TRL Dude or Joule 150 MKII for Major Pre Upgrade

Thinking of either of these for what I view as a huge pre upgrade in my system. Current system is:

-Celestion A3
-Krell KAV250a (500 wpc/4 ohms).
-Nohr CD-1
-Rotel 995 preamp

I am looking to pickup warmth, depth and much more soundstage. Quality bass is also important to me. I want to keep the Celestions and feel that my current pre is the weakest link. Will also will update my digital source and ss amp down the road.

My thinking is that it will be worth paying up a bit for a higher quality pre that I can grow into.

Also I have a small naive question...with either of these pre amps will the sound difference be that great compared to the Rotel.

Thanks...any comments are appreciated.

The TRL will be a significant improvement over the Rotel and will make you happy for many years to come.
Many owners of the Joule preamps will tell you it is one of the finest they have heard, adding just the kind of qualities you say you are looking for. Have never heard the TRL so I cannot comment, but the Joule has been in the mix for finest preamps for a long time, with Jud's best work said to be found in his latest iteration, especially the ME series.
I've never heard the Joule but own a TRL Dude and am still amazed by this piece.

It's truly worldclass IMO.
I have owned Joule preamps in the past including the 100 MKlll. I like the Joule sound and he makes fine preamps for sure. I have not heard the 150 however. I know the Joule would be a nice improvement over your Rotel.

I have owned the Dude for several years now and can say it will deliver the things you are looking for to a greater degree then the Joule. The Dude is a champ at bass and soundstage plus in many other ways.

The Dude will cost $4,000 new and you can find used 150's for under $3,000. Is the Dude worth another $1,000 - $1500?
If you can stretch up to the Dude with your cash, then yes it is. At least is/was for me :-)

Both offer a significant improvement over your Rotel
I have a Joule lA 150II and love it. Watch the listings and you will get a Joule for much less than a Dude, plus you don't see many Dudes come up. Try the Joule for a while, you would probably recoup your money, if you decided to move on.
good luck
The Joule is not only a champ in bass, but the very thing that made HP go gaga over the Joule in TAS. This quality was improved in the 150MKII and later product including the 150SE and the 300 and 450s, but the latter may be beyond your price point. Not sure which of the two brands you will prefer, apparently there will be advocates for both, but I personally would steer to the issue of track record, logevity, build quality, and reliability - the intangibles that go beyond sound. The TRL might be first rate at these, though it has not been around for nearly as long (if that matters to you). Sounds like they would both make you happy.

Frankly, I don't think you will know either way without listening (hard, I know) - that would be far more important than what partisans of either brand might say - but ain't it always the truth.

A brand you don't mention, but you should consider is the CAT SL1 Ultimate - I would be hard pressed to choose between it and the Joule (both of which I have owned) as the are both superb but different and who know how you will respond to what you hear?
You make some very good points,and yes nothing beats a personal audition. I`m familiar with the CAT linestage but I`d take the TRL Dude if given a choice. I find the Dude more'natural' the Cat in my experience is more 'hifi' in presentation. bUT of course YMMV.
Yes TRL has been building great gear for decades an my Dude has been flawless in sound and performance since day one! Both Dudes I have owned.

Paul answers his phone and will always get back right away and help. I must say this is not true of all small "one man" companies. I have still not heard back from Roger at Music Reference and I emailed/called to actually buy his amps - RM10.I decided to buy another amp now. He is one example and unfortunately I know of many others in this business. Paul will respond to customers.
There is a review of the Dude here with a photo showing dual volume controls, the one on TRL's site has one, are there two models?
The Dude I borrowed for a few days last month had dual volume controls and is a recent model.
$4,000 direct? I like the dual controls!

It is true the Roger is not the fastest responder, but his equipment make the
wait worthwhile - I think he has hired an assistant to handle e-mail and phone
inquiries, but it does seem to take 24 hours to hear back.

Grannyring, do you have photos of the Dudes innards you could share?
I really wanted to try a RM10 and asked about buying two in mono block form. It has now been 5 days and no answer. This scares me. Oh well, I bet it is an awesome amp based on many comments by owners.

