NOTE: You can go to www.garage1217.com and download the manual (PDF) for the Starlight and the PS2 for free.
NOTE: A complete review of assembling the Starlight is not necessary here. For that, go the PS2 kit review. The Starlight is just the same. There were a couple of anomalies, which Jeremy responded to post haste. After the serial number of this kit is 00001.
On a whim, I picked some LEAD FREE solder try out. LET ME SAVE YOU SOME PAIN. It takes more heat and does not flow as well as 60/40 LEAD/TIN ROSIN CORE. Plus, you do not get that shiny finish to let you know that the joint is good (not cold). I feared that this might impact the performance of the amp but it did not.
The SILVER BEARING solder I looked at is only 2%--hardly worth the extra $$$.
I use the Weller WLC100 solder station with a conical tip. Just adjust the temp control (slightly below 4 on mine). Adjust until the solder flows through the pad to the other side. The price is this station runs around $40. If you plan to do much DIY, it’s worth the $$. The amp has 4 DIP sockets and the pins are fairly close to each other. The conical tip makes pinpoint soldering easy.
Each channel has four opamps driving the phones. I have not verified if all four are stacked (parallel) or a combination of series/parallel. I’m certain that Franz (Solderdude at the RockGrotto European forum) got it right. I will find out.
Rolling with just one on each side to verify rolling can be done with one to lower $$.
I am using a spare DIP socket to plug the opamp into and then plugging that in the PCB mounted socket. Purists may say extra capacitance, but that goes away after deciding which ones to use and it beats breaking and bending pins. I couldn’t really hear any difference.
With each one tested, I measured the DC OFFSET VOLTAGE. For those that don’t know what that is: any stray voltage at the input of an opamp will be increased at the output. That voltage goes to the voice coil of the driver and extends the diaphragm away from the neutral position. Over time that can damage the phones. An “acceptable” level is 20 millivolts. The average voltages ran from .5 to 5 millivolts—way below the upper limit.
Opamps tested: What I have on hand.
LM4562 (stock-comes with the kit)
BURR-BROWN OPA 2227, OPA2132, OPA2134: These have the “Burr Brown laid back sound kind of tube like sound.
JRC 4556: Yeah I know, the 50 cent Grado RA1 opamp. The idea is to test different brands. Suprisingly, it sounds pretty good when fed a better signal than a Cmoy. And considering that this one will output 70 milliamps and there are four in each channel, there is some considerable power there.
This offers a lot of rolling for little $$. And even if you make a mistake, the only thing that will blow is the opamp. The surrounding circuitry is very durable. Replace the opamp and move on.
I used a 12 volt 12AU7 for the first turn on (flawless-no smoke!) and then a then a 6 volt 6922. There is a 6/12 volt jumper next to the tube socket.
NOTE: The bias can be adjusted using the installed LEDs to display a high and low range setting for both channels. In this case, I am a purist and connected a DMM to the provided holes in the PCB and monitored the actual voltages while watching the LEDs. The HIGH LED bright is around 12.5 volts and the LOW LED bright is around 8V. This will be great for tuning discussions for biasing with different tubes!!
LED Under tube:
Unlike the PS2, this led is a single color. Colors available are white, orange, blue, red and green. It is BRIGHT, but there is a jumper next to it that allows turning it off. I went with blue.
I built both of these amps in the pictures, the PS2 and the Starlight:
You can save $35 by ordering the built unit. I am a seasoned electronic tech ranging from radio and TV broadcasting to computer networking. I took my time and verified everything twice (measured every resistor and electrolytic capacitor orienting) before soldering. Every bag was correct. The result was that BOTH amps only required tube biasing and the result was total success. There is a great gratification sipping your favorite celebration beverage (single malt scotch in my case) staring at the amp while running it through its paces.
Yeah, I know to the purists, that’s cheating. But consider this: The amp can handle ANYTHING I send to it in spades. Also, I can tune out headphone and recording variation deficiencies. In my case it is a 31 bands per channel.
Grado SR80i, SR225i, fully vented SR225 with Canare cable, Allessandro MS1,AKG K702 and 240 Sextetts-660 ohm. Both known to be finicky with amps.
I don’t presume to discuss SQ terms here. The point I am making is that everything works well and it’s a lot of fun experimenting.
Final comments on sound quality:
FANTASTIC!! Better than the PS2? I say no. Equal to yet different with a HIGH degree of tuning. With the high output resistance setting, running the 600 ohm Sextetts sounded great. They like power and the amp brought out their outstanding mids and soundstage.
AH-SO! Now the careful stuff is complete and I did not blow up the amp. Now is time for laid back listening, sipping Scotch and smoking the Easter ham and turkey.
Edited by rmouser - 4/2/13 at 5:06pm