Traynor YGM-3 (early) - Selmer cab

[rp]

Maybe you've already found, but here's two useful posts that might help, One is the 'famous' conjunctive filter, the other the 'famous' fizz cap. Never tried the conjunctive filter, seems to have been invented originally to snub a ringing OT, I doubt that's a problem with a limited bandwidth MI OT, and with all the 'blanket over amp' comments I would save it for last. I'd try the least harmful IME, the 47-100pf across the PI plates, and if you have some instability this would be where to snub it first, I believe. Then the smoothing cap across the LTP top plate resistor that's so popular it's called the 'fizz cap'.

I dislike all these things, you loose the best part of the treble - the 'air' the 'sparkle' but live in a club, with a loud band, with fuzzed-out ears, I doubt it matters. Still, when I look inside an amp and see snubbers I wonder what's up, like when I see too much shielded cable or, bless us all, both.

http://el34world.com/Forum/index.php?topic=12723.0
http://el34world.com/Forum/index.php?topic=7620.0

[xtian]

One thing that occurs to me is the nature of the speakers.

Oh, man! If you have not actually played this Traynor through different speakers, hold everything until you do.

[martin manning]

This amp has a fizz cap across the PI plates, and I believe increasing it was tried already. It has screen resistors added too.

I'm still puzzled by the alleged low primary impedance... The load line runs through 300% of max plate dissipation.

[Barks]

That's correct Martin - we upped the fizz cap and added screen resistors.

I've a Peavey Classic 50, 2x12 which can act as a cab as its 8ohms

I'll set up mics and record a 'before and after' tomorrow for analysis

[martin manning]

Barks, if you get the chance can you get a hi-resolution photo of the inside of the chassis looking straight in and showing the entire length?

[Barks]

Barks, if you get the chance can you get a hi-resolution photo of the inside of the chassis looking straight in and showing the entire length?

Hope these help. I seem incapable of taking good photos with this iPhone.

Also attached are two recordings of the amp at same setting with LesPaul in bridge and mic setup about 3 feet back.
Only caveat is that the Blue Marvels are pair 8ohm speakers in series wheras the Goodmans are pail 16 ohms in parallel - so the Traynor has to work into 16ohm load with the Blue Marvels. So this may null the comparison.
One thing I can try is running the Goodmans from the Peavey as it has an 8ohm output option

The Blue Marvels are darker - which is how the Peavey comes across anyway - but I can still hear the fizz in there.

[martin manning]

Photos are great. The flat light makes it easy to see details. I don't hear the fizz on a single note like I did before on either recording, it's not nearly as noticeable to my ear. The final chord is fizzy, and sounds like blocking distortion. What do you think?
On laptop speakers I can hear the darker tone of the Blues, and other than that the impedance match doesn't seem to be making much difference.

[Barks]

Thanks.

Its interesting, as when I play and move to the side of the amp, or into the next room it becomes more noticeable.
Either way its still a great amp - I'm going to try the Peavey amp into the Goodmans as it has both 8 and 16 ohm outputs - might be great!

I assume blocking distrotion will be solved by upping the grid stoppers on the powerstage?

Can I try increasing the GS on the preamps?

[martin manning]

I assume blocking distrotion will be solved by upping the grid stoppers on the powerstage?

Larger grid stoppers on the power stage can delay the onset of blocking distortion at that location, but the fizziness on the final cord in the recording above might be coming from the preamp.

Can I try increasing the GS on the preamps?

Yes, but there will be roll-off of HF. See here: http://www.valvewizard.co.uk/gridstopper.html

[Barks]

Thanks again!

One thing I'm reading - and understand from explanations at TAG - is that the grid stopper needs to be as close as possible to the valve base.
So - when looking at my layout on the first generation YGM and later YGM generations, Traynor moved V1 to be close to the input jack - whereas mine is on the other side.
I could try moving the present 68k resistor so it is at pin 7?
I wonder if V! this change was to get rid of some of these issues?

later revisions:

reground.jpg

mine (early):

file.php.jpeg

[martin manning]

The grid leads going from the input jacks to the first stage don't look bad the way they are, but you could push them down against the chassis. The second triode doesn't seem to have a grid stopper anywhere close, though. If so that might be something to try. I don't have the schematic at hand but I'll look later.

[martin manning]

No V1B grid stopper on the schematic. You could add something like 10-20k and see what that does.

[Barks]

Thanks Martin.
Will report back.

[Barks]

OK.

I tried a 6.8k that I had spare from the PI mod I did - mentioned in a previous post.

No difference to fizz, but noticeable drop in "air" to the sound and slight overall level drop( though this may be subjective as I was a little despondent that no change to trailing fizz!)
With that in mind I don't see the point of trying a higher value at this point?

Next step is to try and draw out onto the original scheme the mid range boost circuit that was added 20 years ago - though not convinced, as all this is between the first and second stage of V1.
This incorporated an inductor and pot (in input 3 position) and various bits around the tone stack.
Incidentally the first version of the YGM-3 had the tone stack built directly onto the bass and treble controls, but later variants onto the actual boards.

[martin manning]

Is that mid boost still in the circuit? If so you could try bypassing it (revert to the original schematic) and see if that is causing any problems. Re the in reader grid stopper, if that detracts from tone and doesn't solve anything then put it back.