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Tubelab Simple P-P

The following was posted last week by George in another thread regarding the Simple P-P. He's really swamped right now testing some IC's (or something like that) at his job.

The boards are scheduled to ship in about 2 weeks. Advanced has been known to ship early. I have a skeleton of the manual written but the time frame for completion is really up in the air.

The boards should arrive at about the same time we get our next pass IC chips back at work. The last chip led to 60+ hour work weeks for almost two months. If the boards arrive one weekend before the chips it could make a months difference in the time to get everything done.

I usually want to build at least one amp, and get a beginner to build one with the instruction manual before I start selling them. It really cuts down on the questions.

I already have two Simple P-P prototype boards up and running. I have not tried my usual mono block experiments with them yet. There are usually 3 ways to make a mono block out of a stereo amp. The eaisest way is simply to leave out one channel. I have done this with the Tubelab SE and the Simple SE, and I am sure that it would work on the Simple P-P. Another option is to parallel both channels for twice the power output. Some circuit changes could be used like wiring all 4 tubes up to one OPT. Another option is to use the amp as a two channel amp for bi-amping a single speaker.
 
Now that someone has started this thread I will post all updates here.

The chips arrived very early at work (10 days ago) which led to a panic to test all 900 of them. I have completed that. Now I am involved in the verification effort which requires a lot of time, but not like this week. If the boards showed up last Monday, they would still be unpacked.

The boards are ordered. They should be shipped next Friday (8-14) and in my hands early the next week. It is possible that they ship early.

I must then shoot all of the pictures for the manual which usually involves building two boards and one complete amp. The construction manual needs to be completed using the skeleton that I have already made from the Simple SE manual. The time for this is highly dependent on my work schedule. I then have at least one amp built by a third party "beta tester" to verify the manual. All or the parts for these three boards are on order and should be here before the boards.

Sherri has gone back up north to assist her mother, so I don't have the use of her organizational skills, but I have more free time. ;)

I am guessing that the Simple P-P goes live in about 3 or 4 weeks, but that is a guess since much of my time is beyond my control.
 
Has the layout changed since the prototype?

The general layout of all of the components is similar to that amp, but the board layout has changed. I moved several parts around to make assembly easier. I rerouted most of the traces to make the amp a little quieter.

I have a new prototype that exactly matches the board that was sent out for duplication. I will post a photo when I have some time at home. That's likely Saturday evening or Sunday morning.

If you need a true novice to do a build to test the manual I would be happy to volunteer.

I usually get Sherri to build one, but she is not here. I have already identified a local builder for Beta 1.
 
Picture of proto board.
 

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I'd be curious to know if you stuck with the LED's or not?

I did not make provisions for putting the LED's directly in the board. After some considerable testing I decided that it would not be a good idea for a board that is designed for beginners.

There is just too much variability in the voltage drop across LED's from the same lot, and the variability of tubes being sold as EL84's is even worse. The required cathode voltage is dependent on the power transformer, the line voltage, and to some extent the operating mode. There is no way to specify a set of parts that works in all conditions. I have found that a set of LED's that works with one set of tubes will lead to red plate death with another set.

I will explain how to make the modifications to an amp after it is up and running. You need to measure the cathode voltage on your set of tubes after they are well broken in using the existing cathode resistors. Then select a combination of LED's that adds up to the same voltage and install them in place of the cathode resistor. You must do this for each tube. This is the only way it will work without adding bias adjustments to the board. That defeats the "Simple" part. Most builders will not do this, so this feature was left off of the board to avoid unnecessary complexity.

This will be explained in further detail after the basic manual is finished.
 
As with my SE amplifier projects there will be at least two. There must be a "Simple" version that you just build, plug in, and listen. It needs to appeal to the widest possible DIY audience. That is what this amp is for. It uses the EL84 / 6BQ5 tube, and produces from 10 to 20 watts per channel. This board is slightly larger than the Simple SE or the Tubelab SE.

It is possible to design a P-P amp using octal tubes that is all on one PC board but the board would be rather large. Most PC board vendors have a non linear price per square inch charge that starts to turn upward rather quickly at around the size of these designs. This is because the boards are made in large panels and then cut up. The scrap costs go up as the board size increases. I decided that bigger amps would need to be built in a modular fashion.

There is another P-P amp being designed in a thread on this forum. It is a single channel driver board using a pair of 6SN7's. it started out as a paper design to drive 6L6 type tubes in class A, AB1 or AB2 using PowerDrive. It evolved into a working driver board. I made sure that the board had the capability for driving all sorts of wierd tubes and I have been using it for just that. The sound quality has been stunning, and I am already making an amp using the pair of boards that I made. Email response has indicated that there is a demand for these, and I can already see that I could use a few, so I will likely get some made. This is definitely not a "build, plug, and play" solution though.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=133034
 
Just curious, did you get your boards yet?

The original supplier that I ordered the boards from decided to raise the price once they received the gerber data because the boards were too big to use their standard process. Their prices for Simple SE boards have increased 30% in the past 3 years already. I decided to change vendors for this board, and possibly the Simple SE on the next batch. They will be supplied by another US board house that I have been using for the Tubelab SE boards.

The ship date for the boards was last Thursday. I have not received them yet. Their web site "order tracking" is useless since it still shows orders from 2005 as "not shipped". I have sent an email asking for order status that has not been answered yet. Past experience has shown that I will get an email reply after I get the boards.

I will post a picture of a shiny new board as soon as I have them.

I'm guessing a PowerDrive board of that sort would be quite a way off production?

It is a safe bet that they won't be available real soon. I have two working prototype boards that are currently mounted in a "breadboard amplifier" to evaluate several different output tube / transformer combinations. This amplifier will be chronicled in the 6L6GC in AB2 thread mentioned previously since that is where it started, and the 6L6GC is still a valid output tube choice. I have found my UTC LS-57 OPT's so that combination will be tested.

The time frame for commercial duplication depends on a lot of things. The two biggest ones are, the time that I have available for Tubelab related activities (largely beyond my control), and the funds available (this will be determined by the success of the Simple P-P).

I have gerber files ready for the board as it exists now, and I may get a small batch made if the test amp works like I think it will. I can see myself building a few amps using them. I have tested a bunch of different tube / transformer combinations in glorious mono using the one working board that I had, and I heard a few "magic sounding" combinations. I have since made a second board.
 
Can we preorder?????

I prefer not to accept orders for something that is not ready for sale yet. I really have a hard time assessing the time that I will have to devote to creating the manual, since my work schedule varies on a daily basis. Sherri has been away for 3 weeks and she is returning on Friday. She will be here from 1 to 3 weeks, and I must go with her on the next trip. I will be away for 7 to 10 days. I am usually stuck at work for 60 hour weeks when I return from a trip.

I will attempt to get the manual ready before I leave, but Sherri may have other plans (isn't that how marriage works?). I take boards and my laptop with me and ship from the closest post office, where ever I may roam (where have I heard those words before?).

110 boards will not dissapear quickly so there is no need to panic, and I can always get more. Lately board sales have been 1 to 2 per week. The Simple SE did 3 to 5 per week when it was first introduced, but the economy was much better then.