SP 12 SE

[Skratch]

Yes, From the gap clockwise

 

[soundude]

lee, the 47k should be at input to ground or system negative if isolated from chassis, remove 47k and install pot, wiper to input and either of the outer taps to ground and set pot for 47k at input to ground then connect record player turn on and play record thru system and adjust pot for best sound and then disconnect and turn off preamp and take resistance reading across pot connections and thats the resistance you replace the 47k with.

 

[mlucitt]

Johnny, yes the schematics of my Phase Linear 2000 preamp show a 47K resistor (R1-Right and R8-Left) between the input to the first amplifier section and ground. What is the effect if the resistance is too low, distortion? If too high, muddy sound? I realize it might be hard to describe but some of us have our best hearing at Mach 8, not at some low-level phono input...

 

[laatsch55]

Still; dealing with hum.Have a different freq with phono selected than say....CD.Got the tt out and setting up. I haven't set a TT up in 30 years.

 

[soundude]

to low will sacrifice gain, to high youll lose bottom, what you are doing is you are matching the cartridge load to the resistance of the input stage..but you will hear a huge difference, the highs get brighter, bottom more solid...back in a earlier forum I attached a link for the radiotrons handbook 4th edition and it covers ever possible area of audio, even has a complex math section.. here it is again for anyone intrested. http://headfonz.rutgers.edu/RDH4/
you won't need mach 8 for the best sound then..

 

[laatsch55]

Getting a we bit crowded down here.

 

[laatsch55]

F%$# F^^%$ F**^%^ I have HUM all through my system regardless what is being used from the 3300 Ser II to the Spec F%%$#@# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[mlucitt]

Lee, do you have access to a signal tracer? I have one called "The Tracer 77A" It has two parts, a signal injector and an "Inductive Amplifier 200B" If you hook up the tracer to a circuit or wire, the inductive amplifier can pick up the signal in a different location in the circuit or downstream in the wire. Maybe you could use that to identify the source of the hum.

If you cannot find one, I'll send mine to ya.

 

[soundude]

lee, try decoupling the heater supply and or the power supply with a coupling cap B+dc to chassis ground. Also big problem with tube gear is loops, try isolating, lifting, the amp or preamp house ground, third prong.
If not and you have no grounding plug on recepticals ground the record player ground wire to house ground or radiator. Try this too, put your fingers near the tubes and if the hum gets louder you have heater to cathode float leakage, usually cured with coupler across cathode resistor or a 50 resistor from heater connection to ground, this is normally used with ac powered filaments, but try it with the dc, only thing you can lose is hum..

 

[soundude]

really simple to find source of hum, short the inputs of source and or phono if the hum goes away its rf in the circuit, if phono stage could be grounding of player, if it doesnt go away its in the powersupply.

 

[laatsch55]

Johhny, thank you for putting that so succinctly. Thed majority of the hum was in the 700B in the rack. Changed over to the Spec 2 and the noise floor is like a black hole again. There is still some in the pre, but I'm done F^%$%^& with it tonight. Just gonna kick back and listen to tunes and terrorize you, Joe, Mark, Larry, the other white Mark, Jer, Shit----who elsae???

 

[laatsch55]

OK , I'm gettin there. Decoupled the B+ supply, decoupled the phono rca's in, decoupled the filament - to chassis. The hum dropped A LOT!! Not gone altogether, but enough that I was DAMN impressed with what tubes could do to a voice. And there were some subtle things that are hard to explain, like maybe SS is TOO FAST sometimes to catch the subtle things?? I don't know fellers, threw my world in a tube tizzy. It sounded really good on some Younger Brother----"Vaccine"" DAMN good. Maybe I have finally been exposed to some of that tubemagic eh??

 

[speakerman1]

OK , I'm gettin there. Decoupled the B+ supply, decoupled the phono rca's in, decoupled the filament - to chassis. The hum dropped A LOT!! Not gone altogether, but enough that I was DAMN impressed with what tubes could do to a voice. And there were some subtle things that are hard to explain, like maybe SS is TOO FAST sometimes to catch the subtle things?? I don't know fellers, threw my world in a tube tizzy. It sounded really good on some Younger Brother----"Vaccine"" DAMN good. Maybe I have finally been exposed to some of that tubemagic eh??

To me the SS has an edginess. I don't need 3000 watts though. I'm going to send the Teslas. Have a shipment going out today. You can use the TT I sent I think it has a Shure on it. I think. It is set up If I remember right. Am sending you a link for the manual. It is hard to explain the weight.
http://www.musichallaudio.com/product_f ... manual.pdf

I run the weight at 1.5 grams. Do you need anything else? I have a question. I may have missed it. Can we put a pot in place of the resistor so it can be dialed in without soldering? Or has that been said? Is there a blue or red cart on it. Teslas are packed. Coming your way.

Larry

 

[laatsch55]

I'll have to check Larrt. There was a totally separate one in another box. I'll check on em. I can sety the resistor before it goes if we have the same cart.

 

[speakerman1]

I'll have to check Larrt. There was a totally separate one in another box. I'll check on em. I can sety the resistor before it goes if we have the same cart.

Separate ones what. LOL

 

[laatsch55]

Cartridges

 

[speakerman1]

OK LOL

Larry

 

[soundude]

Actually if you can get a good tracking pot you can leave in preamp for future adjustments of cartridges or use for different genre of music...some records are recorded dull and lose the highend and you can use the pot to dial in your sound.. or find the perfect setting and install fixed resistor.
Lee those cleartops could be the source try moving them between sockets..
did you get any hum when you put your fingers around the tubes?
you can also couple the system ground of the board to the chassis...
One thing I try, is you can use a jumper from the preamp chassis to the amp chassis to create a ground unity, warn you though could work in reverse and add hum, but if it goes silent you narrowed it down to circuit loop. keep the other components in incase you roll amps.
Something I love too do with different types of music...
Lee b careful tubes are very addicting and could change you outlook about SS, tubes are more subtle and softer than SS...its actually the feedback and the third harmonics that give the tubes there sweetness. Tubes also produce a purer ac waveform because tube conduction is always flowing and thru a output transformer, which creates a perfect ac wave, transistors which switch on and off which causes noise and corners in the waveform and large amount of feedback is needed to overcome this. This is how I learned it and understood it, but bet Joe can explain better...

 

[laatsch55]

John they don't hum when I run my fingers over them. The 12's yes they are getting more microphonic by the day. What's up with that?

 

[speakerman1]

2 6922 teslas are on their way. Have you ever used a trace pen? I think I have some NOS Clear tops.

Will look at a later date. LOL Are the 12AU7s?

Larry