3 so had to put a couple of 6k8 in parallel

DSC_1623.JPG

DSC_1622.JPG

regarding the FET socket I have half a dozen of these taken from some Peavey amps. Any good?

DSC_1626.JPG

DSC_1625.JPG

Marcus