What's the real truth on hybrid amplifiers?

warnerwh · « **on:** 21 Aug 2003, 05:59 am »

I'd like the tube sound but want the SS bottom end. I've noticed hybrids don't seem too popular. Do they live up to their claim of the advantages of both and the weaknesses of neither? If they do has anybody tried the Anthem Amp 2 Spec. Edition ? Thanks

maxwalrath · « **Reply #1 on:** 22 Aug 2003, 02:26 pm »

I had the Anthem Integrated 2 and thought the Jolida 1501 had at least 99% of the performance for $1K less retail...I sold the Anthem because of the price difference. I thought the Jolida hybrids blew away any solid state integrated at that price range (especially the 30w for $325), but I haven't tried more expensive hybrids.
I thought I'd miss the solid state bottom end also, but I think the all tube set-up I have now has much better bass, just not as much slam. I definitely prefer the bass now.

EDS_ · « **Reply #2 on:** 22 Aug 2003, 07:02 pm »

warnerwh-
I have used hybrids for several years now. Speciafically a Llano Trinity 300 stereo and a Llano Trinity 3 three channel.

With these babies I can run 6 or 12 volt nine-pin tubes.

The tubes make a wonderful difference.

Llano gear is not cheap but it is very well built and has endless power. My two channel amp has 2-1.5KVA X-formers.

MGDeWulf · « **Reply #3 on:** 24 Aug 2003, 12:19 pm »

Theoretically, there are many reasons that a hybrid power amplifier should sound great. Power amps basically have two stages, voltage and current. It just so happens that tubes and solid state do two different things very well: voltage and current. Tubes are excellent voltage devices, and SS excels at current. So it only makes sense that a hybrid amp would be of interest.

Like oil and water, however, getting tubes and SS to work together can present problems. Not insurmoutable problems, but interactive problems that can affect optimum operating ranges.

Many inventive ways have been devised to get the tubes in the voltage stage (input) to drive the solid state current stage (output). When that is done effectively, a wonderful amp can result. Products that come to mind would include the early Counterpoints (SA 12 for example), Lamm, Llano and some others.

In reality, the way the art has advanced in terms of hardware and knowledge, SS can sound like tubes and tubes can sound like SS; and some amps sound like both. A SS designer can in many ways effectively mimick a tube design by manipulating feedback, output impedance, parts selection etc. Same for tubes. And there are a number of power amps that reflect that approach.

What all this has lead to is my feeling that while hybrid amps can get the job done extremely well, one can generally find an all tube or all SS design that can do whatever you want. The trick is finding a designer that has likes and listens the way you do.

Marty

JLM · « **Reply #4 on:** 24 Aug 2003, 12:59 pm »

IMO, better to find a designer that you respect and let him optimize the tube pre/solid state power amps than trying to mix and match from existing components. You also save cost/signal pathway by eliminating the interconnects.

Check out Response Audio for their RAM versions of Jolida integrateds as modded by Dan Wright and the DIY Audio chip amp forum for tube pre/I.C. amp power integrateds.

Here's another link: http://members.ozemail.com.au/~joeras/index.html

Just how deep/tight you like bass response to be, speaker characteristics, room size, etc. will affect which tube or if tube versus solid state power works best. Finally some speakers just sound better with tubes.

my 0.02

jeff

jackman · « **Reply #5 on:** 24 Aug 2003, 01:44 pm »

Your question sounds like a conspiracy theory. I have a Van Alstine Fetvalve 550EX amplifier, a design that uses tubes and solid state. The amp is very transparent, powerful and, above all, has a a very real or live sound. I love tube amps, but there are a lot of trade-offs (less power, high heat output, coloration) that seem to go along with many tube designs. The Fetvalve 550EX doesn't exhibit any of these negatives on my system. Also, since the Fetvalve system is patented (16 patents), I believe this particular design is unique to Van Alstine.

I cut and pasted some of the description from the website:

Quote

Our hybrid vacuum tube design sounds so real because it lets the individual gain parts each work in optimum environments. Vacuum tubes are great at manipulating voltages—you can play with 200+ volt signals where transistors would go up in smoke and flames. So, we use vacuum tubes for all voltage manipulations. Vacuum tubes, however, cannot drive difficult loads. They have very limited output current and get in big trouble trying to drive feedback loops, stray internal capacitances, and connection cables. So, we don’t let our tubes see any loads at all. They operate in an idealized mode amplifying voltages only, and do it perfectly.

