Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Seduction => Topic started by: jamestw on January 28, 2011, 04:46:26 AM
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Hey Guys,
I'm a newbie and this is my first time post here. I have my first time to build a kit - the Seduction just completed this Tuesday.
It's my first DIY project, so I did it very carefully followed the kit building guide and the WWA website - thanks for these two very detailed instructions, It was a lot fun during the building.
After built, I got some problems and have back to check 4~5 times these days, but still can not figure out what caused the problem ! I'm hitched here, hope if anyone could guide me to solve these problems...
Sorry for my English language ability is not so good (I'm in Taiwan), I try to express these issues as detailed as I can :
(1)
I've done the resistance checks, I got figures from terminals, as follow :
- All 0 ohm and "*" terminals are same as kit manual suggested.
- Terminal 17, 19, 22, 24 are not in the ranges (lower) the kit manual suggested.
- I can not get the figures from A3,B3 and A8,B8 ,my DVM only can test voltage below 2Meg ohm, these four terminals shown far higher resistances than my DVM can read.
Terminal / Resistance
input jacks / 47.7K (R & L)
17 / 160.4
19 / 170.5
22 / 151.3
24 / 161.2
26 / 995K
36 / 997K~1001K
A2,B2 / 1002K,1000K
A3,B3 / out of reading.
A7,B7 / 47.9K,48K
A8,B8 / out of reading.
output jacks / 476K (R & L, the L were reading 0 ohm at first time, has corrected later.)
(2)
The voltage checks from terminals, as follow :
* My country main power supply is 110V/60hz, I got a stable power 113V from wall. Not sure if this will be a factor, the power transformer come with kit is PT-1.
- The 0VDC terminals are same as kit manual suggested.
- I got far lower voltages from T12, T15, T25, T34, T44.
- Unbalanced voltages on T27,T37 & T29,T39 & T30,T40 & A1,B1 & A6,B6
Terminal / Voltage
6 / 6.0 vdc
9 / 5.3 vdc
12 / 89.2 vdc
15 / 116 vdc
25 / 143.5 vdc
27,37 / 65.2, 87.6 vdc
29,39 / 61.1, 82.2 vdc
30,40 / 60.7, 81.4 vdc
34,44 / 89.2, 89.1 vdc
A1,B1 / 63.7, 85.6 vdc
A3,B3 / 1.5, 1.5 vdc
A5,B5 / 5.3, 5.3 vdc
A6,B6 / 64.6 85.5 vdc
A8,B8 / 1.5, 1.5 vdc
(3)
I built the Seduction directly with C4S upgraded (skipped the original four 18K plate load resistors) and changed 4 caps to M-cap SIO, two for 0.1uf interstage caps, two for 0.47uf output caps, these M-caps all are 1200vdc as I can buy conveniently from local.
When the first time I powered up my Seduction - I still remember how I was so exciting at that time - two 6922EH tubes slowly glow up, then all leds lighted (yes, 8 leds lighted !). However, after about 1 minute or so, a led died.
Then I noticed , on C4S board, two leds have weaker light then the other one.
But, the 4 leds on two tube sockets look all are normal.
(4)
After that, I checked again all the terminals and found the L output jack was shorted by extra solder !
I fixed the L oupt jack, and powered up Seduction again, all leds started to light... then, again, the same one led on C4S board, died again (and it never back again). There remained total 7 leds kept lighting.
(5)
Next day I checked again all the components, connections, and done the resistance, voltages checks, I can not find where's wrong, the figures from checking are same as before (except the L output jack, now it's fixed.).
Powered it up again, this time the second led one C4S board died, now I got two leds no light, the are two closed to 2N2907 and MJE350 transistors on C4S.
I connected Seduction with turntable and preamp, there is only R channel sounded, the L channel does no any sound.
I kept check the constructing and want to figure out, till now, the problem still there.
I'm thinking, maybe I should go back to original Seduction constructing, disassemble the C4S and put four 18K plate load resistors on ? But before do this, I really want to know where is the problem now in my Seduction.
A lot appreciate, any suggestion could guide me fix the problem.
Please help, thank you guys.
james
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Ok, you should post the expected voltage or resistance reading next to the actual reading. There is no need to post anything that is 15% high/low as that is the tolerance expected with varying input voltages. With yours expect slightly low readings. But the +/- 15% still applies.
