Redboy
a few good watts
Build a tube amp, eh? :scratch2:Say though...now that you have a herd of those pre-amps...maybe it's time for a toob amp...?
Just sayin.'
Now there's a thought...
-
Feeling lucky? Check out the AK 24th Anniversary Giveaway thread and join in the fun!
Proof of concept: An $8.01 passive preamp... in a cigar box!
- Thread starter Redboy
- Start date
Now there's a thought...
heekma
Well-Known Member
Yeaaah buddy.
boosh!
I'm not "new" to the forum so to speak, skulked around a couple years ago, posted what (very) little I could and built a DIY tube amp--barely!
http://www.audiokarma.org/forums/showthread.php?t=263379
A few pics since my previous server/host bit the dust...
If you already have the toobz down, please don't think I was being condescending.
I just like the cut of yer jib my man, and would enjoy seeing some tube action if you haven't already.
Smell the solder. Burn a few fingertips. Feel the pride.
All the best,
John
boosh!
I'm not "new" to the forum so to speak, skulked around a couple years ago, posted what (very) little I could and built a DIY tube amp--barely!
http://www.audiokarma.org/forums/showthread.php?t=263379
A few pics since my previous server/host bit the dust...
If you already have the toobz down, please don't think I was being condescending.
I just like the cut of yer jib my man, and would enjoy seeing some tube action if you haven't already.
Smell the solder. Burn a few fingertips. Feel the pride.
All the best,
John
TerryO
Super Member
Except you end up running back and forth tweaking the living daylights out of the balance. I had a receiver with dual volume sliders. The tweaking never ended.
You could get a couple of small cogged pulleys that fit a 1/4 inch shaft and then gang them with a cogged belt once you're sure that they're synchronized. A hobby shop, or maybe the slot car guys, would know where to get them.
Best Regards,
TerryO
soundmotor
super modified
Nate and others who have built this preamp, I have a question. How does the gain on this preamp compare to the gainh on an active preamp - same, lower higher????
Do you see any benefits in acoustical quality on this preamp versus a "manufactured mass produced active pre"?
Just wondering?
Do you see any benefits in acoustical quality on this preamp versus a "manufactured mass produced active pre"?
Just wondering?
x_25
Big Vandies!! Mwahahah...
An active pre has an amplifier in it, therefore can have positive gain. A passive pre can only attenuator the signal. So if you plug your source right into the amp, that is the max volume attainable with a passive pre. :yes:
audiozaz
rtfm!? - tl;dr
As X 25 pointed out, passive means no power gain can be achieved. No voltage gain is achieved with this design either, for which you would need transformers and a whole new world of impedance problems would present itself.
As for quality, assuming the passive device to be perfectly matched in impedance to the upstream and downstream devices, it should be comparable to the better-designed actives out there and beat cheaper stuff, as no preamp is the best preamp. When you think about it, a preamp is there for two reasons: convenience (quick source switching) and to correct imperfections that should ideally not be there to star with (musical-content, gear and room related frequency response issues, balance...). In other words, perfect recordings played on perfect equipment in a perfect room, heard by perfect ears should be the standard, but who can claim to have even one of those? So I guess the better your source material, gear and room are, the better you can enjoy a passive pre.
az
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lorne
Sonic Lizard
X 25 and audiozaz are right on the mark. You're only attenuating whatever the line output is from the sources that are in your system. If you want, you can incorporate your passive attenuator with a switch box so that you can attenuate and switch sources from the same box. There are some simple plans around to show you exactly how to do this — and it is cheap enough to do. In my case, I built a separate box. The only issue I ran into was making cassette tape recordings. I had some sort incompatibility.
Currently, I am back to using an active pre-amp — a tube Melos GK 1+1. It uses an expensive volume pot and balance is achieved by switching through resistors. I've had to completely rebuild and modify the massive, outboard power supply. Back in the days, this active pre was very expensive and yet, I have to say, over the years the only thing that has come up to it in my opinion are the passive attenuators I've built. The Melos does have an advantage — a very configurable head-amp section that I need to play LP's, and it is completely compatible with my upper end cassette deck. One option was to build a separate head-amp unit for the TT, but I just happened to have the Melos stacked up in the closet!
If I were only using my Yamaha CDX and linear-power-supplied Monica II DAC, I'd be back using one of my passive attenuators. Even my DC powered Monica I had enough output to easily feed either two Kenwood/Trio L-05M mono amps, or the power section of my rebuilt Pioneer SA-8900.
