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looking for ultralinear push-pull project

TJ

Member
2001-09-05 1:54 pm
MALAYSIA
Hi, designing a 30- 40w class A tube amplifier is not a good idea ! wasting ur tube life ! most tube amplifier working on class AB . Class A doesn't meant good sound ! i don't think u can find a GOOD tube simulation software ..... b'coz tube design is not complicated like transistor !
 
re:ultralinear push-pull

The Svetlana looks interesting in theory...except I can't get a good look at that schematic, it's too tiny (and it's not a link, unfortunately ).:confused:
As far as software goes...I recently ordered a copy of TubeCad--
it seems like it may be nice to work with on PP designs. Anyone have any experience with this?
TJ, your point about 30-40W in Class A is interesting. I hadn't really thought about it from that aspect. I may just have to look into going AB instead of A...or at least compare them head to head.

Thanks for the replies

Matt
 
Look at www.amplimo.nl (dutch site) for the UL40-S2 designed by Menno Vanderveen, or look at www.plitron.com
The UL40-S2 has an ultralnineair schematic. standard with svetlana 6n1p/EL34. I build it with Svetlana KT88's.
It has a lot of class A power and sounds great. A lot better than the Audio Innovations series 500 i had before...
If you need the schematic, let me know..

Greetings,
Tube Addict
 
I have a copy of the TubeCAD software. It is very educational and interesting. There are some very nice features and the interface is very intuative. It has interactive plate curves for lots of tubes types. It calculates things like output impedence. It evaluates your circuit for exceeding the tubes ratings, makes suggestions, and will even fix up your circuit automatically.

It is different from traditional SPICE programs. In SPICE you draw the schematic. Define paramters, component values, power supply values etc. Then you run the simulation and get the different results.

TubeCAD comes with about 48 pre-drawn schematics. You cannot change the schematic. This is fine because there is such a wide range of schematics to choose from.

The problem I do have with the program is, there are too many user defined variables. You have to define resistor values, power supply voltages and (idle?) current. The current is what throws me off.

I have never been able to get my head around that. With Ohm's and Watt's laws, once you have established any 2 of the four parameters, (voltage, resistance, current and power) the other 2 can be calculated.

Maybe some out on the forum can explain this to me?

What would work best for me: Specify resistor values and power supplies and then let the program calculate the currents and power dissipated.

Then I can tweek the values to get the power and current levels where I want them. I have contacted John at TubeCAD to get an explaination on how to deal with this. Never got a response that addressed my confusion. The answer may be obvious some one who understands tubes (and math) more than myself.

They also have a very interesting on-line magazine.

http://www.tubecad.com/

It is still a very good deal, I am never sorry I purchased it. John, the guy who writes the software and the magazine deserves your support.

Aud_Mot
 
I blew up the schematic for the Svstlana and took a look. Check out the Dynaco MarkIII(3). Looks to be very close. The smallest Allen Organ amps use a PP UL 6L6 with a 12AY7 for low harmonics and high gain. I understand that the larger amps built for the tone cabinets used 4 6550s per channel/amp getting you up into the 100 watt range and I am presuming using the UL style of circuit. The Allen Organ people will gladly send you a hard copy of their amp schematics. That is how I got the one for the 20 watt 6L6.
 
Matt,

maybe you look at Antique Electronics Supply, they sell an article reprint of the original Williamson amplifier.

If you happen to find a pair of Acrosound TO300 output transformers, you can use this together with the Williamson circuit for either triode or ultralinear configuration -- it sounds magic.

If you settle on that, email me, i might have some schematics of the Heathkit WM-4 which used this trannie and KT66 as output tube. 6L6GC also is a possible tube.
 
Transformer maker Plitron at

http://www.plitron.com/

has an excellent book about output transformers in general, plus their own toroid transformers. The book also goes beyomd just transformers and output stages. They even have a PCB available

Bruce Rozenblit's excellent book Beginners Guide to Tube Audio is also an excellent resource.

Once you have those under your belt, you would not have so much need for existing schematics.

Once you have the output stage defined, you just need figure out how much gain (and feedback, one affects the other) and method of splitting the phase.

With education will come the flexibilty to use transformers you can get your hands on, instead of looking for the exotic and expensive model specified in some schematic. There is lots of old tube equipment out there, with excellent transformers in them, just waiting to be dusted off and put to use.

If you can get your hands on an old Dyna Stereo 70 with all 3 transformers usable, you would have a good start.