Since you have sound from the right channel you only need to post the left channel readings that are out of the expected range.
The immediate thing I see is you put in the C4S and you will not get the proper resistance readings through the dead (no voltage on them) boards. So A & B 1 & 3 can not be measured for resistance.
Don't disassemble it till you make a few checks first.
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Thanks, Grainger,
So now only the left channel I have voltage readings that out of +/- 15% ranges as follow :
T37 / 70 vdc ... I got 87.6 vdc
T39 / 70 vdc ... I got 82.2 vdc
T40 / 70 vdc ... I got 81.4 vdc
B1 / 70 vdc ... I got 85.6 vdc
B6 / 70 vdc ... I got 85.5 vdc
Though the right channel does sound, but the T12/135vdc that I got only 89vdc that is far lower, is it OK ?
I'll back to do more checking.
james.
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... also attached a photo.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F2.jpg&hash=2c1d4488110a1cadb9143f7480707d66b4ca12ad)
james
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Ok, if T12 is good and every thing attached to the left channel plates (T37, T39, T40, B1 & B9) is high what reading are you getting at B3 & B8? You had posted 1.5V DC. Is this still right? Do the LEDs on those terminals light up?
Everything you listed is the left channel after the plate load C4S circuits. Are the LEDs on the C4S board on the left channel out?
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Hi James,
It is possible that one or two of the 2N2907 transistor metal cans are touching a PC board trace. You might check for that and if it looks like the problem, try reheating the solder pads that the transistor is soldered to and lifting it up from the PC board a tiny bit. That PC board is one of our very early designs (we have been selling that kit for something like 10 or 11 years now!) and that has been an occasional problem.
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... from another view.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F3.jpg&hash=a3fb912b8d8e8bdb24b9f2a89e1d8ac6723ff2fd)
james
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That is nice and very neat work.
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Thanks, Grainger,
Are these two died leds on C4S at photo that indicate the left channel ?
I was try to see the underside of C4S board, but can not for sure, unless I disassemble the board.
james
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Thanks, Dan,
I'll do these to lift 2N2907 transistors up a little bit.
I did a similar thing as you suggestion but I focused on two died leds that I though they might have their tiny silver plates underside are shorting two trace holes, as two holes for led's leads are so closed.
So I've lifted two leds up a little, though, the problem are not on leds obviously.
james
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James,
There are two LEDs on the C4S board for the left channel and two on the tube socket for the left channel. Your pictures don't show but 2 of the 4 LEDs on the C4S board lighted. I expect those would be for the working right channel. In the first picture I think can see all four LEDs on the tube sockets lighted.
If you have 1.5V on both tube socket's pins 3 and both tube socket's pins 8 then the problem is most likely on the C4S board. That board must be passing some current for the left channel's tube socket LEDs to be lighted. But the problem is on the board.
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Actually it appears that one LED is out in each channel. I think you have two different problems - one is that the LEDs aren't lighting which means the C4S loads are not working right - the other is that there is some problem in the left channel around the RCA jacks or left channel tube socket that is blocking the signal.
For the LED problem, start by unplugging the preamp from AC mains and lifting up the C4S PC board from its nylon standoffs and rotate the PC board so that you can use your ohm meter to test resistance between each pair of the three solder pads that each transistor is soldered into. There should be no readings lower than about 1000 ohms. If you find any reading under 100 ohms that transistor may be blown. Sometimes the 2N2907 can blow if it touches that copper trace under it.
To find the problem with the left channel, start with the easy things. First swap the tubes between the sockets and see if the problem follows a tube. If the tubes are OK (I think they are OK, because your voltage readings are not perfect, but they do show that the tubes are drawing current and lighting the LEDs on the tube sockets), then with the Seduction switched off and unplugged from AC mains take your ohm meter and measure the resistance between the center pin of each RCA jack and the outer shell of the same RCA jack. The output jacks should read about 470K ohms and the input jacks should read about 47K ohms. If any read around 0 ohms there is another shorted jack like the one you already found, that needs to be fixed. If the RCA jacks are all OK, then carefully check the wiring of the resistor and capacitors on the terminal strips to make sure they are all on the correct terminal and no solder joints were missed.
