Bucking Transformer

[ampbldr2]

I like the idea of having a bucking transformer for lowering the AC line voltage coming out the house outlet on days that it is high.
You can see the project on Slucky's site. sluckeyamps<dot>com/misc/Amp_Scrapbook.pdf

I have been monitoring my house voltage for about two weeks now and readings swing from 116-127 Vac so having one of these to buck the voltage on a high day seems like a good idea. The problem is you can not source the radio shack Cat # 273-1511 transformer anymore.

Is there another brand that would be a close spec to the radio shack one?
Also are there significant drawbacks to using one?

[gktamps]

You can use a variety of transformers as long as they provide the voltage and current specs you need.
I've built several bucking transformers for my audio gear, and have used new Hammond and used Triad 5V filament transformers.
Figure out how much voltage you want to drop and remember that the current rating must be equal to the entire current draw of your amp.
Here's one I built for my tube mono blocks; it is comprised of 2 5VCT 8A transformers, switchable for voltage drop.

DSCN3161.JPG

M125Bucker2.jpg

[ampbldr2]

Thanks for the info. I think the Hammond 167R5 transformer voltages will work my equipment.
Mother nature 50mph wind gusts decided to snap one of my fence posts today which is going to delay my plans for new stuff.
Also, I have been considering adding tubes4wifi m125 mono blocks to my pioneer SX1050. What mono blocks are you using?

[gktamps]

Ooh, sorry about the damage.
I have the same amps, with some of my own refinements.

[dayn]

I also need to figure out a bucking transformer, as I have 122v at my wall, and a 100v made in Japan tube amp that I want to use. I've seen some posts about making a bucking transformer to get down to 110v, but I need 100v.

Ot is it better to just get a step-down transformer? I also have a couple 220v and 240v amps, so maybe I just need a fancy one that can go up and down.

[sluckey]

Just use a very common 24VAC transformer.

[dayn]

Just use a very common 24VAC transformer.

I think Rob Robinette used a Hammond 166N12 for his bucking project. So maybe the Hammond 166N24?

I see you used a Radio Shack part for yours - I'm open to parts suggestions if there is a good readily available 24v T up to the task.

[sluckey]

So maybe the Hammond 166N24?

AES has that for $40. Bet you could get a suitable 24V/3A transformer from your local HVAC supply house for a lot less. Totaline is a generic HVAC replacement brand. I suggest you get a 75VA power rating (24V/3A) like this one on eBay. Maybe even buy this one...

https://www.ebay.com/itm/154903224486?h ... SwVCJhzgJm

[WhopperPlate]

Curious, do y’all have a preference for bucking transformers ? as opposed to simply utilizing a variable auto transformer off the AC mains?

[gktamps]

Definitely prefer bucking transformers to a Variac-type solution. Smaller, lighter, no chance of accidentally raising voltages, less chance of failure.

[WhopperPlate]

Definitely prefer bucking transformers to a Variac-type solution. Smaller, lighter, no chance of accidentally raising voltages, less chance of failure.

I have been using an old W20MT3 plugged into various fuse protected power conditioners/isobar power strips , tapping the Variac with another isobar strip . These portable Variacs have their own fuse protection as well .

Whereas I can’t say that I have experienced all possibilities of faults and failures , nor can I argue against its hefty size, but this arrangement has seems to work gig to gig .

The biggest problem I have experienced is making sure the Variac doesn’t flip a temperamental power breaker at power up . I have only dealt with this in old homes with sub par electrical .

[WhopperPlate]

Searching the net I found this relevant article that gives some cool food for thought .

https://sound-au.com/articles/buck-xfmr.htm