favorite amp conrad johnson mv 125. it's the classic tube sound. |
I expect Audiozen wanted something like "jingoism," rather than "racism." I expect "race" is often used (much) too loosely, but even so, I don't think it is conventionally extended to "Canadian."
Depending on what happens with Quebec, it may even be a stretch to refer to Canada as a country! (Of course, if Rick Perry is to be believed, the same might be said of the US and Texas.)
Yours lexicographically,
John |
canada is a country not a race. i hope that ends the discussion.
audiozen. you used the word race incorrectly. go check the dictionary for a definition.
did you ever take a course in anthropology ? you would learn about race if you did. |
ZZzzzzzzzzzz...wake me when its over... |
Zzzzzzzzzzz.....reactions to a full frontal lobotomy are often confused with sleep symptoms. |
Audiofeil..After an extensive conversation this morning with my Audio friend Richard in Chicago, he will be ordering all Psvane tubes from Grant Fidelity today for his David Berning gear and looks forward to the upgrade!.. |
I'd rather have a bottle in front of me than a frontal lobotomy. |
LOL..a good bottle of Opus One!!.. |
Congrats zen, two mental defectives are better than one.
Neither of you will be advancing to the lightning round. |
Audiofall..lightning round?..boy, do you have child issues. I gave up baby competitions at the age of four and had no further use for my sandbox. If you want to let go of your childhood skeletons and get rid of your sandbox, I would recommend putting it up for sale on Ebay, or better yet, install four outdoor cube speakers on the four posts and list it on Audiogon. |
CJ no clarity...can we start over? No wonder this thread has run off the rails. |
Zabiaud, Welcome to AudioGon and your first posting here. In answering your question disagreements have arisen that may be of some value to you or not. In any event it has nothing to do with you personally.
Regarding your 4 ohm speakers. In my earlier post I suggested a tube amplifier and offered some of my personal observations with them. I'd like to offer a bit more detail.
My speakers are 87dB / 4 ohm yet they dip down to 3.6 ohms. I was powering them with a powerful 200 watt solid state amplifier as well as a 375 watt switching amplifiers. The solid state amplifier would begin to sound congested when turned up and the switching amplifiers had no problem other than the difference in their presentation.
The Carver tube amplifiers can be run at high volume without any audible issues that I can hear. They're highs sparkle, the mids have depth and weight with solid mid bass and surprisingly powerful deep bass. They come with a switch that changes the amount of feedback which gives you a modern or vintage tube amplifier sound. They also have that relaxed feel that only tube amplifiers offer.
I suggested these because they are the first tube amps that were not excessively large, hot, and expensive. More importantly to me, they are able to comfortably drive my 4 ohm speakers while sounding much better than the other amplifiers I was using.
My personal experience with tube amplification is limited to Marantz 8B's and an MFA D75. Neither of which could drive my 4 ohm speakers beyond background music levels. I hope this has been of some help.
Whatever you decide on I hope you will return and share your experience.
Vic
|
I had a 360 w/ch Carver m4.0t SS Tube Transfer Function amp for many years.
This was one of Carver's efforts to "voice" a SS amp to sound like a tube amp and was reasonably successful at that.
A corollary to that was that although it went plenty loud and clear, and did well with my speakers that were relatively tube friendly at the time (Magnepan, Triangle), it was also not able to deliver balanced sound top to bottom with my other less tube friendly speakers (B&W, Dynaudio, OHM) despite also going plenty loud.
FWIW. |
Mapman,Yeah I was a bit skeptical of the Carver name. After more reading it became clear these new tube amplifiers area collaborative effort. IMO and in my system I'm extremely happy with their presentation.
This is from a review, not sure which one.
["The new Carver amplifiers should be understood as a collaborative effort between Bob Carver (pictured here) and Tim de Paravicini. Bob relates the following: "Tim and I got together a few summers ago in a small California town (Sebastopol) when he came from England to do a service call on his amps for a big record company. I'll never forget that day as long as I live. Tim designed the input and driver stages, and together we designed the output stage. I designed the power supply. Tim taught me how to design the output transformer." The input signal is AC coupled to a 100 kOhm potentiometer, which defines the amplifier's input impedance. The input stage uses a 12AX7 configured as a long-tail pair phase splitter using a large tail resistor to ensure constant current source operation. The driver stage uses a 12AT7 also configured as a long-tail pair."] |
Just take any tube preamp and change the caps to oil caps so you get a warm, tube like sound. It is that simple. You can also changeout the filament resistor to adjust the voltage to the tubes and warm up the sound (relax the sond). No need to try different preamps if that is all you are looking for. |
The input stage uses a 12AX7 configured as a long-tail pair phase splitter using a large tail resistor to ensure constant current source operation. :) He must be new to differential operation. You can't do that effectively with a resistor like that- you will need a proper constant current source (CCS) if you really want it to work right.... just say'n |
I don't have a clue as to what your say'n. This is from a Dick Olsher review. Maybe there is some information here that might explain things for you.
