[Reactcore]

Haha. Now I am jettsetting. Would love to visit the Netherlands. If I visit in the next couple of years I will definitely hit up @Reactcore. Leave my Dave for a tune up. HAHAHA.

@Reactcore You are not going to Can Jam Dallas, TX by any chance? hehe

Im not planning on going there..

But my door is always open to fellow music lovers

 

[SteveHulk]

Good point.
In fact i tried to acquire those.. asked Digikey to get a quote from TDK.. but they denied delivery of low numbers.. i cant get my hands on them.. still i would then place 6x 2200uF as its improvent to Dave's amp drive is ever increasing

I guess if you really want to be free of size constraints you could build an outboard caps box for the Dave.

 

[Reactcore]

I guess if you really want to be free of size constraints you could build an outboard caps box for the Dave.

That wont be a good idea as it would significantly increase the ESR on the regulator.
Having the caps directly on them is what makes it a better solution.

 

[SteveHulk]

That wont be a good idea as it would significantly increase the ESR on the regulator.
Having the caps directly on them is what makes it a better solution.

If the caps box was immediately behind the Dave and connected with the shortest possible thick high-quality wires, where would all this extra resistance come from?

If you put the caps externally you could have whatever caps you like in the box. Even huge supercapacitors or motor run capacitors.

 

[Reactcore]

If the caps box was immediately behind the Dave and connected with the shortest possible thick high-quality wires, where would all this extra resistance come from?

If you put the caps externally you could have whatever caps you like in the box. Even huge supercapacitors or motor run capacitors.

Even the same cap cilinder 3 pin type has lower ESR than the same cap in 2 pin variant.. 1,3 mohm is an extremely low resistance.

Seeing the small improvement 6 caps had over 4.. i think im reaching the limit cause the LM regulator inhibits internal resistance too.

And i like the aesthetics as it is now

 

[Jawed]

With all your upgrades, do they make you more or less interested in the Ultima DAC or an eventual (guessing) DAVE 2?

 

[Reactcore]

With all your upgrades, do they make you more or less interested in the Ultima DAC or an eventual (guessing) DAVE 2?

Surely im interested to hear them.. but its hard to imagine how it could get much better.
I guess it should be my headphones being the weakest link now..

Allthough before i never believed my HD800's were capable of such convincing realism speed and power

 

[Jawed]

Surely im interested to hear them.. but its hard to imagine how it could get much better.
I guess it should be my headphones being the weakest link now..

I have similar feelings though in my case I would like a DX amp before a new scaler or DAC, since I think that my power amp is probably the weakest link.

I'll probably let the dust settle before listening. It would be nice to be blown away but I doubt it. Sort of like DAVE compared to the original Hugo.

 

[Reactcore]

I have similar feelings though in my case I would like a DX amp before a new scaler or DAC

Oh we are by now only waiting for 7 years for that with multible 'final test stage' statements will it ever come..

But maybe the new ultima DAC gets speaker terminals

 

[Jawed]

Oh we are by now only waiting for 7 years for that with multible 'final test stage' statements will it ever come..

But maybe the new ultima DAC gets speaker terminals

I replaced the Etude with the Ultima just over a year ago because DX was looking so far off...

I imagine Rob will make Ultima DAC like DAVE: the balanced output will be ultra low current - but phono sockets (and headphone jack) seem likely to be at least as powerful as TT2 as there are headphones that want that kind of power.

 

[Reactcore]

After equipping the silver Dave with the optic receivers.. i took the time to do some testing with the Sean Jacobs cap board, alone and combined with my cap mods..

First my impression with this Dave in stock form feed by its original smps in external box..

The board gave by comparison a stronger bass and meat to the sound.. surely an improvement over stock. It further kept its signature intact.. treble kept quite the same but flows better into the midrange.

But i missed the organic sound and the extra depth in the sound.. the powerful grabbing ultra sub bass and that realness im now used to with my black Dave.

So then the combination of this board with my other mods..

It worked out in the opposite way.. again in comparison to both seperate mods.. the sound became congested in its midrange and bass.. quite evident.
It seems two groups of low esr caps with PCB tracks between them give (contra)currents which interfere with the regulators and with it Dave's amp section.

Taking the Sj cap board out immediately took this congestion away.

So i started reasoning how to battle this issue.. i came up with.. yes.. 1ohm serial resitors in between the Sj cap board output and Dave's PCB input
It seems this prevents current buildup by joint (dis)charging cap groups.

The Sj cap board became a nice addon, although very marginal.. to the stock smps and caps by the regulators.

The TDK caps still pose a very low ESR to the regulators but are backed by the first group dampened by the series resistors.

I learn everytime more as i DIY on..

 

[Reactcore]

I can imagine its a bit confusing what i have been doing with all the mods sofar.
So ive been drawing my progress step by step until my last finding.

Starting with the schematic of a stock Dave:

I'm solely focussing on Dave's analog circuit's power section. The 5VDC from the PSU is for digital circuitry and pulse array.
I never made any changes on my Dave's analog audio path because thats perfectly implemented and i dont want to mess that up.

As you can see, Rob placed a LC filter to dampen RF noise from the power input. This is placed near the white Molex PCB connector. From there PCB tracks run straight under the display to the regulators located on the far right. after the regulators a dual parallel cap setup is placed to keep equal track distances to both channel's OP transistors. I coloured the positive voltage rails in Red and the negative rails in Blue. Circuit ground is in black.

