D1 I/V Stage Finished.

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#125
hi everyone, how the d1 stage? I have parasound dac 1500. looks like it is VERY similar to pass labs d1-similar receiver, digital filter, DAC chips. except analog stage. there are lot of analog devices opa, lot of black gates = very long signal path. the sound is very warmth and analogic but it is not ultimately dynamic and soundstage seems not the best I have ever heard. it is very well built with very good parts, but seems need new analog stage 😉 I am absolutely newbie on digital. here is the spec of my dac- cs
four bur brown pcm 63p-k highest grade dac push-pull for each cannel and fully balanced. dac has about 110 000uf PS, 9 diferent power suplies , 3 transformers and etc. I wonder is it posible to convert it to exact pass labs dac. transformers are 2x12, also 2x21.7 and again 2x 21.7V
 
#126
Hello,

I just try the D1 Jfet IV in attached diagram. The sound is really good on my PCM63 DAC. The offset at input is also more stable (easy) to adjust compare to original D1.

Spencer
 

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#130
Hi Spencer,

I am not too familiar with the transistors. Are you using the 2SK170, 2SJ74 for your circuit.

What is K389BL? I am not able to locate a datasheet for the K389BL.

Your DAC looks like a Lite DAC50. Did you buy it in Hong Kong?

Thanks
 
#131
Hi,

Yes I use 2sk170BL and 2sj74V.

2sk389 data sheet refer to http://www.datasheetcatalog.com/catalog/p51240.shtml

Note two matched 2sk170 = 2sk389.

389 is too expensive to get and 170 is still available at reasonable price.

Last month I am able to find 2sk170BL in YH - Sim Lim Tower basement but now all sold out at 0.8 per. Luckily I can now easily find in ShenZhen electronic market at half price but min 200 pcs one bag. I think YH still have 2sJ74V.

Regards,
Spencer
 
#133
Thanks Spencer. I will check out YH over the weekend.

What is the change in the performance of the Lite DAC50 when you removed the passive I/V and tube buffer to replace them with the JFET I/V?

Can I have your email so that we can take the discussions about the DAC50 offline? Thanks
 
#134
Original tube I/V is just average performance, Russian tube sound like no imaging and poor resolution. Use Nelson Pass I/V is two levels up, Jfet is even better on high frequency. You must try before you can believe. In simple term, well design discrete I/V is much better than Op-amp or tube.

Note the original power supply layout on the DAC is also no good. Need to ensure there is a CLC for each supplier pin/voltage of each PCM63. Thus total use 8 CLC from the two regulators on +/- 5V.

I also put 10uF MLCC capacitors in parallel with Tantanum cap solder direct from DAC supply pin to ground.

All receive IC and DF IC also need better power supply decoupling by MLCC.
 
#136
Thanks Spencer for your comments.

I am sourcing for a set of Lite DAC50. I hope to use it for my experimentations with the D1 I/V as well as the Jfet I/V stages.

I may add in a passive preamp stage into the DAC50 based on the passive transformer circuitry.
 
#138
Hi Spencer, 1700 rmb is considered cheap to some of our forumers here 🙂

I do not know where to find the kit set and you are right about the PCM63K chips. They are not easy to find. Monarchy does not sell new PCM63K anymore. They have pulls at US$25 each though.

I have sent you a mail.

Btw, fyi, the Monarchy M24 DAC is a Lite DAC50 on steroids

An externally hosted image should be here but it was not working when we last tested it.
 
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