The Pioneer Super Linear Circuit

> Do I have to remove any Gnd connection to chassis?

I can only tell you what I do myself.
You should then decide for yourself whether that is what you want.
Especially with amps from other people.

I float all inputs and outputs from chassis.
RCAs have insulating washers.
The Gnd of the right channel is connected to mains Earth and also heatsink enclosure via a 10R 2W Gnd lifting resistor.
(Main Earth is of course directly connected to enclosure for electrical safety.)

The left channel Gnd is only connected to the right channel via the common Gnd connection at the XFD.
The aux. supply of the SHPP is taken from the right channel PSU before the regulators.
So the SHPP Gnd is automatically connected to both channels (indirectly).
All these connections are automatically done on our own headphone amplifier mother board.

> What's about an adapter when using SE wired headphones.
> Normally the adapters are putting the Gnd wires of both channels together.

Yes, that would be the case, and it is a compromise.
But I myself have no need for such adaptors.
When testing phones from someone else, I just plug the TRS plug into the above mentioned TRSS socket.
But not for any serious listening.


Patrick
 
Afternoon matching BJT's yielded enough N&P's to get started on one pair of boards.My hfe distribution for both types was mainly in the 420 - 429 bracket and specifically within 422 - 427.

Looks like Q1-2, 7-8 will be exactly 422 and Q3-4,5-6,9-10 will be 424 - 427.

If I can help anyone with some values that they need should they not find enough complimentary matches, let me know I have many left.

Quite a few N&P's in the 430 - 439 bracket and many in the 440 - 470 spare.
 

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Interesting Patrick, it looks a similar distribution to your last graph a while back, your cross over values between the two seem the same as mine maybe slightly higher. Where did you get your parts? Mine were Mouser.

Possibly a difficult question to answer until some measurements are made but...

If the boards are built as expected with well matched parts - have you found a general resistor value for the CSS R45 to trim? It would be nice to have some 0805's ready to try.

I see one post, I think Morde, mentioned 135R so around 120 - 150R should be OK?
 
Thanks Patrick, thought so. It will be September before Mouser can send some JFETs anyway.

My test device is the PEAK DCA55 and their PCA23 adapter. Very easy to use and double tests on BJT's seem to hold consistent measurements. But I agree, in your local environment and kit they would be slightly different. In fact, it looks like my sweet spot is slightly lower than yours here in the UK Midlands.

So all my BJT's are in. Both sets of Pioneer kits and two JLH1985 sets were fully equipped with appropriate matched parts. I have to say it is very enjoyable to work with SMD. Although quite exhausting, the focus and calm required is quite therapeutic.

My intention hopefully, is to try one set with JFET input, CSS without servo first and then one set different with resistor bias and servo depending on how my supplies behave. It would be interesting to try the new Salas ultraBIB regs on the Pioneer boards but they do take a while to settle.

Lovely little design Patrick, looking at hem it is hard to believe they are the business end of a good amp.

Edit- looking at the pic I missed a Q1 on one JLH board.... Dammit
 

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> the focus and calm required is quite therapeutic.

Exactly. Though refuses to do SMD don't know what they are missing.

> to try one set with JFET input, CSS without servo first and then one set different with resistor bias and servo depending on how my supplies behave.

My own is JFET in (for good reasons), CCS bias, and no servo. No needfor servo.

> It would be interesting to try the new Salas ultraBIB regs on the Pioneer boards

Don't blame me if they oscillate.
Salas regs don't like high bandwidth amps. Ask Stixx.


Patrick
 
Yes. Been there done that.

I have entirely come away from the belief that everything audio has to be powered
by shunt regs. I have built enough amps to say that (not being arrogant).
I love the nested cap multiplier psu that is used in the DAO. Inherently stable and
not the slightest impact on sonics.
Have a second one waiting for my UTHAiM build (and a third one for a balanced pre) ;)
 
A good amplifier design should have good PSRR (Power Supply Rejection Ratio), by design.
And for many amplifier designs, the output impedance of the power supply has little significance.
So there is little argument for those regulators that relies on a lot of NFB to achieve their performance.
Most of them, in doing so, have limited bandwidth, beyond which they become inductive.

A cap multiplier does not give you a low Zout.
But when done right, it can be very low noise and very wide band.


Patrick
 
This is an example to degenerate a 2SK209 with 3mA Idss to 1mA Id.

The JFET's curve is approximately that shown by the blue dotted line.
Draw a (red) line from the originalto the intersection (green circle) of the dotted line with the 1mA horizontal line.
The slope of the red line gives you the resistor value.
In this case approximately 170R.


Patrick

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