audio-talk

Look what you've started. It's (sort of) snowing here in Kent now!

Wind from the North. Winter is coming...

Set up my old mac mini upstairs out of the way. I got the kids a gaming pc for Christmas and used the keyboard mouse and screen for that, then put the mac away intending to set it back up at some point. Before all this kicked off I'd picked up a keyboard from a charity shop along with an old monitor for a tenner. I later found it was a vga monitor so was no use with the mac. But digging through an old box I found an ancient hdmi to vga converter. Which worked. So I now finally have some office space
Dug out the Squeezebox too as it can now be run again.

Im thinking about resurrecting an old dac that Neal gave me a few years ago, ak4493 I think, to go with it but it needs a case to go in.
Think I have a metal extrusion somewhere, but if not, I presume it would want some shielding of some kind?
Digital is not my forte

This is more on the lines of what NOT to do when self isolating and bored:

https://www.theguardian.com/australia-n ... hlExltf4N0

I've just spent most of the weekend rediscovering some of my valves, then a good spell of testing and matching.
Also spent slot of time trying to find the ideal load for my mazda p650 's theres not much on the net and I don't have any early mazda info
Its roughly the same spec as some of the early 1929 px 4 equivs,( the early 200 v versions) but it could well be 5 or 6 watts dissapation as it outputs only 1.1watt... Anybody? .. Edit my calculator says it dissapates 4.4 Watts

The p650 was soon out of date and was replaced by the pp3/250, one of the valve sites has the specs but its €25 to join and read the detail.
I've read up trying to work out the ideal load, the rough and ready 3 or 4x the plate impedance will do.

I had a pleasant surprise in that I found quite a few early mesh /globe mh4 and all but 1 tested well. So I'll try a pair
driving the p3521 amp, my plan is then to change the sowter output txs for tributes, and then swap out the p3521s for the p650s, just need dc heaters and the cathode end sorting.

I'm having quiet a valve amp revival these last few weeks..

simon wrote: ↑Sun Mar 29, 2020 6:35 pm

izzy wizzy wrote: ↑Sun Mar 29, 2020 5:39 pm Speaking of quality carpentry and working with good materials, today I resurrected the third bay of our compost heap with recycled pallets from the stone delivery.

Photo, surely?!

It's yer classic 3 Bay compost bin setup. Resurrected one on left. They last about 5 or so years before a revamp.

Will be doing the input stages on the Super Rocky amp this afternoon. After that it’ll be putting it in the system and trying to listen to music over the hum, whilst attempting to convince myself it sounds absolutely fabulous dahling!

The guy with magnets up his nose, sounds like an April fool joke! (Which is tomorrow)

steve s wrote: ↑Mon Mar 30, 2020 11:11 am I've just spent most of the weekend rediscovering some of my valves, then a good spell of testing and matching.
Also spent slot of time trying to find the ideal load for my mazda p650 's theres not much on the net and I don't have any early mazda info
Its roughly the same spec as some of the early 1929 px 4 equivs,( the early 200 v versions) but it could well be 5 or 6 watts dissapation as it outputs only 1.1watt... Anybody? .. Edit my calculator says it dissapates 4.4 Watts

Want to borrow my utracer then you can create some curves for them

Mike H wrote: ↑Mon Mar 30, 2020 1:16 pm The guy with magnets up his nose, sounds like an April fool joke! (Which is tomorrow)

I think it’s completely believable. I have a friend who does just that sort of thing. In the past he has nearly sliced all his fingers off one hand whilst checking the lawnmower blades are spinning properly, burnt his figures whilst checking to see how hot a recently expired magnesium fuse was, frozen his tongue to the pillar valve of a recently rapidly discharged diving cylinder whilst checking to see how cold it was and suffered excruciating pain when he applied plumbers freeze to his scrotum in the hope of alleviating some other discomfort

Nick wrote: ↑Mon Mar 30, 2020 1:18 pm

steve s wrote: ↑Mon Mar 30, 2020 11:11 am I've just spent most of the weekend rediscovering some of my valves, then a good spell of testing and matching.
Also spent slot of time trying to find the ideal load for my mazda p650 's theres not much on the net and I don't have any early mazda info
Its roughly the same spec as some of the early 1929 px 4 equivs,( the early 200 v versions) but it could well be 5 or 6 watts dissapation as it outputs only 1.1watt... Anybody? .. Edit my calculator says it dissapates 4.4 Watts

Want to borrow my utracer then you can create some curves for them

Thanks nick but it's a fair drive when I should be at home. I can nearly see the stock curves on one of the valve sites. The valves I'm using are very close to standard so I'll get it near enough. As long as is dissapating the right amount and the voltages are right I won't be far off..

steve s wrote: ↑Mon Mar 30, 2020 2:35 pm Thanks nick but it's a fair drive when I should be at home. I can nearly see the stock curves on one of the valve sites. The valves I'm using are very close to standard so I'll get it near enough. As long as is dissapating the right amount and the voltages are right I won't be far off..

I would have posted it.

Cressy Snr wrote: ↑Mon Mar 30, 2020 12:56 pm Will be doing the input stages on the Super Rocky amp this afternoon. After that it’ll be putting it in the system and trying to listen to music over the hum, whilst attempting to convince myself it sounds absolutely fabulous dahling!

It’s running now and soak testing whilst I have a cup of tea and a ginger nut. All the voltages check out nicely. The bias on the KT77s is within half a volt of the predicted value and the 6SL7s are bang on for bias too.

There are twin mains transformers and two choke-input power supplies: one on the output and one on the input stage. The input stage draws a constant 20mA through a shunt resistor as without it, the pair of paralleled 6SL7 would not provide sufficient load current to stabilise the supply in choke mode. If the project proves viable in terms of actually being any good in comparison the the NVA clone, I may get out some glow tubes to shunt regulate the input stage.

Output stage is rectified by a hybrid bridge, with a GZ37, whilst the input stage uses an EZ81 as the valve part of its hybrid bridge.

We’ll see whether it hums or not shortly.

Nick wrote: ↑Mon Mar 30, 2020 2:48 pm

steve s wrote: ↑Mon Mar 30, 2020 2:35 pm Thanks nick but it's a fair drive when I should be at home. I can nearly see the stock curves on one of the valve sites. The valves I'm using are very close to standard so I'll get it near enough. As long as is dissapating the right amount and the voltages are right I won't be far off..

I would have posted it.

Thanks Nick but I've decided to do the whole lot in one go. Hopefully it will be working tomorrow..

Steve I've just found a kt66 amp I built about 10 years ago. It had those Hammond on it once.. it had arff a ecc something as a driver surprisingly there is some nice components in it
Oscons and bg's
Best of luck with rocky..

izzy wizzy wrote: ↑Mon Mar 30, 2020 11:44 am It's yer classic 3 Bay compost bin setup. Resurrected one on left. They last about 5 or so years before a revamp.

Compost bins in the sunshine, lifts yer heart!

Two of Andrew's DHT filament supplies configured, tested and installed in my 300B HPA.

No sign of UPS yet so I'm not able to finish the Maida regulator for the B+. Shame as I'm only waiting on one capacitor!