The Dude photo on the website is old and the old style. The new Dude can be custom made with dual volume or one volume knob. Paul will build it as you like. Mine has one volume knob and 4 - 6sn7 tubes instead of two for slightly more gain. This 4 - 6sn7 design option is not needed for the vast majority of folks, but worked well with my power hungry Soundlab speakers.

The Dude is not small, but a 70 pound beast . The circuit is Paul's and really simple but robust beyond any other pre I have seen.
If you google Music Reference or try to get there from teh Agon link the web page doesn't seem to exist,maybe that's why you aren't hearing back
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Paul answers his phone and will always get back right away and help. I must say this is not true of all small "one man" companies. I have still not heard back from Roger at Music Reference and I emailed/called to actually buy his amps - RM10.I decided to buy another amp now. He is one example and unfortunately I know of many others in this business. Paul will respond to customers.
Interesting!!! Seriously considering RM300 after getting the KT-120 results from Roger.

I have similar experiences with Paul. His gears are reliable and built to last many lifetimes plus EXCELLENT sound.
Ever notice how a 5 minute call with Roger turns into 1 hour? Always interesting.
Ever notice how a 5 minute call with Roger turns into 1 hour? Always interesting.

If you ever get a chance to visit him you'll find a planned 1 hour visit can easily turn into 10.

In addition to basically being a 1 man business Roger consults for a few audio manufacturers and is in the process of restoring his new home. To say he is busy is an understatement. That being said if you have some trouble reaching him an alternative is to contact Sal Zambrano at Audio Summa who is in touch with Roger on a regular basis.
Yup, Sal is the fella I've buying MR stuff from the past year or so - the one who
reruns the calls, advises, and takes your order - good guy.

Saw some pictures of the innards of the Dude thanks to Grannyring, looks like a
very robust unit with a very nice attenuator. Has it been exhibited at RMAF?
Check the "Audio Review" section here on audiogon under preamp and you will find a lot of discussion along with a current picture of the Dude. Great preamp!
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I have a brand new Dude if anyone is looking to purchase this stellar preamp. Email me for details.
Will most likely move in the direction of the Dude. Thanks for all your comments.
I received my Dude preamp last week. It looks amazing.It is the best looking piece in my system. The color is gold. Right out of the box, the Dude sounds bad. Up to now, it has been playing about 30 hours. The Dude is utterly shocking now. The transformation is not subtle. I am hearing details in the music that I have never heard before. The music sounds so real. I just cannot wait for it to be fully broken in. Paul Weitzel's customer service is outstanding. I am looking forward to purchasing new tube amps from him.
I would ask Paul if he would build you one like that. Only he can answer that question.
I sadly passed on a "like new" Dude this week because I couldn't make the high output impedance work with my amps. Although the amps have 100K ohm input impedance, they have balanced inputs only. I have to use transformers to convert rca to XLR since using a basic rca/XLR adaptor causes hum. The transformers have an input impedance of only 23K ohms, which would not work with the Dude. I will need a balanced version if I want to try one, or own one. I would like the opportunity to see and hear one sometime before taking the plunge to purchase one.
Mitch2, as much as I think you should be buying my preamp :) instead of the Dude, I am sure the Dude can work with your amplifier. The problem is that the adapters you were using were not wired right.

The problem is that pin 3 of the XLR was left floating, allowing the amp to buzz of hum. Cardas adapters are often wired this way. Its easy to fix- you just connect pin 3 to pin 1 and you're all set.
Tim (Mitch2), Ralph's comment that pin 3 should be grounded when adapting to an XLR input using a simple RCA-to-XLR adapter is of course correct. I would add that the 23.5K nominal input impedance of your Jensen PI-RX transformers is specified based on a 20K load being connected across its secondary. See the datasheet. With a 100K load I would expect its input impedance to be, as a rough approximation, more like 100K!

A separate question would be how well the transformer will perform when loaded with 100K and driven by the Dude's output impedance (I don't know what that is). I note that the datasheet indicates a maximum allowable load of infinity ohms, but a maximum allowable source impedance of 2K. A conversation with Jensen would seem to be in order on that question.

