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
5,298 posts
 
rodman99999....that's very nice of you!  Those are very decent tubes, so @n80 should hear an improvement with those.

I love this community!
n80 OP
2,133 posts
 
@mofimadness : Very nice indeed. I am often taken aback by the kindness of folks I don't even know. I hope to be able to pass on such kindness in the future.

Now I am a little worried about whether I will hear a difference or not as I don't have a lot of confidence in my ears. I will have my wife listen with me.

@rodman99999 : I have PM'd you my address.

Now that I'm actually going to get to try tube rolling I have some questions: 

Access to the internal of my LS-16 is easy. Just a few screws. I'm assuming the removing and replacing these types of tubes is just a straightforward firm pull up to remove and firm downward pressure to install.....no twisting or locking?

Wear gloves to keep oil, etc off the tubes?

When I Google tube changing the issue of biasing comes up, mostly with guitar amps. Is this something I need to worry about with my pre-amp? The manual does not say anything about that.

My pre-amp uses four tubes. Someone said above that I should be able to tell some difference with just two but I'm not sure where to put the two replacement tubes. The layout is like this:

          V1   V2
          V3   V4

Apparently when new the tubes are actually marked V1-V4 for exact location.

If I hear a difference with two will that difference by more pronounced with a full set of four?

If I like what I hear with two of these tubes and decide to get two more how precisely do they second two need to be matched with the first two? Is it okay to buy the same brand and designation or will they all four need to be tested and matched?

Sorry for questions that might seem obvious but this is new to me.

George


mofimadness's avatar
mofimadness
5,298 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
5,298 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...
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