Handmade Passive Preamplifier

AudioLover525

AudioLover525

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Joined
Nov 11, 2020
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Location
Hong Kong
My very first handmade passive preamp!

Lots of fun to make it successfully amplifying and tuning sound quality in thick bass or accurate positioning :D Hope to share with all of you.
 

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In fact, hope to know whether there are anymore similar types of passive preamp. Wanna try and improve my work.

Does anyone know?:skeptical::skeptical:
 
In fact, hope to know whether there are anymore similar types of passive preamp. Wanna try and improve my work. Does anyone know?
Click to expand...

There are quite a few transformer-based attenuators around, I have a Stevens & Billington one. Mine has switchable inputs using relays -- many of which no longer work, by the way :|
Very clear, airy sound, but I get more dynamic impact with the regular active pre.
Beautifully done, by the way!
 
Awesome job...

Arek Kallas offers an attenuator that is rated as one of the best and I know they are highly rated in the DIY community. Khozma Acoustic is his company where these are sold.

High Quality Audio & Industrial Attenuators and Passive Preamplifiers

I do not believe he offers full kits however.

His higher level company is Hattor Audio. In my personal view they offer one of the finest passive pre-amplifiers on the market.

Hattor Audio

I really like my Hattor pre-amp and I have the addon Tube Active Stage on order, which will make my Hattor a true three box pre-amp!
 
Since you guys are talking about the attenuators, I might share more about the attenuator and transformer I used in this DIY passive preamp.

The attenuator and transformer are handcrafted and bought from "design by mr.k", a local brand from my hometown Hong Kong.

I've tried other attenuators and transformers from other brand before, sadly they didn't work/sound good. But for "design by mr.k", I could find 59 steps mechanical volume control and even 59 steps autotransformer - I think it might be probably the largest number of steps I've ever seen before. This transformer controls the volume step-up amplifying, that's why this passive preamp doesn't require any power sources.

This brand also offers the whole set of passive preamp product on eBay. Not sure whether you guys would be interested, but just hope to share my experience and some reviews:cool:

Very sorry that up to this moment I could not post up any links yet(since I'm new and don't have enough post counts). Once I could, I will post up the company and eBay link to you all.
 
AudioLover525 said:
I've tried other attenuators and transformers from other brand before, sadly they didn't work/sound good. But for "design by mr.k", I could find 59 steps mechanical volume control and even 59 steps autotransformer - I think it might be probably the largest number of steps I've ever seen before. This transformer controls the volume step-up amplifying, that's why this passive preamp doesn't require any power sources.
Click to expand...

The Khozma are 64 step and about as good as you get. In the Hattor model "The Big" he uses two of them in dual mono. Each channel has its own volume control. With the AMRG Trans resistors version these are the state of the industry in passive attenuators.
 
Randy Myers said:
The Khozma are 64 step and about as good as you get. In the Hattor model "The Big" he uses two of them in dual mono. Each channel has its own volume control. With the AMRG Trans resistors version these are the state of the industry in passive attenuators.
Click to expand...

I know that Khozma with 64 steps, but it is an electronic switch. In the Design by Mr.K model, the volume switch is controlled mechanically which makes the tuning experience super concrete and good.
 
That is cool. Of course you should use whichever is best for your purposes.

Arek's attenuators are highly regarded as about the purest sounding available. I can tell you from comparing several preamplifiers, the Hattor is the best sounding I have ever heard, and is ranked with the best of the best passive preamplifiers anywhere in the world.

One huge difference however is that Arek offers an optional top quality Active Gain Stage. Mine should be arriving some time this week. It can be used as pure passive or with a selectable level of gain, and some added tube goodness! The full three box preamplifier supposable can hold its own against many of the very highest preamps!
 
Gregm said:
There are quite a few transformer-based attenuators around, I have a Stevens & Billington one. Mine has switchable inputs using relays -- many of which no longer work, by the way :|
Very clear, airy sound, but I get more dynamic impact with the regular active pre.
Beautifully done, by the way!
Click to expand...

In what ways they didn't work? Although somehow switchable inputs using relays are differ from my mechanical control switch.
 
Randy Myers said:
That is cool. Of course you should use whichever is best for your purposes.

Arek's attenuators are highly regarded as about the purest sounding available. I can tell you from comparing several preamplifiers, the Hattor is the best sounding I have ever heard, and is ranked with the best of the best passive preamplifiers anywhere in the world.

One huge difference however is that Arek offers an optional top quality Active Gain Stage. Mine should be arriving some time this week. It can be used as pure passive or with a selectable level of gain, and some added tube goodness! The full three box preamplifier supposable can hold its own against many of the very highest preamps!
Click to expand...

So how do they sound? For mine, different gain options(1X, 3X, 5X and 10X) are with different sound qualities, like sweet and thick. I'm curious about whether Arek offers this kind of variety of selectable gain choices and sound effects.
 
The base unit is a pure passive preamplifier. He offers a few different levels of resistors to choose from (with added cost of course). I originally purchased the base vishay version and it was very good. I then stepped up to the AMRG Trans version, his finest. It was considerably more open, more lush sounding. More air around the instruments, simply inviting and musical sounding.

The Tube Active Stage unit has not arrived yet. Therefore I can not answer that yet. I know the unit has a switch between pure passive mode which should be nice for lower listening, late night sessions, etc. When switching in the active mode there is another switch for how much gain. Arek states that with the active stage the sound is more relaxed, more dynamic with deeper bass. Because I am using harder to drive speakers, 4 ohm and 86 dB efficiency, and I am also preferring my amplifier that is very sweet sounding and musical but lower power, this extra dynamics should be useful.
 
Very nice work! I bought a 64 step volume control years ago with the intent of building something similar. I got lazy and never attempted it. My first passive pre was a Mod Squad Line Drive, it replaced a Carver preamp that had a power supply about the size of your thumb. That Line Drive blew me away and played many years of pretty music for me. Congrats.
 
stereogeek said:
Very nice work! I bought a 64 step volume control years ago with the intent of building something similar. I got lazy and never attempted it. My first passive pre was a Mod Squad Line Drive, it replaced a Carver preamp that had a power supply about the size of your thumb. That Line Drive blew me away and played many years of pretty music for me. Congrats.
Click to expand...

Thank you so much! I think the 64 steps one you bought should be electronic switches with relays, but here we use mechanical switch for concrete volume control experience which is great for HiFi lovers. In fact, you may start trying to build your second passive preamp without any power supply. The attenuator and transformer I bought is from DesignbyMr.K, which also offers the whole kit of passive premaplifier from eBay, has no any power sources applied in the design. As there is no any active components, power lines or supply nor wall plugs needed, no noise and distortion added to the device even up to 10X gain option. If you're looking for a no power passive preamp option, I would recommend DesignbyMr.K to you.
 
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