SSS a Hartman Manning Affair

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martin manning
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Re: SSS a Hartman Manning Affair

Post by martin manning »

Note 310V screen voltage for p-p. That drops the Vg1 = 0 knee down to the load line.
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didit
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Re: SSS a Hartman Manning Affair

Post by didit »

Yes, noted. And so impacts screen supply design. It was 77W vs 70W max power, THD and P-P load that left me a bit puzzling.
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jelle
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Re: SSS a Hartman Manning Affair

Post by jelle »

Or go for all the power available...
6550A.JPG
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dreric
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Re: SSS a Hartman Manning Affair

Post by dreric »

So after much deliberation I've decided to run the amp in standard linear wiring rather than the ultra-liner. The main reason is simply that no one, other than Sunn, has made a good sounding guitar amp with the ultra linear design. I can always change it up later if there are complications.

Thinking ahead I found this post by Martin regarding the step filters:

http://ampgarage.com/forum/viewtopic.php?f=5&t=30118

I built SSS #2 and while I'm happy with the build the filters don't really seem to do much. One of my inspirations for making the Hartman version is to study how the filters work in his version of the amps. I'm planning on trying out Martins "take" on the filters.

Then there's the inductor...........................

I do think of HAD as a brilliant designer. That said, we have the luxury of studying his designs retrospectively and from this perspective he was clearly learning as his amps evolved.

I've always wondered about the inductor. If it really didn't do anything, why would HAD use it? He's meticulous about details and his designs are efficient. It dosn't seem right that he would have a component in an amp that didn't do anything. It leads me to speculate. Perhaps there's something special about the Sprague inductors he used; I've never been able to find one.

OR perhaps we have the wiring wrong. I'm self taught with all of this and I'm good at making things look like the picture and my electronic knowledge and theory improves with each built. There are those on TAG that have knowledge that rivals HAD. Perhaps some of you would share your thoughts on how to make the inductor meaningful.
Eric
1949 Zenith, Zenith Toggle Recoil, Zenith 55 & 440
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didit
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Re: SSS a Hartman Manning Affair

Post by didit »

jelle wrote: Tue Oct 24, 2017 11:48 pm Or go for all the power available..
Depends on available B+, and seems iron has been selected. Differences too beyond raw watts, with higher voltage and taller transformer primary. Some prefer sounds provided with a lower B+ along with higher current. Initial comment was more the surprising differences references in that sheet between UL & non-UL. Punctured somewhat the conventional wisdom.
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didit
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Re: SSS a Hartman Manning Affair

Post by didit »

dreric wrote: Sat Oct 28, 2017 12:51 am The main reason is simply that no one, other than Sunn, has made a good sounding guitar amp with the ultra linear design.
Agreement the conventional primary connection is correct for original SSS. There are, however, fine sounding amps for guitar with UL. Marshall '67 200W, mid-'60s Magnatone, Dr. Z, and Alessandro are well reputed. Reports generally are good. My Magnatone M15 sounds wonderful. Rumours even notorious late silverface Fenders can be redeemed with tweaks, while still keeping the basic UL circuit. These all will tend to clean, somewhat like the SSS. Removing/reducing GNFB essential, in my view.

No thoughts to offer on mysteries of Sprague inductors.

Best .. Ian
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mhartman
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Re: SSS a Hartman Manning Affair

Post by mhartman »

Looks like a great project!
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dreric
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Re: SSS a Hartman Manning Affair

Post by dreric »

Here's a step back in the process.

I've learned the hard way that it's best to make the cabinet and to figure out the mounting first. It's quite a pain to try and drill and mount a completed amp.

I've always found Dumble's chassis mounting system to be remarkably annoying. Very unforgiving and hanging an amp off a 1/4"aluminum lip ......... next thing you know we'll be gluing filter caps together.

So for this one, 1/4 lag bolts, there's plenty of room.

Just a note on making the boards. When I have the chassis dimensions confirmed I take the image file to the local print shop and have them blow it up to that the image matches the chassis dimensions. Two copies; one gets cut up taped to the garolite and drilled. The other copy is my build guide.
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Eric
1949 Zenith, Zenith Toggle Recoil, Zenith 55 & 440
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alkuz1961
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Re: SSS a Hartman Manning Affair

Post by alkuz1961 »

I would advise to install additional cross bars on the sidewalls. It facilitates installation and removal of chassis.

Image

Image
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norburybrook
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Re: SSS a Hartman Manning Affair

Post by norburybrook »

some lovely looking cabinet work there guys :D I envy you all having garages/workshop basements etc to be able to do this. I live in one of the most congested cities in the world so have no space to do this properly. I sometimes have to drive around for 15 minutes just to find somewhere to park my car!!

Thank god for tolex :D I agree about the dumble chassis mounting being a PIA , it's very difficult to get the cabinet holes in the correct place so everything is square and in line when fitted. Also the side rails are an addition I put on too to support the chassis, it means the bolts actually really only have to stop forward /backward movement in the cabinet.



Looking forward to this build coming together.



Marcus
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dreric
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Re: SSS a Hartman Manning Affair

Post by dreric »

alkuz1961,

That's an early picture, I did put in a cross bar for support.

Nice looking cabinet work on your builds.
Eric
1949 Zenith, Zenith Toggle Recoil, Zenith 55 & 440
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dreric
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Re: SSS a Hartman Manning Affair

Post by dreric »

So, a little work this week.

FET, minus the 2 caps on order is wired.

Shielded cable runs completed.

Power supply wired and tested. Martins alternative bias supply works!

Switches are wired.
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Eric
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dreric
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Re: SSS a Hartman Manning Affair

Post by dreric »

Next up are the filters................

Considering the tile of this build I wanted to incorporate Martin's take on the step filters detailed in this thread:

http://ampgarage.com/forum/viewtopic.ph ... 57#p378857

I do need to ask a stupid question regarding the 4n7, 6n8, 3n, 1n5 caps. These are nanofarads? I can't find any at mouser that are not surface mount, am I missing something?

Also, in my quest to give the inductor purpose I am wondering if it wasn't placed as in the old Gibson varitone circuit.
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Eric
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martin manning
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Re: SSS a Hartman Manning Affair

Post by martin manning »

Re the filters, yes nanofarads. IMO it's much easier to write 4n7 than 0.0047u or 4700p. You could use CDE 150's: https://www.mouser.com/Search/ProductDe ... 0472J630BB or these Panasonics: https://www.mouser.com/Search/ProductDe ... Q-E6472JF3

Interesting thought about the Varitone circuit. HAD borrowed from others just like everyone else so there might be something to that. Like you I find it hard to believe he would keep the inductor in the circuit if it doesn't do anything, but the response of the filter as shown looks like it will be very effective.

I see you have both the bias trimmer on the filter board and the full-size bias trim pot mounted on the chassis. You don't need both, so maybe you could remove the trimmer and run three wires from the bias pot lugs to the trimmer eyelets?
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JazzGuitarGimp
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Re: SSS a Hartman Manning Affair

Post by JazzGuitarGimp »

Both the Mouser and Digi-Key search engines will return more hits if you specify nF as pF. Try searching for 4,700pF rather than 4.7nF.
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