Opinions of Menno Vanderveen ( van der Veen ) PP Amps, Esp. Super-Triode

[DrDeville]

Greetings Fellow Tubaholics,

My name is George, and I have been tube-free for...
well, I *haven't* been tube-free. ; )

As further introduction--I am a relative newbie
looking for a DIY amplifier project of about 50WPC and
fantastic sound. By "fantastic", I mean those
subjective tube euphonics of openess,sweetness,
and holography.

As I have searched about, my eye has come upon
the designs of one Menno Vanderveen (or van der Veen ),
a proponent of new topologies and torroidal OPTs.

I am intrigued by his new PP designs, particularly
his Super-Triode, as described in this article on the plitron site.

This design uses both Ultralinear and cathode feedback,
and recommends SV6550C tetrodes.

As far as I can see, the potentially controversial aspects
are the new topology, and torroidal transformers. I
have no insight into the topology, but it seems to me
that the torroid offers extreme linearity and bandwidth,
at the expense of sensitivity to DC current saturation.
However, the design offers DC adjustment, so is it true
that this would not be a problem to the conscientious
tweaker?

What little comment I have heard on his designs
is positive, but I would like to get your advice
before I leap.

So I would greatly appreciate your opinions, insights
and preferences. Do you think this is an excellent
design? Why isn't it more popular? What DIY 50WPC
DIY design would you recommend to a builder seeking
excellent sonics?

Although this is my first post, I have enjoyed
reading your friendly and insightful posts. Thanks
in advance for your help.

Happy Tweaking and Listening!

George Ferguson

[tubetvr]

As far as I can see, the potentially controversial aspects are the new topology, and torroidal transformers.

What new topology, I can't see anything that hasn't been done before. In fact most topologies using tubes has been tried before and for the ones that hasn't been used much there is a very simple reason they dont produce a very good result, something to have in mind wjhen seeing a brand "new" tube based circuit. For the topology in this case it isn't new it has been tried before and you can ask why it hasn't been more successful?

What DIY 50WPC DIY design would you recommend to a builder seeking xcellent sonics?

I wouldn't, that is a wouldn't recommend any 50W amplifier but instead something simpler with lower output power. For 50W I probably would recommend to build something based on KT88 or 6550 in ultralinear coupling but not before the buillder had gathered a lot of experience building several other amplifiers and got an understanding how choice of components and circuit influence the end result. It doesn't matter how good the the concept is if the final result is not base on a thorough understanding how the circuit works in all detail.

Regards Hans

[DrDeville]

Hi Hans!

Thanks for taking the time to respond, and
share your insights.

For the topology in this case it isn't new it has been tried before and you can ask why it hasn't been more successful?

Yes, that's exactly the question I asked.
Vanderveen asserted that tube design
innovation was cut short by the advent of the transistor,
and its interesting to hear another point of view.

Can you name any ultralinear-with-cathode-feedback
designs, either DIY or commercial? It would be interesting
to compare the designs to Vanderveen's, and see what
people thought of them.

I wouldn't recommend any 50W amplifier but instead something simpler with lower output power.

I agree that would make things easier, but it is not
an option in this case--this amp will power some
inefficient speakers, and 50WPC is about the lowest
acceptible power. Otherwise I would gladly go SET.

For 50W I probably would recommend to build something based on KT88 or 6550 in ultralinear coupling

We're thinking along the same lines. What are
your favorites?

but not before the buillder had gathered a lot of experience building several other amplifiers and got an understanding how choice of components and circuit influence the end result. It doesn't matter how good the the concept is if the final result is not base on a thorough understanding how the circuit works in all detail.

That approach has its merits, though I would rather build
something that is actually useful to me, apart from the learning.

In my defense, I have sucessfully constructed a preamp project,
and am in the process of building a Marchand tube crossover.

Yes, in terms of design I am a Newbie, but have a technical background, and am studying.

Actually, I do not think that at this point I need a deep
understanding of components and topology, though I
certainly hope to learn. That's why I am asking for recommendations of a proven, great sounding design.

I've heard good things about Vanderveen's amps,
and am intrigued by their ability to educate me--the
design I referred to is configurable in 8 topologies,
which could be quite entertaining and instructive.

Also, the Ultimate KT88 design that Tone Loc mentioned
seems a very proven design, and could be instructional.

So can you Hans, or anyone else suggest a great sounding,
proven design of 50WPC or more?

Thanks for taking the time, and happy building
and listening!

Best,

George Ferguson

[fdegrove]

Hi,

Can you name any ultralinear-with-cathode-feedback

Well, it's not a big name brand but it has an excellent reputation amongst the " I don't care about AR, give me music" crowd. The name is Audiomat and in the Solfege amplifier they used both UL and CF feedback windings.
Maybe in some other models aswell, I am not sure....

So far, I've never, ever seen a DIY amp commercially available using CFB windings.
This is probably due to the fact that most of these kits use popular, off the shelf OPTs that are readlily available from the major winders.

In the range from 30 to 60 Watt the Quicksilvers are still hard to beat.
While it's not hard to copy as such, the endresult will be much dependent on the iron used.
With a little luck it could possibly surpass the original QS iron, who knows?

