Lightspeed Attenuator a new passive preamp

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#1,721
Yeah, Andrew, but then we have to adjust the knob and switches. one for controlling the shunt ldr and some switches for the `fixed' series ldr.

Anyway, what I am interested is if the ldr as resistance sound better than those hi-end resistors at the same setting. Please if someone have ldr part that can do some comparison and report back?

Regards, Philip
 
#1,722
I plan on coming back on the 4th and having 300LDRs to match so if you have been thinking about getting some matched pairs man this is the time when I will have them closer than ever. The more you have the closer the matching gets.
Thanks
Uriah [/B][/QUOTE]

I'm in for 4 sets of dual pairs Silonex LDR
 
#1,724
So please be gentle... its my virgin run at PCB layout!:cannotbe:

So the idea here is a lightspeed MK2. There are a couple of things I have done to suit what I want....

1. So first up is I have an alps pot fit right on the board. I reckon this is a fairly standard pin out so hopefully many different pots would fit here.

2. I wanted to be able to have a raw AC voltage input so you will see that input, the pins are good for a standard 2 pin terminal block, 2.54mm/0.1" pin spacing.

3. This is the neat bit - the raw DC then is fed to a teddy reg which sits on top of the pcb, on pins. So you will see pins for raw DC to teddyreg, GND point for the teddyreg and then the teddyreg output to the alps pot. The nice bit about this is that you can power up the teddy reg off-board, adjust your output voltage and then fit it down into scokets on the board.

I've included a fairly big ground plane to allow for plently of space for ground points. All the traces are minimum of 1.5mm to allow easy home etching.

So now my request:😀 😀

:smash: Could you gurus have a look over it and make sure I have it laid out correctly (ie that it will work!) and also if anyone has any suggestions for improvement.... please let me know.

Credit due to George for letting us know about this. I have used the mk1 type lightspeed as volume control and have been pretty impressed with it, so I was thinking of etching this board for my upcoming B1 build.

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



Fran


EDIT: eeek. its amazing what you see after you post. The ground of LDR 3 and 4 aren't connected to the ground plane!
 
#1,726
No, I am just trying to read and catch up in between other threads, work and son.

I am still waiting for details of the PCB BG. Both main brd and tx/rx brds.

I want to build this with a tube follower circuit for a friend and would like to make a complete package for him.
 
#1,727
Lightspeed remote control

Hi Folks,

I am running a couple of days behind schedule, partially due to answering all the e-mail enquiries about technical issues regarding the Lightspeed remote control . It is ok to e-mail orders for boards/modules, as my office lass can deal with this, but if you have any technical questions will you please post them on the Lightspeed thread. Please remember I have to run a business through the week. This will help me tremendously as I will only have to answer questions once and the information will be available for others. It will also keep the thread active and maybe help with George's push for a passive preamp forum for the Lightspeed.

Many who wish to build the VCCS themselves have expressed concern about dealing with surface mount components. This can be tricky so I have re-organised the VCCS and receiver layouts to minimise surface mount components There are 3 left on the VCCS board but these are not too small to deal with. I will be continuing with the receiver board on Monday and will hopefully be able to send the CAD files on Tuesday morning once I have checked them thoroughly with a fresh head.

I should receive the costing information for the Transmitter/receiver boards by Thursday and I will post this as soon as I can.

Regards
Paul
 
#1,728
I am in the process of setting up a dedicated work bench / solder station.

To help "encourage" a GB I will offer to solder on the SMD components for the US buyers.

I got tired of resisting assimilation so I bought a new soldering station and set up dedicated space specifically for SMD work.

I am still trying to read through and find the details of the GB.



I will post a few questions / facts here:

Assumed facts:

1. Cost = 65 something(pounds, Euro, dollars, rupees)
2. Item = Single PCB for pwr, resistors and LDR's.
3. In progress = design for remote control PCB's, cost unknown.


Questions:

1. Link to proposed main PCB?
2. Chance of it being combined with the rx'er?
3. Chance of the main PCB being combined with a unity buffer of some type? (Pass B1, Tube, SOAP)
4. Time line?
 
#1,729
troystg said:


Questions:

1. Link to proposed main PCB?
2. Chance of it being combined with the rx'er?
3. Chance of the main PCB being combined with a unity buffer of some type? (Pass B1, Tube, SOAP)
4. Time line?
Click to expand...

Congrats on the soldering station. What did you get?

I'm in for a GB. But, I wouldn't need the LDR's as I'm purchasing those from Uriah.
 
#1,730
marc brown said:


Congrats on the soldering station. What did you get?

I'm in for a GB. But, I wouldn't need the LDR's as I'm purchasing those from Uriah.
Click to expand...


Likewise I got the LDR's from Uriah. I was not offering to supply parts, merely do the soldering.

BUT... On second thought since there are not many parts involved I could...

Believe it or not I bought a "cheap" Radio Shack re-badged Maddal unit.

I got this for a couple of reasons.

