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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 27th May 2020, 10:16 PM   #1
RDL_AK is offline RDL_AK  United States
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Default Some questions about mods made to SSE

I purchased an assembled SSE on an online auction site. I knew it had the led mod for the 12AT7. But once receiving the board, checked the SSE for correct parts, and found some differences. I contacted seller, he had no clue. Evidently an estate sale. I am wondering if the differences relate to the led mod. So before connecting power to the SSE I am looking for info/advice on what the changes will do.

Changes:

LEDs instead of C10,C20 & R10,R20?

R12,R16,R22,R26 220 ohm installed instead of 100 ohm?

R13,23 470 ohm installed instead of 330 ohm?

R2 220K ohm 2 Watt installed instead of 150K ohm 3 Watt?

R4 330K ohm 2 Watt installed instead of 150K ohm 2 Watt?

R3 22K ohm 2 Watt installed instead of 10k ohm 1 Watt?

R17,R27 500 ohm 5 Watt instead of default 560 ohm 5 Watt?

Simple_SE_Amp_Sch_11-08.jpg

SSE1.jpg

SSE2.jpg

SSE3.jpg

SSE4.jpg

Last edited by RDL_AK; 28th May 2020 at 12:43 AM. Reason: Text
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Old 27th May 2020, 10:49 PM   #2
stereo71 is offline stereo71  United States
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This should be interesting...it looks like this board was never attached to any external parts; no wiring connected...an unfinished project. But what was the intent of the component changes? Very strange...
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Old 27th May 2020, 11:41 PM   #3
Mr_Zenith is offline Mr_Zenith  United States
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Some questions about mods made to SSE
None of that makes any sense to me, either - but then again I'm not an EE. The good thing is that it doesn't look like anything was permanently altered, so it should be relatively simple to return it to "stock" condition if that's what you want. R17 and R27 are the output tube cathode resistors used to create bias. They probably differ from those shown in the schematic because a different tube was chosen per the chart on the Tubelab site (either that or the builder wanted a "hotter" operating point). R2 is the bleeder resistor for C1; the lower dissipation could be more problematic than the actual value depending on the current. R3/R4 create a voltage divider to elevate the tube heaters, but I'm uncertain about the significance of the change. Since their ratios are about the same, the difference in the elevated voltage shouldn't change much if at all.
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Last edited by Mr_Zenith; 28th May 2020 at 12:04 AM.
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Old 27th May 2020, 11:54 PM   #4
RDL_AK is offline RDL_AK  United States
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"it looks like this board was never attached to any external parts; no wiring connected...an unfinished project"

That is what I thought too. but once receiving board and closely examining the solder pads the transformers had lightly and very cleanly tack on. I do not want to desolder the components for no reason and put it back to original design. So wanting learn more about the affects of these changed resistors and LEDs.
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Old 28th May 2020, 12:18 AM   #5
RDL_AK is offline RDL_AK  United States
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For more info I also was able to buy the power transformer for this SSE from same seller. So I will attach pic of specs if this helps. The seller also listed output EDCOR GXSE15-5K-8 that I did not win sold for more than new from edcor!
Attached Images
File Type: jpg Power Transformer.jpg (157.8 KB, 104 views)
File Type: png gxse15-5k.png (103.6 KB, 101 views)
File Type: png gxse15-5k-8.png (21.0 KB, 99 views)
Attached Files
File Type: pdf EDB273BX.pdf (238.9 KB, 2 views)
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Old 28th May 2020, 12:30 AM   #6
RDL_AK is offline RDL_AK  United States
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"R17 and R27 are the output tube cathode resistors used to create bias. They probably differ from those shown in the schematic because a different tube was chosen per the chart on the Tubelab site (either that or the builder wanted a "hotter" operating point). R2 is the bleeder resistor for C1; the lower dissipation could be more problematic than the actual value depending on the current. R3/R4 create a voltage divider to elevate the tube heaters, but I'm uncertain about the significance of the change. Since their ratios are about the same, the difference in the elevated voltage shouldn't change much if at all."

Thanks Mr Zenith good feedback. The R2 bleeder issue had my attention too. But I do not understand exactly how lowering the current flow in the bleeder affects the circuit. The changed resistors around the 12AT7 and 10M45 I do not understand why and how this will affect the circuit.

Last edited by RDL_AK; 28th May 2020 at 12:38 AM. Reason: Text
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Old 28th May 2020, 02:01 AM   #7
RDL_AK is offline RDL_AK  United States
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"They probably differ from those shown in the schematic because a different tube was chosen per the chart on the Tubelab site (either that or the builder wanted a "hotter" operating point)"

MR Zenith, from looking at chart I speculate an EL34 at 400V, 5k Z output.

EL34 400 5000 387 34 510 66 24 4.86 7 0.4 4.39
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Old 28th May 2020, 02:08 AM   #8
Tubelab_com is offline Tubelab_com  United States
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That is an old board from before the legal issue that forced the name change to SSE.

None of these mods should prevent the board from operating. One of two things could be going on here.

1) The builder had many of these parts on hand and used what he had that was close in the places where it doesn't matter much. The power transformer is from 2003, before the SSE existed.

2) The builder purposely chose parts for a lower current and voltage operating point that most builders use. The power transformer is 700 VCT where most builders use 750 VCT. The B+ will be in the 400 volt range. This makes sense with the 500 ohm cathode resistors.

The other changes won't matter much except for the 470 ohm current set resistors for the CCS chips. This will result in about 5 mA of current through the 12AT7, which may be OK with the LED. I can't read any numbers off the CCS chips, they may be mosfets instead of IXYS chips. This was done mostly in Europe where IXYS chips were not available, but there were shortages of those part in the USA too early on. It's also possible that the builder intended to use something other than a 12AT7 tube.

I would go ahead and power it up. Check the plate voltage on the 12AT7 before installing output tubes. It should be around 200 volts.
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Old 28th May 2020, 02:48 AM   #9
RDL_AK is offline RDL_AK  United States
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"I can't read any numbers off the CCS chips"

The numbers are:

CP10M45S
IXYS K736
K0737M2

Thanks Mr Tubelab nothing like getting feedback from the designer in nearly real time! I have built several of your designs but always from stock. They all work and sound great. I saw this assembled and cheaper than parts to fill the board so I bid and won it!

With this being IXYS and I am going to use 12AT7 should I change to the 330 ohm precision resistor? Thank-YOU for sharing your passion with us all!!!
Attached Images
File Type: jpg Simple_SE_Amp_Sch_11-08 Changes Values.jpg (254.8 KB, 57 views)

Last edited by RDL_AK; 28th May 2020 at 02:58 AM. Reason: Attached image and Text
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Old 28th May 2020, 03:19 AM   #10
RDL_AK is offline RDL_AK  United States
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"This will result in about 5 mA of current through the 12AT7, which may be OK with the LED."

"I would go ahead and power it up. Check the plate voltage on the 12AT7 before installing output tubes. It should be around 200 volts."

Took a few minutes for me to realize you already answered my question.
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