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No.4

Pre amp or no pre amp for tube setup

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I am considering adding a tube pre amp to my system, but I’m not sure if it will have any benefit. As always I am trying to squeeze any improvement out of my system. My system consists of the following. Emotiva erc3 CD player followed by a khozmo MKII attenuator feeding a diytube based KT88 clementine. My speakers are La Scala clones with the kappa 15c woofers, alk ES500/5800  networks, b&c dcm50 and de120, and Eliptracs. In my room I usually have the volume set around the halfway mark. I don’t necessarily feel like the amp can’t keep up, but I wonder if there is more.

 

I have been lightly Browsing some pre amp designs over the last year but nothing really jumped out at me. My daughters have been wanting to work on an electronics project with me as well, so I started looking again. I want something simple for them to help me with, but also something worthy of the main system. I found the bottle head quickie which is simple and battery powered but appears to have some drawbacks. Then we found the aikido 12vac which seems perfect. Low voltage, a decent amount of gain, easy to find in production tubes and a decent price. I actually have a nice enclosure that this would be perfect for this amp that I built a few years ago for a light speed that I never finished. It can acomidate the Wallwart power supply and the Toroid. I figure we can start with the Wallwart then I will change over the power supplement to the Toroid later. Any ways......

 

I am looking for some guidance from some of the tube gurus on his forum. First, is this addition going to yield any better performance from this system? Will this addition of another stage enhance the detail, bass, midrange etc? Is this a question that can be answered, or is this a you will have to try it to find out situation?

 

I should note that I will be using a khozmo mkII in this unit as well.

 

Let me know your thoughts, thanks.

 

 

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I have read some descriptions of slight noise floor issues with the Aikido design but I haven't owned one myself but I did shop them very intensely before falling into a NBS.

 

I think you can pick up some coloration with a powered pre... and you'll be able to roll tubes to tailor your listening experience. Both could be positives... as opposed to a totally transparent passive. Notice I didn't say veiled.

 

What version of the khozmo is yours? 48 step attenuation or 64? Any resistors or upgrade?

If you decide to part with the Khozmo, I might have seen me interest... LMK.

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Guest wdecho

If you have enough gain I do not believe adding a pre will benefit your system. Less is always better in my opinion. Especially when it comes to a tube pre. I do use a Firstwatt B1 I built more for convenience, being able to have multiple inputs, than adding anything in the way of improving the sound. It is a buffer with no gain but it also allows me to use my sub. I use it with my tube amplifiers and also my SS mainly because it is about as neutral as it gets without adding or deteriorating the sound in any way. I have a number of excellent preamplifiers as well both tube and SS. I only use a preamplifier occasionally with my SS amps and rarely use my tube preamplifiers mainly just for adding some sound effect. This is a quality designed full kit with outstanding specs. I built and have one and it is my favorite tube preamplifier.  http://www.oddwattaudio.com/owforewatt.html

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I too have and sometimes use a First Watt B1, earlier today matter of fact. In the right system a passive, or buffered passive in this case, a no gain can work but I've found more often than not an active pre really gives the drive many rigs need. For instance I do not feel the B1 drives the FW F3 well at all. It didn't do a bad job with the XA25 but still didn't produce the ultimate bass or drive of the active. I once thought tubes amps were the answer but like echo feel they can introduce added noise to the signal. A tube pre really has to be a good match within a system. Even an overall good tube preamp with noisy tubes is a no-go for me. I have rid myself of more than one tube preamp because of noisy tubes and not willing to search out the right tube, tube rolling, for the application. Maybe I'm just lazy, cheap or both?! Opinions differ but for the most part I have found a good active provides me the cleanest, noise free signal fed into horns. 

