Six Year SSE Project Nearing Completion

[woodo]

I did notice that it was several seconds before the dim bulb started to glow...

I use a 5ar4 as well and i notice about a slight delay before everything charges up compared to the 5u4g.

Good to see everything turned out well. Enjoy the music!

 

[Duke58]

Most people want that slight delay- it's supposed to be better for the life of the tubes.

 

[dwinstonwood]

Thanks woodo!

Thanks Duke58. Then everything is functioning as designed!

I'm getting ready to take voltage readings here soon. I'll post the numbers.

The Tung-Sol datasheet for the EL34B's that I'm using state a maximum plate dissipation of 25 watts.

I am currently using 680 ohm resistors. If I'm near 25 watts should I swap up to 750 ohm, or 820 ohm resistors?

Thanks!

 

[Duke58]

I'm like Tubelab- if they're not red plating, run em.

 

[Richard Ellis]

Congrats on your SSE build, looks as good as it sounds huh? With those bright blue Edcors, finding a knob with a touch of matching blue color was a masterstroke.


---------------------------------------------------------------------Rick......................

 

[dwinstonwood]

Thanks Richard Ellis! Yep, when I saw that knob on eBay I bought it on the spot! Haha.

We really have to hand it to George. I've never built an amp before in my life, ss or tube. He seems to have designed it so that it will simply work right when someone like me builds it.

Here are my numbers:

Remember Tung-Sol states the maximum dissipation for the EL34B is 25 watts.

Plate voltage - 457V

Right Cathode - 34.5V
680 OHM resistor
50MA
21.124 watts

Left Cathode - 34.6V
680 OHM resistor
50MA
21.12 watts

I'd say that's spot on.

 

[cogitech]

As close to perfect as you can get!

This thread, like a few others, has been very inspirational to me as I build my SSE. Thanks for posting!

 

[dwinstonwood]

Thanks cogitech, I'm looking forward to seeing your finished amp!

But I did an incredibly stupid thing when I first measured the voltages...

I was nervous and I forgot to attach the dummy loads.

Well, the amp was only on for a few minutes total with no signal, and nothing was hurt, but I was really mad at myself.

Then, I figured having a load on the OPT's would most likely alter the power tube voltages to some degree (although, I have no understanding how or why). So, I measured them again. There was a slight difference:

In my previous post I should have said B+ voltage, not plate. So, these figures are still not accurate - a bit high - because they're calculated using B+ not plate voltage (I don't know how to measure the plate voltage).

With 8 OHM load: B+ - 454V

Right Cathode - 34.2V
680 OHM resistor
50MA
20.99 watts

Left Cathode - 34.3V
680 OHM resistor
50MA
20.985 watts

So, with speakers attached the amp is running even more conservatively.

 

[Tubelab_com]

The minor differences between your two sets of measurements are likely due to power line voltage changes since your B+ reading is changing.

If there is zero signal, operating an amp without a load will have no affect on voltage readings, nor cause any damage. It's still a good idea to have a load attached to any tube amp whenever it's turned on since some amps that use GNFB can go unstable and oscillate without a load.

I don't know how to measure the plate voltage

Using your meter place the black lead on ground as if you were going to measure B+. With no signal applied, touch the red lead to the plate pin of each output tube. It's pin 3 on the tube socket, or the plate terminal of the OPT connector. It's normal to find a few volts of difference between the two tubes.

Subtract the cathode voltage from the plate voltage, then multiply by the current to get the actual total tube dissipation. 1 to 2 watts will go through the screen grid, so your plate actual dissipation is slightly lower than the total tube dissipation.

 

[dwinstonwood]

Thank you George. You cleared up quite a bit.

And, your design really sounds remarkable.

Then, my actual plate dissipation is below 20 watts meaning I'm running the EL34's in the neighborhood of 70% - 75% of max. That's reassuring.

