Handmade Passive Preamplifier

Randy Myers said:

The webpage actually shows it with a volume control (volume etched on it), and an input selector (3 RCA inputs) beside that weird gain control thingy. Obviously the OP did not build it as it was intended to be built.

Honestly, in my view I would stick with either the Khozma Acoustic or Hattor Audio passive pre-amplifiers. In my view they are using a higher quality level of parts. I can tell you from personal experience the Hattor is amazing. Also, adding the Hattor optional Tube Active Stage is fantastic and it can be used either passive or active!

The Khozma offers a superior attenuator if someone is a DIY person and is building their own unit. He also offers input boards and remote control capacity if that is something you feel like adding to your home made project.

Here is how it is designed, with a selector to choice the input and a separate control for the gain thing:

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I just bought the attenuator and transformer from the manufacturer, this is reasonable to have design variations. What I hope is to share with all of you about its amazing functions, a passive preamp could do voltage amplifying up to 10X gain, together with different sound qualities, which I am very satisfied with it. It is expected that the manufacturer could have an even better design than mine. This is a passive preamp, saying a Tube in comparison I think it's meaningless as they are different kinds of amps, which in fact you've never tried this passive preamp before. Sound is heard by ears, not seen by eyeballs.

I've tried all your mentioned brand products, which couldn't do voltage amplifying. That's why I eventually sell them out. For the one actually does voltage amplifying you didn't call it a passive preamp, for yours that couldn't do so you called it a passive preamp. I think it's better to call it a "passive volume" or "passive selector".

You posted the manufacturer's product images here, are you actually doing advertising promotion for "designbymrk"?

Speedskater said:

Yep, the OP's schematic in post #1 is strange to say the least.

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It is not that strange because having gain options for passive preamp design such a method has been released for over 20-30 years, which was very popular in Japan, however at that time only 24 steps could do. That's why it made the volume control steps are not fine enough, which is sometimes too loud or too low. Currently what I'm using is 59 steps one that could solve all the problems I just mentioned.

Obviously I was not comparing the tube stage to this passive. Do you even read before posting your obvious defensive replies? I was commenting on one of the highest rated passive preamps in the world, the Hattor and I mentioned that he also offers an add on tube active stage (which when engaged would make the preamplifier no longer passive). You can then either use it in pure passive mode or tube active mode with the flip of a switch.

Also a friend of mine designed and builds probably the other most renowned passive preamp, the Wyred 4 Sound STP-SE Stage 2. Therefore I would say I have a bit of knowledge on passives. I have never heard of the product you are pushing, but always prefer that correct information is given and shown. Therefore photos of the real product.

Also you have stated several times how the 59 step attenuator is unique and so many more steps then other passives while I posted links to Arek's 64 step attenuator which in virtual any passive and DIY group discussion is regarded as the finest passive attenuator in the world.

Lastly, please stop posting your non-sensible and repetitive replies.

AudioLover525 said:

It is not that strange because having gain options for passive preamp design such a method has been released for over 20-30 years, which was very popular in Japan, however at that time only 24 steps could do. That's why it made the volume control steps are not fine enough, which is sometimes too loud or too low. Currently what I'm using is 59 steps one that could solve all the problems I just mentioned.

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Your schematic in post #1 does not show a stepped volume control system.

Randy Myers said:

Obviously I was not comparing the tube stage to this passive. Do you even read before posting your obvious defensive replies? I was commenting on one of the highest rated passive preamps in the world, the Hattor and I mentioned that he also offers an add on tube active stage (which when engaged would make the preamplifier no longer passive). You can then either use it in pure passive mode or tube active mode with the flip of a switch.

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You was commenting about one of the highest rated passive preamp in the world, but couldn't believe that you didn't even include those transformer type, which is an obviously in-comprehensive speech.

Randy Myers said:

Also a friend of mine designed and builds probably the other most renowned passive preamp, the Wyred 4 Sound STP-SE Stage 2. Therefore I would say I have a bit of knowledge on passives. I have never heard of the product you are pushing, but always prefer that correct information is given and shown. Therefore photos of the real product.

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It's none of your business that what your friend has designed even in the point of view of us, as an electronic practitioner, audio is actually such a low-tech product:yahoo1: Kind of hobby or toy.

Randy Myers said:

Also you have stated several times how the 59 step attenuator is unique and so many more steps then other passives while I posted links to Arek's 64 step attenuator which in virtual any passive and DIY group discussion is regarded as the finest passive attenuator in the world.

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OMG you've been wrong and wrong again:exciting: How many times I've told you that please DO NOT try to compare electronic switch attenuator that has no amplifying functions with my 59 steps MECHANICAL voltage amplifier? The brand Hattor you've mentioned for so many times in fact could reach up to 48 mechanical steps even without any amplifying functions.

Randy Myers said:

Lastly, please stop posting your non-sensible and repetitive replies.

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Before I stop, please stop posting your repetitive mistaken speech. I won't keep being repetitive if you're right.

