Good thing I re-read. Atmasphere's discussion of a preamps inability to control the cable. I reconnected the preamp, but this time I ran the variable output to the preamp in. The sound is improved over the fixed output. Maybe that's because the signal running through that circuit with pot changed the impedence--or resistance or capacitance or inductance--that the preamp cannot control. You have to tune the preamp with cable or any other means you can think of. Yes? ( Atmasphere says that degradation of sound quality at lower listening levels is the same issue, which I thought must be sensitivity. I got that). This might be the most important thing I've learned so far. Lynne |
Geez, I can't believe people still talk about 600 ohms for any reason. No offense, but that went out with disco... |
Interconnects are very important w/passives. Especially where HF is concerned. Keep them as short as possible. In my system however it sounds fine at low volume. In fact I find the HF better at lower volume. This could be due to the extra headroom on my LF amp. I use a Placette resitor ladder. My only source these days is a CDP w/2.5 VRMS@ 50ohms. I feed two amps: both CJ SS w/100K input impedance and the same gain although one is 100WPC (HF) and the other 250WPC (LF) My gear has fairly ideal values for a passive setup which is critical. |
I think it is well established that I don't know anything, but if the analogue components could control the cable, then we could not hear the cable. But there is a whole industry based on the fact that cables have a sound. I never understood the reason for this.
I think I'm giving up on the passive linestage for now. Electroid, if you have the ideal components, I think mine are the worst. I've got 1.1V sensitivity@22kohn. And both my players are 2V@10kohm. Not logical. My disposable income went with the stock market, so I'm not in the mood to do a lot of experimenting right now. But I've learned a lot and that's just as much fun. Lynne |
Lynne I've got 1.1V sensitivity@22k ohm I take that to be the amp's specs, right? I.e. it reaches its peak when fed (a max) of 1,1V & its input impedance is 20kOhm. That's not too bad... But are you saying your players have an "output impedance" of 10kOhm??? That's too high... I must have misunderstood something. OTOH, 2V output is more than enough to drive the amp -- and then some. You should be able to use a passive attenuator on it. (BTW, it's called "impedance" when the "resisting" factor changes with frequency; it's called resistance, when the "resisting" factor remians constant whatever the frequency) |
We have a cable industry in high end audio based on the experience of audiophiles hearing differences in the cables.
However most audiophiles don't get that the recording/broadcast industry tackled this problem in the late 1940s and early 1950s, the result being the balanced line system.
For decades, audiophiles listened to inexpensive single-ended gear at home. Single-ended cables do not have a termination standard, so to get around the differences in cables that thus resulted, the cable industry began to develop, starting in the late 1970s, lead by Robert Fulton.
But the balanced line system has the advantage of making an inexpensive balanced cable sound as good or better than the best single ended cable (price no object). The first balanced line audio product was introduced to the high end audio world in 1989, possible because of the increased budget allowed in high end audio, but balanced line has had an uphill battle due to audiophiles not really getting why balanced line is an advantage. I hope my explanation here helps; balanced line exists specifically to eliminate cable problems!
BTW the classic passive volume control problem is lack of bass impact at low volumes. Some controls are built to be very low impedance to try to get around this problem, but that low impedance limits the number of front end products that can work with them. |
Gregm, ok. Yes, the amps spec is given as 1.1V@22K ohm input impedence. On the CDP, if you meant,"did I read it wrong", apparently not. The HD7600ll's output impedence is given as LINE- 2.0V@10k ohms. I thought the other player was the same, but now I see that a spec is not given. It's an H/K FL8400, one model newer--same DAC, probably the analogue section. So I conclude that it won't work. I am mildly interrested in a City Pulse DAC but I think it has the same spec. But another DAC might be a way to get around it. Otherwise, I assume the Placette active would work. Maybe autoformers? Thanks for the clear, simple explanation of impedence vs resistance.
Atmasphere, I finally got something right. Thanks. I've found a lower cost cable that I like but I probably have $1k in cable easily. For $1k, it probably could have been made balanced. Lynne |
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Hi All,
I am FOR the passives and not against.
There is a simple principle here - the less is more.
An additional circuit is not a benefit to the whole.
The thing is that the output of many of the sources is not
designed to drive the power amplifier directly.
Then there is the problem of impedance matching and that is why some passives use transformers.
A good tube phono pre-map having a cathode follower stage at the output will drive.
So a selector and ladder volume control (Elna, Goldpoint) at the output will be sufficient for a power amplifier with relatively high input impedance and low input sensitivity (0.5V - 1V).
Why add another circuitry in between?
Let's say that the output tube of the phono is 12AX7 and the input tube of the power amp is 12AX7 as well.
Then these circuits probably match very well.
Some do not.
'Everything should be made as simple as possible, but not simpler' - Albert Einstein. |
I hear you Aleko. What is interesting about the theory is that so many folks who have tried passives at some point go back to actives, mostly tubed. I like them both passive (rsistor and tranformer based)and tube actives, but as Guy Hummel of Placette once said to me, and I'm paraphrasing, a thousand theories as to what should sound good aren't worth one good listen. |
Very low input sensitivity might allow noise to enter. |
Unsound...You got that backwards. Low sensitivity means that, to be heard, a signal needs to be strong. Noise pickup is a weak signal. |
In theory I totally agree with you Aleko. However, when using my ears as a guide, I've consistantly found that active preamps sound more musical to me. IMS, IMHO, YMMV.
Cheers,
John |
Eldartford, thanks. Of course your correct. What I should have posted in regards to Aleko's post is that an amp with a low voltage input may permit more noise to enter. |
Unsound...No problem. I also made a mistake once. I thought I had made an error, but was wrong about that :-) |
Eldartford, I wanted to say that the amplifier is very sensible so I have probably said it wrongly. So I should have probably said high input sensitivity.
I wanted to say that the power amplifier needs low level signal say 1V rms to reach its full output.
Unsound, thanks for the info.
I have used a passive pre-amplifier and not heard noise when using the Pass Aleph 3.
Also, I have thought that the level of noise depends on the power amplifier circuitry and not the input sensitivity.
For example I have heard noise coming from the Air Tight 211 amplifier. I just want to add that this was the only flaw otherwise the sound was wonderful in all aspects.
Then I read the Stereophile review which confirmed that.
It was not mentioned there for the reason to be the input sensitivity (which as far as I am aware is set at 1V to allow use with a CD output directly).
But now you make me think the reason for the noise is exactly this.
On the other hand the Wyetech Topaz reportedly does not generate any noise due to the circuit - choke filter and so on and still input sensitivity is set at somewhere this level - 0.6 V if I recall correctly. |
