[classfolkphile]

I have the 25.2 and thought it was good from the beginning. And this is coming from some fairly expensive digital rigs in my system.

Two caveats.
First, as has been mentioned, the stock tube must be ditched. I've tried a Philips gold pin 6922 and an Amperex gold pin 7308. Both are really excellent and make a significant difference in clarity, resolution, frequency extension and bass tightness. Second the soft stock feet must be bypassed. I've used both Symposium precision couplers (relatively expensive) and myrtle blocks (cheap). Both reduced the muddiness that is the unit's main drawback.

Having had several modded CDPs previously, I decided to go that route with the 25.2 given the fairly inexpensive options available from Affordable Audio; which, being they're both a dealer and the Music Hall service center, do not void the warranty.

Mods for the Music Hall DAC 25.2 [DAC 25.2 Mod] - $250.00 : Affordable Audio Venice California in West Los Angeles, | AA TECH DESIGN |

(No connection except as a customer).

I went for the full upgrade package: new diodes, op-amps, resistors, and Hovland Musicaps. Cost was $450 (there are cheaper options). The improvement is beyond what I was expecting. All muddiness is gone. Clarity and resolution are further improved and the increased transparency and image separation is stunning.

I also recently picked up a stock Havana DAC, which I love. I'm using it with an Ericsson gold pin 2C51. The modded 25.2 is at least on the same level as the MHDT and might be better (though, of course, very different). I'm hearing a slight dryness, even graininess, to the vocals on the latter that has me considering changing the caps in it.

For those interested, I'm using a Marantz SA15S2 as a transport with either a Jena Labs Symphony or KCI Pegasus Digital IC. Amp is a Rogue Cronus (with very upgraded tubes), while speakers are Aural Acoustics Model Bs. Wiring is Jena Labs, PCs are Kaplan and Black Sand Violet Z2s.

Sorry for the length of this post.

 

[TJHUB]

I owned a PS Audio DLIII DAC for few months and thought is was the best DAC I've heard for the money. Over time, the only real complaint I had was that many times the DAC would throw a nasty, make you want to squint, treble brightness that I could not live with. Even though the DAC was said to be "warm", I never thought it was.

This sent me on the hunt for a different DAC and I tried a few. All this proved was that the PS Audio DLIII was still the "best" DAC I've heard in my setup. I then ran across a deal on a Music Hall DAC 25.2 and figured I'd give a tube DAC a try.

(NOTE: All of my comments are based only on the tube output of the Music Hall DAC.)

From reading everything I could, I knew the stock tube wasn't very good, but I was too slow to pick up any other tubes and I ended up listening to the DAC with the stock tube for a week. Even with the stock tube, I could find many things to like about the DAC. The biggest things that really jumped out at me was the very wide sound stage with decent depth. The sort of 3D sounding imaging and separation was very good. But as this first week moved on, I could really hear just how poorly the stock tube performed with the main issues lying in muddy bass, limited extension, and a sort of distorted sound overall. BUT...this was the first DAC I listened to that I didn't hate.

I was completely new to tubes, so it was not easy for me to start tube rolling. Thankfully there are a lot of really great people on some of the other forums I frequent and I had a couple of tubes sent to me to try. To make a long story short, here are the tubes I've rolled in the Music Hall:

Electro-Harmonix 6922 (stock tube) (NOT A GOOD TUBE!)
Telefunken E88CC (1960's)
Tesla E88CC (1980's)
Amperex (Holland) (RCA label - late model)
Conrad Johnson labeled 6DJ8 (unknown brand)
JJ E88CC

And the hands down winner of all of them for me is a 1972 NOS Mazda 7308. It was the only tube that had great extension, great attack and decay in the treble, an open and very clear midrange, with decent bass articulation. The latter was the biggest issue for me with most tubes. Basically the Mazda tube was by far the most balanced sounding tube of all of them.

Since rolling some "good" tubes through the Music Hall, I've really grown to like it a lot. It was now far better than the PS Audio so I finally sold it. I find the Music Hall to have almost perfect synergy with the rest of my setup and I've decided that I'll always have a tube component in my systems from now on. I can't believe I got all the way to 41 years old having never tried tubes. A tube DAC or preamp will always be in the mix for me now.

However as time passes, I always have to find issues and "improve" things. It's in my nature and I can't help it. I was reading about all of the upgrades some companies do for this DAC and I found a thread where someone had modded their DAC step-by-step. To shorten the story, I decided to try new Burson opamps. I didn't really know exactly what to expect, but the change was significant.

Here's a pic of the Bursons installed:

As soon as I installed the Burson's, the biggest change was clarity. It was like everything was so much more coherent. I could literally hear more music. Every little detail and nuance was more obvious. I thought things were really good before the Burson upgrade, but wow, things were much better. Even at low volumes, everything is so clear. The strike of a piano key and the tap of cymbals is just perfect sounding. Transients are sharp without any hint of harshness. The detail is amazing and the tonality seems perfect. The separation and definition in the sound stage is much improved. This DAC is absolutely amazing for the price!

