Overview and compare the Amplitrex AT1000 with the Audiomatic SOFIA, and the Roe-Test.

Interesting, with the Sofia a tube test is performed faster as with the new made AT1000, which software works very slow. What takes a bit longer, is to set up the Sofia. So for a quick test on one tube, the AT1000 is much better, but when you want to test and match a series of -say- 50 tubes the Sofia is the undisputed king. I would say for series testing, first comes the Sofia, then comes nothing, and then comes the AT1000. The result is so much better, you can't even compare it. The Sofia tests a tube 10x faster. Moreover, you can save the curves, and let the Sofia do the matching. So it tells you for instance: Pair#1 is Tube 4+12, Pair#2 is tube 17+49, etc. So it comes up with 25 pairs, and even sorts them by matching quality. It does so by overlaying the curves best possible way. Well I can tell you if you want to do this with the Amplitrex (overlay the curves) you need to print them, put several sheets on each other and hold them against the light. I can do so with maximum four sheets of paper and with more sheets you can't see what're doing any more. Doing so in the computer age, I feel really silly, and for myself here, it is matching which I use the AT1000 for most for. This 20 years old Sofia does this job in 10 seconds. Anyway each tester, surprises with nice features, so you must decide for yourself which one you like better.

First let me start with the Shorts risk with a Sofia, because you always have to keep this in mind when using it. When you bypass the "shorts tests" with any historical tube tester you make a mistake because these can be seriously damaged by a shorted tube. With computer controlled testers, you have little influence on this. The Sofia does have an overload test, and a heater circuit test. So I can not say it is unprotected, and indeed it switched off when I made an error with the cabling (tube connections). So it is not unprotected for sure. Though the previous owner warned me, the tester needed a few times a repair, after testing hundreds of EHX KT88, and some shorted ones were amongst those. Since he used the tested for KT88 high quantity testing mainly, he gave up on the Sofia. He had it repaired once more, and then sold it to me. Now I don't know what he has been doing, but from my experience with people, tubes and equipment, I learned that so called "professionals" (and companies) make serious mistakes as well. Well still I regard it a strong warning he gave me, and I will not put any questionable tubes on the Sofia, and not use it as a work horse. Only use it only for tubes that are basically good, but I need the curves from. When I have time, I will put a protection series lamp in the gird circuit, same as Hickok uses it, and I have seen that on other testers too. The other power supply outputs I will protect with normal fuses and put reverse diodes over it. That seems all missing. The most common short is cathode to heater with KT88. Since the cathode is grounded in the Sofia, that will short circuit the heater, so the fuse hopefully helps here. Another common short is grid to cathode, and most likely the a series lamp will cover this very good, since a low current lamp is known to be the fastest fuse there is. From my R&D days I remember an extremely useful method to protect high voltage motor control circuitry. You use a fast power thyristor, which shorts the DC voltage directly after the capacitor of the rectifier circuit, and in the path is a normal fuse. Very crude, but the most useful method I have ever seen, and low cost too. When you fire this thyristor, you switch off the High Voltage to all electronics with a delay of less than a micro second. Then, some 10 milliseconds later the fuse will blow. Interesting, the thyristor survives this. Even if you blow the thyristor, the damage is a short circuit, so it still does it's function, and all you need to do is replace it. For firing the thyristor you can use any detection circuit you define yourself. Such as a current overload detector of the heater supply in this case. Well... these are just ideas. I will first put a fast fuse inside.

I once had a FACTORY NEW Electro Harmonix 6922 tube with a hair-thin wire wrapped around all pins, in a circle! So all pins were short circuited. Don't ask me what that was, but it came out of a box with 100 factory new tubes, from Russia. Also I have still here in my memorabilia cabinet a new Electro Harmonix 6SN7, also from a 100 pcs factory box, with the socket one position rotated, so that tube can never have worked. I do not try to prove here, they do lousy testing at EHX. These were tested with the Russian L3-3, and it survived those, though the 9-pins all together shorted 6922 made some smoke come from the inside. Well it survived that. Actually the Sofia would have spotted this mistake too, because it will not switch on the High Voltage, after the tube passes the heater current test. Heater current is measured, and must reach it's correct value before the rest of test program can start.

Another possibility is, a tube that appears good at 250V will short circuit at 500 Volts. This can happen if the tube is gassy. This I already had, and the tester switched off normally and detected the error.

