My_Ref Fremen Edition - need help on PCB evaluation

[bcmbob]

Dario, Count me in. May be a good excuse to buy some of the new "scope" hardware/software Android/iPhone offerings.

One question, do you recommend two boards/kits to be able to hear the improvements in "stage" and separation elements or can one grasp the differences that you are promoting with a single?

Will remit as required.

[ClaveFremen]

Originally Posted by bcmbob

Dario, Count me in. May be a good excuse to buy some of the new "scope" hardware/software Android/iPhone offerings.

The measurement thing is a nice plus but it's not required.

So at the moment:

1. Me
2. Soongsc
3. BmcBob
4. .
5. .
6. .

Originally Posted by bcmbob

One question, do you recommend two boards/kits to be able to hear the improvements in "stage" and separation elements or can one grasp the differences that you are promoting with a single?

One of the biggest difference will be soundstage, I think is hard to appreciate the change without two PCBs.

IMHO, the best thing is to buy the two PCBs since they will be manifactured with same specs as definitive ones:

• 2mm FR4
• 2 Oz/70u copper
• Blue solder-mask
• Serigraphy on both sides
• ROHS HASL finish

Well, maybe the definitive ones will have chemical gold finish instead of HASL if the price is reasonable...


Anyway with two boards, if everything works as intended, you'll have a complete working amp.

Originally Posted by bcmbob

Will remit as required.

It will be between the last week of December and the first of January since the PCB factory is closed for Christmas Holidays till Juanuary the 8th.

[ClaveFremen]

Originally Posted by ClaveFremen

In this moment I'm doing the last tests (LM3886 ground to GND and optional caps for AC input)

Wow, I was no expecting such a big impact.

Bass is tighter, soundstage wider and deeper and dynamic gains too, even the output DC offset fall near 0V (from 2mV to 0.5V in one channel).

The AC input caps have also a clear effect, without them bass is deeper and fuller and soundstage wider and deeper too.

The optional AC caps will remain since they permit more flexibility with different transformers and with the double bridge things could be different.

With these tests all mods included with FE are verified on TP boards apart the double diode bridge (BTW the PCB can be easily adapted to work also with a single bridge).

If the PCB works as intended this is going to be a pretty different beast...

[soongsc]

What AC caps are you referring to?
MyRef C had the Lm3886 ground to GND, you said that this board had the Lm3886 ground to signal ground. So which are you referring to as the WoW?

[ClaveFremen]

Originally Posted by soongsc

What AC caps are you referring to?
MyRef C had the Lm3886 ground to GND, you said that this board had the Lm3886 ground to signal ground. So which are you referring to as the WoW?

Well, let make thing clear...

The 'AC' cap is marked C5 on TP boards, it's the one on side of rectifiers.

The original MyRef has the LM3886 GND (Pin 7) referred to 0V (signal ground) while the Fremen Edition to GND (power ground).

The wow is obviously referred to Fremen Edition way...

I've attached also the last schematic.

[soongsc]

Those AC caps are supposed to be X caps, are there surface mount Xcaps available? I wasn't aware of any, but I wasn't looking either.

I've always wondered about the LM3886 ground, but had not tried it yet.

[ClaveFremen]

Originally Posted by soongsc

Those AC caps are supposed to be X caps, are there surface mount Xcaps available? I wasn't aware of any, but I wasn't looking either.

Those caps are not specced as X type in none of My_Ref versions, actually I don't think they need to be... they're not on mains voltage.

Originally Posted by soongsc

I've always wondered about the LM3886 ground, but had not tried it yet.

Definitely that mod has a bigger effect than what I was expecting...

[soongsc]

Yes you are right, those are on the secondaries. I would have expected larger caps for those though.

[ClaveFremen]

Originally Posted by soongsc

I would have expected larger caps for those though.

C5 was there only to damp ringing of the original diode bridge.

With the use of high speed/softrecovery discrete diodes it's no longer necessary, in fact in the My_Evo C5 is no longer present.

[AndrewT]

capacitor (C5) - only to damp ringing.

This does not sound right.