Please Help for my Seduction problem.

[jamestw]

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


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[Doc B.]

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!

[Paul Joppa]

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.

[jamestw]

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.
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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.
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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.

(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
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[jamestw]

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

[Doc B.]

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.

[jamestw]

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

[jamestw]

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.
(T25/160 vdc)...(149....(150)

(T27,T37 / 70 vdc)...(68.2 , 64.7)...(62.8 , 59.5)
(T29,T39 / 70 vdc)...(64 , 60.6)...(58.8 , 55.
(T30,T40 / 70 vdc)...(63.4 , 60)...(58.4 , 55.3)
(T34,T44 / 135 vdc)...(114.6 , 114.4)...(116 , 115.

(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

[Paul Joppa]

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.

[Grainger49]

James,

Are you up and running yet?

[jamestw]

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

[jamestw]

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

[Grainger49]

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

[Paul Joppa]

... 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.

[jamestw]

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