An ideal transformer (which of course is something that does not exist) having a turns ratio of one-to-one will present an input impedance identical to the load impedance that is connected across its secondary (output) winding.

Best regards,
-- Al
As noted I use the Dude with my balanced amps (100K input) without any issue too. The adapters are wired just that way.
Almarg and Atmasphere, thank you for the comments. I did indeed try Cardas adaptors this week when I heard the buzz. I also own another generic set of adaptors I can try. If I can take a set of these adaptors apart (they seem glued together) I could simply run a jumper between pins 1 and 3, and then try it again with my current single-ended preamp. If I cannot get the adaptors apart, I have the guts of some XLR connectors around here and it would be easy enough to wire up a set and try them.

With a 100K load I would expect its input impedance to be, as a rough approximation, more like 100K!
Almarg, funny you should point out, I previously discussed this very issue with someone at Jensen and I remember being told that very same thing. However, when deciding on whether to purchase this single-ended Dude, I called them again this past week and was told the input impedance would be a maximum of 25K ohms, as shown on the data sheet. Maybe another phone call is in order.

The preamp I am using has an output impedance of only 12 ohms, so it works just fine with the Jensens. I just like to try new stuff sometimes and the balanced only thing limits me somewhat, at least in this case where the Dude has a higher than typical output impedance. If I can get the adaptors to work without noise, that might be the ticket.
Ok, I checked out my generic rca/xlr adaptors both using a multi-meter and also by taking one apart. These have a jumper from pin 1 to pin 3. Hooked up my single-ended preamp using these adaptors and have the same moderately loud buzz. Run through the Jensen transformers the same preamp/amp combo is dead quiet. Also using my MUSE balanced preamp, or the balanced active outputs from my MUSE Erato II player, the amp is dead quiet without the transformers. Therefore, choices are to keep using the transformers and preamps that work well with those (e.g., preamps having output impedance preferrably below about 1K ohms, and no greater than 2K ohms); find a balanced preamp I like better than my preamp/transformer combo; or buy new amps with single-ended inputs.
Tim, sounds like the single-ended preamp has a ground loop problem when working into the balanced amp via an adapter, the loop being broken, as might be expected, when the transformer is used.

An adapter-based approach that I suspect would provide better results, although probably not as good as the transformer-based approach, would be to connect RCA male to XLR male adapters at the preamp outputs, and run XLR cables from there to the amp. That would essentially be equivalent to the arrangement shown in Figure 2.1 of this Jensen paper on interfacing balanced and unbalanced equipment.

With respect to using the transformer, I wouldn't necessarily conclude that you have to stay below 2K output impedance for the preamp, given that your amp has an input impedance of 100K. It seems conceivable to me that the 2K figure in the datasheet is based on the assumption of a 20K load, just as the input impedance spec is based on that assumption.
However, when deciding on whether to purchase this single-ended Dude, I called them again this past week and was told the input impedance would be a maximum of 25K ohms, as shown on the data sheet.
My guess is that the person you were speaking with was not Mr. Whitlock :-)
Maybe another phone call is in order.
Yes, that would seem clear.

On the other hand, you could buy one of Ralph's preamps, and the issues would all be moot :-)

(I have no affiliation).

Best regards,
-- Al
The Dude as an output impedance of around 5k ohms. I am having the same noise problem in my system with an Aesthetix Atlas hybrid amp and my Dude preamp. The Atlas has both xlr and RCA inputs however. I get a buzz with both the Dude and a passive preamp -
Lightspeed Attenuator. Seems both of our amps may be very picky regarding single ended preamps and ic's? Al has tried to help me figure out my issue, but I still have a buzz - slight buzz on both speakers. Sounds like some sort of ground loop issue to me.

Strange for sure..For me the buzz only came when I changed speakers from active to passive. No buzz with active speakers, buzz with passive.

System sounds great so I live with it. Can't hear it 10 feet back.

I tried adaptors like you with pins 1 and 3 tied, still a buzz. I purchased an ic that goes from RCA to xlr with 1 and 3 combined, still have a buzz.

