3 preamps with transformer hum, DC on the line?

Jea48, thanks again for the info. Here are the preamp's specs:

Output imp: < 20
Power consumption: 6.5 watts
Max output voltage: 3.8 v

With the above specs, is there a cheaper EI power supply I can try? Or maybe I can put my amp on the same EI supply. The power amp consumes 850 watts. Would the one you found be powerful enough for both the preamp and amp?

Yesterday I tried exactly what you stated by ONLY having the preamp plugged in to the dedicated 20 amp AV line with no other AV equipment powered up on the same line and all the other breakers off in the main fuse box. So, power was cut off to every breaker except the dedicated AV line and the only thing powered up in my entire house was the preamp. Still hums.

So, I took the case off the preamp today and tightened all power supply screws (none really budged). Powered it up with every breaker turned off except my dedicated 20 amp AV line and only the preamp plugged into the dedicated outlet. Still hums - grrrr.

It looks like I have very few options, some which I cannot afford and 1 I really am not sure I want to do:

1. Send back to Audio Plus Services (Seattle to NY). Anyone had any experience with this shop and their service dept? I can see a $250 diagnosis bill plus shipping both ways and them coming back saying there is either nothing wrong with it or they are unable to fix it. Really not sure about this route. Probably a No.

2. A custom or 3rd party power supply is probably out of the question after looking at various wires coming off the factory power supply. No.

3. Trying a PS Audio or similar power regenerator. Too expesive. No.

4. Going to an integrated amp if I can find an Audio Refinement Alpha Complete in black that does not hum in 8/10 shape I just might do it. I've heard it is a good unit but not as good as my Audio Refinement separates, especially the Pre 5. A Maybe.

5. Trying my best to get the power company come out and test the line. Hopefully something that is easily addressable and I can actually get the power company to show up and test the line and do it for free (I do pay them for a resource with hopefully some kind of service level agreement backing it.

6. Going to try a Environmental Potentials DigiPlug Stationary in series before my Porter Port on my dedicated 20 amp line. They will do a 30 day refund trial and I can do the wiring myself. A Yes and hope it fixes things.

What I really don't get is that all 3 preamps I've tried do hum and got better with using the PS Audio Humbuster, but again, I lost the high frequencies so the PS Audio Humbuster is out. If it is that common of a problem, why is there not more of an industrial standard that avoids this problem. On top of that, the Linn Classik K music (integrated amp with tuner and CD player) just cranks away with no hum but does not sound as good as my current Audio Refinement gear and probably loses out to the Audio Refinement Complete Alpha integrated also.

Things that annoy you with their hum...

BTW, the Linn Classik is part of my bedroom system with some Tukans and is not on a dedicated line and I have quite a few dimmers in the house.

I finally replaced the power supply in my preamp with another Pre 5 that was in rough shape but had a quiet transformer. The swap worked great and I now have no DC hum. I sold the custom DC blocker but have a PS Audio Humbuster III for sale if anyone is interested.

Jea48 and everyone else, I appreciate the answers and ideas. Yes, it is a toroidal transformer. Usually YBA, which made the Audio Refinement line does not use toroidal ones but they did for this line. And I think the Linn Classik does use an EI.

I had all the grounds checked when I bought the house in 2010. House was built around 2004 and, yes it is quite a new and large housing development with a business park or two down the road and a retail strip mall village at the entrance of the development.

Jea48, do you know of any plug and play 120v in to 120v out EI transformers that would have decent wattage, good to excellent quality and not break the bank? Or maybe a high quality EI transformer that I could add a plug on the in wires and a outlet for the out wires plus a nice box?

So I am going to try an isolation transformer. I found one of the two new (returnable if it does not solve my problem):

- Tripp Lite IS1000 in black (1000W) for preamp only
- Tripp Lite IS1800HG (1800W hospital grade in off-white) looks like it is just under the 2000W rating Jea48 recommends for preamp and amp

I am going to check around Seattle today to see if someone has the IS1000 in stock. Hopefully this works and gives me some more evidence to use if I can ever get the power company to come out and test my line.

If the IS1000 does not work for eliminating the hum in my preamp, it looks like it will have to go in for repair. Does anyone have any good repair shops besides Audio Plus Services?

Again, TIA everyone,

Scott

Found the following locally:

Tenma 450 VA Isolation Transformer, Isolated Outlet (2): 450 VA Continuous, 550 VA Intermittent, Direct Outlets (2): 900 VA, Isolation Leakage: <0.1 mA, Dimensions: (W x H x D) 6 x 5 x 9 , Weight: 16 lbs, Power Requirements: 120 VAC, 60 Hz

Going to give it a try for just the preamp. Fingers crossed.

Scott

The isolation transformer (a Tripp Lite IS350) did not change anything. I think I will just live the minor hum. I cannot hear it from my listening position and only hear it when changing records. Would be nice to have it be quiet but we cannot have everything perfect, especially when it is not a necessity.

Thanks everyone

I returned the isolation transformer within the 30 day return window, which was easy after buying it locally.

I might try ordering the parts my own humbuster / dc filter and have one of the two local audio service shops do the assembly. Can someone give me a schematic of the simplest proven design (side by side caps on either the live XOR neutral feed with diodes on each side?) and a high quality parts list that I would need? Should I go with the Bryston, the Crown or a simpler design? It would be great if that parts list included a nice black outer metal case / box if possible plus high quality IEC female connector. I would hope to be able to use one of Porter's power ports also.

Jea48, have you done something like this before? I saw a similar thread post by Gbart that he / she has made some of these for Audiogon members, but I am unable to email that user.

Please drop me an email if possible: white 78 911 at hotmail dot com

TIA again!

Gbart, I sent a reply with some questions. Thanks,

Scott