Jeff Rowland model two sounding thin With Mini Utopia


Hello everyone, 

i have been following the forum for years, but never had the chance to have an active participation.
I apologise if there are any errors but english is not my native language, as i am Portuguese.

I have recently added a Jeff rowland model 2 to my system, in order to give my beloved Bat VK60 some res,t due to high hours of usage.

Much to my surprise, the Model 2 paired with the preamp Bat Vk5 and driving JM Lab Mini Utopias sounds quite
"thinner" then the VK60. I don't think it is just the "valve vs transistor" sound diference, and i am wondering what are the causes.

I have chosen the high input impedance 36Kohm and normal 26dB gain to match with the Vk5, and altought have yet to change the pinout of the xlr's (waiting to receive some Neutrik NA3FMX wich is a phase inverter between pin 2 and 3 (BAT uses pin 2 hot and JF Model II has pin 3 hot) i have tried inverting the speakers phase but with no sucess in regard to achieving somewhere close to the sound i had with the VK60.

Everything else in the system remains the same, apart from the power cable of the Model 2, because i am waiting for a IEC Tupe 19 i orderes from the States, in order to be able to use my power cables from Van den Hull.
Have tried to change the nordost valkyria between amp and preamp for another one i use for the cd palyer, but with no improvments.

With the Model 2 i have lost the wheight in the midband as well as a certain roundness in sound. The model 2 is quite smooth, but the analogy that comes to mind i is like you are feeling a fresh wind instead of a warm wind embracing your body. Everything else is as expected, good image and tonal accuracy. Harmonics are not as good as VK60, bass response surprisingly presents itself  leaner compared to the vk60 wich is quite good (had a Krell KSA 200s before tjhe Bat so i could compare both). All in All a less satisfying sound.

I have opened the Model two and it looks in pristine condition (inside and out), and becasuse the capacitors are hidden, can not see how they are looking.

Is this a mismatch between the model 2 and the Mini Utopias, the current phase inversion, the caps that are due for a replacment, bias adjustment (no idea if it even usess bias adjustmente) or anything else i am skiping?

Your thoughts will be apreciated, as i keep on trying to squeeze the sound i was hoping for.

PS: the next JF dealer is over 800kms away in another country, so i would rather sort it out first before i think of sending them the amplifier for a check in. Also currently still waiting for a reply from the Jeff rowland site, with no replys.




c_n_m
What you are hearing with the Rowland connected to the Mini's is the REAL sound! And if you don't like it, sell them and get something else! But keep the Rowland (great amp!).
he BAT VK60 has an output impedance over 1 ohm (or higher!). So it will act as a tone control when following ANY speaker's impedance curve! OHM's LAW!  The Rowland amp has an output impedance BELOW 1 ohm - so it will have a FLAT (neutral) response with ANY speaker!
roberjerman, thank you for your comments. It is an interesting perspective. I actually never thought of that.



I had a pair of Minis for a couple years and couldn't get them to sound good either. At the time I had Classe, Sumo, Mac, & Plinius amps pass through here, but they sounded bright and thin with all of them. I moved on.
I have finally managed to get things wright. Unsatisfied i kept trying diferent things, and finally got the amp out of the rack to check everything again .

It seems upon installing the Jeff Rowland i unwillingly flliped the toggle down to 600 ohms...

Once it was back to 36k as i thought i had it all the time, things got much closer to what i was expecting. Sound got more dynamic and gained wheight.

It seems that with the higher gain of 32dB the sound is even bolder, but i keep getting back to the 26dB because 32 is excessive, and i can’t turn the volume upwards of 10 o’clock.

I also changed the toe in (less tow in then i had with the vk60) and i am starting to enjoy listening to music again.

Still waiting for the phase inverters from Switchcraft though, and i am inverting the phase on the speakers for a temporary solution.

The Mini Utopias are back in business, eventhough they don’t have that extra wheight that the BAT power seemed to have given them.

Thanks for all your contributions.