[WGH]

Oh boy, I can see myself getting into a lot of trouble for this.

My AVA amp started out in August 2008 as an an Insight 440 and since then it has been sent back twice, once for the Insight+ 440 Double upgrade and the second time to turn the amp into a Synergy 450. I don't know when the transformer developed a slight hum, maybe it was always there, maybe not. My old house was noisy and the amp was in an adjoining room so I never noticed. Now my new house is quiet as a tomb, super insulated with Marvin Integrity windows (highly recommended) and the hum is noticeable. Not loud but once you notice it, it is always there. Yes it is plugged into a dedicated circuit with AVA's Humbuster but I figure some transformers hum, some don't.

So why not try a little additional damping? My shop always has interesting stuff hanging around so I put together a damping kit. Years ago when computers were much noisier I made sound absorbing sheets using leftover wall carpet from one job and cork, it worked extremely well quieting an old computer. The cork-carpet sheets were made using my vacuum bag veneer press and yellow glue and are well bonded together.


The carpet is Ozite Champion made from Olefin with a flammability rating of Class A - ASTM E-84 which means it has 25% or less flammability than red oak. The transformer never even gets warm so I'm not concerned but it is good to know I'm not building an incendiary device.

The black disk is a solid surface counter top material like Corian, very non-resonant.



The hum is quieted by at least half and quite acceptable now, never loud to begin with but now I have to get real close to hear it.

But now I'm wondering if I'm delusional because the Synergy amp sounds clearer, separation between speakers is more defined and center image is more focused. I have enough material to make a few more kits if anyone wants to try this out but I don't want anyone to void their warranty if Frank thinks this is a bad idea.

Wayne

[Wayner]

I think this is a bad idea, as the toroidal transformer's main surface to dissipate heat is on the top, which you have now insulated. The result is a rise in internal core temperature, perhaps putting the amplifier into an unsafe operating mode. I also think this may remove any warranty left on the amp, because of the modification.

I suggest undoing it, and calling Frank for another option, before you have a problem (like a fire).

Wayner

[rollo]

    Agree with Wayner here. There are numerous products to use to isolate the trannie. If is a HUM issue then Franks Hum Buster is for you. If it is resonance the most affective method we recco is 3/8" th. Ebony. Ebony pencil blanks are VG to try. Used as rails under trannie.
     Have fun trying.



charles

[WGH]

I have run the amp this way for a couple of days with the cover off to see if there was any heat issue and the transformer has stayed consistently cool. In your experience do transformers in AVA amps get too hot to touch during normal or hard running operation?

Rollo - as mentioned in the first post a Humbuster is already in use but thanks for the additional ideas. I'm thinking of a ventilated wheel which damps the outer edge with the center open for cooling.

[avahifi]

I suspect your toroid power transformer has a slightly loose internal winding in its big coil wound core and that is vibrating slightly causing your hum.

In general that power transformer won't ever get hot unless the amp is run at near sustained full power continuously.

Thus I suspect your damping plate cure is just fine.  The other cure would be to replace the power transformer which we will do at no charge if you want to return the amp to us for this service.

If you do decide to return it for a transformer transplant, remove your pad and stuff and clamp the transformer down tight so it won't move in shipment.

Regards,

Frank Van Alstine

[Wayner]

What? Apparently anyone can modify their Van Alstine stuff to suit themselves any way they want.

Unbelievable..........

[avahifi]

Wayne, normally our big power transformers just sit there at room temperature.  Note that one "normal" mounting practice is to clamp the transformer between a big flexable mounting pad on the bottom and another on the top with a big metal dish on top of that with the big bolt through the middle holding the whole works in place.  Even units coming back here after 20 years of service show no excess transformer heating. The only power transformer we have used that runs warm is the original Dyna ST-70 power transformer.  That has been resolved long ago by using either the Dynakitparts or Triode replacements that bump up the current capability by 50%.

No, I absolutely do not want end users to do whatever they want to try home remedies in dealing with some issue with our electronics, but in this case I can't forsee any serious issues.  Of course with the metal cover in place about the worst that could happen would be an internal meltdown and a lot of stink in the house.  But we have never seen that happen either.

One nice thing about having an infrared thermometer in house is that now we measure the heat from everything in our equipment.  It is a great design helper and also useful in troubleshooting.  Just point the laser at the device you want to measure, squeeze the trigger and look at the readout.

Frank

[Wayner]

Whatever.

[WGH]

Thanks Frank, it's good to know a humming transformer, even though working perfectly, is covered. Since I seem to send my amp in every few years for an upgrade I may wait.

In response to Wayner's concern over fire I did a melt test using an old iron set on linen 445 °F (230 °C) which, if ever reached, would probably smoke the transformer too. I set the sample padding on sheet metal, set the iron on top and left it there for 1-1/2 hours while I worked. After the initial melting and smoking stage the sample calmed down and cooked. It never did catch fire. Fun stuff guys.



Wayne

[srb]

A woodworker and a mad scientist!

Steve

[rcag_ils]

Believe it or not, I addressed this issue some time ago here, at that time, nobody cared. I used my isolators to isolate the transformers on two AVA amps with great success. Now I am using it on all AVA amps and preamps even they don't make any obvious audible noise.

[WGH]

Believe it or not, I addressed this issue some time ago here, at that time, nobody cared. I used my isolators to isolate the transformers on two AVA amps with great success. Now I am using it on all AVA amps and preamps even they don't make any obvious audible noise.

I care. Do you have a link to the thread? Or photos? I would like to see your solution.

Wayne

[jtwrace]

Maybe one of these?   

http://www.audiocircle.com/index.php?topic=78870.msg749166#msg749166


http://www.audiocircle.com/index.php?topic=96041.msg997340#msg997340

[rcag_ils]

yes, the above second link is one of them, I have been using "aviation grade" vibration isolators on most of my audio equipment with great success, but it requires a bit of work.

[rcag_ils]

WGH, I did similar mod on my power amp, but not quite like yours, I only isolated the power Xformer at three/four points from the bottom, and nothing on top, and it works.