Kerry

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?

Newark has a few (about 30) just to test with.

The posted files did not have the oscillation issue, so your right, everything worked correctly. I left in some of the adjustment for the Bias voltage (pre regulation) with R25, R21. You can keep this voltage in a safe range (not for humans) at around 700V. These values could be adjusted for different PS uses (KGHB, KHSSHV, etc). The 2.6K load was based on the BH 400V / 150mA. I've added a 100V zener for protection and tested in spice. It works well. I could lower it to 91 volts. Here is the updated schematic and LTSpice with the addition of the CRD (thanks for the help on this ) and protection zener. I like this version much better because it will work with a variety of input voltages without adjustment. The only trick is that it will only regulate over about an 85V range, which should be fine. In my case, for a 400V output, that is 415V to 500V. lower and it doesn't work (420V is more stable) and higher and the zener will kick in - I tested this in LTSpice and it works well. I think that by adding back R5 (referencing schematic per my first post) and adjusting for different voltage inputs you could increase this range.

Cool This is what I was thinking for the power supply and bias. I used the voltage doubler from the original BH PS and just bumped some of the cap values to accomodate the load required by the zener string. With this I can use the same transformer from the original BH design. That should keep the heat from the pass fet around 7.5W +/- 3W or so. Here's the schematic (just the positive rail and bias): image removed at the request of Kerry I ran it through LTSpice and got this: image removed at the request of Kerry Any thoughts? I'm not above being silly; but what's a CRD?

I love this idea I modeled this in LTSpice and was playing around with the voltages, etc (wanted to see if it would work for the BH as well). I noticed when I reduced the voltage gap between the regulated and unregulated that I need to drop the values of R1 and R9 (I'm guessing to increase the current on the collector of Q3 feeding the pass fets) to prevent an oscillation. Did you see the same thing and do you think this is a good idea? Also, did you consider replacing the 2SC3381 with something less expensive (not that it's terrible)? I see on the silk that you were allowing for two individual devices.

That's really nice! Can't wait to see it completed.

Definitely want in on this. One board set and a handful or so of the 2SA1968.

I agree. I use DipTrace and put the spice info into each component export the net list and then load and run in LTSpice. I was able to simulate the Blue Hawaii like this. The only issue was getting the 2SJ79 to simulate correctly. I got it close in the end. A nice benefit of this is that the schematic is tied to the board layout and tied to the spice model so you know that you have things connected correctly.

I've been away too long working on a CNC machine. Birgir that is an absolutely beautiful chassis! Beats anything I had in mind. Kevin - that looks scary ... but fun!

Agreed. My understanding is that all the orginal boards / cases were spoken for, but we need to get that from Kevin. There was a conversation regarding an additional run of boards, which Kevin said he wouldn't mind doing. That brought the heat sinks up as the major stumbling block. If we can solve that (and Marc this looks promising), then I think the world may have some more T2s.

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

I have to say that you have the coolest toys

Were you able to use the thicker ceramic insulators without having to re-solder the devices? It seems like you were just able to re-bend the leads a bit to get them to sit right. I love the black nylon screws.

What about Glass Filled Nylon. Here's one at McMaster-Carr. Search product 91221A220. They don't come in 4-40 so you'd have to use 6-32, which will work with everything except the 2SA1486 devices. They have an operating temperature range from -40 - +230 deg F. I don't see there electrical properties listed, but I have used them on the Blue Hawaii.

I have a bunch of 4169G and 4180G pads. They are really nice, but the widths are more than .5", which is the mounting width of the devices. It's nice to know that the 4171G will work. I cracked one by over tightening, so you have to be careful. I think I will order some of these as well. Not sure on the voltage rating of the glass filled PPS screws. I do worry a bit about the temperature limits (around 185 deg F for the ones I was looking at). Shouldn't normally be an issue but in a hot room it starts to get close. Great idea on the current limiting supply!

:) :) Very cool stuff here! A KG designed balanced DAC - This is going on my list of things things I can't wait to build! Nice work Inu. A question on the spacers - I see the need on the hotter resistors, but are they needed on the diodes?

Nice job Birgir! I'm in awe. Red is cool Anybody close to firing this up yet?

Wow Very cool that you have access to stuff like that!

Yeah, I don't know why it is so painful to solder the umbilical cords / connectors. Very nice job though

Here's another seller that I've used. They have reasonable selection of hook-up wire if you poke around their store. 20-AWG Mil-Spec Wire 9-Colors 10-Ft-Each, 90-Ft-Total - eBay (item 230414847920 end time Jan-19-10 15:49:38 PST) I've bought some 22-awg silver plated hookup wire from them recently.

Wow. Just beautiful. Looks like a long weekend ahead

Looking absolutely awesome. I just noticed how many holes there are in them boards. That'll take more than a few nights to stuff I expect the results to be well worth it

Looking good. How are you connecting the chassis earth? Through ground or a separate connector.

That's is going to look really nice. Are the front and back plates extrusions as well or did you mount some angle on them?

Very nice! What's the dimensions on the chassis?