Next Single Ended build

IslandPink · Post by **IslandPink** » Mon Apr 28, 2014 9:29 pm

Some nice background info :
http://vinylsavor.blogspot.co.uk/2014/0 ... -801a.html

Paul Barker · Post by **Paul Barker** » Tue Apr 29, 2014 7:13 am

Poetry in pictures.

Will · Post by **Will** » Tue Apr 29, 2014 11:15 am

Geat valve .. I wont tell about pairs of 801's for £30 from S Korea

Dave the bass · Post by **Dave the bass** » Tue Apr 29, 2014 11:18 am

Oh gwarrrrrn!

DTB

Will · Post by **Will** » Tue Apr 29, 2014 11:25 am

Back to work sunshine.. pay my pension

Mike H · Post by **Mike H** » Tue Apr 29, 2014 11:53 am

Dave the bass · Post by **Dave the bass** » Tue Apr 29, 2014 10:15 pm

Will wrote:Back to work sunshine.. pay my pension

Shurrup you!.... and get back to your (singular) Muddy Waters album

DTB

Paul Barker · Post by **Paul Barker** » Fri May 02, 2014 1:12 pm

Sadly the Hammond four Interstages don't fit and never will.

I could sprout the interstages out through the sides but that will look very bad.

What a contrast to our Steve's projects.

Back into thinking of what and how to change. Might yet end up with a cap coupled stage just so it fits the case..

pre65 · Post by **pre65** » Fri May 02, 2014 1:14 pm

Paul Barker wrote:Sadly the Hammond four Interstages don't fit and never will.

I could sprout the interstages out through the sides but that will look very bad.

Better untidy than crap sounding ?

Cressy Snr · Post by **Cressy Snr** » Fri May 02, 2014 2:27 pm

pre65 wrote:
Better untidy than crap sounding ?

'ere what you sayin?

Seriously though, there's nothing wrong with RC coupling.
That 6B4G SE amp that created such a wonderful sound at Owston, a couple of years ago was cap-coupled with guitar amp caps.
It didn't seem to be at any disadvantage.

Paul Barker · Post by **Paul Barker** » Sat May 03, 2014 5:04 pm

I have invested sufficient spending and effort on the casework that I will press on and build something which fits it.

This version is purely because it fits. The version with two stages of interstage can be built at a later date in a different case.

to make sure it fits the case I need to use just one filament transformer, and there isn't enough space for the dc filament supplies. So I am gambling. I gamble that the 50 hz hum of the 10y and the PX4 can be nulled by providing adjustment on both. There should be a null which eliminates all 50 hz hum. That leaves the 100hz hum. The 10Y is the dominant source of this hum and it's effect can be mitigated considerably with the 1n4148 circuit shown. The second half of the gamble is that the 100hz hum of the px4 will be nulled out by a value of 10Y 100hum adjusted to with the 5k pot. So it is expected that no 50hz or 100hz hum will break through. The higher order harmonics it is hoped won't case a problem. If they do I will have no choice but to use the dc modules off board and import filament voltages aswell as B+. I would rather not do so.

The change to a 27 for the first valve is in order to make all the heater voltages come within the scope of the 50 watt self wind heater transformer. If I kept the 10y in this position it would be a significant hum problem and tip the project past a single 50 watt heater transformer. there isn't space for another.

I have managed to retain one 10y. This circuit is the largest I can go and remain in the confines of the chosen box.

I could have gone to the 5687 had that been a problem.

So I am hoping that with this design I will have a very good workaday PX4 amplifier which fits into a reasonably sized box.

pre65 · Post by **pre65** » Sat May 03, 2014 5:28 pm

I found an old (mid 60s) Wireless world mag in a charity shop in Canterbury over Easter, and they were advertising PX4 for 17/6d.

Will · Post by **Will** » Sun May 04, 2014 10:30 am

Move the first section into a separate box and call it a Pre-Amp

pre65 · Post by **pre65** » Sun May 04, 2014 10:32 am

Will wrote:Move the first section into a separate box and call it a Pre-Amp

It'll never catch on.

Mike H · Post by **Mike H** » Sun May 04, 2014 12:05 pm

Mind you 17/6d weren't that cheap in mid 1960's - and a lot of it was tax

audio-talk

Next Single Ended build

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