SET amp owners thread

[DasguteOhr]

First impressions are WOW! Om my VOTT the SQ is just on another level compared to the SS amps. The room is huge and the separation of the instruments/voices is simply fantastic. The only issues is the transformer hum that is clearly auditable as the 817 are extremely sensitive… but I guess that’s the nature of zero FB design!?

mechanical humming at the transformer can be heard with your ears or humming only through speakers?

 

[Norway]

mechanical humming at the transformer can be heard with your ears or humming only through speakers?

Speakers only. Hum noice is not affected by the attenuators.

 

[morricab]

First impressions are WOW! Om my VOTT the SQ is just on another level compared to the SS amps. The room is huge and the separation of the instruments/voices is simply fantastic. The only issues is the transformer hum that is clearly auditable as the 817 are extremely sensitive… but I guess that’s the nature of zero FB design!?

Congrats but no, hum is not inevitable. I am also not surprised by your wow…I would be shocked if SS was better on your speakers

 

[Salectric]

With a DC filament supply, there shouldn’t be any appreciable hum heard through the speakers. I would suspect a ground loop with your power cords. Try using a cheater plug that bypasses the earth connection and see if the hum disappears. If it does, then you have a ground loop.

I have noticed that with new amplifiers as well as new power cords there may be a ground loop hum initially but it goes away in a couple days.

If it is a ground loop hum and it does not go away, there are three options. You can use the cheater plugs all the time (not recommended for safety reasons); you can have a tech install a 10 ohm buffer resistor between the amp electrical ground and the amp chassis; or you just live with the hum.

 

[Norway]

With a DC filament supply, there shouldn’t be any appreciable hum heard through the speakers. I would suspect a ground loop with your power cords. Try using a cheater plug that bypasses the earth connection and see if the hum disappears. If it does, then you have a ground loop.

I have noticed that with new amplifiers as well as new power cords there may be a ground loop hum initially but it goes away in a couple days.

If it is a ground loop hum and it does not go away, there are three options. You can use the cheater plugs all the time (not recommended for safety reasons); you can have a tech install a 10 ohm buffer resistor between the amp electrical ground and the amp chassis; or you just live with the hum.

Thanks for your comforting reply. I’ll give it a go tomorrow and try out your suggestions.

 

[christensenleif@msn.com]

You heard no hum in my place
Try gnd lifting AC on the amps

 

[Norway]

You heard no hum in my place
Try gnd lifting AC on the amps

I’ll get rid of the hum before you come to my place! And that’s a promise.

 

[acousticsguru]

With a DC filament supply, there shouldn’t be any appreciable hum heard through the speakers. I would suspect a ground loop with your power cords. Try using a cheater plug that bypasses the earth connection and see if the hum disappears. If it does, then you have a ground loop.

I have noticed that with new amplifiers as well as new power cords there may be a ground loop hum initially but it goes away in a couple days.

If it is a ground loop hum and it does not go away, there are three options. You can use the cheater plugs all the time (not recommended for safety reasons); you can have a tech install a 10 ohm buffer resistor between the amp electrical ground and the amp chassis; or you just live with the hum.

Any reason why ground loops would disappear after a couple of days?

Greetings from Switzerland, David.

 

[DasguteOhr]

Speakers only. Hum noice is not affected by the attenuators.

ok put the amplifier upright on its side then remove the base. then switch on and wait 10 minutes until everything stabilizes. regulate with a potentiometer to the lowest hum. please follow the "one hand rule". only touching the amplifier with one hand saves your life in case of carelessness.
there are many causes for hum can be terribly annoying. mostly different grounding concepts of devices. but try the above first.

 

[Atmasphere]

Any reason why ground loops would disappear after a couple of days?

Greetings from Switzerland, David.

None whatsoever.

 

[Ampexed]

Could be power supply buzz which is difficult to get rid of.

 

[Salectric]

Any reason why ground loops would disappear after a couple of days?

Greetings from Switzerland, David.

The only reason I can think of is the earth wiring has to break in. Even as I write that, I realize it doesn’t make much sense from an electrical theory perspective, but I can’t think of any other reason.

The best example of this was with a new pair of Virtual Dynamics David II power cords. When I first hooked them up to my mono block tube amps, there was an obvious hum from both speakers. It wasn’t
enough to interfere with listening but was annoying nonetheless because the amps had been dead silent with my old power cords. Over the next couple days, the hum became less and less and after 5 or 6 days the amps were back to dead quiet.

That wasn’t the end of the story for the VD power cords though. A couple years later I reconnected the VD cords after being in the closet for a few months. Once again there was hum but in a day or two it was gone completely.

The VD David cords were odd ducks since they had magnets inside the plugs at each end. Maybe these were a factor.

 

[morricab]

Any reason why ground loops would disappear after a couple of days?

Greetings from Switzerland, David.

You just stop noticing?
When I had ground loop issues in the past they never went away on their own.

 

[microstrip]

According to the Stereophile review the amplifier had some grounding problems. In order to diagnose I would suggest powering it on without input cables but fitted with short circuited RCA plugs. Do you still have hum in such conditions?

 

[Salectric]

Well, here’s another example. A year ago I moved to a new house and there was a slight hum when I set up the system. Same equipment that had no hum in the old house. A week later, without any changes in the system, the hum had disappeared. I can only surmise the wiring in the wall and outlets and the electrical box itself, all of which was brand new, went through some break in as the equipment was used. Everything was then dead quiet just as it was in the old house, and it has remained so ever since.

 

[cal3713]

First impressions are WOW! Om my VOTT the SQ is just on another level compared to the SS amps. The room is huge and the separation of the instruments/voices is simply fantastic. The only issues is the transformer hum that is clearly auditable as the 817 are extremely sensitive… but I guess that’s the nature of zero FB design!?

Sorry, what were you using before for amplification? Congrats on getting your beautiful Altecs on a circuit they were designed for and being rewarded for it!

 

[SVS]

The volume control has no effect on hum, so shorting the inputs will not eliminate it. It is most likely that the cause of the hum is poor filtering of the voltage of the heaters. Low-sensitivity speakers can't hear it, but high-sensitivity makes it noticeable.
It is possible to eliminate this by adding large-capacity electrolytic capacitors to the filter of the power supply unit of the 211 tube heaters.

 

[Norway]

ok put the amplifier upright on its side then remove the base. then switch on and wait 10 minutes until everything stabilizes. regulate with a potentiometer to the lowest hum. please follow the "one hand rule". only touching the amplifier with one hand saves your life in case of carelessness.
there are many causes for hum can be terribly annoying. mostly different grounding concepts of devices. but try the above first.

Ok! But if you don’t see any more posts from me here it didn’t work for me…

 

[Norway]

Problem sort of solved… I connected til ATM 211 to my Perlisten S7t(92-93 db sensitive) and you have to be within 1 m.(3ft) for the hum to be of any issue.

 

[christensenleif@msn.com]

you call that solved!?