I would look into a new Jolida JD 202A for $825 and a pair of new Klipsch RF-52s for $500.

The Jolida JD 1501A hybrid 100 wpc integrated amp for $695 should also get consideration. The preamp section has 12AX7 input tubes driving a MOSFET solid state power amp section.

Charles,

Congratulations on your decision to step into the realm of high-quality music reproduction! As you've found in your search of Ebay product offerings, high-performance vacuum-tube equipment doesn't necessarily have to come at high expense. However, please maintain a reasonable level of caution; while many of these Chinese-sourced vacuum-tube products are well-made implementations of classic audio designs, a number of folks have had less-than-optimal experiences. Caveat emptor...

Based on the tube complements listed for each of the products that you've identified and the specified power output levels, it appears that these amplifiers are probably variations on the classic "Williamson" push-pull power-amplifier design, a circuit configuration which underlies a large percentage of the products produced in the 'golden-age of high-fidelity' during the 1950's and early 1960's (for technical details, just "Google" for "williamson amplifier schematic"). If the amplifiers that you have under consideration are, indeed, "Williamson" power-amps, then they would represent implementations of a well-proven circuit topology.

The quality of the supplied vacuum tubes can have a significant impact upon both the sound quality and the cost of the amplifier. A useful primer is available at Upscale Audio (http://www.upscaleaudio.com), which has an excellent on-line store for vacuum tubes that describes the performance differences between the grade-levels of the same model of vacuum tubes offered (even within tubes from the same manufacturer). The "good news" is that tubes can be replaced with units that match your music-listening requirements.

The output transformers represent another major quality nexus in vacuum-tube power-amplifiers; while a "entry-class" 60W push-pull output-transformer from Hammond Industries costs about $80/each, a "world-class" equivalent from Plitron costs about $320/each. The "good news" here is that even "entry-level" output transformers are usually pretty good, they just don't exhibit the additional levels of audio transparency available with the premium units.

As you noted, there's a pretty noticeable difference in the level of industrial-design between the Yaqin and Music-Angel products. The additional materials and machining required to produce the cosmetics of the Yaqin MC-100B could well account for most of the cost disparity between the power-amplifiers under consideration. Certainly, the Yaqin unit has a very high "coolness" factor in its favor... ;-)

As you can surmise from the discussion points above, any or all of these factors could account for the price differential; there's simply not enough information available to know for certain. Just do your Ebay-related due diligence in checking-out the vendors and enjoy the music!

Charles,

The "Ultralinear" term describes a push-pull output stage that uses pentode power tubes (the "Ultralinear" circuit was developed by Alan Blumlein, one of the leading audio designers during the 1950's and 1960s). Pentode tubes have additional control interfaces ("grids") that can be configured to allow more linear operations at high power levels; these additional grids are brought into play for "Ultralinear" operation (the "Ultralinear" output stage is one of the key aspects of the "Williamson" power-amplifier topology). It's fairly straightforward to insert a switch to reconfigure the output-tube to bypass the additional pentode grids and operate in triode mode. Many listeners prefer the sonic characteristics of triode vacuum-tubes, but the "Ultralinear" use of pentode vacuum-tubes provides higher power output levels and an alternative voicing of the power-amplifier. I noticed that all of the amplifiers that you have under consideration indicate that they include this capability (don't be confused by the use of alternative terms "ultralinear" and "pentode"; within the context of a "Williamson" circut, the terms essentially mean the same thing).

As to the issue of transformer quality; the more accurate the output transformer, the more intimately your speakers will be coupled with the sound produced by the power-amplifier. If the Yaqin has the better output transformers, then that would definitely be a strong point in favor of that product.

The reports of blown resistors is troubling as this indicates a circuit that is being operated too close to the limits of the component parts. Most likely, the affected parts are the resistors located between the output-tube cathodes and the electrical ground; the component value of these resistors is used to set the bias value of the output-tube. These resistors have to dissipate a few watts of heat (5-10 Watts) in normal operation; however, if an output tube develops a short-circuit (a tendency of low-cost KT88/6550 power tubes), the excess current will "blow" the cathode resistors if the resistor is only a 5-10W part. A better-built power-amplifier would use resistors rated for worst-case scenarios and probably have a 25-50-watt resistor (thereby allowing the main AC fuse to blow instead of the more-difficult-to-replace cathode resistor). The indication of this sort of inappropriate cost-cutting raises questions about the long-term viability of the product.

