[FunkyBassMan]

And funkybassMan its indeed about improving what is already great. But instead of judging of the first line i learned to ask questions to the people that indeed try and invest in engineering and improving gear for the fun of it and indeed experience inprovement. Dont dismiss without research

I find it a testament to the quality of the basic Dave that people bend over backwards to get it to its ultimate state.

Since running M-Dave, I understand the desire to do that: the sound of the music is so addicting in a very visceral "deep brain" kind of way (at least to me) that it feels like there's almost a kind of drug-like thing going on. It's very tempting to pursue that drug to its strongest state.

I find the basic system so addicting that it's almost too much sometimes, and it makes me afraid of going down the upgrade rabbit hole, even though I could afford to. I have other stuff to do in life.

That said, all hail the explorers who push the frontiers. I can only imagine the great stuff you're hearing.

 

[MvRBE10]

The caps replacing in the dave do not cost more than a pizza pepperoni and some time. And make a huge difference and mostly fixes the bass and drive problem of the dave for headphones. Reactcore can explain that he uses hp most i am a speaker head so my preferences are a bit different but are close to his. He has done some great work inside the dave to improve it at no cost.

That said i was in new orleans last september and had a 24” inch (60cm) pizza pepperoni and that was not cheap

 

[Reactcore]

The caps replacing in the dave do not cost more than a pizza pepperoni and some time.

I understand most users are affraid to open their Dave let alone solder in it invalidating its warranty.. if i just bought it new i would wait too.

But mine is at least 5 years old and after reading loads of posts on the Chord forums about the improvements of RF treatment and PSU change it brought me to try things even though i was a 'unbeliever' at first.

I heard exactly what i read in many places.. not only on headfi but also reviews about eg. a TT2 has superior hp drive and fuller sound.. but transparency staying behind a bit vs Dave..

So what was fundamentaly different and 'upgraded' on TT2's design?.. Capacitors!
So i knew i had to explore that.. and lucky i did since this gave not small benefits but a mindboggling change.

Yes my first attempt to place the buffer caps in parallel on the final regulator output and even straight on the amp transistors failed and gave distortion and crippled some area of the frequency response. But i didnt wanted to stop there and started to reason what is happening.. i figured it was the fact that there are 2 caps in parallel for each voltage on the amp circuit and thats mainly causing Dave to sound 'thin' as some say and needing an external amp to 'thicken' its sound. But then all music is artificial thick or coloured.

Now it can sound both very warm and cold at once with the same playing music. It totally makes an extra amp only degrading SQ imho.

Further this made the Mscaler's effect all the more appearent.. its so enormously holographic real and intimide when the track demands it. It simply pulls me into musical bliss.

Ofc its magnitude remains recording and adc process dependent.

 

[PierreHPfan]

So IYO how difficult was it to dissemble the DAVE, get out the PCB and take off the old caps, then solder the new ones in place? I am tempted, but also nervous. Don't want to bust if, even though I trust the sound reports post modding it. New caps are cheap, even best quality ones, so it is the risk factor that is stopping me.

 

[MvRBE10]

If you take your time and slowely disassemble i would say no risk at all it is basic unscrewing and slicing some tape and silicone away. With the assembleybyou have to use some double tape to attach the display to the coolant block.

The soldering of the caps if using a good soldering iron like a metcal will do the job. Ok but i do advice you have some experience with electronics and soldering. So when doubting let a friend do it who is in the electronics for some years and it is basic stuff.

 

[Reactcore]

So IYO how difficult was it to dissemble the DAVE, get out the PCB and take off the old caps, then solder the new ones in place? I am tempted, but also nervous. Don't want to bust if, even though I trust the sound reports post modding it. New caps are cheap, even best quality ones, so it is the risk factor that is stopping me.

Read this post of how to take the pcb out:
https://www.head-fi.org/threads/my-choral-housed-chord-mscaler.964931/post-17173702

Then in my signature link its shown how and where to place the caps. Its three different cap mods explained.

The first is placing the orange TDK brand caps on the INPUT of the linear regulators (LM307 & LM317) All type numbers are in the post.

The second mod is simply exchange the original 3 ones near the psu plug on the pcb For higher grade ones.

And lastly replace the original 2x two parallel caps on the OUTPUT of the regulators for 2x one of low ESR type.

Its very important to carefully observe the cap's polarities in the pictures!

If you have doubts i would advice to let someone with soldering skills do it, showing the howto.

 

[Jawed]

I heard exactly what i read in many places.. not only on headfi but also reviews about eg. a TT2 has superior hp drive and fuller sound.. but transparency staying behind a bit vs Dave..

So what was fundamentaly different and 'upgraded' on TT2's design?.. Capacitors!

Are you referring to the supercapacitors inside TT2?

