^^ none of which has anything to do with my prior comment. Look at the quote I made- the comment was addressed to that. |
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." |
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 |
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. |
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."] |
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. |
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
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CJ no clarity...can we start over? No wonder this thread has run off the rails. |
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. |
Congrats zen, two mental defectives are better than one.
Neither of you will be advancing to the lightning round. |
LOL..a good bottle of Opus One!!.. |
I'd rather have a bottle in front of me than a frontal lobotomy. |
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!.. |
Zzzzzzzzzzz.....reactions to a full frontal lobotomy are often confused with sleep symptoms. |
ZZzzzzzzzzzz...wake me when its over... |
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. |
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 |
favorite amp conrad johnson mv 125. it's the classic tube sound. |
Relax..I'm not dumping at all on Joe. Supporting the US economy? Give me a break. Do you buy only audio components made in the U.S.A.? I doubt it. Everyone of us owns gear made in the States, Asia and Europe. However, I plan on putting together a vintage system in my home this fall and you can be assured that I will buy Psvane tubes from Joe. I am glad Audiofeil brought him to my attention, and after checking him out on Gon, its a no brainer to buy from him due to the loyalty and history that surrounds him and the immense respect given him by Gon members for many years. Appears that he is one remarkable person. Thanks Audiofeil. |
After reading the past week's posts to this thread, I throw in my two cents' worth about Joe Trelli (Trelja). Although he and I are only acquainted from a few private emails and reading each other's posts over the years, I know of his past manufacturer relationships and have to agree with Springbok10 that Joe is a good guy, and I wouldn't hesitate to do business with him.
Audiozen, maybe you need to learn what the word racism means. It has nothing to do with Canada vs. USA. You seem to be confusing the word with nationalism, another word you can look up. If you favor buying from Canadian businesses, fine, but please keep race out of the discussion. |
1. Anyone supporting the USA economy is hardly a racist, and probably should be praised, rather than called a term that is patently ill-founded, ill-considered and clearly unjustified. Check your thesaurus, Audiozen.
2. Anybody having any dealings with Joe Trelli, as I have, over the past 8 years, would know better than question his ethics, reliablity and integrity. It is of the highest order and if you took a poll on Audiogon, you would find 100% support of my contention. Note that he doesnt try to hawk his products in the Discussion fora, as do so many other retailers/manufacturers/dealers. They are all well known. (In this thread, both Atmasphere and Audiofeil are both fanatical in their maintenance of integrity and ethics, as well, and also never push their products)- So lay off Trelja - he is indeed one of the good guys in our hobby. |
Ok..Ok..Audiofeil..I'll answer so I don't hear from your Attorney..your message.."No need to deal with Canada..no way..no how"..is biased racism towards a foreign country..whats the big deal about buying Psvane tubes from Grant Fidelity?..Psvane.com website list only Grant Fidelity as their North American dealer and Grant Fidelity also has a business license in Nevada and has a warehouse located in Las Vegas. Why should I buy from Trelja? He's nowhere to be found on Google as a "premier vendor" for Psvane and has no website to sell from.
Hell, their's DIY Webmaster services online that for several hundred dollars you set up your own website with uploaded pics and get hooked up to a search optimization service with an 800 number and your up and running in 48 hours. |
Zen,
Answers please.
Especially the racism deal. |
Yoo hoo Zen, where are you?
Seems you owe a bunch of answers here, especially that racism accusation.
Man's game junior. |
|
The vacuum tubes I have purchased from Trelja have been the best quality tubes I have purchased and his prices were less than any other tube vendors with fancy websites that I have dealt with in the past. It was a pleasure to do business with him and I sure hope he is still in business when I need more tubes. |
Audiozen, I hope you will respect my general distaste for conducting business in the discussion forums. In that vein, please feel free to let me know if you desire to contact me offline, and I'd be more than willing to answer whatever questions/concerns you may have beyond what I provide here.
But to address your (legitimate) concerns in brief, yet relatively informative fashion:
1) Yes. I do have a licensed business, registered in the USA and state of Pennsylvania.
However, following the old adage, "if you want to make a small fortune in audio, start with a large one", audio is not my "real (a lead software engineer at the local Blue Cross affiliate) job" but something to instead have some fun (and make some money) with
2) No. I do not have a website dedicated to vacuum tube sales. I do maintain three websites in the high-end audio marketplace, and with the IT background, there would be no issue in standing one up if I deem that day has come.
