Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by FlySweep, Nov 2, 2015.
I forgot the thermal grease on the regulators. Before unsoldering everything I ran some sims. The B+ MOSFET runs at about 2.8W, and the 6.3V heater regulator at about 3W. A quick google turns up an Infineon doc on TO-220 FP mounting which gives an Rth improvement of 1.2 to 1.5 K/W for thermal grease -- so we're talking about a delta of less than 5ºC for the 6.3V reg.
I did thermal grease the output stage BJTs.
Some real-world measurements:
B+ MOSFET case temp: 42ºC
B+ MOSFET heatsink temp: 30ºC
output transistor case temp: 70ºC
output transistor heatsink temp: 62ºC
output CCS case temp: 70ºC
output CCS heatsink temp: ?? (not a big enough flat target for my IR thermometer)
So we can see that no thermal grease results in a delta of 12ºC, while thermal grease knocks that down to 8ºC.
Overall the temps seem well-enough controlled for a tube amp. I like to target 60ºC for solid-state, but then I leave those on 24/7 so longevity is more of an issue.
Had a minor setback when I went to attach the front and back panels and realized the case holes weren't tapped. So it's all got to come back apart again so I can clean the swarf out after tapping.
But before I do that I thought I'd see if it was worth all the fuss. I'm not sure what I was expecting, but certainly not that. Wow.
All I've compared it to so far are two-channel setups, which is a bit apples and oranges. But, FWIW, it handles congestion better than my F3, and its attacks are notably punchy (though not as sharp as my F5). Not as sweet as the F3, nor as clinical as the F5, but closer to the latter. Imaging not as good as my Cronus Magnum & Maggies, but that might be more of a cans vs two-channel observation.
One other note: I get some capacitively-coupled noise when I touch the volume pot shaft. This is probably due to insufficient grounding because the case is anodized. I'm hoping it goes away when the (similarly anodized) volume knob goes on. But as long as I don't touch anything it's dead silent through HD650s.
@JeffYoung So glad to see you have it completed finally!
A very neat build.
I sure hope it's not just you, Jeff, and me... That's gonna make it real hard to find a frame of reference if my T3 ever dies and I need to replace it! I'm still really happy with it, bought it for the HD 600 (which turned into modding a 6XX) and it actually helped me figure out what I wanted from future headphones. I moved on to the Aeolus and it's still rocking w/that.
I went in kinda blind since I hadn't tried very many tube amps, I've gotten to try a few lower end ones since and I think the T3 still hits a sweet spot... Maybe I'll move on someday, but it still fits my needs/gear nicely and I even like how little desk space it takes up.
I'm about 1/2 way through a DIY clone of a Pass HPA-1. It's all solid-state, but like the T3 it's a single-ended differential circuit, so it should be interesting to see how they compare....
Looking forward to seeing how it is compared to F3 and T3. Is the schematic available somewhere?
*on a second thought, F3 to HPA-1 are just like apple to orange.
The schematic has not been published, but Jam and Wayne at Pass Labs gave us some pretty good clues: https://www.diyaudio.com/forums/pass-labs/300060-pass-hpa-1-a.html .
You can also work out a lot of the values from the pictures in the 6Moons review.
The one thing I couldn't figure out is the control logic, but then I'm not going to program a PIC for it anyway (and I don't need remote control), so I just went with something simpler there.
Kinda late to the party, but I finally got mine. Some time ago posted a WTB where I was looking for unfinished Torpedo 3 projects. I myself have a few grand of frozen assets in unfinished audio electronics and I figured I could help some poor sod out exchange guilt into hard cash. Some people offered their finished Torps, but that was not my plan and I got a dead Torp from @MisterRogers who had pimped it to death and now couldn’t find time to nurse it back to its former glory. It had all the bells and/or whistles - CCS’es, Mundorf caps and even a Belleson discrete reg. Also it wasn’t working. I’m not an expert in electronics, but generally it’s hard to kill anything that’s expensive on the Torpedo 3 BOM. Tubes and trafos shrug off electric damage and all of the silicon on the Torp can be bought for pennies, so I could just replace everything. So I sent a PP payment and sat tight.
