Pass B1

[captrajesh]

Can we replace the current volume pot in PM1 with a lightspeed attennuator? If so, what are the changes required?

Yes provided you can supply 7.5-12V DC or regulated 5VDC and your PM1 has analog volume control. I already mentioned that diagram in some post here while connecting CCW, W and CW point of volume control with LDR Volume Control.
- W is connected to middle terminal of volume pot
- CW is connected to terminal of volume pot which contact with middle when turned clockwise direction.
- CCW is connected to terminal of volume pot which contact with middle when turned counter clockwise direction.

Sounds good but what is the longevity of the LDR? I heard that the LDR changes its value with passage of time. If it is so, I'm sure it would affect the volume control.

If my understanding is wrong and the LDR is as reliable as other electronics, I'd like to buy one more LDR for my AP PM1.

 

[omishra]

Sounds good but what is the longevity of the LDR? I heard that the LDR changes its value with passage of time. If it is so, I'm sure it would affect the volume control.

If my understanding is wrong and the LDR is as reliable as other electronics, I'd like to buy one more LDR for my AP PM1.

LED is the source of light in LDR and it has finite life if used to full brightness (@25 mA). Here that max current case arises two times.

1. When we keep volume at zero maximum bright LED in shunt LDR (L2, R2)
2. At full volume maximum bright LED in series LDR (L1, R1).

This perticular design which we used, volume between any place other than 0 is safe as max is controlled here to 8mA. That will maximize the LED life. It is said 24x7 should be 20 years at middle volume level. That's time when LED reaches to half of its brightness.

So it will live after me as my volume pot never touches to zero/max.

 

[gobble]

Since B1 is a Passive Pre (w/o any gain) and volume control, it can be connected to active Preamps (w/ B1 volume to max) to get more dynamics.
...
I am planning to connect it to my Acoustic Portait PM1 tube pre to get a tube flavor.

Why would a passive pre add more dynamics? Better impedance matching? What is sub-optimal about the current impedance (no pun intended) across the interfaces. Is the CDP having too high o/p impedance? Or existing pre having too low a Zin?

I thought that loss of dynamics was the main curse of passive pre's.

Why would a solid state pre add tube flavor to the sound?

One more gear unit in the chain means one more expensive IC. If you dont use the same IC in both places, the 2nd IC will also affect the sound differently.

--G0bble

 

[cmsajith]

Why would a passive pre add more dynamics? Better impedance matching? What is sub-optimal about the current impedance (no pun intended) across the interfaces. Is the CDP having too high o/p impedance? Or existing pre having too low a Zin? I thought that loss of dynamics was the main curse of passive pre's.

Adding an active pre adds more dynamics to a passive pre (i am using only the buffer stage)
Ref: http://www.dms-audio.com/nelson-pass-b1-buffer

Why would a solid state pre add tube flavor to the sound?

PM1 is a tube pre

One more gear unit in the chain means one more expensive IC. If you dont use the same IC in both places, the 2nd IC will also affect the sound differently.

Planning to integrate the B1 to PM1 by changing the volume pot of PM1 with Lightspeed and adding the buffer of B1 for high impedance

--G0bble[/QUOTE]

 

[omishra]

You mean we need to purchase an additional 330 or 390 ohm, >2W resistor and connect it in series to the wire from PSB to the LDR?

Today I verified with new transformer. We need to add 330 ohm, 2W in series of +ve wire of LightSpeed Supply wire. Also 28V at the output could be just reached. If more headroom is required then 'R8' need to be reduced to 200-220 ohm. I will post new diagram for connection.

It seems that I owe some shipping charge from everyone. I need to spend that. I will buy those parts and send those to everyone, sundry 2-3 Rs item but better done at once. ( But by simple/registered post).

 

[captrajesh]

Hi Mishraji,

Got my PSU & LDR kits.:yahoo: Could I ask for one more LDR? I need it for replacing the stepped attenuator on my pre. May be you could send the kit along with the resistor

Off they go for soldering tomorrow. What is the latest on the trafo?

Rgds


Rajesh

 

[omishra]

Hi Mishraji,

Got my PSU & LDR kits.:yahoo: Could I ask for one more LDR? I need it for replacing the stepped attenuator on my pre. May be you could send the kit along with the resistor

Off they go for soldering tomorrow. What is the latest on the trafo?

Rgds
Rajesh

I don't have extra kit. We got to make only 12 PCBs and out of 60 LDRs only 50 are matching. So only 2 extra does not make complete group of 4 for one kit. There are some bigger tolerances in remaining, not suitable for audio applications at least. That's the situation now.

