I've just built up one of these using a kit from RJM (also built a sapphire) - thanks Richard!
Sounds great, although I need to go back and tweak the circuit for the 2n5486 that I had as I'm running out of adjustment on the trimmer. Anyway the thing is running a little underbiased but it sounds very good indeed. Big sound with very solid bass. I'm listening to some steely dan as I type this and the bass is absolutely rock solid on the k701s. I'm impressed!!
The sapphire is an excellent HPA too - either circuit is well worth building!
Fran
Sounds great, although I need to go back and tweak the circuit for the 2n5486 that I had as I'm running out of adjustment on the trimmer. Anyway the thing is running a little underbiased but it sounds very good indeed. Big sound with very solid bass. I'm listening to some steely dan as I type this and the bass is absolutely rock solid on the k701s. I'm impressed!!
The sapphire is an excellent HPA too - either circuit is well worth building!
Fran
http://www.diyaudio.com/forums/head...dio-sapphire-desktop-headphone-amplifier.html
Tell me more about the kmultiplier - is that extra capacitance?
Excuse my ignorance!
Fran
Tell me more about the kmultiplier - is that extra capacitance?
Excuse my ignorance!
Fran
Some numbers for mine:
V+ is 16V fed by a salas shunt. Bias at 5.5V (which stays steady once you do a final adjustment at working temp) and I changed R3 from 1.5k to 2.2k which allowed me to bring the bias up (I think my 2n5486 were a shade on the low side). Temp on the metal tab of the IRF510 is 45degC - which is ~25 above ambient. I'm more worried about the temp on the shunt heatsink which is sitting at 53degC now - and this will probably rise a bit more when the lid is on the box.
Its a joyous amp to listen too - really sucks you in a keeps you coming back, zero fatigue. Very powerful bass which just is grippy as hell - listening to some steely dan last night and the drums were just so tight, the ring from them was fantastic. Lovely treatment of vocals too - I'm listening to Terri Hendrix singing "The Dark" from the tribute to Guy Clark album and her vocals are lovely - warm, but detailed and no over-emphasis of sibilance. I'm really impressed with it!
Overall, I'd say the Sapphire is the cleaner more neutral amp and indeed it sounds great too, but I am developing a bit of a sweetness for the J-Mo!! I suppose the other thing is that the Sapphire is more of a universal amp in that it will take all impedances. However, you could do like I jsut have (inspired by the pic RJM posted in the Sapphire thread) and build both into the one chassis - that way you can use either!!
I'm listening to CDs, on a shigaclone, fed into a EUVL 9022 dac powered by LiFePO4 batteries and a JG filter/buffer powered by salas shunts and then to the J-Mo and then K701s.
Thanks Richard for the kits and advice along the way. Its a lovely amp!!
Fran
V+ is 16V fed by a salas shunt. Bias at 5.5V (which stays steady once you do a final adjustment at working temp) and I changed R3 from 1.5k to 2.2k which allowed me to bring the bias up (I think my 2n5486 were a shade on the low side). Temp on the metal tab of the IRF510 is 45degC - which is ~25 above ambient. I'm more worried about the temp on the shunt heatsink which is sitting at 53degC now - and this will probably rise a bit more when the lid is on the box.
Its a joyous amp to listen too - really sucks you in a keeps you coming back, zero fatigue. Very powerful bass which just is grippy as hell - listening to some steely dan last night and the drums were just so tight, the ring from them was fantastic. Lovely treatment of vocals too - I'm listening to Terri Hendrix singing "The Dark" from the tribute to Guy Clark album and her vocals are lovely - warm, but detailed and no over-emphasis of sibilance. I'm really impressed with it!
Overall, I'd say the Sapphire is the cleaner more neutral amp and indeed it sounds great too, but I am developing a bit of a sweetness for the J-Mo!! I suppose the other thing is that the Sapphire is more of a universal amp in that it will take all impedances. However, you could do like I jsut have (inspired by the pic RJM posted in the Sapphire thread) and build both into the one chassis - that way you can use either!!
I'm listening to CDs, on a shigaclone, fed into a EUVL 9022 dac powered by LiFePO4 batteries and a JG filter/buffer powered by salas shunts and then to the J-Mo and then K701s.
