Crown D-45 is excellent ss

[leok]

Erik,

The cd player with the Creek at 100% IS essentially an active line

stage (the player itself, which has a lower output impedance than many

preamps, directly feeding the Crown (there is a pass through the Creek

pot wiper, but no in-line impedance because the pot is at 100%)). The

Crown pots, in this config. are less than 50% so I certainly don't need

any more gain. I think I've got what you're suggesting I try, unless

you think adding more gain just to pad it down more in the Crown would

improve something. A preamp is not going to supply a lower impedance

signal than direct feed from the TransDac I'm using.

Leo

[Erik Mandaville]

Leo:

I was thinking more in terms of output/input Imp. relationships than gain. As you said, you've got plenty of gain with the CDP performing the same function as an active stage. Actually, lots of folks, including me, could probably get by fine without an active preamp.

I'll bet the Crown sounds really nice in your system, and that's what matters.

Erik

[leok]

Erik,

I thought I mentioned the I/O impedance. Is there part of that that is

not clear? I really think I am implementing exactly what you are

suggesting. Is that not the case?

Leo

[Erik Mandaville]

Leo:

It's absolutely clear to me, but I thought you were thinking I was focusing on the gain rather than imped. aspect of this -- which I can see now that you are not. Sorry for the slight confusion there. What you've written makes me again think of taking a passive route with the headphone/amplifier combination. I had been using the CDP straight into the Moth, but found with headphones that I could detect some small but bothersome imbalance between channels -- like the image needed a front-end alignment, or something, since it would pull to one side or the other. So I inserted an active preamp (not because it was 'active' but because it was handy) between the two so I could use the balance control to fix the problem -- as well as a tiny bit of EQ provided by the tone controls. I like tone controls on a preamp.

I think if I went to a passive attenuator between CDP and amplifier, I would take another look at transformer coupling/attenuation. What's neat about that is that the signal sees an appropriately high input impedance, but with an extremely low output impedance into the amplifier. I think this may be why 10K values for volume pots are often suggested for use with passives -- where one is trying to get a reasonable input impedance and sensitivity, but with an output imped. that's as low as possible. With higher values, like 50K-100K, the input sensitivity is better, but the output imped. goes up in relation to the value of the control. So, if one were using a 100K control, the output imped. might be highish -- like 60K, or something, depending the position of the wiper. Then, if this were being used with a component downstream with a much lower input.imped., there might (possibly) be something noticable in the sound quality (?) I don't know, it's all theory here, which has nothing to do with the good sound you're getting with the Creek. My brother has one of those and loves it!

This is based on the ratio of 1/10 imped. ratio between input and output, with 1 being the source output and 10 being the load it sees. I guess this ratio is considered the minimum acceptable ratio, but, again, what matters is what one hears.

Erik

[leok]

Erik,

Possibly I am beginning to se the disconnect here. I am assuming the

Crown is a summing junction input which makes it a current rather than

Volage driven device. The way to see this is simply picture a 10K input

resistor to signal ground. The current through that resistor is what

gets amplified. The input to a tube amp is voltage sourced. The usually

very high valued resistor simply biases the input grid and provides a

very high impedance to what is historically assumed to be a high

impedance tube driven source.

The current sourced approach can be problematic for tube line stages

which can become quite non-linear as input impedances become less than

10X the tube stage output impedance. This is why it is often easier to

match a tube line stage with a tube amp rather than ss amp (some ss

amps get around this by using input buffers to create voltage inputs).

Resistances between the linestage driver and amp input, because they

are linear, do not necessarily follow the 10/1 rule. In the case of a

current input, one must decide how to properly load the true linestage

output Voltage source so that the desired current passes through the

amp's input resistor. One approach would be to use a big, series

resistor, in which case the apparent linestage resistance is probably

greater than the amp's input resistor. Done properly, this is no less

effective than padding down the Voltage and feeding the amp from a

lower impedance. You can't really do this with a high impedance

tube amp input, the impedances get way too high, and the input is

really not resistive, it is a combination of grid resistor and grid

capacitance.

In the end, you really have to know the characteristics of the actual

signal source within the linestage, and the nature of the amp's input.

A summing junction behaves very differently from a tube input or a ss

Voltage buffer stage. With a summing junction, as long as the ultimate

signal source (in my case all low impedance ss drivers under 100 Ohms)

is not overloaded, impedance network design used to provide the desired

input current can vary substantially without negative affect. Note that

the output impedance of a ss line source is not the impedance of the

ultimate signal source (op-amp or ss buffer) - it includes a series

resistor used to protect the source from short circuit and oscillation

in the case of capacitive loading. The protection resistor then becomes

part of the impedance network that eventually drives the amp input.

