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!!!!
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!!!!
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.
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!!
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.
Last edited:
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:
http://www.diyaudio.com/forums/showthread.php?t=133034
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:
http://www.diyaudio.com/forums/showthread.php?t=137063&highlight=universal+driver+board+tubelab
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.
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.
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.
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
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
Yes, I have a box full of 6CW5's from all of those HP audio oscillators that I parted out. They work fine, but must be operated at a lower B+ voltage than a 6BQ5/EL84. They seem to prefer a 3K ohm OPT too. I have also used some 7189A's that can be cranked harder than an EL84. I will have data with all 3 tube types in the manual.
I am still finalizing the parts list. I haven't finished the testing with all 3 tube types. It may be possible that some resistor values will depend on which tube is used.
The output tubes, yes. The power supply requires two positive voltages and a negative voltage. All of my amp development is done using regulated bench supplies, although none of them are in particularly great shape. One of the reasons for the test amp that I just built is to find out if regulation is required or advantageous for any of the supplies, and what voltages work best for a given tube and load impedance.
They don't even need to design their own. My schematics are on the web site, and people have built their own. I have no problem with that. There are still people that believe a PC board will mysteriously suck the life out of the sound. If they want, and are capable of building one of my designs PTP, go for it. It can be done with the Simple SE. There are at least two builders that have done a Tubelab SE using PTP construction. Heck, I wouldn't even try that myself.
All of the funds collected from selling PC boards goes into paying for the experiments that I do, and the development of more stuff, including more boards. I have not done a good job getting all of my experiments posted on the web site but most of them have been posted on the forum.
It is interesting that one of the whiners that refused to pay $35 for "something that he could do himself" had the nerve to email me a few months later complaining that the design was a POS since his amp hummed. I didn't answer him.
If I saved all of the sand based life forms that I have killed over the years I could easilly fill a garbage can. Any SS device connected directly to the power lines or a car battery can really go bang. Often there is only a black stain on the PC board where a chip or mosfet used to be.
I usually keep pretty quiet, but I must say George, I love your work and all you have done and I cant wait for the P-P boards to go on sale! I myself would love to try something with some screen drive, some day.
Some people are NEVER happy no matter what! Please dont let this kind of crap discourage you in any way because most of us like your work and the efforts you have put in, especially with all what is going on in your life right now! Thanks
Some people are NEVER happy no matter what! Please dont let this kind of crap discourage you in any way because most of us like your work and the efforts you have put in, especially with all what is going on in your life right now! Thanks
As my Dad was fond of saying about folks that liked to bitch all the time "They would bitch I they were hung with a new rope". Rest well old fella, you are missed by many
It doesn't, I posted this because it was the worst case of whining that I have received. In reality most (99%) of the email that I get is very positive. I can't possibly have the time to answer it all, but I try. Last night I got home late and spent the entire evening answering email even though there is a half finished Simple P-P board on my bench calling my name. I tried to explain the reason that a board cost $35 to him in response to his first email. I even mentioned that I spend considerable effort chasing hum so that the builder won't have to. Then when I got his second email, I just laughed.
My life has returned to almost normal after nearly 2 years of no amp building and very little experimentation. There are rumors of another round of layoffs at work. If I get past that one, things will be OK and all of the stuff that I outlined previously will happen.
This thread is good news! I love my Simple SE and have been waiting for the Simple PP. I was thinking of putting together a Buffalo 32 DAC after I finish building my Aleph-J. However, I think the DAC may be getting pushed back so I can build a simple PP instead, hehe.
Thanks for all your had work George, and if anything, $35 is too cheap for one of these boards.
Thanks for all your had work George, and if anything, $35 is too cheap for one of these boards.
Hello George,
Stop worrying about the complainers, they will never be satisfied. $35 for a well engineer board is a bargain indeed. Your effort and support for your products speaks for themselves. I just finished my 3rd Tubelab amp and very happy with them. It was a dream of mine to own an EL-84 based amp. I tried different Scotts but not satisfied with their sonic coloration and sold them all. Your PP amp is the ticket I reckon. Godspeed, Sir.
John Revilla M.D.
Stop worrying about the complainers, they will never be satisfied. $35 for a well engineer board is a bargain indeed. Your effort and support for your products speaks for themselves. I just finished my 3rd Tubelab amp and very happy with them. It was a dream of mine to own an EL-84 based amp. I tried different Scotts but not satisfied with their sonic coloration and sold them all. Your PP amp is the ticket I reckon. Godspeed, Sir.