 

[AnalogEuphoria]

@Rob Watts Canjam Seminar is now available on YT:

Very much enjoyed this, has the other one been recorded as well from the day after?

 

[Reactcore]

Are you referring to the supercapacitors inside TT2?

Yeap, its whats different vs other Chord Dacs and imo the reason why TT2 has better drive and control over headphones.

 

[Jawed]

Yeap, its whats different vs other Chord Dacs and imo the reason why TT2 has better drive and control over headphones.

How similar is the circuit diagram for TT2 compared with DAVE? The capacitors before/after the 12V regulators (right next to them) seem to be the most important in the work you've done. Presumably the supercapacitors are at 15V, before the final regulator. Is that right?

In the audio interview from Singapore Rob says that the output impedance of the supercapacitors is high, e.g. 50milliohm. That would seem to suggest that ESR isn't the dominant factor in the capacitance before the voltage regulators...

 

[Reactcore]

Heres another attempt to try to explain why i think i get better drive on my headphones using low ESR caps.

Imagine an amplifier with a load connected (speaker/headphones) supplied with an audio signal.
This amplifier will, aside a pre bias, draw current from its power supply. but this current is not fixed when playing music.. it varies with the signal it amplifies.
The more force is needed for a conus from a speaker driver to be pushed or pulled, the more current the amp draws. of course for headphones this is only in mA range.
In fact the amp's current drawing behaviour can be observed as audiosignal related current modulation on its power feed.

If it would be a fixed current, the PSU would just supply it, but the voltage on the amp would be slightly lower cause the dropped voltage will exist over the circuit's wiring and tracks. As long the PSU has enough rated current specified this voltage drop would not matter much.

But with a varying current, as a result, also the voltage will vary, and this is applied to the amp which in turn wil vary its amplified output together with it.

So while the audiosignal demands more force on the speaker driver coil, the voltage on the amp is slightly lowered, counteracting the output causing a form of distortion.
Distortion which is not so much obvious with a clean sinewave test signal and would not appear that much on measuring.

Now PSU's are equipped with capacitors parallel on the output for ripple rejection, not to be mistaken with RF filtering caps.
These capacitors serve another important purpose in acting as a voltage buffer. When a rising current (peak) is drawn, the capacitor will help supply it with its contained energy keeping the voltage steady.

An audio related current ripple (in a frequency range of ~20-20Khz) is too fast even for a small capacitor container to react to (unload and load again)
But a resistor does not hold energy charge and will instantly allow a voltage drop causing the above discribed effect. Resistance is everywhere on a circuit board, like plug contacts, components, wires and PCB tracks, all sum up to total resistance before the dropped (and modulated) voltage reaches the amp.

Capacitors have a notably internal resistance in series with their energy container called ESR (Equivalent Series Resistance) which can be several hundreds of miliohms.
This might not sound as much but it allows a ripple to be built up on the voltage.

Many (audiophile) external PSU's are loaded with parallel capacitors mainly to increase the capacitance and lower the AC-DC ripple or PWM ripple in case of a SMPS.
And posess a lower ESR than a 'standard' PSU like in Dave.. this will not so much lower RF.. but give benefits in the drive capabillity of the amp section. I can imagine why i heard and users say these PSU's matter.

But as stable voltage an external PSU might give.. the voltage still suffer a modulated drop while running through connector contacts and pcb tracks.
As most amps, Dave has capacitors placed close to its amp section for mainly the same reason: stabilising the voltage feed on that circuit.

But i think this can be improved by lowering the caps ESR values to decrease the current modulated voltage and with it the amp's performance.

Principle: smaller ESR makes less modulation amplitude

Aside the amp, also Dave's LM307/317 regulators react to varying input voltage, they are based on a feedback to keep their output at the set voltage.
If the input voltage drops, they raise the output current to level the voltage, this gives a delay on the audio related ripple which in turn also influence the performance of the amp. Placing additional caps on the input of them contributed also on stabillity.

Thanks for reading.. i hope this makes any sense
Cheers

 

[Reactcore]

How similar is the circuit diagram for TT2 compared with DAVE? The capacitors before/after the 12V regulators (right next to them) seem to be the most important in the work you've done. Presumably the supercapacitors are at 15V, before the final regulator. Is that right?

In the audio interview from Singapore Rob says that the output impedance of the supercapacitors is high, e.g. 50milliohm. That would seem to suggest that ESR isn't the dominant factor in the capacitance before the voltage regulators...

Rob is mentioning the supercaps ESR are not contributing to RF filtering. But this is not what im after, see my previous post.
In fact i also played around with supercaps but aside a huge capacitance they havent that low ESR.
My chosen caps on the input pose 2 mohms which is 25x smaller than one supercap TT2 has 3 caps in series for each voltage (3x6v, 3x50mohm = 150)

 

[miketlse]

Heres another attempt to try to explain why i think i get better drive on my headphones using low ESR caps.

