Having some distortion issues with an Ultimate Attenuator

[AaronGTR]

I just recently acquired an Ultimate Attenuator and I've been having some issues. I am playing through a Dr. Z Stang Ray and whenever I crank my amp up, it begins to lightly breakup at around '4' on the volume knob (without the attenuator). When I turn the attenuator on and turn the volume to '3' on the amp, I get wayyyyy more gain then I ever could out of diming the amp sans attenuator. Also, it is really noticeably dulling the sound out and bumming a lot of my high end. I have the latest version of the UA and I've been keeping the 'bedroom' and 'plexi' switches in the off position - turning 'plexi' on makes the problem much worse. Does anyone have any idea what may be causing the problem? All help is greatly appreciated.

[8len8]

Sorry about that. I've had a UA for a while now without any problems. Maybe the Dr Z just doesn't like the 32 ohm input impedance of the UA. Their web site specifically talks about the custom output transformer so maybe it requires exact matching.

[Blue Strat]

Since the optimum match for the UA is 32 ohms, using an amp with anything lower than 16 ohm output impedance can be hazardous (and may not sound great).

[jboyjams]

If it's not a compatability issue with your amp and the UA (as mentioned earlier), then there's possibly/probably something wrong with the attenuator.
I still own one and had two of them all together.
I'd use it at gigs to lower my volume when using a halfstack Plexi - always 16 Ohms but have run at 8 when testing pulling 2 tubes from a 100 watt amp and didn't notice any issues or added distortion. Seems very transparent to me.

If I couldn't return it, I'd contact Magnus to see about having them look at it (or Ho in Canada).

Also, it'd be helpful to test it on another amp - although I suspect that could be risky if it's faulty.

Good luck with your setup.

[Steve73]

Originally Posted by Blue Strat

Since the optimum match for the UA is 32 ohms, using an amp with anything lower than 16 ohm output impedance can be hazardous (and may not sound great).

Yeah, +1 on this. What is your ohmage set at on the amp? If you are using a UA, set it as high as you can to help minimize the ohmage mismatch. Set at 8 or lower and it will really effect your tone and distortion level.

[jp1977]

are u plugging the amp into the built in variac plug on the back of the attenuator??

[AaronGTR]

Alright, I just had a chance to try all the suggestions in this thread. I had been running the amp and cab at 8 ohms, and experimenting with both the variac and wall plugs. Switching up to 16 ohm really helped with the distortion issues I was having. However, I'm still losing a lot of richness in the highs and lows (and just plain losing a ton of low end and high end). It sounds like the amp is in the closet with the door closed when I attenuate the signal at all. The variac and wall plugs aren't really making any difference as far as the attenuation goes - although it does alter the tone (in a cool way) just by switching the power source. Anyone have a suggestion?

[awardsjake]

I noticed the exact same thing you described...more overdrive with the Ho/Ultimate inline vs. amp without attenuator. It did the same thing with the impedance set correctly on four completely
different amps. I'm guessing it has something to do with the re amping? ...just a guess.
I sold it because of that issue.
Jake

[gulliver]

Might just be the acoustics of your room ... when you play loud, heavy reflections can increase certain frequencies and also create an illusion of increased amp distortion. Psychoacoustics play a large role in the dislike of attenuators. I do like my UA and just sold my Hotplate. It was actually a change that was difficult to get used to, but I feel it is closer to the true tone of my amp and feel the touch/sustain is much more loud feeling than with the Hotplate.

[8len8]

Originally Posted by AaronGTR

Alright, I just had a chance to try all the suggestions in this thread. I had been running the amp and cab at 8 ohms, and experimenting with both the variac and wall plugs. Switching up to 16 ohm really helped with the distortion issues I was having. However, I'm still losing a lot of richness in the highs and lows (and just plain losing a ton of low end and high end). It sounds like the amp is in the closet with the door closed when I attenuate the signal at all. The variac and wall plugs aren't really making any difference as far as the attenuation goes - although it does alter the tone (in a cool way) just by switching the power source. Anyone have a suggestion?

It's likely the amp can't handle the impedance mismatch. Do you have 2 16 ohm speakers you can put in series at the amp output to see if you get the same effect? Maybe go to the local music store with the amp and try wiring it up to a couple 16 ohm cabs in series...

Have you contacted the amp manufacturer or the UA manufacturer? They'll know best...

[AaronGTR]

I got into contact with Mark Gregg. He's answering my e-mails extremely fast and been very helpful. I bought this attenuator off of craigslist and apparently it is the 2 ohm version, which was discovered after Mark had me plug a speaker cord into the "amp" input and test the resistance (it only read 10 ohms). It would have been nice if the seller would have disclosed this tidbit of information when I bought the attenuator. He has offered to walk me through the mod to bring it back to the original specs. He is being incredibly helpful and supportive considering I didn't even buy this unit direct from him. I will keep you guys updated as things unravel.

[8len8]

Originally Posted by AaronGTR

I got into contact with Mark Gregg. He's answering my e-mails extremely fast and been very helpful. I bought this attenuator off of craigslist and apparently it is the 2 ohm version, which was discovered after Mark had me plug a speaker cord into the "amp" input and test the resistance (it only read 10 ohms). It would have been nice if the seller would have disclosed this tidbit of information when I bought the attenuator. He has offered to walk me through the mod to bring it back to the original specs. He is being incredibly helpful and supportive considering I didn't even buy this unit direct from him. I will keep you guys updated as things unravel.

Yeah, Mark has helped me in the past too. I never knew there was a 2 ohm model. If you ever find out from him why the standard model is 32 ohms and not 8-16 ohms I'd like to know...

[AaronGTR]

Originally Posted by 8len8

Yeah, Mark has helped me in the past too. I never knew there was a 2 ohm model. If you ever find out from him why the standard model is 32 ohms and not 8-16 ohms I'd like to know...

He has a bunch of stuff on his website about that. The best explanation I have gotten for that is from a post I ran across by the guy who owns Mojave Ampworks. Here is the link: http://www.vintageamps.com/plexiboar...81179&start=45

[8len8]

Originally Posted by AaronGTR

He has a bunch of stuff on his website about that. The best explanation I have gotten for that is from a post I ran across by the guy who owns Mojave Ampworks. Here is the link: http://www.vintageamps.com/plexiboar...81179&start=45

Thanks for the thread. Not sure if I totally agree with them since increasing the load means the amp's output transformer has to deal with a larger voltage at its secondary winding when it sends current into the UA.

Either way it works, and it (a re-amper) sounds more transparent at bedroom levels (with many dB of attenuation) compared to MASS, HotPlates, or others I've tried.

[Dave_C]

Originally Posted by AaronGTR

I just recently acquired an Ultimate Attenuator and I've been having some issues. I am playing through a Dr. Z Stang Ray and whenever I crank my amp up, it begins to lightly breakup at around '4' on the volume knob (without the attenuator). When I turn the attenuator on and turn the volume to '3' on the amp, I get wayyyyy more gain then I ever could out of diming the amp sans attenuator. Also, it is really noticeably dulling the sound out and bumming a lot of my high end. I have the latest version of the UA and I've been keeping the 'bedroom' and 'plexi' switches in the off position - turning 'plexi' on makes the problem much worse. Does anyone have any idea what may be causing the problem? All help is greatly appreciated.

Running ANY amp with a low output impedance into a high load impedance will reduce its power output (i.e. make it clip sooner) and will soften and darken the tone. The UA uses a 32 ohm load, so even running a 16 ohm amp output into it results in a mismatched load which will change the original tone of the amp. Running less than 16 ohms into the UA is downright dangerous and could damage your amp due to excessive flyback voltages.