Mezmerize DCB1 Building Thread

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42001

Disabled Account
Joined 2012
Little update about the sound of the DCB1 modyfied to a slightly hotrodded version

The soundstage has "matured" I think. Voices are clear with no harsh Sses(if you know what I mean) Placement is just unbelievable! Every 2 days I played the SACD from The Dave Brubeck Quartet-Take 5. After two weeks the hairs on my arms just rise.... perfect! I think the combo DCB1 and Hiraga work really well together. I tried the DCB1 on 200Watt class A Vincent monoblocks, but they are not in the same league compared to the Hiraga. Hiraga is much faster, clearer and just more musical. What's nice is that all my friends who listen to the DCB1 are just stupified. Even the Vincent's sound much better when driven by it.

So, overall I'm extatic about the result!

Preamp will stay forever! Hiraga will be changed in time :) Goldmund Mimesis 9.2 clones are next!

People who are not sure about the DCB1 version: Just do it! Compare it with the original B1 version. You will be Mezmerized, I promiss you that!!!!

Sjoerd
 
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Offie

Member
Joined 2014
Really great to hear that Sjoerd. (greeting from Belgium). I also ordered the print for it.
Now i'm looking for some matched Jfet's. Maybe I'm gonna order a lot of them and do the matching myself.

I'm gonna drive the velleman monoblocks with it. (with IRFP9140's and IRFP140's)
http://users.telenet.be/offie/k4020.html

It's great to hear that you like this B1 buffer. Gives me good energy for starting to build it. It's my next project....PCB is on the way.

I received a friendly email from DIY audio store. Beautifull how this forum and store acts!!!!
 
4

42001

Disabled Account
Joined 2012
Hi Offie,

Good to hear you will build the DCB1. You will not be dissapointed!


Try to match the Fets as close as possible! Best within the 0.01 range with Ldss of around 10 will be perfect! That tip came from the master, Salas :)


Knowing Velleman, they will probably have input and output caps. See if you can get rid of those! That will improve the sound significantly. Also change the resistors in the soundpath for premium ones. You will be surprised what that will do with clarity. Ps: I used those Amps in my Drive-in days :) they can really take a beating!!! I have some more tips if you are interested. Just send me a PM because it would be off topic here.


Happy building!!!
Sjoerd
 
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dodog

dodog

Member
Joined 2013
Salas said:
To cut a long story short, normal way in Mez subjectively helps low current builds by introducing some rail asymmetry. Relaxing matching goals also. Total symmetry like standard in the hot-rod Hypno takes the trick. Around 200mA both ways sound the same. But it won't interfere with your LEDS symmetry you worked for anymore. Just do the thing with the middle leg soldered to its side leg in the photo. On that specific FET only.
Click to expand...

Just to be clear, I short the source and gait pins for that JFET only. I have grouped LEDs to try to match the voltage goals and also have a matched quad of JFETs. With the unmatched 6 JFETs for this particular one only, I do the leg-trick. I definitely don't understand why I'm doing this but I can follow instructions. Is this correct:

An externally hosted image should be here but it was not working when we last tested it.
 
O

Offie

Member
Joined 2014
Hi,
Someone can sell me a matched quad @ 7,42mA. Is this always OK?...I don't know the method he measured or matched it. If ok..please give me a sign ;) Or is it better to buy 50 2SK170's and do the matching myself? Is the amount of 50 enough to do a precise mathing ?
 
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A

AndrewT

R.I.P.
Joined 2004
Cedricb,
there is no "ideal" vol pot value.

Too high can result in loss of treble and non linear attenuation with pot setting
Too low can result in drawing too much current from the Source.

The "in between" range can be enormous.

For a guide of maximum range of vol pot values:
with an Rin of 220k you could use ~1/5th, i.e. 50k
A source with Rs<200ohms would allow 1k, provided the Source can drive 1k//cable capacitance.

A sensible, less wide, range would be 2k to 20k.
Personally I would go for 10k, since I know my (non-buffered output) Sources can all drive 10k//cable capacitance.
 
C

cedricb

Member
Joined 2008
AndrewT said:
Cedricb,
there is no "ideal" vol pot value.

Too high can result in loss of treble and non linear attenuation with pot setting
Too low can result in drawing too much current from the Source.

The "in between" range can be enormous.

For a guide of maximum range of vol pot values:
with an Rin of 220k you could use ~1/5th, i.e. 50k
A source with Rs<200ohms would allow 1k, provided the Source can drive 1k//cable capacitance.

A sensible, less wide, range would be 2k to 20k.
Personally I would go for 10k, since I know my (non-buffered output) Sources can all drive 10k//cable capacitance.
Click to expand...

I've got a tube power amp (Dynaco ST35 clone), so if I decide to not use the DCB1; is 10K enough? My main source is the Subbu V3 DAC.
 
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Offie

Member
Joined 2014
I would like to share this link guys. Coupling capacitors are gone in the DCB!. What is the effect of coupling capacitors....
This is really basic done, but gives a good impression. I think thant we can be happy that we don't use extra coupling capacitors...so it can't influence the music.

Next step is t take a look at the coupling capacitors of the connected equipement.

PLS TAKE IN NOTE THAT: frequently you need a coupling capacitor. Your speakers are not happy witch DC!!!!
effects from coupling capacitors in audio circuits - YouTube
 
O

Offie

Member
Joined 2014
Tea-Bag said:
Sure, I have, Woodturner-Fran has. Of course these were all done with the older boards.

use 2-3 2W 20-30R panasonic resistors (narrow leads)

Put IRF's bolted to bigger heatsinks or chassis floor.

Second 100uf cap becomes small MKP type cap of .2 or .1uf, make sure it fits.
Click to expand...

Does this mean that for hot rodding @200mA C1, C2, C3 & C4 (all in the power supply section) need to be replaced with .1µF polyester film caps?
 
Tea-Bag

Tea-Bag

Member
Joined 2006
Paid Member
WalterW said:
So that's C1 and C3 in the DIYaudio store schematic? I hot-rodded to 200mA but let the 100uF's in place. Seems to work OK.
What's the advantage by replacing them with 0.1uF MKP's?
Click to expand...

Walter, it looks like C2 and C4 to me, but spacially looking at board - as I am familiar with them as such - its the caps next to the bank of 5 LEDs.

The reported sonic performance has been proven on other threads regarding adding of more current and using a smaller bypass cap here.

I am not sure if there is a more technical explanation for you.

Tea
 
dodog

dodog

Member
Joined 2013
Just when I think I have all parts ordered, I see this. So, to hotrod to 200 mA, one needs to put 10R, 2W resistors where the 2x68R spaces are on the board. One also needs to change the two 100 uF caps (next to the bank of 5 LEDs (also next to the 100R resistors)) for 0.1 uF MKP caps?

Looks like the lead spacing for those caps is 5mm. Would these be suitable?

MKP2D031001F00JSSD WIMA | Mouser

Those are rated 63V AC, they also have 160V AC rated as well:

http://www.mouser.com/ProductDetail...=sGAEpiMZZMv1cc3ydrPrFwSei4c7mYTFSAyUvQSE8Q0=
 
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