While I should leave well enough alone, it has been recommended to me to upgrade the clock and some diodes in the DAC. I'm on the edge of ordering them, but I first need to make certain I know how to install them properly. I'm looking forward to any possible improvements I may get from these future changes, but if I decide not to do them, I know I'm already happy with the way things are.

The other huge improvement with this DAC came when I tried a tube damper. I don't want to get into it, but the tube damper was terrible. I couldn't live with the sound, so I pulled it off. The sound was back to "normal" and this confused me. So knowing that the DAC was being affected by vibration, I tried an experiment and put the DAC on a small fiber filled pillow. WOW, big difference in clarity and articulation. Now I'm trying to figure out what feet to put the DAC on as the pillow is not all too sexy.

My setup:

Roku M2000 streaming WAV
Music Hall 25.2 DAC
Parasound 2100 preamp
Parasound 2250 amp
Salk HT2-TL speakers
SVS PB13-Ultra subwoofer

 

[Skylab]

Nice. Maybe it's time for me to upgrade from the Sylvania I put in mine to an Amperex or one of my more "exotic" NOS 6922's...

 

[jpelg]

Quote:

Originally Posted by TJHUB /img/forum/go_quote.gif NOTE: All of my comments are based only on the tube output of the Music Hall DAC.

Quote:

I decided to try new Burson opamps...the change was significant.

Where in the chain are the op-amps that the Burson's replace? I thought the tubes were on the SE-output side, while op-amps were on the balanced side. Are there other op-amps on the circuit board that affect both outputs?

 

[classfolkphile]

Forgot to mention that I also changed the fuse by the IEC connector to a Hi-Fi Tuning Fuse and, as always, it made a nice improvement: a bit more resolution. Well worth the $.

 

[TJHUB]

Quote:

Originally Posted by jpelg /img/forum/go_quote.gif Where in the chain are the op-amps that the Burson's replace? I thought the tubes were on the SE-output side, while op-amps were on the balanced side. Are there other op-amps on the circuit board that affect both outputs?

Unfortunately, I do not know the answers to these questions. I am following the instructions of a forum member on another forum and the people at Parts Connexion. Both have been very helpful, but the forum member has basically done almost all the mods step-by-step and has given impressions as to which ones proved the most bang for the buck and easiest to perform DIY.

 

[RayfromTX]

I've read through this thread and others and I'm still not clear if rolling the tube would improve the performance of the signal coming out of the headphone jack. Can anyone tell me for sure?

 

[classfolkphile]

No it would not, unfortunately.

Underwood Hi-Fi on A'gon. is offering a headphone mod to the 25.2 for $250. but I don't know what it entails.

It would seem to me that just changing an op-amp or two would make a large difference. I'm going to shoot an email to the company that did the non-headphone mods (listed above) on my unit and see what advice they may have to offer.

 

[stoutblock]

I've had this DAC for many months now. I use mine only in SE (First Sound line stage does not have balanced inputs). I rolled several tubes but found the Mullard cv2493 to perform the best. It seemed to open things up more than other tubes. It is also my favorite line stage tube.

Considering updgrades. I would have started with the opamps but I assumed these are for balanced only? Anyone know for sure?

 

[TJHUB]

Quote:

Originally Posted by stoutblock /img/forum/go_quote.gif I've had this DAC for many months now. I use mine only in SE (First Sound line stage does not have balanced inputs). I rolled several tubes but found the Mullard cv2493 to perform the best. It seemed to open things up more than other tubes. It is also my favorite line stage tube. Considering updgrades. I would have started with the opamps but I assumed these are for balanced only? Anyone know for sure?

You can see on any list of components provided by companies that mod these DACs that they all upgrade the opamps for the tube buffer outs. All three opamps must be replaced for the SE outs. You can contact Parts Connexion as well. I've purchased all of my upgraded components from them.

 

[ztsen]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Nice. Maybe it's time for me to upgrade from the Sylvania I put in mine to an Amperex or one of my more "exotic" NOS 6922's...

the problem of finding an Amperex 6922 NOS is like treasure hunting. It is Expensive and many fake amperex in the market. Did you successfully get one?

 

[Skylab]

I do not have an Amperex 6922. I do have some Amperex 6DJ8's (which for sure are real - I know how to tell on these).

I keep looking, but I am not really sure I want to spend the $$$...

 

[adam2434]

I just picked up this DAC.

TJHUB, I'm seriously considering a French Mazda 7308. Do you mind my asking where you got yours and how much you paid?

Also, I was wondering if anyone has rolled any opamps (besides Bursons) in the RCA circuit output (the two OPA2134PA and OPA2604AP).

I was thinking the following as options:

AD8066
AD8620
LM4562

Thanks,

Adam

 

[dreamweapon]

im about to order one myself. in a couple months i want to swap out the tube for another since it's highly recommended. any suggestions? i'm new to this and i dont know a whole lot about tube rolling. do you think a siemens tube or a mullard tube would be best with this? thanks

 

[Skylab]

A Mullard CV2492 would sound very nice. I put a Sylvania JHS-6922 in mine. Also sounded very good. Siemens tend to be a little lean sounding - not my cup of tea.