A Few Technical Details
Push-pull Class AB operation is essential to maintaining good efficiency in a high-power amp otherwise you end up with a space heater and poor power tube life. And within this context, Bob Carver seems to have made all of the right design decisions. Let's start with the KT88 plate voltage. At 725VDC, Bob has entered a HV frontier where no designer has gone before, and it's a choice that is bound to raise a few eyebrows. High plate voltage coupled with a cold bias setting near cutoff allows for huge voltage swings without encountering tube saturation. But one traditional argument against use of a high plate voltage has been the need to operate the output stage at low idle currents in order to stay safely within the plate dissipation rating. The end result is of course only a few watts output in Class A and the potential for increased distortion when each half of the output stage is driven into cutoff. This would appear to be a classic conundrum of efficiency vs. distortion. Can you really have your cake and eat it too? The fact is that the Cherry 180's total harmonic distortion remains less than 0.5% at any power level. How's that possible, you ask? Well, it's partly a function of some global feedback, but mainly this is due to Bob's secret weapon his DC restorer circuit, to be discussed later.
Just how cool running is the Cherry 180? The front panel bias meter displays the combined idle currents (plate plus screen) for all six KT88s. To obtain the idle current for a single KT88, the meter reading needs to be divided by six. Bob sent me measurements of the plate and screen currents for one of the KT88s. At idle, the plate current measured 11.6 mA at 715V, while the screen current measured 0.3 mA at 375V for a total dissipation of about 8.4 watts. To quote Bob: "Cool enough so we can't injure ourselves if we hold on to a tube. Still, and just the same, I would not tempt fate by holding on for an extended time. I'm sure it would feel quite uncomfortable." The idle current may be adjusted via the bias pot to a maximum of about 150 mA.
And what about tube reliability at high plate voltages? Bob reminded me that all push-pull designs approach twice their plate voltage during dynamic conditions due to the coupling between the two halves of the transformer's primary winding. For example, a 200V drop in one half of the Cherry 180's output stage (from 725V to 525V) would give rise to a voltage of 1250V in the other half. Furthermore, Bob says that "the only worry would be arc-over inside the tube. I did some experiments to find out what voltage on the plate was required to make it arc-over inside. No problem at three thousand volts." Note that the tubes are warranted for an unprecedented period of one year!
Fixed bias is used rather than cathode bias, which is the right choice for overdrive conditions. To begin with, cathode bias is wasteful of B+ voltage. An even more important advantage is that since fixed bias is not affected by large plate current fluctuations, the operating point maybe set closer to Class B operation without the penalty of increased distortion.
The DC Restorer
Carver says he copied the DC restorer from old TV circuits with tube video amplifiers. "Those sets needed to deliver the DC component of the video signal to the CRT all the way down to DC. As used in my amp, this circuit reduces distortion by a factor of three as well as the tube dissipation by approximately the same amount. It works by keeping the DC component on the control grids the exact correct value over the whole signal swing, getting rid of the need to operate the tubes at very high currents (even at low level operating conditions just to get them to work right). The main thing that causes non-linearity in tube amps is that the screen voltage drops when the amp is driven, not so much because of low idle current to begin with (though higher idle current does make for lower distortion, but the trade is a bad one). It takes lots of idle current to drop the distortion a substantial amount, so the DC restorer is a better choice than lots of idle current. I get lower distortion at eight watts idle per tube than at 28 watts idle per tube."
The restorer is simple yet ingenious. It uses a 6AL5 dual diode. Each diode section services one bank of power tubes. The 6AL5 cathodes are connected to the control grids of the push-pull power tubes which are held at a nominal fixed bias of -47VDC. The diode plates are at an acquisition threshold of -56VDC. Bob admits that some aspects of the DC restorer operation are somewhat mysterious to him, as they are to me as well. My take is that the circuit aids significantly in recovery from hard cutoff conditions. Under those conditions the KT88 grids act as rectifiers and shift the effective DC level below -56V, to the point of causing the 6AL5 to conduct momentarily and pull the DC bias back to its nominal value. Bob estimates the lifetime of the 6AL5 as about 50 years. "I know that seems wrong, but 6AL5's are ubiquitous in tuners, and 50-year old tuners always have these tubes and they still check as new. There are so many of them in this world that a guy on eBay sells a string of them for three cents (each tube) to be used as Christmas tree lights." |
^^ none of which has anything to do with my prior comment. Look at the quote I made- the comment was addressed to that. |