Thanks Richard for the kits and advice along the way. Its a lovely amp!!
Fran
Hi Fran,
I had hoped those kits would have kept you occupied in the workshop for a little longer, its not even December yet!
You promised pics. I wanna see pics.
Anyway, I'm glad to hear you got both projects up and running without any problems. Certainly the 2-in-1 approach is a novel one, and makes listening evaluations that much easier. Given the complementary nature of the two circuits its actually a nice option: to select the amp based on mood, headphone choice, and even the individual song.
"kmultiplier" is probably a capacitance multiplier, basically a simple voltage regulator but with with a voltage divider rather than a fixed reference. The X-reg falls into this class, but the "classic" version is just a filtered voltage divider with the output tied to a transistor gate/base: link
I had hoped those kits would have kept you occupied in the workshop for a little longer, its not even December yet!
You promised pics. I wanna see pics.
Anyway, I'm glad to hear you got both projects up and running without any problems. Certainly the 2-in-1 approach is a novel one, and makes listening evaluations that much easier. Given the complementary nature of the two circuits its actually a nice option: to select the amp based on mood, headphone choice, and even the individual song.
"kmultiplier" is probably a capacitance multiplier, basically a simple voltage regulator but with with a voltage divider rather than a fixed reference. The X-reg falls into this class, but the "classic" version is just a filtered voltage divider with the output tied to a transistor gate/base: link
It is a special cap multiplier that has very low output Zo due to the use of a CFP.
I placed it between the smoothing caps and the shunts... it took the J-Mo to a very high subjective level.
http://www.diyaudio.com/forums/power-supplies/177516-keantokens-cfp-cap-multiplier.html
The K Multiplier
OK, I'll investigate!
A pic.... as I said, it aint pretty. Thats the shunt at the back, the J-Mo in front of that and then the 2 boards for the Sapphire to the right. Single pair of input RCA jacks at the back with a switch to swap the signal from one amp to the other. 2 x headphone jacks and 2 x gigawork pots complete the wiring.
Both amps are silent as the grave, with just a touch of hiss on the Sapphire at full volume (which you would never go near anyway). At all normal to very loud listening levels, no hum, hiss, etc. etc. If it wasn't for the LEDs in the shunt and the bit of vibration from the EI Tx you wouldn't know it was on.
The lid has yet to go on, and of course the front plate which I have yet to make (this is a recycled box from a cassette deck).
Fran
A pic.... as I said, it aint pretty. Thats the shunt at the back, the J-Mo in front of that and then the 2 boards for the Sapphire to the right. Single pair of input RCA jacks at the back with a switch to swap the signal from one amp to the other. 2 x headphone jacks and 2 x gigawork pots complete the wiring.
Both amps are silent as the grave, with just a touch of hiss on the Sapphire at full volume (which you would never go near anyway). At all normal to very loud listening levels, no hum, hiss, etc. etc. If it wasn't for the LEDs in the shunt and the bit of vibration from the EI Tx you wouldn't know it was on.
The lid has yet to go on, and of course the front plate which I have yet to make (this is a recycled box from a cassette deck).
Fran
Attachments
The two matching transformers (leftmost ones) supply the sapphire, one for each board. The rectifiers are mounted right on the transformer terminals. The other one then supplies both channels of the J-Mo via a salas shunt - the PCB mounted vertically on the heatsink at the back.
Nothing shared after the back of the IEC..... I'm getting lazy maybe putting it all in the one box, but it helps keep the box count down. I'm still thinking about finishing the front of it - whether I go for a wood or acrylic, not sure yet. The other thing that I might do is split the supplies for the J-Mo and go dual mono on that. I reckon I can fit it all in, especially if I stacked 2 toroids.
Fran
Nothing shared after the back of the IEC..... I'm getting lazy maybe putting it all in the one box, but it helps keep the box count down. I'm still thinking about finishing the front of it - whether I go for a wood or acrylic, not sure yet. The other thing that I might do is split the supplies for the J-Mo and go dual mono on that. I reckon I can fit it all in, especially if I stacked 2 toroids.
Fran
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