Seduction And Reduction Tube Equivalents

[Paul Joppa]

The 6ES8 is a "semi-remote cutoff" tube, meaning the gain is highly variable depending on the current. It is built that way so that the gain can be automatically adjusted for different radio stations. In audio, that means it is nonlinear as all get-out. It's not suitable for audio. In Seduction, it will also not have anywhere near enough gain.

This tube is often listed, and sometimes sold, as a 6DJ8 equivalent - this is either a product of ignorance or fraud. My opinion of course.

[Dobs]

Seduction runs the heaters at 5.7 to 6.0 volts, which gives the "longer life and lower noise" effect. Running a 7DJ8 that low will give very long life and no noise at all - but no sound either of course; the heaters will be too cold to function!

It's the problem i have with 6N1P tube in my Seduction, some work and some dont.

[Grainger49]

The 6N1P draws twice the heater current than Seduction was designed for.  The Seduction transformer will burn out after a while using them.  But they are good sounding tubes and were used in the design stage as reported by PJ.

If you want to run the 6N1P, then buy a transformer that will give you double the current for the heaters and put a 500k ohm resistor to ground where the 1M ohm resistor is after the interstage coupling cap and before the grid stopper 220 ohm resistor.  After getting a higher current transformer in there you might need to adjust the voltage on the heaters by changing the series resistor in the heater supply.  This is also according to PJ.

[Dobs]

The 6N1P draws twice the heater current than Seduction was designed for.  The Seduction transformer will burn out after a while using them.  But they are good sounding tubes and were used in the design stage as reported by PJ.

I hope i didnt damaged too much my transformer because im using 6N1P for about 2 years now with around 800h of play.

If you want to run the 6N1P, then buy a transformer that will give you double the current for the heaters and put a 500k ohm resistor to ground where the 1M ohm resistor is after the interstage coupling cap and before the grid stopper 220 ohm resistor.  After getting a higher current transformer in there you might need to adjust the voltage on the heaters by changing the series resistor in the heater supply.  This is also according to PJ.

Can you guide me to get a good transformer? And also give me more details on the parts to get and the way to locate them. I have build my Seduction 4 or 5 years ago and i dont have anymore documentation about it.

Thanks again,

[Paul Joppa]

I have not yet found a good alternative - in fact, we developed the PT-1 because there were no really suitable transformers even for the 6822 version.

The simplest approach would be to run the 6N1P on AC heater power, bypassing the rectifiers entirely and grounding one side of the winding. This will reduce the RMS current to within spec. There is risk of hum, but there are various inexpensive ways to improve that. I've posted this for years but I don't remember anyone having tried it.

The next simplest approach would be to replace the heater power supply with a 6vDC external supply, as many people did with the original Foreplay years ago. It should be rated for 1.2 amps or greater.  These are usually the kind that have a small box to plug into the power outlet, the so-called "wall wart". Caution - some of these are fine, some are junk, and it's hard to tell which is which!

[Grainger49]

The specs I just read say each tube draws 600mA +/-50mA.  So on the outside that is 1.3A.  Give your self some room to rectify and filter the heaters.  Get at least 1.5A 6.3V transformer (Hammond 166L6).  You can use a three pin regulator chip and trim up the voltage to exactly what you want.  For that you should get a 1.5-2.0A 8V transformer (Hammond 166L8).

[Dobs]

Wich way is best?

Can i install the transformer into the Seduction without compromising the sound with electrical noise.

[Dobs]

The specs I just read say each tube draws 600mA +/-50mA.  So on the outside that is 1.3A.  Give your self some room to rectify and filter the heaters.  Get at least 1.5A 6.3V transformer (Hammond 166L6).  You can use a three pin regulator chip and trim up the voltage to exactly what you want.  For that you should get a 1.5-2.0A 8V transformer (Hammond 166L8).

On the spec i saw the hammond give 2a at 6.3v I assume its 6.3vdc? When you say 3 pins regulator chip you mean variable resistor?

[Grainger49]

Transformers produce AC so if you want to go with DC you have to use either a full wave bridge or four diodes arranged in a bridge, some capacitors and a resistor to smooth the rectified AC.

The three pin regulator is a good way to go for smooth and noise free DC.  (you still need everything mentioned above)

This part is an adjustable voltage regulator but with 5 pins (I couldn't find a three pin regulator):

http://www.mouser.com/ProductDetail/Sharp-Microelectronics/PQ070XH02ZPH/?qs=sGAEpiMZZMsGz1a6aV8DcJFN%252bbTDeMTjFe%2f59o4dkoI%3d

Edit: this transformer would have to be out of the Seduction chassis or it will hum.

It has 10V maximum input, 2A maximum current and is adjustable from 1.5 to 7 volts.

[Paul Joppa]

There are two problems with the Hammond transformers suggested, both of which mean that they will generate excessive magnetic hum fields and cannot be placed near the Seduction. (Without testing, I would guess that a minimum 12 inch distance would be adequate - but not in the same box!)

The first problem is a lack of magnetic headroom; the second is having the windings separated into two different bays of the bobbin. Note that the PT-1 runs 70-80 percent as much magnetic induction as the Hammonds, and still needs both a copper shield and a molyperm shield tape. This greatly increases the cost of this transformer and - you know Bottlehead - we would not do that unless we had to! My second attempt at a good phono preamp power transformer is the PT-5 in the Eros; it does not need the shield tapes but is much larger, so no cost savings there.

Our experience developing the Seduction - one of our earlier products - is what convinced us that we should use custom power transformers in all our products, designed for low-noise audio applications.

[Dobs]

I thought the Hammond was to be used as a stand alone supply for the heater only instead of a cheapo wall wart type, right?

[Grainger49]

An outboard power supply is indicated for this application.  It is not that hard to do.

[Doc B.]

I hope i didnt damaged too much my transformer because im using 6N1P for about 2 years now with around 800h of play.

Actually I would say that you have proven that the PT-1 can be run way over spec and handle it pretty well. I'm not condoning this, as it could be that the transformer might fail for some one else running in this same condition of overload. But if it's already been running for two years for you without incident I wouldn't really expect a catastrophic failure...just don't ask us for warranty coverage if it goes. Strikes me that a simpler solution than changing the power supply is to go back to the tubes it was designed to work with.

[Dobs]

Transformers produce AC so if you want to go with DC you have to use either a full wave bridge or four diodes, some capacitors and a resistor to smooth the rectified AC.

The three pin regulator is a good way to go for smooth and noise free DC.  (you still need everything mentioned above)

I will go that way if DC is better then AC.

Can you make a small plan and part list to do this with the regulator and how to proceed for the voltage adjustment in the final stage.

Thanks again,

[Dobs]

Yes, no, maybe?