I understand the competing desires that you face; it can be quite entertaining to play "audio limbo" to see just "how low can you go?" on price and still get quality sound. On the other hand, the Yaqin MC-100B is certainly a very good-looking piece of audio gear (and, according to the importer, has the better output transformers). You'll just have to let your audio muse be your guide...

A very basic tube has two main inner parts. These are a cathode with a negative charge (that is, it has extra electrons) and an anode with a positive charge (that would like to take more electrons). The cathode is heated to help the electrons move from the cathode to the anode.

This flow of electrons is controlled by inserting a grid with a varying charge between the cathode and anode. This grid is cleverly called the control grid.

At this point we have a triode tube.

The tube types are named by the number of basic parts they have. A triode has a cathode, and anode and a control grid between them.

A tetrode tube adds one more grid, the screen grid. The screen grid provides isolation between the control grid and the anode. This decreases the capacitance between the control grid and the anode, and it increases the tube's gain.

A pentode adds suppressor grid between the anode and the screen grid. The suppressor grid collect the electrons that bounce off the anode instead of flowing through the anode.

Tetrodes and pentodes have more power (greater gain) than triodes, but the trade off is more distortion. Thus, the invention of ultralinear operation of these tubes.

My understanding is that ultralinear operation of a pentode or tetrode tube was invented by David Hafler and Herbert Keroes in the early '50's.

Ultralinear operation connects taps on the output transformer to the screen grids of the tubes. Driving the screens with part of the output signal lowers distortion.

To change a pentode operating in ultralinear mode to triode mode, the switch connects the screen grid to the anode with a resistor and diode between them.

The best way to start understanding tubes is to find some explanations with pictures. They are not as complicated as they initially appear.

(As a fun bit of info, the electron rays coming off of the cathode are called cathode rays. When these electrons strike a magnetized surface with a phosphorescent coating, such as in a TV, the coating glows. This is how the CRT of a TV or computer monitor works. Cool, huh?)

Yes. Good old TV. Staring down the barrel of a cathode ray gun. Literally.

Baird invented the system he used, in order to communicate inter-dimensionally with spirits.

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I really do like music, and I'm a big fan of old technology, and I want to get into tubes. I briefly looked at older power amps (The Dynaco Stereo 70 caught my eye), but the cost of a Dynaco, plus the preamp, plus the fact that I'll have to completely rebuild it with all new caps, sockets, and everything else... well, for that kind of money I can buy one of the sexy integrated Chinese tube amps listed on eBay.

I'll be the contrarian on this thread and suggest you stick with the Dynaco amplifier. Yes, you'll probably have to rebuild at least part of the amp, if you can find a stock ST70 or MKIII. They are both getting to be pretty rare in stock form. You can easily find a rebuilt, modified ST70 for a few hundred (or less) than you would pay for a stock unit. That amp would be ready to go into sevice the day you unboxed it.

Let's say you found a decent ST70/MKIII and wanted to rebuild it to your needs. There is no amp that I am aware of that has more options to the rebuild process. You can build this to almost any level of performance and still tear it down and start again tomorrow night on a new direction.

And you'll learn more about audio in general and tubes specifically than you will by ordering something from China. When you get done with the ST70 you'll know something (lot's of things probably) that you don't know today and never thought you would know. You will have joined the legions of hifi nuts who cut their audio teeth on a Dynaco product. That's a group that goes back over fifty years now and there's some very well known names who started their careers by soldering together a ST70 on their kitchen table at 2 AM. You wil have a stake in your system rather than just some cash invested.

The Dyna transformers are still one of the best around and far better than most. And with a tube amplifier transformers are the heart of the amplifier. None of the Chinese amplifiers can tell you what their transformers are about in a fashion that is really meaningful to you at this point. Build the Dyna and you'll learn what to look for in the transformer.

Let's say you buy one of the cheap Chinese amps. It breaks in a year. The entire Chinese supply of cheap electronics is based on a system that is non-sustainable. That company might not be in business a year from now. A lot of the tube companies from China that were hot a year ago are gone today. Tube amps aren't that difficult to service; but if you don't know how or can't find someone willing to be tied down to a discontinued amplifier from a non-existent company, you'll have a new paper weight to use.

