DCB1 Build

[sachu888]

DCB1 is more transparent than B1. Do you have problem in all inputs or phono only. You may find harshness in female voice especially if your cart is not align properly or Lp is damaged.

Regards
Sachin

 

[manniraj]

DCB1 is more transparent than B1. Do you have problem in all inputs or phono only. You may find harshness in female voice especially if your cart is not align properly or Lp is damaged.

Regards
Sachin

No Sachin, I have not yet heard the DCB1 on my TT. The harshness I am talking about is with my Oppo980->Audio-GD Coaxial for CD playback as well as music-pc->Audio-GD USB DAC. I also hear it over my NAD 412 tuner as well. Let me try and see with TT today. Even I am thinking that DCB1 should better but not sure whether my soldering skills have messed up something somewhere.

 

[omishra]

Actually in some cases transparency could be curse than boon. Please keep observation, I feel it should be the case on song-song basis.
Also I was talking about caps on DCB1 which decouple PS line at each JFET.

 

[keith_correa]

IMO, "transparency" in the true sense will never sound harsh and most definitely will never cause crackle. Unless there is a problem with your source material or speakers.

 

[manniraj]

IMO, "transparency" in the true sense will never sound harsh and most definitely will never cause crackle. Unless there is a problem with your source material or speakers.

I am sure that I can rule out the my DIY FH and ACA as I was using the same combination with B1. So I am presuming something wrong with my soldering skills or connections being loose or messed up. This is the first time I did soldering after my graduation. Even though I got the DCB1 soldered from Sachin but the connections with SSP,input/output and volume pot I did it myself using a multimeter checked the polarity and voltage.

 

[omishra]

IMO, "transparency" in the true sense will never sound harsh and most definitely will never cause crackle. Unless there is a problem with your source material or speakers.

My mention was towards material. I can feel the difference between individual CD quality too. Imported foreign pressings CDs sound extremely good.

I am sure that I can rule out the my DIY FH and ACA as I was using the same combination with B1. So I am presuming something wrong with my soldering skills or connections being loose or messed up. This is the first time I did soldering after my graduation. Even though I got the DCB1 soldered from Sachin but the connections with SSP,input/output and volume pot I did it myself using a multimeter checked the polarity and voltage.

We will find out the reason, if any. Please post some pics of your build.

 

[jls001]

DCB1 power rail reinforcement wiring diagram for those who want to implement it:

 

[jls001]

Here's the picture of the actual fitment. This is still a temp fitting. I will tie down the caps to the chassis later when I can find better caps:

Here's a picture of the resistor mod to the OPS. I used 470 Ohms/3W (white ceramic resistor peeking at the edge of the board), nearest value to the suggested 500 Ohms 2W. Measured value is more like 488 Ohms. So close enough.

Below is an overview of the DCB1 cabinet:

 

[omishra]

^^ C2, 100uF looks like swollen.

 

[jls001]

^^ C2, 100uF looks like swollen.

Thanks for pointing it out. Will get replacement on my next trip to Lamington Road.

Question: if the supply rail caps help, is doubling the value twice better? Asking because I've got two more caps extra

 

[keith_correa]

The tiny board sitting alone in the middle of a vast and empty cabinet looks a bit comical.

Looks like a cabinet with exactly half the current depth would have sufficed, no?

 

[omishra]

Thanks for pointing it out. Will get replacement on my next trip to Lamington Road.

Question: if the supply rail caps help, is doubling the value twice better? Asking because I've got two more caps extra

Actually I have used 2 X 15000uF, 25V which are physically damaged and removed from earlier B1. And frankly speaking I did not see benefit beyond 470uF. Still I suggested bigger values to you. It does not harm.

It started while I was experimenting with 10uF + 0.1uF. Then I did not had anything beyond 22uF & 330uF, but had 2 X 470uF. It was best I could get. So finally I got sweet spot and I distributed 4X 100uF at 4 places on DCB1 board with 0.1 paired along. I did not measure this, but quite apparent that day.

 

[jls001]

Looks like a cabinet with exactly half the current depth would have sufficed, no?