John Revilla M.D.
Well, Sherri got back into town yesterday after being gone 3 weeks. We had lots of stuff to do, but I still managed to "light one up". I can see several configurations for this amp, and like the Simple SE, I expect that most people will want the biggest power transformer to get the most output power. There have been several requests for a minimalist configuration, the best amp for the absolute least money. Since that was the first set of transformers that I came up with when I started scrounging, that is what I built.
I have an Allied 6K56VG power transformer and two Edcor XPP10-8-8K OPT's. The output tubes are some Russian 6P14P tubes that were $3.50 each on Ebay including shipping from the Ukraine. I have not had any time to optimize anything, so the board is as built. I am getting 10 WPC in UL mode at 3% distortion. Triode or pentode have not been tested yet. I am drawing a bit too much B+ current from the transformer, but it has been running at full power for 2 hours. The power transformer is cooler than the one in my Simple SE and the hot smell turned out to be the dummy load resistors. I found that many 8BQ5's work just fine since Hammond transformers supply nearly 7 volts on their filaments. These can often be found cheap.
I plan to do some more testing with different tube / transformer combinations. I don't think that these tubes can deal with high voltages, but I have some 7189A's to try. I will also test 6CW5's, they run at much lower voltages, but can be made to crank out some power too.
I have an Allied 6K56VG power transformer and two Edcor XPP10-8-8K OPT's. The output tubes are some Russian 6P14P tubes that were $3.50 each on Ebay including shipping from the Ukraine. I have not had any time to optimize anything, so the board is as built. I am getting 10 WPC in UL mode at 3% distortion. Triode or pentode have not been tested yet. I am drawing a bit too much B+ current from the transformer, but it has been running at full power for 2 hours. The power transformer is cooler than the one in my Simple SE and the hot smell turned out to be the dummy load resistors. I found that many 8BQ5's work just fine since Hammond transformers supply nearly 7 volts on their filaments. These can often be found cheap.
I plan to do some more testing with different tube / transformer combinations. I don't think that these tubes can deal with high voltages, but I have some 7189A's to try. I will also test 6CW5's, they run at much lower voltages, but can be made to crank out some power too.
Attachments
What's the driver tube on these guys? 12AT7? Is the schematic up on your site?
I'm intrigued that you opted to use a choke in the power supply on these. I'd assume that given the "absolute least money" directive, it would be the first thing to go. Sure, on a single ended amp it makes a big difference, but in push/pull doesn't a lot of the residual PSU hum tend to cancel out in the finals?
I'm intrigued that you opted to use a choke in the power supply on these. I'd assume that given the "absolute least money" directive, it would be the first thing to go. Sure, on a single ended amp it makes a big difference, but in push/pull doesn't a lot of the residual PSU hum tend to cancel out in the finals?
The schematic, or any new information related to the Simple P-P has not been posted yet. For now all that I have is the Eagle schematic which only shows the board mounted components. The driver tube is a 12AT7.
There is a resistor on the board with the two terminals to use a choke if you want. When I saw that a 150 ohm resistor was costing me 30 volts, I dug up a cheap choke with a 50 ohm DCR. I picked up 1 watt of power.
I wired it up in pentode mode, and applied about 5db of feedback. power was 12 WPC. Distortion at 1W is 0.17%. Power output below 50Hz was limited by transformer saturation.
I connected a CD player and speakers. It sounds very good, some saturation was heard on Money for Nothing, but if you stayed away from the saturation, the bass wag pretty good.
The sound quality was good, and easy to listen to. It will not strike fear ino the 75WPC all triode monster that I have been working on.
There is a resistor on the board with the two terminals to use a choke if you want. When I saw that a 150 ohm resistor was costing me 30 volts, I dug up a cheap choke with a 50 ohm DCR. I picked up 1 watt of power.
I wired it up in pentode mode, and applied about 5db of feedback. power was 12 WPC. Distortion at 1W is 0.17%. Power output below 50Hz was limited by transformer saturation.
I connected a CD player and speakers. It sounds very good, some saturation was heard on Money for Nothing, but if you stayed away from the saturation, the bass wag pretty good.
The sound quality was good, and easy to listen to. It will not strike fear ino the 75WPC all triode monster that I have been working on.