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The text above is a follow-up to ...
I hope the lytics aren't sour...the Tono is new. Switching the Tono polarity with a three to two adapter didn't make any difference in the hum, by the way.
Thanks for your input on this (annoying) situation with the speaker hum.
Bob Sasso
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Hi again,
OK. The hum is from the tube preamp. Someone suggested a switch box between the preamp and amps to get the preamp out of the circuit when not in use. I am concerned however about signal degradation going through a switch box . (I have sprung for some nice interconnect cables to avoid that problem). Are there any high quality switch boxes made that I can use, or am I better served by NOT putting anything in the path between preamp and amp.
Thanks a lot,
Bob Sasso-------------------------------------------
The text above is a follow-up to ...
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Thanks so much for the info on the speaker hum. So, if a three to two adapter works in eliminating the hum by inverting the power cord, is it ok to just leave the set up like that? Assuming it works, is it really necessary to rewire the transformer of the Tono?
Thanks again for your expertise,
Bob Sasso
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Followup To
Question -
Hi,
Here is my set up: Tono line stage tube preamp, Jolida JD100 tube CD player, Vandersteen 2Ci speakers. This is all powered by 8 Marantz monoblocks MA-500, bridged to make four monoblocks to biamp and biwire the two speakers.
Here is the problem: I want to leave the amps on all the time. If I turn off the preamp, there is a VERY loud hum out of both speakers...turn the preamp back on, no hum. Do you know what is happening and how to fix it? I used these monoblocks in the past in a home theater system with a 7 channel Lexicon processor...the amps were on all the time, and no hum when the processor was off.
Thanks so much,
Bob Sasso
Answer -
First, that is a nice system. The Marantz blocks are really good sounding amplifiers. The Vandersteens are good; they sound even better if you sandbag them (Hang some heavy weights on the back so they are rock solid for bass projection; or if you don't mind, place a heavy object of about 100 lbs on the top to hold it down tight to the floor. You will be amazed at the improvement in bass performance).
The hum is from the output of the tube preamp; when it goes off the outputs are still coupled to the power line through the transformer in the power supply.
Just to verify, turn off the amps to verify this, then just pull the output cables from the back of the preamp. Now, when you turn the blocks ON there should be no hum with the preamp ON or OFF. Right?
That will prove the hum is from the preamp internal grounding or transformer pass through.
I think you may be able to eliminate this problem by reversing the power cord of the tube preamp unit. You may have to get one of these little electrical plugs from the hardware store that has a three to two prong adaption (and they usually have a little pigtail ground wire hanging out the side). But, see if that does not solve the hum problem.
It could also be an inverted power cord on one of the amps or even the cd player, but since you did not have the problem in your previous Lexicon setup, it is likely the Tono unit that is the intercepter.
If this solves the hum problem, you might ask the Tono people to rewire (they are handmade) the transformer winding by inverting either the primary or secondary section. (Or they may have an alternate idea for it).
Let me know how I can help further,
Cleggsan
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With some designs the 3 prong power plug is required to meet the UL or safety certifications. So, it is just a safety code requirement.
In other designs the transformer and ground system is isolated and a balanced power line is okey and the reversing of the polarity makes no difference.
So, let me know if it works AND if the power cord on the tube preamp is a two pronger, it should not be a problem at all.
Cleggsan
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I am beginning to wonder if the hum is coming from WITHIN the Tono line stage tube preamp! That is entirely possible if the filter Lytics have gone sour. In which case you will have to replace them.
A good audio repair shop can easily test for hum on the outputs of the audio left and right; if so, replacing the power supply electrolytics are not expensive and are not hard to replace - and will not effect the sound quality.
I don't recommend the switchbox you mentioned; they are always troublesome and can bring in more hum in a system like yours.
AnswerThen, maybe you are back to the switch box. You can set up a box such that it merely disonnects the outputs of the Tono preamp when not in use. In other words, just pass the signal through the box; when switched off it interrupts the signal. Perhaps that will work.
But, I am still not satisfied the system is wired correctly (including signal wiring and power wiring). If the products are designed correctly you should not have a hum problem. Have you tried connecting a ground line from the preamp chassis to the amp chassis? Or, still better, grounding each chassis to earth ground. And what happens when the preamp audio leads are connected but the preamp is unplugged from power?
Maybe do a little more experiementing with the ground situation.
Cleggsan