The weakness is, it runs under DOS which is a pain in the ass to set that up, but ok I have it done, and spend the Sofia it's own DOS computer. This is an Hewlett Packard Kayak, with a multi boot option for DOS and W2000. After the tests are done, I can re-boot in W2000 and copy the results on a USB stick. From there open teh results again under Windows7. Though I did manage to set it up as well under Windows7 and a very special virtual machine. The regular virtual machines, they all don't work. The good thing is, once you have the software working, it is the best piece of test software I have ever seen. Even under DOS, the speed beats anything I have seen before, and Graphics quality is excellent. If you have an XP machine, the Sofia software runs fine, but only for looking at test result files (the .pte files). I use this option a lot, because once you have a .pte file, you can plot the curves on your screen once again, and move teh cursor all around to analyse the curves, and get gain, transconductance and Rp at a random point. Also matching can be done afterwards, or repeated with a few of the tubes removed from the list. Still dor actually measuring, you need DOS always.

What is good about the Sofia, and seldom mentioned, is the fabulous matching software. You can save up to 200 curves, and the program calculates which curves fit best to each other, using a mathematical error function. I mean you can do this in Excel for one single operating point, but for complete curves it is like programming a piece of software. The Sofia does this in 10 seconds for 200 curves. That's DOS :). So we have to say it, the software is GREAT and the best part of it, and in REALLY compensates the trouble using DOS. Furthermore, graphic capabilities of modern LCD monitors seems the perfect thing for this software. I don't know how this works, but it looks if the pixels from the DOS Program fit directly 1:1 on the pixels of the LCD monitor. The result is a crystal clear picture. (see at the end of this page, but these are compressed jpgs. The originals are sharper even)

A mystery remains.... At the power supply main board is a large connector, unused. It is of the same kind as the top board. So one connector connects the power supply to the microcomputer board, another (similar) one is empty and unused. Who knows what is was intended for! If I was to say, I would connect a relay board to it, so the cables at thee deck get obsolete, but that is really only just a guess.

It has no tube data base inside, just 10 tubes to give you an idea how to do it yourself. However that works fast an easy, and after a while you have what you need.

I found only one. The heater voltage is connected with one end to ground, and the other end is heated with DC. For indirectly heated tubes that is no problem, but this gives an issue when testing directly heated tubes (DHT). The reason for this is, with DHT, the cathode's electrical reference is by definition the middle of the filament. So you lift up the cathode reference point by by half of the heater voltage. Not much of an issue when the heater is +2.5V and the grid -45V, and low gain tube such as a 2A3. The error is 1.25Volt only and you would not even notice at this low gain of 4x. However it is a major issue with a tubes like RE134 or the Emission Labs 30A.

This is made in non-SMD which you will start to like once you need to repair it. There are very few connectors, which devices are always a long term problem in old electronics. The electronics don't get hot, and it needs to cooler fan. The fact the electronics stay cool, it the ticket for a long life. The printing on the IC's has not been removed, and these are all standard parts, that still can be bought. The circuit boards are clean and tidy, and doing service and repairs is not hard to do. The A/D converters have many potentiometers, but probably most are just for the offset of the Op amps, and when needed I can dig into this. So far this is not needed, and I won't touch it.

The PC port is RS232, and here comes a bit of a problem setting up modern PC's for an RS232 port. Though I was able to use a USB to RS232 cable under Windows7, the accuracy under a non-windows DOS version and a real RS232 port is better. For the rest of the DOS story, read the software part.

Very useful, and simply forgotten on many other testers is the High Voltage "HAZARD" lamp, indicating the high voltages are switched on.

A major shortcoming of the SOFIA, is the tube connections have to be made by plugging in the cables. Well some protection comes from this too, since you can not plug in two cables in one hole, so an error you usually see, but this stays kind of touchy. Best is to make colored overlay cards for the tubes you want to test. That works faster, and is error-proof. An advantage we have here too, since these are all banana connectors, and you can access the tube connections easily for whatever purpose you need it. Like connect external meters to it. Even put in a current link.

The deck panel is removable easy and quickly, and you can add more tube sockets to it.

Now looking at the specifications this makes you amaze. This speaks for itself. It can even test 6C33 which is usually a problem with other testers because of the heater power. Also you can make curves of the 845 and 211 up to 700V. Not extremely much for this tube, but you come in a meaningful area of the curves. Even a GM70 with it's 20Volt, 3Amp heater is possible.

