2. amps-preamps
  3. 147225-115924

Tube Rolling for Pre-amps?

I have an Audio Research LS-16 that feeds a Madrigal Proceed HPA2 solid state amp. 

I did not choose this equipment; it was given to me. From what I can tell the original owner spent a good bit of time matching up these two components with the speakers, Aerial Acoustics 7Bs.

The tubes in the AR are original. Probably 10-15 years old? But with an extended period of not being used.

The system sounds good to me. I don't need to change anything.

However, I've been told that the tubes are old and may need to be replaced soon. I've also read a little bit about tube rolling but most of the articles I've seen talk mostly about tube rolling with amps and not pre-amps.

So I have some questions:

1) If the original owner wanted a system that sounded like a 'tube' system, why not have a tube amp and pre-amp? Does it make sense to have a tube pre but SS amp?

2) Other than outright failure, how will I know if my tubes _need_ to be replaced?

3) With a SS amp, will changing tubes in the pre-amp have a noticeable impact on SQ? In other words, is tube rolling for a pre-amp played through a SS amp a thing?

4) For someone like myself who is happy with the system and who is also easily frustrated by A/B testing is tube rolling the pre-amp even worthwhile? I can almost always hear a change when comparing various components but only rarely am able to say A is better or worse than B.

( I probably can't even articulate effectively what I look for in terms of SQ except that I like the bass to be tight, precise, well defined and not boomy. I do not like the music to be overly bright or tinny. I like depth and lushness but not overly warm. Not sure if these are things you alter with tubes.)

Thanks for any advice.


n80
mofimadness's avatar
mofimadness
5,290 posts
 
The tubes that the LS16 uses are 9 pin.  Once you turn the tube over, you will see that there are in a circle pattern with a gap between.  Align that gap with the gap in the tube socket and push down firmly until it seats.  I usually will put in and pull out a tube several times to make sure that if there was any residue on the pins, it gets scraped off with a few rotations.

I wear gloves, I was always told that the oil from your fingers will make the tube burn uneven, but Kevin Deal, (probably knows more about tubes than anyone I've meet), says that's bunk.  I still wear them.

You do not normally bias a preamp tube.  So no worries.

This is me, but I would always replace all (4) tubes at one time and all need to be the same.  Yes, there are exceptions, but mixing tubes in this matter, often leads to poor performance.  (I am talking about the OP's ARC LS16 preamp and nothing else because I know that it can vary widely, but this pertains to the LS16).

So yes, get the tubes as close to each other as possible.
n80 OP
2,133 posts
 
@mofimadness : Thanks. I also have some deoxidizing spray that I used to clean and repair the pots on my old receiver. Should I apply this to the pins?
mofimadness's avatar
mofimadness
5,290 posts
 
I also have some deoxidizing spray that I used to clean and repair the pots on my old receiver. Should I apply this to the pins?

I have always been told not to do this.  I tried something many years ago and it ruined not only the tubes, but the tube sockets had to be replaced.  I don't remember what it was, (might have been "TWEEK").  I'm sure others have had different results...
n80 OP
2,133 posts
 
What I have is DeOxit. Probably no reason to use it if the pins look good.
rodman99999
6,206 posts
 
There’s no need to match all four, only two between channels(ie: V1 closely performance/readings matched to V2 and V3 needs to match V4).  Nor do tube manufacturers need to be the same, between V1/2 and V3/4. ie: If you like the warmth/sound of whatever two tubes you’ve installed(ie: say these Amperex, in V 1/2), and don’t want any more warmth, you’d want to find a tube that adds no more warmth, or- just leave the original pair alone(in V 3/4). When there are multiple tubes, in the same circuit/channel, it’s common experience, that using different tubes will reinforce the better qualities of each tube and minimize the weaknesses. I’ve not heard of the LS-16’s circuit responding differently(personally). Gold does not oxidize and I’d appreciate it, if these pristine gold tube pins weren’t repeatedly pulled in and out of a socket. Installing them, in either the two positions/sockets closest the rear, or the two closest the front of the unit, should tell you what you need to know. A two-fingertip grip, as close to the base of the tube as possible, pulling straight up and two at the top, pushing straight down, has always worked for me(no bent pins or widened sockets). A cotton glove or sock(pulled over the hand), would be nice/can’t hurt(it’s what I do). I’ll have them on their way to you, tomorrow.
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