Yeah, that would be about right. Getting a good looking cabinet is challenging.

 

[jls001]

Actually I have used 2 X 15000uF, 25V which are physically damaged and removed from earlier B1. And frankly speaking I did not see benefit beyond 470uF. Still I suggested bigger values to you. It does not harm.

It started while I was experimenting with 10uF + 0.1uF. Then I did not had anything beyond 22uF & 330uF, but had 2 X 470uF. It was best I could get. So finally I got sweet spot and I distributed 4X 100uF at 4 places on DCB1 board with 0.1 paired along. I did not measure this, but quite apparent that day.

Fine, looks like we can try higher values. Let's see if it makes any difference. The only thing boring about this type of experimentation is we need to wait for proper burn-in of each new component before making an informed opinion.

 

[manniraj]

My DCB1 pictures taken today for the harshness that I am experiencing. After taking the pictures I reconnected the power cables for source selector which had a joint cables because of the distance with the older cables. I adjusted the SS to a different place and connected the power cables with a single pair of cables. But now the harshness/shrillness I am not experiencing on every song but still I feel the harshness/cracking of vocals on increase in the volume pot. So I am now having a feeling that there is something wrong with the connections with the volume pot. The reason being that the color of the cables is the same and I had connected the first/second time wrongly to the DCB1 board. After chatting with Sachin changed the CW-W-CCW connections and I was able to increase the volume otherwise during the initial connection the volume was high even with the pot at the lowest and the pot was not working. So not sure whether I did some damage because of the wrong connections on the volume pot either the DCB1 or the pot itself. Experts should comment on the same.

Thanks

 

[omishra]

Now look at RCA to SS, L,R are coming from each source and ending into SS PCB. Where the ground for each channel returns?. All L grounds and R grounds should be collected together and lands to your SSP 's each channel's ground. There it meet with PCB ground. Output ground should start from dcb1 and end on RCA shell.

Remaining grounds are taken care by ps line which connects all grounds together into power supply.

 

[jls001]

So not sure whether I did some damage because of the wrong connections on the volume pot either the DCB1 or the pot itself.

For correct pot wiring, follow below instructions:
1) Assume you are looking at the rear side of the pot, which is inside the cabinet. You see two row of terminals. Each row has three terminals.

2) Right most terminal (pin) is ClockWise. Center is Wiper. Left most is CounterClockWise.

3) From left channel volume points on the DCB1, connect CW to right most pin, W to center pin, CCW to left most pin. You can use the front row or the back row of terminals on the pot first - it doesn't matter.

4) On the second row of terminals of the pot which is not yet used after you complete the above step, repeat above steps for right channel.

Do not reverse the above connections.

Secondly, as Om already pointed out, your input signal to the DCB1 uses one twisted wire, with one lead each going to +ve of the left and right input points. You NEED to wire the -ve leads too. So use one twisted pair for each IN to the DCB1. The same applies to the OUT of DCB1. Right now, there is no path created in your circuit for return signal. Remember that a circuit is a loop. The loop must be complete for electricity to flow correctly. It seems in current scenario the signal is returning via some path since you are able to play it, but it is NOT the correct path.

 

[jls001]

Stereo pot wiring diagram:

 

[manniraj]

Thanks Joshua for sharing the pot connections but I have resolved the wiring problem the same day. But I was only concerned that I ran the DCB1 with the wrong wiring initially then realized that the pot connections look different as I was not able to increase or decrease the volume and it might have created some problems. But I am still trying to identify the issue of crackling of the voice in high pitch voices which sometimes show up in some of the songs but not all songs.

 

[manniraj]

@Om, One thing I have realized just now is that I have replaced the Opamps on the CNC and SSP with 49990 along with the DCB1. Now just to rule out the possibility of the 49990 being the culprit if I want to revert back to the old Opamps on the CNC and SSP what should be the voltage on the PSU. As the earlier B1 the voltage was +/-15v for the SSP & CNC but the DCB1 required voltage is only +/-10v.

Thanks