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The "Right" preamp for me

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I'm running upgraded 68 khorns powered by my recently assembled tubes4hifi Bob Latino st70. Currently just using a preout from my Yamaha 1030 avr. 

 

This is the preamp I was thinking of playing with. Is this a step in the right direction? Is there something better bang for buck kit or not? Will I hear a difference by adding this to my system?

 

http://www.tubenirvana.net/pas-ngt-tonepreamp.html

 

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It is hard comparing products without hearing both. I have built this one but not from the kit but point to point.  Many consider the different variations of the 12AU7 tubes better than the 12AX7 tube for an audio preamplifier. 

 

http://oddwattaudio.com/owforewatt.html

 

http://diyaudioprojects.com/Tubes/ECC802S-ECC82-12AU7-Tube-SRPP-Preamp/

 

As far as hearing a difference from what you are now using is anybody's guess being that what one hears is so subjective. But I have built a number of Bruce Heran's designs and all were excellent and quite. 

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Why not get a tubes4hifi sp12?

Its based around the aikido circuit and 6sn7 tube.

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If you are only using high level sources like a CD player or DAC you should be able to directly drive the amp if you install a volume control (I believe Bob offers a nice stepped attenuator for that purpose).  The less electronics in the signal path the better.  In comparison, a preamp can only degrade the sound.  And, if you need a phono stage, you can use the one in your Yamaha.  A simple external switch box makes it easy to select which source is connected to the amp.

 

Maynard

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To me the Tube Nirvana preamp has a better chassis/face plate/ overall build quality compared to the tubes4hifi SP12. It costs about the same (with tone controls) and $50 less without which I believe is the only way the SP12 is offered. 

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Maynard,

 

You observed, "...a preamp can only degrade the sound."

 

I'm in agreement regarding the benefit of a simply in-line attenuator between a high output source component, and have built many such "passive" devices in the past.  They can work well if certain prerequisites have been met.  Appropriate impedance matching is critical as you know.  Where a preamp can arguably be beneficial has to do with its potential impedance buffering ability -- a quick example of course being a simple cathode follower (which not all people care for).  There can also be considerable increases in capacitance associated with longer runs of interconnect, and that in turn can be aggravated by higher source output impedances -- both of which make it difficult for a signal passing through a passive attenuator to get much traction.

 

We of course know of active line stages with sonic characteristics that well out-weigh and compensate for the fact that, being either of a hollow state or solid state design, they provide signal gain, impedance matching/buffering (or both) and have a power supply.

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And to sort of finish my thought on this, we shouldn't neglect to mention that, if one were in favor of an in-active (aka 'passive') means of controlling the output gain of a source, one approach which is thought to be greatly better than a basic audio-taper pot involves the use of transformers instead of potentiometers.  They provide a very high input impedance for the incoming signal to work against on the primary side of the winding, while offering considerably lower output impedances on the secondary (output) side.  In fact, there are those examples which can actually provide a certain degree of what we might call 'passive gain.'  Cost of entry, though, is exponentially higher for dual mono transformers in comparison to either a two-section stereo or dual-mono potentiometer arrangement.

 

Maynard's well-made point, however, remains:  That modern source components usually have more than enough signal strength (gain) on their own to drive a large majority of amplifiers to full output.............and beyond that into clipping.  And so he is simply saying that adding more circuitry to an already very strong and pure signal may (subjectively speaking) ultimately do more harm than good.  Whether or not that is the case, though, depends on an assortment of different factors.

 

Which brings me to what I think to be an oddly ironic thing about active preamplifiers:  That they are in actuality more often used to attenuate a signal by turning it down than the reverse of that.  How? What will be the result of taking the full, unattenuated output of a CD player, DAC, etc., and connecting directly to a power amplifier?  In other words, a preamplifier is not too unlike the oxygen regulator on a scuba diving air tank or the control knob on a gas stovetop.  They are used as a means to control, harness, or attenuate an otherwise extraordinarily strong potential. 

 

 

 

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I had a pair of tapped autoformers for volume control use, and the brand are rather well known. It was a kit more or less, except one had to provide an enclosure/case, and connectors.

I took my sweet time and made sure things were properly wired.

 

In use, I liked the midband to top audio band of the autoformer's "sound". But the bass wasn't there, no matter how I stacked the laminations, which was an option. And there was this sort of subtle saturation sound when in use.

And I checked over the connections several times, even asking questions on the site's forum.

 

In the end, the "sound" of the tapped autoformers just wasn't for me. It's a excellent product however, and I really like the guy, and maybe I did something incorrect. But with regard to just using a passive type volume control, a simple resistive potentiometer or a stepped attenuator is the choice for me.

 

Out of boredom one day I took each autoformer and connected a signal generator to the input, and a scope lead to each tap, (unloaded) and ran square waves from 50Hz to 30kHz, monitoring the scope for ringing of the autoformer's on each tap.

Each autoformer had a bit of a ringing overshoot on the front left edge through the whole audio band. (all taps)

30kHz was a mess, but the harmonics of higher frequency square waves will round out the "square" of the wave at the source, not necessarily the device under test.

 

You can do the same thing with a simple resistive potentiometer, (carbon trace, whatever) and the pot will pass fine square waves with of course no ringing.

I brought this up to local retired audio engineer...his comment was something to this regard: "It is to my knowledge that a transformer/autoformer should never be used as a resistive divider."

 

 

 

 

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so all of us with powered line stages are doing it wrong?

I still have not tried a passive... might be time.

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Schu,

 

Absolutely NOT doing it wrong.  We have discussed here and I on other sites where an active line stage often bring much more to the proceedings than a passive.  Again, a matter of preference.

 

Simple carbon pot can be fun, I've made quite a few of them -- if appropriate impedance matching precautions are met.  Get that messed up, and things will not be good.

