xchagg

You might need to change R2/R3 if you're using it with a portable source. The standard values give a gain of 2, which is a little on the low side. If you're using the SR60s as your portable can, a gain of 3-4 should be sufficent. I built my CMOY2 with a gain of 2 and it was perfect with IEMs, but a slightly higher gain would still have been preferable. A gain of 2 isn't enough for high impedance phones like the Senn 650's though. They still sounded good, just not loud enough Another suggestion would be to remove the input caps (C1&C2) and jumper them for improved bass. The input caps help block any DC offset in your source from frying your phones, but they can induce bass roll off, unless you chuck in a bigger value film cap like 2++uF, which isn't quite possible given the small space.

I think Gary offers a lifetime warranty on the PA2v2, so if all else fails just send it back for repair

Hahah, yes you can. It was discussed in on headfi in fact, but the opamp needs to be able to run on 3.3V from the regulator, which limits your opamp choices severely. And my solder skills aren't good enough for SOIC parts. But somone else who has a Transit, better soldering skills, and itchy hands can do it hehe.

ugh, more expenditures lol. I'm overseas studying, so having to rebuy all the DIY equipment is not . . . appealing haha. Though yup, forgot the easiest way to test is with a multimeter doh. And yup I seem to have a liking for big caps in small places Stuffed 2 BG 330uFs into a CMOY2 lol. One cap is enough to cover the entire middle row of resistors hehe. Though someone barely managed to stuff a 470uF BG cap into the Transit case, I didn't want to take that chance and went for a smaller cap this time.

The Transit is quite decent if most of your music is on a computer and can't afford a proper DAC heh. So one day hand itchy, (and after reading a post on head-fi) and decided to mod the Transit lol. I replaced the 2 cheapo output caps with NX 22uF BG caps, and the power capacitor with a 220uF BG STD. Well the sound hmmm, much more detail coming through, less muddling of different instruments and voices (better seperation?). In all a noticeable improvement. The caps are brand new, so hopefully they get even better with time, but I'm already satisfied Just a few questions though, my soldering skills are still lousy, so I had some problems and had to improvise a bit. 1. The leads for the Black Gate 220uF were too big to go through the holes, so I put 2 blobs of solder on the pads, positioned the capacitor, than reheated the solder blobs and added a bit more so that the cap would 'stick'. Essentially the cap leads are just connected via solder to the pads on the top of the board as they couldn't fit through the hole. Will this cause any major problems? 2. More concerned about this one: I had some problems replacing the new output cap on the top left corner. Didn't have something thin enough to poke through the holes, so they were slightly blocked. I somehow managed to stuff the capacitor leads partially in, then added more solder on the other side of the board. The leads didn't go all the way through, so they're kind of stuck in the middle of the board. The cap couldn't be pulled out using pliers either. Is there a chance a proper connection wasn't made and that pad is sort of shorted? The Transit is working properly, but I'm afraid if the cap is not properly seated and not doing it's job, than the DC offset might damage something. Some Pics: Original Board: Butchered Board: Close up of output caps on lineout: New Big Power Cap (Yum!):

OT, but i guess I'm starting to miss home a lil now I first saw this post on Head-Fi. Didn't realize it was a local review until I re-read this post here and took a closer look at the photos. The classic old-style pattern wood floor, familiar power sockets and the anti-cockroach pads haha. And the POPULAR files and UE Square haha! God I HATE the 3-hole punchers in the U.S Wonder if I can demo the RS-1s sometime in the when I pop back during holidays in the distant future hehe...

hmm, look familiar anyone? EBay CMOY2 Since when is the 2134 superior to the 2227, I always thought it was the other way round heh. Could be mistaken though

the transistors, opamp, trimpots, have to get from farnell i believe. Could try placing an order through Federal.

The caps I orginally put in were Nichicon Fine Golds. I swapped them out because one day the amp suddenly brightened. I don't believe it was due to a placebo effect, cuz I was waiting for the MRT when the sound suddenly brightened mid-song. I didn't like the change, so I swapped out the caps lol. To be honest I don't think Black Gates make much of a difference in this circuit. They're just fun to to use But swapping the caps did make the sound return back to normal (i.e. no more over-brightness) And black gates take several hundred hours to 'burn-in', so I don't know if the sound will change again. Probably won't make much difference in the CMOY2.