Sofia tube tester specifications
Resolution:      16 bit
Plate voltage range:      0...700V
Plate current rage 0....250mA
Grid screen voltage range:      0...700V
Filament voltage range:      0...24V
Filament max. supply current:      5A
Grid voltage range:      +10... -150v

Overview and compare the Amplitrex AT1000 with the Audiomatic SOFIA, and the Roe-Test.
	Amplitrex AT1000. (This is based on the Testers we bought in 2009 and 2010) Manufacturer Homepage	Roe-Test Homepage This is a KIT. You must build it yourself. Functionality is higher than AT1000 or Sofia.	SOFIA Manufacturer Homepage

Technical support	Email is answered timely and professional.	I WANT TO POST MORE INFORMATION HERE ABOUT THIS VERY INTERESTING PRODUCT. IF SOMEONE WANTS TO HEKLP ME HERE, PLEASE LET ME KNOW. REAL OWNER INFO IS NEEDED FOR ALL THE WHITE BOXES.	They offer repairs still. Provided they can buy replacement parts needed. Tester Manual
Schematics	You should try.	Yes	Dear Mr. van de Walle, As Mr. Bigi told you over the phone we do not supply schematics of our products. This a Company policy since 1985 and up to now we had only elements to enforce it. Best regards, Maurizio Jacchia. President Audiomatica Srl (Received By email, Di 19.07.2011 16:06)
Windows compatible	Yes	Yes	No
Measurement Resolution	10bit, and I can confirm it is really there and no offset problems. However it is not enough bits or some tubes. For instance 6SN7 tests in steps like this: 2550, 2650, 2750. The last two digits are for the birds, they are always xx50.		16bit. Which is achieved by external D/A converters. So no analog Single Chip inputs. When you go to very low voltage, the Sofia has 100mV offset, which is can be a lot when you test tubes with low grid voltage. I am pretty sure this is a calibration issue. So the tester itself can not be blamed after 20 years.
Measurement range	Very good in general. Though plate voltage can not be set lower than 75 Volts. This is a problem for making curves of tubes like E88CC.		Absolutely AMAZING. It can do 0...700V DC, 250mA Filament 0..24V 5A (Wow!) and Current measurement included.
PC and or stand alone	Both. PC only windows. ALSO there is a large display in the machine, indicating many data.	Only PC	Only PC
HARDWARE
Shorts test	Yes		No. This is dangerous, one day you are going to have a shorted tubes, and you might also connect something wrong, with those loose cables.
Gas test	Yes		No, See above, because a gassy tube may short spontaneously.
Hazard Lamp	No		Yes
Sound Test	Yes		No
Hardware access to all tube connections	Only Plate, Cathode and 1st grid.	Yes, with full relay matrix	Yes, by hand switching
Dust proof cover	Yes	Depends on yourself.	No
Measure Filament current	No		Yes
Hardware Quality	Very good, but the Fan is definitely too loud.	Depends on yourself.	Hardware is very good. No fan. What I like, there is almost no micro stuff in there. Even IC's. So if you damage something, you have a good chance to fix it yourself. The "secret" schematic issue, I accept during normal production, but not if production is stopped. For me personally, I would never buy an new production This Of course this is my personal opinion only. If you buy a new product that they refuse to give you the schematic, you are free to feel good about this.
SOFTWARE
Software updates	I never received one.		No. Version 2.1 for DOS is available from the Audiomatica Website, but this is not an update, it is very old.
Curve tracing	By default it draws only one curve. Yes, but it needs a lot of trial and error before you have the curves drawn the way the should look. I am not so enthusiastic about this. Also the "Excel look" of the curves is not so much my style.	Optics of the curves not as nice as the SOFIA. It has the "Excel Look" like Amplitrex has, but options and possibilities are the best of the best.	Curve charts are drawn the way they are supposed to look, right away. Scaling can be done afterwards, even if STORED curves. Wow!!!! This is an EXCELLENT Software job.
Speed	The AT1000 is not impressing with speed. Depending on what you do, the Sofia can be 10x faster, and produces higher resolution data still.		Once the test is started, the curves are plotted after just 10 seconds. Dynamical and static data is derived afterward from the curves. Excellent feature: When you press"start" too quickly, curve plotting is auto delayed until the tube heater appears warmed up. This is done by monitoring the heater current draw. (Checked it with a scope) Great software job.
Review saved results	Yes.		Another top class feature of this software. You can save the charts to disk, and you can change the scales afterwards. So you zoom in and out. Like test the tube from 0....600V. Another day, you can plot a curve from 0...200V only, it uses the original measurement. EXCELLENT Software job.
