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Post by jennerc on Nov 22, 2017 22:43:51 GMT -7
got a used EZG in beautiful shape serial # starts with U--- so old style oval front- with grove tubes #4's . original likely?
Thought I'd go with the current recommended TS and got a bias rite for the job (always wanted one anyway). The GTs read 28 at 450V- about spec- at about 12N on the bias pot, Sounds good and pretty happy. I realize there are some little estimations the bias rite makes - cathode resistor method etc...
The new TS read 35 at the LOWEST bias pot setting at 452V. I can't go any lower, but I want to- sounds a bit harsh and is definitely louder (good or bad.. ). What's going on? 35 is safe for the tubes OK but at the bottom of the bias pot? with a suggested 28 per Doc's specs?
Are the tubes that different or is the newer model that different. Do I need to send the amp to the doc for upgrade?
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Post by headshrinker (Marc) on Nov 23, 2017 11:01:50 GMT -7
My guess is that the new tubes you have are way out of specs. Doc always calls for medium range tubes. Yours sound like high. There are others who know more about the workings of amps though. I've never had a problem using the bias pot on Z amps and being able to get medium tubes to the right numbers.
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Post by jennerc on Nov 24, 2017 5:22:41 GMT -7
thanks. Could be - I know this variable exists but haven't run in to it at this level before. I wrote the tube guy to ask. The numbers on the boxes are 47.4 / 2960 and 45.7 / 2910 from his matching process - over my understanding despite a long Bing inquiry last night. (some expressions of plate dissipation and output I gather, but I can't benchmarks for comparisons). The tubes are a bit warmer sounding after a few hours playing (or my ears are numb- it's a loud amp-), but bias readings haven't changed much. I worry I bother you folks as an inexpert hobbyist, but, I have built several guitars, an amp, own 4 others (2 Z's) and tweak tones compulsively best I can over years, so I guess I rate some small bonafides here. I take courage to post again (the lurker exposed). My apologies as applicable for your indulgence. And certainly thanks either way.
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Post by headshrinker (Marc) on Nov 24, 2017 10:42:40 GMT -7
Not a problem. We're all here to help each other. We've probably all posted something hoping there was a been there, done that, among the rest.
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Post by jennerc on Dec 2, 2017 8:39:34 GMT -7
new set arrived. Plate current listed as 18.3 and 19.0- much lower. (lower than the medium gain Z recommends as it turns out) Biased to 28 per website - that's 27.4 and 28.6. Voltage read 470 (higher). These are nice looser sounding.-plenty of harmonic content. If there's even order distortion from the small variance in matching I certainly can't tell. Some nice blackface OD sounds at appreciably lower volumes. (celestion gold 12") I didn't need the Z brake to break up the cleans with pick attack. So I learned a lot. The softer rated tubes make a huge difference the character and feel , volume overall may be a bit lower but not much - just some earlier breakup and touch happiness. Whole different amp. Happy. Thanks, z talk. then I added in zen drive. well...
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Post by Jaguarguy (Mike) on Dec 2, 2017 10:03:44 GMT -7
Glad you figured it out! Doc's amps age great with or without pedals!
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