• These commercial threads are for private transactions. diyAudio.com provides these forums for the convenience of our members, but makes no warranty nor assumes any responsibility. We do not vet any members, use of this facility is at your own risk. Customers can post any issues in those threads as long as it is done in a civil manner. All diyAudio rules about conduct apply and will be enforced.

GB for DC coupled B1 buffer with shunt PSUs

Jump to Latest
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
What kind of impedance does the Lightspeed present to the signal when at max volume? A simple check with a DMM set for Ohm will do. Thanx.
 

Attachments

  • Lightspeed-Passive-Attenuator-Schematic.png
    Lightspeed-Passive-Attenuator-Schematic.png
    50 KB · Views: 587
U

udailey

Member
Joined 2008
picasaweb.google.com/udailey/MyRef#
The total input impedance should be pretty steady. It waivers a little but for the most part is the same as at zero volume. The series resistor and shunt resistor in the LDRs vary in resistance opposite each other so if one goes up 2k then the other goes down 2k so Rtot is still the same. If one resistor is fully "ON" then the resistance is from 30-70Ohms and at the same time the other would be nearly "OFF" and assuming that input impedance for that matched set was 10k then that "OFF" resistor would really be at around 10k.

Last time I had matched 549 LDRs and ended up with sets with values from 5k-20k with most falling around the 10k-13k range. So input impedance for the average matched set would be 10k-13k. Might be different this time. Usually I get in the 7k-10k range.
Uriah
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
That will do well for our little project here. Thanks. I hear that the Lightspeed is THE transparent attenuator. Well done. Of course I would recommend it to be included in the same box with the DC B1 so to avoid an additional set of interconnects and RCAs that go towards defying the transparency goal and worsening the budget.
 
U

udailey

Member
Joined 2008
picasaweb.google.com/udailey/MyRef#
I agree Salas. Minimize contacts and interconnect as much as possible. If you can get the B1 inside your amp case and mount the LDRs directly on the B1 board then the B1 directly on the amp inputs even better.
I HAVE experimented with something similar and there ARE sonic benefits to removing that extra RCA cable and the extra RCA plugs/jacks.
If you could run just one RCA from your CDP to your amp it frankly sounds better.
Uriah
 
W

woodturner-fran

Member
Joined 2006
Well, I can do an experiment, but it will be a few days yet.

Background:
I originally planned to do a lightspeed with the B1 I've just built. However, my lightpseed had, err, issues (oh go on then, the issues were with my build!:rolleyes:). Anyways, I stuck in a 50k stepped pot like the one I posted a few posts back. Thats whats in there now and sounding not too bad might I add.:nod:

However, tonight I spent some time in the workshop troubleshooting the lightpseed and I believe I have it sorted now:up:. So what I plan on doing is using the B1 as it is now, with the stepped attenuator in place, and then say next week, replacing it with the lightspeed to see what the difference is. I probably will get another pair of ears along with mine to help judge.


****************************

OT... and further background... just to declare interests. I've been using a few of the older version lightpseed for a while now and rate them pretty highly. They are easy to use, work well and most importantly sound great. From memory theres nothing separating the original lightspeed (an older version with just one pair of LDRs) and the stepped pot mentioned above. However, either one was so far ahead of an alps blue velvet it ain't funny.

A while back I repaired an airtight amp from a friend of mine. These amps ain't cheap! Anyway, what do i see when I open her up? bloody alps blue velvet. Think they would have put in something a bit better than that. I know a bunch of pretty high end amps that use them. They sounded so veiled in the 2 amps I tried them in......

end of OT
****************************



Fran
 
A

AlanElsdon

Member
Joined 2003
woodturner-fran said:
However, tonight I spent some time in the workshop troubleshooting the lightpseed and I believe I have it sorted now:up:. So what I plan on doing is using the B1 as it is now, with the stepped attenuator in place, and then say next week, replacing it with the lightspeed to see what the difference is. I probably will get another pair of ears along with mine to help judge.

Fran
Click to expand...
Fran,

You will be very pleasantly suprised when you directly attach the LSA to the B1.

Alan
 
K

korben69

Member
Joined 2006
New BOM v3.2, some changes :

a) Input / Output Sections : Male and Female connectors + crimps
b) Rotary Switch : same as upper but 7 poles.
Female 7 poles is unavailable at Farnell's today, it can be done using 1x3p + 1x4p.
All connectors are 2.54mm spacing.
c) BOM is now showed in sections.

I've submited a question about Green Leds part N°, as I want to avoid mistakes, thanks for your qualified answer. I'll cook v3.3... :rolleyes:

korben69 said:
For the 16 x green Led ref, I think this one is more accurate :
http://www2.mouser.com/ProductDetai...=sGAEpiMZZMuus4pmcqQnzpwU6y34ia5a4Ij/Veh5DEs=
It shows 1.9 to 2.5v vs 2.2 to 2.5.
Your opinion ?
Click to expand...
 

Attachments

  • DC Coupled B1 Shunt PSU V3.2.pdf
    39 KB · Views: 167
Tea-Bag

Tea-Bag

Member
Joined 2006
Paid Member
back on topic, sorta. Protypes have been ordered. I will try to get ETA on the boards, but the lead time is 7 days, then some time to ship back. they are from China so I assume some amount of time.

Those who want to be the prototyper's, and have not emailed me privately, please do so, with your mailing address. I am only looking for prototypers who can promise a fairly quick turnaround to build and debug. It also assumes that if a mistake arises (and we know that's a slim chance) you are confortable doing some additional wiring and pcb mods as needed (think drill and razor). This way we can move forward quickly with any changes and ordering more boards for the mass's.

Tea-Bag
 
K

kannan_s

Member
Joined 2009
Tea-Bag said:
back on topic, sorta. Protypes have been ordered. I will try to get ETA on the boards, but the lead time is 7 days, then some time to ship back. they are from China so I assume some amount of time.

Those who want to be the prototyper's, and have not emailed me privately, please do so, with your mailing address. I am only looking for prototypers who can promise a fairly quick turnaround to build and debug. It also assumes that if a mistake arises (and we know that's a slim chance) you are confortable doing some additional wiring and pcb mods as needed (think drill and razor). This way we can move forward quickly with any changes and ordering more boards for the mass's.

Tea-Bag
Click to expand...

HI I sent you my contact info for Basic Prototype as mentioned earlier
kannan
 
K

korben69

Member
Joined 2006
Last edited:
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
Does not matter much. Greens just tend to bunch together easily for matching, that is why I recommended them. Academically, the yellow are the less noisy. Also if you find 3mm will stuff easier and look better on the PCB.

For example: http://www.ledshoppe.com/Product/led/LE4008.htm

Those will tend to bunch over 2V though. Look for intensities up to 3mcd.

The HLMP1700 that korben found is 3mm 1.8V and 2mcd. Perfect. http://it.mouser.com/ProductDetail/...=sGAEpiMZZMuus4pmcqQnznpa3uwzKp/1NBxnRpKrPOM=
 
grufti

grufti

Member
Joined 2004
You must log in or register to reply here.
Top Bottom