02-06-2022, 10:23 PM
Andy,
Most of my experience with 5AR4's is in modern guitar amplifiers. The complaint is noise and random LOUD popcorn noise.
Hang a CRO off the filter capacitor and watch. Every so often the is a loud pop. Overall hum is "higher than I expect ". The pop is a very short spike on the CRO trace.
I replace the rectifier with GE made in USA made sometime in the 50's. ( I still have a few of them ) Switch back on from the same power point on my bench with various
other bits of kit plugged in and running. ExactIy the same setup as before, but about 2 minutes later. thought at first it could have been my soldering iron cycling, but its not.
The hum has dropped to just audible. There are NO pops, there is no more noise in general. I wait several hours and all is well.
I replace the GE rectifier with Sovtek. Its back!! hum, noise, pops and farts. I have been doing this for 50 years!!.
Im not easily caught out .( mostly :-) ) I cannot say why they are inferior, unless the vacuum is not as good as the 70 year old GE's.
Its about the only feasable explanation in my head. I do know I will not build any amplifiers with Sovtek EL34/6CA7, KT88 or 6V6's.
I always end up with a crappy amp that always gets warranty claims. In the case of 6V6's I replace the bases and fit 7C5 NOS made by Sylvania.
I dont see the amp again. ( Maybe the customer is so peed off he goes somewhere else ?? ).
In general just the visual inspection shows random QC problems, Mis alighned mica's, Getters at crazy angles totally different in each example.
Sometimes the whole valve is skewiff inside the bottle. I have had dry joints in the pins in the base as well.
The ONLY advantage with the russian stuff is cost. a 5AR4 in sovtek costs about $25 Au. about 12 quid to you.
I paid about double that for the GE NOS ones I have, and I bought them probably 30 years ago.
You asked me to explain, and thats about what I get.
Regards
Joe
Most of my experience with 5AR4's is in modern guitar amplifiers. The complaint is noise and random LOUD popcorn noise.
Hang a CRO off the filter capacitor and watch. Every so often the is a loud pop. Overall hum is "higher than I expect ". The pop is a very short spike on the CRO trace.
I replace the rectifier with GE made in USA made sometime in the 50's. ( I still have a few of them ) Switch back on from the same power point on my bench with various
other bits of kit plugged in and running. ExactIy the same setup as before, but about 2 minutes later. thought at first it could have been my soldering iron cycling, but its not.
The hum has dropped to just audible. There are NO pops, there is no more noise in general. I wait several hours and all is well.
I replace the GE rectifier with Sovtek. Its back!! hum, noise, pops and farts. I have been doing this for 50 years!!.
Im not easily caught out .( mostly :-) ) I cannot say why they are inferior, unless the vacuum is not as good as the 70 year old GE's.
Its about the only feasable explanation in my head. I do know I will not build any amplifiers with Sovtek EL34/6CA7, KT88 or 6V6's.
I always end up with a crappy amp that always gets warranty claims. In the case of 6V6's I replace the bases and fit 7C5 NOS made by Sylvania.
I dont see the amp again. ( Maybe the customer is so peed off he goes somewhere else ?? ).
In general just the visual inspection shows random QC problems, Mis alighned mica's, Getters at crazy angles totally different in each example.
Sometimes the whole valve is skewiff inside the bottle. I have had dry joints in the pins in the base as well.
The ONLY advantage with the russian stuff is cost. a 5AR4 in sovtek costs about $25 Au. about 12 quid to you.
I paid about double that for the GE NOS ones I have, and I bought them probably 30 years ago.
You asked me to explain, and thats about what I get.
Regards
Joe
