Harsh, square sounding amp, advice?

[samdjr74]

Hi All,

I posted this on the gear page but thought this would be a better place for this question. I have a 1974 Traynor Reverb Master head and the amp works great but when I use the master volume to overdrive it the sound is harsh, cold and square. My question is if I change the preamp tubes could I possible get a rounder, warmer sound out of the amp? If so what brand and type would be a good place to start?

Thanks,
Sam

[David Root]

With the treble boost in or out? With the reverb in or out? And what settings on both the volume and master? Is the speaker original or has it been replaced?

This amp uses 6CA7 power tubes which are not to everyone's taste (American design EL34).

Also, how long ago did it have the filter caps replaced?

Pete Traynor was a good designer so if it doesn't need a cap job and there are no other bad parts in it I'd say you either don't like 6CA7s or you don't like Traynor amps.

You could try 5751, 12AY7 or 12AT7 in the V1, and/or in the phase inverter (V4). I would try 12AT7 in V4 position.

[Andy Le Blanc]

had a traynor a while back... and my impression was much the same....the screen grids are fed thru a common 470 ohm resistor.... try installing a second so each has its own.... I also remember changing some of the circuit values to more closely resemble a fender... have fun ...

[samdjr74]

With the treble boost in or out? With the reverb in or out? And what settings on both the volume and master? Is the speaker original or has it been replaced?

This amp uses 6CA7 power tubes which are not to everyone's taste (American design EL34).

Also, how long ago did it have the filter caps replaced?

Pete Traynor was a good designer so if it doesn't need a cap job and there are no other bad parts in it I'd say you either don't like 6CA7s or you don't like Traynor amps.

You could try 5751, 12AY7 or 12AT7 in the V1, and/or in the phase inverter (V4). I would try 12AT7 in V4 position.

Hi David,

1. treble boost out
2. reverb in at 5
3. volume at 10 master at 1
4. The speakers are original marslands and the cabinet is a traynor 4x10.
5. The cabinet was checked out a few months ago and what ever needed replacement was taken care of.

Your the second person to mention the 5751 so I might just give that a try. The amp sounds great with a clean signal but it's dirty sound isn't to my liking. I thought because it has a mater volume that I'm really using the preamp tubes for gain and trying something different would help.

Thanks,
Sam

[David Root]

How does it sound with volume at 6 and master at 6? I say that because the master is a very simple type that does not sound good at 1.

It also does seem that (and I didn't look at this closely before, but should have) V3B is an oddball distortion stage and you might want to try something with that.

I modeled it on TubeCad and it appears to be running about 0.2 mA, with a theoretical gain of 59, but with such a low plate voltage and being in a non-linear area of the plate curve, it would give rise to heavy distortion.

In a way it's similar to the Marshall 100k plate/10k cathode stage BUT the Marshall operating point is at about -3V bias, this is at -0.5 or so. i.e. opposite ends of the plate curve, and more importantly the Marshall has NO cathode bypass cap, its gain is about 10 and current 0.29 mA.

I would try disconnecting the 25 uF cathode bypass cap on V3B, just lift the ground connection, this will drop the theoretical gain from 59 to 18 and just might make your problem go away right there.

If you still don't like the tone you could change it to the Marshall 100k/10k, which is not particularly radical by today's standards for a distortion stage. For a Soldano touch use the famous 39k cathode resistor.

Also, Andy's point is a good one. I would go further and put a 1k 5W resistor on each screen.

[samdjr74]

It does sound much better when I mess around with the master and the vollume but then it's getting a tad too loud. I'll look into the V3B cap and see how it turns out, thanks for the info!!!!

How does it sound with volume at 6 and master at 6? I say that because the master is a very simple type that does not sound good at 1.

It also does seem that (and I didn't look at this closely before, but should have) V3B is an oddball distortion stage and you might want to try something with that.

I modeled it on TubeCad and it appears to be running about 0.2 mA, with a theoretical gain of 59, but with such a low plate voltage and being in a non-linear area of the plate curve, it would give rise to heavy distortion.

In a way it's similar to the Marshall 100k plate/10k cathode stage BUT the Marshall operating point is at about -3V bias, this is at -0.5 or so. i.e. opposite ends of the plate curve, and more importantly the Marshall has NO cathode bypass cap, its gain is about 10 and current 0.29 mA.

I would try disconnecting the 25 uF cathode bypass cap on V3B, just lift the ground connection, this will drop the theoretical gain from 59 to 18 and just might make your problem go away right there.

If you still don't like the tone you could change it to the Marshall 100k/10k, which is not particularly radical by today's standards for a distortion stage. For a Soldano touch use the famous 39k cathode resistor.

Also, Andy's point is a good one. I would go further and put a 1k 5W resistor on each screen.