The Ultimate DIY Part 2 ? The KGITSOJC

[Beefy]

Here is a larger picture of the CTC unit:

That thing is seriously calling out for a couple of shaft extension kits......

[n_maher]

Not as standard - 1k, 5k and 10k only. I've heard rumours on the web of higher values, and I've reasonable confidence that they will do custom values

They won't do any higher than 15k, I spoke with the US distributor about this last year when researching stuff for the T2 project.

[edit]And I can't help but feeling that the Ayre is a colossal waste of raw materials. I understand doing a one-off like Kevin's T2 out of a single block but for a commercial products where you end up removing 75% of the material... seems like pissing money down the drain with no benefit.

Edited April 5, 2010 by n_maher

[spritzer]

I'd ideally like 50K but 20K should be more then enough to cover very high impedance sources (NOS dac's and the like)

[kevin gilmore]

The aluminum is recycled. Still it takes lots of energy to melt the stuff down and re-purify and recast.

At the prices ayre is charging, he probably does not make too many of those things.

They sure are nice however.

The blowtorch's were also machined out of a solid block of metal. and then they still have an end plate.

What a complete waste of materials.

[spritzer]

It makes a lot more sense to build these things like Pass did (does?) with thick sections of aluminum all attached to corner pillars.

[n_maher]

It makes a lot more sense to build these things like Pass did (does?) with thick sections of aluminum all attached to corner pillars.

It'd certainly make working on them a hell of a lot easier. Could you imagine trying to service the Ayre? It looks damn near impossible to remove the "modules" not to mention just getting visual access to see if a part went poof.

[dsavitsk]

"3rd" wire of a balanced input should be connected directly to the enclosure anyway and to nothing else

Yes

that's the 4th wire, and very few people actually ever wire that.

No.

Sound System Interconnection

[Beefy]

Yes

No.

Sound System Interconnection

That doesn't apply to the bridged amps common to us though, does it? Consider a 'balanced' B22...... it should have the ground/pin1 from the balanced interconnect connected to the signal ground on the boards. Signal ground can then be connected to the chassis through a ground loop breaker.

[Craig Sawyers]

They won't do any higher than 15k, I spoke with the US distributor about this last year when researching stuff for the T2 project.

That's interesting, Kevin. While you've got one answer of 15k from the US distributor, I've just mailed my contact at the P&G factory and asked about 20-50k audio taper possibilities. I'll let the list know if I get the same answer (or a different one!). Might be a few days because of Easter.

[n_maher]

That's interesting, Kevin. While you've got one answer of 15k from the US distributor, I've just mailed my contact at the P&G factory and asked about 20-50k audio taper possibilities. I'll let the list know if I get the same answer (or a different one!). Might be a few days because of Easter.

My quote from last year for 10k 4ch RF15s was $390.27 each with a min purchase of 10. Lead time for stock values was 6 weeks.

More importantly I misspoke, P&G will go up to 20k, but allegedly refused to go higher.

[dsavitsk]

That doesn't apply to the bridged amps common to us though, does it? Consider a 'balanced' B22...... it should have the ground/pin1 from the balanced interconnect connected to the signal ground on the boards. Signal ground can then be connected to the chassis through a ground loop breaker.

Balanced != Bridged. Balanced has no signal ground. The benefits to a balanced topology are many, while the benefit to bridged, at least in headphone use, is that the manufacturer can sell twice as much stuff.

http://www.jensen-transformers.com/as/as032.pdf

http://www.jensen-transformers.com/an/an004.pdf

[luvdunhill]

Balanced != Bridged. Balanced has no signal ground. The benefits to a balanced topology are many, while the benefit to bridged, at least in headphone use, is that the manufacturer can sell twice as much stuff.

yes siree.. now, what about 3 ch. topology, that implies the manufacturer can sell 1.5x as much stuff?

[Beefy]

Balanced != Bridged. Balanced has no signal ground. The benefits to a balanced topology are many, while the benefit to bridged, at least in headphone use, is that the manufacturer can sell twice as much stuff.

So is this preamp in question balanced or bridged?

[kevin gilmore]

The preamp in question is both balanced and bridged.

It will take a 2 wire balanced input. It will take a 3 wire balanced input.

