Linear Tube Audio Micro-Zotl amp On GR-Research Super Vs.

Rocket_Ronny · « **on:** 31 Aug 2017, 03:59 am »

A friend dropped by the other day and we tried out his Micro-Zotl .75 watt amp on the GR-Research Super Vs. Now he loves this amp and is VERY hard to please and has spent a small fortune on gear over the years. So I was very excited to hear it, as he loves it, even if at lower volumes. He has tried it on small boxed 2 ways, and even though it did not play that loud it sounded fantastic.

With the Super Vs being 98 db and crossing over at 200 hz I thought the amp would pull some real magic. But I did cast a weary eye at that crossover on the Vs. So we hooked up the little Zotl and pressed play. Within 2 seconds it was obvious the amp was puking it's sorry guts out, even at low levels. It sounded thin, stressed, and just broken, bummer!

So there you go, can't go by eff. alone but have to consider the crossover these small amps have to deal with. I would like to hear the higher powered offerings but wonder if I would deal with the same problem.

Rocket_Ronny

Rusty Jefferson · « **Reply #1 on:** 31 Aug 2017, 12:31 pm »

Is it possible the MicroZOTL has more gain than the amplifier you replaced? Did you measure voltage? If it does have more gain, and you didn't adjust the active woofer output appropriately, it (or any amp with similar gain) would sound thin as you'll have proportionately less bass output. If it's only running the coaxial driver from 200hz> there is no reason it should sound thin if the woofers are adjusted to to exact same output. A borrowed MicroZOTL easily drove my 102db coaxial based speakers to comfortable levels (it is only 1 watt afterall) with great bass response. It's necessary to measure voltage anytime doing A/B or A/B/X tests, especially if using active woofers/subwoofers.

Rocket_Ronny · « **Reply #2 on:** 31 Aug 2017, 08:09 pm »

Good points Rusty but that was not it. We both think it can't handle the crossover.

Rocket Ronny

Rusty Jefferson · « **Reply #3 on:** 31 Aug 2017, 08:29 pm »

So, you did measure the voltage of both amplifiers at a given output level of your preamp or DAC? They were identical in gain? You didn't need to adjust the woofer output? Can you explain how you compared them? What is the amplifier you compared the MZ to?

Rocket_Ronny · « **Reply #4 on:** 31 Aug 2017, 09:46 pm »

No, we did not measure voltage. The bass response did not increase on the subs. It was just a quick insertion of the amp into the system due to time limitations. My regular amp is a Tube Research Labs solid state amp, a kind of sliding bias Class A design.

Rusty Jefferson · « **Reply #5 on:** 31 Aug 2017, 10:09 pm »

I don't have personal experience with these speakers. Are there others using them that can confirm the need to adjust the woofer output based on the gain of the coaxial amplifier? I looked at the GR Research website and see what appears to be active woofers or subwoofers for this model. I didn't see a manual link to explain how the woofer amps get their signal and whether they need to be adjusted for gain of the full range amplifier.

glynnw · « **Reply #6 on:** 1 Sep 2017, 12:10 am »

Think of the woofers as a separate sub with it's own controls on a plate amp.. They can take a line level signal, as from a preamp, on the RCA inputs. Or they can get a signal from the amp running the coax by hooking to the supplied binding posts as if it were a regular speaker. Then you simply adjust the output level to match the coax with the volume control on the plate amp.

Rusty Jefferson · « **Reply #7 on:** 1 Sep 2017, 02:10 am »

Okay, thanks. That's what I thought. So if the MZ (in this case used as an integrated) had more gain than the OP's preamp/amp combo, and he didn't adjust the woofers, the system would be bass shy, or thin as he stated. I don't know about his "stressed, broken" comment though. Something doesn't seem right.

Rocket_Ronny · « **Reply #8 on:** 1 Sep 2017, 04:44 pm »

The Zotl was only driving the 98 db eff. P Audio driver that does have a crossover.

What can I say. My buddy and I have been in audio forever and this was sort of new to us. While we have seen electrostatic speakers bring an amp to it's knees I don't think we had come across an amp sounding so broken, stressed and thin, trying to drive a speaker. Now his amp is working fine in his headphone rig, so it's not a permenant thing.

We went from the unbalanced outputs of a Lampizator dac into the Zotl and ran the speaker leads to the P Audio crossover with leads off of the positive posts of the Zotl going to the speaker sub amps.

It's possible we messed up, as it was a quick try of the amp. Just sharing what happened. Very disapointing as I really wanted to hear this amp.

Rocket Ronny

Shakeydeal · « **Reply #9 on:** 1 Sep 2017, 06:58 pm »

I believe you heard what you heard. However, you will have to match the sub amps to the gain of the new main amp. Unless the voltage gain of the two are identical (highly unlikely) there will be a difference in the output of the subs. This may or may not account for the "thin" sound, but it will be noticeable.

Shakey

Dieterle Tool · « **Reply #10 on:** 1 Sep 2017, 08:43 pm »

This string is absolutely useless and should be removed.

-Dieter

lancelock · « **Reply #11 on:** 2 Sep 2017, 12:40 am »

In defense of the Micro ZOTL, I have two of ey sound spectacular as a one watt integrated amp. I have used them to power my Tekton Double Impacts and also my Decware ERRx radial speakers and at 93 db they did a respectable job with decent volume.