1. The "preset" buttons that I can switch between hole through and SMD quickly.
2. Very precise tips.
2. Very affordable.


http://www.radioshack.com/product/index.jsp?productId=3132686

It is a re-badged this:

http://www.ntscope.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=MTC&Product_Code=AT201D
 
#1,731
Lightspeed remote control

Hi Troy,

Group Buy: Cost of an unpopulated printed circuit board for VCCS is £12 and a built and tested module without LDRs is £60 (see post 1705). For those looking for LDRs they are available matched from Uriah. The basic carriage and packing charges are set out in post 1706. Ordering more than one item is likely to change the carriage charges so it is best to confirm what you want to order before actuating a payment.

Please note that Paypal payments can be sent to paul@paulhynesdesign.com and these must be converted to GBP (Pounds Sterling) before transmission. I am not paying for currency conversions. If you send funds in other currencies without paying for conversion your order will be rejected.

I have yet to write the application notes and this will be done once the board CAD files are on the way to the PCB manufacturer. Each purchaser will receive an application note with their goods, and to make life easier regarding component ordering, for people building the module from scratch, I will post the full application note on my website at the next website revision.

The VCCS board will be kept separate from the receiver board, as one size will not fit all for preamp projects as case choices will vary. The receiver board can be mounted behind the front panel and the VCCS board can be mounted at the rear of the case close to the input/output sockets. Also not everyone will want to have a buffered Lightspeed so I am not adding a buffer to the board. If you want or need a buffer there are plenty of options around for this function.

Time line – I have checked with the PCB manufacturer today and he has told me their current lead time is now 15 working days from receipt of CAD files. On the assumption that the lead time does not change by next Tuesday (If the manufacturer takes any orders from elsewhere between now and Tuesday this will affect lead time), this would mean I should have the boards by 30th March. Orders will be dispatched in order of placement. All unpopulated boards should be on the way within a few days, modules will have to be built and tested first and the lead time will depend on my business work schedule but rest assured I will endeavour to get them out as fast as I can.

Regards
Paul
 
#1,735
George,
G'day again,

I'm still enjoying your Lightspeed.Even more so,as I've changed my active crossover from the Behringer CX-3400 to the Accuphase F-25.
A new power amp has also driven home just how much more there is to the Lightspeed.

The question I wanted to ask here George was:
Have you listened to any iterations of Nelson Pass' B1 buffer yet?

Also,I recall that you said that the best performing buffer you had heard was a tube one.Is it commercially available,or a 'one-off'?
Thanks
 
#1,736
theophile said:
George,
G'day again,

I'm still enjoying your Lightspeed.Even more so,as I've changed my active crossover from the Behringer CX-3400 to the Accuphase F-25.
A new power amp has also driven home just how much more there is to the Lightspeed.

The question I wanted to ask here George was:
Have you listened to any iterations of Nelson Pass' B1 buffer yet?

Also,I recall that you said that the best performing buffer you had heard was a tube one.Is it commercially available,or a 'one-off'?
Thanks
Click to expand...

Glad to hear my Lightspeed Attenuator is still serving you well. Yes that Accuphase xover is a nice piece of gear, I had to repair one once for a client.
As for the Nelson Pass B1 buffer, I have not stuck one on the rear of the Lightspeed Attenuator as yet, but from all my experience, no buffer is still the best buffer, unless you have impedance matching problems, then a buffer is a solution, unless you can fix the impedance mismatch.
This was one of the reasons Nelson Pass designed the buffer for the Lightspeed Attenuator so it could drive his amps as well, which are nearly all very low input impedances, below 20k. And there are some other amps, not just his I have to add.

The best tube buffer I have heard is one that was first used in an early high end tube Tektronics Osciloscope (attached below) fondly called now as the SLCF (super linear cathode follower) buffer.
 

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#1,737
georgehifi said:


Glad to hear my Lightspeed Attenuator is still serving you well. Yes that Accuphase xover is a nice piece of gear, I had to repair one once for a client.
As for the Nelson Pass B1 buffer, I have not stuck one on the rear of the Lightspeed Attenuator as yet, but from all my experience, no buffer is still the best buffer, unless you have impedance matching problems, then a buffer is a solution, unless you can fix the impedance mismatch.
This was one of the reasons Nelson Pass designed the buffer for the Lightspeed Attenuator so it could drive his amps as well, which are nearly all very low input impedances, below 20k. And there are some other amps, not just his I have to add.

The best tube buffer I have heard is one that was first used in an early high end tube Tektronics Osciloscope (attached below) fondly called now as the SLCF (super linear cathode follower) buffer.
Click to expand...
George,
would I be wrong in speculating that the super linear cathode follower circuit,is also incorporated into Allen Wright's Vacuum State Electronics components?
I'm certain that he borrowed the same circuit from the same implementation......
Thanks for your reply(and your Lightspeed).


🙂
 
#1,740
Yeah, he was pushing the DCM Time Windows, I did'nt think much of them.
Then there was a time he was at my friends place who had Magnplaner Tympani 1D's, and Allen bought his mono block theater amps that were driving them, then with the aid of a couple of freinds to help I went out to my car a bought in my 100kg water cooled pure class A 150 watter
http://www.diyaudio.com/forums/showthread.php?postid=1119883#post1119883
and blew the theater amps into the next century.
"Sorrry Al one tends to hang onto memories like that"

Cheers George
 
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