Power MOSFETs are super current amplifiers. They can control great gobs of current without stress, and when properly selected and used, they perform without needing external compensation, thermal tracking circuits, or VI limiting and protect circuits. So we use all power MOSFETs for current-amplification duties. There is simply no roughness or compression in Fet Valve amplifiers. Our power supply features a shielded toroid power transformer and a regulated 12 volt heater supply for the vacuum tubes. The tubes see no AC ripple at all and thus have vastly extended service lives. There is a separate six-stage power supply for the active circuits with isolated supply sections for each tube and hybrid section of each channel.
Unlike other tube-MOSFET hybrids, our tube sections do not have to directly drive MOSFETs connected to real world loads, thus the tubes never load down as they are doubly isolated from the real world. The promise of true hybrid design is realized in your music system, not just on paper.

Lastly, I recently had my 550HC upgraded to a 550EX. Since I also had my Fetvalve preamp upgraded to T7, it's difficult to tell what is making my system sound so much better (the pre or the amp) but it certainly has been improved in every area. Bass is more powerful, treble is more detailed without any harshness and the overall musical presentation is more realistic (versus the older Fetvalve design). The older Fetvalve design (compared to the newer) was more "tubey" sounding. The upgrades provide more detail and a separation between instruments that seemed to be lacking in the original by comparison.

Lastly, the newer design runs much cooler than the old. My gear has been running for five days, 24 hours per, and has never gotten above warm (say, a warm swimming pool or shower, versus a hot-tub or warmish cup of tea for the older design). The older stuff would run a bit hot. Not "make me some scrambled eggs on that thing" hot like some class A or tube designs, but the metal top of the preamp case would be pretty warm to the touch.

You are welcome to come by with your speakers and check out the Fetvalve (if you are in the IL area). If you find an integrated that outperforms it for less than $3500, please let us know.

Regards,

Jman

Edit: I just noticed that you are in Oregon...too far to come to Chicago for a listen. AVA has a 30 day return policy and the Fetvalve 550EX is not very heavy or expensive to ship. I'd suggest trying it yourself on your system. For the money, I don't know of a better amp. I also believe (based on a brief listening session at my home) the other non-hybrid amps from AVA have much of the performance of the Fetvalve or hybrid designs. If you want a refined, powerful inexpensive hand-made amp, you may want to check out the Omegastar amps from AVA or even an AVA rebuilt Hafler model. I have seen a couple on Audiogon and Ebay for decent prices. All older AVA gear can be upgraded to the latest circuit designs. That's what I did with mine. For $1,100 (there was a summer sale), my older Fetvalve preamp was upgraded to T7 (with a new transformer, all new circuits including new phono preamp and headphone amp and new tubes) and my Fetvalve 550HC was upgraded to the newer EX model. They even replaced the goofy star head screws with standard philips head screws for easier tube swaps. Also, it appears the rubber feet on the older gear was replaced with new feet. I can't recall a more impactful $1,100 spend.

MGDeWulf · « **Reply #6 on:** 24 Aug 2003, 05:32 pm »

Quote from: Van Alstine

Unlike other tube-MOSFET hybrids, our tube sections do not have to directly drive MOSFETs connected to real world loads, thus the tubes never load down as they are doubly isolated from the real world. The promise of true hybrid design is realized in your music system, not just on paper....

Interestingly, as I noted in my post above, special concern has to be paid to getting the tubes and transistors to work together. It appears that Frank is using a buffer (probably an IC op-amp) between his tube driver section and the MOSFET output section. As such, the tubes are driving the solid state buffer which in turn drives the output section. A perfectly valid way to make the transition from tube driver to current output.

There are other ways of doing the same thing, as some designers don't want to place an IC buffer in the signal path. Not necessarily a better or worse way of doing things since the true test comes during the implementation more so than in the design. (though a bad design is still a bad design - even if perfectly implemented)

Marty

warnerwh · « **Reply #7 on:** 24 Aug 2003, 11:20 pm »

Anybody know of any other hybrid amps I should look at? I really don't want to spend over about 2K on a used amp. At this point it looks like nobody has anything to say about Anthem but the Llano looks pretty good and is within my price range. Thanks to everyone for your help.

satfrat · « **Reply #8 on:** 25 Aug 2003, 02:54 am »

Hi Warnerwh, peace!

I`m surprised that JohnB hasn`t spoken up about his Butler Audio 5150 as he speaks so highly of its sonic qualities. I have read/heard nothing but 5 star reviews from this 150 wpc tube amp except from Maddog comments of course.

From what I understand (and that ain`t much), each channel has a 6SL7GT tube on the output stage that takes the place of an output transformer. This allows for the high power output with <.1 harmonic distortion. It`s the simplicity of this tube hybrid w/ easily assembled module channels that convinced me to enter the high end component world with the purchase of 2 amps w/6 channels and retire my mid-fi system. As I`m still waiting delivery, I have no impressions to share but from all I`ve heard about this amp, I`m sure I won`t be disappointed. Anyways, I thought it deserved to be mentioned.