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I agree with the value of swapping tubes to see if the problem moves, which would confirm my theory:
I think the main problem is the low power line voltage, and consequently the low heater voltage. See if you can find a low value resistor, in the range 0.39 to 0.68 ohms and rated 1 watt; place that resistor in parallel with the 1.2 ohm resistor in the power supply (T6 to T9). This should raise the heater voltage (T9, A5, B5) into the range 5.7vDC to 6.0vDC. You can adjust the value of this resistor if it seems to be too large or too small.
The low heater voltage makes the cathode too cold and unable to produce enough electrons, so the plate voltage rises. The plate voltage is the same as the power supply voltage (around 89v) on two triodes, so the C4S does not have enough compliance and that extinguishes the LEDs. The power supply voltage is high enough at first, before the tubes begin to conduct, but then the tube current pulls the power supply voltage down.
Another problem is that the power supply voltage drops too much between terminals 25 and 15. There should be a 1000 ohm resistor between those two points. Either that resistor is too big it should be easy to measure), or something is shunting extra current to ground at T15. There is a resistor of 270K in parallel with a capacitor of 220uF, both from T15 to ground (T14). Make sure the capacitor is oriented correctly (negative terminal with the stripe on the side goes to T14) first. If that is correct, then see if the resistor is 270K ohms. You may be able to measure the resistance T15 to ground if you leave the meter connected for a long enough time; you may have to measure it in both directions (the diodes can cause a false reading), or you may have to disconnect the resistor at one end to get an accurate measurement.
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Yes Grainger,
Four leds on two tube sockets are lighted, and A3, B3, A8, B8 voltage readings all are 1.5v.
Looks I have to lift C4S board and check it...
Thanks Dan,
I'll go for C4S board checking first.
Switching tubes on both sockets that I've done few days ago, but it not make difference that still only right channel sounded, left channel keep quiet. I did not measure voltages after tubes switched, I'll do it again and check the readings.
Both input RCA jack resistance readings are 47.7K, and both output jack readings are 476K. They are OK.
Yes Paul,
Both power supply voltages really bother me, they are low and I don't know how to do them...
Thanks for the tips, I'll check and try to fix them.
Thank you guys, if without you I don't know how to start to do with these problems
I'm going to do these ways, will report the results later :-)
james
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Another problem is that the power supply voltage drops too much between terminals 25 and 15. There should be a 1000 ohm resistor between those two points. Either that resistor is too big it should be easy to measure), or something is shunting extra current to ground at T15.
There is a resistor of 270K in parallel with a capacitor of 220uF, both from T15 to ground (T14). Make sure the capacitor is oriented correctly (negative terminal with the stripe on the side goes to T14) first. If that is correct, then see if the resistor is 270K ohms. You may be able to measure the resistance T15 to ground if you leave the meter connected for a long enough time; you may have to measure it in both directions (the diodes can cause a false reading), or you may have to disconnect the resistor at one end to get an accurate measurement.
Okay, Paul,
T25 & T15, and T12 & T15, both have a 1001 ohm resistor reading I just measured there.
The 220uf cap orientation is correct on T14 & T15 with " - " connect on T14.
I clipped " - " of meter to chassis ground post and "+" on T15 of 270K resistor it parallel with 220uf cap, the reading started from about -360K, to -100K, to 0 K, resistance getting rise and slower and slower, took about 18 minutes the reading stopped and stayed on 278K.
I guess it's OK :-)
I'm going to inspect the next...
james
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Okay, I have done some checking now :
Tubes swapping.
Same as before, only right channel sounded, the left channel does no sound.
Voltage checks after tubs swapping.
- First I noticed a difference is one led on C4S board it back to light, but two leds are lighted weaker than the other one. It just same as before, I took a photo attached.
- The voltage readings have some difference :
(Terminal/Voltage)...(VDC before tubes swapping)...(VDC after tubes swapping)
(T12/135 vdc)...(89.2)...(94.6)
(T15/148 vdc)...(116)...(119.4)
(T25/160 vdc)...(143.5)...(142.3)
(T27,T37 / 70 vdc)...(65.2 , 87.6)...(69.3 , 85.1)
(T29,T39 / 70 vdc)...(61.1 , 82.2)...(65.2 , 87.1)
(T30,T40 / 70 vdc)...(60.7 , 81.4)...(64.4 , 86.2)
(A1,B1 / 70 vdc)...(63.7 , 85.6)...(67.1 , 63.5)
(A6,B6 / 70 vdc)...(64.6 , 85.5)...(68.5 , 90.2)
A5, B5 are 5.3 vdc, same as before.
