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03-30-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 1
Post ID: 835
Reply to: 835
HELP: I’m a line-level looser.

I am pissed, disappointed depressed and my ego is a size of a brains or an average audio-Moron.

For a last number of days/weeks I was truing to do something extremely simple and still I had failed with a disasters fiasco. All that I need was some kind of vacuum tube buffer that would have no-gain of a very low gain and that would be sonically completely transparent. Believe me or not but I was not able to make such a stage (of whatever radical designs I trued) that would deliver a level of transparency that my playback would demand.

So,

I am depressed and semi-suicidal…

Anyhow,

if any could point to me to some kind of no-gain of a very low gain buffer then please let me know. To whoever lead me to a direction of line-level transparency I promise to make a reword.  Nope it would not be a first born but rather as a compilation/s of my selected musical peaces.

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-31-2005 Post does not mapped to Knowledge Tree
Antonio J.
Madrid, Spain
Posts 272
Joined on 08-16-2004

Post #: 2
Post ID: 836
Reply to: 835
So I assume you've tried

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building a preamp based in the same tube you're using on the Melquiades and results aren't what you expected. Have you?
I wish I knew how to do it, I'd love receiving a compilation of your favourite music. Anyway, why do you think you'll get better results with no gain or very low gain? As I see it the problem might be that the tubes you've tried aren't completely lineal, so they introduce their own sonic flaws to the signal. Maybe all you need is trying a simple approach regardless of gain, and doing it with the most lineal device you can find, perhaps an opamp or a RF tube. Probably this makes little sense or is too complicated to implement, but you know, ignorance is dared.
The other way to go might be using the buffer section of a known preamp that you like, it might not be completely transparent but would introduce modifications which go in a known and liked direction. Maybe Lamm's buffer is all you need.

Rgrds,

AJ

03-31-2005 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 3
Post ID: 837
Reply to: 835
Re: Don't worry, we're all line level losers!
Hi Romy,

I've tried several linestage circuits none of which have been entirely successful.
I'm currently slowly building a line stage based on a choke loaded 10Y tube. See VT52.com, DIY, projects, Firefly. This is about as simple as it might get. I will be using a more interesting HT supply than batteries and LT supplies for the 10Y's from Tentlabs. (http://www.tentlabs.com/)

The output coupling caps and cathode biasing components will be experimented with.

I will also be using a stepped attenuator that you can buy from Taiwan on ebay. I already have this and it seems quite transparent in comparison with the potentiometers I've tried.

Given your apparent aversion to dht's you might not like this but I'll let you know how it is when I've finished it.

Guy
03-31-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 4
Post ID: 838
Reply to: 835
I do not know where it leads me…

I have no “apparent aversion” to anything at this point and I would accept absolutely anything that would deliver a result, no mater how crazy it would be. I do not talk even about the X-factors or about anything “kinky” but only about a plane transparency.

You know this state whet a line level device introduce no sound and an introduction of it into a signal path change absolutely nothing? I mean not “almost nothing” or “practically nothing” but a situation when there is absolutely no differences between driving 150K Melquiades with for instance 47R of Bidat source and an introduction a unity gain buffer between the Bidat and Melquiades has no any kind effect to sound. Whatever I trued, no mater how aggressive it was design-wise or how well it was built was able screw the source’s sound. Practically it is horrifying in the very tiny world of lower bass’ tonal and dynamic discrimination.  In fact, it was not only there but pretty much everywhere and it always filtered out something.

Certainly I did try a number of different topologies and power supply methods, in including the complete Melquiades input stage running it into rolled-off sensitively of load or killing it gain with a feedback. The problem with all of this was that it didn’t juts deliver a satisfactory result but that is delivered a result that was not even close to the level where any serious conversation might be even started.

I juts do not want to continue on this zombie-research, building the different buffers and keep convincing myself that it was no transparent enough. I know that I act almost like a woman during PMS but so far I have managed to bult a strong prejudges and fear that all of buffers are not transparent enough.

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-31-2005 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 5
Post ID: 840
Reply to: 835
All buffers are duffers!
Do you REALLY need one?
Why SHOULD you need one?

A buffer is "simply" a device for converting impedance from high to low to drive cables but every such device loses information in the process.

With a 47R ouput impedance surely your Bidat has the current-sinking capacity to drive cables without problems?

Brian.

PS Sorry about the earlier spurious posting as a new topic Romy.
03-31-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 6
Post ID: 841
Reply to: 835
How would I switch the 6 souses?
 ....to plug the cables? :-)
 Brian Clark wrote:
A buffer …. loses information in the process
This is execlty what I would like to challenge.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-31-2005 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 7
Post ID: 842
Reply to: 835
Down with Entropy!

