Introductory Hello & My M125 Build

Denizen wrote:I realize the tubes are brand new and I'm only running one speaker but I was surprised that I didn't hear any difference between pentode and triode modes. What might be the reasons for that?

I never could, either, except for the drop in power.
The pentode or ultralinear mode was the final development of these types of circuits; running in triode seems like a step backards.
Some guys swear there's an audible difference - might be speaker-dependent.

If you are not running near clipping, and you have sufficient headroom in both modes, you should not hear any difference. Do you have any signal with a wide Peak-to-Average? As much as 20+ dB? If so, and you run at a moderately high volume, you might hear a difference.

In any case, enjoy!

deepee99 wrote:

Denizen wrote:I realize the tubes are brand new and I'm only running one speaker but I was surprised that I didn't hear any difference between pentode and triode modes. What might be the reasons for that?

I never could, either, except for the drop in power.
The pentode or ultralinear mode was the final development of these types of circuits; running in triode seems like a step backards.
Some guys swear there's an audible difference - might be speaker-dependent.

Interesting. I tried it out with my Alpair 10p FHXL (8 ohm socket) then a Magnepan 1.6qr (4ohm socket). Neither one made a discernible difference to me.


Ah, just seeing your response as I was writing this.
That would definitely explain it. Thank you.
Is there any advantage then other than volume?

deepee99 wrote:
Some guys swear there's an audible difference - might be speaker-dependent.

I swear, although I prefer pentode.

Just FYI,
You can toggle between triode and pentode "on the fly" but there's a lot of juice running through that switch so to be ultra-cautious I would shut her down first, let the pwr supply cool, then make the change.
Several after-market guys who start with the basic VTA amps don't even include the option and their gear just runs in pentode all the time. I don't miss triode mode. If I could hear any difference, it would be that the bass in triode sounds a bit wimpier. But that could be just expectations. You'll get the most our of your outputs in pentode and you're not saving any tube-hours by running in triode.

I find triode mode pulls the mids forward at the expense of the upper and lower edges which become softer. Since I like vibrant mids I address the fringes through biamping my speakers. SS amp for the highs, preserving the high end sparkle. Meanwhile a powered sub fills out the lows below 80 hz. The difference is subtle, but IMHO noticeable. Another dollar for the swear jar.

I got the 2nd one finished late last night but couldn't really crank it until now. Tubes are still too new to evaluate the sound but these m125 have power to spare. Even with my Magnepan 1.6qr the volume dial goes much further than I dare go. Effortless power.

https://ibb.co/nxJWBv

Looks nice but watch out for excessive heat buildup. Heat coming off those tubes is fierce and its going to refract back onto the amp with the shelf above being so close. Small cooling fans are advised if that's where you intend to leave them.

LeGrace wrote:Looks nice but watch out for excessive heat buildup. Heat coming off those tubes is fierce and its going to refract back onto the amp with the shelf above being so close. Small cooling fans are a must if that's where you intend to leave them.

I hoped they'd be ok there but I felt exactly what you mean and I'm letting them cool down now before I move them onto the floor.

Denizen wrote:

LeGrace wrote:Looks nice but watch out for excessive heat buildup. Heat coming off those tubes is fierce and its going to refract back onto the amp with the shelf above being so close. Small cooling fans are a must if that's where you intend to leave them.

I hoped they'd be ok there but I felt exactly what you mean and I'm letting them cool down now before I move them onto the floor.

I recall Bob L. saying that the only thing those output tubes should see is the ceiling. That heat's also tough on rectifiers, esp. Webers.

deepee99 wrote:

Denizen wrote:

LeGrace wrote:Looks nice but watch out for excessive heat buildup. Heat coming off those tubes is fierce and its going to refract back onto the amp with the shelf above being so close. Small cooling fans are a must if that's where you intend to leave them.

I hoped they'd be ok there but I felt exactly what you mean and I'm letting them cool down now before I move them onto the floor.

I recall Bob L. saying that the only thing those output tubes should see is the ceiling. That heat's also tough on rectifiers, esp. Webers.

I missed that but discovered it quickly enough.
Drilled ventilation holes in the Webers before ever even using them. Was easy to see why it's a popular mod.

Current set up is nothing much to look at but is only temporary. At least they'll stay cool.
https://ibb.co/hZreEF

The shelf location is fine as long as you implement supplemental cooling. I have a similar setup, and at first I could see it was a problem, the PT's would get smoking hot. I then moved the amps to the uppermost shelf, but everyone kept wanting to touch the tubes!! (why is that?) Plus the cabling runs were awkward.

