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Old 26th August 2009, 06:18 PM   #21
adwsail is offline adwsail  United States
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Thumbs up pp boards

Outstanding!!! I've been waiting to build a PP amp since I built the Tubelab SE about 3 years ago. It is still my favorite amp despite blowing it up once by the unfortunate richocet of a resistor lead from another project. Count me in on a board, simple or not is no problem as long as I've got a good schematic. Building a new design without verifying the board/schematic is asking for trouble anyway.

Whenever you have a price and want to let the cat out just let us know!!!!
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Old 26th August 2009, 06:25 PM   #22
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Whenever you have a price and want to let the cat out just let us know!!!!
Despite being slightly larger and slightly more expensive than the other boards, I plan to keep the same price, $35. I still get emails asking why they are so expensive, they are just 2 layer boards. I tried explaining the concept of recovering the development costs, but i realized that these people just want to whine.

Tubelab has never made any money, but at least last year, and likely this year, it didn't LOSE any money. That works for me....at least as long as I have a job.
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Old 26th August 2009, 06:33 PM   #23
adwsail is offline adwsail  United States
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Paypal should be notifying you soon. Thanks a bunch. Offhand, is there a current schematic you recommend following for the construction? I totally understand the issues with the leds... not very "tight" in there construction but once that is accepted it's a simply matter of matching led's to R values that are working. Looking forward to it!!
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Old 27th August 2009, 03:34 AM   #24
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I'm waiting for the Tubelab screen drive sweep tube amp to appear. So much talk about them, but still no product on the market...
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Old 27th August 2009, 05:07 AM   #25
DougL is offline DougL  United States
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I'm waiting for the Tubelab screen drive sweep tube amp to appear.
Since this is a work in progress, here is a starting place for you.
http://www.tubelab.com/6AV5.htm
At the bottom of the page is the Screen Drive schematic.
While it may not be ready for a circuit board, its certainly good enough to DIY.
Let us know what you find.

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Last edited by DougL; 27th August 2009 at 05:15 AM.
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Old 27th August 2009, 03:40 PM   #26
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I'm waiting for the Tubelab screen drive sweep tube amp to appear. So much talk about them, but still no product on the market...
In order to avoid going broke I must design what the readers want (based on email and forum response). Since the Simple SE was introduced the overwhelming request was for a P-P version. "Something that would blow those S5 kits away". OK, that one is near completion. Close behind that in email requests is for a BIGGER Simple P-P. As with most things in life "bigger" and "Simple" don't always work well together. I have laid out a PC board for a "bigger" Simple SE using octal output tubes. The board for a complete two channel amplifier becomes too big for economical fabrication and the thermal issues would compromize the reliability. So it seems that anything bigger than the Simple SE or the Simple P-P really needs to be broken up into multiple boards or "modules". What does "modular design" have to do with screen drive? A lot.

Screen driven amplifiers have never been main stream. They generally require sweep tubes. You can buy a 6SN7 or a 6L6GC anywhere in the world. You can not find the 6AV5 or many other popular sweep tubes outside the USA. The sweep tubes found in Europe or Australia are different than the ones common in the US. This means that the market for a dedicated screen drive amplifier is small and fractured. A PC board for a screen driven 6AV5 amp would likely not be capable of recovering the development costs. So, how do we get a screen drive amp?

Since it has been determined that we need to go "modular" we will need a driver module, an output module, and a power supply. Since it would be impractical to design a new board for every type of amplifier that I (or you the readers) can imagine, I am changing direction a bit here.

There will be one or two "universal drivers" that should be capable of driving nearly any tube out there. One design is nearly done, and the other is in the second working prototype stage. The first is the octal driver board that developed in the 6L6GC in AB2 thread:

6L6GC AB2 Amp

This board is a response to the many requests that I get to use all octal tubes. It is also capable of driving just about anything including the screens of a 6AV5. The mosfet PowerDrive is on the board. I have breadboarded several mono amplifiers using one of these boards. I have built a two channel test amp using two of these boards, and two "output modules" made with dual octal turret boards. The purpose here is to test and verify a big bunch of tube / OPT combinations, using conventional and screen drive. A spreadsheet will be created to gather power supply requirements and record the results.

There is another driver board in the works that got started in the "universal driver" thread:

"universal" P-P driver board

This one uses 9 pin miniature tubes and has the option of eliminating the direct coupling between the first and second stages to allow for a higher output swing for a given B+ voltage. A few single channel test amps have been breadboarded including screen driven sweep tubes.

There will be one or two power supply boards that are somewhat universal in nature. These have not been designed yet. Before anything can be designed, I need to figure out what is needed to satisfy the largest variety of amplifier designs without compromize.

The output modules for most amplifiers are really simple. Mine have a pair of 10 ohm resistors for cathode current measurements and a bunch of jumpers to allow the use of a variety of tubes. Since the majority of the components are on the driver and power supply modules, the output modules are not really even needed. I envision one for use with the common audio tubes (for convienience), and one with multiple PowerDrive circuits on board for use with dual drive (screen and control grid driven independently). More on this later!

Based on email, I assume that 90% of readers want an amplifier that can "stomp an ST70" using all octal tubes that is compatible with the commonly available Dynaco (or Dynaclone) iron. This is likely the next target after the Simple P-P. This means that the octal driver board gets done next, followed by a power supply board for this type of amplifier, and a simple output board for 2 or 4 octal tubes.

There is nothing to prevent using these same modules to do a screen driven amplifier, in fact I will do that and publish the schematic.
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Old 27th August 2009, 03:50 PM   #27
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If anyone wants to balk at $35.00 for a well researched printed circuit board that is a proven design, they need to design their own amplifiers. Your time and efforts are worth a considerable amount. I could not ask anyone to do something for free or for that matter for no gain. You have every right to ask for some compensation for the use of your brain, your time and your creativity.
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Old 27th August 2009, 04:39 PM   #28
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Originally Posted by Curly Woods View Post
...they need to design their own amplifiers.
No doubt. I have a talent for smoking anything solid state, and can botch even a simple tube design. I don't consider myself a noob anymore, but there's a lot I don't know. Troubleshooting sometimes requires expensive test equipment and the skill to use them effectively, and I've got neither. $35 is a bargin.
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Old 27th August 2009, 05:08 PM   #29
w5jag is offline w5jag  United States
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George,

The Simple P-P sounds like fun. Will you post here when you are ready to take orders for the board? And have you tried it with 6CW5?

That universal driver board also sounds great. I would think that power supplies and output tubes could pretty easily be wired point to point, even by beginners.

Win W5JAG
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Old 27th August 2009, 05:13 PM   #30
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I agree, $35 for a proven board is amazingly affordable. That kind of pricing, along with George's extreme helpfulness is a boon to amateur builder like myself.

i can't wait to be able to place my order, collect all the parts, and get building!
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