The only issue to watch out for is impedance compatibility. This has been discussed and worked out in the threads so you can more or less predict your needs. In many cases it just works out. And if you build your first one with the cheapest of parts, you can afford to play with things until you get it right
Currently, I am back to using an active pre-amp — a tube Melos GK 1+1. It uses an expensive volume pot and balance is achieved by switching through resistors. I've had to completely rebuild and modify the massive, outboard power supply. Back in the days, this active pre was very expensive and yet, I have to say, over the years the only thing that has come up to it in my opinion are the passive attenuators I've built. The Melos does have an advantage — a very configurable head-amp section that I need to play LP's, and it is completely compatible with my upper end cassette deck. One option was to build a separate head-amp unit for the TT, but I just happened to have the Melos stacked up in the closet!
If I were only using my Yamaha CDX and linear-power-supplied Monica II DAC, I'd be back using one of my passive attenuators. Even my DC powered Monica I had enough output to easily feed either two Kenwood/Trio L-05M mono amps, or the power section of my rebuilt Pioneer SA-8900.
The only issue to watch out for is impedance compatibility. This has been discussed and worked out in the threads so you can more or less predict your needs. In many cases it just works out. And if you build your first one with the cheapest of parts, you can afford to play with things until you get it right
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kmulder
Member
I'm sure this is a dumb question.....but what IS a pre-amp for? Simply to boost input, allowing for even MORE volume out of the speakers?
I have a Sansui 7070 and never turn the volume up past half for fear of shaking my trailer home off its foundation.
There must be some other reason other than to get louder music
I have a Sansui 7070 and never turn the volume up past half for fear of shaking my trailer home off its foundation.
There must be some other reason other than to get louder music
lorne
Sonic Lizard
This is not a dumb question at all. And, while attempting to answer you, I fear that I may have forgotten some vital things about the subject — or I may be distorting some points. Still, I don't think that it will be off-topic to comment on your question. Perhaps I can attempt to explain why Redboy and others have been inspired to build such very simple devices.
In my understanding, an earlier era of audio produced line-sources that were not in and of themselves producing much line-stage power. Moreover, there was not much agreement among manufacturers, or even consistency among the various line-stage devices.
The most obvious need for a pre-amp was in regards to LP playback. All analogue was recorded and then re-recorded on archival, playback vinyl with some of the audio bandwidth suppressed while other parts were left in full bloom. This was done in order to assist in reducing unwanted noise and distortion. Playback needed a circuit that played back the LP according to the realism that was being being attempted. The process could be described by representing geometric curves. These were understood and standardised. And, all head amps or EQ circuits in the common pre-amp were designed to rectify the archive back into the realistic representation. Obviously, some EQ circuits were better than others. And acccordingly some were more expensive than others. And so, pre-amps achieved reputations based largely on what the EQ sections could achieve. They were all attempting to match a standard established by the recording industry.
Even today, some LP enthusiasts are using sections of older pre-amps to play back LP's. And of course, there is an entire subsection of an industry that supplies TT playback EQ amps — everything from the very inexpensive to the extravagant, boutique items — and, as always, plans and schematics for the DIY person.
Cassette tape players were brilliant in a way because they supplied their own, on-board EQ sections. The media and the hardware were integrated and functional in one machine. I think that this is a milestone that has been missed in the history of home recording!
Anyway, as time and technology went on, there was still the need to integrate systems so that various devices could be coupled without gross impedance mismatches. After all, there was a moment in history when solid state and tube separates were often shot gunned into some form of marriage. And the average consumer was neither aware of, nor perhaps very interested in the issue of whether they suited each other. A pre-amp stood an excellent chance of surviving most marriages — for those who were using separates — that is pre-amps and power amplifiers. The consumer could hook up almost power amp that was produced on the market to a decent pre-amp and produce a reasonable, effective sound. In addition, one could alter the tone to suit the room — as well as reduce the nastiness of certain speakers, or enhance the deficiencies in others. The purist even back then was often suspect of these features, but it atracted a market.
Any look inside a 1970's pre-amp or integrated amp will be a dramatic illustration. The so-called tone board is usually a large piece of real-estate. And many (not all) TOTL pre-amps of a certain era have a vast number of pots and switches devoted to this end. It was marketing — the more do-dads and thingy-puffers the better. But that was the age. Even my venerable Tannoy Gold Monitor speakers came with tonal controls for gain and tone. When I rewired them, I set them for flat response thereby bypassing a whole pile of passive stuff like switches, metres of wire and various passive components on the X-over circuit.