In the case of the Crown, I have provided it with signals directly from

the cd player (about 1K Ohm resistive impedance) and from the Creek pot

at its highest output impedance position (providing about 12.75KOhms

impedance). The Creek uses a 50KOhm pot. Worst case, the resistance is

divided in half: 25.5 to ground and 14.5K to signal + 1K for the signal

and there is 25.5K per side. Output impedance is half of that. I could

detect no difference betwen the two. That, for me, was a check of what

I suspected would be the affect of the Crown's style of input.

Leo

[PrestonTom]

Re: Using a "passive" pre-amp with a ss amp.

I have bee doing this configuration with an Adcom straight line controller (passive pre-amp). One thing that is sometimes missed is that the output impedance of the passive preamp is not as high as a typical pre-amp.

One consequence is that a long interconnect from the pre-amp to the amp, can acually introuduce some low pass filtering, since the input of the amp is typically configured to "see" a higher impedance input (this is a folksy explaination) from the pre-amp.

The corner freq of the this "filter" would simply be a one pole filter (6 dB per octave) located at

1 / (2*pi*R*C). In this case the capacitance would come from length of the cable. This is generally very small (and typically ignored) and it is specificed as capacitance per length of cable. It is best to use a cable shorter than 2 ft. This is a real effect and not "cable voodoo".

I am not advocating using some expensive & esoteric cable. A typical interconnect, if it were 3ft long, might actually low pass the signal at 13-14 kHz. The solution is simple, make sure your cable from the passive pre-amp to the amp is short.

Good luck,

-Tom

[Erik Mandaville]

Leo:

Thanks for that detailed explanation; I am clear on this now.

Erik

[sfogg]

Tom,

"I have bee doing this configuration with an Adcom straight line

controller (passive pre-amp). One thing that is sometimes missed is

that the output impedance of the passive preamp is not as high as a

typical pre-amp."

Other way around. The passive has a higher output impedance then most

other pre-amps. And it will vary depending upon where the volume

control is set. This can run into problems if you are using an amp that

has a fairly low input impedance so some system matching is required

for best sound. With a good match though passives work very well. I

used the SLC for a couple of years too.

There are some passives that have unity buffers in them (McCormack TLC for example) to help avoid this problem.

Shawn

[artto]

After reading this, I'm thinking I might try one for myself. Cost aside, would there be any advantage to bridging two D-45s over a single D-75?

No advantage unless you really need the power (and remember, doubling the power only gives you an additional 3dB of gain).

It may be a disadvantage though, because if you take a look at the spec's, you'll notice that in bridged monaural mode, while the power output doubles, the noise and distortion from both channels also gets compounded resulting in the combined noise and distortion of each channel (for all practical purposes). Whether or not this is audible depends on your particular situation.

D-60 spec:

Freq Resp: stereo +-0.1dB 20-20KHz, mono +-0.2dB 20-20KHz

Damp Factor: stereo >200 0-1KHz, mono >150 0-1KHz

Load Impedance: stereo 4 ohms or >, mono 8ohms or >

IM Distortion: stereo less than 0.05%, mono less than 0.1%

etc.

And don't forget that with these amps IMD is highest at the lowest power levels with 4 and 8 ohm loads.

[Erik Mandaville]

Leo:

...and on another note, we haven't communicated in some time -- I hope things are well with you and your family.

Erik

[Daddy Dee]

Leo,

Thanks for that explanation. In another thread Fini has been trying to

come to terms with the sound in a system set up with a Blueberry Xtreme

driving the power amp end of a McIntosh receiver.

To my very lay understanding, that could be why he is missing something in the sound.

[MICA]

[artto]

Just for reference.

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Back in the 70s Crown started getting a bad rap from a lot of audiophiles. There was a discovery of a new type of distortion by Dr. Matti Otala, which he called TIM, or Transient Intermodulation Distortion.

Apparently, one of the culprits of this kind of distortion resulted from the (improper) use of negative feedback. It seems many (technically less informed) audiophiles made the assumption that since Crown amplifiers used high amounts of negative feedback, that they were automatically prone to TIM. All of a sudden Crown amps were tizzy, or bright, or hard sounding. I find that kind of interesting because before TIM came along Crown amps were used extensively as being amongst the best there is. Even The Absolute Sound and Stereophool used them testing the legendary Infinity Servo-Static speaker. Today the Servo-Static is still highly regarded by these people, yet Crown was dumped from being audiophile quality.

For the record.I have written correspondence from a Crown engineer stating that Otala had tested Crown amplifiers for TIM and found them to free of any TIM.

Enjoy your Crown!

[fini]

It's good to be free of TIM...

