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Old 23rd August 2013, 02:12 PM   #1101
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Many thanks for that Andrew.
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Old 26th August 2013, 03:23 PM   #1102
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I am mounting the two transformers vertically, mounted on an aluminium plate. It occurred to me that I could save some more space by mounting a second set of much smaller transformers (for the front end supply) the other side of the metal plate using the same mounting bolts. Will the big power transformers cause inductance in the smaller transformers either through the metal plate or via the shared mounting bolts?
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Old 27th August 2013, 08:34 AM   #1103
AndrewT is offline AndrewT  Scotland
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You can mount extra transformers in line.
Just be very careful you do not create a shorted turn.
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Old 27th August 2013, 10:57 AM   #1104
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Thanks Andrew once again. As a matter of general physics does the intervening metal plate reduce the influence of hysteresis between the two transformers? I'm thinking it certainly won't abolish it when you think of a magnet below a metal tray with iron filings on the other side and how does a GOSS band work?
Sorry this is turning into a Wikipedia enquiry.
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Old 27th August 2013, 10:59 AM   #1105
Zen Mod is offline Zen Mod  Serbia
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two Dounuts are not having much influence to each other
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Old 28th August 2013, 11:40 AM   #1106
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Thanks Zen. Two will make you fatter than one though.
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Old 2nd September 2013, 01:03 PM   #1107
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Cable shielding:

I'm running my mains cable close to one of the power boards. I am already using Supra shielded cable to reduce radiation from the mains voltage but I have also put a braided sleeve around it to increase protection from radiation. However, where to ground the braid? I have been doing some reading on the subject and low frequency radiation it is suggested requires grounding at one end but there are those that suggest to protect from higher radiation frequency or magnetic interference both ends should be grounded.
What is the verdict?
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Old 5th September 2013, 01:24 PM   #1108
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Ah! I think this answers it: Cable Shield Grounding
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Old 22nd November 2013, 02:17 AM   #1109
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Default Burning Amp Lamp

Burning Amp Lamp

Hello to all my fellow Burning Ampers (or should that be Burning Amperes?).

I have had many hours of enjoyment listening to my BA-2 amplifier over the past year. My thanks again go out to the man who made this possible.

One thing I neglected in my haste to get the amp working was a power on indicator. This oversight has added to my electric bill, since, more often than not, I forget to turn the amp off when I am finished listening.

Recently I decided to move the amp back to my workbench and install something to let me know when the amp is powered on.

My first inclination was to stick a simple LED on or behind the front panel, which I made from a 19 inch dual height rack mount perforated metal security cover. I thought using the security cover for the front panel would give me some degree of shielding from electrical interference while still letting me see the internal circuitry of the amplifier. I have a bad habit of opening equipment up from time to time to look inside if I can't see inside without taking covers off!

I went digging through my parts boxes and ran across a tri-color (RGB) Cree LED illuminator PCB that I had bought for another project and never used, and my mind started thinking of somehow using it as a combination amp interior illuminator and power on indicator. I thought it would be cool to be able to dial up any color I want to light up the inside of my amp.

As I thought a while about various ways I might make best use of the device, I thought back to my younger days when I used to stare inside the back my dad's tube radio while he listened to the baseball games he dearly loved. The warm orange glow from the tube heater filaments was bright and cheery looking, and I fell in love with that look. It struck me that I would love to recapture that same look inside my Burning Amp, which has the physical warmth of a tube circuit due to the high bias of its impeccable Nelson Pass design, but not "that tube glow" that I love.

So I sketched out a simple triple adjustable constant source to drive the LED board. I built and wired the circuit across the second set of power supply filter caps so that the LED's light up as the amp is powered up.

There is enough delay in the RC supply circuit and inrush thermistor that the LED's come up gradually, looking very much like the filament light in a tube amp upon turn on. I mounted a white translucent plastic rod over the LED emitter so that the illumination would be diffused and spread throughout the interior of the amp with a good portion of it being visible through the perforated front panel.

With the circuit completed and in place, I turned the room lights down and started playing with the three color mix pots in search of that perfect filament glow.

I found that I didn't need the blue LED at all, and it was reasonably easy to mix the red and green LED's to achieve the look I wanted.

I hooked the amp back up to my living room system and turned the room lights off. When I hit the power switch and watched the amp power on, I couldn't help smiling at its fine new look.

And there was a bonus that I hadn't anticipated--when the amp is powered down, the discharging power supply caps allow the illuminator to gradually dim, adding very much to the tube illumination illusion.

So now my Burning Amp is finally finished, and my support of the local electrical company should be a little less.

If anyone is interested in the circuit, let me know and I will gladly share it with the group.

Thanks to everybody here. I really love learning from you all.
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Old 9th March 2014, 09:26 PM   #1110
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Greetings all,

I populated a BA2 FE board from the diy store and all my readings are ok. But the D-out are reading about 12V. is this normal? Also, is it possible to hook this up to an amp, say an F5 or F6?
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