A3, B3, A8, B8 all are 1.5 vdc, same as before.
Do these readings mean the tubes difference ?
I'm going to lift up the C4S board now...
james
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F5.jpg&hash=b233e09e2c35a6c7ddd32d0a1b5cb73182af3496)
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Hmm, it is strange that the voltage drop from T25 to T15 and T15 to T12 are each about two times what they should be, which seems to mean that the preamp is drawing too much current. It is probably best to try to solve this puzzle by changing one component at a time.
I would start with Paul's idea of adding a resistor in parallel to the one from T6 to T9, and see if that brings the heater voltage up to at least 5.7 volts DC. If it does go up to the proper range, then remeasure the voltages at T25, T15 and T12 to see if they have changed.
By the way your pictures are very helpful and your workmanship is really superb!
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OK, some more speculation:
The power supply voltage drops about 48v from T25 to T12; it should drop half that much. Therefor something is drawing too much current.
The LEDs at the tube sockets glow correctly and the tubes are all biased properly, but B6 is always too high a voltage (also T37, T39, and T40 - all of which are connected to B6).
From these numbers, it seems likely that the C4S is trying to feed too much current to B6 (through T37). There are four resistors of 237 ohms on the C4S board, and one of them determines the current sent to B6. Perhaps that resistor is shorted on the board, or the wrong value?
There is still something odd at B1; it is the only value that changed a lot when the tubes were swapped. That suggests a bad contact, either a solder problem or a mechanical one. But B1 seems to be acceptable after the swap.
I still think it is important to increase the heater voltage.
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I checked the C4S last night, and fond a problem... Dan was right. There have two 2N2907 transistors metal cans shorted with PC board trace, and with the ohm meter check transistor's solder pads, the readings are too low, only 3.5 and 11.5 ohm.
Thanks Dan, you are amazing ! You actually pointed the problem at very first time.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F6.jpg&hash=894879775d68c42e1b33f37d561906e7f4435fd2)
I pulled out four 2N2907 transistors, two of them got extra solder residues underneath... the problem was here.
Took solder residues off and lifted all 2N2907 transistors up, solder them to C4S again, and check them with meter - this time the readings looks unify - from 771~776 ohms for four transistors.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F7.jpg&hash=c1fd400d88c3ece1f4b62795e1db88bcf346e37e)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F8.jpg&hash=0e2586a4241b233bb67445bb18468f10771f966a)
Reinstalled C4S board to Seduction, This time 4 leds on board are lighting properly.
I did again the Voltage checks, got new readings as follow :
(Terminal/Voltage)...(New vdc reading)
(T6/6.5 vdc)...(6.0)
(T9/6.0 vdc)...(5.3)
(T12/135 vdc)...(115.5)
(T15/148 vdc)...(132.4)
(T25/160 vdc)...(149.8)
(T27,T37 / 70 vdc)...(68.2 , 64.7)
(T29,T39 / 70 vdc)...(64 , 60.6)
(T30,T40 / 70 vdc)...(63.4 , 60)
(T34,T44 / 135 vdc)...(114.6 , 114.4)
(A1,B1 / 70 vdc)...(67.4 , 64)
(A3,B3 / 1.6 vdc)...(1.5 , 1.5)
(A5,B5 / 6.0 vdc)...(5.2, 5.2)
(A6,B6 / 70 vdc)...(67.5 , 63.9)
(A8,B8 / 1.6 vdc)...(1.5 , 1.5)
Connected the Seduction with TT , I have BOTH channels sounded now :-) ... soooooo HAPPY !
Also many thanks to Grainger and Paul, you guys are kind enough guide me the ways for checking problems, they are thoughtfully.
Hi Paul,
The next step, I'm going to find resistors to parallel with 1.2 ohm resistor in the power supply (T6 to T9) to bring heater voltage up. Are the 0.39 to 0.68 ohms value to add that still efficient ?
I'll report the result later...
james
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.bikedomeworks.tw%2Febay%2520images%2F9.jpg&hash=875644e56532eaf79432fde1e402a798356b9fe9)
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I listened about 3 sides of records with Seduction, Somehow it's not balance for left and right channels.
The right channel is louder about 3db than left channel.
