Traynor YGM-3 (early) - Selmer cab

[Barks]

Hi all again.

So far so good, it seems to be holding up. All generally sounds good. I detect the amp is a smidgen quieter - so hopefully it will still cope on a two guitar bass/drum gig.

I've been contemplating a fan installed to help keep the valves cool - a small PC type maybe than could also run off the 6.4 heater supply?

Also, regarding fizz in the decay, I found this which relates to 18 watt EL84 amps. Is it possible this could relate to the Traynor?

http://www.18watt.com/storage/18-watter ... fo_311.pdf

[Leo_Gnardo]

Also, regarding fizz in the decay, I found this which relates to 18 watt EL84 amps. Is it possible this could relate to the Traynor?

http://www.18watt.com/storage/18-watter ... fo_311.pdf

Thanx for that link Barks, veddy interesting! Bring on the zeners.

[rp]

Here's some fan info: http://www.blueglow.de/FenFan.html - remember that fans aren't a free ride and draw some current so check that. That PT has a free 5V tap, no? Maybe a fan off that?

Looks like you are just going to have to try the zener trick. Never played that Traynor model nor a fixed bias EL84 amp, but IME with classic EL84 amps is that they are all a little thin but not particularly fizzy, so it can be done w/o snubbers and zeners. Fender offered a Blond fixed biased Tremolux for a few months then decided they didn't like it.

[martin manning]

I guess it's better than it was before the PT change and bias adjust?

One thing that bothers me about the P Ruby write-up is that he built two amps to same circuit, but only one of them had the problem. That makes me think that the Zener fix is covering for some other shortcoming, perhaps the OT that was used in the conversion amp.

If the trailing fizz problem in the Traynor is due to bias excursion, there are some other things to try, like reducing the value of the PI coupling caps or increasing the value of the power valve grid stoppers.

[Barks]

Thanks Martin and RP

Yes, I feel it is much better than before. I am very happy so far.
As mentioned, overall it is tighter and sounds good.

The fizz was always present in the amp - even though I want some in there -it always felt just a little too much. It is diagnosing where it is coming in and attenuating it a bit.

I hoped getting the power section better would resolve that but it hasn't really - though I am happier I've done this PT knowing how incorrect and potentially risky the old one was.
It's all a positive process of improvement. Sonically and safety.
Not to mention what I have learned in general. How PT's work, Filament v and Plate v, Biasing and plate dissipation, irregular outlet voltage etc.
It's even adjustable bias now!

I've been doing some more research and higher plate resistors seem to be implemented/recommended so this is one area I can try - now that I have a good stock here.

Another one is to change the 6k8 and 470ohm resistors in the PI to higher values to increase headroom a little bit.

There is no harm in trying, and I'm a lot more confident to attempt it now.
I remember Miles questioning the size of the PI coupling caps (the 400v 0.1?) at the beginning of this odyssey.

[martin manning]

Yes, the 0.1uF that couple the phase inverter to the power valve grids. You will lose some bass if you reduce those, but you could try 0.047uF there. The other possibility is larger grid resistors, the 1k5's on the board that connect to the EL84 pin 2. These could be quite a bit larger, so maybe you could try 15k to see if there is a positive result. Maybe just add them right at the socket pins (which is a good place for them anyway).

Does the position of the tremolo intensity pot have any effect on the fizz?

[rp]

I've been doing some more research and higher plate resistors seem to be implemented/recommended so this is one area I can try

You must mean screen resistors, no need to mess w/ any plate resistors here, though if you do a Vox-like PI you might want to change that 82K to 100K. Not sure how much it really matters.

I remember Miles questioning the size of the PI coupling caps (the 400v 0.1?) at the beginning of this odyssey.

Those are sought after magic mojo tone caps (google mustards) so don't chew them up or toss them out. Save them if you ever want to put them back.

Check your speakers that it's really an 8R load. Should be two 16R speakers in parallel. That OT according the schematic only has an 8R tap. A miss match could make the tone brighter fizzy and at these voltages could really stress that little OT and tubes.

[Barks]

Yes, sorry. I meant screen resistors. Spot the newbie/rookie terminology error.
RP, you mentioned 1K here so I may try that.

The PI resistor change is recommended as follows. 6K8 to 47k, 470ohm to 1.2K

Thanks again for all the extra info.
Martin - I'll check again later if Tremolo Intensity effects anything

[Barks]

sorry meant to add:

The speakers are both 16ohm. They measure slightly less than that on each. They are in parallel and give me 7.2ohms.

[Barks]

Does the position of the tremolo intensity pot have any effect on the fizz?

Just checked - no real difference. At volume the tremolo only starts to kick in during the decay portion.

[Barks]

First post PT transplant gig done.

Keys (Rhodes) and Guitar via Copicat.
Funk/Calypso/reggae and latin-infused jazz.

Perfect.

No issues or noise.
Responsive and loud enough at 4 on the dial.
Tighter bass and cuts through.
Plenty of good comments about the sound and the engineer was lauding the sound of the guitar. Even at 4, I could get a bit of dynamic crunch without it feeling like it was compressing.

Only issue was picking up mobile phone "morse code"

I've recently also done the the resistor change in the PI mentioned above and it is much more smooth, fat and crisp when pushed.
Next will be to look at upping the 1.5k resistors pre power valves.
Also upping the grid resistors.

Next week Manchester Jazz festival.

Pretty happy!
Thanks again for all the help !

[martin manning]

Great, glad to hear it!

The PI mods got you a cooler bias on the PI, and less PI headroom, thereby less drive into the EL84's- maybe a good thing. The PI balance is may be further off now with the 82k/100k load resistors (they could both be 100k), but that depends on how well balanced the two triodes in the PI tube are too.

[Reeltarded]

I like upping stoppers on the output. I think bypassing the inverted side of the PI with 100p is another good idea.

[Barks]

I think the PI is something i need to understand better.
It looks pretty symmetrical on the scheme, but why is there and 82 and 100 there? Why not the same?
I also understand there are a few different implementations - such as Long Tail?

I need to go hide in a learn zone now!

[martin manning]

Yours PI is a long-tail pair, and yes it's deceptively symmetrical looking. You can read about it here: http://www.valvewizard.co.uk/index.html and here: http://www.aikenamps.com/index.php/white-papers
The two sides do not naturally have the same gain, so the plate load resistors are miss-matched to balance them a bit better.