For me, a website, which is simply a vehicle for advertising oneself, does not a business make. Rather, it must transcend that. It's effort, dedication, commitment, willingness to learn the craft, transparency, equity, honesty, relationships and reputation one makes for themselves in the marketplace, and the ultimate teller of truth, time
3) Yes. I do sell tubes out of my home. As countless other high-end audio professionals do the same, I make no apologies for that. Sadly (at least for me), for the most part, the days of the brick and mortar audio store have passed away.
Yet, it's that lack of overhead that allows me to sell tubes or whatever other product I choose at or below those who do so directly from China, while providing the assurance of dealing with a (familiar, accessible, and approachable) North American entity
4) Further, I do enjoy the transparency the Audiogon, Audio Asylum, and other high-end audio sites provide, which serve as my vehicle of advertisement for now. Inherent in that are the assurances provided to the buyer via the seller's actual (not something they themselves claim) reputation/feedback, protections extended by the site, and the overall buying process itself.
Of course, I believe this works both ways. By that I mean if the seller conducts themselves in the proper manner, they will potentially also reap dividends
5) Entities (manufacturers/representatives of both vacuum tubes and assembled kit alike) in China often inquire regarding my willingness to formally represent them in North America. To date, I have demurred.
Likewise, European (vacuum tube, raw parts [i.e. capacitors, transformers, loudspeaker drivers], and assembled kit alike) companies have also approached me about establishing a formal relationship. For the most part, I don't see the type of advantage I demand being able to provide to the end user/customer
Now, on to something far more important, Bud Fried passed away in 2005. He remains the model of something unfortunately no longer present in this business except in very rare instance. And on a personal level, I continue to miss him terribly... |
Okay Atmasphere..so is Joe (Trelja) a Distributor or a Retailer..and again..does he have a business location and a website? Every legit Distributor I'm aware of in New York and California have websites and business locations. I don't like the feeling of doing business with a "Garage Distributor"..Heck..Bud Fried still has his transmission line speaker company going for years in PA. and has a website..Let me know the name of Trelja's website.. |
Audiozen, FWIW Joe (Trelja) has been in the audio business for some time. He used to work with Bud Fried and also imported the Consonance line. |
By the way Trelja..no offense..but since your a "premier vendor" for Psvane tube's, I assume you have a legitimate licensed retail business with a retail website. Whats the name or your retail business and your retail website address so I don't feel like I'm buying tubes out of someone's home basement or off the back of a pick-up truck.. |
can we say 'the big speaker systems like proac d40 or b&w (4ohm) generally don't go well with tube amps'? Yes, and I can take it a step further- 4 ohms does not go well with *any* amplifier, if **sound quality** is your goal. If *sound pressure* is your goal you will get some small benefit from using 4 ohms with transistors, but even transistors sound better into 8 or 16 ohms. IOW if you are a loudspeaker manufacturer this is a simple way to get your speaker to seem smoother and more transparent- design for 8 or 16 ohms instead of 4. |
itsn't that funny to think rightaway to go to "trelja.net" or smt... isn't that a ".com" syndrome? :)(:
simple rx is to stay away from comp for a while and go to the beach or get laid:-) |
Yes, thanks Trelja for being the premier vendor of Psvane and Shuguang tubes in North America.
No financial affiliation with his company, just a satisfied customer. |
Thanks Trelja for your clarification..I had no idea..no offense..I'm glad Audiofeil mentioned your name since your threads and your commitment to reporting on the shows around the country appears to be outstanding. |
thank you, atmasphere.
your comment on 4 ohm speakers really helped me.
i came to know some relationship btwn gears.
but i still don't understand some about 4 ohm speakers.
can we say 'the big speaker systems like proac d40 or b&w (4ohm) generally don't go well with tube amps'?
need your opinion. |
Audiozen, "Besides, the Trelja website Trelja.net has no phone number listed and has no online order form and no product listings. Its just a blank white page with no descriptions whatsoever. Not very professional for a "premier vendor"."
I'm sorry, but allow me to clarify, please. That is NOT my website. Not sure what that website is, other than to say it's not mine. I have no affiliation or relationship with any such site as Trelja.net, Trelja.com, or Trelja.anything. |
Racist?
