Salas hotrodded blue DCB1 build

[ppcblaster]

Thanks

[Nikon1975]

So, have been reading all the thread, and I would like your opinion on the following matters. I think I will try the 10R and the 3R3 versions:

Power transformer: I live now in Japan that has 100 V, but I will move sooner or later back to Europe. So I was thinking to buy a transformer 115/230 primary and 18-0-18 out. This will give my 15.6 V in Japan and 17 V in Europe. The alternative is to have a 15-0-15 V secondary and run at 13 V while in Japan. I can change resistors when I move.
I have to choose between the R26-22 and the R26-34 by DIYclub

What do you think is better ?

Potentiometer: I think I will choose a 20 K pot. Does it make sense to use a stepped attenuator ? advantages and disadvantages ? I'd love to install something that I can remotely control in the final build, suggestion ? Lightspeed is also an option.

I will use the buffer mainly between the DAC and the Power amplifier. The DAC (DAC-END2) has a tube output with 1 5687 with the sections in parallel and 1 mF output cap. I have various amp, but they all start with a tube (5842, 6N1P, 12AX7). I plan to play with i/v stages anyway.
Does it make sense to use two buffers before and after the pot. It looks like in the Pass Lab threads they think this is the best solution.

For the resistors I think I will use Caddok for the signal. I am tempted by the Foil one for the 220R, but they cost 15 $ any cheaper source ?

Also, I did not find a source for the pot. Any suggestion ? I find only 10k or 50k.

Output caps: Am I right thinking that with OPTs before the speakers there is no way of getting DC on the speakers ? Worst case scenario, if there is a problem with the buffer, the bias of the input tubes will change if I have some DC, although with leds on the cathodes this should not happen.

Thanks,

Davide

[Nikon1975]

Could this fit as pot choice ?

Hi-End Volume Control DIY Kit,LED, Remote Control /V-03 - eBay (item 290485343961 end time Nov-07-10 04:10:12 PST)

It says max out impedance 22K.

Thanks,

Davide

[Nikon1975]

In case I go for the stepped attenuator. Do I need a string attenuator, or can I use a shunt attenuator ?

Thanks,

Davide

[Salas]

The RC kit is fine for DCB1.

15-0-15. 13V is still enough. Running hot rod you skip much CCS heat VS 18-0-18.

See about Vishay RNC90Y too. Bulk foil.

No DC when OPTs.

[Nikon1975]

Mouser have the 215 ohm Vishay RNC90Y would they work ?

D.

[LucasAdamson]

Wow! not cheap, those!

You could also try the highly regarded Vishay Naked Z foils if you're spending:

Vishay VAR-Series "naked" Z201 Z-FOIL RESISTOR

Regarding values, Nelson Pass originally had them at 1K, and they were reduced by popular consent/dissent, (based on reports of tighter bass with more drive) to 220R, which Papa agreed with I believe, warning however, that the lower value you go, you increase risk of parasitic oscillation. So, you can choose any similar value and be safe, and go up to 1K, but I can confirm that it sounds better near to 220R.

[Nikon1975]

What about using one or two buffers ? (before and after)

Lucas, I saw that, I was looking for a cheaper source of them. 15 $ for a resistor make me think about. I mean, I have other cheap resistors between my DAC and the speakers (not many around 5). Unless I don't replace them all, I am not sure it would be worth it.


Thanks,

D.

[Tea-Bag]

Vishay Z-Foils. TX2575. I dont think you'll regret the investment, especially if there is something else in their first to try.

Direct from texas instruments I get them for for about 10.00 each before shipping and handling. That may be another $10.00 for that. Maybe more for asia shipping. Anyone can order from there I think, even just 1 resistor.

Use caddock for 220k, 1M anything else IMO.

[LucasAdamson]

I am using PRP Audio grade Metal Film resistors, which cost 30c each. The price/quality ratio for these is unsurpassed, period.

I think it's pretty ridiculous to spend that kind of money on resistors before you've let the circuit settle in - like using $30 silver/gold film caps in a power supply or gold wiring.

For me, such resistors would be a potential tweak for a year or so down the road, if I felt the need. That way you can hear for yourself if you've wasted you're money or not.