Kerry

Also, if you use SMD parts, you'll have more space because you loose a lot of through holes and can better use both sides of the board. If you did this it might fit better. Also, you can stack a couple of boards (one for left and and one for right), thought this is not as optimal.

It would be nice to have a board that would would fit into the standard balanced POTs used for the T2, etc using some sort of pins and would mount above the amp board. A simple plug in. The board would also have a ribbon cable for the I2C control stuff. Not sure if the size would workout, but it would be nice.

Beautiful job Birgir I like the idea of using an SMD resistor for the PS fix, though I'll stick with the standard one for this build since it's already cut this way.

Here's my progress on the power supply. I'm waiting on a couple of caps, but I've got most of the other components in. I'm going to mount this onto the rails and start populating the sand tomorrow. I've left this full size so you can see the fixes (reverse diode on on the neg 12V supply) and the 30V zeners instead of the 1N4007's. http://img864.imageshack.us/img864/9232/t2ps001.jpg I've also left out the 2SC3675's so that I can use the emmitter lead to apply the patch to the bottom of the board. Here's a shot of the cut trace and I've also removed the solder mask (I used a 1/8" end mill on my drill press for this) on the traces so that I can use it to mount the resistor and one end of the .1uF by-pass cap: EDIT: I also replaced the rectifer diodes because they were no longer available with these: DSEP12-12B also a number of caps were no longer available: 220uF 250V caps with these: ECO-S2EP221BX from digikey 100uF 450V caps with these: ECO-S2WP101BA 680uF 450V caps with these: EET-UQ2W681EA

Very cool I was thinking of adding some local feedback on the output stage to keep the gain to about 10x (on the output stage). This will help keep the gain on the drains of the input stage closer to 1x amplification. Right now with all the negative feedback it is really low (hard to measure even on the scope). What do you think? Did I mention this is very cool!

Likewise, sorry to hear that. Let us know when you track down the issue what cause it. I should have the boards populated next week and I will be putting in the transformer order tomorrow, so I should be able to start testing the supply pretty soon (baring any forgotten components).

Here's a new amp I just did based loosely on the T2 topology. I was trying to meet a $69 challeng. Close, but fun just the same. I built it for the NYC head-fi meet have a picture of it here: Here's the schematic for it. Sounds pretty good, but there's a bit of tweeking I need to do. I think I'm going to raise the power up a bit (currently 250mA per balanced leg). The heat sinks will take it, but I need to modify the power supply a bit. Thanks to Kevin for his pointers

Don't worry. I've got a build that I've got most of the parts for and am just getting started. I think there are a few others that haven't finished their builds yet. But yeah, I have to believe that most are blissfully listening to their T2s. Regarding the angle brackets, they are currently boxed up, but I can get exact measurements next week. I think they were 1.5" x .73" and approximately .33" from the edge. They are not typically tapped and the hole size I use is approximately .132". Sorry I can't be more precise at the moment. Is that 5" horizontal per heatsink or for two? Sounds massive

Congratulations

Welcome back Great information! What are the diameters / heights of your transformers. I'll keep those limits in mind as I put the specs together for SumR. Thanks.

I was just about to pull together the requirements for the transformers. I'd be looking for a significantly lower temperature rise. The last transfomer I ordered from SumR, we were able to get them made with a 22°C rise at full load. For the three transformers what were you thinking (power wise) for each winding? I think the most significant power is pulled by the Neg. 500V supply at about 33mA (per channel per LTSpice). I'd like to keep them as cool as possible so 4x seemed reasonable, which would put it around 133mA (assuming LTSpice is right). Here's the specs that Kevin gave so it's pretty close. Richard at SumR can take these and beef up the windings to accomodate the lower temp rise, but we need to make sure the size doesn't exceed 2.5" tall by about 3.5" wide (not sure on max width). I'd like to try to get the same specs as you if you are reordering.

The generator does support a DC offset of +/-10V. The rise time of a square wave is <20ns (@ 1KHz, 1 Vpp)and the square wave upper limit is 3MHz.

I just got this combo Scope + Function Wave Generator: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260729602293&ssPageName=STRK:MEWNX:IT It arrived a couple of weeks ago and I only just turned it on for the first time... just too busy these days. I'll post back on how I like it once I figure out how to use it

With my keen eye for reading subtle meaning from a post, I've guessed that you're not too happy with your ISP

The amp / PSU can be built however you'd like. Stacking is definitely an option. I may do one this way - it could be a very small foot print. I'm using DipTrace to do all the design work. I've got the not-for-profit version that supports 1,000 pins. I'll see about elongating the pad size. I know what you are saying. Given some of the issues around bad semi's rework is a real possibility.

Glad you're up and running again Craig. I've been having my own fun on another layout. I wanted do a layout for the BHT2E. Here's where I'm at... I wanted the board small enough so that I can do a single chassis for the PS and amp boards. It can be done as two units (PS & Amp) with the depth being about 8" or 200mm and the boards being 12" wide. Since the 100V (BH) supply is not on the amp board and the bias for the tubes was reduced from 25mA to 12mA, this should produce a lot less heat than the BH. I'll want to play with the current to see / hear the difference. It models nicely at 10mA - 12mA which is only slightly more than the T2 at 10mA. I'm using the T2 output stage and servo and have added a servo to the BH front end. Again, it models well but I've also kept the adjustment POT to keep the servo's job to a minimum. If it affects the sound, I can just pop the opamp out and go manual. Who knows if it will actually work, but it's worth a try

That's a nice friend. Very nice work on the boards and transforms.

Really nice. Thank you.

Thanks Craig - I see the value now. This solves one of the mysteries for me. LTSpice is also supposed to have an RMS calculator (Ctrl + right mouse), but it is not working for me.

Craig - Thanks for this post. I'm still a bit unclear in the calculation. I downloaded the duncan amps PSU Designer. I basically got similar results in LTSpice. On an active battery regulator in LTSpice with a 425V output, DC current draw of about 50mA and front end 340uF capacitance I'm seeing spikes of about 2.5A. I thought maybe to divide by 1.414 to get an RMS value, but that is still 1.77A. You mentioned needing to use 2 - 4 times the DC requirements (which seems right to me). If this is a pure average then I can approximate it around 3x - 4x. I did a quick scan on the web (looking up schade curves), but didn't see what I was looking for yet. I thought I'd lazy and ask.

Marc's right. I haven't added holes for the standoffs just yet. Also, the AC on this will need 2x 330VAC CT, 1x 140VAC, 1x 28VAC, and 1x 28VAC CT (not counting the filiment windings). This uses less power than the original BH, so I was thinking of doing it in one transformer. For the bias, it uses a similar doubler to the orginal BH, with a bit more capacitance, and then the IXCP10M90S against some zeners (same as the T2). It supports two taps out, Stax Pro for the higher and it has an option for what the lower one is (500V - for HE 90 or 240V Stax Normal).

Yes. I was shooting for a specific size on this board.

Here's some fun stuff. It's my draft for the BHT2E (per Inu ) power supply. It's got +425V, +15V, -15V, -295V (via 160V against the -455V rail), -425V, and -455V (via 30V against the -425V rail). The dimensions are 12" x 5.5". Once, I have this built, I may take a BH board and hack it up a bit to test the design. Any thoughts are greatly appreciated.

Really cool!

I forgot to knock down the voltage going into the opamp servo, but it is the same as on the T2. Model still works, though I'm not sure what would happen in the real world. I just added it to my model. I would love to get feed back on this. It's actually the T2 output and the BH input with servo similar to the vendetta / T2 for the input section.