Passive Preamp

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Here is a link to a photo of a product that some may find interesting. This is a transformer-based attenuator and controller unit that was volume-produced by Luxman around 1993.

Sadly the photos at the link below show the exterior only - no sexy internal shots.

http://page2.auctions.yahoo.co.jp/jp/auction/b35161692

This Luxman was produced in reasonable quantities, so units do appear on the Yahoo Japan auction site every now and then.

best to all, jonathan carr
 
HH's shunt attenuator: my $0.02

Ah well I can say this:

One can REALLY hear the difference between using an el cheapo stereo pot in normal mode and this design. Although the cheap resistors I used for this one give it a metallic sound (and grainy aswell). That's for gainclone 1.

With my second gainclone, using an Alps 50k stereo pot, the difference was less. However, although I didn't use very good resistors (yageo) it did sound better. Mids and highs are clearer and soundstage is way better than with the alps pot in normal mode.

I think I'll build me a separate preamp for my -almost finished- all BG & riken gainclone numberrrrrr.... 3
 
I built one using an Alps Blue Velvet and Vishay VTA54 series resistors. Now that sounds good 😀 A second unit that I built for a cousin used a cheap pot and Yago resistors. It sounded good, but not as good as mine. I think it's the Vishay resistors that did the trick.

RonS
 
Audiofanatic

I'll keep you posted, audiofanatic. I'm still waiting for the delivery of some BG's which were out of stock, still have to build a case & experiment with PSU diodes & voltage.

But this is not the right forum for that...

oja ik woon redelijk bij het centrum in de buurt, dichterswijk (croeselaan)

oops, was that another language? :goodbad:
 
Passive preamp

Hi!

I made the passive preamp with two 22k resistors in parallell for R and a 100k Pot to shunt to earth. I get enough volume very early and the pot hasn't even reached half of its travel range. As I have more than enough volume I could trade off some volume level for lower impedance. How do I could achieve this?

Thanks for any replies!
Hans M.
 
Hi all,
inspired by HH passive preamp, I made some mods to de design and I have inserted a 4:1 trafo before and a 1:1 trafo after the pot.

I'll put some pics as soon as I'll own a digital camera :xeye:

My impression is positive, maybe a little lack on the grave register, but it works very well on the image and stage.

Has anybody tried something similar?
Thank you!
bye
 
passive pre amp

Hi,
This is one of the first thread I read coming to the forum. Having studied the whole thread, and others on the subject, I experimented with a slight variation shown in Fig. 1 with cheap off- the-shelf parts (US$7 in all). It worked without any hiss or hum. The only thing is that it has too much gain too quickly. I'm using a log pot and the song becomes too loud at 11 o'clock (the starting point is 8 o'clock). Also, the sound is sowhat indifferent, less engaging. I'm now thinking of building the real thing - with vishays and alps, to a filter design adapted from Slone's book (figure 2). I'm building an Opti-mos so I think there might be some logic in doing this. To keep with the intention of HH's design, 5 is the maxium component count. Members' comments are valuable.
 

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After having used Alps pots for years in my passive preamps the stepped attenuator, Dact 10k log, sounds a bit dull at first, have to get used to it. Sounds like there is less coloration, good recordings are awsome to listen to. Its different, don't know yet what to think of it.
Poweramps are UCD400's. Always wonder why people say passive's have no dynamics? Comparing it to my NAD C162/C272 it has plenty dynamics!
 
I too have a UCD 400 with 10K passive pre,
have you change the input gain (R3) ?
I change my to 250 ohms and now I have tons of power.😀
 
Yes, I changed it to 180 ohms. It is quite sensitive now. But for a passive it is nice.
But the biggest change for me was the DACT attenuator, it sounds so different. I had a blue Alps 10k log stereo pot. which I used for a decade. Maybe I am too used to the sound of this pot. I still cannot believe the change in sound experience. Have to listen a lot to be able to judge this. It sounds a bit darker, tons of bass and highs but the middle section is a bit more dull sounding.
I mean the voice is ok but it is less agressive...difficult to give a sound experience in words.
 
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