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Old 23rd January 2010, 12:44 AM   #891
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I tried a new pot in my DCB1 tonight. For those on a budget (or not actually) these are fantastic value:

DACT Type 21 Stepped Attenuator 20K FOR PASS B1 DIY - eBay (item 120502791204 end time Feb-04-10 09:17:39 PST)

So how does it sound? Well, very good actually. The sound is a bit warmer than with the lightspeed, and to be absolutely honest, in my system, thats probably a plus. The soundstage is not as distinct, or maybe resolving, as the lightspeed, but its very nice. The action on the pot is nice, the detents are very smooth/gentle not very "clicky" if you know what I mean. The other one to compare it to is the valab one, which is 25$. In terms of sonics, I don't think the valab one is any better, but I'd say the switch quality in the valab one is probably better. Having said that, there are lots and lots of open case pots out there working AOK.

No clicks, pops etc on turning. Feel wise, I think this is one of the nicest yet. At that price an absolute steal.

I'm going to leave it in for a while and see how it goes....

Fran
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Old 23rd January 2010, 12:47 AM   #892
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Oh yeah, meant to add, these are a drop-in replacement for an alps (AFAIK) so if you just solder on a few pins to the pads on the little circuit board, you can just drop it into the DCB1 board. Body size is tiny, so no problems fitting it.

What a bargain.

Fran
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Old 23rd January 2010, 02:39 AM   #893
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Quote:
Originally Posted by woodturner-fran View Post
I tried a new pot in my DCB1 tonight. For those on a budget (or not actually) these are fantastic value:

DACT Type 21 Stepped Attenuator 20K FOR PASS B1 DIY - eBay (item 120502791204 end time Feb-04-10 09:17:39 PST)

So how does it sound? Well, very good actually. The sound is a bit warmer than with the lightspeed, and to be absolutely honest, in my system, thats probably a plus. The soundstage is not as distinct, or maybe resolving, as the lightspeed, but its very nice. The action on the pot is nice, the detents are very smooth/gentle not very "clicky" if you know what I mean. The other one to compare it to is the valab one, which is 25$. In terms of sonics, I don't think the valab one is any better, but I'd say the switch quality in the valab one is probably better. Having said that, there are lots and lots of open case pots out there working AOK.

No clicks, pops etc on turning. Feel wise, I think this is one of the nicest yet. At that price an absolute steal.

I'm going to leave it in for a while and see how it goes....

Fran

Great to hear, I picked up a couple myself (and posted about it awhile back).
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Old 24th January 2010, 08:46 PM   #894
DQ is offline DQ  Romania
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My p2p built DCB1 is finished! And it's running OK! Horrrayy!

PSU voltages: +10.3 and - 9.94 VDC.
DC offset: 0.8 and 1.3 mV - with the initial LEDs, I didn't have to replace any of them!

Pictures here. Case is not too pretty, I even made some unimportant mistakes, but I was too tired and a bit disappointed after the F2 experience, so i didn't care to remedy them.
I have skipped the relays part. R1 in the PSU is 11 ohms (2x22 ohms in parallel); sinks are too big, but I wanted to be sure ; pot is external for the moment and all I had was a 50k ALPS Blue, so I replaced the 220k in the buffer with 560k. Hope to change it for the above mentioned 20k stepped soon and perhaps a Lightspeed later on, right now I'm short of money - badly!
About the sound I cannot comment much yet, I have tried it with my Mackie HR824 active monitors and it does sound fuller than solely with the pot, but I was with a guest and I didn't have time and proper conditions for a better assessment. I'm not even sure the Mackies are DC protected, btw. And I'm moving to another town in 3 days, so the audio hobby will have to take a (short) break.

Many many thanks to Mr. Pass and Salas as the authors of the "B1" and the "DC", respectively, and also to all the other members here whose knowledge and willingness to help are much appreciated!


I have a couple of questions, though:

1. I hear a hum that I'm 99% sure is a ground loop as I stupidly used some female RCA connectors that touch the ground to the chassis. Instead of buying and soldering other connectors, can I just unsolder the ground from all the connectors and connect the circuit ground to the chassis in a single point elsewhere? This way the signal input ground would be connected to the circuit (= output) ground through the chassis itself: input cable ground --> male RCA connector ground --> female RCA connector ground --> chassis --> circuit ground (and similar for the output). Would this be detrimental to the sound quality?

2. Should I decide to build an F5 instead of my F2 that I have some problems with atm, where would I have to insert a capacitor in the DCB1 + F5 combo? Can it be at the F5 input? Sorry, I'm sure this has been asked before, but I can't find where right now... Also, what value should that capacitor be, can it be 1 uF?

Thanks again!
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Old 25th January 2010, 12:01 AM   #895
Salas is offline Salas  Greece
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You are welcome.

1. Try that grounding change you thought of. It may work, if that is actually the only grounding problem.

2. F5 must be 100K load if I recall correctly, so 1uF in series with its input must be enough, and the correct place for a single coupling cap in a DCB1S+F5 system.
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Old 29th January 2010, 02:16 PM   #896
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Any issues with using the DCB1 to drive both a power amp and a sub, i.e. dual outputs?
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Old 29th January 2010, 02:25 PM   #897
AndrewT is online now AndrewT  Scotland
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only slight.
The output impedance of the B1 will see both RF attenuating capacitors and the capacitance of the two cables.
You may have to check that the R and the Total C are within your acceptable range of filtering.
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Old 29th January 2010, 02:28 PM   #898
Salas is offline Salas  Greece
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Quote:
Originally Posted by pengboon View Post
Any issues with using the DCB1 to drive both a power amp and a sub, i.e. dual outputs?
Its a buffer. Not 0 Zout but adequate. Will make do. Its output resistor normally counteracts ringing. If in a problematic situation, up in value.
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Old 29th January 2010, 02:36 PM   #899
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I have three outputs, I cannot tell of a problem. I use 100ohm resistors between them on the signal side. I dont remember where I got the recommendation to do this.
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Old 29th January 2010, 03:29 PM   #900
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Originally Posted by Tea-Bag View Post
I have three outputs, I cannot tell of a problem. I use 100ohm resistors between them on the signal side. I dont remember where I got the recommendation to do this.
OK, thanks. So all outputs connected to output of DCB1, and 100R between each output. Curious to know the reason too.
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