Why I haven't been building bikes this year

[Mark Kelly]

First one.jpg

One unit

Build in parts.jpg

Ten units in bits

Main_board.jpg

The heart of the matter



This project has consumed all available resources. It finishes tomorrow.

For those who are wondering, they are specialised motor drives designed to run the ancient Garrard 301 turntable.

[devlin]

So would you be able to build guitar amps as well? Nice by the way.

[Britishbane]

I assume ancient isn't quite correct, right? I've no doubt you've built a new plinth, rejuvenated or replaced bearings, etc. What tone arm(s) are you using? Cart? Details man, details.

[Paul]

Yes, let's see more.
That's a lovely piece of work!

[Mark Kelly]

I assume ancient isn't quite correct, right? I've no doubt you've built a new plinth, rejuvenated or replaced bearings, etc. What tone arm(s) are you using? Cart? Details man, details.

Well the one I have is my age, so it probably feels ancient at the moment.

Yes, it's a homemade plinth as is usual with these things but I'm about to replace it with one laminated from veneer leaf the way I do my frames. Less usually, I made the tonearm too, and am in the process of constructing a new one which is a pivoting linear tracker (think Burne Jones, but this actually works).

Cart at the moment is a Grace F9 but I'm talking to the people at Garrott Bros. about making me a special version of their P77 with one "channel" responding to horizontal modulation and the other to vertical. It looks like a goer, but I have to rebuild the tonearm to suit.

[Mark Kelly]

So would you be able to build guitar amps as well? Nice by the way.

I would, but the subjunctive is appropriate. I don't and won't, not my field.

[summilux]

Good lord. Are you the Mark Kelly of the LP12 board? I've got one of those languishing because I've been spending too much time on my bikes. My next project is going to be a Lenco anyway. Never thought there'd be someone from diyaudio here.

[Britishbane]

Good lord. Are you the Mark Kelly of the LP12 board? I've got one of those languishing because I've been spending too much time on my bikes. My next project is going to be a Lenco anyway. Never thought there'd be someone from diyaudio here.

It is. The one and only.

[Mark Kelly]

Are you the Mark Kelly of the LP12 board? I've got one of those languishing because I've been spending too much time on my bikes.

The board in pic three above retains several design elements from that synch board. The microcontroller at bottom right now does the frequency division of the quartz clock instead of the clunky counter chip version I first used but the logic that generates the stepped waveform is the same.

Voltage setting now uses a bandgap reference chip and digital pots so it can be adjusted from the front panel. The filter now uses a tracking PLL to set F0.

The analogue section is similar except this is a single phase so the second "channel" is used for feedback. The big change is that this signal is passed to a 12AU7 driving a pair of KT88s, the OPTX on the KT88s is effectively just an isolation transformer (1:1 winding ratio plus feedback coil).

[summilux]

The big change is that this signal is passed to a 12AU7 driving a pair of KT88s

Dammit, you've ruined my evening. Now I'm going to have to pull the schematic and figure this out. And I've got a Crumpton to build.

[Mark Kelly]

I was going to say "build the Crumpton and ride it, don't worry about amplifiers" but I'm guessing the weather in Ottowa is not conducive to riding a brand new Crumpton at the moment. (Google weather says it's 4 degrees C at 4 pm)

[summilux]

Ski hills open next weekend here, so other than commuting, outdoor time is ski time. The Crumpton isn't going to be used until March at the earliest, so I'll have to content myself with staring at it. My audio goal for the winter is to get the Lenco working.

[Mark Kelly]

Downhill or real skiing (the one with uphills too)?

[summilux]

Ha! Funny thing, I love to climb on a bike but I absolutely hate Nordic. Too bad since Ottawa has great XC trails less than 15 minutes outside of downtown. Global warming is cutting into the XC season, but January to early March are pretty reliable. Being a lazy sod on skis, the skiing I love is the one that has features a bar after each run.

[Cookietruck]

looks pretty awesome.
i wanna see pics of the turntable...

[Mark Kelly]

I'll post some up when the new tonearm and plinth are finished. Won't be for a while.

[Cookietruck]

yeah i know how it goes. i don't have anything fancy (except the cartridge i guess) but i do like the empire i have.
built a little arm board and mounted a pretty cheap tonearm on it, sounds pretty ok. the cornet phono stage made a huge difference in the sound though.

[Mark Kelly]

Over a year later, the last one heads out the door Monday. This one is PP 300Bs with 12BH7 driver; a little OTT for a turntable motor drive, but it seems to work exceptionally well.

Common thread with the bikes: that front panel is Tasmanian Blackwood Acacia melanoxylon which I also use on my frames.

Last One

I have finally fulfilled the commitments I made five years ago and can gracefully retire from the field.

[zetroc]

Mr. Kelly,

I regret to inform you that posting photos of these fine creations obligates you to build more of them for any forum member who may want one, payable upon receipt.

Yours,

The Forum




Seriously though, that looks incredible. I wish I had one tenth your skill. My hat is off to you.