Now enters a new age. You could now choose a speaker that was either a garbage-end dud, or if you knew enough about audio, one that was perhaps more likely to be optimally the best solution in your listening room. Also, CD's and DVD's blah blah were being recorded (compression aside) more or less according to a common standard. The audio bandwidth was being pushed out whatever sort of port, either as a complete set of sine waves that were ready to be amplified and transformed into sound waves by the speakers — or as data-bits that a DAC unit rendered to the same end. Some Japanese integrated amps even included their own, on-board DAC units!
Now, with this simplified world, all we have to do is attenuate the signal coming out of the source — either the CD/DVD blah blah player — or the end source DAC ... if you are using separate boxes — reading and conversion.
There are some remaining questions: what about tone? Well, all the stuff that controls tone requires devices that in many cases degrade the product. That is to say, each electronic device adds its own influence. So, consider the possibility of cutting out all of the middle stages in the pre-amp, and submit the line source to simple attenuation. Problems can remain — impedance matching being the main concern. But, if the enthusiast complies to some guidelines, this can be adjusted and optimised — with greater or lesser effort. For the casual user, the integrated one-box, or the pre-amp/power amp combination could be the easier solution.
So, in conclusion, many enthusiastic users will be trying to match speakers and their amplification to suit the space they are listening in. And I submit that today's industry is much more developed, and has more choices for which to do this.
But that is not exactly the answer we are seeking is it? Question: do we need a pre-amp? For the users of separate boxes, this still isn’t any sort of no-brainer question? Some of us still need to switch sources. Some of us are just not comfortable with the possibility of impedance mismatches. And some of us may want a buffer stage to kill the nastiness of some Redbook recordings — music we love but in a rendition of sound that cuts up our sense of hearing. And there is a niche industry that caters to this end.
Line stage output is no longer an issue. All line stage units are within a range that can be attenuated and amplified to loud levels using the simplest of attenuators — the simplest of pots! Well, some people have complained of low levels, but I've not experienced this problem. With huge rooms and so on ... maybe ... in some cases.
Referring to my previous post: personally speaking, I do miss some of the rawness of the CD Redbook that comes across on my simple, passive attenuators. But, I do enjoy the buffer that is offered in the gain stage of my Melos tube pre-amp. It's a matter of ‘win some ... lose some’. On the Melos, I can switch, sources, play TT and have no issues with say recording FM tuner to cassette — something that was not as successful with just the simple, passive devices I was building. YMMV!
The exact and descriptive, electrical/electronic explanation is much more complicated than I have written here. And, I am not competent to write it. Some of our members could write encyclopaedias on the subject. But, I hope that this adds something to the discussion.
You — who ever you are out there in audio land — may not need a pre-amp at all. If you are within the terms of impedance matching that is described and prescripted in related threads, you may be best served by a simple, passive attenuator. And, as it is said over and over — the best signal can be the one that passes most directly from the source to the transducer — the speaker.
Sometimes we need more. Sometimes less. Back in the day we needed more, or at least many of us thought we did — pots, defeat controls blah blah blah. Today, you may be in a position to use a LOT less. In the end, it is may be a matter concerning what is often reffered to today as synergy! There should be little or no magic in it. But science cannot predict it all either.
Many of us have been astonished at what we can do with some very simple, passive circuits. Simple to build, but not so altogether simple to understand. These basic circuits get right to the guts of Ohm's Law and the function of the most fundamental, everyday, discrete electronic devices. Not all of us — including me — find the fathoming of this world as easy as say ... uh ... parsing a sentence, or cooking up a curry rue.
But, no matter what ... you cannot lose by building one — for like ... $10?
In my understanding, an earlier era of audio produced line-sources that were not in and of themselves producing much line-stage power. Moreover, there was not much agreement among manufacturers, or even consistency among the various line-stage devices.
The most obvious need for a pre-amp was in regards to LP playback. All analogue was recorded and then re-recorded on archival, playback vinyl with some of the audio bandwidth suppressed while other parts were left in full bloom. This was done in order to assist in reducing unwanted noise and distortion. Playback needed a circuit that played back the LP according to the realism that was being being attempted. The process could be described by representing geometric curves. These were understood and standardised. And, all head amps or EQ circuits in the common pre-amp were designed to rectify the archive back into the realistic representation. Obviously, some EQ circuits were better than others. And acccordingly some were more expensive than others. And so, pre-amps achieved reputations based largely on what the EQ sections could achieve. They were all attempting to match a standard established by the recording industry.
