Modwright LS 36.5 or BAT VK-51SE

Roor, why the pre-amp search if you are upgrading your Pass pre-amp? It is my understanding that Nelson Pass creations are best if used together particularly in light of the impedance matching issues.

In terms of pre-amp options, I cannot speak to the BAT or Modwright as I have not heard them in my system. I would consider calling Dan Wright and seeing if any of his pre-amp owners also own Pass amps for more feedback. Otherwise, use your gut and buy something used for a trial.

I am a TRL Dude owner and love that unit, but also use their monoblocks and not Pass Labs. I don't know of any TRL who also owns the Pass Labs amps. The Weitzels might know.

Regarding "pull down resistors," that is simply studio slang for a xlr-rca adapter using a resistors to come up with a "phantom" negative phase. Cardas sells them. Nothing mysterious there.

"The posts by Atmasphere starting here provide some insight into the output impedance of the Dude"

Almarg, there is no insight there. Just misinformation.

I should add to my previous post that high output impedance that is primarily resistive, and is therefore high at high frequencies as well as low frequencies, can result in upper treble rolloff due to its interaction with cable capacitance. But that is easily avoided by using low capacitance cables and/or avoiding long cable lengths, and is unrelated to which power amp is used.

Best regards,
-- Al

Since the output impedance spec of the Dude is not provided, it seems to be a situation where you'd have to hear the preamp in your system to decide if it matches or not. You'd want to be listening for rolled-off highs. I don't know what a resistor pull-down XLR is.

The BAT VK-51SE was tested by Stereophile, and the output impedance was measured at 410 ohms (200 ohms spec'd by BAT), and rising to 4700 ohms at 20K.

Grant, I think you meant to say 20Hz, not 20K, and that what should be listened for is rolled off lows, not highs.

I don't know what a resistor pull-down xlr is either.

The posts by Atmasphere starting here provide some insight into the output impedance of the Dude. It sounds like a major contributor to its output impedance is the volume control and its setting (he indicates that the control is located at the output), with the output coupling capacitor perhaps being no more than a secondary factor.

Since the volume control is essentially resistive, rather than capacitive, its contribution to output impedance would be pretty much constant with frequency. So high output impedance would be much less of a concern than in the more common situation where it is due primarily to the output coupling capacitor, which would cause the output impedance to be much higher at very low frequencies than at higher frequencies. It is the DIFFERENCE in output impedance between those frequencies that causes low frequency rolloff when output impedance is too high relative to power amp input impedance.

Best regards,
-- Al

Greg, I have no information specific to Lamm being noisy with other amps. However, you are correct to be concerned, and you should pay attention to this issue with a demo. Particularly with the Pass which are so quiet, adding a noisy preamp is one step forward, two steps back. If you can readily hear the difference in noise from your listening position in a quiet room with the preamp on vs. muted, then it may nag you in the end. I think noise destroys a soundstage.

In terms of mismatch, also consider that cabling is HUGE in defining bass and upper-end extension (PC, IC, SC). So many cables out there restrict both, or do one at the expense of the other.

Tvad: Was there any hiss or noise with the L2 Reference with the Pass Labs XA-60.5's?

I've read several posts where the Lamm L2 reference hisses loudly with just about every other amp besides their own, and Lamm says it's "normal". It's driven people crazy that tried to fix the problem with no luck, so it sounds like a risky move. I'm leaning towards the Modwright LS 36.5 at this point or possibly that with seperate dual mono power supply.

Erndog: Yes, I want to upgrade speakers as well, and am negotiating on a pair of preowned Daedalus Ulysses.

Tvad: Pauls's response regarding the balanced option and impedance was

"No, I've never heard a line transformer that I liked, even spent lots of money trying to get some made. We use a resistor pull-down xlr. I think we've sold a Dude to a Pass owner, what's the input impedance? Dude is happy with 25K or more load. Lower, there might be some bandwidth loss, might be more of a situation on paper than in actual use, though. Thanks,Paul"

The input impedance on my XA-60.5's is 30k balanced and 15k unbalanced?

I'm not certain these will be compatible? Any thoughts, as I don't know much about impedance and proper matching?

Will I be ok if I used the balanced input on my amps connected with a resistor pull down xlr on the dude?

Thanks,

Greg

Roor- When you gonna upgrade those speakers? I'd do that before anything else.