It will take a 2 wire unbalanced input.

It will output both 2 and 3 wire balanced output. And 2 wire unbalanced output.

Same as krell and ayre, and levinson.

The T2 will take a 2 wire balanced input. But because there are only balanced input

connectors, pin 1 is connected to signal ground so that you can supply an unbalanced

input.

Clear as Mud!

[kevin gilmore]

Balanced != Bridged. Balanced has no signal ground. The benefits to a balanced topology are many, while the benefit to bridged, at least in headphone use, is that the manufacturer can sell twice as much stuff.

Except when bridged is used as balanced.

Lets take the input of the T2 for example. The two hot wires both go to seperate deck on the attenuator.

The other end of each of the attenuator decks is ground. Therefore a truely balanced 2 wire input signal

coming from a transformer has both wires referenced to signal ground thru the resistance of the pot.

Now the T2 also as a switch that can tie pin 1 to signal ground. For hum and noise reasons signal ground

IS NOT chassis ground. Chassis ground is strictly tied to earth safety ground. If you want to you can drive

the T2 with an unbalanced signal by using one of the neutrik unbalanced to balanced converters. In which

case rca ground is tied to both pin 1 and pin 3 inside the connector. For this you have to set the switch

to connect pin 1 to circuit ground.

The same thing is exactly true for the input of the preamp.

Now the output of the preamp should be considered as a bridged output referenced to signal ground.

In which case only 2 wires are needed to drive the input of a transformer.

The problem comes in with the input compliance with respect to ground. In this case chassis ground.

transformers are good for at least 100 volts of compliance, most solid state gear can handle less than

15 volts of compliance.

the RSA protector for example is a bridge output amplifier.

Edited April 5, 2010 by kevin gilmore

[Craig Sawyers]

Clear as Mud!

[kevin gilmore]

how i hate photoshop. If anyone has any better ideas to take a multi sheet pdf and stack the pages

with some transparency to make something that shows up without being 10mb...

http://gilmore.chem.northwestern.edu/baseboard3-1.pdf

[nattonrice]

Oh shit

I am so in on this.

[Craig Sawyers]

how i hate photoshop. If anyone has any better ideas to take a multi sheet pdf and stack the pages

with some transparency to make something that shows up without being 10mb...

http://gilmore.chem.northwestern.edu/baseboard3-1.pdf

I'm getting hot and sweaty about this damned thing already. Only comment - given the legendary resolution of the basic Curl design, the mute relay needs careful consideration.

[Kerry]

how i hate photoshop. If anyone has any better ideas to take a multi sheet pdf and stack the pages

with some transparency to make something that shows up without being 10mb...

http://gilmore.chem.northwestern.edu/baseboard3-1.pdf

You might try using the save to web function in the file menu and save it as a gif file. Much smaller output.

[naamanf]

You might try using the save to web function in the file menu and save it as a gif file. Much smaller output.

I think Kevin likes using large files for those poor chaps without a good internetz connection. Which would be me right now.

Count me in though, because other than build something for SWT61 all I have to do is move sand around the middle east for the next year.

[swt61]

This looks like a totally badass preamp. Wish I could hang with the big dogs on this one.

[grawk]

seriously

[kevin gilmore]

better at 1.7mb

http://gilmore.chem.northwestern.edu/baseboard3-3.jpg

bigger at 6.5mb

http://gilmore.chem.northwestern.edu/baseboardpro.pdf

both smaller than the above version.

Now for the important stuff. charles hansen says he found a non-multiplexed vacuum fluorescent display

for use in his preamp, he says it generates way less digital hash. Which certainly makes sense.

Anyone have any idea who makes his display. its 1 line of 16 characters, and is VF.

Power supply coming along nicely. lm317/337 in first stage, same thing as current limiters in second stage, third stage will either

be series regulated, or shunt regulated, have not decided yet.

All the resistors will be the surface mount thick film, vishay or equivalent, completely non-magnetic and non-inductive.

(and not super cheap, but not super expensive either)

[deepak]

Kevin, will this preamp have problems driving long lengths of cable (about 30 feet)? Assuming low output impedances on source and 100k input on solid state power amps.