Yes, of course.No, I do not think so
The intended outcome should have been giving others an idea which sound signature they can expect from these amps.Yes, of course.
So, what is the final outcome you realized?
For me, with these types of amps, I am just noticing synergy over anything else. Headphone will sound great on one and so-so on another. There truly isn't a one amp beats all perspective I notice.
I'm glad the 307 scales, the story fits perfectly.
Kevin Gilmore Megatron and Kevin Gilmore Stax T2, both built by Soren Brix
Megatron
1st Stage (12AU7/ECC82/(E80CC)): EH 12AU7
- Build according to KG design
- 450 V HV
- Golden Reference HV and LV Power supply
- Transformers: 400 VA + 2x 40 VA
- Tubes:
2nd Stage (12AX7/ECC83): ECC83 TELEFUNKEN Smooth Plates
Output (EL34): TESLA brown base (double O-getter)
CCS (EL34): Russian MULLARDS
T2
- Build according to KG redesigned T2, no replacement semiconductors
- 500 V KG power supply
- RK50 attenuator
- Tubes:
- Input (6922): JAN PHILIPS (Sylvania)
- Output (EL34): TESLA brown base (double O-getter)
Testing source
QOBUZ/TIDAL è SINGXER SU6 (DDC) è MUSETEC MH-DA005 (DA) è MT XLR out to T2
Cables (just for the record, no talent on my side to hear a noteworthy difference to previously used cheaper whatever cables…)
USB è DDC: AQ Coffee, I2S DDC è DA: AQ Carbon 48, XLR DA è MT: Inakustik NF-803, XLR Megatron è T2: ORB J10
Musetec runs with 2x Sabre 9038 pro, but is tuned to a warmer, less than for ESS typical forward/incisive signature. Matrix X-Sabre 3 with same 2x 9038 pro e.g. was a lot leaner and more incisive sounding. Overall sound signature I would describe as fairly neutral.
Music
Completely mixed, but I listened less to classical music.
Headphones
Stax SR307, 007A (2016, port + spring mod), 009, 009S, X9000
Sound
Treble
Extension and resolution seems similar on both, outstanding (maybe slight advantage for T2).
Treble on MT is more rounded and never causing fatigue, slightly subdued in comparison to T2. A completely grain free and sweet presentation.
T2 is presenting treble with more energy and dynamics, and most important, without harshness. Treble kicks in much stronger on T2 and more immediate, but appears not overdone in absolute terms.
Mids
Mids on MT appear to my ears as full, very liquid and “creamy” sounding. There is absolutely no shout to vocals (or anything), no matter how far the volume is cranked up.
On T2 the mids are tighter, less warm and big sounding, but maybe more articulated and focused. Probably many would say more neutral than MT, but I cannot say MT having colored mids in the reverse conclusion.
Bass
MT bass is precise, extends deep and delivers the fattest bass of all amps I listened to. T2 bass is most precise and extends deeper, bass is not as big and fat as MT. Bass impact is very prominent on MT (but not overdone), but is in comparison softer. T2 bass can hit you like a hammer, there is so much punch and rumble, if the music demands for it. MT is more polite in comparison. IMO the bass presentation of both suits all the a.m. headphones very well, and this alone sets both amps apart.
Overall
MT overall sound signature is relaxed and engaging at the same time, timbre is on the warm side. Both micro- and macrodynamics is great (be sure, all these EL34 are no statists). Already after plugging in MT for the first time, with the very first song it was clear to me that it is special in the way how harmonic its sounds. Tuning is on the softer side, very natural. There is not too much tube glare (unlike e.g. an unmodified SRM007t). The attribute coherency comes into mind, and that this is no one trick pony, more like experiencing one of the most “adult” sound of an amp I ever listened to, whether HP or speaker amp. Paired with great resolution all across the board, good transparency, delivering the most beautiful sound colours. Soundstage is very wide and deep, but exactly not like some overly exaggerated fuzzy tube amp staging one might have experienced. Next on the favorite list is how much body is given to the music, especially to the bass, resp. the lower frequencies in general. I guess this is not the kind of tuning one can generate by EQing other amps, this is organically implemented, and it suits the Staxes so well (even my 007A). MT is the perfect amp for (very) long listening sessions.
