| Author | Message | ||
     MikeCox |
I’m currently refurbishing my 212HD-130. I’ve had it 25 years (second hand) - never had to go into it for any reason. Not being much of an electronics whiz, I thought: “after all this time, it would seem like the tubes would have to be weak” – so I ordered new tubes for it. I'd heard lots of general chatter over the years about "Groove Tubes" (almost all of it seemed positive). Upon reading these threads, I thought I'd post to see what kind of decision I made (albeit after the fact – next time I’ll know to come here 1st). Thanks in advance for your responses. GREAT WEB SITE! Mike in Texas | ||
| michael kaus |
I personally think they are nothing to write home about. The 700v that the MM amps have on the plates are pretty rough on standard tubes. I use JJ's in my MM and they seem to last for a few years before thay go south. You MUST bias them properly if you have the 12ax7 PI tube or they will eat tubes. Mike | ||
| Anonymous |
what model number are the JJ's that you use Mike? I have the 12ax7 with 6CA7 tubes now... | ||
| michael kaus |
I use the E34L's and bias them about 23mA of idle which is a little cooler than what is normal but mine last so that's my 2c plain. Mike | ||
| Anonymous |
23ma on the control grid, I assume there would be 4 trim pots inside... using ohms law to calculate the current... what would be the highest people use on the control grid current? you said you run them a bit cool?....thanks | ||
| michael kaus |
There are only two pots inside the amp. One is for trem adj and the other is bias voltage control. You basically have a master bias control and you have to adjust for safe operation with the hottest tube. 23mA then would be the hottest you would want ANY of the tubes to run. That's why I check mine individually. Mike. | ||
| Douglas W. Fink (dfink) Username: dfink Registered: 06-2007 |
I would save some money and buy the EL-34's from Eletro-Harmonix...From Tube Depot (http://www.tubedepot.com/)...I just got a set for my mid-70's 210-sixty-five and they rock. And yes, make sure to get your amp biased for longer life....Keep rockin' |