calling Line drive/passive pre users??

[ashok]

Parts list:

• Insulated RCA jacks - 1 pair for output, as many pairs as you need for inputs
• Bugle phono preamp - you can buy a complete kit (board + parts) from one Jack Gallagher on ebay. I do not know if he is still selling the full kit.
• DC PSU is from Marchand. Hagtech offers a PSU too.
• Opamp buffer: Simple one dual opamp IC configured as a unity-gain amplifier. I bought the assembled board from Greg Ball (SKA Audio).
• The 1:1 transformers are from Magnequest. Although other line level transformers should work well. I saw another thread in AK DIY on a tube buffer using the Edcor 10K:10K.
• Pot on the secondary of transformers is a PEC 10K stereo pot.
• Chassis is 12" x 8" x 3" Hammond made of steel. The steel was supremely hard to work with my puny hand drill.

The DC PSU has more than enough capacity to power the Bugle and the buffer.

Grounding on the secondary side of the transformer is not done inside the preamp chassis. The L/R channel grounds on the preamp output are independent.

This preamp is the 4th one I have tried. I started with a NAD 1300 series pre. It was pretty decent, but early-mid 80s vintage.

The next one was a 2C51 tube-based preamp, Gary Kaufman's design. This one had way too much gain, plus I had a stepped-attenuator. A couple of clicks, and it got way too loud.

So, I switched to the Luminous Audio Axiom passive device. This one was really good. It matched well with my system, and I enjoyed it a lot. But soon, I wanted additional inputs and the Axiom comes with only one.

On to the present version. I re-used the 2C51 pre's chassis to build this most recent edition. The sound is very nice. Plenty of detail, but not sterile. Easy to listen to.

 

[Tedrick]

I've got an Adcom SLC-505 passive pre-amp. It's on the sidelines right now waiting for a system to be built, but it's a fine pre-amp with very neutral sound and minimal, if any, sonic signature of its own.

 

[qboneus]

Awesome!
thanks for the pictures!
Looks great!
any more additions?

tal

 

[Urizen]

QED Passive

The little QED CD-PA Gold Passive with Alps Blue Velvet 10K potentiometer. I currently use it as a subwoofer volume control with a system that doesn't have a variable output.

 

[cableguy]

I am currently using this one...

http://www.audiokarma.org/forums/showthread.php?t=215129


Great preamp...I love it.

 

[qboneus]

thanks for the pictures.
tal

 

[Redboy]

No, it was a good link to a thread in the Subscriber section. It was a thread that I need to take down anyway, so I've reattached the pics here:

 

[qboneus]

Excellent!
don't know how I missed your response; thanks for the import.
tal

 

[klama2006]

My $8.01 cigar box pre (thread here).

Thats cool as hell.

 

[theophile]

This thread made me consider doing something which the designer/builder of my Lightspeed has been telling me to do since I first bought the thing.
Lose the Buffer stage.
I've had a change of component which follows the Lightspeed(the F-25 Accuphase active crossover),and the interconnects which I am using are also different.
So I 'lost' the Buffer stage.....

The difference was 'night and day'. :yes:

I got a channel imbalance at first,so I swapped the interconnects which connect my Moon phono stage to the Lightspeed.

OH MY GOD ! ! !

The difference now was incredible.The sound with the Lightspeed/Buffer was very,very good.When I'd finally got everything sorted-out,it was freakin' unbelievable.

The designer of the Lightspeed(George Stantscheff)states that the advantage of the Lightspeed over other attenuators is that it doesn't have the contact element which a pot or a resistor ladder/stepped attenuator has.
The attenuating element(in this Stereo attenuator)is one Light Dependent Resistor per channel.The only contacts are the input and output jacks.

I've not used any other attenuator in order to prove/disprove George's assertion,however he has generously divulged his construction of the Lightspeed on 'diyaudio' forum.The thread is massive(70+ pages,and counting)however the guts of what has to be done are shown on the first few pages.The rest is discussion by those who have been seduced by the Lightspeed about fine details,adding remotes etc.
Check it out. :thmbsp:
I'm a fully fledged member of the Passive Attenuator User Group now.
Forever....... :yes: :thmbsp:

 

[Redboy]

Interesting stuff, theophile. Thanks for the heads up - I'll have to try building one of those sometime. :yes:

 

[theophile]

Interesting stuff, theophile. Thanks for the heads up - I'll have to try building one of those sometime. :yes:

The Lightspeed seems particularly suited to mating with Tube power amps,because they generally have very high input impedance.That suits the Lightspeed down to the ground.
George(I surmise)is a Tube-Man. :scratch2:

Keep us informed of your endeavour. :thmbsp:

 

[whell]

I used a McCormack TLC-1 for quite a while before selling it to a fellow AKer. Nice piece of gear, but now I use no preamp at all in the main system.

That fellow AK'er would be...me! It is still in daily use here and sounds great in my system. I wasn't sure how a passive pre would work out for me, but so far it has exceeded my expectations.

 

[qboneus]

That fellow AK'er would be...me! It is still in daily use here and sounds great in my system. I wasn't sure how a passive pre would work out for me, but so far it has exceeded my expectations.

:thmbsp::thmbsp: mirrors my experience!

tal

 

[qboneus]

:yes:Still running my line drive in my system and i couldn't be happier:thmbsp:

Bump for those that missed this thread last time

cheers,
tal

 

[Redboy]

Here's one I built recently.

 

[theophile]

:yes:Still running my line drive in my system and i couldn't be happier:thmbsp:

Bump for those that missed this thread last time

cheers,
tal

I will admit that I have 'jumped-ship'.
I decided to try out a number of preamps that I had put aside,after I had purchased the Kenwood L-1000M amps.Mostly because I was selling my Yamaha C2x(and the Yamaha B-2 I had)to my friend and fellow AKer 'Timofred',and wanted to be sure that the C2x was operational.I also decided to try-out the Transcendent Sound Grounded Grid preamp,which had always sounded awful in every system.
Well again it sounded awful but by the end of the LP side,I was getting hints of things that I had never heard resolved before,from an LP that I knew extremely well.I left the GG in the system and haven't put the 'Lightspeed' back in since. :scratch2:

My thoughts are that I had never previously used the Grounded Grid sufficiently to 'burn-in' the capacitors.

Of course,still having the Lightspeed at hand,I will eventually put it back into the system for another comparison. :yes:

 

[Redboy]

Hey theophile, I'm slowly accumulating parts for a Lightspeed build of my own, largely on your recommendation. Since I'm a fan of passive preamps, it seems like a natural fit and something I ought to try.

Will post up a thread when I get around to it.

 

[ejfud]

I use one on and off. When it matches well with the amp, it's wonderful, when it doesn't, it sucks the life out of the music.

Like everything in this hobby, synergy is key.

 

[theophile]

Hey theophile, I'm slowly accumulating parts for a Lightspeed build of my own, largely on your recommendation. Since I'm a fan of passive preamps, it seems like a natural fit and something I ought to try.

Will post up a thread when I get around to it.

Redboy,
I certainly won't disparage the Lightspeed.My opinion of it remains very favourable.The concept behind it seems to be the most straightforward of all passive designs.

I would be extremely interested in reading your thoughts about it. :yes:

If I haven't caught your eventual thread on it(for whatever reason),could I humbly beg a PM notification of your posting of the thread? :yes:

It's nice to hear what other people have to say about a scarce component.