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Post by mattbaer355 on Jan 20, 2008 14:42:22 GMT -7
Hi All,
I need some tube recommendations for my Dr Z amp as a power tube is going on me and I would like to retube the amp. Right now I have the following tubes:
Sylvania Germany EF86 EI Yugoslavia 12ax7 EL34WXT Sovtek Reflector 5AR4 GZ34 China
I bought this amp second hand and was told that these are the original tubes that came with the amp. The amp is from 1998 and has the permanent market date on the chassis.
I was looking through the older posts and seen what myles recommended. Although it is tempting those recommendations will cost me over $350 to have the entire amp retubed and have a set of spare tubes. I would like some tube recommendations and if what I have now in the amp is considered good or poor. I would like to stay away from NOS if possible as I would like to find replacements years from now that are not a fortune. If I can keep the total price under $200 that would be optimal (I want 2 of everything and 4 power tubes). If anyone could give me some recommendations and advice I would appreciate it.
Thanks and kind regards,
Matt
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Post by pistolpete on Jan 20, 2008 17:55:31 GMT -7
hey matt, im not sure what they cost but mine has svetlana "winged c" EL-34's in it. i havent investigated the other tubes. but the output distortion is awesome. equal parts dirt and clarity if you know what i mean. id recommend 'em. ill see what the others are and get back to you. be well, PP
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Post by atalog on Jan 21, 2008 8:47:22 GMT -7
I did the following in September 2007 based upon Mike Kropotkin's inputs. Here is what he told me. I got the NOS Siemens. Dr Z likes the Dario Miniwatts in his amps. For EL34s, either the NOS Siemens, Groove Tubes EL34Ms or SEDs would be good. Mike Kropotkin KCA NOS Tubes and Amp Repair www.kcanostubes.com Policies, warranty, shipping costs www.kcanostubes.com/content/bio.asp 703-430-3645
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Post by myles on Jan 25, 2008 14:29:02 GMT -7
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Post by mattbaer355 on Jan 25, 2008 16:07:05 GMT -7
Thanks for all of the recommendations! I will order the new tubes on mon. after I contact Mike. I am familiar with electric devices but not too much with amp biasing. Can anyone tell me how I can bias this amp or send me to a link explaining it? If it seems like too much then I will take it to my local amp guy but I think I can handle it myself as I do build racecars in my other hobby. I have a volt meter...I just need some direction.
Thanks again and kidn regards,
Matt
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Post by mattbaer355 on Feb 7, 2008 11:28:53 GMT -7
I installed the new tubes and the amp sounds great. I am getting some very very slight microphonics (I believe from the EF86) but I have heard this is normal. The amp does sound great. I was able to remove the amp form the case and set the plate voltage to 440 volts as recommended by the bias notes from DR Z. Does anyone have any croessreferences for plate voltage to ma onthe power tubes? I.E- does 445 volts equal ~40ma? The 440volt plate voltage is supposed to net between 28-32ma at the tube.
Thanks again for the recommendations and suggestions...much appreciated.
Matt
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Post by kruzty on Feb 7, 2008 11:38:33 GMT -7
I installed the new tubes and the amp sounds great. I am getting some very very slight microphonics (I believe from the EF86) but I have heard this is normal. The amp does sound great. I was able to remove the amp form the case and set the plate voltage to 440 volts as recommended by the bias notes from DR Z. Does anyone have any croessreferences for plate voltage to ma onthe power tubes? I.E- does 445 volts equal ~40ma? The 440volt plate voltage is supposed to net between 28-32ma at the tube. Thanks again for the recommendations and suggestions...much appreciated. Matt You should try some of those rubber tube rings on the EF86. That helps with the microphonics.
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Post by mattbaer355 on Feb 7, 2008 12:20:39 GMT -7
I will have to try them! Thanks for the suggestion.
Best regards,
Matt
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Post by mattbaer355 on Feb 27, 2008 7:35:50 GMT -7
I went ahead and ordered a Bias Right from weber speakers and checked the bias. Using the method from the DR Z bias notes the ma were at 34. A small turn of the bias pot and I was able to change the ma to 36. The amp now sounds great with no micorphonics (I received a bad Ef86 and Mike sent out a new one to replace it). I would like to thank all of you including Mike from KCanostubes for the hell and advice. Rock on!
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