When are you going to stop your now obviously blatant advertising for a product you have a vested interest in. It seems to be time for the Admins to put a stop to this charade as you have nothing to add to this forum but product promotion. Sell your goods on Ebay and move on.

May I introduce myself here, I am actually an electronic engineer who design medical equipment that applied in operation rooms, which I hope you guys will never use my service So after a long period of arguing, I found there is a situation that public does not really have a clear understanding on what a passive preamp is. And I try to explain here.

First of all, if a passive preamp could not perform an amplifying function, the sound level will not enough while using phono and open-wheel tube. The reason is very simple that some player output level is only around 0.2V, but somehow currently most of the CDs and network player output level have reached up to 2V. So those passive attenuator called themselves as passive preamp, is in fact fooling the public in modern society.

For the reason why using passive preamp rather than active one, is to seek for minimum level of noise and the purest sound in the world. To reach both of them, it is impossible to apply power lines or active components to it, once there are power lines or active component, noise ever exists no matter how strong the power filters you use. Sadly, to satisfy consumers' desires on using remote control, I would say this is kind of laziness, businessmen add remote controls plus electronic switches which entirely destroy the root theory of a passive preamp. Even they told that both power lines and attenuators circuits are absolutely isolated, it seems that they forgot the fact that both circuits are installed on the same PCB(Printed Circuit Board). The problem is that both circuits are interfering each other by air and the parasitic capacitance from PCB, therefore the only choice is to apply a mechanical volume control instead of an electronic one, not even the remote controls.

By the way, talking about the 59 steps mechanical switch, which is applying an Attenuator Curve 15A. While that 64 steps electronic attenuator recommended by that expert, is actually applying Curve B. I am confident to say that applying Curve 15A in 59 steps is undoubtedly superior to Curve B in 64 steps. For the reasons, you guys could search them online by yourselves otherwise people would think that I'm doing product promotion here.

One really good way of ingratiating yourself to a new group of people is to talk down to other members, basically stating that none of them know what they are talking about. Pretty much calling them ignorant.

You should realize that you are here posting on a forum whose members, for the most part, are very experienced, very accomplished, and extremely smart people. Many times I feel like I have lower intelligence than many of these brilliant folks and I have a 140 IQ.

You really should show a whole lot more humility when you first attempt to join a group of such amazing and accepting people who gladly share and assist fellow audio enthusiasts.

AudioLover525 said:

...For the reason why using passive preamp rather than active one, is to seek for minimum level of noise and the purest sound in the world. To reach both of them, it is impossible to apply power lines or active components to it, once there are power lines or active component, noise ever exists no matter how strong the power filters you use...

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this is the part of your argument many will have a problem with. You're making the presupposition that low noise circuits have to be passive by default which ins't true. indeed, sound reproduction would be impossible without active circuits and we're talking MANY stages of amplification cascaded from the mic pre amp back to the power amp driving the speaker. Transformers (or autoformers) do impart a sound of their own (some call it a 'dulling' effect) and are not linear devices relative to frequency response and 'gain' setting or switch position. Passives have their place but aren't a panacea for removing a veil or improving transparency and are limited to the overall gain requirements of a given system (source>loudspeakers).

puroagave said:

this is the part of your argument many will have a problem with. You're making the presupposition that low noise circuits have to be passive by default which ins't true. indeed, sound reproduction would be impossible without active circuits and we're talking MANY stages of amplification cascaded from the mic pre amp back to the power amp driving the speaker. Transformers (or autoformers) do impart a sound of their own (some call it a 'dulling' effect) and are not linear devices relative to frequency response and 'gain' setting or switch position. Passives have their place but aren't a panacea for removing a veil or improving transparency and are limited to the overall gain requirements of a given system (source>loudspeakers).

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I understand and this could be a problem when using transformers. In fact, according to designbymrk website, which states their transformers perform a frequency response ranging from 20-20kHz with +/-3dB. However what I measured is actually ranging from 20-20kHz with +/-0.5dB with a 47kohm loading at 10X gain option, which really impressed me and that's why I recommend it.

Randy Myers said:

One really good way of ingratiating yourself to a new group of people is to talk down to other members, basically stating that none of them know what they are talking about. Pretty much calling them ignorant.

You should realize that you are here posting on a forum whose members, for the most part, are very experienced, very accomplished, and extremely smart people. Many times I feel like I have lower intelligence than many of these brilliant folks and I have a 140 IQ.

You really should show a whole lot more humility when you first attempt to join a group of such amazing and accepting people who gladly share and assist fellow audio enthusiasts.

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The reason why we kept arguing is that it seems like we were discussing on different things. What I was trying to share is a passive preamp, but you might intended to share some active one/electronic switch control/even not a preamp(that couldn't do amplification), which is not quite applicable.

I know here is a place full of smart and talented people, even me who also have an amazing IQ that I wish not to share here.

Well Hattor is a world renowned passive preamplifier. It is even printed right on the face plate.



