oneplustwo F5 build thread

[Bksabath]

Really? Will I be able to hear the difference? To be honest, I have no idea how good/bad 14mV is in the grand scheme of things and I feel like my speakers are already pretty good. Or at least, I'm not sure how much better my speakers will ever get!

Course you could hear difference especialy with ear glued to front o speakers

Another customer with Papa bug......

Once started there is not stopping F5 is realy realy good now that you mastered the first one more will certanly folow.

Have you tried to play with P3?

 

[oneplustwo]

Mine didn't have P3. I do still need to finish my beta 24 though. Also, my dcb1 still needs a little work... Although I hear the f5 doesn't really need it. And then, I have parts for my statements speakers that are patiently waiting for me. Too many projects, not enough time.

 

[oneplustwo]

Hmm... I can indeed hear hum at the speakers. I thought it was my source, but maybe it's the ripple? I measure 3.5mV AC at the output. How is that in the general scheme of ripple? What would be the typical improvement scheme? Introduce a choke somewhere? More capacitance?

 

[Bksabath]

Is not bad at all but now that you know that it is there....
yess you got it another RC or if you can LC is the way to go

IF you said it was 3.5 mV at the begining probably I would not have said a thing... sorry

 

[oneplustwo]

Is not bad at all but now that you know that it is there....
yess you got it another RC or if you can LC is the way to go

IF you said it was 3.5 mV at the begining probably I would not have said a thing... sorry

Ha! The 3.5 mV is at the speaker posts with my IPhone plugged in (paused). Maybe I need to try it with my DAC and see what it is.

The bigger numbers were just before and just after the PSU PCB.

That said, is there an easy way to implement LC with where I'm currently at?

 

[AndrewT]

3.5mVac at the speaker posts is terrible.

Expect <=0.1mVac

 

[6L6]

Hmm... I can indeed hear hum at the speakers. I thought it was my source, but maybe it's the ripple?

First, assume that it's improper grounding, not ripple. You have a 2 chassis design and a 'red' psu board... so there might be some weirdness.

First 2 things to check -

Does it hum with the input jacks open?
Does it hum with the jacks shorted?

 

[oneplustwo]

First, assume that it's improper grounding, not ripple. You have a 2 chassis design and a 'red' psu board... so there might be some weirdness.

First 2 things to check -

Does it hum with the input jacks open?
Does it hum with the jacks shorted?

Input jacks open I get 0.4 and 0.6 mV on the two sides. So at least better than before. Not yet <0.1 mV though. No hum.

How do I short the jacks? (when I tried shorting the ring to sleeve of my 3.5mm to RCA cable, I get bad hum.)

 

[6L6]

Take an alligator clip and attach the ring to sleeve. It's usually easiest to do this on the inside of the amp (I.E., the back of the RCA jack.)

 

[oneplustwo]

Take an alligator clip and attach the ring to sleeve. It's usually easiest to do this on the inside of the amp (I.E., the back of the RCA jack.)

Goes up by 0.2 mV with inputs shorted.

 

[6L6]

Well the good news is that it's hum, not ripple. Now you need to fix the hum...

 

[oneplustwo]

Well the good news is that it's hum, not ripple. Now you need to fix the hum...

Ok. I'll try playing with the grounding scheme. Also, I want to try my DAC and see if that makes a difference in terms of audible hum.

Any other recommendations?

 

[Andersonix]

Put it in a steel box.

 

[oneplustwo]

Put it in a steel box.

The speakers? Yah, I guess that would get rid of the hum.

DAC didn't reduce the hum. Will try options with the earth ground wire next.

 

[6L6]

The Earth ground probably isn't it, but do try a couple of configurations, you will probably make it quieter.

Look at the signal grounding, start by removing one of the ground wires from the PSU board and attaching both ground wires to the same point on the psu (I.E., both signal grounds to one side.)

There was a guy who recently had a similar problem with the red board psu, I will try to dig it up.

 

[oneplustwo]

Aha! I think I forgot to tie the signal ground to the PSU board in the first place!



Oops. I will try that tonight and see what happens.

 

[Zen Mod]

NTC please

 

[oneplustwo]

Sorry, what does NTC mean?

EDIT: NTC is the CL-60 thermistor? In which case, I think I'm good since the PSU PCB is already populated with that.

 

[6L6]

Yes, the NTC is the CL-60 ground-breaker. Not the 2 in the PSU being used as the inrush suppressors.

Attach the signal grounds to the ground-breaker, and at the same spot. Hopefully that's the problem.

 

[Bksabath]

Negative Themperature Coefficent

Also on bias thermistors 4.7K