jon96789 Posted February 21, 2023 Posted February 21, 2023 (edited) I am new to vacuum tube amplifiers and am getting in kind of late in the game. Especially with the Russo-Ukraine war which has depleted stock of Russian-made tubes, especially since they make 60% of the world's vacuum tubes, the rest being from China. With the burning down of the Shuguang tube factory a couple of years ago with no news from them, it is placing even more stress on the vacuum tube market. Some tubes (e.g. Gold Lion KT-88s) are no longer available and the used market on eBay is drying up. I am forced to buy NOS or used tubes on eBay and I know you generally cannot trust the specs on said tubes since almost all the listers are using using vintage tube testers (which ironically uses tubes themselves) that are several decades old. I bet very few have been calibrated and maintained properly, add the fact that all tube testers have an accuracy of ±10%.. To compound matters, they do not have common terms to relate. Some measure gain, some measure emissions, some measure transconductance and other sellers don't even mention any tested values other than good. Also, almost all tube testers test at around 175-200 volts which is nowhere near the operating voltage of the tube. Since the tested voltages are different, you cannot even compare the test results of the tubes tested with other testers. Another issue is that the used tube tester market is ridiculously expensive, decent condition testers run a couple of thousand dollars (and you don't even know how accurate they are). This brings me to the subject of buying my own vacuum tube tester. Right now the only options I can see at are: 1. Amplitrex AT1000 (~$3000) (can test tubes up to 500V) 2. MaxiMatcher 2 ($1000) (can only test power tubes at 325 or 400 volts) 3. MaxiPreamp 2 ($1200) (can only test preamp or rectifier tubes, unit includes four socket adapters for octal tubes @ $55 each) 4. Space Tech Labs Canada ATT-1.01 ($800, built to order) 5. Space Tech Labs Canada ATT-3.01 ($1100, built to order) The Amplitrex is the most versatile but is also the most expensive. Owners however have complained that the system is buggy and has a not user friendly interface which has never been updated in the 19 years since its release. This unit is often out of stock and you might have to wait for the next production run. It can test up to 500V and is regulated. The unit tests for Transconductance (Gm), Emission and Gas. The MaxiMatcher 2/MaxiPreamp 2 can test up to four tubes at once (the MaxiPreamp can only test two octal tubes at once). While the power tube tester does test at 325 or 400 volts which is preferable, the voltage supply is not regulated so the same tube can test with different results depending on the stability of the AC voltage where it is used. The company is a very small time operation and units are built in batches and can be out of stock until the next production run. The MaxiMatcher 2 tests power tubes for short circuits, heater operation and the electrical characteristics of Plate Current (Ip) and Transconductance (Gm). The MaxiPreamp 2 is designed to test dual triodes and other signal tubes for the electrical characteristics of gain (A), transconductance (Gm) and noise (dBm). Both units can test for shorts as well as noise. The Space Tech Labs operates in Canada and seems to be a small operation as well. Units are built on demand and are usually available three-four weeks after ordering. Unfortunately, the testers test at only 200 volts which may not give relevant results. Both units can test power tubes as well as pre-amp tubes. It can test for Transconductance (Gm), Gain and noise. Big negative, they do not accept credit cards or PayPal, only bank transfer of funds. The cheaper device is manually operated and the more expensive is somewhat automatic and comes with a wave form display to check for any tube abnormalities in operation. I have bought a lot of tubes, EL34, KT-88, 6CA7, 6SN7, 6SL7, CV-181 for my Willsenton R8 tube amp, a lot of them used. i want to match the tubes as much as possible into sets after discovering that mismatched tubes causes channel imbalance in the sound. Also big differences in gain in each of the 6SL7/6SN7 triodes can cause unnecessary higher distortion in that channel (I have seen differences of gain as high as 20%). Right now I am leaning on buying both MaxiTest devices. If anyone has any experience with any of the above mentioned devices I would be happy to hear your experiences. If there are other testers than you can recommend, please do so. Thank you in advance, any advice will be greatly appreciated. Edited February 21, 2023 by jon96789 fixed typo 1
Collux Posted February 22, 2023 Posted February 22, 2023 Hi, New tube testers can be rather pricey as you have indicated and older secondhand units could very well be problematic. I've been looking at DIY options, which may or may not be of interest to you? (An alternative here is to get someone experienced, to do the build for you.) Some examples https://www.valvewizard.co.uk/valvetester.html https://valveheaven.com/2015/03/an-inexpensive-easy-to-build-diy-valvetube-tester/ https://www.dos4ever.com/uTracer3/uTracer3_pag0.html I personally, am looking at constructing the recent Electronics Old & New Tube Tester Design, the Build and Testing. A well regarded reference is the following Make your own Tube Tester and Electron Tube Equipment by Gary Steinbaugh https://www.ermag.com/product/make-your-own-tube-testers-and-tube-equipment/ https://tinyurl.com/5ezcj64h In closing, I have copies of a 1960's Australian Electronics article on Design & Construction of an "old school" Valve Tester. >> PM me if you wish a copy. 1 1
jon96789 Posted February 22, 2023 Author Posted February 22, 2023 Thanks for the info. It makes very interesting reading. FYI, I found another tester that seems very reasonably priced. I would have considered this unit except that it can test either 6SN7 or 6SL7 but not both.
