You can just use a jig and a router, unless you are a purist demanding dovetails carved with a hammer and chisels.
Yes, I did notice that. This "Thomas" amp I am referring to (from a Thomas "Talking Organ" I received as a child) is a similar circuit also (12AX7 gain + 12AU7 split load phase splitter + pair of 6V6GTs per channel). I've often thought of improving the circuit, since it seems to be optimized for tube life, but the output transformers are *tiny* and probably would need to also be replaced to make it worth the effort. GNFB lets the amp perform reasonably until it starts to clip. Then it breaks up pretty quick for reasons you've mentioned to me before.
All that said, there is a pretty good chance that I will be ordering one of your PCBs...especially if you are selling them as kits with all the PCB components (which it sounds like you are?). I may not build it anytime soon as I don't know how the wife will deal with yet another tube amp sitting around the house.
I guess there is some airflow through this chassis...the tubes are recessed so some air can move out of the chassis between the PCB guard and the top plate. But I also made a point of sinking any hot components that I could. Still, the TSE puts out a lot more heat just being on the bread board than the SSE ever did.
I never got around to making a bottom cover (perforated aluminum on the new Simple P-P amp) or putting any feet on the chassis so the side rails sit right on the wooden bench top. No air can go in, so none can come out. The top plate gets almost too hot to touch and the power transformer does get too hot to touch. I am almost afraid to see what it looks like under there.
That is the plan. Sherri is putting together the "bag o parts" for the Simple P-P boards. After the credit card recovers we will do the same for the Simple SE.
Does a guy who calls his company Tubelab but sprinkles sand in many amps sound like a purist? We had a dovetailing jig in the old classroom, but not in the new one. I never had the time to play with it, but I did watch it being used by an experienced user.
The transformer is still in the box, unopened. Unfortunately I have been stuck at work late every day (8:14 PM last night) and on a 7 day work week. Broke a tooth last weekend (split down the middle!) which requires a root canal this afternoon followed by more dental surgery. This puts me further behind (not good in this environment) at work so my schedule for the rest of the year is very uncertain.
I have mentioned the results of my testing in several posts in this thread, but I don't have anything summarized in one place yet.
I have big changes planned for the Tubelab web site and information related to Tubelab in general. I get more email than I can possibly answer and lately I have spent more of my time (which is very limited right now) answering email than working on the Simple P-P manual. Often I get the same questions from 5 different people (usually asking if I have boards in stock, and how to get one). In order to make this easier for everyone I have decided to try a one year experiment. There will be a Tubelab forum on diyAudio for support and general information. Most of the Tubelab related threads will be moved there. I am paying for this in advance for one year, and I will decide after a year if it is worth it. It is already there, I just don't have the time to set it up now. I will also add a limited shopping cart to my web site early next year. If these two additional expenses allow me the time to actually play with tubes again, it will be a success.
I parted out the amplifier from an old Baldwin organ last weekend. I saved the iron and the tubes. The organ was bought new by a church in 1962. It was used until it was deemed beyond economical repair. The amp was removed and used as a PA system. It was replaced by a solid state amp about 2 years ago and given to me. So this amp was used for at least 3 hours a week for 45 years. It contained 8 6BQ5 tubes and 7 were the original Baldwin branded Sylvanias.
Today I decided to see if there was any life left in those old tubes. I plugged them into a Simple P-P board and cranked up the juice. Does 30 WPC at 2% distortion running on 420 volts without exploding sound like there is any life left? I got this idea to run the amp as a single channel mono block using 4 6BQ5's. OK i got 62 watts out of it at 3.7% distortion. I don't have any new tubes that can do this. I guess that the old Sylvanias rock.
The first attempt ended badly for one of the 6CW5's. The screen grid lit up and then the lightning started jumping around inside the tube. The B+ was about 310 volts, too high for a 6CW5. I don't have time to figure it out tonight. It is 11PM here and I gotta be at work by 8.
Today I decided to see if there was any life left in those old tubes. I plugged them into a Simple P-P board and cranked up the juice. Does 30 WPC at 2% distortion running on 420 volts without exploding sound like there is any life left? I got this idea to run the amp as a single channel mono block using 4 6BQ5's. OK i got 62 watts out of it at 3.7% distortion. I don't have any new tubes that can do this. I guess that the old Sylvanias rock.
The first attempt ended badly for one of the 6CW5's. The screen grid lit up and then the lightning started jumping around inside the tube. The B+ was about 310 volts, too high for a 6CW5. I don't have time to figure it out tonight. It is 11PM here and I gotta be at work by 8.
Attachments
I believe the boards are all good and ready to order, but the "bag o parts" won't be for some time (currently George is working 12 hour days to keep his job).