I am getting some kind of ground loop issue when my ic's are connected. Any ic's. I may try your transformer answer, but now wonder if their will be an input impedance mismatch with my pre and the Jensen transformer? The Dude has 5k ohms of output impedance.
Grannyring, I have an extra transformer since I went from a two-channel transformer box (both L and R channels in one box) to mono transformers (two boxes) when I moved my monoblocks further apart (although they are now closer together again). The balanced cables out of the transformers should be no more than 1M long. The ones I use are about 2 feet long. To use the one-box version, your monoblocs must be reasonably close together.

I had offered to let another member try the transformers. Since he is not having the buzz issue and I do not think he needs/wants to try the transformers right now, maybe you would like to try them and see if they help. This would be interesting information for me too, because then I would learn whether a single-ended Dude might work for me.

My plan earlier this week was to try the single-ended (SE) Dude that was up for sale on this site and if I liked it to go ahead and order a balanced Dude while continuing to use the SE Dude. I planned to use the SE version for the 3 months it takes TRL to make these and then sell it after I received my new balanced Dude. I declined to buy the SE Dude after my research indicated the 5K ohms output impedance may not work with the transformers. However, Almarg is correct, I do not believe I spoke with Bill Whitlock when I called Jensen last week.

Almarg, I know Ralph's preamps are fully balanced and would work properly with my set-up. While I respect Ralph and his company immensely, I just didn't care for the sound of the Atma-Sphere preamp that I owned some years ago. It was a tricked out MP-3 with teflon, regulated power, and Caddocks. I am aware of an Atma-Sphere preamp for sale now that is called an MLS-1 Linestage, which is apparently a one-box precurser to the MP-1. I know it is old because it has the yellow board they used early on. This pre was apparently at Atma-Sphere recently where it received; new filter caps, HV regulated power supplies, fast rectifiers, the latest 3.1 version volume attenuator, main power transformer, and state of the art copper CuTF V-Cap coupling caps, as well as a full cleaning of all controls and input/output connections. The price is reasonable but I have no idea where something like that would fall between the MP-3 and MP-1. It would have to offer something above the MP-3 I owned for me to consider trying it.
Grannyring, your issue doesn't seem to me to be a ground loop issue, as it occurs even when the preamp is unplugged from the AC outlet (and with no source components connected). Therefore I'm not at all certain that a Jensen transformer would solve the problem, which I'm frankly out of ideas on.

For anyone else who may be able to contribute ideas on Grannyring's issue, it was discussed here. Note that multiple sets of interconnect cables were tried, as well as both the Dude and Lightspeed preamps. Yet the problem goes away when the inputs to the amp are disconnected, and the problem did not occur until the previous speakers, which were electrostatics, were replaced with passive speakers.

Best regards,
-- Al
My Dude works fine with my low gain power amp. But when it was used with a pair of high gain tube monoblocks, I could hear some humming noises. So I got rid of the ground loop by floating the signal ground from the AC ground at the power amp, but keeping the chassis connected to the AC ground for safety. It has been quiet since then.
Vett93 , please help me understand what you did? I am not understanding your fix? Are you saying you simply used a cheater plug on the amp? If so, tried that also.Thanks

Mitch2, thanks much for the offer. I want to try what Vett93 is saying and I may take you up on your offer.

Al, you may be right or I may have a ground issue that is induced between gear thru the ic's .....don't know. I have another system I may place the amp into today to see what happens.
Back to the OP, the Joule will likely be easier to find here used (if that is your intent) than the Dude, simply because more have been made over a longer period of time. There is an LA 150 MkII for sale here now. I owned that preamp and it would be a huge upgrade over the Rotel. You would also have the option to upgrade it to the Signature Edition [LA-150 MkII SE] version in the future for $1,750. In addition to a very nice appearance, the Joule offers a couple of neat features that can have practical applications such as selectable output impedance of 400 and 1200 ohms, and selectable gain from 0 to 11 dB. The 6350 tubes used are no longer made but Joule has thousands for when you need more, and they are also available in other is something I found about those tubes:
6350: This tube was mainly manufactured for IBM and other computers in the late 1950s to mid 1960s. Sylvania and GE blackplates are considered the best of all with this tube. It has a mu or gain factor of 18 so is very close to the 12AU7. These were made to tight specs and carefully quality checked, since replacement in a computer of the day was difficult and costly, and the tubes were expected to operate 24-7. These make impressive upgrades to the standard 12AU7!
I don't use cheater plugs. My method fixed the hums from a ground loop. Let me first establish a baseline. Some systems have two ground connections: one through the signal ground wire connection (interconnect) and the other through the ground pin in the AC plug. Most designers wire these two together and to the chassis. You can have a ground loop when you connect two components using an interconnect cable.