So back onto the lower shelf they went. Except this time I mounted some low RPM low flow Noctua fans directly behind the amps. Noctua is an Austrian outfit known for their very low noise fans. PT's only get lukewarm now and amps are safely tucked out of the way!

Merci LeGrace.

I'll look into that further.

LeGrace, I see Noctua has quite a variety. Which size did you go with and if you were to do it again, would you use the same size?

LeGrace --- what is the part/model number for the Noctua Fans that you used?

Please let us know.

Thanks!

The model I used is Noctua NF-P12. I have a small power supply I took from an old computer that I situated on the floor in behind the amps to power the fans, since this model is DC. I would use 120 mm dia again, keeps the amps so cool and they are very quiet.

Denizen wrote:Merci LeGrace.

I'll look into that further.

Denizen, since you seem to be quite the carpenter, you might want to just build an un-covered side-shelf onto that nice cabinet for the amps, get 'em up just high enough to deflect the curiosity of cats and small children. That eliminates the need for fans.
BTW, that looks like a nice stash of vinyl in the background. What TT/cart combo are you using?

Thank you. I do love building stuff and actually have another level of this table in the other room with another (un modified Lenco L75). Height doesn't actually help us much though as our Bengal loves heights. It would help air flow though.
The turntable I use that's in this photo is a L75 with solid birch plinth, Audiomods arm and Ortofon 2m Black. Currently using a Les Box Yaqin 23b but I have a ph16 and an EAR 834p TRLH that are both very nearly finished.

Another fan of AudioMods arms. Amazing teamed up with the Kiseki Purple Heart. EAR have a great rep, let us know how that turns out.

I've been curious about the Kiseki Purple Heart but kind of have my heart set on a Soundsmith Zephyr MIMC Star at the moment.

On a side note, I still have a Rabco sl8 tangential arm that I need to set up. That one is destined to go on the slate plinthed Lenco once I finish that. Pretty set on a Decca cartridge with that though.
I've got 5 Lencos in total so I just might get around to the new Audiomods with a Kiseki.

So many projects. Not enough time.

Well, it's been pretty much 12 straight hours of listening (except for ~45 minutes to let them cool and move them). I have to say, I'm very, very pleased. I'm holding back from describing the aound until around the 50 hour mark but I haven't spent this much time listening to the Maggies since I got them.

Denizen wrote:I've been curious about the Kiseki Purple Heart but kind of have my heart set on a Soundsmith Zephyr MIMC Star at the moment.

On a side note, I still have a Rabco sl8 tangential arm that I need to set up. That one is destined to go on the slate plinthed Lenco once I finish that. Pretty set on a Decca cartridge with that though.
I've got 5 Lencos in total so I just might get around to the new Audiomods with a Kiseki.

So many projects. Not enough time.

I moved up from a Dynavector 17D3 which is no slouch but was absolutely stunned by the Purple Heart.

2 quick things. The amps are now on their own table (on top of a huge, slate slab) and a slight bit of hum in one amp was quickly and easily fixed.

As to the hum, Bob was lightening fast with replies so a huge thanks to him for that. In the end, it was simply the ground lug that's bolted down to the power transformer had a bit of soldered wire poking out that made it harder to fit my socket wrench on so I hadn't originally tightened it down as much as I thought I had.

Now with the volume at maximum, I get 42db of hum at each speaker from 1 meter away. For reference, music at half volume is 90db from my listening position (over 3 meters). Damn impressive if you ask me.

I have to say, the amps and Bob's support are everything I hoped for and more. I took a long time deciding on which amp or amps to go for and these spank everything that I was able to audition (Unison Research, Vincent, Cayin and the well respected Ayon).

I'm one very happy camper.

I currently have the maggies mg12 and 1.7s. They both have "upgraded" crossovers. I preferred the mg12 in triode and the 1.7 in pentode.

pedrocols wrote:I currently have the maggies mg12 and 1.7s.  They both have "upgraded" crossovers.  I preferred the mg12 in triode and the 1.7 in pentode.  

Thanks for that.
I definitely prefer pentode mode now. My 1.6qr with PG crossover are so much more musical and even across frequencies than stock that there's no desire to mess with it and pentode mode feels the truest to my Maggies capabilities.