Tuesday, January 30, 2007

Isolator completed. 3 Hardwired output cords (quickie types), hardwired input. Not a lot more to say here, lot of found parts and scratch. I've used such devices before to good effect. A diversionary mockup to distract me from future projects.

I may have a disease on my hands.... can't stop building junk... not even time to post most of it here.

Monday, January 29, 2007

Latest fiddlings

The innards: EI trafos with their secondaries connected to each other, in pairs. Common connection to the mains on the primaries of one group of transformers (3), the primaries of their correlated transformer are connected to the load (power inlet for DAC, CDP, ETC). It's a way to do an isolation transformer (with it's many advantages) with found transformers.

Don't know if they'll be good for more than 35W a pair. I'll toss some small caps across the secondaries for additional HF filtering. The output wiring and those caps are still pending.

The base. You can see that I used U-channel for the transformer mountings. Cut them by eye with a hacksaw, and drilled the holes by hand. All hardware is stainless, with nylon insert locking nuts. Nice and solid, despite the lightweight box (1/4" ply winebox). The cables will be hardwired, the quick and dirty power inley cable is shown. 3 leadouts with IEC connectors will be used to power several devices. I'm hoping it'll drive my DVD/SACD/CDP, which draws 43W according to spec.... might be too much. We'll see. Certainly the dac, linestage, and digital EQ effectively, so it won't go to waste if it's too small for the player.

What else.... fiddling with digital EQ in the big rig, installed surround channels in the bedroom rig. What's next, still pending is the preamp: octals, with phonostage. Will be using a chassis from www.diyenclosures.com. Also, the time has come for us to start playing with driver modification. After that's up and running, we're probably going to have a little fun with a small open baffle, with a high density driver compliment- 4 8"s (peerless HDS), a high eff. midrange and tweeter.

I've been keeping hifi on it's toes for a goodly while now.

Thursday, January 04, 2007

A little fix me up

The big rig needed a little TLC. There's a circuit correction for the transcendant that was never done (is now), not to mention, swapped out the horrid heater diodes for the driver stage (1N4007, awful noisy nasties) for uF4007, a 25c drop-in much lower noise replacement.

Nice gain in smoothness and clarity, a little better transparency too. Don't know how much came from which, but I've always had impressive results replacing noisy diodes in the past. I also had to make a fix in the linestage (12AY7 based circuit, simple plate amp running at about 190V and 3mA.), the grounding on the attenuator (chinese 24 step stereo 100k ladder) had worked it's way loose, so it was intermittent, and jiggling around causing the loss of the shunt element..... drivers with 0.3mm xmax aren't meant to jump around! Good thing they weren't hooked up to a big class D amp, but rather the OTL.

Next Victim on the repair list: A finnicky LP12. Also have a passive preamp to rebuild for a customer, and my own big Phonostage/Preamp. After that, looking like open baffles, probably with 4 8"s ..... perhaps with a horn midrange! How strange! Still working out the details of the horn, probably a 400Hz or so round tractrix.

If anyone's reading this, comment so I know!

Wednesday, January 03, 2007

Some Miscellaneous ramblings and my office rig

The Dyanco Super 70, an Audio by Van Alstine rebuild of the classic kit amp (New driver stage, power supply). This is replacing a little Sonic Impact T-Amp, the $30 wonder amp. Well, this AVA piece is definitely a lot more powerful and has better mid and detail, but there seems to be a less airy top end. Wondering if I just need to let it get up to speed. It definitely doesn't suck.
Had to re-rectifier and rebias and replace a broken Silver Mica cap in this, but otherwise in decent shape. I bet a little TLC and I could get some real singing out of this.

Beneath it is a DIY build into an old Rotel CD player chassis (waste not, want not). Microprocessor controlled relay and resistor network, 4 source selection, 99 step 1dB volume control, balance, mute functions. Nice little box to stack under a power amp when you really need an integrated and not an active linestage. Basic Pioneer CD changer (a better dac would open things up, so may go to hard disc playback with a dac) And of course, these are driving the Galacticons (scroll down). Pretty darn good office system. And yes, the FR125s can bump a little bit, though ultimately still a 4.5"

In the bedroom rig, the Peerless HDS tweeters are singing nicely, I have the whole setup wired as a 2.5 way first order (midrange/woofer first order at 240Hz, cap coupled tweeter, no lowpass on the mid), and it's pretty rocking. The 15"s don't overpower the room, even run passively, which is lucky.

Working on a big preamp next, probably, octals w/phonostage. Got the parts, need the time. Anyone got a week to spare?