How can I fix this problem ?
james
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Hi James,
Glad you found the problem. Try swapping the tubes again and see if that helps the balance problem. Also, balance may improve as the tubes get around 20-50 hours of use.
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Thanks Dan,
Swapping the tubes did work, the balance improved after tubs swapped. The right channel now about 1db louder.
All parts are still in break-in, I think they will improve further more later.
james
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I think the main problem is the low power line voltage, and consequently the low heater voltage. See if you can find a low value resistor, in the range 0.39 to 0.68 ohms and rated 1 watt; place that resistor in parallel with the 1.2 ohm resistor in the power supply (T6 to T9). This should raise the heater voltage (T9, A5, B5) into the range 5.7vDC to 6.0vDC. You can adjust the value of this resistor if it seems to be too large or too small.
I can only find a 0.5 ohm 2W resistor from local, its value within in suggested range but I'm not sure 2W is OK ?
After put it parelled with 1.2 ohm resistor (T6 - T9), that did work.
Now I got the heater reading both 6.1 vdc on A5, B5. (before they were only 5.2 vdc).
but the other readings on tube sockets are lower than before, especially the plate voltages A1,B1 and A6,B6 .the B1, B6 just lower than -15% tolerance of 70vdc ... Is there something wrong ?
Voltage checks :
(Terminal/Voltage)...(vdc reading Before add parelle resistor)...(vdc reading After add parelle resistor)
(T6/6.5 vdc)...(6.0)...(6.48)
(T9/6.0 vdc)...(5.3)...(6.1)
(T12/135 vdc)...(115.5)...(116.3)
(T15/148 vdc)...(132.4)...(132.8)
(T25/160 vdc)...(149.8)...(150)
(T27,T37 / 70 vdc)...(68.2 , 64.7)...(62.8 , 59.5)
(T29,T39 / 70 vdc)...(64 , 60.6)...(58.8 , 55.8)
(T30,T40 / 70 vdc)...(63.4 , 60)...(58.4 , 55.3)
(T34,T44 / 135 vdc)...(114.6 , 114.4)...(116 , 115.8)
(A1,B1 / 70 vdc)...(67.4 , 64)...(62.3, 58.7)
(A3,B3 / 1.6 vdc)...(1.5 , 1.5)...(1.5 , 1.5)
(A5,B5 / 6.0 vdc)...(5.2, 5.2)...(6.1 , 6.1)
(A6,B6 / 70 vdc)...(67.5 , 63.9)...(62.5 , 59)
(A8,B8 / 1.6 vdc)...(1.5 , 1.5)...(1.5 , 1.5)
james
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Excellent!
2 watts is better than 1 watt, so that value is just fine - I should have said "1 watt or greater". The voltage of 6.1v is very good - my design intention was to run the tubes at 6.0, with an acceptable range of 5.7 to 6.3v.
The tubes are able to conduct more current when the cathode is properly heated, which pulls the plate voltage down a bit - that's why those voltages have dropped. It is actually a good sign, and it's not uncommon for the plate voltages to drop to 55-60 volts. It's not a problem.
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James,
Are you up and running yet?
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Hi Grainger,
I just back from the long Chinese Lunar New Year holiday, I was out of town last week can not get access to internet easy ...
I have ran the Seduction with my TT (Micro Seiki DQX1000) and Yamaha RX-V661 receiver which is an integrated amp has its build-in MM input which is not a bad build-in MM stage, so I have compared RX-V661 stock MM stage with Seduction... And I have a confidence to say the Seduction is totally superior than RX-V661 build-in MM stage, in everywhere.
Till now, my Seduction only ran about 15 hours, but I can tell it did has difference sounding everyday when I played records - in good way.
It's hard to me to explain how its difference each time I listened records with Seduction, It had a R&L channel balance issue that I reported last week, but now both channels have balanced sound as 6922EH tubes and all the parts of Seduction has break-in 10 more hours.
Now I just put Seduction on rack at convenience, I'll settle down it at a proper position on the rack in next few days, and will post some photos here.