As far as the preamp goes. I've got a Modwright SWL 9.0 and absolutely love it with my Pass Labs amp. Mine is the model below the 36.5 you are considering. I enjoy the flexibility to roll tubes and the weight and body it adds is superb.

Please consider that the XO.2 has a decent resale value, so moving to either the BAT, MW or Dude won't cost me much out of pocket once the XO.2 is sold.

FYI, Last time I talked to Paul, he has developed a fully balanced Dude so contact him if interested.

I think these preamps would have a world of difference between them. All good, all different. In the right system, the best out of the 3 could mean the difference between magic or dull.

Well...

If one cannot tell the difference between 3 entirely different preamps, I'm not sure if I would consider that a curse, or lucky.

At least it makes life simpler.

Tvad:

I appreciate the input. Do you think a balanced TRL Dude would be a better choice?

Roor,
TRL Dude is a single ended design and Paul can add all the pseudo XLR inputs/outputs that you need.

Bugredmachine:

I've never heard either of these tubes, or either of the preamps! I live in northern NH and there isn't much access to demos or dealers around here, so I am going on input I've received and reviews. I would love to hear about the differences between the two models of tubes these two different preamps use. Thanks,

My system is:

Pass XA-60.5 amps
Esoteric P-05 transport
Esoteric D-03 DAC
Totem Hawk speakers
Pass Labs X0.2 preamp (upgrading now)

I thought about the TRL Dude as well, but isn't that a single ended (rca only) preamp?

I need balanced inputs and outputs. If the Dude is available with balanced ins and outs, it will certainly be in the running.

Can anyone confirm?

service is excellent from both organizations. Both solidly built as well. You really can't go wrong with either but it might help to know what tubes tickle your fancy and lean that way.

What he said.

I had the single box 36.5 side by side with a Dodd battery and a response Audio Bella Max pre and the order of finish was the Bella, the Dodd, and then the MW in terms of overall clarity and air.

Yes a nice unit and Dan is very cool. I recently had an entry level BAT unit and really liked it and had great response to my questions by Viktor. I was on the verge of going with a 51SE or even the 52SE and then decide to slow down and shop around some. When I tried the Rogue Anthem with the same 6H30 tubes as used by the others mentioned it was fantastic, but I have ordered a TRL Dude based solely on reviews here.

So I would not count out BAT products and believe service is excellent from both organizations. Both solidly built as well. You really can't go wrong with either but it might help to know what tubes tickle your fancy and lean that way.

I auditioned both preamps thoroughly in my system (Thiel 3.7, Primare A32 and Marantz 7s1, Supra cables. I also auditioned ARC Reference 3, CJ ACT 1, Aesthetix calypso and Pass XP10. Surprisingly to me, I thought the Modwright 36.5 exceeded them all. The integration of the sound and the articulate low frequencies (unlike the VK51SE which had a strong bass but not the clarity) made the decision easy. I thought based on reviews that the Ref 3 was going to be my choice, but it sounded good but not great in my system; in fact, I would have been hard pressed to hear a lot of difference between the Calypso and the Ref 3. Proves once again there is NO substitution for auditioning in your system in your room. Given that there are 36.5s on the used market for under $3000 I think it is a tremendous value. Build quality is superb and I particularly like having a volume knob again.

I love my ModWright preamp! I have owned several different BAT preamps, (though not at the same time as the Modwright) and find the sound of the ModWright more to my taste.

I also agree that Dan is the MAN!!! He's a pleasure to talk to and work with.

I'll second Horseface's post--no experience with BAT but Dan has been a joy to deal with, his gear is well made, looks great and sounds fantastic.

I can tell you this:

Dan Wright has always been there for me anytime I had a question or needed help. He stands behind his products and is great to deal with. I think service is always something to consider anytime you make a big purchase. Not trying to take anything away from BAT ... just sharing my good luck with Modwright.

Good luck,

both are first rate items from first rate folks.

I'd guess the issue here revolves around what sort of sound you are shooting for and which features best suit your needs.... if both are on par with one another pricewise.

If you have it narrowed to 2, get both, return or resell the one you don't like.

Some sellers maybe even willing to let you try for a week with the option to return. Of course, you cannot lowball someone and then ask them to do this for you, but it is reasonable to ask, if you are buying at their asking price.