Better walk that back a bit.
BTW, what "race" is Canadian?
Thanks |
Audiofeil..my apologies..I stand corrected. "You need not deal with Canada in any way, shape or form?"..whats this?..Buy from America only? How racist!!..I'm certain that your Audio system has separates from Japan and Europe.
Besides, the Trelja website Trelja.net has no phone number listed and has no online order form and no product listings. Its just a blank white page with no descriptions whatsoever. Not very professional for a "premier vendor". |
Audiozen, please read my post more carefully.
I said you need NOT go to Canada.
Fact of the matter is, Trelja stocks Psvane and Shuguang tubes in the USA and ships from the USA.
You NEED NOT deal with Canada in any way, shape, or form.
Hope you now understand better. |
Member Trelja is the premier vendor for Psvane tubes regarding price and service.
Don't put too much stock in what unreliable sources may say or write. |
For those speakers and your goals, the bel canto ref1000m or 500m class d amps might work well. They are smooth and liquid sounding i would say though not inherently warm though results in that regard may vary depending on speaker and preamp used. I use an arc tube preamp with mine to very good effect in that regard. |
Audiofeil..just received an email from Rachel at Grant Fidelity. All Psvane tube orders ship direct from their Hong Kong warehouse to the U.S., Canada and around the world with free Air Mail Shipping. |
Audiofeil..your comment that you need to go to Canada to buy Psvane & Shuguang tubes from Grant Fidelity is completely false. Grant Fidelity ships from three locations and ships worldwide. If your in the States the tubes will ship from their warehouse in Las Vegas. They also ship from their other warehouses in Calgary and China. |
Zabiaud, if you really want to find out what tubes can do, you will need to think about getting a different set of speakers that are higher impedance and hopefully a little more efficient!
Four ohms sort of works with transistors, but any tube amp made will not be sounding its best on 4 ohms. Tube power is expensive, which is why before transistors showed up most speakers were considerably more efficient.
Actually, four ohms does not work all that great with transistors either. Sure, you might get more power, but the distortion will be higher and you will hear it in the form of brightness/harshness. A transistor amplifier will sound smoother and more detailed driving a higher impedance. Plus, speaker cables are far more critical for 4 ohms- they should never be run distances of over 5-6 feet, wheras with a 16 ohm speaker you can get away with hardware zip cord and it will work pretty good. Something to think about. |
Here you go.
http://www.bobcarver.com/
If you're reading this and rolling your eyes right now its quite understandable. The fact is, if you love your difficult to drive dynamic speakers as well as the presentation that only tubes can give-but the thought of large, hot, and expensive tube amplifiers is not appealing then...
The 180s or the 305s are a welcome alternative. They run substantially cooler than my 75 watt ultra linear, bias once and forget it, feedback selection for modern or warm sound, point to point wiring, no plugs or wire boards, no pricey casework, 2 ohm tap, and made by hand in the USA.
So what do they sound like? Well, ultimately, as everything in this hobby that'll be up to you. I'm thrilled with mine? What they don't sound like is solid state or switching amplifiers yet they have wonderful mid bass and surprisingly good deep bass.
I found more answers at 770-667-5633.
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I dislike using these threads for what should be a personal email so I apologize if this offends: Zabiaud, I have a conrad johnson Premier V that might meet your needs - if your near Chicago. |
You need to check this thread out as it discusses about pairing with different amps and comments from users.
http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1204173742&openfrom&1&4#1
Sorry if you already had seen it in which please disregard the post. |
Your speakers aren't a good match for a 300B SET amp. |
thanks for many tips and knowings, everybody.
my speaker system is 'dali hellicon 800' - 4ohm needed 400watt amp power.
power amp is 'mcintosh 275'
preamp is 'jeff rowland synergy'
source is 'dynaco pro'
some said 300b amp will be the best for 'warmth'
but i'm afraid that it won't be enough to drive power hungry speakers like dali800 or b$w 802.
anybody objection to use chinese shuguang kt88 tubes for better warm sound?
thanks again |
*actually i have a difficulty to match speaker systems with*
Well, what ARE your speakers? That'd help a great deal to make a recommendation. But in general, for "lush" sounding tube amps, I'd say start with Cary, &/or VTL....."vintage" means something too, sometimes older tube gear sounds more "tubey"...... |