T2: Overall more (most!) energetic and more straight sounding. The analogy of an athlete, whose muscles are always tensioned comes to mind. This leads to a very lifelike (but not stressful) presentation, there seems to be not one millisecond delay from the record till it reaches the ear. Simply impressive!
T2 sounds a bit brighter/leaner than MT, having less of this “organic charm”, but there is even more transparency. Many might say T2 is more neutral. In comparison to the Carbon I experienced, T2 is less bright. I think there is enough warmth for most tastes and I think this makes a big difference. If some amps (also sources and transducers) suffer from either being highly dynamic but more lean sounding, while others from being warm but less dynamic, this is not the case with T2. I guess most would say T2 is where you want it to have. Compared to MT, stage on T2 is smaller, but probably more “correct” in size, with width and depth equally pronounced.
Mainly because of in comparison less treble energy of MT, listening at higher volume is possible and can be highly enjoyable. Both amps have excellent reverb, another ability which sets them apart from the other amps I could try before (speaking from memory though). Reverb on MT seems to be even more distinct than on T2.
T2 adds excitement already at low listening volumes. T2s most energetic presentation challenges you more, especially when cranking up the pot. You will not read a book while listening to music which is presented with this lifelike absolute authority.
Tube rolling
Megatron
Above mentioned tube configuration is based on the preceding words. Few other settings I tried:
1st stage
2nd stage
- E80CC instead of 12AU7. (Possible if the PS can handle the filament current of 0,6 A instead of 0,3 A. Using this tube results in slightly more gain.)
- I tried Valvo (Heerlen) and Tungsram E80CC. Both seem to be similar in sonics. This leads to a more engaging presentation, leaner and more treble sparkle compared to the EHs, but in the last time I feel it is maybe somehow not 100% “harmonic”. I would say its a preference thing. For now I switched back to EH 12AU7, because:
Output stage
- Coming from EH 12AX7 I switched to Telefunken ECC83 (Smooth plates), and this tube makes a difference. The Tele is adding resolution, treble extension, midrange presence and stage depth, tight bass. It is not a very tubey sounding tube I would say, but suits in this position very well, highly recommended. Together with a.m. E80CCs maybe too much of a good thing, bringing it to the lean side.
- I tried also Valvo ECC83 MC2 45° (Hamburg), this adds some 3D stage, but overall a bit too sleepy for my taste here.
(edit: Telefunken + Tungsram ECC82 and vintage Mullard ECC83 are on its way)
- Coming from Russian Mullards. They are overall pleasing in every regard, nothing to complain about. Recently I put in the Teslas, and they seem to be slightly more refined and clear sounding, a bit tighter in a good way. JJ EL34 II were no improvement (too lean). Overall there seems less influence compared to 1st and 2nd stage rolling, maybe no need to spend big money here. (Btw., GG was reacting much more on changing EL34)
- CCS: The Mullards I never changed.
- Receiving any experience from other MT owners would be very welcome.
T2
- No change of the input tubes so far (want to try Valvos)
- Changed the output from Russian Mullards to the Teslas. Not very much difference, but the Teslas I liked better. Also here overall a bit clearer, tighter with better treble resolution, but not night and day.
Synergy with Headphones (preliminary)
This was respective still is not an easy (but most enjoyable!) task, personal preference as mood and music are playing a role and there are many combinations + influence of tube rolling. I think I can already say that none of the mentioned headphones sounds less than at least very good on both amps, there are no real sonic mismatches.