Even today, some LP enthusiasts are using sections of older pre-amps to play back LP's. And of course, there is an entire subsection of an industry that supplies TT playback EQ amps — everything from the very inexpensive to the extravagant, boutique items — and, as always, plans and schematics for the DIY person.
Cassette tape players were brilliant in a way because they supplied their own, on-board EQ sections. The media and the hardware were integrated and functional in one machine. I think that this is a milestone that has been missed in the history of home recording!
Anyway, as time and technology went on, there was still the need to integrate systems so that various devices could be coupled without gross impedance mismatches. After all, there was a moment in history when solid state and tube separates were often shot gunned into some form of marriage. And the average consumer was neither aware of, nor perhaps very interested in the issue of whether they suited each other. A pre-amp stood an excellent chance of surviving most marriages — for those who were using separates — that is pre-amps and power amplifiers. The consumer could hook up almost power amp that was produced on the market to a decent pre-amp and produce a reasonable, effective sound. In addition, one could alter the tone to suit the room — as well as reduce the nastiness of certain speakers, or enhance the deficiencies in others. The purist even back then was often suspect of these features, but it atracted a market.
Any look inside a 1970's pre-amp or integrated amp will be a dramatic illustration. The so-called tone board is usually a large piece of real-estate. And many (not all) TOTL pre-amps of a certain era have a vast number of pots and switches devoted to this end. It was marketing — the more do-dads and thingy-puffers the better. But that was the age. Even my venerable Tannoy Gold Monitor speakers came with tonal controls for gain and tone. When I rewired them, I set them for flat response thereby bypassing a whole pile of passive stuff like switches, metres of wire and various passive components on the X-over circuit.
Now enters a new age. You could now choose a speaker that was either a garbage-end dud, or if you knew enough about audio, one that was perhaps more likely to be optimally the best solution in your listening room. Also, CD's and DVD's blah blah were being recorded (compression aside) more or less according to a common standard. The audio bandwidth was being pushed out whatever sort of port, either as a complete set of sine waves that were ready to be amplified and transformed into sound waves by the speakers — or as data-bits that a DAC unit rendered to the same end. Some Japanese integrated amps even included their own, on-board DAC units!
Now, with this simplified world, all we have to do is attenuate the signal coming out of the source — either the CD/DVD blah blah player — or the end source DAC ... if you are using separate boxes — reading and conversion.
There are some remaining questions: what about tone? Well, all the stuff that controls tone requires devices that in many cases degrade the product. That is to say, each electronic device adds its own influence. So, consider the possibility of cutting out all of the middle stages in the pre-amp, and submit the line source to simple attenuation. Problems can remain — impedance matching being the main concern. But, if the enthusiast complies to some guidelines, this can be adjusted and optimised — with greater or lesser effort. For the casual user, the integrated one-box, or the pre-amp/power amp combination could be the easier solution.
So, in conclusion, many enthusiastic users will be trying to match speakers and their amplification to suit the space they are listening in. And I submit that today's industry is much more developed, and has more choices for which to do this.
But that is not exactly the answer we are seeking is it? Question: do we need a pre-amp? For the users of separate boxes, this still isn’t any sort of no-brainer question? Some of us still need to switch sources. Some of us are just not comfortable with the possibility of impedance mismatches. And some of us may want a buffer stage to kill the nastiness of some Redbook recordings — music we love but in a rendition of sound that cuts up our sense of hearing. And there is a niche industry that caters to this end.
Line stage output is no longer an issue. All line stage units are within a range that can be attenuated and amplified to loud levels using the simplest of attenuators — the simplest of pots! Well, some people have complained of low levels, but I've not experienced this problem. With huge rooms and so on ... maybe ... in some cases.
Referring to my previous post: personally speaking, I do miss some of the rawness of the CD Redbook that comes across on my simple, passive attenuators. But, I do enjoy the buffer that is offered in the gain stage of my Melos tube pre-amp. It's a matter of ‘win some ... lose some’. On the Melos, I can switch, sources, play TT and have no issues with say recording FM tuner to cassette — something that was not as successful with just the simple, passive devices I was building. YMMV!
The exact and descriptive, electrical/electronic explanation is much more complicated than I have written here. And, I am not competent to write it. Some of our members could write encyclopaedias on the subject. But, I hope that this adds something to the discussion.
You — who ever you are out there in audio land — may not need a pre-amp at all. If you are within the terms of impedance matching that is described and prescripted in related threads, you may be best served by a simple, passive attenuator. And, as it is said over and over — the best signal can be the one that passes most directly from the source to the transducer — the speaker.
