DIY Audio General - stuff you're making, tips, advice sought, etc


#42

Well I did keep a few records - I still have a deck bit it’s being stored untilI i move


#43

You are welcome to visit - I am close to Oxford - Feel free to message me


#44

I can’t hear them from here, but they certainly look great :+1:


#45

thanks a million


#46

Result of recent pratting around. Sockets wired for ECC types with 1K grid stoppers where required, tag board to shove power supply around. Like the Kiwame resistors with printed values…


#47

Ridiculous electronic component of the day:


A 1Meg resistor rated at 5W dissipation. Just run those numbers through for a while. (Only here as HFC didn’t have the standard 2W in stock).

Forms part of latest partial faffing about.


#48

Kiwame don’t make a 2w over 510K so it’s hardly HFCs fault :wink:


#49

Also rated at 750V max I believe, which at 1M trumps the 5W rating by an order of magnitude or so (power). You’ll know at least as well as I that in valve circuits it can quite often be voltage rating which bites us before power rating.

VB


#50

First try at putting some voltage through stuff.



One at a time as I can’t find the other horrible Billington Gold E88CC, but both sides bias the same and the output looks OK within the limits of a Hantek scope.


#51

Managed to get my elderly and very basic valve tester working again, chiefly by partially stripping down the meter (there’s very little else to go wrong), cleaning and lubricating it.

The scale is meaningless in absolute terms, but is very useful as an indicator of valve health, and for matching both valves and sections within dual triodes. Plus it can health check a hell of a lot more than the Orange VT can, not least diodes!

Also cleaned and lubed the pots and switches, checked for shorts on any of the rats-nest of wiring and tightened anything that had slackened up in its 50+ years of life.

Timely, as I’d bought a dozen 12AU7 that should work perfectly and yet failed 100% short on the Orange VT. You expect the occasional duffer, but not a clean sweep. Needless to say the Model 257 found all but one slight weakling to be in perfect health…


#52

So we have E88CCs nicked temporarily out of the dac in the main system, the 81s from @chelseadave, input from a a DAC Box S USB from a Pi with its volume control down to give a several mV level and would you believe that music comes out at about a volt or so… Basically silent when nothing is happening as well.

Just need some last components ordered a few weeks ago to turn up to replace the current bit in the middle which is an approximation for what a particular type of circuit would do to a 1kHz signal…:thinking:

Only thing I might need to think about is the operating point of the cathode follower at the end to make sure it can cope with any seriously loud bits if needed.


#53

You could get a job as a Badger at ANUK if you muss that up a little bit and dent the enclosure some. :ok_hand:


#54

When it comes to the appearance of wiring, there are two levels.

  1. Graeme.
  2. Mortals.

I am in 2.


#55

While not crazy-pretty, plenty of stuff I’ve seen leaves factories in a worse state.

As for neatly bundled wires - that’s fine if you know which wires to bundle together, and which not to…

Again, IME, stuff leaves factories where that hasn’t been considered…


#56

Parallel bundles look nice, but promote coupling, so messy wiring is often quieter / less problematic.


#57

Thanks :grin: !

I spent quite a few formative years working in high-speed high-voltage engineering. High speed is only possible with low inductance which means running flow and return wires as close and as parallel as possible. Withstanding high voltage, on the other hand, is often about keeping wires a long way apart. When nanohenries matter, which they quite often did for us, there’s no option but to route the current paths very carefully indeed.

Pete’s right about coupling though. I’ve just finished working on an amp which had twice as much hum in one channel than it needed to because the lead to the mains switch had been tie-wrapped too close to that channel’s small-signal valves. Neither the valves nor the lead could be moved so I ended up wrapping grounded copper tape round the outside of it to screen the electric field which was causing the trouble. Sometimes stuff you learn in one job turns out to be useful in another.

VB


#58

These have arrived in the post…


#59

Admittedly what I’m doing isnt real DIY as there’s no hammers or belt sanders involved, but this is the only remotely suitable thread so I thought I’d mention here that I’ve got a MiniDSP 2x4 HD. It is all @Adpully. 's fault as he made me do it.

The intention is to properly integrate my speakers, subs and room. I’ve a vague idea that rolling off my main speakers around 70hz and letting the subs do the work from there will take the strain of the fostex drivers and improve their performance. I also hope to remove a shitty 80hz room-boom in the process.

Once the active subs are setup using the software I can use their own filters to mimic the DSP’s settings and then fully DSP my main speakers, removing their internal crossovers and Lpad. (That is a long way off.)

I threw it together last night, stabbed around in the software and did this…

The slopes are too steep, but it demonstrated there’s real potential.

I realise I’m late to the DSP party however the software is incredibly flexible and I reckon given time it will do more than I’d hoped for. I expect I will need to change amplifiers to make the system workable long term. (The DSP with its remote makes for a clumsy preamp with cables on both sides, but that is forgivable.)

Next installment will be in room measurements…


#60

Going through a similar process myself at the moment. Using a minidsp 2x4. Have you installed REW? Very useful for taking measurements which can then be converted into files and sent into the minidsp.


#61

No not yet, literally had an hour with it last night.
I’ll look that up later this week, sounds ideal.