Yes it is a good idea getting a populated board also. You will have one control board ( populated one ) and the other with variable parts. That way you know which way the mods are going. Don't keep soldering parts on the test board . Use very small extender wires to the parts being changed/compared. That way the board's tracks will not get damaged by repeated soldering. Better done on the solder side of the board.
I find some other boards like DAC's being sold by several vendors. Looks like they source it from the same person as the tracks/board look identical. This JLH board might also be similar. Board prices might vary depending on parts type and possibly shipping methods and charges.
I find some other boards like DAC's being sold by several vendors. Looks like they source it from the same person as the tracks/board look identical. This JLH board might also be similar. Board prices might vary depending on parts type and possibly shipping methods and charges.
Yeah, or just shoot for the high quality components right off the bat right ?
Board shipped, but won't be here for another week or two. I need to now find a good case that looks good, and of the right size.
Do you have any recommendations on a diy dac by any chance?
Thanks!
Hi All,
Until now I was read only mode here and now sorry for the OFF, but I would reflect to oz7affs #216.
I built the complementer symmetric amp linked this post and I have to say that this is most superior than the JLH! Fast, precize and natural sound. Not as smooth as JLH, more fast, but easy to listen. I more like this with MJE243/253 BJTs at the end, these give more natural sound; original BD139/140 have too much highs for me. The sound is very similar too CKKIII (with BJT input and MJEs), but a little bit more "negative feedback sound", more disciplined, but same clear.
Here is a photo. Its inside not beauty, this is a fast built prototype. I not used caps in the signal path.
oz7aff, thanks for share this amp! Has it name?
ON: And here is my JLH. It's not from cheap eBay parts, I bought everything in local stores in Hungary. (KITs BJTs have less beta than specified... Other parts was messy look too.). It has less than ideal bass for me, slow, relaxed sound; but more clear than IC devices. I used BC547C/557C and TIP41C.
Regards,
bkercso
Until now I was read only mode here and now sorry for the OFF, but I would reflect to oz7affs #216.
I built the complementer symmetric amp linked this post and I have to say that this is most superior than the JLH! Fast, precize and natural sound. Not as smooth as JLH, more fast, but easy to listen. I more like this with MJE243/253 BJTs at the end, these give more natural sound; original BD139/140 have too much highs for me. The sound is very similar too CKKIII (with BJT input and MJEs), but a little bit more "negative feedback sound", more disciplined, but same clear.
Here is a photo. Its inside not beauty, this is a fast built prototype.
I not used caps in the signal path.oz7aff, thanks for share this amp! Has it name?
ON: And here is my JLH. It's not from cheap eBay parts, I bought everything in local stores in Hungary. (KITs BJTs have less beta than specified...
Other parts was messy look too.). It has less than ideal bass for me, slow, relaxed sound; but more clear than IC devices. I used BC547C/557C and TIP41C.Regards,
bkercso
oz7aff, thanks for share this amp! Has it name?
I think it is very fine that you have tried to build a copy.
It looks fine and I notice that you find it good as I did also.
It has no name, the original project was made by a Danish HiFi magazine back in 1980 and they only called it a High Speed Headphoneamp.
It was build with 2N5210 and 2N5087 as small signal transistors and as power transistors they used MPSU05 and MPSU55. These transistors has become obsolete in this part of the world and that is why I tried to build it with comonlly aviable european transistors.
I can mail you a copy of the original article, but it i writen in Danish.
Please download it here:
http://www.sandcastle.dk/artikler/HSHPAMP.pdf
You should be able to translate it via Google translate.
Thanks for it!
I experienced that idle current is more independent from temperature if T5 isn't installed on the heatsink. T12, T13 emmiter resistors are large enough for good temperature stability, and T5 on the common heatsink foul up this.
I wait for compare this amp with my friends Panda amp.
I experienced that idle current is more independent from temperature if T5 isn't installed on the heatsink. T12, T13 emmiter resistors are large enough for good temperature stability, and T5 on the common heatsink foul up this.
I wait for compare this amp with my friends Panda amp.
According the original article, the main concept of this amp is the low TIM distortion because of the low open loop gain (as the first simulation shows too). Similar design concept used by Kevin Gilmore when constructed Dynahi (or Gilmore amp, I don't remember exactly).
CKKIII open loop gain is even less (as it is an open loop amp), maybe for this is the reason of the sound similarities.
CKKIII open loop gain is even less (as it is an open loop amp), maybe for this is the reason of the sound similarities.
I newer noticed any problems with the stability og the idle current. It might also have something to do with the size of the heatsink and the thermal connection between T5 and the heathsink.
Yes, they talk a lot about TIM, one have to remember that TIM was the big thing back there in the late seventies and early eighties
Yes, they talk a lot about TIM, one have to remember that TIM was the big thing back there in the late seventies and early eighties
Someone mentioned that even very low bias currents can still sound good. I did try that and it really sounds fine. The heatsink is barely warm. Didn't measure the current but it is low compared to normal class A settings. Distortion levels might have gone up it isn't apparent on listening to music. I blew the + power supply. No idea what happened. I think the mains voltage went up and it blew the diodes and cap. So can't make anymore measurements till it's fixed.
My output offset started at about 4.6 mV and dropped to 4.1 mV after 30 minutes and didn't vary much after that. I can trim it down further but haven't done so. However the board is open and not in an enclosed case.
The plan to upgrade it and box it has been delayed.
My output offset started at about 4.6 mV and dropped to 4.1 mV after 30 minutes and didn't vary much after that. I can trim it down further but haven't done so. However the board is open and not in an enclosed case.
The plan to upgrade it and box it has been delayed.
Not sure which amp the previous post is referring to. The one I built is the JLH circuit from the Net. Transistors BC557/558/547 and BD139 for the output.
I can't measure anything now as the power supply is blown. Looks like the -ve 12 V regulator blew. There was a lot of power fluctuation that morning. Could be the cause.
Anyway I simulated the circuit and with the component values I have and the output quiescent current appears to be 26 mA. Still sounds very good. Instead of two 1n4148's I used a red LED for the bias control circuit. My phones is 60 ohms I think.
The amp is very silent. No background hiss ( or hum ) at all !
I can't measure anything now as the power supply is blown. Looks like the -ve 12 V regulator blew. There was a lot of power fluctuation that morning. Could be the cause.
Anyway I simulated the circuit and with the component values I have and the output quiescent current appears to be 26 mA. Still sounds very good. Instead of two 1n4148's I used a red LED for the bias control circuit. My phones is 60 ohms I think.
The amp is very silent. No background hiss ( or hum ) at all !
Many eBay parts are fake. But amp is correct.
Fake parts can produce noise, hum or damage the amp.
For example: I measured TO-92 transistors beta from eBay JLH headamp kit: every beta was lower than specified!
Grounding/wireing also can produce hum.
Idle current mainly depends on the temperature of T5. I used smaller heatsinks than yours, so the change was higher during warm up. After that I disconnected T5 from heatsink and "problem" solved.
Absolute rubbish! What are you you talking about?
Have you built one?
My rendition is stunning, no hiss no hum only mind boggling great tunes!!