Fast forward 3 weeks and I got the package. Prolly the post people thought I’m buying some expensive booze by the shape of the box. Everything was packaged more than fine. There was a close call with the pot shaft piercing one of the tube boxes and missing it by a hair. Otherwise everything was cool. I popped open the case and everything looked kinda ok. @MisterRogers did tell me that he’s blaming cold solder joints, so I investigated them. Everything was “good enough for army work”, but four kinda weren’t aerospace grade and I reflowed them. Also changed the PT jumpers, so primaries are good for 220V. Now for the first power up. Flicked the switch and started listening for pops and/or heat effects, at the same time sniffed the air for burning or heating up. Felt the heatsinks with my finger and everything was heating up as expected. The MOSFET that regulates B+ wasn’t too hot, so I felt that it’s necessary to see wether this voltage is up to spec. It was. Now hooked up a pair of sacrificial headphones and listened for noise. Nothing. Measured voltages on RCA’s, so I don’t kill my DAC. Hooked it up. Pressed play. Music!
The test system:
Windows 7 PC
Sonarworks Reference 4 individual calibration
Soekris dac1541 (USB/0dBFS volume/1st level x-feed/2nd LP filter)
DIY silver plated copper RCA IC’s with Neutriks
Torpedo 3 - CCS’s/Belleson reg/Mundorf caps/Cinemag OT’s/ stock EH tubes
Neumann NDH-20 150 Ohm dynamic closed back headphones
Mount Gay Eclipse golden rum mixed with coke and lime
As you know I’m kind of a stickler for good engineering. I will bash shoddily designed and built gear. I don’t really lust for -130dB distortion, but it makes me appreciate the effort of the guys behind such a device. So I’ve kinda overlooked tube gear. Until about 3 months ago I bought a Marshall DLS40 tube combo. So, I thought, why not try out fire bottles for headphones?
My main amp so far has been the Schiit Jotunheim which I now going up for sell. It’s good SS amp, but Torpedo 3 makes me stay up for one last album way more often. It’s like looking at an LCD on a camera versus the ground glass. One is a decent hires image, while the other looks like magic. I am able to hear more subtle details with the Torp and the general image is more layered. The Joti also had a bit of a leaning towards harshness in highs at higher volumes. Can’t say whether that’s truthful or not, but Torp 3 just goes louder, without getting annoying.
So yeah, Torpedo 3 is here to stay. I don’t have any other tube amps for comparison, but I haven’t heard as good SS amps so far. Maybe I’ll dip my toes into rolling tubes. I’ll hook up my RME ADI-2 Pro in the following days. Can’t imagine my impressions to change much. Maybe in the future I’ll build the Neurochrome DG300B, I did by the last boardset.
I highly recommend that people check out Torpedo 3. And good job @dsavitsk on the design!
How well do you think it matches up with the 1541 @Hrodulf ? I've had my eye on the latter...
The T3 is a bit on the romantic side, but as far as R2R dacs go, the 1541 is one of the least warm. So I'd say it's a good match. If you don't need BAL, then dac1421 might be a better choice.
The T3 responds pretty well to fine tuning via tubes. @TomB has posted some in here that are a good balance of price / performance (CV4024) - I think the price has doubled since I purchased them last though.
It appears I'm the only person left who hasn't dumped "pull-up-pampers" T3 for some big boy amp. Anyhow, rolled in some Brimar Yellow T CV4024s and so far I'm very much liking some added roundness and body without losing any HF extension or openness from the GE 12AZ7s, using HD800SDR. That is all.
It is just a matter of time
I finally got a Yggdrasil A2 to let my Torp 3 flex its muscles. It's pretty hard to get any of the big boy amps here in EU, unless one wants to pay silly money.
Separate names with a comma.