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 Romy the Cat wrote:
 ....to plug the cables? :-)


Well, you could do just that - just plug and unplug. Couldn't be purer than that ;o)


 Brian Clark wrote:
A buffer …. loses information in the process
This <U><STRONG>is</STRONG></U> execlty what I would like to challenge.


Come join with me in the Anti-Entropy League, let us defeat this miserable enemy that thwarts at every turn! :-))

I'm no physicist but I believe whenever energy is converted some is always lost and I think this is what we are ultimately up against. Converting impedance loses energy/information.

Brian.

03-31-2005 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 8
Post ID: 843
Reply to: 835
Re: Switches, an avoidable compromise?

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On the line stage I currently use I haven't got around to fitting a selector switch so I really do have to change the cabling arrangement each time I want to listen to a different source. As I only really use 2 sources and occasionally an fm tuner with its own volume control (Leak Troughline, very nice sounding internal buffer circuit) it's not that big a deal. My wife isn't happy about it though. She has to listen to whatever source is connected! At some point I'll have to fit a switch. Perhaps on the new linestage when it's built. Maybe I too will be shocked by how much it messes things up.

Is your quest for the best possible switch or for the whole package?

As Brian says, there will inevitably be some degradation of the sound with whatever switch you use and with whatever buffer you choose. I find that the losses incurred there are far less than the differences in quality between various recordings. It therefore isn't that big an issue. You have to accept sometimes that things are never going to be perfect and just get as near as you can.

I'd be interested to hear what circuits you've tried. Cathode followers used anywhere usually seem to have a shocking effect whenever I hear them. The Leak Tuner mentioned above perhaps being an exception (although that too has a signature albeit quite a pleasant one.)
03-31-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 9
Post ID: 844
Reply to: 835
An avoidable compromise?

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 guy sergeant wrote:
.... there will inevitably be some degradation of the sound with whatever switch you use and with whatever buffer you choose. I find that the losses incurred there are far less than the differences in quality between various recordings.
Hm, I think you have an incorrect vision of the subject if you feel that “l...osses incurred there are far less than the differences in quality between various recordings”. Let me to explain: the losses that the buffers introduce are not the losses per say but “something” that reduces the differences in quality between various recordings. They introduce a certain common denominator that minimizes the differences between recordings, along with the differences between the dynamic assent, tonal contrast and sonic transient. They act like a global umbrella over the entire system that severely subdue the system's capacity. There is something unwise to use them if we know that what they do is so devastating. It is nothing to do with me being a perfectionist or anything like this. All that I would like to have is a no-gain buffer with no sonic effect. Would it be too much to ask without being called an utopist?

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-31-2005 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 10
Post ID: 845
Reply to: 835
lower bass problems...
"Practically it is horrifying in the very tiny world of lower bass’ tonal and dynamic discrimination.  In fact, it was not only there but pretty much everywhere and it always filtered out something."

I wonder if it is the reactive components (blocking caps etc) that are to blame here, seeing as much of the problem is in the lower bass.

Just a hunch which leads me to suggest that a battery powered, dc coupled fet (ugh) buffer may be worth a try, if only because it's cheap  - see for example:

http://www.tkhifi.com/div/Erno_Borbely_fet_articel_2.pdf

I've never tried this sort of scheme, it's a longshot but I only suggest them because I suspect the coupling caps are the villains here.


cheers
cv
03-31-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 11
Post ID: 846
Reply to: 835
A white buffer flag?
Yes,

you might be on something in here. Although I used the best possible coupling caps of large values but still from point of view LF it was never “there”, even close. I also played with regulations and PS and sumized that the PS were not the reason for the sever LF deterioration . Interesting that the deterioration was identical across the anode follower, cathode follower, a regular low and high gain stage, with and without feedback. Certainly they all sound kind of different but in a way they all sound identically-bad compare to a direct connection. (For instance Bidat’s output is direct coupled, 47R across a whole audio spectrum).

I, after being so dissatisfied, am trying now to give to a direction that is quite similar to what propose: SS stage with direct coupling. I will have a result in a week or so…

Rgs, Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-31-2005 Post does not mapped to Knowledge Tree
Alex Yakovlev
NJ, US
Posts 45
Joined on 10-06-2004

Post #: 12
Post ID: 847
Reply to: 835
Re: A white buffer flag?

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I never had a chance to play with various preamplifiers in a very high-resolution system, but all the attempts that I've made with my system at home are constantly returning the same result - passive linestages seems to be the most accurate one.
03-31-2005 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 13
Post ID: 848
Reply to: 835
I'm a passive chappie too

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Preferring transformers to resistors.

Brian.
03-31-2005 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 14
Post ID: 849
Reply to: 835
A passive linestages white flag.

Alex,

yes, the passive linestages (resistors) tend to be more transparent then active stages but it is only in the case when a passive line stage (attenuator) sits right next to the grid of your input tube. As long as a passive linestage begins to drive a cable everything go to toilet with dynamic and LF dying first. My usual comment about it was something like this: a perceived quality of a passive linestage could be determined by the misery of system’s LF section – the worst LF capacity of playback the better apparent quality of a passive linestage. Anyhow, I looking for only an active stage.