Good luck and let us know what you end up with.
 
re:amp

Hey everybody--
Thanks so much for your responses...I'm very impressed with how friendly everyone here seems to be.
The book by Bruce Rosenblitz caught my eye awhile back, I'm
definitely looking at picking that up. I'd really love to get into the
design end of things--the part that's got me really stumped at the moment is calculating how much feedback I need. Any suggestions on that end?
For Luis MCP--I've got Pspice, but I haven't seen any models for tubes and transformers. Is there a place that I can download something of this nature? Can you import designs from TubeCad to Pspice? Which do you prefer in terms of simulation?

Matt
 
RE: amp

mnewport wrote:
Hey everybody--
Thanks so much for your responses...I'm very impressed with how friendly everyone here seems to be.
The book by Bruce Rosenblitz caught my eye awhile back, I'm
definitely looking at picking that up. I'd really love to get into the
design end of things--the part that's got me really stumped at the moment is calculating how much feedback I need. Any suggestions on that end?

My opinion is apply NFB to minimize THD% at negligible levels. This is for PP topologies. In SE topologies, THD% is more benign, higher armonics are lower.


For Luis MCP--I've got Pspice, but I haven't seen any models for tubes and transformers. Is there a place that I can download something of this nature? Can you import designs from TubeCad to Pspice? Which do you prefer in terms of simulation?

Many models of tubes in http://www.duncanamps.com/spice.html
Transformers are easy to modelize, I have got my own of Ultra Linear, Single Ended and Push-Pull types of many impedances.
I don't know how to import from TubeCAD to Pspice.
Pspice is fine for simulating small power tubes. SECAD is better to me, for power tubes. Pspice is more flexible.

Luis



Matt
 
I got on line and found the Allen Organ co and wrote a Email saying I needed a schematic for the 20 watt 6L6 amp and it was mailed from the closest dealer with a lot of ' How can we be of service' type stuff. Best customer service I have had in years. It should be possible if worded right to get all the schematics for the tube gear they made. And if you are interested in the 6L6 PP you should be able to get a pair for $300 t0 $400 on Ebay depending on how badly the other guy wants them. From what I understand the OPTs are exact copies of the Triad 300 Ultralinear ( if I have that right ) that went into the W3 Heaths. A pair of Allens will cost close to the same as a pair of the OPTs of W3s. I hope this is a help. I just got rid of a Dyna Mark III and the Allens could beat it all to hell and back.
 

Denis

Member
2001-10-13 2:25 pm
mnewport said:
I've been trying to find schematics for an ultralinear pushpull
amplifier that puts out roughly 30-40 watts in class A...I haven't had much luck finding one. Any suggestions?
Also, any recommendations for simulation software for tube circuits?

Such amount of class A power is quite a hard Job for most known power pentodes. 30W class A UL amp could be built with a pair of 6550 tubes.
Indeed, the most powerful and efficient power pentode is EL509.
A pair of these tubes can easely deliver about 40W of class A power, and moreover, the power will continuously increase with lower load resistance due to great reserve of output power.
Indeed, the use of conventional UL output transformer with screen taps will be unappropriate, because thses tubes require the Eg2 much lower than Ep. There is more efficient and versatile solution, the cathode feedback or distributed load circuit in which the small part of the primary winding is connected to the cathodes providing local voltage feedback. Such circuit topology can give ultimate results with any pentode and with either PP or SE, because one can freely choose the screen voltage, and the local NFB introduced this way is enough effective to get the same or even lower Ri than that for these same tubes triode connected, and the driver voltage will be still within reasonable limits. Also the proper choise of Eg2 makes it possible to alter the harmonic distortion spectrum in such a way that the high-order harmonics will be almost totally cancelled for the most part of the dynamic range, and the amplifier will behave much the same with different lads and when leaving the class A current range.
The historically first use of such topology seems the Quad II amplifier.
You can find more on the performance of CFB PP ampliers with EL509s at www.cortmi.com.ua/omak
 
Tube Addict said:
Look at www.amplimo.nl (dutch site) for the UL40-S2 designed by Menno Vanderveen, or look at www.plitron.com
The UL40-S2 has an ultralnineair schematic. standard with svetlana 6n1p/EL34. I build it with Svetlana KT88's.
It has a lot of class A power and sounds great. A lot better than the Audio Innovations series 500 i had before...
If you need the schematic, let me know..

Greetings,
Tube Addict

Hello Tube Addict,

I'm looking for the schematic of the UL40-S2.

Kind regards,

Marc
 

JDeV

Member
2002-10-19 7:51 pm
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