The Dyna is obsolescence-proof. It's like buying a small block Chevy engine. There will always be the new tweak on a Dyna amp. And you'll learn how to fix an amplifier because you know how it goes together.

The positives for the Dyna as I see them are; 1) great amplifier that never will be out of fashion 2) knowledge gained 3) resale that does not diminish with time, in other words - free hifi 4) pride of ownership 5) everybody should own a ST70 at some time in their life.

Advantages to buying a new Chinese amp, 1) you get to contribute to China's economy.

Here's another clasic; http://buy.audiogon.com/cgia/cls.pl?ampstube&1204418131

Pair the El84 tubes with a single driver, full range Fostex. You won't see yourself coming down the street.

Here's a very stock ST70; http://buy.audiogon.com/cgia/cls.pl?ampstube&1203639368

Now I'm feeling bad that I sold my pair for $99@ two years ago.

Quote:

You will have joined the legions of hifi nuts who cut their audio teeth on a Dynaco product. That's a group that goes back over fifty years now and there's some very well known names who started their careers by soldering together a ST70 on their kitchen table at 2 AM.

And electrocuted by a 500VDC rail at 2:01 am.

Yes. A truly hands-on electronics guy has many more options available than a Chinese amp. All depends on how deeply one wishes to go down the rabbit hole.

Gentlemen,

Please; let's not overwhelm someone who just wants to enjoy the rewards of high-fidelity music reproduction by means of a new, ready-to-go vacuum-tube power-amplifier. Remember, this isn't DIYaudio, where the rabid audiophile/engineer rolls-their-own and/or hacks the living-daylights out of existing audio gear (personally, I partake of both worlds...). I've restrained myself to answering Charles' questions regarding the Ebay-sourced amplifiers that he is considering for purchase.

By the way, I love Dynaco vacuum-tube gear (I have my original PAS-3 preamplifier, Stereo-70 stereo power-amplifier and a pair Mark-III mono-block power-amplifiers, all constructed as Dyna-kits back in the late 1960's). However, for a high-fidelity newcomer, I don't think that I'd recommend either restoring a vintage Dynaco nor attempting to un-hack a previously modified Dynaco product (there's some pretty unsafe and downright-scary modifications floating around in those old chassis). I'd much rather send someone to http://dynakitparts.com, who offer complete kits for most of the Dynaco vacuum-tube power-amplifier products, using freshly-minted reproduction parts (chassis, transformers, etc.).

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Please; let's not overwhelm...

Excellent point!

I like both tubes and solid state (and switch amps somewhat regularly). I got a tube amplifier and tube amp initially for romantic reasons - I like the concept.

Tubes are confusing and a bit intimidating a first. As there are a lot of turnkey amps out there, just raring to make own happy this is a great way to start.

I hope my little tube tutorial didn't add too much to the intimidation factor. I'm one that likes to understand things and was very frustrated initially trying to understand how tubes work.

That site looks like they are offering new true-to-the-original amplifier kits. Do you have experience with their products? Since a huge chunk of the Dynaco performance came from their transformers, how are these units? They claim original specs but anyone can claim anything they want on paper. And these are basic Dynaco amps, right? There are no modifications to the original circuit? I liked my old ST70's but I wouldn't consider a stock ST70 to be competitive with today's amplifiers in many ways.

Elk,

Sharing knowledge about the technologies underlying our hobby is always helpful. As an engineer by training and avocation, I share your need to comprehend how we can harness technology in the service of music.

I just wanted to ensure that everyone kept the conversation within the context of a newcomer asking for help in evaluating his proposed choices for a brand-new, ready-to-go, vacuum-tube integrated amplifier.

Jan,

Yes, DynaKitParts is offering very high-quality reproduction Dynaco audio components in kit-form. Currently, they're offering complete kits for Dynaco Mark-IV's, Stereo-70's, Stereo-35's and Mark-III's (the Mark-III's are a fairly new addition). The only "modification" from the originals has been prompted by the unavailability of the 7199 vacuum-tube; DynaKitParts provides a low-profile 9-pin adaptor to enable the use of the 6GH8A vacuum-tube as a direct replacement.

