Two-Rock Ruby issues(Ghosting)

[sean]

Hello,
I am new to this forum.I'm also not a tech.I hope to learn quite a bit from everyone.I own a Two-Rock Ruby 12/18 watt amp.I bought this amp new some time ago.There seems to be an issue with it.I hope someone could shed some light on it for me.There are ghost notes(or doubling)that are most noticeable on the G,B and high E strings.The G and B seem to be the worst. Two-Rock has looked at the amp and told me there was nothing wrong.I was told the ghost notes were normal for this circuit(T'wreck express).He suggested I try to mismatch the impedance.I did.The cab I use is a Two-Rock 212 cab with the TR-1265 speakers.The cab is 8 ohms.
When I put the amp to 4 ohms the ghost notes get worse.When set to 16 ohms the ghost notes are greatly reduced.Bill told me I could run the amp at 16 ohms into an 8 ohm load with no problems.Can someone
please explain what is happening with the amp.The tubes are fine.Conecry is not an issue because of the TR-1265 speakers.I need some suggestions.Thank you in advance for your time.
Regards,
Sean

[Allynmey]

Hi Sean, This could be a filtering issue or a layout/capacitance parasitic Oscillation issue. Take a couple of pics of the guts and post them here. Layout is key in this circuit and some have made clones with the right circuit schematically and they don't sound right. Let see the layout in a picture and we can start there.

Allynmey

[sean]

Allynmey,Thanks for your reply.Here are some photos.I could take more if needed.Thanks.
Sean
[IMG:512:384]http://i46.photobucket.com ... jpg[/img]
[IMG:384:512]http://i46.photobucket.com ... .jpg[/img][IMG:384:512]http://i46.photobucket.com ... .jpg[/img][IMG:384:512]http://i46.photobucket.com ... .jpg[/img]

[Funkalicousgroove]

I had a similar problem with a Rocket Clone I built, I ended up adding ALOT of filtering as well as changing my ground scheme. Where are you Located? maybe one of us could take a look.

[Robert]

Sorry to see your having trouble and got little help from TR. Check out the Dumble forum post about '"ghosting" for a couple clues. I'm sure your not the only one experiencing this problem. You might find discussion on some of the other amp forums.

Bill told me I could run the amp at 16 ohms into an 8 ohm load with no problems.

This seems contrary to what was discussed recently in the Dumble forum about speaker matching where several members suggested the opposite was safe. My reading of their posts, see "Speaker matching", would be that it is safe to use a speaker with 2 times the ohm rating of the OT tap you use it with. I thought the other way around as you quoted Bill was a big problem for the OT.
From the venerable Dogears where he suggests an 8ohm speaker into a 4ohm tap,

I always check 8 into 4 and see how I like the tone.

and Harris,

You can also safely use an 8 ohm speaker with a 4 ohm tap as well.

and Bob-I

a 2:1 mismatch on impedance is acceptable

[Chris G]

Sean,
This may not have anything to do with your problem,but in the pictures,it looks like you have a bad solder joint in the power supply,In the second picture, right above the power supply caps,the second connection in the string of diodes closest to the supply looks unsoldered. might just be the pictures but I would check it out.

Chris

[krash]

running a 2:1 mismatch, in either direction, is probably ok for most tube amps.

The impedance gets reflected back to the tubes. So if you have a 6K pri OPT and you run it on half-load, it'll be running the tubes into a 3K primary impedance, which just changes their operating points but doesn't really make it unsafe. Might sound bad. Might not. 2:1 in either direction will be fine.

I always check my hifi amps with both mismatches (both directions) for my preference in tone and how they interact with speakers. I find that a running, say an 8 ohm speaker on the 4 ohm tap makes for a tighter, brighter, and more hifi-ish sound, while running the 8 ohm speaker on the 16 ohm tap makes for a looser and rounder, more euphonic kind of sound. I have run it both ways for very long extended periods of time in a lot of amps with no problems and in fact I have an amp with 64 ohm OPT taps that I have run for years on 8 ohm speaker with no ill effects (that's a 8:1 mismatch).

[Allynmey]

Sean, is that an effects loop I see? The Express layout is very fickle about grid wire length. You may be picking up an oscillation from that circuit. I also see what ChrisG is talking about. The wires in front of the EL34's look like they have one of the grid wires running parallel in a group with power and heater wires for about 3 inches. That might also be an issue. I can't seem to enlarge the pics for a better view.

Allynmey

[sean]

Sean, is that an effects loop I see? The Express layout is very fickle about grid wire length. You may be picking up an oscillation from that circuit. I also see what ChrisG is talking about. The wires in front of the EL34's look like they have one of the grid wires running parallel in a group with power and heater wires for about 3 inches. That might also be an issue. I can't seem to enlarge the pics for a better view.

Allynmey

Hi,Yes,there is a tube buffered effects loop.Via a switch it can be in or out of the circuit.The gosting happens either way.This Ruby is an 18 watter that is pwered by EL-84 tubes.The ghosting is very minimal with the amp at 16 ohms into an 8 ohm cab.The amp has a bit more clarity and punch this wat too.


Thanks to all of you for your replies.
I would like a tech that is familiar with the Express circuit to look at it or send it back to Two-Rock again.It is frustrating because this amp is amazing save for the ghosting.I'm about 1 1/2 hours North of Austin Tx.Any recommended techs in that area?What questions should I ask Bill at Two-Rock if I do send it back to him?
Thanks,
Sean

[sean]

Here is a different view of the amp.[IMG:384:512]http://i46.photobucket.com ... .jpg[/img]

[sean]

I added a different photo view of my Ruby in the above post.Can anyone tell me why the ghosting is greatly reduced when I mismatch the impedance(amp set at 16ohms into a 8ohm cab)?I would be grateful for any help.

[tubedogsmith]

What are the resistor values in the PI? What value is the cathode resistor for the output tubes, or is it fixed bias? Put up a pic of the trannies. These things should have "NO" ghost notes at all. I've rewired a few of them and heard lots of weird noises in them when I first got them but ghost notes weren't in the mix. The extra gain stage/loop thing can be a problem. If you know what you're doing poking around in an amp measure the voltages on all the plates and post them.