I got a serious hum problem at first two days after connected the Seduction to Micro and Yamaha system, not surprised to me, which I has expected, and I tried/played the grounding in many ways from tonearms (two tonearms on Micro TT), TT, SUT, to Seduction, then to Yamaha amp... Finally I have an extra jump wire connect from ground post of Seduction to the metal frame of rack, it does work, it calm down the hum very well :-)
I know the hum is still there when I crank Yamaha volume up to 0db the hum and noise from speakers loudly I can hear, But, it does not bother me now, because at my normal listening level (Yamaha's volume at -30db~-40db) I can not hear any hum or noise, even put my ears close next to speaker drivers, I can only hear a dead quiet :-)
BTW, the volume control range of my Yamaha RX-V661 amp is from -80db to +15db and it drive a pair of very sensitive JBL 3622N horn speakers --- 101db, 4ohm --- I guess this also is a factor that I can still hear hum and noise from speaker when the volume crank to 0db.
Besides, I think my Seduction has not be completed well yet, as I left full length of leads of M-cap SIO cap soldered to connections of Section, I was thinking that I might change to other caps later... But now, I think I will cut the M-cap leads as short as possible and resolder them again, in this way might can reduce hum and noise further more.
I'm happy with my Seduction, now with my first 10 more hours listening it does sound much more clear and show me every details from my records - if compare to my Yamaha build-in MM stage.
The bass is more tight, clear and with textures in there - this is very important to me. (and please note, Yamaha's 'Natural Sound' tech make the bass sounded well already, this amp is not a cheap shit, to compare with my other system, Mcintosh C100 pre + MC352 amp that I can not tell which one sounded better than the other, I love them both.) - But the Seduction make the bass a lot better I've heard.
Since I did not use the stock caps in Seduction, two 0.1uf in interstages and two 0.47uf in outputs, I put M-cap SIO in there directly. I can not tell if the M-caps make Seduction sounds so smoothly or improved more smooth sounding ? I can only say the sound is soooooo smooth, plus, a deeper dimension - Compare to the Yamaha build-in MM stage of course.
I did build my Seduction followed the steps from Wonderful World of Audio website, and of course the excellent building guide from kit, thanks to you guys --- I have a lot of fun with this stuff.
james
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Hi Paul,
Since you guided me to add a parallel resistor on heater power supply brought up voltage to 6.1vdc. I'm wondering if I could do the same way to add a parallel resistor to high voltage power supply (T15/T12 , or T25/T15 , or somewhere ?) to increase the C4S voltage and two plates voltage ?
I know you've mentioned several times, the lower plate voltage is not a problem. But, does the higher plate voltage can offer more gain (or μ) ?
If so, the higher plate voltage will increase noise or other disadvantages ?
... sorry, if this is a stupid question :-) , I'm in learning these tube's knowledges.
Thanks,
james
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James,
Dispersed comments below. Man, sounds like you are almost there.
. . . And I have a confidence to say the Seduction is totally superior than RX-V661 build-in MM stage, in everywhere.
I
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... I'm wondering if I could do the same way to add a parallel resistor to high voltage power supply (T15/T12 , or T25/T15 , or somewhere ?) to increase the C4S voltage and two plates voltage ?...
You have the C4S, which isolates each triode from the power supply. As long as the power supply voltage is at least 10 volts greater than the plate voltages, raising the supply voltage will have no effect at all.
If you had used the resistor loads, you would want to get the voltage up. But changing the resistors in the power supply would provide less hum filtering, which would not be a satisfactory solution. You'd have to replace at least on of the resistors with a filter choke; in that case you'd also have to find a suitable location and orientation for the choke to prevent it from picking up magnetic-field hum. It's easier, less expensive, and sounds better to use the C4S loads.
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Next we will lead you through some tweaks, but the hum first.
That will be good, I'm interesting to know what tweaks I can do on Seduction.
Good move. Is the rack itself grounded? Maybe it is acting like a shield, it is hard to say. The MC lead to the SUT and from SUT is as important as any cable routing in your system. Keep them short, especially the MC cartridge to SUT, and away from transformers (except the SUT). Sounds like you are now getting an acceptable noise level.
Oh, the rack does not ground itself. It just a common 'L' shape rack that can easy buy from hardware stores, each L shape frame has many punched holes so you can adjust each level's height as you want, add more beams and you get more levels. These frames-beams made by steel with paint coating. This kind of rack has a strong construction once it be assembled, normally it can take 300 kgs or more without any problem.
The M-Caps need 100 hours of break in at the minimum. Paul Joppa, designer of the Seduction, has suggested for breaking in you can feed a CD player