Regards, Robin

Mad DOg · « **Reply #9 on:** 25 Aug 2003, 03:21 am »

Quote from: satfrat

...I have read/heard nothing but 5 star reviews from this 150 wpc tube amp except from Maddog comments of course. ...

you forgot Sa-dono...he didn't care for the Butler either...

satfrat · « **Reply #10 on:** 25 Aug 2003, 03:55 am »

Would it make you feel better Maddog if I just said the whole LA crew? From a tube amp hybrid review standpoint from Audioreview, the 5 out of 5 star rating this amp got in it`s car applications was enough for me to take a chance on it out of curiosity. That and high recommendations from the only 2 owners of the Butler 5150 that I know of. I just thought the Butler 5150 should be brought up as an amp worthy of consideration. I would really be interested in Warnerwh`s opinion on this amp if he were to see fit to check it out. Regards, Robin

avahifi · « **Reply #11 on:** 26 Aug 2003, 10:25 am »

MGDeWolfe wrote, "It appears that Frank is using a buffer (probably an IC op-amp) between his tube driver section and the MOSFET output section. As such, the tubes are driving the solid state buffer which in turn drives the output section."

This is incorrect. The Fet Valve 350Ex and 550Ex amps (as does the Transcendence preamps and DAC) uses our patented transimpedance amplifier to drive the ouput mosfets (or the real world in the case of the preamps and DAC). This loop consists of a triode combined with a power mos-fet in a configuration that provides high input impedance, low output impedance, high output drive current, very high feedback overload capability, and a blazingly fast slew rate. The tube sees no real world load and does not have to supply current. The mosfet has no voltage gain and does not have to deal with feedback issues. There are no ICs in the audio circuits of the Fet Valve amplifiers or Transcendence preamps and DAC at all. There are very fast high current unity gain current buffers in the headphone output section of the preamps, but they are not in the main signal loop.

Its best to take a look at our circuit designs before making assumptions as to their engineering.

Frank Van Alstine

JLM · « **Reply #12 on:** 26 Aug 2003, 11:01 am »

Here's a very nice $1,300.00 USD tube pre/MOS FET power 80 wpc integrated that's been well reviewed, offers 3 inputs, neat/but limited control remote, and looks great:

http://www.6moons.com/audioreviews/unisonresearch/unico.html

If I wasn't a high efficiency speaker/SET amp kind of guy this is what I'd probably buy (and still might).

warnerwh · « **Reply #13 on:** 26 Aug 2003, 01:41 pm »

Frank: I'd appreciate learning a more about the power supply of your Fetvalve amps. Transformer and filter capacitance etc. Also any safety devices. Thank you

David Ellis · « **Reply #14 on:** 26 Aug 2003, 05:08 pm »

I don't post here often, but your post seems a good query regarding the hybrid amplifiers. I am not sure there is anything special about Franks amplifier, but this is simply because I don't understand the initimacies about amplifiers. Sure, power supply circuits are simple. When going beyond this, I get a little fuzzy.

I am not, however, fuzzy about the quality of components under the hood of Franks electronics. I peeked into one piece and saw Rubycon electro's and panasonic poly's. These are very good parts and not very cheap. I cannot say the same for the quality of many parts in my Anthem CD player. While there are some good opamps and I.C.s', the capacitors and diodes sorely lack.

If you are considering spending $2k, IMO you will not find a better amplifier than Frank's. The Anthem piece is a bad decision IMO. It does not have the quality of Franks amp. I have heard the 550EX, and it is amazing. It easily bettered my Bryston 3B-St.

If you wish to spend less and live with less power (I do), buy a Jolida and do some mods. They are good from the factory. After some mods to replace the very cheap stuff under the hood, they are excellent.

Dave

MGDeWulf · « **Reply #15 on:** 26 Aug 2003, 05:14 pm »

Quote from: avahifi

MGDeWolfe wrote, "It appears that Frank is using a buffer (probably an IC op-amp) between his tube driver section and the MOSFET output section. As such, the tubes are driving the solid state buffer which in turn drives the output section."

This is incorrect. The Fet Valve 350Ex and 550Ex amps (as does the Transcendence preamps and DAC) uses our patented transimpedance amplifier to drive the ouput mosfets (or the real world in the case of the preamps and DAC). This loop consists of a triode combined wi ...

That's great Frank. I'm glad that you clarified the situation. But what we were talking about was the difficulty of driving solid state output sections with tubes directly. It's not as easy as some think. It was then noted that you used some form of buffer to bring the two together - the rest was merely speculation used to illustrate. (note the qualifiers)

Don't get your undies in a bunch when there is no call to.

It appears that you have some very good eqipment, and people here certainly appriciate it. No harm or misrepresentation intended, just talking about getting tubes to work with solid state....something you apparently do very well.

Marty