Megatron
- X9000: Especially with this one I had my issues when getting it and I was not sure whether I would keep it. When MT arrived, I found missing synergy with X9000, so I forgot that idea. The full bodied character of MT with its thick mids was like it was made for X9000. Only area where I feel “only” good synergy, is in the treble. Both partners are having great resolution and extension, but are on the softer respective harmonic side.
- 009/009S (I will not differentiate between these at this point): IMO the perfect match! Period. I doubt anybody would call 009 bright or edgy in this combination and you would be surprised at which volume fatigue free listening is possible.
- 307: see 009, just wow. I would prefer 307 with MT over the round Staxes on certain “lesser” amps.
- 007A: IMO also a good match and no, I do not find the bass region too congested. But indeed a combination where bass heads might lift an eyebrow. Btw., MT is able to drive also 007 to unhealthy volume levels, and everything remains so listenable.
- (Once I could compare 007Mk1 (70xxx) and my 007A on MT and Carbon. 007MK1 I liked better on Carbon, but 007A (and all the other HPs) I preferred on MT.)
T2
- X9000: Very good match, but different synergy than with MT. As T2 adds a bit less body and thick mids to the music than MT, presentation is of course also leaner (but luckily not lean in absolute terms). Where X9000 really profits is in the bass and treble. Compared to 009, X9000 bass bleeds a bit into the lower mids (my perception), but the control, punch and precision of T2 cures that for me in a noteworthy way. The treble of X9000 was originally an issue for me. While resolution could not be better, treble is on the soft side and I missed macro dynamics, excitement. T2 cured this, treble is simply outstanding now.
- 009: Very very good match (at lower volume perfect). Two wild tigers are meeting, playing with their laser swords. All the qualities of T2 applied on 009 lead to a maximum exciting listening experience. For me the most impressive of all combinations at lower volume. Listening loudly for longer time can be too much of a good thing though. Right now I prefer 009S over 009 on T2, as it is slightly more “civil”, less challenging at higher volume.
- 307: Very good match, highly energetic and exciting sounding. Reasonable volume without fatigue is possible. And while I rate a 009 or 009S (which share a good part of their tuning with 307) higher, it is again surprising how much also this one is scaling with amplification. Taking into account I paid 250 € new, this thing is a kind of small wonder.
- 007A: You expect it, and yes, T2 fits to 007A perfectly. T2 transforms specially this one to a much more awake and precise transducer. Midrange recession is reduced, bass is juicy and accurate, the treble alive and just right. Having all the HP in front I ones was about to swap from 009 to 007, until I realized 007 was already on my head.
Overall thoughts:
I can easily agree with previous statements who called these two amplifiers outstanding, both are by far the ones I enjoy the most. Every headphone I tried sounds great in its own way with either amp, pairing is in the end as always a question of preference.
IMO T2 is not simply a better Megatron, as a Ferrari is no better Bentley. The full bodied and liquid tuning of MT is something very special and it suits probably the taste of many. On the other hand the energetic nature of T2 in combination with its balanced and lifelike sound is impossible to ignore and I´m sure will excite every listener.
Before T2 arrived here I thought at low volume listening most estat amplifiers do sound more similar to each other vs when cranked up, when more capable amps dominate due to lower distortion and all that. T2 somehow disproved this for me, I expect this alone might make some prefer T2 over MT.
I hope I could give a little bit of (preliminary) indication what to expect with these amps. Sorry for a not more polished language, and while reading it there are repititions…(never tried to describe sound in more than 2-3 lines before).
Btw, some might need to consider the WAF (wife acceptancy factor). I can say MT with its smaller one box solution is easier to “sell” for having it in the living room
Again, thank you Soren for providing these two excellent builts. Kevin, thank you for making these possible.
What are you trying to accomplish?
https://web.archive.org/web/2023011...inearz.com/stuff/transforming-the-stax-srd-7/
Ull love the Lundahl transformers, wipes the floor with the SRD which is pretty good once you rip out all the thermistor garbage but a lot of room for improvement as the small transformers struggle in the lower frequencies when you start to crank the volume. I followed the instructions in that link also when I started out.