In the U.S. Boston to be exact.

The Millet-Hybrid Amp. Thing is I'm overseas for studies, and having to rebuy all the equipment again is . . . painful lol.

Wanted to use the BGs for a Pimeta, but didn't have time to build it, so just swapped caps in the CMOY2 and put the other 2 in the MINT. Used Switchcraft jacks in both amps, very nice build quality. The metal barrels of the look-alike ones from Koba tend to detach from the main body if you twist them around too much lol. Thining of going tubes instead of SS for my next amp. Looking at the MAD Ear+Purist HD, but that's one nice chunk of change But I think I should get a Headroom MicroDAC first; Currnet source is the headphone out from laptop. It is suprising good, even better than my Iriver, but there's all the electronic background noise ugh. Putting the signal through an amp cleans it up, but the noise is still present ... But the glow of tubes is sooo alluring....

Pic shows how I laid out the front panel. 1st DIY amp so forgive the mess heh. Ugly, but functional. Putting the switch in front of the LM6171 was a very tight fit . . . if the hole you drill for the switch is just a bit too low, the switch will push the IC out of the socket when you case it up. I went through 3 Hammonds before managing to case it up properly :s Also remember to give clearance at the sides of the front panel for the screw posts. I destroyed my 1st Hammond by putting the switch too far at the side lol. Couldn't close the case up. Another thing about audio jacks at the sides. The material at the sides is much thicker, so the audio jack barrel is a little recessed. You might not be able to always get a good grip btwn the jack and plug. Mine works perfectly, but if I pull out the audio plug just a tiny bit, the right channel goes. The Go-Vibe v2 solves this by removing a small square of plastic on the inside of the case, but I have no idea (nor the tools) to do this. You could try it though. Maybe a chisel just might work Added pic of the Go-Vibe where part of the plastic is removed for the audio jack:

I ordered twice from Farnell around June/July. Both times bought ard $35 worth of parts. Delivery was free both times. Ordered by web btw.

Order $30 worth of parts from Farnell and they'll deliver to your doorstep. Some of their stock is in Europe/US so you might have to wait ard 5 days. Better to order via phone/web if that happens. I think Federal @ SLT also handles Farnell orders. But same, if no stock at hand, come back in a few days hehe. If you nd some AD8610/8620s, MINT/PIMETA/PPA PCBs, volume pots you can try Tangent Audio. Ordered twice from him already, no problems. http://tangentsoft.net/audio/shop If you're feeling crazy and want to try some BG Caps (excellent & expensive ) Ordered once before, no problems: http://www.kyoto-electro.com/index.html

The OPA2228 is a fast IC, so that might be causing the oscillation problem. The OPA2134s are slower, so if it's the 2228s causing the oscillation than your problem is solved. Also, have you tried removing the LM6171 and shorting pins 2 & 3 to see if the oscillation is still present? Just a shot in the dark haha, but that's one of the things I tried when troubleshooting my CMOY2. Turned out I snipped off the ground pin on the audio jacks by mistake so my IG and OG signals were going nowhere lol.

Got the tupperware from Jason's supermarket for $2.80. It's the smallest size available i think, other than the round tupperware. And much cheaper than a Hammond After I decided to put the amp in a tupperware, I swapped the elec caps for something better hah. Might as well utilize the extra real estate. Oh yea, didn't way anything about the sound. LOVE it hehe. Sounds slightly better to me than the CMOY2, mainly the expanded soundstage. And more detailed, prob due to the AD8620 vs. OPA2227s in the CMOY2. It is WAY better compared to the Go-Vibe v2 w/AD8620. Lots of detail, and sounds a lot richer and less 'trebly' than the Go-Vibe. Probably the buffers at work there. Too bad the tupperware is not pocket friendly, so the CMOY2 is still my choice for amping on the go.

