 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
In Reply to: SF/Bay Area tube testing Collective - READ! posted by anevsky on October 19, 2003 at 03:47:04:
Please don't misunderstand my post, I'm not trying to discourage your efforts, nor am I intending to knock the products you speak of. But let me point out a couple things:1. The VTV product tests only 9 pin dual triodes as shipped, and to check octal dual triodes you need to get the $60.00 adapter. So it WON'T do "a quick test to make sure that new KT-88 doesn't arc and kill your amp". You will still need a basic tube tester to check for gas and shorts. And the VTV tester doesn't do power tubes anyway.
2. You wrote "Everyone knows that microphonics are ruinous, and simply pinging the tube with an eraser doesn't work so well." Well, the VTV tester allows you to listen, but you still must provide the excitation. In the microphonics test setup, it is simply a high gain amp. You provide the input to the tube, it lets you listen to the output. So you still will be "pinging the tube with an eraser". There is no "go - no go" measurement, you'll have to build a mental database based on all the testing you do.
3. AFAIK, the Hagerman tracer is a nice unit, but one drawback (as I see it) is that it only goes to 380 volts. Plus you need a good quality o'scope to attach it to, so that must be purchased as well. Also, the idea of matching tubes is fine, but to find a set of matched tubes requires you have a sizable batch to select from. So while it can do the job (up to 380 volts, I use 465 on 6550/KT-88/6L6GC etc.), it may have very limited practical value.
So I think you need to up the budget to include a scope, the octal adapter from VTV, an adapter board from Hagerman ($300.00) for "oddball" tubes, and a good basic mutual conductance tube tester with a good shorts and gas check. The total cost will be more like $3K by the time you are done.
Best of luck to you on the project however you decide to go.
Follow Ups:
Here is a reponse I got from Jim after I sent him your critique.I've also posted a few pictures which he sent me. They are curve tests of a 300B
http://www.trailtopia.com/akimball/300b.jpg
http://www.trailtopia.com/akimball/easyscope.gif
-----Depends on what tubes you are using. The VacuTrace won't be doing a 845 or anything of that nature. Really, you don't always need super high volts to measure a tube at THE BIAS POINT of interest. You can get a pretty good feel for a power tube by looking at the lower voltage characteristics too. Check out the pic, it's a 300B overlayed onto a data sheet. You really don't miss that much.
Granted, the VacuTrace is better for lower power tubes, especially triodes. The real benefit is getting curves for the actual tube you use, or for comparison matching. In fact, I rarely bother with gm or other single point measurements. The curves tell it all. And a tube that matches at low volts tends to match at high volts.
Second pic is from a USB-based digital scope that works really well. It's $189 (www.saelig.com) and lets you get jpgs. Else, a very cheap analog scope will do fine (& digital camera). You can get plenty of these for under $100 on eBay. Heck, if you're doing serious audio work, a scope is super handy.
The VacuTrace will do a pair of 6550s at the same time, showing curves from both. But in pentode mode you get above the 100mA limit in a hurry with high screen voltages. So as was pointed out, you cannot run these tubes anywhere near full blast. For that you will need to make your own tester. Maybe a Tek 570 will do it?
If all you want to do is match 6550's, then this may not be the right machine. Better to make your own. The VacuTrace was designed to be very flexible and operate with a wide range of tubes.
jh
-----------------------
Jim Hagerman
Hagerman Technology LLC
P.O. Box 26437
Honolulu, HI 96825
Cell: 808-383-2704
Fax: 808-394-6076
www.hagtech.com
Again, I'm not taking Jim or his tracer to task. As I said, I've heard it was a good machine. I just wanted to be sure you knew the limitations (and Jim H. confirmed them). The same holds true with the VTV tester.BTW, a Tek 570 goes to 500 volts, but the reality is they are so rare that the prices are really steep - if you can find one at all.
Jim,I understood you weren't taking Jim to task. I just wanted to hear what he had to say about the issue as well, and I posted that so others who may be following this thread (very few indeed..) would get to hear from him.
Thanks,
Adam
Thanks for pointing out those inaccuracies.Yes, there VTV won't test power tubes, I stand corrected.
As for microphonics, of course there is no level telling me when to skip a tube. As in all things a little thought is necessary. And comparison. Hooking up the output of this to the input of a good sound card would get you a very nice "picture" of the noise" where many aspects can be analyzed.
I've already planned for the scope - in fact, someone already interested in the collective has offered to let their's stay with the Vacutrace. As for the max voltage, that is a good point. I will write Hagerman and ask him what he thinks about this. I'll send you entire quote.
Yes, a hicock or something would be a nice addition. Maybe we can swing that.
Thanks for the info,
-Adam
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
