DCB1 Build

[saikatbiswas82]

For 2A or more, you can bypass those inductors. I won't suggest that PCB also. High current paths must be thick.

Thanks a lot. Will keep this in mind.

Sent from a handheld device. Some typos may creep in

 

[omishra]

Also you can replace these, if find.

2SK170 -> 2SK370
2SJ74 -> 2SJ108

I hope this may help.

 

[prasen_b]

One tweak (it's not even a mod) you could easily try: the supply for DCB1 is +/-10V. Using the trim pots on the OPS, you could try different voltages like +/-12V, 12.5, 13, 13.5, 14, 14.5, etc and see if you like the sound of a voltage more than the original 10.

I've not experimented with DCB1 but I'd played around with a similar buffer, and the results were very interesting.

http://www.hifivision.com/diy/63668-bluespower-dual-shunt-regulated-power-supply.html#post714214

It's always great fun to try alternate PSUs. If you have patience, time and inclination try shunt regulated supply.

I am not sure about trying different voltages. I went through your findings shared in the link and it seems you had to change something in the buffer PCB for trying out the higher voltages.
After the attenuator the PSU is the next thing I would like to upgrade. And I will try out the shunt supply.

 

[jls001]

No change needed in buffer.

If you're using OPS power supply, simply use the trim potentiometers on the OPS board to vary output voltage.

 

[prasen_b]

You are okay, no need to worry. Continue with that.

Good to know that. Any comments about using higher rail voltages as suggested by joshua. Also at the start of this thread you suggested using some capacitors at the power rails of OPS. Does it also apply to the latest OPS that I believe I used?

I have a question about the potentiometer. I believe the current consensus is to use a 20K pot. I am using the same value currently but the loudness increases suddenly after 11 clock position. My amplifier has an input impedance of 47K and my DAC an output impedance of 80.
My current understanding of the impedance interaction is the RCA input to the DCB1 and from there to the potentiometer and from there to the output RCA.
So in my system the impedance ratio are as follows

DCB1 input impedance = 220K
DCB1 output impedance = 250

- DCB1 input/DAC = 80/220K = 2750
- potentiometer/ DCB1 output = 20K/250 = 80
- Amp input / potentiometer = 2.35

So my question is shouldn't 10K be a better value for the potentiometer, considering that most amplifiers have an input impedance of around 30K?

 

[prasen_b]

Powersupply makes lot changes in the sound.Capacitors which I got with powersupply are made by " Samwha". If one uses Elna or Panasonic,sound may improve further.Also voltage of transformer does matter.
For DCB1 even 12-0-12V should be fine as you get around 16+V as DC after rectifier and regulator LM317 needs to convert it to 10-12V. So probably less noise generated. Its is said to have 3V more voltage more than the output voltage(regulated) for better results.

Yes I upgraded the PSU capacitors to panasonic.

 

[Hari Iyer]

2sk170/2sj74 matched components are available from diyaudiostore and ebay us.

Sent from a handheld device. Some typos may creep in

Its not available anymore in diyaudiostore.

Its still available at ebay us but a single piece is showing $80 hyeah:hyeah:

 

[manniraj]

Its not available anymore in diyaudiostore.

Its still available at ebay us but a single piece is showing $80 hyeah:hyeah:

Hari, contact this member "liubincalvin" on the diyaudio.com site. He sells genuine closely matched ones. I had brought from him the "IRFP240 and IRFP9240" and I think he has 2SJ74/2SK170.

 

[Hari Iyer]

Yes 2 pairs for stereo is required by me. There are couple of them available at Mumbai LT Road, but all are printed Chinese stuff. Not original. They get easily wiped off with acetone.

 

[saikatbiswas82]

Let me know if you need 2SJ74/2SK170 matched pairs.

Dear hifimar, I might need few pairs going forward. Could you please let me know the price? Are they BL or GR?

Sent from a handheld device. Some typos may creep in

 

[omishra]

Good to know that. Any comments about using higher rail voltages as suggested by joshua. Also at the start of this thread you suggested using some capacitors at the power rails of OPS. Does it also apply to the latest OPS that I believe I used?

I have a question about the potentiometer. I believe the current consensus is to use a 20K pot. I am using the same value currently but the loudness increases suddenly after 11 clock position. My amplifier has an input impedance of 47K and my DAC an output impedance of 80.
My current understanding of the impedance interaction is the RCA input to the DCB1 and from there to the potentiometer and from there to the output RCA.
So in my system the impedance ratio are as follows

DCB1 input impedance = 220K
DCB1 output impedance = 250

- DCB1 input/DAC = 80/220K = 2750
- potentiometer/ DCB1 output = 20K/250 = 80
- Amp input / potentiometer = 2.35

So my question is shouldn't 10K be a better value for the potentiometer, considering that most amplifiers have an input impedance of around 30K?

About big capacitors, yes i added those big capacitors but not required. Still adding nice Panasonic 1000uf or more does not harm. It's placebo effect IMO. I used keltron caps on board, hence I added those big caps.

I did not understand your calculation about impedance. But 25K volume pot is okay for all sources. DCB 1 output impedance is 50ohm. Do not go by mere resistance values.

 

[jls001]

I've tried 50K CITEC and Alps Bluevelvet, 20K I don't remember brand and 10K stepped from eBay Hong Kong. I think 10K is the ideal value.

PS: has anyone tried the new stepped pots from the Audiocrafts? I got 10 and 20K but lazy to change

 

[omishra]

I've tried 50K CITEC and Alps Bluevelvet, 20K I don't remember brand and 10K stepped from eBay Hong Kong. I think 10K is the ideal value.

PS: has anyone tried the new stepped pots from the Audiocrafts? I got 10 and 20K but lazy to change

But many were unhappy with 13K LSA.

 

[hifiramr]

Stepped pots from the Audiocrafts is far superior than Alps Blue Velvet I have used for JC2 preamp build by replacing Alps with much improved result.

Alps old black beauty is also very good and better than blue

 

[ajeshkumarts]

Stepped pots from the Audiocrafts is far superior than Alps Blue Velvet I have used for JC2 preamp build by replacing Alps with much improved result.

Alps old black beauty is also very good and better than blue

Hi Hifiramr
Please post a link to the same on theaudiocrafts

 

[hifiramr]

The product is not listed in there site please contact him in the website info

 

[spirovious]

Can dc voltage be kept more than 12-0-12v for dcb1?
B1 jefet can accept 22-24v.
So was wondering.

 

[doors666]

Can dc voltage be kept more than 12-0-12v for dcb1?
B1 jefet can accept 22-24v.
So was wondering.

if it drops 12v at 10ma, giving about 120mw power dissipation. It will run quite hot.

 

[vbutani]

I want to build DCB1 but not sure where to get PCB and parts, please advise.

 

[jls001]

I want to build DCB1 but not sure where to get PCB and parts, please advise.

Please message @sachu888 . He might still have the kit.