Rgs the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-31-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 15
Post ID: 850
Reply to: 835
The lower bass problems...some unexpected thoughts.

 cv wrote:
I wonder if it is the reactive components (blocking caps etc) that are to blame here, seeing as much of the problem is in the lower bass.
Chris, what you said made me to think.

Look, the output of Bidat and a SS buffer that being bult for me now are direct coupled and they do “a perfect” bass. The buffers that I tried were capacitance coupled and all of them delivered identical (regardless of topology) worsening of bass. I trued the transformer coupled (amorphous Lunhale) and I lost bass as well, differently then with caps but still it was a sever lost of amplitude. The capacitors did not loose amplitude but they degenerated the quality and the definition of bass.  I did use various capacitors in there but this game I played log time ago and I know that the caps I use all were the best in existence (the same the I used in Melquiades coupling).

So, if to make a presumption that the output capacitor of the buffers was a guilty party, and this is the very same cup that is so phenomenally-good couple the Melquiades’ inner-stages then where would it lead us? Does it mean that in the “Super Melquiades” when I intend to use the same cap in the LF channel this cap will be the weakest element?  (Thanks God I have resolved the problem with the transformer). Would be a good idea do not use those caps in there but to look at something else? Perhaps a very large electrolytic cap will do better as a coupleling cap in the sub 100Hz amplifier or perhaps the back-to back electrolytics with a negative bias? Yes, theoretically in that location 6uF introduce a second order roll-off at the fraction of a hertz but perhaps there is something else in there, considering that Melquiades pumps unspeakably low bass? Perhaps it is about the shaking the dielectric or something like this?

Any thoughts on it?
The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-01-2005 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 16
Post ID: 851
Reply to: 835
The path of least resistance

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 Romy the Cat wrote:
the passive linestages (resistors)tend to be more transparent then active stages but it is only in the case when a passive line stage (attenuator) sits right next to the grid of your input tube. As long as a passive linestage begins to drive a cable everything go to toilet with dynamic and LF dying first.


Have you experimented with transformer attenuators Romy?

Brian.
04-01-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,547
Joined on 05-28-2004

Post #: 17
Post ID: 852
Reply to: 835
...perhaps too arrogantly...

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 Brian Clark wrote:
Have you experimented with transformer attenuators Romy?
Nope, I did not. I have two purely theoretical problems with transformer-attenuators.

First I did not see any transformers that can handle LF all the way down (beside ET but they are out of the game). I made my experiments in past with Lamm’s SET and was not able find any magnetics that can handle the LM2’s bass and now,  with the Melquiades, the result I sure would be even less satisfying.

Second, if we even presume that a transformer-attenuator is transparent enough (that feel will not be a case) then still the cables, switched; DCRs of primary and all the rest things are driven by the output stages of the sources. Some of them have quite high Rout. I believe that a good buffer with ultra low output impedance (I still do not have it) would be way better alternative from a perspective of noise, driveabilety and dynamics.

Still, my observations on the subject of transformer-attenuators are not based on my practical experiences as I always thought (perhaps arrogantly) that transformer-attenuators would be good enough only for a playback with those little ported monitors of 89dB sensitivity that are having the silk done tweeter… :-)

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
04-01-2005 Post does not mapped to Knowledge Tree
Brian Clark
Ongar, UK
Posts 78
Joined on 10-02-2004

Post #: 18
Post ID: 853
Reply to: 835
Arrogance? From you Romy? Never! :-))
I use S&B TX102s which have huge cores but my system does not allow examination of the subterranean levels.

I mention the magnetic solution only as an alternative to resistive attenuation. How it is implemented is another game of pinochle.

Brian.
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cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 19
Post ID: 855
Reply to: 835
Re: The lower bass problems...some unexpected thoughts.

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 Romy the Cat wrote:

 cv wrote:
I wonder if it is the reactive components (blocking caps etc) that are to blame here, seeing as much of the problem is in the lower bass.
Chris, what you said made me to think.

Look, the output of Bidat and a SS buffer that being bult for me now are direct coupled and they do “a perfect” bass. The buffers that I tried were capacitance coupled and all of them delivered identical (regardless of topology) worsening of bass. I trued the transformer coupled (amorphous Lunhale) and I lost bass as well, differently then with caps but still it was a sever lost of amplitude. The capacitors did not loose amplitude but they degenerated the quality and the definition of bass.  I did use various capacitors in there but this game I played log time ago and I know that the caps I use all were the best in existence (the same the I used in Melquiades coupling).

