Transformer Burn-in - It's piss'n me off......

John Chapman · « **on:** 6 Jul 2004, 09:51 pm »

Hello!

Recently a few folks (including Zybar here in the forum) reported hearing quite a change in the pre-amps sonics as they burned in - even after the short burn-in I give them here. This got me wanting to test this burn-in thing some more......

I had not listenned to the burn-in cycle of a tx102 since the first pair I got here. At that time I heard more of a change than I ever did on other gear before. Up till that time I saw burn-in as a maybe kinda thing and felt it was as much 'getting used to the sound' as real. The fact it really does seem to be there is distrurbing to the engineer in me...... On the other hand at a very low level there is a mechanical event of sorts when these things run so the fact it changes maybe should not be so surprising. There is more of a case I think for burn-in affecting sonics on transformers than on just wire - for example.

Since that first time I heard the fact burn-in was real I started burning in pre-built units here before I even listen to them so I have not really stayed familliar with the sonic changes.

Zybar's experience and some other reports from folks that sonics kept improving after the burn-in here made me think it was time to have another look at this burn-in thing. The other thing that spurred this along was recent testing of copper vs. silver (post on that will come right after this one). The differences between them are subtle enough that comparing units with different burn-in levels makes the test largely invalid.

Bottom line is that I heard things open up considderably after putting another 100 hours or so on the transformers. There is a more transparent presentaion after burn-in.

This presents a problem - at least now when I am just trying to catch up and so I am shipping more units than typical. I can't have them here for 200 hours each after I finish contruction. Folks have been waiting long enough!

I spoke with Jonathan at S&B (who - like me- is a bit skeptical about burn-in in general) and confirmed it is safe to burn them in at a higher level - BUT NOT TOO HIGH. I now use a signal about 30V Peak to Peak on the primary and with a lowish 350 ohm load on the secondary. The signal (either a fry cleaner output or a sweep on a signal generator 30hz to 100khz sine wave - sweeps every 1 second) is fed to the tx102's via a small integrated amp and then - just before the 102's - through some large folm caps to block DC. I think this way I can do a few days of that here and then test and ship them. For those that have not had the intensive burn-in please don;t worry about it - your pre-amps now have enough hours on them that they will be there or well on there way there.

Two important points if you are temped to try this at home on your scratch built tx102:

1- Use a cap after the amp to block DC (I used 100 uf 200V caps) or you risk magnetising the core of the tx102 - this is a bad thing to do!

2- Put a scope on the primary and secondary to confirm you are not clipping or distorting the waveform. If you go to high you can clip the amp or saturate the core and this is also a bad thing....

Do not use one of the aggressive cable burn-in boxes they will most likely cause problems with the transformers. Basically unless you understand all of the above just put your pre-amp in your system and listen to it for burn-in. I don't find them all that bad right from the start!

Many Thansk!

John

zybar · « **Reply #1 on:** 7 Jul 2004, 12:19 am »

John,

Thanks for the confirmation that it isn't all in my head!

I had some friends over this past weekend and they all said the system was sounding great. A good chunk of that improvment is the NOH preamp.

It absolutely paints a crystal clear picture of the muisc and I love it!!

I can safely say that two pieces of gear aren't going anywhere - the NOH preamp and the RM 40's.

George

Marbles · « **Reply #2 on:** 7 Jul 2004, 02:17 am »

Quote from: zybar

John,

It absolutely paints a crystal clear picture of the muisc and I love it!!

I can safely say that two pieces of gear aren't going anywhere - the NOH preamp and the RM 40's.

I totally agree!!!

Doc Jr 8156 · « **Reply #3 on:** 7 Jul 2004, 06:53 pm »

John,
Your post got me worried. I remember when I consulted you about this burn-in procedure, you told me I can hook the NOH on my FryKleaner with a pair of ICs from the output of the FryKleaner then another pair from the output of my NOH to the FryKleaner's reverse output having the FryKleaner in full-strength (+10mv) and the NOH's volume control to the max. Did I caused a problem on my NOH by doing the above for 200 hours? How will I know if my Tx 102s are magnetized? They sound great anyway. Godspeed.

John Chapman · « **Reply #4 on:** 7 Jul 2004, 09:23 pm »

Hello!

Fry cleaner is NOH problem at all. I was refering to cable burn-in devices using very high voltage signals (like 120VAC and a light bulb....) and sometimes (from what I gather) square waves, etc.

Just relax and enjoy......

Thansk!

John

maxlorenz · « **Reply #5 on:** 7 Jul 2004, 11:03 pm »

Hello John:
Sorry if the question is stupid.
I noticed some lubricant liquid at switch selector's contact sites. Maybe this also acounts for "improuvements" in sound as it is removed?
In other words, do I have to remove it?

Mauricio.

John Chapman · « **Reply #6 on:** 7 Jul 2004, 11:09 pm »

Hello!

I know some switches use a coating there (types of oil). Seiden does this - although I never saw enough to call it a 'liquid'! The shallco's always look dry to me - describe which switch and where it is and I'll see what it is.

I do think you are right that switches take a few turns to get the contacts seated in nicely. I leave them on the top setting suring burn-in but give them a spin when i walk by and sometimes will spin a bunch of times before doing comparisons to make sure this is not an issue with a new switch.

Thansk!

John