I recently helped a buddy completely refurbish his Dynaco Mark-III's with new chassis, power transformers, output transformers and covers from DynaKitParts. As you noted, transformer quality is critical. We A/B'ed the sound of my friend's refurbished Dynaco Mark-III's (using the DynaKitParts power-transformers and output-transformers) with my original kit-built pair from the late 1960's and the power-amplifiers were aurally indistinguishable. Additionally, the fit-and-finish and silk-screening on the chassis were really nice (DynaKitParts claims that all of their reproduction Mark-III chassis are "fabricated from 18 gauge (non-magnetic) type 304 stainless steel, polished to a #8 mirror finish and followed by the application of a durable dark brown silkscreen. The lettering font, position and color are closely matched to the original.").

Another excellent source for Dynaco replacement power-transformers and output-transformers is Triode Electronics (http://triodestore.com/). These folks offer their DynaClone products, which I've used to help another buddy restore his Stereo-70. The DynaClone transformers were audibly identical to the originals.

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the power-amplifiers were aurally indistinguishable

I'm not knocking your amplifiers; like I said I loved my ST70's. But this implies the "new" amp sounds just like the old amp. While that's hardly a condemnation since there was a large dollop of magic in the original design, I would still place that sound more in the "classic" tube sound than in a contemporary vein. Does someone buy these new kits to relive the days of their youth? Like buying a boxed up '57 Belair? There are some very doubtful modifications that have come and gone for the Dynaco gear but I don't know that I would pay $675 for an amplifier that took me all the way back to 1959 unless I knew that what I was trying to find.

Jan,

I absolutely agree that the sound of the original Dynaco gear is quite "vintage" in nature. My Dynaco gear is kept for sentimental reasons; my current audio system uses custom-designed hybrid vacuum-tube/MOSFET circuits, combining Nelson Pass' SuperSymmetry and Aleph current-source topologies. I was simply using the Dynaco units as a point of comparision between the sound of the reproduction transformers and my original units. I'm most definitely not recommending the original Dynaco designs as the nadir of audio reproduction... ;-)

However, for those who might want to use these audio classics as a starting-point (including the wonderfully musical Dynaco transformers), both DynaKitParts and Triode Electronics can readily supply the "hard-points" for a number of currently-available designs that are based upon the key Dynaco elements (chassis, power-transformers, output-transformers, etc.).

The venerable audio-designer/modifier, Frank Van Alstine, is currently offering a complete rebuild of the Dynaco Stereo-70, replacing virtually the entire guts of the amplifier (with the exception of the chassis, and the transformers), all in an effort to deliver what Frank contends is an assault on the power-amplifier state-of-the-art. Frank also offers replacement of the input jacks and the output terminals with contemporary components to prevent the scraggly old jacks/terminals from impeding the performance. The URL is:

http://www.avahifi.com/root/equipment/amplifier/ultimate70.htm

Ron Welborne's company, Welborne Labs, also offers a massive upgrade kit for the Dynaco Stereo-70 (Ron is one of the key folks behind the origination of the Rocky Mountain Audio Fest). Ron's Stereo-70 upgrade also retains just the "hard-points" of the original product and essentially replaces everything else with a design authored by Alan Kimmel. The URL is:

http://welbornelabs.com/st70.htm

Of course, a discussion of Dynaco Stereo-70 modifications wouldn't be complete without mentioning Curcio Audio Engineering's offerings; the URL is

http://www.curcioaudio.com/dynadr_3.htm#DYNACO%20STEREO%2070%20POWER%20AMPLIFIER

The availability of these reproduction Dynaco parts (and complete kits for those who want to intimately understand what all of the fuss was about...) makes it much easier for music-lovers to experience these updated Dynaco-based products without having to resort to the oft-times very-used/abused Dynaco units available at auction. Instead, you can build one of these Dynaco-based wonders with all-new parts and a shiny new chassis.

In your opinion is it worth starting with one of these new kits for $675 only to then turn around and replace quite a few of the parts - other than transformers - with a modifier's product? What's really to gain other than cosmetics over buying an original stock ST70 if cosmetics are not that high on your list? For the most part the original Dyna transfomers seem to be holding up well despite being 40-50 years old. What are the pro's and con's of stock original vs new kit? Am I right that you can buy a new chromed chassis from these folks and it's a straight replacement for the original?

Jan,

Certainly, there wouldn't be any point in purchasing a complete Dynaco amplifier kit if your objective is to immediately go to one of the modifications; instead, you'd just buy the chassis, transformers and any other relevant bits-and-pieces, then add the modification kit. If you have the original Dynaco transformers in good working order, there's no need to buy replacements.

Deleted.

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