So, if to make a presumption that the output capacitor of the buffers was a guilty party, and this is the very same cup that is so phenomenally-good couple the Melquiades’ inner-stages then where would it lead us? Does it mean that in the “Super Melquiades” when I intend to use the same cap in the LF channel this cap will be the weakest element?  (Thanks God I have resolved the problem with the transformer). Would be a good idea do not use those caps in there but to look at something else? Perhaps a very large electrolytic cap will do better as a coupleling cap in the sub 100Hz amplifier or perhaps the back-to back electrolytics with a negative bias? Yes, theoretically in that location 6uF introduce a second order roll-off at the fraction of a hertz but perhaps there is something else in there, considering that Melquiades pumps unspeakably low bass? Perhaps it is about the shaking the dielectric or something like this?

Any thoughts on it?
The Cat



Allo,
Well, I followed exactly the same line of reasoning and what I came up with is that the coupling cap in Super Meqluiades is operating at a much higher ac level. Dunno why that should make a difference, but it's all I could think of.

I do not think that it is anything to do with the straight frequency response (6uF and 100k is about 1/4 Hz, first order, not second) - we are firmly in the murky waters of component voodoo here.

Having said that, it does not surprise me that you've found bigger transformers do better bass; cores have a memory effect, particularly at LF, where the operating point of the transformer shifts somewhat depending on the history of the signal. The way around this is a massive core with a massive airgap (sounds familiar, eh?). This is why I didn't suggest anything transformer coupled; it would kill the rest of the range.

Now, I'm still unsure as to why you need the buffer, but since you are multiamping, you might use different flavours of buffer for different bands?

I actually considered using a TVC for midrange and up and switched resistive for bass for similar reasons...

As for the cap being the weakest element in Super Melquiades (other than the potential saving grace of ac level I mentioned above), I think it might be. A possible solution is a dc coupled driver: use a level shifter after the input tube (essentially a voltage divider with a resistor up top and a current source down below with a -ve supply. This will drop the dc level but not lose gain. This then needs to be buffered by a cathode follower which is direct coupled to the 6C33.  This offers the advantage of good low impedance drive for the 6C33 and instant recovery from clipping, should it happen. I suspect you already have the required negative supply for the level shifter...

Voila, you now only have one rolloff, the OPT...

Cheers
cv

PS I was seriously thinking of putting together a Melquiades-inspired dc coupled 6C33 OTL circlotron to drive a series connected (32ohm) array of 8 Lambda 15" woofers (similar motor to scanspeak SD1, paper cone, foam surround, 20Hz fs, 94db/W each - the Cat might almost approve). The Zout of the OTL would raise the Qts to 0.5 too... but it would only work for a dipole array. No LF rolloffs anywhere in the electronics though (well, the power supply I guess...).

Your comments about dipoles have got me thinking of a line of 6 sealed enclosures a side with dc coupled S.M. as above...

Have yet to decide which I'm going to try first... I still think my idea of the "phased-array" of spaced out units may be worth trying...
04-01-2005 Post does not mapped to Knowledge Tree
Thorsten


United Kingdom
Posts 65
Joined on 12-06-2004

Post #: 20
Post ID: 856
Reply to: 835
Re: HELP: I’m a line-level looser.
Hi,

 Romy the Cat wrote:
All that I need was some kind of vacuum tube buffer that would have no-gain of a very low gain and that would be sonically completely transparent.


Completely transparent is very hard to do.

Try the following:

6AS7 SRPP, 1K Cathode resistors, unbypassed, HT 400V, Shunt Regulated (Gas Tube & KT88 Shunt element or the like).

This comes jolly close to transparent but not entierly. The only thing completely transparent I know is nothing. Even a pair of RCA Jacks and a wire inbetween is not transparent. A TVC comes reasonably close to trasparency (in a bypass test against a wire), closer than any active stage I tried on any account.

Ciao T


"It is to Madame Justice that I dedicate this concerto, in view of the holiday she seems to have taken from these parts." V
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  »  New  Preamplifiers: keys to mystery. (Lamm L1, L2)..  In analog domain...  Audio Discussions  Forum     2  45051  11-14-2004
  »  New  The ultimate buffer – light in the end of a tunnel..  A few minor corrections...  Audio Discussions  Forum     36  272740  04-28-2005
  »  New  The ultimate buffer #2...?..  invisible preamps...  Audio Discussions  Forum     3  30925  11-23-2006
  »  New  Lamm hybrids: M1.2 vs. Lamm M1.1..  Lamm hybrids: M1.2 vs. Lamm M1.1...  Audio Discussions  Forum     0  21726  12-12-2007
  »  New  Lamm introduced LL1 Signature Preamp…..  An Oscar for the most retarded comment printed in audio...  Audio Discussions  Forum     19  101571  05-16-2009
  »  New  A quests for an ultimate preamp...  Balance Control...  Audio Discussions  Forum     5  41106  05-16-2009
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