Kerry

Nice work getting the beast up and running Peter

Looking really good Thanks. EDIT: Looks like a balanced dynalo. I've always wanted to do one this way. What transistors were you thinking of?

Nice work!

Great sleuthyness

In the T2/Blue Hawaii amps, the current source is tied to the anode of the output tubes which flows pretty much right to your ears. Seems like the CSS can definitely impact the final result. If I were to speculate, the CSS's job is simply to provide a constant current against the fluctuating voltages produced by the amplifier. If it does this one thing well, then you are mostly hearing the amplifier. If it does it poorly, then I'm less sure.

Thanks. I made the umbilicals 30" each so the amp can sit side by side or on top of the power supply. The amp powered on fine, but because I was using the PRP resisitors in the active batteries I had a noise issue. My suggestion is to use the Xicon resistors for the active batteries. Beyond that just really tripple check your work. There's a lot of parts in here and they all need to go in correctly.

I'm just putting the finishing touches on the T2 so here are some shots... Here's the coupler I made to join the 1/4" shaft for the volume to the 8mm shaft on the RK50. Here's a couple of shots of the amp I've got some JJ's in it now, but I'm going to try the mullards next.

Nice idea. I like the look too.

Yeah... 10A is a bit overkill for the LV

Nice. I love your collection of headphones. I'm very interested in your DIY phones.

There is another fully functioning T2 in the world I had to spend some time replacing resistors and getting the second channel working again. I had shorted out the battery while I was testing a month or so ago. I replaced all the sand in the one battery, 4 2SK216's in all and the protection zeners (100V). Good news is that even though the zeners died, the 2SJ79's were all fine. I adjusted the voltage across the 22K resistors in the batteries to 6.55V first with the 2K POTs centered. Then I ajusted each battery to 740V with the 10K POTs. I didn't need to further adjust the 2K POTs since it was really quite already. The servos are working nicely. The + to - differnce is mostly under 100mV and the outputs with respect to ground sit at about 4V for the left channel and 14V for the right. All good. The really story is how great this amp sounds. I did some comparative listening with the Blue Hawaii and the T2. There is a striking difference and it is really remarkable. The highs sound more extended which really seems to open up the sound stage. The bass is very tight on the T2 and it has really great extension and slam. I was listening to some high def Dianna Krall (Quiet Nights). I was so in the music that I couldn't stop smiling. I've got a few mechanical items I need to address (screw holes misaligned, etc), but I will have this baby polished off pretty quickly. I'm excited to get the second channel of my Blue Hawaii / T2 combo amp working. The first sounds great, but you really can't tell until you've got stereo.

Great job. Congratulations

I had the volume set down all the way. I also tested it by turning off the source with the volume half way up. Sounded pretty much the same to me.

I just replaced R37, R38 which sit pretty close to some other PRP resistors and the noise is almost entirely gone now. I'm hearing some very slight static every minute or so at turn on and slightly more frequent as it warmed up. I'm going to replace R35, R36 next. These resistors are only seeing about 185V each so it is no where near the working voltage but replacing them had a big impact. I'm starting to think that leakage is looking better as a cause for the noise issue. The noise floor (now that I can hear it ) is very low. With SR-404's it is bearly perceptable. On the O2's I really can't hear anything in the way of hiss or noise.

:prettyprincess: I replaced two resistors in the batteries and the noise is almost all gone (very, very slight now). When I originally did the build I used Xicon resistors for R39 (62K), R43 (390K) and R44 (390K) just because I couldn't get the PRP. The rest were all PRP. This setup had a lot of noise. I just replaced R33 (820K) & R34 (820K) with Xicon's (no other change) and the noise is way, way down! I think the relevant resistors are R43, R44 and R33, R34 since they see the highest voltage differential. Seems like the PRP were either leaking or breaking down very slightly. It's odd because the data sheet says they are good to 500V for the 1/2 watt version. Needless to say I am very happy! :prettyprincess:

Just realized there isn't a 490K for the Xicon. You can use the 487K or you can leave the 442K and switch the 20K to an 18K. Either will get you close to 500V.

The zener voltages are fine. On the board there is a resistor string that is 440K - 440K - 20K. That is setup for 450V. If you want 500V it should be 490K - 490K - 20K. It forms a voltage divide against the 10V reference so that the 490K - 20K junction should be 10V as well. Good news is the supply is working fine, just need to change the setup a bit EDIT: This has to be done for both the positive and negative rails.

I have the PRP resistors lifted by about .05". That's less than half of what Kevin was recommending, but the solder mask should provide a barrier as well. I've ordered the Xicon resistors and will change them out next. I would always recommend lifting the resistors off the board for high voltage applications. That being said, I believe the noise issue here is very specific since it is amplified by 113 and then again by 1000. Microvolts here become big issues.

I checked the 3675's for the batteries before I put them in. I picked ones with higer hfe (70 or so) for the batteries. What were you looking at when you measured these transistors?

I tried most of the circuit changes that Inu suggested to the batteries and still had the noise issue (didn't remove the 2K pot, RV1, from the circuit, but i did completely remove RV2 and used fixed values) - I'm using PRP resistors. I've got some GR grade 2SK246 that I'm testing separately first. I'm going to put them in on one channel. If that doesn't work I'm going to get both Dale and and Xicon resistors and replace them out in the batteries. I prefer the Dale as well, but it seems like a bit of experimentation might be in order here. Thanks to Blubliss for posting his results.

Nice work on the PS's Horio! I llike to duck under the table with a voltage meter tied to the outputs when I first turn a new build on EDIT: Just looking at the photos again, I can't tell if you have insulators mounted behind the output fets.

Looking good

Looking good

Wow... That was fast. I asked to be notified via email from BDent. I got the email this morning and checked availability. They still had some available.

Thought you all might want to know that BDent has the 2SK216's back in stock.