[Glenn]

Going Going 4hours 33 min. left D75 on E-bay CHEEEEEEEP http://search.ebay.com/search/search.dll?sofocus=bs&sbrftog=1&catref=C6&strkw=+new&from=R10&keyword=on&fstype=1&satitle=D-75+amp&sacat=-1%26catref%3DC6&bs=Search&sargn=-1%26saslc%3D2&sadis=200&fpos=ZIP%2FPostal&ftrt=1&ftrv=1&saprclo=&saprchi=&fsop=1%26fsoo%3D1&coaction=compare&copagenum=1&coentrypage=search&fgtp=

[JulieHeartKlipsch]

I frankly don't know what to make of these wildly divergent opinions.

I'm not seeking convergence so much as understanding. Is the difference

in this thread and the other simply personal opinions/experiences/

hearing acuteness and/or deficiencies or is it more of different units

equipment in the entire system(s)? Is there no "absolute sound"?[]

Other than a magazine) Specifications if made accurately mean something

it is all in the interpretation of them. I do not want equipment

"etched" nor on the other side something "mellow." Can one tell etched v. mellow by specifications?

J.

[dragonfyr]

Unfortunately it is not too much different from debates, I mean, arguments between those who feel that religion is absolute and that science presents only a flawed representation of the natural world.

Funny how so many choose to see them as being at odds with each other...

But then that reflects the predilection of those involved and not the nature of reality...

And on this site we have many who have already made up their minds, and for which a discussion is not so much for the purpose of exploring an idea as it is a means to impose their already formed interpretation.

What might be more refreshing and a bit more productive would be a discussion of how the models, if they are so flawed, can be modified to more closely represent the thing described.

But unfortunately, few are actually aware of the current models that they are so quick to dismiss. And, heaven forbid, in an environment where, for example, complex topics like time and frequency variant impedance is overly reduced to static nominal impedance (I mean resistance!) it might be a fascinating journey to discover and learn what the existing models really say. And that would be but a simple beginning!

But let's be careful here! As we don't want to come too dangerously close to actually pushing the limits of folks' understanding and perhaps actually expanding our knowledge! ...Such heresy![][6]

[Erik Mandaville]

Leo:

Your impression of the D-45 is not unlike what I experienced with the 3-channel Teac digital amplifier. It has provided some really good sound here, and is in many ways as good as the several triode amplifiers we use. In character, the sound is not the same, however, with the single-ended amps being rather more organic in tone. The Teac is outstanding in many ways, though -- extremely efficient, able to extract very fine detail without some of the caustic quality I have experienced with some solid state amplifiers. Kelly mentioned the Monarchy amp, which is one we also had the chance to listen for awhile. I almost bought it, actually, but began to sense something of a cardboard-cut-out-like quality that it had (IMO) compared to the main amps, which at that time were the Moondogs. The sound was very good, but just didn't have the roundness of tone and notes that heard with the Moondogs in the system seemed so natural and real. That Monarchy would have made for a nice foot-warmer in winter, though! It is a very good SS amp, but just wasn't for us.

Erik

[Daddy Dee]

I have two thoughts on the widely divergent perceptions of particular amplifiers...

One is that there is not always, and perhaps not all that often, a real

apples to apples comparison. There are still a number of "real" reasons

amplifiers can sound different. It could be that a piece of used gear

is not up to factory spec. In addition to that there is a synergistic

issue of how an amplifier will sound in a particular system, with a

particular preamp. Those issues can make significant differences in the

way gear sounds.

The second thought is allowing for subjective preference. People have

genuine preferences for what sounds good to them. One of the genuine

surprises to me is that quality amplifiers still have a different

reference sound. For me, then it has become not having "the best"

sound, but sound that I enjoy and that is reasonable (to me) in price.

That's one of the reasons I really like Klipsch. The music sounds

"live" to me and is a real value in gear, IMO. Part of my enjoyment is

knowing that people spend many times what I've spent on gear, and I

like my system better. That is an opinion I'd keep to myself while

listening to a friends very expensive system... just would not be

polite to say that, but I would be thinking it. I'd express my genuine

opinion of shared happiness that this particular fellow is pleased with

his particular system. After all, that's what this hobby is really

about.... enjoying the music.

[Erik Mandaville]

Dee:

I couldn't agree more. A set standard for what is 'good,' is in my opinion inherently impossible. I have good friends or even family members that truly and honestly do not care for horn-loaded speakers of any variety. I loved the Lowthers and continue to use them, but there are people who thought they sounded horribly colored, overly bright (which was somewhat the case when the drivers were brand new), and just plain bad. The same is true for the Klipschorns, which for me and what I happen to like and/or prefer, provide a window into the music unlike any speaker I have heard. Maybe it's because they work so well with low-powered triode amps, although again, we know all too well that all opinions here do not hold hands when it comes to the topic of low-powered SE triode amplifiers.

Erik