There are several ways of building passive preamps. The main criteria is to not use any buffering or any gain stage... basically two of the main sources of coloration of sound in a preamp. Weather electronics are used to move banks of resistors in line for attenuation, or digital displays, or remote controls for that matter, has nothing to do with being classified as a passive preamplifier.

And honestly, what you are describing can be argued would not be classified as a passive preamplifier; it actual does have a gain stage and as you have very clearly stated this gain stage does actually color the sound.

AudioLover525 said:

different gain options(1X, 3X, 5X and 10X) are with different sound qualities, like sweet and thick.

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This in most circles is exactly what dis-qualifies a pre-amplifier from being considered passive; therefore sir, in actuality it is you who could be argued as being mistaken and not understanding passive preamps. Just because the sound is manipulated without the use of electronics does not mean it qualifies as being passive, it still changes the sound (i.e. colors the sound) by use of a gain stage. And yes I can quote several sources verifying this is the commonly accepted definition of what a passive preamplifier is.

This discussion has become quite tiring and you have been asked several times to stop. I therefore ask nicely that you please stop, for one final time.

Sorry for posting something in context, what is the output impedance ? does it change with the voltage gain ?

It's unlikely that we will see good, impedance, frequency response or distortion test results.
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actually it would be a ton of work to do those tests. Change the source impedance or the load impedance or the volume tap or the effects tap or the level and the results change.

Devg said:

Sorry for posting something in context, what is the output impedance ? does it change with the voltage gain ?

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No problem. The output impedance is 10k ohm at minimum, according to the manufacturer's user manual. I'm not sure whether the output impedance will change with voltage gain, I think you might contact the manufacturer for more information.

False trade descriptions, false, misleading or incomplete information, false marks and misrepresentations of the goods provided in the course of business or the suppliers of such goods cause the violation of The Trade Descriptions Ordinance. Please make sure the product is coherent with its actual function as an amplifier. As the OP I don't think I need to stop, instead, somebody could choose not to reply. I've tried my very best to persuade you all with the definitions of passive preamplifiers as an electronic engineer. It's perfectly fine that some of you disagree with me.

Yes and I think the manufacturer has done a lot of work on that. That's why I could have such a great listening experience.

I was about to post a full explanation of passive preamplifiers from Tortuga Audio, Hattor Audio, Creek Audio and others. But then I figure why bother.

These companies have great reputations and of course they have no reason to lie (which you accused them of). For example, Hattor. He does not advertise, does not go to shows, his units are rarely reviewed. They are hand built in Poland by a one man operation, and they are very well respected from word of mouth alone. Yet Hattor and Tortuga are two of the most renowned passive preamplifiers in the world. I guess you must know more though.

You simply keep pushing a product that no one has ever heard of and keep stating that the big boys in the passive preamp field are lying about being passive even. Even funnier, from what I can tell I believe that the product that you have been pushing for 30+ posts is not even sold in the US, i.e there are no dealers or distributors in the US and the e-bay link is, well difficult to trust to put it mildly. Estimated transportation time, 22-39 working days.... after taking 15 working days to build... so we are taking 11-12 weeks. The other companies ship within a couple days and it took exactly 2 days to ship from Poland. Yea definitely not a lot of confident in buying this from China.



All of the companies I mentioned are very established and sell from their website along with having US distributors. They all correspond with their customers through e-mail or through their US distributors, and have a reputation for providing great customer service. Arek from Hattor is amazing and stands behind his products like it is gold.

Randy Myers said:

You simply keep pushing a product that no one has ever heard of and keep stating that the big boys in the passive preamp field are lying about being passive even. Even funnier, from what I can tell I believe that the product that you have been pushing for 30+ posts is not even sold in the US, i.e there are no dealers or distributors in the US and the e-bay link is, well difficult to trust to put it mildly. Estimated transportation time, 22-39 working days.... after taking 15 working days to build... so we are taking 11-12 weeks. The other companies ship within a couple days and it took exactly 2 days to ship from Poland. Yea definitely not a lot of confident in buying this from China.

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Let me tell you, or educate you, if we say we are from Hong Kong then we are from Hong Kong. NOT CHINA. At least not yet until this moment. Please DO NOT mix them up, I suggest you to read more news so that you will know Hong Kong is differ from China The manufacturer stated this product is made in Hong Kong, then it is definitely just from Hong Kong. I also visited the manufacturer's factory, which proves that the product is manufactured in Hong Kong. Otherwise, it is violating the Trade Descriptions Ordinance if it is from China. The manufacturer has the right to accuse you of calumny. Other than audio knowledge, please also be well educated for international issues. You've hit the bottom line to Hong Kong people.

The products you keep pushing do not have amplifying function, which can be proven by testing. The passive preamplifiers are manufactured in Hong Kong. I've taken photos from the factory, which is a strong evidence to show it is from Hong Kong. However, you stated it is from China. This shows how rude you are, that's why I can't respect you.