I saw and tested that transformer. Order can be confirmed as it seems fine to me. It has Electromagnetic shield, long 10" leads and confirms size standards. Especially bobbin and core material are excellent. Power rating looked + than expected. In test sheet they mentioned 1KV test for 1minutes :thumbsup: These got passed

Price remained same only taxes go away as we pay cash. Should we order according to earlier list?

 

[Audiodoc]

Yes I too am waiting. As you know i want two second one being 0-18V, 1A.

 

[quad]

Om, please add one transformer for me too. Thanks!

 

[stereorules]

I confirm for the trafo ...

 

[captrajesh]

I don't have extra kit. We got to make only 12 PCBs and out of 60 LDRs only 50 are matching.

I thought Uraih Dailey supplies matched LDRs.

Is it only the LDRs or is it that we are short of boards and other components as well?

Should we order according to earlier list?

Yes, yes I want one trafo of 22-0-22, 30VA and remember one of 34-0-34, 400VA

 

[sachu888]

I thought Uraih Dailey supplies matched LDRs.

Is it only the LDRs or is it that we are short of boards and other components as well?



Yes, yes I want one trafo of 22-0-22, 30VA and remember one of 34-0-34, 400VA

Yes Uraih sells matched Ldrs @ $18+shipping,they are costly IMO Single Pair of LDRs
We don't have any board for LSA

Regards,
Sachin

 

[omishra]

I thought Uraih Dailey supplies matched LDRs.

Is it only the LDRs or is it that we are short of boards and other components as well?

This cost us rs 300 /pair. Compared to USD 17.5 + Shipping.
Other components are not that costly except PCB itself, and locally available within 100Rs.

List updated -

22-0-22, 30VA
1. Gopib - 1 Nos
2. Stereorules - 1 Nos
3. Captrajesh - 1 Nos
4. AudioDoc - 1 Nos
5. Santhosh - 1 Nos
6. jetlag - 1 Nos
7. cmsajith - 1 Nos
8. gobble - 1 Nos
9. quad - 1 Nos

18-0, 30VA
1. AudioDoc

34-0-34, 400VA
1. CaptRajesh

 

[josephjohnt]

Hi omishra,

what is the cost of the 22-0-22, 30VA.

Thanks

 

[gobble]

Yes please tell us the final cost so I can make one final payment rater piecemeal every few days.

I received the 2nd parcel for Santhosh and 2 LDR kits yesterday.

--g0bble

 

[gobble]

This cost us rs 300 /pair. Compared to USD 17.5 + Shipping.
Other components are not that costly except PCB itself, and locally available within 100Rs.

List updated -

22-0-22, 30VA
1. Gopib - 1 Nos
2. Stereorules - 1 Nos
3. Captrajesh - 1 Nos
4. AudioDoc - 1 Nos
5. Santhosh - 1 Nos
6. jetlag - 1 Nos
7. cmsajith - 1 Nos
8. gobble - 1 Nos
9. quad - 1 Nos

18-0, 30VA
1. AudioDoc

34-0-34, 400VA
1. CaptRajesh

This single trafo will supply power to the complete kit including the LDR pcb I hope?

--g0bble

 

[sachu888]

This single trafo will supply power to the complete kit including the LDR pcb I hope?

--g0bble

Yes

Regards,
Sachin

 

[omishra]

Joseph, gobble: I got it in Rs 625 with 700mA (30VA). But now 22-0-22, 1A (30VA) will cost Rs 500 approx + shipping at actual; as my brother will pay in cash and collect personally.

H'bad people can collect it personally. This is heavy item approx 30VA as >500gms and 400VA is more than 4Kg. Please don't pay now. This need to transfer to my brother. So please wait till Monday. I am just put one of them into my tuner and running it for 24hrs.

 

[captrajesh]

400VA is more than 4Kg.

WTF 4 Goddamn KGs!!! Whoa!!!

Since my amp's power rating is 125x2 RMS @ 8 Ohms and 250x2 RMS @ 4 ohms and 500 RMS in bridged mode, what do you guys suggest 300VA or 400VA?

 

[omishra]

WTF 4 Goddamn KGs!!! Whoa!!!

Since my amp's power rating is 125x2 RMS @ 8 Ohms and 250x2 RMS @ 4 ohms and 500 RMS in bridged mode, what do you guys suggest 300VA or 400VA?

Then that will require 600VA if you going to squeeze 500W RMS.