Building a symmetrical psu B1 buffer

[parodielin]

Originally Posted by Marra

I agree with you regarding the DCB1 against the B1; the Salas unit is absolutely brilliant. I'm interested to hear what you think of the Optivol and DCB1 together having built both but not yet got around to trying them together myself.

Not sure if my subjective listening experience will help you but if I care that much to vent, it must be really good.

LightSpeed + DCB1 is working and it is dead silence on my system. As I mentioned before, B1 won't survive without a metal enclosure in the same environment. LightSpeed + DCB1 are in an open cardboard box.

With B1+CDA254, it is good. It sounds way better than my old HK 635. But during extended listening, there is a slightly "bright" tone on some content, which generates a tiny bit litsening fatigue. My speakers are ruler flat using Scan Revelators. In comparison, the B1+Emotiva XPA-2 doesn't have that "brightness", the sound stage is more extended, more dynamics, and the etc. In some content, B1+CDA254 could be a bit "dull" or not engaging.

For the "dullness", this is compared to my friend's $$$$$$$ Ayre system using the same speakers. There is an argument saying the difference I'm hearing between B1+CDA254 and B1+Emotiva is because impedance mismatch. I know too little on this area to comment (B1 - 1K, CDA254 7K, Emotiva 35K). Anyone want to chime in?

With DCB1+CDA254 - more dynamics. It removes the "dullness" feeling. I did not do an extensive listening on this because I put on the LightSpeed two days after. With LightSpeed, the immediate difference is in the mid-high frequency, say 1K-3K, where most harmonics and timbre reside. It is beautiful. Just like designing speakers, I usually listen to one channel on axis first, take measurements and move on to stereo. I haven't done the stereo on my Scans yet. By experience, what I'm currently hearing will lead to a big and massive sound stage when putting in stereo.

My Emotiva has came back. It's so heavy so I won't be hooking it up until I'm happy with all other placement (moving XPA-2 is a real pain). But the current combo is very good (LightSpeed + DCB1 + CDA254). I no longer feel I missed something from my friend's Ayre system. Actually, I was happy with B1+CDA254 and I spent majority of my time working on speakers. The upgrade was triggered after I hook my speakers to my friend's Ayre system - I didn't know the speakers can sound that good. But from ROI perspective, it is not that good to demand that much money (> $10K) from me.

Hope this helps. Now I want to build another Hot Rod DCB1.

[TheAnaesthetist]

Salas, the DCB1 is playing now for a few days and I must say it sounds super. Sounstage is suddenly much bigger, wider and deeper, there is more body, piano is clear and has weight, bass is thight and has punch. Voices are accurate without sharpness. It puts a big smile on my face with now and then disbelieve of things I really didn't hear before. The F5 is today ready too and already makes a good couple, needs a bit more burn in. Thank you and Tea Bag, dvb-projekt, spencer and others.

[Salas]

Happy listening guys, nice that you like it. Good clean inside arrangement looks by the way.

[jambul]

Hi everyone,

I build one of the hypnotize dc coupled B1. and made some mistake with the transformer and lead to the burn the right side of the diode, and i found that i missplace the second irfp240 and irfp9240.

i change the diode and test

result is :

one side of led is working (the side on the irfp9240)..all led is lit but very low intensity and on the side of irfp240 the 5 led doesn't lit.

if i pull out the irfp240 the 5 led on the side of irfp9240 lit normally.

i didn't measure the voltage and current arround componen,

is there anybody can help me with this problem

many thanks before

regards

denis

[jambul]

additional information foe the above problem,

I did change the pair of irfp240 with the new one, but the result is the same.

thank you

[Salas]

Check for voltages across all semiconductors. See if there is a zero reading somewhere.

[mike_mcf]

Hot Rodding a DCB1 increases the current going to the board. The stock current is around 60mA(?) w/ 34ohms (those parallel 68Rs on each side). But the more current you feed the mosfets, the better the sound quality as a general rule. Salas indicates this occurs in tiers, ~200mA being the next tier, 600mA after that, and then around 2A(!). But there's a catch: Heat. The more current, the hotter those mosfets get. Stock values you can forego heatsinks, but beyond that you'll need them. I'm pushing 600mA on my DCB1, using the entire 12x12 enclosure of my integrated amp as a heatsink with the mosfets bolted to the chassis AND a fan installed.

Is it worth increasing the current. Yes. Definitely the 200mA tier at least. Soundstage, three-dimensionality increases.

How do you increase the current? Resistors. The resistors by the PS caps. The BOM lists parallel 68R (=34ohms) as basic value (though the board shows 47R, which is fine as well), and 10ohm 5W for hot-rodding. You do not use 2 10R per side, just 1. This a guideline, you can increase or decrease values as you deem fit.

Could someone please tell me what value resistors to use for:

200ma
600ma
2A

[mike_mcf]

I have some more questions as I put together my BOM:

I am thinking that running 2A may not be worth the energy cost or reduced parts life. If I stay at 600mA, will the 50VA Antek transformer do (http://www.antekinc.com/pdf/AS-0515.pdf) or for the small incremental cost should I just get the 100VA version (http://www.antekinc.com/pdf/AS-1215.pdf)?

These are the best heatsinks I can find on Mouser: WA-T247-101E Ohmite Heatsinks
How much current do you think I can run with these?

I am also ordering some JFETS from Spencer. He matches them to .2mA, which I assume is as good as it gets, but I can also select the Idss. What is optimal?

[SirByrd]

Here is my progress so far:

[Tea-Bag]

Wow!