XVR1 active crossover, discrete active stage

promitheus · 19th July 2002, 03:02 AM

Hello,
does anyone have a real circuit diagram of the active stages in the pass labs XVR1.
There is a general schematic but it has no parts list.
Any ideas would be helpfull.

rtirion · 19th July 2002, 10:08 PM

In my quest for a buffer, I have made this up so far.
This is only a draft. I have not yet build it.

Regards

HarryHaller · 19th July 2002, 11:22 PM

I'll bet Passlabs does.........

H.H.

promitheus · 19th July 2002, 11:35 PM

That´s about what I also had in mind, I was trying to find the correct resistor values today in simulation. Have you simulated or built thic circuit yet ?

Mr. Pass does this circuit have anything to do with the new active crossover that will be posted soon, or will that one be totaly different ?

rtirion · 20th July 2002, 12:00 AM

As I mentioned before I have not build it. Yet.

Just simulation. Load was 100 Ohm and up. The "simetrix" phase margin shows around 50 deg. -3db down at aprox. 900khz.
Not to bad, I think.

Let's put some better transistors in, and this could become a real circuit.

Regards

promitheus · 20th July 2002, 12:07 AM

I am trying to make a dicrete opamp like this for an analog output for a new DAC I am building. It has 4 opamps int original design and I dont want to use them. I prefer to put a discrete stage instead.
I saw the simplified circuit in the Pass active crossover. I think it is what I want. I also like the Borbeley FET cascode line stages but are not quite my taste.
What you designed is really really good.
the 2SK389 is one of the best around and the BC550C are also low noise very good transistors. Do you mean to change the output transistors ?
The BC337 and BC327 are also very good high current BJTs.
The specs you say are very good. I will try to simulate it and tell you what I got. How do you simulate the 2sk389 btw?

rtirion · 20th July 2002, 12:16 AM

transistors
J.A.Pan makes some realy nice ones. So does zetex.
You could ask H.H. (sorry Harry, just teasing).
There is a list of really nice devices somewhere on this forum.

For the 2sk389, I use a model. If you can't find it, I can post it.

rtirion · 20th July 2002, 12:22 AM

I forgot this:

I think it is Mr. Nelson Pass or someone else at PassLabs who designed this circuit. I just did a simple implementation to start with.

Regards

promitheus · 20th July 2002, 12:25 AM

Of course this is from Passlabs, i know that. I use circuit maker to do my designs and the 2sk389 is not included in the library databank. can I use two normal fets instead ?

rtirion · 20th July 2002, 12:32 AM

model for 2sk389

.model J2sk389 NJF(Beta=51.76m Rs=8.008 Rd=8.008 Betatce=-.5 Lambda=11.22m
+ Vto=-.5275 Vtotc=-2.5m Cgd=18.28p M=.3367 Pb=.3905 Fc=.5
+ Cgs=20.07p Isr=112.8p Nr=2 Is=11.28p N=1 Xti=3 Alpha=10u Vk=100
+ Kf=92.85E-18 Af=1)

Drop two of these in, after you have added this model to your simulator, or one of its library's.

Hope this helps.

19th July 2002, 03:02 AM	#1
promitheus diyAudio Member Join Date: Jan 2001 Location: Germany	XVR1 active crossover, discrete active stage Hello, does anyone have a real circuit diagram of the active stages in the pass labs XVR1. There is a general schematic but it has no parts list. Any ideas would be helpfull.

19th July 2002, 11:22 PM	#3
HarryHaller Banned Join Date: Feb 2002 Location: Dallas,Texas	does anyone have a real circuit diagram of the active stages I'll bet Passlabs does......... H.H.

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19th July 2002, 11:35 PM	#4
promitheus diyAudio Member Join Date: Jan 2001 Location: Germany	That´s about what I also had in mind, I was trying to find the correct resistor values today in simulation. Have you simulated or built thic circuit yet ? Mr. Pass does this circuit have anything to do with the new active crossover that will be posted soon, or will that one be totaly different ?

20th July 2002, 12:00 AM	#5
rtirion diyAudio Member Join Date: Nov 2000	As I mentioned before I have not build it. Yet. Just simulation. Load was 100 Ohm and up. The "simetrix" phase margin shows around 50 deg. -3db down at aprox. 900khz. Not to bad, I think. Let's put some better transistors in, and this could become a real circuit. Regards

20th July 2002, 12:07 AM	#6
promitheus diyAudio Member Join Date: Jan 2001 Location: Germany	I am trying to make a dicrete opamp like this for an analog output for a new DAC I am building. It has 4 opamps int original design and I dont want to use them. I prefer to put a discrete stage instead. I saw the simplified circuit in the Pass active crossover. I think it is what I want. I also like the Borbeley FET cascode line stages but are not quite my taste. What you designed is really really good. the 2SK389 is one of the best around and the BC550C are also low noise very good transistors. Do you mean to change the output transistors ? The BC337 and BC327 are also very good high current BJTs. The specs you say are very good. I will try to simulate it and tell you what I got. How do you simulate the 2sk389 btw?

20th July 2002, 12:16 AM	#7
rtirion diyAudio Member Join Date: Nov 2000	transistors J.A.Pan makes some realy nice ones. So does zetex. You could ask H.H. (sorry Harry, just teasing). There is a list of really nice devices somewhere on this forum. For the 2sk389, I use a model. If you can't find it, I can post it.

20th July 2002, 12:22 AM	#8
rtirion diyAudio Member Join Date: Nov 2000	I forgot this: I think it is Mr. Nelson Pass or someone else at PassLabs who designed this circuit. I just did a simple implementation to start with. Regards

20th July 2002, 12:25 AM	#9
promitheus diyAudio Member Join Date: Jan 2001 Location: Germany	Of course this is from Passlabs, i know that. I use circuit maker to do my designs and the 2sk389 is not included in the library databank. can I use two normal fets instead ?

20th July 2002, 12:32 AM	#10
rtirion diyAudio Member Join Date: Nov 2000	model for 2sk389 .model J2sk389 NJF(Beta=51.76m Rs=8.008 Rd=8.008 Betatce=-.5 Lambda=11.22m + Vto=-.5275 Vtotc=-2.5m Cgd=18.28p M=.3367 Pb=.3905 Fc=.5 + Cgs=20.07p Isr=112.8p Nr=2 Is=11.28p N=1 Xti=3 Alpha=10u Vk=100 + Kf=92.85E-18 Af=1) Drop two of these in, after you have added this model to your simulator, or one of its library's. Hope this helps.

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