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I was looking into building one. So I was wondering if anyone here uses or has tried the autoformer type of passive preamp.
These are available in parts for at Sledge audio and Bent audio.
Any advantages. Or is this just going to end up an expensive project that keeps me busy and end up in a box unused?
charles
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I had the Sonic Euphoria PLC for many years and loved it. The only thing that could topple it (tried preamps up to 8K) was an LDR, which I now own.
Oz
Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill
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Beatnik's stuff http://web.me.com/jnr1/Site/Beatniks_Pictures.html
I have been using Slagle Autoformers in my passive preamp for several years. Hard to go back. If I upgrade it will be to an EMIA version with remote.
High sensitivity, wide dynamic range, low distortion, and smooth frequency response. Pwk
http://www.itishifi.com
This thread is perfectly timed I just noticed Dave Slagle is giving away some autoformer modules on their blog. Check it out and sign up if you think you are into that sort of thing 8-)
High sensitivity, wide dynamic range, low distortion, and smooth frequency response. Pwk
http://www.itishifi.com
Sonic Euphoria (passive autoformer) is the best of several preamps (BAT VK30, Jeff Rowland, Bryston) I've used. It is simple, quiet, uses no power, cannot break or go out of spec, has loads of input/output flexibility, sounds wonderful. It does not lack dynamics (with excellent recordings they are sometimes frightening) when playing CD/SACD. I passively run three complete systems from it with very long IC's, and the SQ is fine.
You'll need a preamp for phono.
Peace,
Tom E
I got rid of my Sonic Euphoria one years ago.
Advantage: very lower power usage.
Disadvantage: lost some dynamics.
I thought the same when I reviewed one many years ago for Positive Feedbback. I even stuck it between another preamp and the amp and found that the loss was real and it was not completely free of coloration.
Sold my Sonic Euphoria to a friend who loves it. I also thought it was a great preamp. No loss of dynamics and was not limited to cable choices. Autoformer passives are nice and they can even have some gain.
Alan
You'll be happy with it. No remote volume on an auto former whereas a resistor ladder or light speed does.For a passive to work well one needs ballsy high output voltage (2.5V+) sources with low output impedance (200 ohms or less is best) and a sensitive high input impedance amp. One that will give full output with a volt with 100K input impedance would be great.
So tell us your numbers. Phono will be harder to pull off than other sources. You need to start at cart output voltage, phono stage gain then output voltage and impedance. SS phono stages almost always have lower output impedance.
ET
Edits: 02/02/16
With an autoformer, none of the stipulations you mention, other than phono restrictions, are true.
Do you understand the difference between passive resistive and autoformer?
Peace,
Tom E
Yes and I know you can get often 6db gain or so from an autoformer. There are still scenarios based the numbers, particularly amp input impedance and sensitivity that are not suited for ANY passive linestage. Period. I'll throw the "do you understand" back at you.
ET
Any modern line level source with an output imp below 1k ohms should be capable of driving an autoformer, and any amplifier with input imp above 10k connected to it can realize its full potential, even with longish IC's. Devices outside those specifications may induce matching difficulties with any preamp. I imagine there are fussy sources and amplifiers that are unsuited for use with anything but the most benign, accommodating preamps.
Producing excessive gain and then throwing it away never made sense to me. That is exactly what most powered preamps do, at the expense of power consumption and additional distortion and noise. Unless a system has a low level source such as phono, there isn't much need for an active preamp.
Peace,
Tom E
You only forgot to address sensitivity. Although rare I've seen some amps almost always tube amps that need two and three volts or more for full output. I'm with you on line level sources these days. I still have concerns regarding phono as one must calculate everything from cart output on up the chain.I don't think we see things much differently I think I'm just more cautious. This comes I guess from being a dealer and seeing things creep up when the customer forgot to tell you something pertinent to the install/system.
ET
Edits: 02/05/16 02/05/16
Most of what you say is true with resivetive passive. Not so much with autoformer passives. Sonic Euphoria had a version with remote.
Alan
As I said above there are still certain scenarios where even the little bit of auto former gain isn't enough. Rarer for sure but they exist. Thanks for your post.
ET
I use a Sonic Euphoria as well and found that I have not heard many preamps (especially for the price) that forms as much of a 3D image coupled with FR neutrality as this one does.
As louie3 noted you do have to be careful with amp sensitivity as well as cable/source drive and capacitance.
Good luck with your project!
Happy Listening!
DeeCee
I have a Sonic Euphoria autoformer preamp I use with high input sensitivity
amps in my system from time to time. It is far and away the best "passive" preamp I have had, including two transformer preamps.
But no built in gain just does not work for all systems.
If I could make up my mind which amp I like better it would help.
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