Thanks a lot
Kevin Gilmore Megatron and Kevin Gilmore Stax T2, both built by Soren Brix
Megatron
1st Stage (12AU7/ECC82/(E80CC)): EH 12AU7
- Build according to KG design
- 450 V HV
- Golden Reference HV and LV Power supply
- Transformers: 400 VA + 2x 40 VA
- Tubes:
2nd Stage (12AX7/ECC83): ECC83 TELEFUNKEN Smooth Plates
Output (EL34): TESLA brown base (double O-getter)
CCS (EL34): Russian MULLARDS
T2
- Build according to KG redesigned T2, no replacement semiconductors
- 500 V KG power supply
- RK50 attenuator
- Tubes:
- Input (6922): JAN PHILIPS (Sylvania)
- Output (EL34): TESLA brown base (double O-getter)
Testing source
QOBUZ/TIDAL è SINGXER SU6 (DDC) è MUSETEC MH-DA005 (DA) è MT XLR out to T2
Cables (just for the record, no talent on my side to hear a noteworthy difference to previously used cheaper whatever cables…)
USB è DDC: AQ Coffee, I2S DDC è DA: AQ Carbon 48, XLR DA è MT: Inakustik NF-803, XLR Megatron è T2: ORB J10
Musetec runs with 2x Sabre 9038 pro, but is tuned to a warmer, less than for ESS typical forward/incisive signature. Matrix X-Sabre 3 with same 2x 9038 pro e.g. was a lot leaner and more incisive sounding. Overall sound signature I would describe as fairly neutral.
Music
Completely mixed, but I listened less to classical music.
Headphones
Stax SR307, 007A (2016, port + spring mod), 009, 009S, X9000
Sound
Treble
Extension and resolution seems similar on both, outstanding (maybe slight advantage for T2).
Treble on MT is more rounded and never causing fatigue, slightly subdued in comparison to T2. A completely grain free and sweet presentation.
T2 is presenting treble with more energy and dynamics, and most important, without harshness. Treble kicks in much stronger on T2 and more immediate, but appears not overdone in absolute terms.
Mids
Mids on MT appear to my ears as full, very liquid and “creamy” sounding. There is absolutely no shout to vocals (or anything), no matter how far the volume is cranked up.
On T2 the mids are tighter, less warm and big sounding, but maybe more articulated and focused. Probably many would say more neutral than MT, but I cannot say MT having colored mids in the reverse conclusion.
Bass
MT bass is precise, extends deep and delivers the fattest bass of all amps I listened to. T2 bass is most precise and extends deeper, bass is not as big and fat as MT. Bass impact is very prominent on MT (but not overdone), but is in comparison softer. T2 bass can hit you like a hammer, there is so much punch and rumble, if the music demands for it. MT is more polite in comparison. IMO the bass presentation of both suits all the a.m. headphones very well, and this alone sets both amps apart.
Overall
MT overall sound signature is relaxed and engaging at the same time, timbre is on the warm side. Both micro- and macrodynamics is great (be sure, all these EL34 are no statists). Already after plugging in MT for the first time, with the very first song it was clear to me that it is special in the way how harmonic its sounds. Tuning is on the softer side, very natural. There is not too much tube glare (unlike e.g. an unmodified SRM007t). The attribute coherency comes into mind, and that this is no one trick pony, more like experiencing one of the most “adult” sound of an amp I ever listened to, whether HP or speaker amp. Paired with great resolution all across the board, good transparency, delivering the most beautiful sound colours. Soundstage is very wide and deep, but exactly not like some overly exaggerated fuzzy tube amp staging one might have experienced. Next on the favorite list is how much body is given to the music, especially to the bass, resp. the lower frequencies in general. I guess this is not the kind of tuning one can generate by EQing other amps, this is organically implemented, and it suits the Staxes so well (even my 007A). MT is the perfect amp for (very) long listening sessions.