I don't use cheater plugs for two reasons: 1. I think they are usually not very good quality, and 2. I want the chassis wired to the AC ground for safety reasons. (I am paranoid...)

So you would need to decide where you want the ground point of your system to be. You want only one ground point in the entire sysetm. By ground point, I refer to the point that signal ground is connected to the AC ground. Most people think the ground point should be either the source or the preamp. I chose the preamp as the ground point because one of my sources does not use the ground pin of the AC plug.

If you choose the preamp as the ground point of the system, you may have two ground loops: one at the source and one at the amp. Typically, the hum is caused by the ground loop at the amp. So the next step is to get rid of the ground loop at the amp. Some amps have "float" switches for this purpose.

Before we go on, we need to make sure that the preamp is indeed the system ground point first. My understanding is that some TRL Dude preamps don't wire the signal ground to the AC ground. If you have this configuration, then your ground loop is from the source to the amp, which will produce even louder hums.

If you are still with me, now we can proceed to get rid of the ground loop at the amp. There are three points of interest at the amp: signal ground, AC ground, and the chassis. I would wire the AC ground to the chassis and then keep the signal ground float; i.e., not connect to chassis or AC ground.

I think my method is good and safe. I have heard some more "advanced" methods for grounding. But I think they are safety hazzards.

A remaining question is if I should get rid of the ground loops for systems that do not hum. I have a few gears to rotate and some combinations don't hum at all even they have ground loops. One school of thought is that if it ain't broke, don't fix it. The other school of thought is that even it does not hum when the sysetm is idle, it could produce ground noises when the system is not idle.

Vett93 thanks for your response. Well, when my cd player is totally removed from the system by unplugging both power cord and ic's I still get a hum/buzz though the speakers. The buzz is not present with the amp and speakers only. As soon as any preamp I have here goes into the amp by ic's ( not power cord into the wall) then the buzzing begins.

My Dude is grounded at the AC inlet plug. The power supply also looks grounded, but I am not certain about the signal ground being wired to the AC ground as you say? I will ask Paul.

In case it is not clear to you, I modded the amp to get rid of the ground loop. I opened the chassis and found the designer wired the signal ground, the AC ground, and the chassis all together. So I diconnected the signal ground from the AC ground/chassis.

Hope it is clearer....

PS. If you have a high voltage amp, be careful of what you are doing....
Hi Grannyring,

If the power cord is not plugged in to your Dude and you have a hum already with just the interconnect, it is not a ground-loop induced hum then. Have you tried a shileded interconnect like the one from Blue Jeans cable?

What amp do you use these days?
Gentlemen, once again let me emphasize that Grannyring's issue arises even when the preamp's power cord is not plugged into an AC outlet, and when no components are connected other than the preamp, power amp, and speakers. Therefore I don't see how the problem could be due to a ground loop, because there is no loop in that situation.

The facts that the problem is not present when nothing is connected to the inputs of the amp, but is present when the preamp and interconnects are connected to the amp, would seem to suggest an issue involving emi/rfi pickup. However, as Grannyring indicated in his thread that I linked to earlier, in addition to its normal RCA and XLR inputs his amp provides separate RCA and XLR inputs that are processed through high pass filter circuitry. And when the preamp is connected to the normal RCA inputs the problem exists even if any of the other three inputs are selected on the amp. Which leaves me totally baffled, unless perhaps something is defective in the amp's input select circuitry. But that, in turn, would not seem to explain why the problem wasn't present with the previous speakers.