Took me awhile, but I finally got around to casing this up. Ran out of time to get a proper Hammond (went overseas), and couldn't figure out how to make a hole big enough for the volume pot witout destroying an Altoids tin, so here's my own MINT (Meta42 In A Tupperware ) Some pics, this is my first digicam, so they aren't very good heh. Shot of the Innards: External shot, cover off: External shot, covered:

A couple of questions: Does using premuim capacitors for the power supply capacitors influence the sound? Cause I used those Nichicon FineGolds in my CMOY2 and after around a week (avg 4hrs per day), the sound suddenly became brighter, as if the treble eq had been bumped up a notch. The change was quite sudden: was waiting for the MRT when I noticed something funny with the sound haha. WRT using electrolytics instead of film caps for input/output?? decoupling, would this be like using a good quality electrolytic, e.g Black Gate N-series for the C4 cap in a Pimeta? Or the C3, C4, C5 in a CMOY2? (hand feeling itchy already haha). And finally what exactly is the function of the input coupling cap and output coupling cap? Input coupling: Blocking DC offset? Is this cap usually in the audio signal line? Output Coupling: umm, no idea Is this cap usually in the audio signal line? Thanks.

Erm just a couple questions about the design of the CMOY2? 1. Is this considered a 2-channel or a 3-channel design? 2. What is the function of the LM6171? As a ground channel, or some sort of voltage splitter or VG? 3. Is voltage splitting accomplished by the LM6171 or by resistors? 4. Would a BUF634 work in place of the LM6171? No cheem terminology plz, still a newbie at audio stuff haha. Thanks.

ah well, the pot in question is back in stock at Tangent so no need for alt pots . . . Again, is there a local source for the Vishay Dale RN55 series resistors? And if a Tupperware is used as a casing, is there cause for worry of static electricity buliding up inside the casing and frying the ICs? Thx.

Hi, I'm thinking of building a PIMETA next. Tangent is still out of the RK097 pot (the one with built-in switch). Are there local sources for this particular pot? I found something similar in RS, but the manufacturer number doesn't quite tally. Can someone take a look and see if they might be the same pot? The correct manufacturer's number should be RK0971221Z05, but is listed on RS as STRK09707. RS Stock No.: 249-9159 As for the case, which of the following Hammonds would be a good size case to fit the board and 2 9Vs or 12 AA/AAAs? It's not meant to be portable, but I don't want too huge a case sitting on the desk. Hammond Cases Other case suggestions are welcome too, as long as it's plastic. (Drill not good enough haha) On a side note, I managed to properly case up my CMOY2, LM6171, LED and all (on the 3rd Hammond case lol), except i screwed up the volume knob positioning. Is there a way to remove the volume knob from the shaft and reposition it? I was considering heating up the knob, dunno if it'll work though. Thanks. EDIT: One more question . . is there a local source for the Vishay Dale RN55 series resistors?

an update: Finally got all the parts I needed to populate the board. (Digikey and vPOSTUSA shipping was a killer . . . if there is a local source for the Panasonic EVJ-C20 pot I'm really going to smack my head HARD lol, but I was lazy ) Hooked up some wire and croc clips to test it out and it's working beautifully. Though I had to spend around 10 mins b4 finding out that i needed to jumper the switch pads if there isn't a switch installed. Was wondering why there was power only at the V+ and V- pads but nowhere else Thanks again Jason for the solder assist

thanks heady. Think I'll stick to the standard pot and put it in a different casing. Mmm . . tupperware anyone? More wiring = more things that can go wrong. Though the thickness of the plastic is a pain to drill through with a battery powered drill As for the 1st CMOY2, it'll have to do without a LM6171 lol.

Hi, Any idea if the ALPS RK097 volume pot as listed in Tangent's Audio Shop can be mounted directly onto the PCB? Reason being I'm having trouble fitting a switch/audio jack near the audio output jacks as there's not enough clearance with a socketed LM6171 installed. After casing the amp up in the Hammond one end of the LM6171 tends to get pushed out of it's socket by the audio jack/switch. Soldering the LM6171 directly to the PCB probably would give enough clearance for a jack at the spot but I risk frying the chip... Also, if the pot is changed to the RK097 (10k), do any of the resistor values need to be changed? Thanks.