EL34 YGL3 -> 6L6 SSS

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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

In fact you could power the CF driver stage with a +/- 160V bipolar supply made from that small transformer. The only additions are switching to a FWB for the bias supply rectifier and adding another cap. Do you have a 2" x 4" footprint somewhere?
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bcmatt
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Re: EL34 YGL3 -> 6L6 SSS

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martin manning wrote:I think you could use a Hammond 229B230 flat-pack, which is small (~2" x 2.5" x 1" high) and cheap ($15): http://www.mouser.com/ProductDetail/Ham ... 7RMJLfk%3d It's a PCB mount, but you could put it on a small board using eyelets.
Thanks Martin! I ordered it this morning, along with a few extra resisters that I was having a bit of trouble finding int he wattages I wanted.

I spent most of the last couple days trying to understand why typical bias tap voltages would not be appropriate (and reading everything I could find about grid biasing). I guess I was a little bit unaware of the much larger bias voltage required with this driver tube. Wanting to see some schematics with Voltages, I had been mistakenly looking at old Twin Schematics, Overdrive Special Schematics. SSS Schematics (and especially with voltages) seem to be a little bit hard to find for me. Finally, after seeing David Root's SSS-001 schematic, I started comprehending what you are talking about. It hadn't clicked for me that I would need a significantly higher bias voltage than any other 6L6 amp.

Therefore, looking at this transformer to use for the bias, I would connect pins 1 and 2 (for 115V) on the primary side to my mains (like my PT), but on the Secondary side, I'm guessing I would want the full 230 Volts, I would ground pin 5, connect pins 6 and 8 together, and get my bias tap off of pin 7. Am I getting this right? Then I can continue with a bias circuitry that looks a lot like Hartman's?

On another note, if there are schematics or voltage information on these SSS's that I have yet to find, it would be much appreciated!
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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

Referring to the Hammond wiring diagram, connect terminals 1 and 3 to one side of the mains, and 2 and 4 to the other side. The two primaries are wired in parallel- note the small dot at one end of each coil indicating the start end. Connect the secondaries in series by connecting 5 and 8 (or 7 and 6) to form a center tap, and get the 230VAC from the other pair.

I don't see the need to put ~700V across the driver stages. If it were me, I'd use the circuit shown below.
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bcmatt
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Re: EL34 YGL3 -> 6L6 SSS

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martin manning wrote:Referring to the Hammond wiring diagram, connect terminals 1 and 3 to one side of the mains, and 2 and 4 to the other side. The two primaries are wired in parallel- note the small dot at one end of each coil indicating the start end. Connect the secondaries in series by connecting 5 and 8 (or 7 and 6) to form a center tap, and get the 230VAC from the other pair.

I don't see the need to put ~700V across the driver stages. If it were me, I'd use the circuit shown below.
Martin! You are a prince among men! Thank you for that work and your help on this. I was having a little bit of difficulty seeing how your diagram fit into the non-existent schematic I have not (yet) made from the Hartman layout, but "self-contained" is really the key term here! So I see this provides the B+ as well for this tube, so that's pretty cool.

Since I have not yet made the boards yet for this amp, I have plenty of room inside to make a board with this tidy little circuit on it. I don't think that will be a problem. Awesome!

I was starting to get a little discouraged about this project, but now I'm super excited again! Thanks! I'll keep posting how this comes together.

I'm already thinking about other handy ways your little self-contained driver tube kit may lend itself into other projects/ amps down the road. Very cool.
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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

It's actually almost the same circuit as shown in the M Hartman layout and even closer to the one seen in the D Root schematic.

The bipolar power supply replaces the screen node voltage feed to the plates, and the negative bias voltage supply. I think I would mount the transformer on a small piece of G-10 by drilling holes for the pins to fit through snugly, then wrap the connecting leads around the pins on the bottom side, tight to the board, and solder.

The rest of the circuit is just different values for the resistors, and the addition of the bias trimmer and grid stoppers. You can mount the grid stoppers on the small terminal strip next to the tube socket, and use the socket lugs instead of the terminal strip to tie the driver tube cathode leads to the power tube grid leads.
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bcmatt
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Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

martin manning wrote:It's actually almost the same circuit as shown in the M Hartman layout and even closer to the one seen in the D Root schematic.

The bipolar power supply replaces the screen node voltage feed to the plates, and the negative bias voltage supply. I think I would mount the transformer on a small piece of G-10 by drilling holes for the pins to fit through snugly, then wrap the connecting leads around the pins on the bottom side, tight to the board, and solder.

The rest of the circuit is just different values for the resistors, and the addition of the bias trimmer and grid stoppers. You can mount the grid stoppers on the small terminal strip next to the tube socket, and use the socket lugs instead of the terminal strip to tie the driver tube cathode leads to the power tube grid leads.
I think I understand, but I would love for you to take a glance at this schematic I pieced together using rather crude methods and a pencil, your schematic, the Root Schematic, and MHartman's Layout... With preference to Your schematic and the MHartman Layout for all component values. I'd like make sure I'm getting things right electrically before I finalize my own adapted layout.