T2: Overall more (most!) energetic and more straight sounding. The analogy of an athlete, whose muscles are always tensioned comes to mind. This leads to a very lifelike (but not stressful) presentation, there seems to be not one millisecond delay from the record till it reaches the ear. Simply impressive!
T2 sounds a bit brighter/leaner than MT, having less of this “organic charm”, but there is even more transparency. Many might say T2 is more neutral. In comparison to the Carbon I experienced, T2 is less bright. I think there is enough warmth for most tastes and I think this makes a big difference. If some amps (also sources and transducers) suffer from either being highly dynamic but more lean sounding, while others from being warm but less dynamic, this is not the case with T2. I guess most would say T2 is where you want it to have. Compared to MT, stage on T2 is smaller, but probably more “correct” in size, with width and depth equally pronounced.
Mainly because of in comparison less treble energy of MT, listening at higher volume is possible and can be highly enjoyable. Both amps have excellent reverb, another ability which sets them apart from the other amps I could try before (speaking from memory though). Reverb on MT seems to be even more distinct than on T2.
T2 adds excitement already at low listening volumes. T2s most energetic presentation challenges you more, especially when cranking up the pot. You will not read a book while listening to music which is presented with this lifelike absolute authority.
Tube rolling
Megatron
Above mentioned tube configuration is based on the preceding words. Few other settings I tried:
1st stage
2nd stage
- E80CC instead of 12AU7. (Possible if the PS can handle the filament current of 0,6 A instead of 0,3 A. Using this tube results in slightly more gain.)
- I tried Valvo (Heerlen) and Tungsram E80CC. Both seem to be similar in sonics. This leads to a more engaging presentation, leaner and more treble sparkle compared to the EHs, but in the last time I feel it is maybe somehow not 100% “harmonic”. I would say its a preference thing. For now I switched back to EH 12AU7, because:
Output stage
- Coming from EH 12AX7 I switched to Telefunken ECC83 (Smooth plates), and this tube makes a difference. The Tele is adding resolution, treble extension, midrange presence and stage depth, tight bass. It is not a very tubey sounding tube I would say, but suits in this position very well, highly recommended. Together with a.m. E80CCs maybe too much of a good thing, bringing it to the lean side.
- I tried also Valvo ECC83 MC2 45° (Hamburg), this adds some 3D stage, but overall a bit too sleepy for my taste here.
(edit: Telefunken + Tungsram ECC82 and vintage Mullard ECC83 are on its way)
- Coming from Russian Mullards. They are overall pleasing in every regard, nothing to complain about. Recently I put in the Teslas, and they seem to be slightly more refined and clear sounding, a bit tighter in a good way. JJ EL34 II were no improvement (too lean). Overall there seems less influence compared to 1st and 2nd stage rolling, maybe no need to spend big money here. (Btw., GG was reacting much more on changing EL34)
- CCS: The Mullards I never changed.
- Receiving any experience from other MT owners would be very welcome.
T2
- No change of the input tubes so far (want to try Valvos)
- Changed the output from Russian Mullards to the Teslas. Not very much difference, but the Teslas I liked better. Also here overall a bit clearer, tighter with better treble resolution, but not night and day.
Synergy with Headphones (preliminary)
This was respective still is not an easy (but most enjoyable!) task, personal preference as mood and music are playing a role and there are many combinations + influence of tube rolling. I think I can already say that none of the mentioned headphones sounds less than at least very good on both amps, there are no real sonic mismatches.
Megatron
- X9000: Especially with this one I had my issues when getting it and I was not sure whether I would keep it. When MT arrived, I found missing synergy with X9000, so I forgot that idea. The full bodied character of MT with its thick mids was like it was made for X9000. Only area where I feel “only” good synergy, is in the treble. Both partners are having great resolution and extension, but are on the softer respective harmonic side.