Imagine an amplifier with a load connected (speaker/headphones) supplied with an audio signal.
This amplifier will, aside a pre bias, draw current from its power supply. but this current is not fixed when playing music.. it varies with the signal it amplifies.
The more force is needed for a conus from a speaker driver to be pushed or pulled, the more current the amp draws. of course for headphones this is only in mA range.
In fact the amp's current drawing behaviour can be observed as audiosignal related current modulation on its power feed.



If it would be a fixed current, the PSU would just supply it, but the voltage on the amp would be slightly lower cause the dropped voltage will exist over the circuit's wiring and tracks. As long the PSU has enough rated current specified this voltage drop would not matter much.

But with a varying current, as a result, also the voltage will vary, and this is applied to the amp which in turn wil vary its amplified output together with it.

So while the audiosignal demands more force on the speaker driver coil, the voltage on the amp is slightly lowered, counteracting the output causing a form of distortion.
Distortion which is not so much obvious with a clean sinewave test signal and would not appear that much on measuring.

Now PSU's are equipped with capacitors parallel on the output for ripple rejection, not to be mistaken with RF filtering caps.
These capacitors serve another important purpose in acting as a voltage buffer. When a rising current (peak) is drawn, the capacitor will help supply it with its contained energy keeping the voltage steady.

An audio related current ripple (in a frequency range of ~20-20Khz) is too fast even for a small capacitor container to react to (unload and load again)
But a resistor does not hold energy charge and will instantly allow a voltage drop causing the above discribed effect. Resistance is everywhere on a circuit board, like plug contacts, components, wires and PCB tracks, all sum up to total resistance before the dropped (and modulated) voltage reaches the amp.

Capacitors have a notably internal resistance in series with their energy container called ESR (Equivalent Series Resistance) which can be several hundreds of miliohms.
This might not sound as much but it allows a ripple to be built up on the voltage.

Many (audiophile) external PSU's are loaded with parallel capacitors mainly to increase the capacitance and lower the AC-DC ripple or PWM ripple in case of a SMPS.
And posess a lower ESR than a 'standard' PSU like in Dave.. this will not so much lower RF.. but give benefits in the drive capabillity of the amp section. I can imagine why i heard and users say these PSU's matter.

But as stable voltage an external PSU might give.. the voltage still suffer a modulated drop while running through connector contacts and pcb tracks.
As most amps, Dave has capacitors placed close to its amp section for mainly the same reason: stabilising the voltage feed on that circuit.

But i think this can be improved by lowering the caps ESR values to decrease the current modulated voltage and with it the amp's performance.

Principle: smaller ESR makes less modulation amplitude


Aside the amp, also Dave's LM307/317 regulators react to varying input voltage, they are based on a feedback to keep their output at the set voltage.
If the input voltage drops, they raise the output current to level the voltage, this gives a delay on the audio related ripple which in turn also influence the performance of the amp. Placing additional caps on the input of them contributed also on stabillity.

Thanks for reading.. i hope this makes any sense
Cheers

Thought provoking.

 

[Jawed]

Rob is mentioning the supercaps ESR are not contributing to RF filtering. But this is not what im after, see my previous post.
In fact i also played around with supercaps but aside a huge capacitance they havent that low ESR.
My chosen caps on the input pose 2 mohms which is 25x smaller than one supercap TT2 has 3 caps in series for each voltage (3x6v, 3x50mohm = 150)

Disregarding the RF subject, what I'm curious about is why the supercapacitors do something that you like with TT2, despite the fact that the ESR, which has always been the top priority for you, is "relatively poor".

I'm not trying to suggest that ESR is irrelevant. I'm curious why it appears not to be detrimental in the case of TT2.

So I'm curious, why is ESR important in the performance of DAVE, but seemingly not in TT2. That's why I was asking about the similarity of the circuit for each, as perhaps there's a crucial difference with TT2 that is more than just the supercapacitors.

Of course you might tweak TT2 with low-ESR capacitors, e.g. after the regulator, and discover a similar improvement as heard with DAVE.

 

[Reactcore]

Of course you might tweak TT2 with low-ESR capacitors, e.g. after the regulator, and discover a similar improvement as heard with DAVE.

I haven't measured inside TT2, but for sure its power section is much improved.

As far ive seen TT2 doesnt have Dave's LM307/317 regulators (which are a Bob Dobkin 1976 design) but a new discrete circuit. Its supercaps surely contribute to more stable voltage. Rob also said only after Dave and battery findings with 2Qute/Qutest he focussed more on PSU section and changed TT2's design on that. Ofc mainly looking to the RF side of things, but also to be able to deliver extra current for the amp section to drive speakers which he wanted for himself.

Anyway every circuit behaves different and Dave's one is really sensitive to stable voltage cause of its regulator design. My (and others) ears have confirmed that.