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Guest wdecho

My B1 buffer, preamplifier, is the latest addition series 2 which institutes a PP design. I have built the old design twice and did not like it very much. When using a quality SS preamplifier I am like you in that I, at times, feel like it contributes more oomp to the music but then it may be that with more gain and less turning of the volume control was all it was. Last week I played my F3 with my B1 buffer and enjoyed the combination being too lazy to replace the B1 with a gain pre. The main thing is to use what you like best. Maybe the OP will like the combination of tube pre with tube amplifier. But if one of my tube amplifiers has enough gain I do not want to add a tube pre into the mix. I would only use a tube pre with a tube amplifier when the power tube amplifier does not have enough gain by itself. I had one tube amplifier in the past that required a pre but have since tore it down and recycled the parts. 

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At this moment I'm listening to LaScalas' through the XA and Wyred STP SE preamp, a passive/active design. At low levels for LS it runs in passive but has much more drive than a traditional or even a buffered passive. Has as much if not more  capacitance than most power amps and uses a resistor relay volume control. This combination is quite sublime yet has the drive and full top to bottom balance at low levels. A great combo for LS. 

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Not a definitive yes or no from all who responded. Like schu said I do worry about adding noise to my system. Right now it is dead silent and any added noise would not be acceptable. I have not read any reviews that mentioned noise, but I have not researched it as much yet as schu probably did. For the question of gain; does my amp have enough gain? I think so. It sounds very good to my ears. Should it have more? I don’t know. Would adding a hotter signal bring out more detail? Will it add more punch and definition to the bass? Would both of these occur at lower listening levels with a powered pre? Bringing out more definition and detail would be the main goal of adding another element to my system. Having a way to switch sources would be nice too, but I mostly listen to CDs. Decisions, decisions.

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Guest wdecho

I think it would increase the chances of more noise unless the preamp is dead silent. If there is any noise in the preamp it will be amplified by the power amplifier just as signal. No benefit on noise but chance of making system nosier. As far as having more gain improving things I would not say so. One can have the illusion of bringing out detail because of the increase of gain. I do not think adding a preamplifier when you have enough gain with your amplifier will add anything other than maybe adding some flavor to the music which you might find delightful. I have a B1 Nutube which uses a special kind of tube that adds favor to the mix being advantageous with some SS amplifiers but it is in reality a sound effect device. If you test any tube preamplifier with a distortion analyzer you will find a dominant 2nd harmonic signal being added whether PP or SS. But getting back on whether you may like having a tube pre in you setup, it can depend on your taste and the preamplifier in question. Still no concrete answer without hearing the pre you are favoring in your mix yourself. You may find at first it is a good thing then later get tired of the sound effect being added. I personally find no advantage adding a tube pre on a tube amplifier where one is not needed.  

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Guest wdecho

I've taken the time this morning to make and show you a screenshot of my Oddwatt ,Bruce Herring, SRPP preamplifier. You can see that this is an extremely quiet design which should not add any appreciable noise into the amplifier. The screenshot also shows a predominates of a 2nd harmonic signal which can be beneficial if the amplifier is too dry and sterile sounding. A PP designed preamplifier has less 2nd harmonic than a single ended one. I am sure one can find a tube preamplifier where the 2nd harmonic is less but probably not at a reasonable price. I personally like some 2nd harmonic in any amplifier but if your tube amplifier already has a dominating 2nd harmonic you will be adding more with most any tube pre. 

Screenshot (28).png

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Listening through my tube amp vs a MyRef   Chip amp I notice a few things. Most dominant is the 3D effect or imaging. The tube amp kills the MyRef in this dept. the MyRef is accurate and sounds good but it just can’t touch the tubes. I don’t know if I would call the tube amp overly warm, but it sounds natural. How much 2nd harmonic is present I really can’t say. I know I have read all over the internet that many people prefer to combine SS with tubes or any combination of both. While many others prefer to be exclusively all tube or all SS. Both sides claiming there is a cumulative effect. I’m my situation I may have to find out for myself. I did forget to mention that the CD player is also driving a bash amp for my horn sub. Not sure how I forgot that  or what difference it will make but there it is. I have read a little in the past about the B1 with the korg tube. It sounds interesting and I did not know Nelson had made it available. I have had a B1 board and parts in my project pile for many years. I never got around to building it because I was having so many failures with alps and tkd pots. That’s what pushed me in the direction of the Khozmo. I will try to source some measurements on the aikido today.