Collux Posted February 23, 2023 Posted February 23, 2023 (edited) A further reference that looks of interest, found on Amazon: How to Use, Calibrate, Repair and Upgrade Vacuum Tube Testers by Igor S.Popovich Amazon submitted reader comments for this and the previously mentioned: Make your own Tube Tester and Electron Tube Equipment by Gary Steinbaugh Make for interesting background reading. Edited February 23, 2023 by Collux 1
Ian McP Posted February 23, 2023 Posted February 23, 2023 more than you ever need to know! My (never complete...) Tube Tester Collection https://www.jacmusic.com/Tube-testers/ https://www.jacmusic.com/Navigation/Products-All.html
MosfetMainac Posted February 23, 2023 Posted February 23, 2023 (edited) Not exactly on your list but worth considering the nice tester here and you might get it for the right $$, no bids yet and just over the ditch in Auckland , I've been eyeing it up myself because it's an almost irresistible bargain, but I really don't need another one https://www.trademe.co.nz/a/marketplace/antiques-collectables/tools/listing/4003911137 Edited February 23, 2023 by MosfetMainac 1
xlr8or Posted February 23, 2023 Posted February 23, 2023 (edited) 6 hours ago, MosfetMainac said: Not exactly on your list but worth considering the nice tester here and you might get it for the right $$, no bids yet and just over the ditch in Auckland , I've been eyeing it up myself because it's an almost irresistible bargain, but I really don't need another one https://www.trademe.co.nz/a/marketplace/antiques-collectables/tools/listing/4003911137 Wow, wow and wow!!! $500NZD. I'm in! I have 2 AVO valve testers (MkII and CT-160), why not add a third one to the collection, right? Well my collection is actually at 8 valve testers now. A MkIV valve characteristic meter - I love it, the best of the best of the AVO valve testers with 400v B+! You can also buy a new galvanometer for these now, as the magnetic coils burn out easily when undertaking the 'bouncy' needle to the far right off-scale mutual conductance measurements. Edited February 23, 2023 by xlr8or
muriwai Posted February 23, 2023 Posted February 23, 2023 Is there any one of you members in Melbourne outer east that can check tubes for me?Happy to pay for your time,I have a tube pre amp Supratek that I think may have a dodgy tube?
xlr8or Posted February 23, 2023 Posted February 23, 2023 (edited) The ROE tester is also a good DIY tube tester to consider. http://www.roehrentest.de/EnglishInfo.html My 2 most favourite tube testers though are vintage ones. The Metrix U61C/D and the Nueberger RPM370/375. Yes, they need to be serviced and calibrated, but this is easily carried out if one knows what they are doing. The beauty about these 2 testers is that they show the actual test parameters being used on analogue meters. Also, bogeys are required to undertake relative measurements. The accuracy of the tester becomes far less important when comparing against these bogey standards. This is often how old and modern tube testers are calibrated - against a bogey standard of known lab-based measurements. Edited February 23, 2023 by xlr8or
Collux Posted February 23, 2023 Posted February 23, 2023 (edited) Further details for the DIY 'ROE' (Roehren V10) tester -this is a not inexpensive project, targeted to the experienced builder. http://www.roehrentest.de/index.html https://www.diyaudio.com/community/threads/state-of-the-art-german-diy-tube-tester-curve-tracer.372186/ https://tinyurl.com/yzuzfvrf http://www.roehrentest.de/FAQs.html Edited February 23, 2023 by Collux 1
jon96789 Posted February 23, 2023 Author Posted February 23, 2023 Thanks, butI am not experienced enough to build a DIY tester. I am looking for complete new units.
acg Posted February 23, 2023 Posted February 23, 2023 I have an eTracer that does an excellent job. More expensive, but also easier to use and better results. https://www.essues.com/etracer/ 1
Ihearmusic Posted February 25, 2023 Posted February 25, 2023 +1 for the http://www.roehrentest.de/EnglishInfo.html Might be a bit much for the occasional DIYer though. My unit: 1 1
Candyflip Posted February 26, 2023 Posted February 26, 2023 This one popped up on Facebook Marketplace over the weekend? Palec VCT-3 Valve & Circuit Tester, from the 1930s apparently. https://www.facebook.com/marketplace/item/1583496148837307/
jon96789 Posted March 2, 2023 Author Posted March 2, 2023 Getting back to my question. I know that there are all kind of specs that people throw around, e.g. gain, transconductance, emissions and plate current. What is the most important spec that one should look at? Many suggest gain, others suggest emissions or transconductance. What is your opinion and why? On a side note, I ordered the MaxiMatcher 2 and MaxiPreamp 2 and am awaiting shipment. I was told that they would ship by mid-February and as of today I have heard nothing from them and there have been no response from my emails.
jon96789 Posted March 3, 2023 Author Posted March 3, 2023 I just heard from the Maxi guys. The testers are further delayed because they have not received their circuit boards on time as promised. It appears it will be another month before i can get them. I am considering just canceling the whole thing. It's not as if i really need the testers.
Recommended Posts