Has anyone tried yet?

Cheers,

[SY]

Can you name any ultralinear-with-cathode-feedback designs

I'll have to dig up Crowhurst's book to see if he showed it there, but I think he did. And I think that the Luxman 3045 might have used it, too.

Back in the late '70s, a popular mod for the Dynaco equipment was to use the secondary as a cathode feedback winding, like in the Audio Research pentode amps (cathodes connected to 16 ohm and common, 4 ohm tap grounded), but retaining the UL connection. Tertiary windings weren't really an option for the amateur in those days for lack of availability. But in any case, it was certainly UL-wit-cathode-feedback.

[DougL]

For What its worth, I have concerns with the circuit listed in an "super triode" configuration.

Simply stated, the "super triode" uses local feedback to obtain tube gain simular to an equivelent circuit using triodes rather than pentodes. Ok.

Triodes need AB2 in order to put out maximum power that the transformer / power supply / tubes can deliver. Since the "super triode" has simular gain, it would need simular drive.

The circuit is clearly AB1, due to the lack of direct coupled driver or interstage transformers that would allow for positive grid current.

Bottom line, I would not choose this design to copy unless you
are willing to live with 25 w or can re-design the amp for ab2 if necessary. However, within its limitations, it may sound wonderful. It just doesn't look like a mature design, more like an engineering concept to loosely follow.

Just my opinion, and I have not done the math.

Cheers;

Doug

[DrDeville]

the name is Audiomat and in the Solfege amplifier they used both UL and CF feedback windings

Hey Fdegrove,

Thanks for the tip!

I followed up on it, and it received at least one glowing review.
Here it is , in case someone is interested.

So far, I've never, ever seen a DIY amp commercially available using CFB windings. This is probably due to the fact that most of these kits use popular, off the shelf OPTs that are readlily available from the major winders.

I suspected as much, which is why I am intrigued by advances in technology that allow DIYers to build designs with components that weren't available off the shelf in the 50s.

Well, you may be have a treat in store, for a minor winder makes OPTs for these designs--Plitron in Canada, Amplimo in the Netherlands.

It's not an off-the-shelf kit, but
here are Plitron/Vanderveen's build instructions, and here
is one of the transformers the design can use. Note the
"Cathode feedback tap"

Amplimo sells the same OPTs in your neck of the woods, under different model numbers.

(Although I must look like a salesman for these products, I have no relationship with these companies. I am just an excitable geek. )

Thanks for the info Fdegrove. If you, or anyone else, happen to check out the Plitron or Amplimo site, I'd be very interested in your assessment.
By clicking the "site map" link on the Plitron site, one can see a bunch of articles on how to use these transformers.

Again, many thanks, and Happy Tweaking and Listening!

Best,

George Ferguson

[DrDeville]

For What its worth, I have concerns with the circuit listed in an "super triode" configuration.

Hey DougL,

Your concerns are very worthwhile to me, for it is "sanity checks" from experts (certainly more expert than me ) that I am seeking.

Triodes need AB2 in order to put out maximum power that the transformer / power supply / tubes can deliver. Since the "super triode" has simular gain, it would need simular drive.

Does it make any difference that, to my point of view, "Super-Triode" is something of a misnomer? It seems to me that the circuit in question is in fact a pentode in Ultralinear configuration, with cathode feedback? Does that ease your concerns in any way?

If not, what about the fact that this design can be reconfigured as a traditional Ultralinear (circuit 2)? It seems to me that, if the Super-Triode circuit does not work, as a fallback I could configure the amp as a traditional Ultralinear. Looking at circuit 2, are you comfortable with that design?

Thanks for your message, and for any other insights you can provide.

Best,

George Ferguson

[tubetvr]

I'll have to dig up Crowhurst's book to see if he showed it there, but I think he did. And I think that the Luxman 3045 might have used it, too.

The first time I saw this was in the Swedish DIY magazine "Populär Elektronik" from the early sixties where they described inventions and ideas together with DIY projects.

I am not very positive towards authors who claim that they invented something that was actually tried long before, it seems also to be common to invent a flashy new name together with the presentation of the new invention. There are quite many examples of these "inventors" around in the tube community today which is unfortunate because beginners can easily be tempted trying something that not only isn't new but has been rejected by many other designers earlier due to several valid reasons.

We're thinking along the same lines

No I dont think we are actually, I recommended to start with something easier then a 50W UL amp. Anyway as Frank says iron is very important, I would start from that end and then decide what amplifier to build. The circuit that Tone Loc mentioned seems to be very standard and unspectacular and could be a good starting point even if dont agree on some of the component choices, also as I live in Japan and have experience of Tango and Tamura transformers I would probably choose another transformer instead of the Plitron but that is my own personal choice.

Regards Hans

[DrDeville]

The circuit that Tone Loc mentioned seems to be very standard and unspectacular and could be a good starting point even if dont agree on some of the component choices

Thanks for crushing my unrealistic expectations.

Speaking only for myself, MV appeals to this newbie because he has a design he likes, and is willing to explain why he likes it and how to build it. I'd love to get similar information on a better 50+WPC design, but maybe that's another thread?

Best,

George Ferguson