The real magic of this little amp is when it is used as a preamp. This is where it really shines. It is the best preamp I've ever owned, probably ever heard. I really suggest trying its preamp capabilities. You will be stunned. I'm using some primo NOS tubes and it really is a tube rollers dream.

jsm71 · « **Reply #12 on:** 8 Sep 2017, 05:24 pm »

+1 on Lance's comments. I suspect using this piece as an integrated amp is its least accomodating form of deployment. I know its been used at shows with super HE horns to great effect however. It was originally, and is still designed as a premier headphone amp. Preamp usage has been a pleasant surprise.

I also am using it as a preamp (with NOS tubes) in front of one their amps. Outstanding.

gregfisk · « **Reply #13 on:** 9 Sep 2017, 02:12 am »

I own Super V's and Rocket's comments are right on. They need way more power than the 97db "at least that's what I think they are rated" would suggest.

I have tried several flee watt amps including tubed, SS and class D and have never been able to really get the P Audio drivers moving without at least 50 wpc. The crossovers being the cause makes a lot of sense and is what I also have suspected all along.

Yes, you have to adjust the subs volume control way down to get a flee watt amp to be an even output and vise versa with a large amp.

About two weeks ago a friend brought over a tube amp with 8wpc. I had to almost turn off the subs volume to get them to match up in output.

And Dieterle, yes you are a Tool.

Greg

tdinut · « **Reply #14 on:** 5 Oct 2017, 12:16 pm »

I have the LTA MZ2 and use it with several different amps. I really love it. It makes everything sound more alive and open. It's an amazing piece and is extremely quiet. It kills preamps many times more expensive, IMO.

Shakeydeal · « **Reply #15 on:** 5 Oct 2017, 03:34 pm »

Quote from: gregfisk on 9 Sep 2017, 02:12 am

I own Super V's and Rocket's comments are right on. They need way more power than the 97db "at least that's what I think they are rated" would suggest.

I have tried several flee watt amps including tubed, SS and class D and have never been able to really get the P Audio drivers moving without at least 50 wpc. The crossovers being the cause makes a lot of sense and is what I also have suspected all along.

Yes, you have to adjust the subs volume control way down to get a flee watt amp to be an even output and vise versa with a large amp.

About two weeks ago a friend brought over a tube amp with 8wpc. I had to almost turn off the subs volume to get them to match up in output.

And Dieterle, yes you are a Tool.

Greg

The power output of the main amp, be it SET or push pull, is not consequential in your scenario. It is the gain of the amps in question that has to be matched, not their output.

Shakey

Tyson · « **Reply #16 on:** 5 Oct 2017, 07:11 pm »

I ran the V2's for a long time and I run the Super 7's now and this feedback is right on - different amps are louder or softer than other amps and it has nothing to do with their power output (watts). It has to do with their gain. ANY time you swap a new amp into the top section of one of these speakers, you MUST re-set your sub/bass volume to match the new amp.

I don't measure the amp voltage. I just put the amp in, measure the speaker output via my microphone (hell, even iPhones have mics you can use nowadays). Adjust the sub volume up or down to get back to a flat response.

Without doing that, there's no way to actually hear the amp properly.

Danny Richie · « **Reply #17 on:** 6 Oct 2017, 06:03 pm »

He guys,

The crossover doesn't impose any type of a load issue on these. In fact there is even an impedance buffer at the front of the network to balance the load. The amp will have no more issue driving the P-Audio woofer with it in or out.

It is quite likely that you guys have an extreme balance issue with that little amp and the servo amp might need quite a bit of adjustment to balance the levels. The gains could be way off.

Another thing that would really help is to use a pre-amp to drive both the little amp and the servo subs via an RCA connection. Ganging up two servo amps plus the speakers on the speaker outputs might be more of a load than the little amp can handle. It just may not have the current capability for those low frequency ranges.

And if you use an inline filter to roll off the lows to the P-Audio driver (placed before the little amp) then it will increase its headroom and dynamics considerably as the low frequency current demand will be gone.

doggie · « **Reply #18 on:** 27 Nov 2017, 02:22 pm »

Quote from: lancelock on 2 Sep 2017, 12:40 am

In defense of the Micro ZOTL, I have two of ey sound spectacular as a one watt integrated amp. I have used them to power my Tekton Double Impacts and also my Decware ERRx radial speakers and at 93 db they did a respectable job with decent volume.

The real magic of this little amp is when it is used as a preamp. This is where it really shines. It is the best preamp I've ever owned, probably ever heard. I really suggest trying its preamp capabilities. You will be stunned. I'm using some primo NOS tubes and it really is a tube rollers dream.

+1

While the MZ2 can certainly drive some speakers directly in a near field scenario it really shines as a preamp and HP amp, especially with NOS tubes. I am using it with the LTA Z10 amp for my Omega Audio 97db speakers and it is remarkable.

Rocket_Ronny · « **Reply #19 on:** 27 Nov 2017, 04:21 pm »

Quote

It is quite likely that you guys have an extreme balance issue

Thanks for chiming in Danny. No, it's was not a balance issue at all. Most of the posts point this out and that is NOT the issue at all. The amp was severely stressed and broken sounding, almost like clipping yet we even tried super soft volumes. Your suggestion of running the subs off the preamp is probably the answer if the crossover is not the issue.
Anyway, none of it matters as it was just a quick little effort to hear the amp and it did not work. I am happy with my Tube Research Labs amp, so no sweat. Just wanted to hear the Zotl as my friend absolutely loves his.

Rocket Ronny