Bigbottle Phonostage - MK3 Design, Pictures and More!

So what make were the ones that were microphonic?

Did you get microphony from the 3rd valve?

Three guesses as to what the postie just delivered.....

Blimey, I thought it was pretty much nailed on it'd take a guess or two. You been speaking with my wife?

Been having a look at the phonostage today.

Since @reffc put his together, there been some talk of "noise" when in MC mode.

I had attributed this to the quite unsuccessful implementation of an EI transformer.

The Bigbottle is quite a sensitive creature and the EI traffo has caused quite a Hum issue.

I had a chat with Paul about his experience and what he'd done to try and reduce any hum and noise, and realised I hadnt removed the Varnish from the EI's outer, so the traffo wasnt connected to the Chassis ground.

I have taken the file to it today and it is now 100% metal on metal contact.

Plugging in I noticed that the hum became audible first, as I turned the volume up. Seems grounding the traffo's exterior has made a small difference. Previously the noise and hum had been linked intrinsically.

Well, now I can clearly hear a little difference so I'm gonna go and try a little something else and see what happens......I'll report back later.

Wrap it in copper slug tape and solder a gnd wire on it.

Distance is always your best friend though.

One of the reasons I stick to toroids, the field is largely vertical apart from the lead outs which can be easily aligned.

That box looks familiar..

Has it worked?

Mine is being built as a "two box"... I feel like a pioneer

With the talk of lowering the noise on the MC input on other threads I have been experimenting.

I have cobbled up a miniature pcb to hold 4 fets and 4 resistors, as an add on to the standard board. It's not pretty and it's very fiddly to do.




The theoretical maximum improvement should be -6dB, here it is fitted to my BB3.





I can report that the noise has reduced significantly. This will be available as an add on in due course that can be fitted where the leaded fet would normally go.

Down the line I'll simply transfer mine into a standard size enclosure...no need for double boxes on these if a 440 case is used.  I turned the traffo and it's surprising at even 50mm off the board you can reduce hum to almost nothing, volume maxed out and that's on my 250 wide case.  With another 6" of case width it will be utterly silent 

As soon as the CCT is in my possession, I will fire it off to get some little add on boards made.

I will of course offer these out unpopulated at cost....

Wont be much I wouldn't have thought

What was the other one? I've forgot lol

Mute on switch on, 🙂

You can build everything around it though.