The Amp Garage

Oops! Indeed. V1b

jabguit wrote: ↑Sun May 30, 2021 11:02 am

Audiodog wrote: ↑Tue May 25, 2021 10:36 pm Importance of 500pf bypass cap on V2A

V2A? I'm not finding a 500p anywhere on any ODS schematic but on V1B - is this what you meant?


cheers,

Only 3 of 10 measured good. The others were low. I would get the 510pf. To make sure they are big enough. So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Sk...

This.

So I just got a package of NOS 500pf ceramic discs. I did an experiment and compared three Draloric 220k resistors bypassed with three different brands of 500pf ceramic discs in my 700v Bludo Skyline. All measured within 1% of each other. All three caps sounded very different. It even effected the l...

I see a lot of lead dress issues. First, separate the plates and grids. Some say it doesn’t matter, others say it matters a lot. I had oscillation symptoms that were directly related to this. There is no reason to have them touch, ever. Make sure there is space between them. Next, keep the wires fro...

Me too. Certainly seems that way. I keep hearing about high end but the difference I hear is in the low end when moving the grid wire away from the plate wire. I am going to go with phase cancelation of low end from proximity of the wires as that grid wire is so sensitive. I don't feel very enlighte...

A few things I see…. First, have you tried a 150k slope? Rare to see a 100k with a skyline. I use the 150k. Or maybe go with a 100k and .047 mid cap. Also, I would use a 500pf cap on the 220k resistor on V1b. It does effect the knee of what is bypassed in an audible range. I feel the 470pf is the la...

I have a theory…. What if the issue is caused by the vibrations. Moving wires with chopsticks is not the same as 100-300hz cycles. Specific touching, combined with specific vibrations, causing some sort of oscillation or other issue with that lead dress. Maybe being in a combo adds to the issue. I a...

To be clear. The amp that had the problem, similar to Gil’s oscillation description, is a high end clone from a respected and major builder. Built to exacting specs. All parts measured, oriented, etc. I changed all the tubes after getting it here. Power and preamp. Still had the problem. Adjusted PI...

No need for sarcasm…. The amps were indeed unplayable. Pumping volume makes for unplayable ( the Ceriatone). The other one had a wonky bass control and horrible shrillness on top. Guy spent hundreds sending the amp here because it was unplayable. Really bad sounding. Either I am an idiot or a liar. ...

My amps are Teflon. Could be the jacket shielding against the induction when touching. This is a bizarre thread for me as the effect is so extreme that the amps effected were virtually unusable in OD mode. Maybe the wire brand and type matters? The amp I tested has 22 ga. UL1015 600V PVC stranded to...

Neither of those pics you posted have the wires touching, Touching bad. The gap can be used to tune response, as noted. Touching can cause all kinds of mayhem at high volume.

Exactly! Touching is super noticeable. Not subtle. Even a tiny gap fixes some of it. Then as you note, you get a fattening and sweetening with more spread. Just before this topic came up I was playing around with that OD grid wire. I hear a big difference when the wire is elevated all the way from t...

Can’t explain…. I have always heard a slight fattening by paying attention to that area. In a couple cases the amp was so bad that the owners shipped to me or drove it here. The fix was the lead dress both times. Not subtle nor needing a double blind. Maybe the wire brand and type matters? I have tw...

The issue was the increased bass that caused more of the inductive feedback. It was directly related, After hours of parts clipping in and other things I tried, the wire was it. Had the same thing with a Ceritone I mentioned. I even notice a change in feel and tone if you push CL2 coupler towards th...