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Ping Gartenman or tube knowledge


USNRET

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Where did you get your GL's, good price?

I bought my quad Gold Lion (reissue) KT-88's from bnb_tunes on ebay. $200 shipped. I would recommend. Link. No affiliation.

He is also the best source for Mullard CV4024 NOS tubes, one of the best 12at7 tubes out there.

I second the recommendation of "bnb". I got some CV4024's from them and they are excellent!

Herb

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I wonder about the bias. It's set at about 0.47. Plug in the power tubes, power up and cringe, wait then bias again or what technique?

.47 bias seems awful low, (or is that what you're just starting at when replacing the new tubes?.) KT88's in the VRD's should be between .60 and .80. Craig runs his at .70 as do I.

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I wonder about the bias. It's set at about 0.47. Plug in the power tubes, power up and cringe, wait then bias again or what technique?

.47 bias seems awful low, (or is that what you're just starting at when replacing the new tubes?.) KT88's in the VRD's should be between .60 and .80. Craig runs his at .70 as do I.

Per the manual Craig recommends between .50 and .65 VDC and he states in his manual for the VRD "I personally run mine at .55 VDC". If you don't have a manual, call Craig and I'm sure he'll get you one. I just hate to see people prematurely burning up power tubes. Where did you hear Craig runs his at .70?

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I wonder about the bias. It's set at about 0.47. Plug in the power tubes, power up and cringe, wait then bias again or what technique?

.47 bias seems awful low, (or is that what you're just starting at when replacing the new tubes?.) KT88's in the VRD's should be between .60 and .80. Craig runs his at .70 as do I.

Per the manual Craig recommends between .50 and .65 VDC and he states in his manual for the VRD "I personally run mine at .55 VDC". If you don't have a manual, call Craig and I'm sure he'll get you one. I just hate to see people prematurely burning up power tubes. Where did you hear Craig runs his at .70?

I have tried settings from the mid .40s to the mid .60s and the higher .40s sounded more mellow to me, my taste. I do have the manual and have discussed the bias with several folks, Craig included if not mistaken and I understood (or mis-understood) that a setting in the low range was not a problem whereas a setting too high would be.

Now that I have changed out the 82 and 83s for the 12AUs and 12AXs, I need to get some time on my ears and then run back thru the the bias range before swapping out the VAs for the GLs.

Thanks for all the good info guys.

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you are exactly right, did you read the same thing in the manual that i read about the settings? i've actually talked to Craig about this issue as well and I know he doesn't run his high, rather low like you do, if it sounds good at low the tubes last way longer...i think you'll love those GLs, again i'm glad you liked the RCAs, Brent Jesee sells nothing but the best!

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This is interesting. My manual says to run between 0.65 and 0.75 VDC for KT88s and states that Craig personally runs his at 0.70 VDC. The same discussion is included about lower voltage settings and longer tube life though.

Perhaps some clarification is in order from the manufacturer!

-PB

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This is interesting. My manual says to run between 0.65 and 0.75 VDC for KT88s and states that Craig personally runs his at 0.70 VDC. The same discussion is included about lower voltage settings and longer tube life though.

Perhaps some clarification is in order from the manufacturer!

-PB

Just to be clear, I have the stereo version of Craig's VRD amp. This may or may not be different from the mono version.
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I've owned both the stereo and mono's, and have manual's for both. Maybe there's someting different about your particular amplifier, but "normally" KT88's are run around .70 in the VRD's. I'll send you an e-mail, and if you reply I'll send you the manual I have in .pdf format.

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The bias configuration of the VRD mono blocks changed about 2 years ago. The manual supplied with each set is the correct bias. The older version ran the output tubes at a higher current setting. The older versions can be updated to the latest revision which will extend output tube life.

The older models should not be biased to the new models settings. Well they can be but the Sonic results will not be to pleasing....

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go this website on scroll down about 1/3 and Brent Jesse has an excellent video showing older Genalex's, G.E.C.'s and Tung Sols so as not be sold fakes. Here's the website: http://www.audiotubes.com/audtube.htm It's called How to spot a Nos KT 88 or 6550" or something to that effect. Pixs of the reissues and their boxes can be found anywhere on the web.

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I also recommend Brent Jesse for tubes, I've bought all my front end tubes from him and have nothing but good things to say about all the tubes I've bought from him as well as his customer service. My personal favorites in the VRD's are the Siemen's Longplate 1953 Haltron label 12AX7 and the Siemens nickel plated 12AU7. And of course a Siemens CCA in V1 of the Peach!

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Ok master, here's another request for info


Someone states that "These tubes tested excellent 52-53 51-53 50-53 47-47 where the tv7 states 32 is the minimal good and most new tubes test in the 49 range" what does that mean?

1) I assume the two numbers (52-53) mean two different tests performed.

2) That some test set manual gives the range of minimal of 32 and that all most NEW tubes of this type test at approximately 49.

3) All things manufactured has some engineered tolerance so a new tube may indeed surpass 49 but exceeding specification is not rejection criteria,

4) Does one assume that the 'best sound' from that particular tube would be at the new range and if so then as it lowers then the sound quality decreases; would the sound quality then decrease if the test revealed that the tube tested higher?


What gets me is that a WHOLE lot of advertised tubes exceed the nominal New specification. It would seem that, if portrayed accurately, the NEW test point would skew
upwards over time due to the amount of tubes exceeding the initial 'new spec'.


Possibly the original manufacturer exceeded the customer's spec or advertised spec (of say 49 in the above case) but never changed the spec to the actual "grade" they achieved in manufacturing so as to have a far better QA pass rate.

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One more thing I have noticed since changing from JJ ECC 82/83s to the RCA Clear Top AU/AXs (installed in the VRD) is that with the Peach preamp dialed all the way to min stop I still hear output where before it was silent. By output I mean music, not noise. I turned down the gain on the Peach by 50% and still hear it. Here again is an assumption, the RCAs have more gain.?

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All things manufactured has some engineered tolerance so a new tube may indeed surpass 49 but exceeding specification is not rejection criteria,

this is correct!

just because a tube tests lower then the "49 range" does not necessary mean the sound degrades...i have 4 Tung Sol 6550 Black Plates which most new tubes test at 62 and they test at low 50s with 44 being minimal good and they have sounded (over 12months) as good as some that i have that test good, they just won't last as long...

the 2 test scores are tests for 2 separate parts of the tube and should be within 5% tolerance of each other (5% of the tube whose 1 side tested 52 being approximately 5.2 so the other section of the tube could be as high as 57.2 and would be within acceptable tolerance) ...

now why some tubes test higher than factory specs for new, taking into account inert gases used it cannot be an exact science in tolerance levels...i would assume the manufacture desires a rating of 49 but sure isn't going to throw out any that test better than that and like you said if you set the standard low than your QA rate will be higher

as to why manufactures do not skew specs upward i would guess is that they take the average of new tubes manufactured over time taking into account accepted quality control standards...your comment, "Possibly the original manufacturer exceeded the customer's spec or advertised spec (of say 49 in the above case) but never changed the spec to the actual "grade" they achieved in manufacturing so as to have a far better QA pass rate is a very valid point

in closing those are very good tube ratings, with that being said even if they tested 32 they would still probably sound good (remembering exception to every rule) but whether they are going to last 1 month or 1 year depends mostly on how they were used in the past (higher bias=less life and if the bias was frequently checked between other power tubes,sort of like the timing on your car engine, so all tubes bear the load equally ) and the future...i check my bias weekly

good questions!

corrections or additions welcomed as i'm never too old to learn...

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