Questions:
A) Did I incorporate it into the Schematic properly they way you said?
B) Is this correct for B+ supplies. Basically, the 6L6s still get their old B+2 supply?
C) This is the same Filter Section from Hartman. Should anything be adjusted because it is fed from the Bridge Rectifier instead of a FWR?
D) What is the function of the 1uF bypass cap on a switch by the NFB? (Found in the Root Schematic that I left in)
E) Is there any advantage to using a DPDT Standby switch on the HT Supply rather than the old ground lift method with a SPDT?
F) Did I do anything incredibly stupid?

Thanks so much!

Edited: I forgot the word "because" in question C). I was wondering if Bridge and full wave rectification require the same type of filtering after, or if one type is more difficult to smooth.
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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

bcmatt wrote:A) Did I incorporate it into the Schematic properly they way you said?
Yes. The cathode resistors don't need to be 3W, though. Half-watt will do fine since the idle current is only about 1.4mA.
bcmatt wrote:B) Is this correct for B+ supplies. Basically, the 6L6s still get their old B+2 supply?
Yes.
bcmatt wrote:C) This is the same Filter Section from Hartman. Should anything be adjusted it is fed from the Bridge Rectifier instead of a FWR?
No.
bcmatt wrote:D) What is the function of the 1uF bypass cap on a switch by the NFB? (Found in the Root Schematic that I left in)
It's an all-or-nothing presence.
bcmatt wrote:E) Is there any advantage to using a DPDT Standby switch on the HT Supply rather than the old ground lift method with a SPDT?
Yes. As shown the switch is switching AC, which will reduce arcing, and since it's double-pole there is no high voltage present on the rectifiers when it is on standby.
bcmatt wrote:F) Did I do anything incredibly stupid?
Nope.
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bcmatt
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Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

Thanks Martin!
I will draw up my modded layout next. It may seem like I'm stalling, but I am stuck on much of this since I am still waiting for these parts. They arrive at "Package Express" in Sumas Washington fairly quickly. But then my parents will go pick up the packages when they are near the border (about once a week or so). Then they will be passed off from my parents to my wife's parents when they drive through their city on their way up here in a couple weeks for a visit (about a 14 hour drive).
This isn't my usual scheme for saving on shipping expenses, but they are coming soon, so why not? I saved about $15-$20 for shipping per package this way. It doesn't seem that big of a deal until you think about the fact that each is equal in cost to the actual contents of the package.

So, if you guys are ever tempted to move to Canada (for various non-political reasons like the availability of vintage Traynors), think twice about the fact you are giving up cheap shipping from amp parts suppliers.
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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

I don't mean to spoil your fun, but here's how I would fit the new power supply and driver circuit into Hartman's layout.

Edit: A little cosmetic tweaking.
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bcmatt
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Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

martin manning wrote:I don't mean to spoil your fun, but here's how I would fit the new power supply and driver circuit into Hartman's layout.
Thanks!
This is more fun to me. I wasn't sure exactly what sort of methods I was about to use to make my own uglier layout. It may have ended up being pencil like the Fender layouts from the 40s and 50s. You would be appalled at my aversion to using tech if I told you what my job is. What program do you use to draw these up? My more recent editings were done in the Mac preview program. :shock:
I may still make an altered layout to accommodate the fact that two of my preamp tubes are at the front panel.
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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

bcmatt wrote:What program do you use to draw these up?
I'm working on a Mac using PowerPoint, plus Grab for clips if needed.
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Re: EL34 YGL3 -> 6L6 SSS

Post by glasman »

martin manning wrote:The inductor in the filter section doesn't seem to have any effect, at least as it's shown in the schematics posted here.
I even tried modelling it with Spice and came up with nothing. So I built the circuit with an approximate inductor, still nada.

Fling it, doesn't need it.
Located in the St Croix River Valley- Afton, MN
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bcmatt
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Re: EL34 YGL3 -> 6L6 SSS

Post by bcmatt »

glasman wrote:
martin manning wrote:The inductor in the filter section doesn't seem to have any effect, at least as it's shown in the schematics posted here.
I even tried modelling it with Spice and came up with nothing. So I built the circuit with an approximate inductor, still nada.

Fling it, doesn't need it.
OK, you guys convinced me. I am no longer tempted to try the inductor at all. Any suggestions on how to use a couple extra front panel DPDTs or a switch and a pot?
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martin manning
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Re: EL34 YGL3 -> 6L6 SSS

Post by martin manning »

You could arrange a defeat of the preamp NFB, one or both loops, by shorting across the 100R resistors at the cathodes of V1a and V1b. I don't know if this would be useful or not, but it would probably put some hair on the tone. Really I'd just build to the schematic first, then play around with it.
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Re: EL34 YGL3 -> 6L6 SSS

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It's been slowing going. Summer has been busy. We went on holidays up to the Yukon, and I had the rest of my parts waiting there for me.
I'm finally home and sort of get little pieces of a day off here and there to make some progress.
I wired up the extra transformer on a board with both sets of rectifiers that I need. All the bigger voltages caps will go off to the right. I think I will silicone the 2x 220 uF ones to the chassis and all the 22s will go on the main board.

My next step will be to mount my choke and reverb transformer to the chassis.
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