Transformer Flux Bands

[Greg.]

DIY Supplement 73, June 2003, entitled ‘Quiet as a mouse Udo’s gripe’.
PS. States copper band does not require earthing.

[Richard]

Thanks Greg, an interesting read.
Which Sowters did you use, frame type or drop-throughs? Were you able to maintain a 90 degree orientation with the mains TX? If not and the OPTXs cannot be moved could you rotate the mains TX or fit/remove mounting frames?

[bob orbell]

Chris, you wrote,- Bob what you built is a completely different beast to what I am using from how you describe it.- now then, of course I have no intention of offending anyone but, I built a Pre II to go with my Phono II and KAT6550, the two later products were good but the Pre was weedy thin, had far too much gain and hummed, IE ****, I tried a few tweaks such as different valves, better resistors, capacitors etc, but it was still ****, I gave it up as a bad joke, now then Chris, your Pre, we will not call it a Pre II because you have said it has been significantly modified, many on here around the time of it's arrival complained about hum, too much gain and other things, so a member Neal Gibbons decided to change it to a cathode follower and publish the nessasery change, the change was excepted by many and most stayed with this design for a long time, personally, I never want to see or hear another ever, but would be interested in some pictures of what you have done, so, over to you. Bob

[Greg.]

Richard, I had some frame Sowter output Tx’s made for 2A3 on loan from friend, Steve Shiels. I removed the original drop through Tx’s and tried the Sowters on flying leads. Tried them in every position and had a buzz which wasn’t present with the standard Tx’s. I later acquired a pair of WAD 300B PSE (mono-block) frame Tx’s which were really good quality. I had them measured and the result was excellent and linear throughout the full frequency range. They didn’t buzz so much and the level was acceptable to get away with a well received demonstration at an Owston a few years ago but they were too noisy at home.

At the time I was collaborating member James (not been here of 7 years) and we concluded it was the close proximity to the mains Tx causing the problem. We then devised a plan to separate the PSU from the main amplifier and built an improved version to create a two box system but although I stripped out the chassis and started collecting parts towards this project, it never came to fruition partly because I lost incentive at the time and for some reason unknown to me, James removed himself from the scene, cutting contact with me and everyone else.

I have now sold on the 300B PSE Tx’s and I’m in the process of restoring the 2A3PSE with the original, albeit considered inadequate Tx’s. They always seemed to work ok for me in my system at home, so I’m looking forward to getting the amp running again.

I’ve reached the wire hook up stage and am struggling to find motivation although, in the meantime, I’ve cleared out my garage and now have my workbench and assembly desk permanently back, so I’m a happy bunny and hope to have the rebuild finished soon.

[Greg.]

Big thread drift. Chris, I hope you are ok with that. I can always start another thread if you don’t like it.

[bob orbell]

Originally Posted by Greg.

Big thread drift. Chris, I hope you are ok with that. I can always start another thread if you don’t like it.

That seems to be the way to go Greg if you can move all the nessasery posts with regard to the Pre II. Bob

[Chris]

Greg it's good to read well written posts from you, I have all the information needed on the thread size and so much more, lol. Bob came up with the size and others added important details.

It seems we are much stronger as a group, individual ideas only go so far.

I would never have thought of using threaded rod and cutting it to size now I can experiment with different materials under the transformers.

Transformers seem to generate lots of heat, then we put a chrome lid on them, is that purely for aesthetics?

With the hum side of things I've added a DC blocker, which gives some benefit, this is the one I bought (link). But it's just very basic, there is a guy on Ebay that sells diy version or fully made up. Mains stuff is all depended on the individual home, where you live, i.e. results will differ.

https://hifipig.com/mcru-excelsior-dc-blocker/

[bob orbell]

Chrome transformer covers, they do look nice and serve a purpose, away back when I read in Morgan Jones book about shiny things next to valves and me being me decided to make the covers from solid chunks of aluminium, I also did this to my KEL84 pictured on here somewhere, they are machined to a similar shape as the originals but about 25mm higher with fine fins machined in them they were anodized satin black, they do look very good on the WA88, they still get warm but not quite as warm as the chrome tops and I hear no difference in sound, but it gave me something to do for about 12 hours. Bob

[pre65]

Originally Posted by bob orbell

Chrome transformer covers, they do look nice and serve a purpose, away back when I read in Morgan Jones book about shiny things next to valves and me being me decided to make the covers from solid chunks of aluminium, I also did this to my KEL84 pictured on here somewhere, they are machined to a similar shape as the originals but about 25mm higher with fine fins machined in then they were anodized satin black, they do look very good on the WA88, they still get warm but not quite as warm as the chrome tops and I hear no difference in sound, but it gave me something to do for about 12 hours. Bob

It's nice to do things, just because one can.

[Chris]

Bob, the fins idea is really cool, sorry for the pun! I was thinking just that to have some kind of heatsink to take away some of the heat or even to have it vented.

Chris