Sometimes we need more. Sometimes less. Back in the day we needed more, or at least many of us thought we did — pots, defeat controls blah blah blah. Today, you may be in a position to use a LOT less. In the end, it is may be a matter concerning what is often reffered to today as synergy! There should be little or no magic in it. But science cannot predict it all either.
Many of us have been astonished at what we can do with some very simple, passive circuits. Simple to build, but not so altogether simple to understand. These basic circuits get right to the guts of Ohm's Law and the function of the most fundamental, everyday, discrete electronic devices. Not all of us — including me — find the fathoming of this world as easy as say ... uh ... parsing a sentence, or cooking up a curry rue.
But, no matter what ... you cannot lose by building one — for like ... $10?
Has anyone tried a HH designed preamp with a yaqin or similar tube buffer in between it and the amp. With a higher voltage digital source, I wonder if the impedance correcting functionality of the buffer could make the amp an easy enough load to noticeably improve dynamics. It seems like with a 2 or 3v digital source there isn't really a need for added gain.
I'd love to here all your thoughts, because this seems like a pretty cool setup to me (but I'm pretty electrically challenged).
I'd love to here all your thoughts, because this seems like a pretty cool setup to me (but I'm pretty electrically challenged).
aussiedan
Ambition beyond ability
I'm sure this is a dumb question.....but what IS a pre-amp for? Simply to boost input, allowing for even MORE volume out of the speakers?
I have a Sansui 7070 and never turn the volume up past half for fear of shaking my trailer home off its foundation.
There must be some other reason other than to get louder music
I think both passive-pre and pre-amps are about source matching.
I made a HH design passive-pre not to make things louder, but quieter. A passive-pre cant make things louder, as it has no power of its own to do that.
I use a tube amp that sounds (to me) fantastic on LP's, but its also the quietest of my sources. If I switch to CD with the volume set the same, it damn near scares me out of the room. In between the TT and the CD (volume wise), is the tuner and cassette deck.
The HH design passive pre lets me "restrict" the other sources to match the TT level. A good solution for my gear and cheap/easy to make (not so easy for me to understand, I just accept that it works). Outright volume is not what I'm chasing, just good sound.
I guess, if you wanted, you could go the other way, use a powered pre-amp and boost the lower level signals to match the loudest.
I think I have the problem as I like vintage gear. As lorne said, some have different line levels. Modern CD's (discs, not necassarily players) seem louder than those of the '90's, and they seem louder than my turntable stage in the tube amp. Thats my reason, I sure there are many more.
hope this helps,
Danny
aussiedan
Ambition beyond ability
Thanks Redboy for enlightening me (putting it here on AK) and thanks to Harry for designing it.
For all those that are already modifying the design without making one, why not build one first? It does not take much. After that, add some more stuff to it and tell us if it improves, or detracts from the design. My thinking is, the more people making and playing with this design, the more info for all.
From what I can tell, costs range from about $4 for the cheapest components, to about $25 for TOTL stuff to put one together. If I said I bought a new stylus for my TT for $25, poeple would laugh at me.
It takes about as much time to make one as many people spend on AK in a day. I may be dumb, ignorant and stupid, but I made one.
Redboy, you have made a few, can you tell the difference in quality v's cheap components?
For all those that are already modifying the design without making one, why not build one first? It does not take much. After that, add some more stuff to it and tell us if it improves, or detracts from the design. My thinking is, the more people making and playing with this design, the more info for all.
From what I can tell, costs range from about $4 for the cheapest components, to about $25 for TOTL stuff to put one together. If I said I bought a new stylus for my TT for $25, poeple would laugh at me.
It takes about as much time to make one as many people spend on AK in a day. I may be dumb, ignorant and stupid, but I made one.
Redboy, you have made a few, can you tell the difference in quality v's cheap components?
audiozaz
rtfm!? - tl;dr
A TOTL unit could easily lead you far into the 3-digits if that's what floats your boat! :thmbsp:
az
Redboy
a few good watts
Yep. I've built several variants of this thing and they all sound good, but you do get better performance with better components, to a point. Like all other things audio, the sky's the limit and the law of diminishing returns kicks in somewhere, but because there are so few component parts to this design, the "high end" is more attainable.
You should sink most of your money into a quality potentiometer if you want to spend more. Better pots track better between channels and have smoother action. Play around with a few and you'll find that they each have a signature sound, too.
At some point though, you've got to quit obsessing about the nuances of bit parts and just settle back and listen!
Redboy
a few good watts
I've got the parts here to build one of those, but haven't gotten around to it.