Im naming my mods alphabethically to give the order in time that i placed / tried them.
So lets start with my first attempt to add the TDK ultra low ESR caps on the regulator's outputs.
Left schematic Mod A 1st attempt:

I was puzzled to why suddenly the bass mostly disappeared, Dave sounded totally wrong, i really thought Low ESR would make a good voltage buffer, well i thought the analog amp circuit must be too much influenced.. so i took the caps out.

Then i tried them on the input side of the regulators as shown in the middle figure, 2nd attempt.
Now we are talking! i was greeted with enormous ultra sub bass which initially made me think it is artificially boosted bc it stood out of other frequencies.
Later when i got a TT2 to compare it to i found the sub bass was actually on par with the TT2. Hm.. so why the mid range kept behind.. i like the fuller sounding mid part of the TT2. Dave sounded more open in trebble and with better transparency and details still.

After some time brainstorming i had a hunch.. Since on the output side more caps in parallel on the original dual caps made it worse.. what if i change those dual caps to a single setup? .. So i changed the circuit as shown on the right figure Mod B.

What the F. Omg.. this sounds much fuller.. the mids were lifted to TT2 level.. theres was alot more energy to the sound and the treble could get quite loud, not so much digitally harsch but some tracks made it less nice to listen to. Overall this was amazing and i started posting about what i heard.
Also the Mscaler's transients became more evident in the midrange.. not just some high frequency room reverb.. but full bodied texture to instruments.
After this i played with different brand and type of caps and even added 2 more TDK caps on the input side where a parallel setup didnt have such negative effect.
This gave even more control on my headphone's drivers.

So i listened for a time until another Dave entered my house.. a Silver stock one equipped with a Sean Jacobs cap board, sadly the DC4 unit didnt came along..
I switched back to totally stock and compared my black Dave to it.. Oof.. this sounds so thin by comparison .. nice in balance and clear sounding but cold and not engaging.
Where is the rumbling sub bass..?

But it gave me the opportunity to try that Sj cap board on my Dave.
So i installed it making my Dave's circuit as shown in figure under:

I started listening.. but.. this was not as i expected.. it sounded weirdly congested again.. some areas of the frequency spectrum were 'damaged'
actually a similar effect as the dual cap setup on the regulator output. Hm why is this happening.. the Sj cap board has a big capacitance and quite low ESR..
I reasoned before that an audio modulated current has a big influence on Dave's Amp's behaviour.. it can detract parts of the frequency spectrum as i noticed.
It all has to do with (de)charging hardwired caps via long(er) wires/PCB tracks and this is being amplified by the Amp's feedback design.

So i came up with the idea to significantly increase the resistance between the SJ caps and Dave's input with 1 ohm .. one might think this is a bad step.. but my tripple TDK ultra low ESR caps work as a voltage buffer(battery) so i only need to keep them charged by the PSU where the PSU cant boost big currents.
Now theres a big damping between the cap groups not being hardwired, stopping the interchanging currents between them or make them much delayed so to speak.. out of the audible frequency range.

Ohmy yess ..this sounds marvelous.. the Sj cap board doesnt break down the sound anymore and my Dave sounds full and authorative again..
wait.. i even hear improved transparency and deeper details.

But wait.. arent there more hardwired caps in Dave.. yeap.. the first LC filter caps are hard connected via a coil to my TDK caps.. so i will place another resistor in between those.. but make them 0,47ohm each to keep under 1ohm total otherwise the 15v voltage drops to much by current demand and bias of the class AB amp stage.

Damn.. Dave opened up even further.. such balance and transparency i never heard before.. all congestion totally gone.. enormous sub bass to sky reaching highs
and that realness just toxicating.. the mids fully textured.. this is hard to beat by anything, it sounds like Rob's digital masterpiece and pulse array just lost all constraints and can breathe.. it drove me to tears of emotion listening and hearing yet more into my music.. just Perfect!

Since the Sj cap board isnt mine.. i took it out leaving the resistors in place and found there was no easy hearable change to the sound..

So the final circuit now looks like this:

Mod D&F: resistors in place

Hoping not to have bored you all with my crazy modding i'm going back to Bliss

 

[TheAttorney]

So the final circuit now looks like this:

Well, what an intriguing end result!
I'm glad you found a simple way of making the SJ caps board more or less redundant. Saves on cost and complexity.

For those of us who like simple one-box solutions, will all of your caps mods fit if the smps stays inside Dave?
I'm particularly thinking of the Mod E cap change.
From your earlier posts, it would seem that taking the smps out of Dave provides marginal benefit, considering the extra complexity.

 

[Reactcore]

will all of your caps mods fit if the smps stays inside Dave?

Sure, the SMPS can stay in Dave with all cap mods.

I'm particularly thinking of the Mod E cap change.

I think all mods are complementing each other.. if you dont add the dampen resistors.. increasing the capacitance in the SMPS will make it worse cause of their negative current exchangings with Dave's LC caps.

I have to admit the original 15v caps are small.. only 330 and 100uF.. the new ones barely fitted


New Chemicon caps

 

[Jawed]

Great to hear about your latest exploits, I imagine it's a hell of a lot of fun and addictively rewarding.

I can't help wondering whether Mod A with triple capacitors is worth trying instead with just a single capacitor...