Maybe not quite yet
I think George is still testing
And he said nothing will happen untill MANUAL is written and approved
And George obviously is a very careful man, and like to have fun and blow up some amps before releasing
Can anyone shed some light?
Copied from the Tubelab forum:
I know this amp isn't even out yet, but for those that understand this stuff a lot better than I do, how hard would it be to mod this amp to accept 6922 (and associated tubes) in the driver slot?
I've got quite the collection of these tubes, including the Russian variants (6H23-EV, 6N1P-EV) as well as several 6922's, 6DJ8's, and some 6FQ7's. I know these are not all exactly the same, but many designs allow them to be used interchangeably. Would it be a nightmare to get the Simple P-P to play nice with these tubes?
Also, I've got several of the Russian variants for the EL84 (SV-83/6P15P-EV as well as the 6P14P-EV) and I'm hoping those will also run without issue.
This amp would be a lot cheaper if I could use what I already have.
Copied from the Tubelab forum:
I know this amp isn't even out yet, but for those that understand this stuff a lot better than I do, how hard would it be to mod this amp to accept 6922 (and associated tubes) in the driver slot?
I've got quite the collection of these tubes, including the Russian variants (6H23-EV, 6N1P-EV) as well as several 6922's, 6DJ8's, and some 6FQ7's. I know these are not all exactly the same, but many designs allow them to be used interchangeably. Would it be a nightmare to get the Simple P-P to play nice with these tubes?
Also, I've got several of the Russian variants for the EL84 (SV-83/6P15P-EV as well as the 6P14P-EV) and I'm hoping those will also run without issue.
This amp would be a lot cheaper if I could use what I already have.
Yes, we had to make the trip on 4 hours notice after we heard that she had fallen down the stairs in her house. Fortunately she was not hurt, and I fell down the same set of stairs the second day we were there. The broken railing is now fixed.
Many will find this odd, but I am 57 years old and until this trip I have never experienced snow falling from the sky. I got to learn lots of stuff that many people learn as a child. Even though I was told that wearing a T shirt and flip flops outside was not a good idea, I chose not to listen since I sitll sweat when it is cold, and don't feel the cold. It never occurred to me that attempting to walk on icy concrete will result in a butt print in the snow! Spinning donuts in an empty parking lot will result in loud screams from the wife.
Despite the circumstances I had fun... for a few days. I got back to Florida yesterday. It took 3 hours to wash all of the salty road crud off of the Jeep, and despite the 70 degree water, I was in the pool (its about 60 degrees F here now).
All of that fun stuff is done. Boards and parts kits are here. The last 6 weeks were mostly spent dealing with my lack of web site building ability, and Microsoft's discontinuing of the support for Front Page.
Look in the "Tubelab" forum for the latest details:
http://www.diyaudio.com/forums/tubelab/157517-when-will-simple-p-p-ready.html
Please read and add your input to this thread:
http://www.diyaudio.com/forums/tubelab/157745-posts-should-moved-here-tubes-forum.html
I was attempting to rein-in the disaster in my shop a little last week (home improvement projects take their toll) and went through my tube collection to try to get it organized. I came across a quad of Sovtek "EL34M" tubes, which I guess are some relabeled Russian mil-spec tubes. I have no idea how/where I got them. Are these similar to the Russian tubes you were trying, George (6P14P-ER)? They supposedly have higher plate voltage and dissipation ratings making them a bit closer to the 7189.
I'll assume you meant to write EL84M?
Maybe they look something like this?
An externally hosted image should be here but it was not working when we last tested it.
http://s69.photobucket.com/albums/i43/Ty_Bower/Tubes/6p14p-EB-2.jpg
The 6p14p can be distinguished from the sturdier 6p14p-EB by the getter. The plain version has the classic Russian "flying saucer" getter, while the -EB version has a ring getter. The -EB also has noticeably thicker glass, and double micas top and bottom.
The tubes that I have are 6P14P (without the ER). They are not exactly the same as the ones shown in either of your pictures. They have the saucer getter, but only single mica. There are 3 slots in the plate. They were like $3 each from an Ebay seller in the Ukraine. They work fine at "normal" EL84 power levels.
I have some Ei 7189A's. They are EXACTLY the same tube. I have had them for about 10 years and got them from a reputable seller, so someone further up the food chain was relableing. Neither will work at 7189A power levels.
I got 4 JJ EL84's from Stan at ESRC about a year ago. These are the only current production tubes that I have found that handle 400+ volts (plate only, don't feed 400 volts to the screen on ANY EL84 type tube). I plan to get some more of these tubes from Stan when I go to the Orlando Hamfest next month. There is a dual Simple P-P under construction, 14 tubes total.