The ultimate DIY? A Stax SRM-T2!

[morphsci]

[Craig Sawyers]

I don't think a contrast dye would penetrate any significant depth in lignum vitae. I say ultrasound as the best bet.

I say using intuition and making a cut is the only way to go. You win some, you lose some - but it is always exciting. I think Kevin got a win.

[morphsci]

I say using intuition and making a cut is the only way to go. You win some, you lose some - but it is always exciting. I think Kevin got a win.

Yep, I agree. Trying ultrasound would be cool though just to see if anything can be discerned. I wonder if the OB ward at the local hospital would mind me bringing in a hunk of wood?

[luvdunhill]

I wonder if the OB ward at the local hospital would mind me bringing in a hunk of wood?

too easy!

[morphsci]

too easy!

I wanted Steve to participate more in the thread.

[kevin gilmore]

ultrasound huh? I very much doubt it.

But i do have access to a newer vintage Siemens unit, will try tomorrow.

The stuff is just about as dead as can be, i doubt ultrasound would go thru

the wood more than .25 inch.

MRI... No way.. But i have a year old bruker imaging system with a 9T magnet,

can try that tomorrow too. If it does work, that would be very slick.

None of these systems have the resolution that i think would be necessary.

At least 100 lines per inch would be needed.

I'll walk around tomorrow with my woody and see what i can do.

Edited September 22, 2010 by kevin gilmore

[Voltron]

Tice simply could not resist this last line if he were paying attention.

[morphsci]

ultrasound huh? I very much doubt it.

But i do have access to a newer vintage Siemens unit, will try tomorrow.

The stuff is just about as dead as can be, i doubt ultrasound would go thru

the wood more than .25 inch.

MRI... No way.. But i have a year old bruker imaging system with a 9T magnet,

can try that tomorrow too. If it does work, that would be very slick.

None of these systems have the resolution that i think would be necessary.

At least 100 lines per inch would be needed.

I'll walk around tomorrow with my woody and see what i can do.

If your machine has trouble penetrating it just needs moar power. Not touching the woody line.

[kevin gilmore]

Polishing of the 8 chassis is done, parts will be here monday.

Then 4 of them will go for anodizing.

[kevin gilmore]

http://gilmore.chem.northwestern.edu/woodknob3.jpg

Tried to xray the wood block. Full power, 50kv @ 50ma. 5 minute exposure.

Absolutely nothing. Not even on the part that is 1 inch thick.

I did just get funded for a copper microsource which is about 10 times the bang.

Maybe one of these days i will sneak it into the APS...

Next up Nmr Imaging. (MRI for the rest of you...)

[luvdunhill]

Is 1/4W okay for the new 10K resistors between the REF102 and OP27? Seems so. I'm thinking about just using a SMD resistor here, as it would be rather easy to fix this way. Adding that cap, is another story...

[kevin gilmore]

1/4 watt is plenty. 1/8 watt would work too. You can build the 1/8 watt into a pair of sockets.

(i'm behind on this)

[kevin gilmore]

one thing i have yet to try is to just add the capacitor, without cutting the land.

The impedance of the reference may already be high enough not to need the resistor.

[kevin gilmore]

So i messed with the imaging NMR for about 4 hours on the block of wood.

Proton(high band): Absolutely positively NOTHING. 1 hour of scans at minimum stepsize.

Carbon(low band): Maybe even the slightest hint of NOTHING. 3 hours of scans at minimum stepsize.

If there is any signal, its buried in the mud. Maybe a few days of scans might generate something.

But i really can't do that. Except maybe over christmas or new years.

Will try ultrasound on monday.

My opinion is that if there was a way to see inside the wood, someone would have already found

it and published it.

[luvdunhill]

is it just a problem with this particular species, or would the same results apply to any type of wood?

[morphsci]

Part of the problem is that this is an extremely dense wood. The problem with wood in general is that the density differentials are not that great so you need machines with very fine resolution. IMO of course.

[qusp]

yeah, in a living species they would inject some type of atomically dense marker wouldnt they?

[Craig Sawyers]

Part of the problem is that this is an extremely dense wood. The problem with wood in general is that the density differentials are not that great so you need machines with very fine resolution. IMO of course.

I think that is probably the problem with sensing the inside of the block. LV is one of the half dozen wood species with a density greater than water - LV is around 1.3. It is also full of a type of gum which both smells like strong perfume when you work it, and makes it self lubricating (it was used for propellor bearings in steam ships for that reason). So it is very homogeneous, which makes it difficult to sense internal structure.

[Craig Sawyers]

Well, OK - I've now got the BH sorted, and truly awesome it is too. Takes a long time to warm up and get on-song - but what a song! Clear that the limitation is the source (TT CD64) and phones (lamdas).

Now on to repair and get the T2 working...

[Dusty Chalk]

MRI? Kidding (probably shouldn't say things like that out loud to Kevin).

I would just like to remind the esteemed albeit insane Dr. Gilmore that I was, indeed, kidding. But thanks for taking the time to amuse us -- it's actually been very educational! (At least, for me.)

[Kerry]

Bored and twiddling my thumbs waiting for semiconductors to arrive to fix the zapped T2, I thought I'd try to get a grip on what the actual signal level circuit was doing.

I've replaced all the current sources and 740V battery with ideal symbols. I've also left out compensation components, and some of the details of one or two current sources which I think are error handling, to prevent the thing blowing up if a tube goes down badly. I think the result shows the rather neat symmetry of the design, and the clever way in which DC voltage shifts are generated using the FETs and batteries to move the ground referenced input signal to -500V.

File is here http://www.tech-enterprise.com/tekstuff/T2deconstruct.pdf

Nice job on this Craig. This really makes it easier to understand the circuit.

I've got a question regarding the current feeding the EL34s. Seems like the T2 uses 10mA over 1,000V vs the BH at 25mA over 800V. How does the power effect the sound. I know everyone's been talking about the higher voltages impacting the slew rates, but what is the optimal power for driving O2s?

[deepak]

Well, OK - I've now got the BH sorted, and truly awesome it is too. Takes a long time to warm up and get on-song - but what a song! Clear that the limitation is the source (TT CD64) and phones (lamdas).

Now on to repair and get the T2 working...

Nice work with the BH. Are you using the 2SA1968 or the new CCS? Get a pair of O2s stat, pun intended

[Craig Sawyers]

Nice work with the BH. Are you using the 2SA1968 or the new CCS? Get a pair of O2s stat, pun intended

Cheers! I'll take some pics soon and post them somewhere. I managed to scare up enough 2SA1968's, but I wonder whether a T2 style anode current source could be substituted; but is that what is already in the BH-2?

Yeah - the next pocket evacuating exercise will definitely be O2's.

[spritzer]

How much power the O2's need isn't really that straight forward. More power is always better but they also seem to "like" certain amplifier traits more then others which is why the small SS amps work better then the Stax tube amps even though the latter has more power.

The later BH has one 10M90 per tube instead of the six 2SA1968's.

[Craig Sawyers]

Yeah - the next pocket evacuating exercise will definitely be O2's.

Pocket now duly evacuated on a pair of O2's. OMG - can't write - have to go listen more.