Tube parameters at multiple operating point	No.	No.	Wow! A most remarkable feature is used here. You can move a marker around in the curves, and you get all tube data at the specific operating point. Even in STORED curves you can do this later. So you use a 300B at 320V or at 480V, and that makes a LOT of difference. Amazing this part of the software works still under XP. Run the sofia.exe file from the DOS window, ignore the "hardware not present" message, and open this pte file. FROM the DOS application, that is. So not click on it in windows, that won't work. First get sofia.exe from Audiomatica homepage, for free. It works under XP or lower. For W7 or higher, you must get yourself a DOS emulator. Best is DOSBOX "megabuild" version. After it works, you can load the pte files, save it at the right directory where DOS can find it. This keeps you busy for a while, until it you have it running, but the reward is nice. So with this pte file I have given here, and working Sofia software you can go ahead. Here is how to open the file. Marker at pos1. Market at pos2. See how Rp changes!
Save curves in graphics format	No.		Yes. The are stored in bmp format, so you don't loose the resolution.
Software Maintenance	Many things, that I would say are not elegantly done, or not done at all. I reported many issues and small items, My impression is, Amplitrex is not interested in any of that. Don't think I never tried.	Very good. This is living software, suggestions and improvements are implemented in the next versions	One major bug, see below. For the rest, I found nothing to improve.
Software (1) Pentode curves	No. This an error. Testing them triode mode, is not the real thing. Problem Reported to Amplitrex, it seems technically possible, I have a working test version, but that is all. It was not implemented in an update.	Yes	Whatever you like. Even specify Ultra Linear percentage
Software (2) Diode Curves.	Officially the answer is No. I found a way to do it myself, even for twin diodes.	Yes	Yes
Software (3) Grid voltage	Grid voltage is measured wrong for Directly Heated Tubes. The effective grid voltage the tube sees, in increased by half of the filament voltage. This was not compensated in the software. (Though this would have been very easy to do). So when the tester draws a -1Volt line for a 300B, it is in reality the -3,5 Volt line. Same error is made with the normal"Tube Test" page it produces. With the Amplitrex, I only report it here, for everbodies interest, but reporting it to Amplitrex has only resulted in a work-around advise.		Grid voltage is measured wrong for Directly Heated Tubes. The effective grid voltage the tube sees, in increased by half of the filament voltage. This was not compensated in the software. (Though this would have been very easy to do). So when the tester draws a -1Volt line for a 300B, it is in reality the -3,5 Volt line. Same error is made with the normal"Tube Test" page it produces. With the Sofia, thinking of an improvement is 20 years too late of course.
Software (4) Transconductance	This is an issue with the AT1000 only. In the stand alone mode, Fixed Bias, the transconductance is represented in percent (of something). Problem is transconductance (in percent!) is only meaningful at 100% plate current. However at Fixed bias, 100% plate current is a matter of coincidence.
Software (5) Emission Test	Though the software is telling you "Emission" and even shows this in percent, it is actually not measuring Emission at all. Just measures plate current and calls this Emission. That's a real slip.		No
Matching	No. You have to decide for yourself if what you see is a good match or not.		Yes. Most excellent method used, which is a MASTER EXAMPLE of engineering quality. This method if HIGHLY RECOMMENDED to study, for every one who wants to make software for tube matching. So you can test 100 tubes, and the software tells you what tubes have CURVES that fit well to other tubes. Not just one or two test points, but full CURVES matching.
Quality Control	No. With "quality control" I expect the tester to tell me if a tube is good or bad. The Amplitrex does not say so.		Yes. So the tester tells you if a tube is good or bad.
Export of Test report	No.		Yes. by hand or auto mode. Saves a bitmap
The future of this software	The software uses Microsoft internal modules, like MSCHART, etc, which is part of the microsoft Operating system. However these are very old microsoft modules, and I I don't know what happens if one day, the Microsoft Gods decide, newer versions of Windows do not need compatibility with the old versions.		The Microsoft Gods have decided not to allow direct access to the RS232 ports inn all Windows Versions, meaning the Sofia can only run under DOS. However as MS obsoleted DOS, with the coming of W7, something nice took place: The open source community started to make DOS emulators. These all have the problem that Windows per definition will not allow direct access to the RS232 and LPT1 port, and besides, DOS expects an RS232 mouse on COM1, and nothing else. I expect good solutions with newer DOS emulators. Right now a 100% good solution does not exist. Use an old DOS PC for your Sofia is the best.


OVERALL RATING	FOUR Stars * * * *	FIVE Stars * * * *	FOUR Stars * * * *