Vett93, regarding your otherwise excellent posts it should be pointed out that with many designs isolating signal ground from chassis and AC safety ground may involve considerably more than minor modification. For starters, the ground sleeves of RCA connectors may not be isolated from chassis. Also, it would seem possible that in many cases changing the component's internal grounding scheme might result in unpredictable sonic side-effects.

-- Al
Grannyring, Have you tried connecting the cd player to the amp with and without pc in the cd player? If same buzz noise, then narrowed the problem to the amp.

Have you check the tubes in the amp? Once I had a bad input/driver tube in my tube monos and it produced a buzz humming noise.

You can always ask Paul to convert or add pseudo XLR outputs to your Dude.
Al, I am very sorry that I did not see the previous posts.

Bill, you mentioned that you shorted the pin 1 and pin 3 of the XLR connectors and it would still hum. Did you just short 2 of the 4 XLR connectors? If that is the case, can you try to short all 4 XLR connectors? I mean shorting the pin 1 and pin 3 for all 4 XLR connectors.

The design of your Atlas amp looks similar to my Counterpoint/AltaVista NP100 amp by Mike Elliot. They both use 6SN7 differential gain stage and don't use switches in that area.

Let me know if that fixes your problem.
I will try shorting all 4 xlr inputs. I will try a Blue Jean cable also. Last, I will try direct hook to my cd player. Thanks to all!
We had a Dude in here for repair a while back and found that the ground setup was peculiar. In a nutshell is would not pass UL/CE certification. I understand later units are grounded differently.

I think there are several things going on with the various responses we have seen on this thread. I am certain that in all cases a transformer is not needed, and I suspect that the reason that it eliminated hum has to do with ground isolation that transformers can provide. But we must keep in mind that there are variances in the production of the Dude, so what may be causing hum in one system may not be what is causing it in another.

So let's start with the AC ground. It is possible to have the Dude chassis tied to the ground connection of the AC power cord, but in some cases this will result in a buzz if the amps are also grounded. This will vary with amplifier, for example some amps (like Classe) are grounded correctly while others (older Cary) often have the chassis and circuit ground tied to the AC ground (which is incorrect).

As you can see, its not just the Dude that has variance, so this can be a tricky matter! It is possible to test the amps and preamp without plugging them in to see if they are grounded correctly. If you measure from the AC ground pin of the power cord, it should have a direct connection to the chassis. However the audio input should not- you should be able to measure a resistance (under 200 ohms but more than zero!) between the audio input and the chassis. This is also true of the preamp, however since the preamp is the heart of the system, it can be alright if its audio circuit is the same as chassis ground, so long as the amplifiers are either grounded into the AC as above **or** not grounded at all (in the case of improperly grounded amps like the older Carys mentioned).

Now let's examine cables. If you are running from the Dude, which is single-ended, it is a good idea to check the resistance from the shield connection of the RCA to the same at the other end of the cable. It should measure nearly zero ohms. If you are using an adapter to convert to XLR, there should be zero ohms between the RCA shield connection and pin 1 **and** pin 3 of the XLR. The center pin of the RCA is thus pin 2 of the XLR.

Now I have also seen amplifiers that purport to have balanced inputs that have some really strange stuff going on- a year and a half ago we discovered a well-known solid state amp that used an input transformer (which allowed it to theoretically operated balanced or single ended with ease) was set up so that the input transformer ignored pin 3! On another occasion we found an Audio Note DAC that used pin 2 for ground instead of pin 1 of the XLR!

So if you want to be scientific about it the connections at the input of the amp should be tested to see that they are correctly wired. Many high end audio manufacturers are not aware that there are standards for the balanced operation...

If the above issues are satisfied, there will be no hum/buzz. This is of course assuming that the preamp is working correctly in the first place (hum and buzz was a problem with the sample we saw). So its a good idea to test the preamp with a known-good alternative amplifier, or to replace it temporarily with a known-good preamp (quite often one of your sources like a CD player can be sufficient for this).

Good Luck- keep posting.