 

[Mr_Zenith]

Congratulations on a fine job! Six years, eh? To tell the truth, if you stay in any hobby for long enough you're bound to accumulate a few abandoned projects, or at least a few half-finished efforts that you'll keep telling yourself you'll "get around to" someday. I'm glad your SSE wasn't one of those.

I'm with Nigel on the patience thing. I built a Tubelab SE-II last year and had it up and running breadboard-style (read "keep away from children and small animals") within six hours of receiving the board in the mail. That's not a boast, but a sad indication of my impatience.

Your chassis work is excellent, by the way. Nothing wrong with a Hammond box, especially if the execution is well-planned like yours. And the wooden "cheeks" are a nice addition, too. Good thing you were able to get it done before we all had to go into hiding!

 

[dwinstonwood]

Thank you for the kind comments Mr_Zenith!

Throughout several moves, I've always safeguarded this project as I was determined to complete it "one day." Now, I'm really glad I kept the board and parts safe all these years and finally committed to finishing it! It's a fantastic amp.

My real "money pit" hobby is designing and building radio control airplanes (the balsa wood kind, covered with Japanese silk and nitrate dope). So, I had a background in planning and building things when I took on the SSE. It was not having any experience working with tube circuits and lethal voltages that was most intimidating. I really could not have done this project without the DiyAudio community.

Now, I'm already researching a phono preamp project. A lot to choose from there. The Tavish Vintage 6SL7 is an interesting PCB-based tube project with documentation.

 

[colnago55]

Now, I'm already researching a phono preamp project. A lot to choose from there. The Tavish Vintage 6SL7 is an interesting PCB-based tube project with documentation.

I've built two Tavish's and I love them. One for myself and one for my son. One is paired with TSE, the other with an SPP. I really like the sound and the flexibility. Scott at Tavish was very helpful as well.

Enjoy,

 

[dwinstonwood]

Thanks colnago55! You wouldn't happen to still have your BoM, would you?

I spent an hour or so this morning converting the Tavish PDF BoM into a Word doc, importing that into an XL spreadsheet, and then uploading that to Mouser.

But, there're a lot of parts that Mouser either didn't have, or couldn't read, from my spreadsheet. I can always finish working on it a little at a time until it's done. Then, I would have a file that I could share with people here.

Thanks,
David

 

[Mmcaleer]

David, I was just going to start a post to ask the same question. I am going to start a SSE build and was looking for a BOM myself. Let me know what you find. Maybe we could start a new thread to build an updated BOM.

 

[Tubelab_com]

If you guys come up with a proposed BOM, post it here, or email it to me. I'll go over it and make a thread like the TSE-II thread where the current BOM stays in the first post, since I have the ability to edit it.

To be honest I haven't built an SSE in nearly 10 years. I have three that work and several boards in various states of disarray since they have been used for numerous experiments.

 

[spiggs]

I just put in an order to Mouser for an SSE build. Attached is my list. I have it saved as a project in Mouser as well and will update as required if a Mouser project link is desired. Oh and heads up George, my money order for one SSE should be hitting your mailbox soon.

 

[dwinstonwood]

Mmcaleer, do you mean a BoM for the Tavish phono preamp, of the SSE?

I will look at my old SSE Mouser orders and see what's there and what's missing. I also bought parts from other suppliers, too.

 

[Mmcaleer]

Mmcaleer, do you mean a BoM for the Tavish phono preamp, of the SSE?

I will look at my old SSE Mouser orders and see what's there and what's missing. I also bought parts from other suppliers, too.

BoM for the SSE

 

[dwinstonwood]

This was my first amp build, so I had to buy almost everything, including a Hakko FX888D, solder-sucker, clip-on test leads, hole cutting bits, wire and various bits of hardware, etc.

I think I bought all of the electronic components from Mouser, except for the coupling caps, transformers, volume pot, tubes, tube sockets, and chassis. Those I bought from four of five different places.

This amp is absolutely worth the investment in time and money. And, now I have pretty much all of the tools I'll need for my next project...

David