| Author | Message | ||
| John Parker (jparker) Username: jparker Registered: 03-2012 |
Hello all, I'm having a problem with my amp and I'm hoping that someone here might be able to point me in the right direction. I own an early 210 Sixty-five (12ax7 PI version) that has been giving me some headaches lately. Initially, the biggest concern was a marked drop in available volume from the amp (having to crank it up to about 7-8 on the master volume to get a comparable stage volume to a Fender Hot Rod Deluxe on 3-4). It was also not as clean as I felt it should be but I chalked that up to having to push everything so hard. I had the amp retubed (JJ EL34 matched pair) and recapped by a trusted technician (I also pointed him to this site so he definitely knows the idiosyncrasies of these amps and was not trying to bias it like a Fender or anything). That still didn't remedy the problem and we determined that at least a couple of the opamps were faulty. I had him replace all of the opamps with NE5534s (recommended here by Ed Goforth as being Mullard soundalikes) using the Brown Dog adaptors. I now have the volume problem straightened out but am having an issue with the preamp section breaking up way too early. I am getting distortion on the high output setting at any preamp volume setting but it starts getting really pronounced at around 3.5-4. It's much worse on the low output setting. It is not as noticable if I'm using a guitar with low output pickups like a Strat but by primary guitar uses a Duncan Jazz/JB setup. This isn't the only one of these amps that I've owned so I do have a frame of reference as to how they should sound but I'm about out of ideas on this one. I know it's not the speakers as it does the same thing plugged into an external cab. Any ideas on where I should have my tech start to look? Thanks in advance, John | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
Using the NE5543's will give you breakup/distortion alot earlier,they can be a pretty hot op-amp,that's actually why i'm looking to load it into my channel 2 drive,I want a more aggressive sound out of mine.They are great op-amps. | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
sorry 5534's | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
oh, forgot to mention the low/high output inputs are kinda backward to most amps,if you have weak pickups like single coils the low output actually acts like a gain to give those pickups more push,the high gain input does the opposite for really high gain pickups to level them down abit,hope that helps...... | ||
| John Parker (jparker) Username: jparker Registered: 03-2012 |
Hey, thanks for he response. I don't think just having hotter opamps is what's going on here. The preamp is overdriving at any level, even with the volume all the way down on 1. It definitely should not be doing that. Also, this was occurring before the opamps were changed out, it's just that it's still happening, even after replacing all of the usual suspects. What I am referring to with high/low settings are the high and low power switch settings on the front, not high/low gain input jacks. It's entirely unusable for a clean sound on the low power setting at any volume. Any other ideas? | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
ahhh,ok ...Now you are getting a little out of my league,but if it were mine with this kind of prob ,I'd say there is probably a cap/caps that has went bad,hope maybe Mike or Ed will jump on this as well... | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Are you SURE that the driver tube doesn't have one side gone? I think you are just going to have to scope it and follow the signal through until you find where it goes up in smoke. I just had one JJ 12ax7 that one side went crazy and was producing four times the signal as the other. IT was distorting badly. Mike. | ||
| John Parker (jparker) Username: jparker Registered: 03-2012 |
It's not the PI tube. I swapped the (new) one that was in there from the recent retube with a couple of others that I know to be good and had the same result. Here is another possible clue that might mean something to someone with more technical knowledge than myself - when the preamp volume is turned all the way down to zero and the master volume is turned up to any level you still hear the raspy, nasty, ugly distortion where there should be dead silence. The character of this distortion is something similar to what you would hear from a blown speaker in a really cheap stereo. This gets LOUDER (by like, twice as much) when the low power switch is engaged. Turning the preamp up to normal levels brings in the beautiful, clean MM tone that I am used to but still with that despicable grunginess sitting on top of it, taunting and tormenting me. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Does it do it on BOTH channels? | ||
| John Parker (jparker) Username: jparker Registered: 03-2012 |
It does not put out a distorted signal when the volume is all the way down on the first input section, it's only doing that on the second section. It does break up at any audible level on both input sections, though. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Sounds like you are going to have to trace a signal through. Do you have any kind of cheap small practice amp around to use as an amp? If so, you can build a pseudo signal tracer and go from there, IF you are comfortable with working around HOT amps. Go here" http://www.tedsforums.com/forum/index.ph p?topic=8797.0 and read this. It will tell you what you need to get to build it(no brainer). I either use a signal generator and my scope but if it distorts like you say, you should be able to hear it when it goes south. you really need to look at the signal as it goes through and see WHERE it starts to take a dump. If it's in the finals, there really isn't much there other than the tubes themselves, the bias setting and those crappy diodes on the tube sockets. Hmm, come to think of it, look at those too. If it leaves the power tubes clean and you're still getting it, you MIGHT have an OT toasted. |
Tue, 03/25/2014 - 09:53
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