 

Yours is the only case where I have heard a single negative comment about transformer-based gain control (by those who like them).  Maybe you just don't care for the way they sound, and if that's the case, you, as I and everyone else here, will choose another signal coloration to his or her liking. Use what YOU like and what sounds good to YOU, not what someone else tells you you SHOULD like because they've been at it a million years longer.  Suggestions, fine; final choice is for the individual, IMO.

 

edit:  My reference to the transformer VC in the third paragraph above was directed toward Mike, not Schu.  My fault for not making that clear.

Edited by erik2A3
clarification

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My preference is the Firstwatt B1 buffer using J-fets but that being said if there is no impedance mismatch a passive has always worked fine with me. An opamp buffer is easy to throw together and sounds really good as well. 

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They might be a necessary evil but I stumbled onto the reality once that the preamp does lower (degrade) the sound.

 

I had a bunch of wires behind the system.  I was on my knees, working in the back where it was dark.

 

I happened to have an amp that had a 1v input sensitivity.  I miswired the preamp and plugged the CD player directly into the amp (and the amp was connected directly to my Khorns)

 

Took me a while to figure it out but I was stymied as to why I couldn't adjust the volume at all....  it was simply set at a certain level (CD didn't have a variable output)

 

As I listened, it dawned on me that the sound had a better quality about it.  Hard for a klunk like me to describe but, those words that some use came to my mind... "more liquid" "fuller" "less steril"

 

I was actually kind of bummed when I realized what I had done and that I had to put the preamp back in to get my various sources back into the system.

 

It was an eye/ear opening revelation for me.  Frankly, I didn't even know at the time that the CD would even work connected like that.

 

 

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Coytee,

 

It may have to you under those circumstances.  I think it good you stumbled on something you like -- really great things can be discovered by accident.  That said, it is not an automatic truth that a preamp degrades sound quality.  Perhaps in your case, but it depends greatly on the preamp you were using, and all preamps are arguably not the same in terms of sonic quality in various systems.  I will say I have heard the same as you, and quite honestly stopped using the preamp I had been using.

 

At the present time I have preamps that I would say absolutely fly past ANY passive I have ever used.  The one I am using now is based on the 300B triode, and has outstanding current delivery into long runs of IC.   It is like polished glass, with really great frequency extension.

 

But, by all means!  use the CD without the preamp if it sounds better to you!  I would guess, then, that it has variable output capability, because if you ran its full (fixed) output straight into a power amp, the walls would have come down.

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Nope...  I'm back to using a preamp.  If nothing else, need it to feed the active crossover which as I understand, needs a little more voltage on the input side.  (Xilica unit, formerly used the EV-DX38) 

 

The preamp I was using was a Peach which is generally well regarded around here.

 

Regarding the walls coming down, the system had some kick to it but wasn't terribly loud.  (mind you this was 10 years ago so I might not remember all the details)

 

As I recall, you could have had a conversation but you would have had to speak a bit more loud and paid attention when someone else was talking.  Certainly nowhere near what the Khorns were/are capable of.

 

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Not quite sure what you're talking about in some cases.  I was on the Peach roadshow when Mark D. first introduced it.  My wife adored it.   It was, and still is, an absolutely  outstanding preamp.  And we in fact used the Peach with our Klipschorns.  Mark is a most respectable designer who has influenced others on this forum.  I wish I bought one at the time.

 

Coytee,   I joined this forum in 2002, and have been through quite a bit of its development.  I left for a time to focus on my own building, but hopped on again several years ago.

 

So......nice.  You're back using a preamp.  swell

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there is a passive I have been dying to try for not much money... maybe its worth a gamble.

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15 hours ago, erik2A3 said:

At the present time I have preamps that I would say absolutely fly past ANY passive I have ever used.  The one I am using now is based on the 300B triode, and has outstanding current delivery into long runs of IC.   It is like polished glass, with really great frequency extension.

 

 

Any active preamp can only add noise and distortion. When you say "fly past" I am guessing you like a little coloration since you are using a 300b line stage. For people that want purity and have low Z out sources along with high Z input power amps a resistive divider and a source selection switch is all you need provided your not trying to run long cables.

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On 6/18/2017 at 4:12 PM, mike stehr said:

I brought this up to local retired audio engineer...his comment was something to this regard: "It is to my knowledge that a transformer/autoformer should never be used as a resistive divider."

 

 

 

 

 

 

I would have to agree with him.

 

 

For blokes that can't seem to get rid og ground loops in their setups an audio isolation transformer can galvancally isolate equipment and put an end to pesky hum issues. Quality ones are expensive.

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ANY component will add something.  I also already stated that passive attenuation can work very well under the right circumstances.  "fly past" : meaning speed, unencumbered by undesirable effects of long runs of IC (my situation).

 

Do you own and listen to an amplifier of any kind?  An amplifier can only add noise and distortion.  Do you listen to loudspeakers?  Passive or active crossover?  You like the colorations contributed by passive devices called capacitors, resistors, and inductors.

 

We ALL have our own preferred selection of colorations.  We are listening to electronically and mechanically reproduced music -- by its very nature a coloration.  Listeners to music in the distant past were thus in a sense far more advanced than their present modern counterparts:. They didn't rely on machinery to vibrate the air for them; they listened to musicians playing instruments.

 

So, certainly.  I enjoy my chosen compromises and colorations tremendously.  I hope you do as well, because that's what you are listening to.  We all are.

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The voltage coefficient of resistors, especially metal film is so low you can't even compare the added distortion to that of what a directly heated triode will add from non-linearity. For people looking for accurate reproduction a resistive divider will be much more transparent. In your case where you need a buffer for cables the passive route isn't an option, but for some people it is an option and is also the most transparent. 

 

 

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