My mix-up was that from memory the trim resistor was on the other leg of the current mirror.
In actual fact, the trim resistor reduces (rather than increases as I originally thought) the bias.
Should have checked schematics before answering.
And build the protection circuit before you put your expensive headphone on.
I know it is tempting to listen to a new toy.
So you should perhaps first build SHPP then second channel.
Patrick
In actual fact, the trim resistor reduces (rather than increases as I originally thought) the bias.
Should have checked schematics before answering.
And build the protection circuit before you put your expensive headphone on.
I know it is tempting to listen to a new toy.
So you should perhaps first build SHPP then second channel.
Patrick
One more tiny thing.
The power supply Gnd should go to the (Power) Gnd pin right between the two electrolytic caps.
This should also serve as the Gnd pin for the output.
The other Gnd pin to the front is only meant for the input signal, i.e. Signal Gnd.
If you want to be perfect then even skip the Signal Gnd and solder everything onto the Power Gnd pin mentioned above.
Then it is truely star Gnd.
Patrick
The power supply Gnd should go to the (Power) Gnd pin right between the two electrolytic caps.
This should also serve as the Gnd pin for the output.
The other Gnd pin to the front is only meant for the input signal, i.e. Signal Gnd.
If you want to be perfect then even skip the Signal Gnd and solder everything onto the Power Gnd pin mentioned above.
Then it is truely star Gnd.
Patrick
Now I have both channels tested and adjusted. Just a lot of drilling and chassis work to be done before completion. I attached a couple of ”spaghetti incident” type of pictures to present my layout plan. So there will be Oleg’s R-2R stepped attenuator for volume control and also the Xen SHPP board is shown.
Attachments
I have been asked whether the Super Linear Circuit can be used as a Power Amp.
Of course it can.
You probably want to replace the following components :
Q13 2SD2560
Q14 2SB1647
R17,18 1.5k
R19,20 0.1R 2W
You can also raise rails to +/-20V without issues, assuming you are using CCS bias and no servo.
And you could set bias at say 1.3A.
(Use 10k trimpot for the Vbe multiplier)
I have not simulated or built.
There is no Spice model I can find for the Sanken Darlingtons.
And no idea about thermal stability of bias.
Patrick
Of course it can.
You probably want to replace the following components :
Q13 2SD2560
Q14 2SB1647
R17,18 1.5k
R19,20 0.1R 2W
You can also raise rails to +/-20V without issues, assuming you are using CCS bias and no servo.
And you could set bias at say 1.3A.
(Use 10k trimpot for the Vbe multiplier)
I have not simulated or built.
There is no Spice model I can find for the Sanken Darlingtons.
And no idea about thermal stability of bias.
Patrick
And since we are on the subject, can we convert the output Darlington follower to a triple Darlington for Power Amp use ?
Yes, we can.
Attached only simulated.
I cannot find Spice models for 2SC4886 /2SA1860.
So I used the Cordell models for MJL4281 / 4302 instead.
But they should not be too different.
So if you already have a working headamp, you can change R19/20 to 68R.
Then add the power stage by P2P hard-wire.
And then you are in business.
The thermal stability of bias needs to be tested in prototype of course.
But they should be OK when mounted on a common heat sink adequately sized.
The basic circuit is really very versatile.
Patrick
.
Yes, we can.
Attached only simulated.
I cannot find Spice models for 2SC4886 /2SA1860.
So I used the Cordell models for MJL4281 / 4302 instead.
But they should not be too different.
So if you already have a working headamp, you can change R19/20 to 68R.
Then add the power stage by P2P hard-wire.
And then you are in business.
The thermal stability of bias needs to be tested in prototype of course.
But they should be OK when mounted on a common heat sink adequately sized.
The basic circuit is really very versatile.
Patrick
.
Yay, It’s rocking! Even though the top cover is not yet produced and the front panel is also only temporary... But hey it sure sounds nice, better listening impressions later. I attached a couple of pics. I have noticed along my projects that I just can’t make the wirings tidy. Propably just too lazy. The main thing is that it’s completely hum free and only faint hiss can be heard with iPhone plugs, but not with my other headphones.
Thanks Patrick for providing yet again a superb HPA project!
The main thing is that it’s completely hum free and only faint hiss can be heard with iPhone plugs, but not with my other headphones.Thanks Patrick for providing yet again a superb HPA project!
Attachments
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Here’s some listening impressions.
UTHAiM vs. Pioneer Super Linear (no X-feed)
- Very close to each other
- UTHAiM a tiny bit better in bass control (The Mars Volta - Wax Simulacra)
- PSL has deeper bass and control is also good (Massive attack - Teardrop, Children Of Bodom - Blooddrunk)
- PSL has better sense of presence with vocals (Norah Jones - Don’t know why). Feels like the singer is in the room with you.
- Sounsdtage is better/sharper with PSL
- Treble is equally good on both
- PSL is somehow smoother and very pleasant to listen to
- PSL a bit warmer sound
It really is hard for me to tell these two apart, but with a small margin the PSL is little better. Might be that my front end and my hearing capabilities are starting to limit the achievable benefits with these ultimate headphone amps. Maybe my next project is a new DAC...
I did the comparison mainly with my LCD-2F cans but the differences seemed to be very similar with Senn HD-800.
UTHAiM vs. Pioneer Super Linear (no X-feed)
- Very close to each other
- UTHAiM a tiny bit better in bass control (The Mars Volta - Wax Simulacra)
- PSL has deeper bass and control is also good (Massive attack - Teardrop, Children Of Bodom - Blooddrunk)
- PSL has better sense of presence with vocals (Norah Jones - Don’t know why). Feels like the singer is in the room with you.
- Sounsdtage is better/sharper with PSL
- Treble is equally good on both
- PSL is somehow smoother and very pleasant to listen to
- PSL a bit warmer sound
It really is hard for me to tell these two apart, but with a small margin the PSL is little better. Might be that my front end and my hearing capabilities are starting to limit the achievable benefits with these ultimate headphone amps. Maybe my next project is a new DAC...
I did the comparison mainly with my LCD-2F cans but the differences seemed to be very similar with Senn HD-800.
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So if you are only allowed to keep one, which one would you keep ?
- UTHAiM a tiny bit better in bass control
- PSL is somehow smoother and very pleasant to listen to
We agree with the two above.
Difference is really tiny.
But the PSL is, for me, slightly complexer in terms of circuitry.
They still cannot beat the DAO SE (for me at least).
The DAO SE is just that touch "sweeter" with female vocal.
Patrick
- UTHAiM a tiny bit better in bass control
- PSL is somehow smoother and very pleasant to listen to
We agree with the two above.
Difference is really tiny.
But the PSL is, for me, slightly complexer in terms of circuitry.
They still cannot beat the DAO SE (for me at least).
The DAO SE is just that touch "sweeter" with female vocal.
Patrick