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Guest wdecho

Build from this schematic instead of the old B1. Much better in my opinion and easy to build on a perf board. I use it more than any pre I have enabling switching and use of sub with any amplifier. It is the one Firstwatt sold the last few years before ceasing production. The Nutube pre is not available as a complete unit and to my knowledge no board either. Pete Millet's boards are very similar and the one I built. Nelson refined the circuit some in his presentation at BAF last year. Other than playing with it some after building it is not getting any use at my house. Cheap and easy to build using a board for a project though. I have a build thread on this forum.

 

  http://www.pmillett.com/Nutube_buffer.html

 

590144d1483672210-b1-rev-2-a-b1-r2-gif

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Well I have shifted gears a little on what I want out of a preamp. I do plan on expanding to other formats at some point so having the ability to switch between them would be convenient. Of course a perfectly good rotary switch just won’t do so I am going for somthing a little more complex. Having a remote would be nice too. Not that my room is very big or my components are very far away, but it would be nice to have. I am happy with the Khozmo unit that I have used for volume control, but wow they have some interesting new offerings!

 

After several emails back and forth to Arek the owner of  Khozmo I decided on the foundation of what will be my new pre. I am going to use the new 64 step relay attenuator with remote and the 6 source selector. These will both be powered from a small power supply board. The source selector has a built in AC relay to switch power on to the amp section. Momentary switches operate the source selection and power supply. Everything has it own led outs for display. And there is a digital display. Once this is all put together I can experiment with whatever line level amp or buffer I want. The other option is to use it as a passive and bypass the pre section. I am thinking of using my enclosure that will allow me to add a phono pre and a DAC down the road if I so desire. I guess with six Chanel’s I could have a buffer and a line level amp in the same case and just switch between them. 

 

I do do want to test the cumulative effect of tube circuits. I am leaning towards the tubes for hifi sp14. 

 

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That's really what I want to try is one of his 64 step passive units... but I don't need all that source selection.

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7 hours ago, Schu said:

That's really what I want to try is one of his 64 step passive units... but I don't need all that source selection.

The source selection is a separate unit. It just has so many features built in. I used to have two separate boards and a relay to do what is all ready built in for the power function. When I start adding things up the price of the source selector starts to be a bargain.

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I use a Cary SLP-98P-F1 tube preamp(driving my Latino ST-120 amp) for 2 major reasons. First, I have many source components, such as a reel to reel, cd player, cassette deck, turntable, oppo blu ray. I like the convenience of being able to use the tape loop for recording, plus the powered volume is a nice feature also. It also has a tube phono amp which is really nice. I am a big tube roller, and like to be able to tweak the sound by using different tubes. 

  Yes, there is a potential for added noise with more tubes in the circuit, and it gets very expensive at times to find good quality tubes. But in the long run I am very happy with the overall presentation

ATR 700 003.JPG

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I run a tomcat audio pre

I enjoy the ability to adjust bass treble and midrange

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On 4/1/2018 at 7:59 PM, No.4 said:

considering adding a tube pre amp

Yes; no clue :D  Love to have tone controls even though I barely use them :( Have a Dynaco PAT-4 preamp on my Bob Latino VTA ST70 amp but just not sure about it. Tried my Oppo DVD player WITHOUT the preamp and think it sounded better.  But ... could just be the age of the preamp ... looked at buying PAS-3 preamps ... then found a JVC P-3030 preamp ... supposed to be VERY good ($415 in 1977, so that's $1500 in today's dollars :) ) "Enroute" to me ... will let you know when it is hooked up :D 

Cheers, Emile 

s-l1000.jpg

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