- 009/009S (I will not differentiate between these at this point): IMO the perfect match! Period. I doubt anybody would call 009 bright or edgy in this combination and you would be surprised at which volume fatigue free listening is possible.
- 307: see 009, just wow. I would prefer 307 with MT over the round Staxes on certain “lesser” amps.
- 007A: IMO also a good match and no, I do not find the bass region too congested. But indeed a combination where bass heads might lift an eyebrow. Btw., MT is able to drive also 007 to unhealthy volume levels, and everything remains so listenable.
- (Once I could compare 007Mk1 (70xxx) and my 007A on MT and Carbon. 007MK1 I liked better on Carbon, but 007A (and all the other HPs) I preferred on MT.)
T2
- X9000: Very good match, but different synergy than with MT. As T2 adds a bit less body and thick mids to the music than MT, presentation is of course also leaner (but luckily not lean in absolute terms). Where X9000 really profits is in the bass and treble. Compared to 009, X9000 bass bleeds a bit into the lower mids (my perception), but the control, punch and precision of T2 cures that for me in a noteworthy way. The treble of X9000 was originally an issue for me. While resolution could not be better, treble is on the soft side and I missed macro dynamics, excitement. T2 cured this, treble is simply outstanding now.
- 009: Very very good match (at lower volume perfect). Two wild tigers are meeting, playing with their laser swords. All the qualities of T2 applied on 009 lead to a maximum exciting listening experience. For me the most impressive of all combinations at lower volume. Listening loudly for longer time can be too much of a good thing though. Right now I prefer 009S over 009 on T2, as it is slightly more “civil”, less challenging at higher volume.
- 307: Very good match, highly energetic and exciting sounding. Reasonable volume without fatigue is possible. And while I rate a 009 or 009S (which share a good part of their tuning with 307) higher, it is again surprising how much also this one is scaling with amplification. Taking into account I paid 250 € new, this thing is a kind of small wonder.
- 007A: You expect it, and yes, T2 fits to 007A perfectly. T2 transforms specially this one to a much more awake and precise transducer. Midrange recession is reduced, bass is juicy and accurate, the treble alive and just right. Having all the HP in front I ones was about to swap from 009 to 007, until I realized 007 was already on my head.
Overall thoughts:
I can easily agree with previous statements who called these two amplifiers outstanding, both are by far the ones I enjoy the most. Every headphone I tried sounds great in its own way with either amp, pairing is in the end as always a question of preference.
IMO T2 is not simply a better Megatron, as a Ferrari is no better Bentley. The full bodied and liquid tuning of MT is something very special and it suits probably the taste of many. On the other hand the energetic nature of T2 in combination with its balanced and lifelike sound is impossible to ignore and I´m sure will excite every listener.
Before T2 arrived here I thought at low volume listening most estat amplifiers do sound more similar to each other vs when cranked up, when more capable amps dominate due to lower distortion and all that. T2 somehow disproved this for me, I expect this alone might make some prefer T2 over MT.
I hope I could give a little bit of (preliminary) indication what to expect with these amps. Sorry for a not more polished language, and while reading it there are repititions…(never tried to describe sound in more than 2-3 lines before).
Btw, some might need to consider the WAF (wife acceptancy factor). I can say MT with its smaller one box solution is easier to “sell” for having it in the living room
Again, thank you Soren for providing these two excellent builts. Kevin, thank you for making these possible.
Probably about right with the bias, the multimeter’s input impedance will be dragging it down… I was never able to get decent readings even before the ballast resistor…
Yup, definitely have background hum with the Lambda Pros. Not so much with the less efficient 007/X9000.
You can get rid of the hum with an isolation or step down transformer which decouples it from mains. I have found a clean bias is just as important as the transformers as it sets the stage for everything else. I did a couple of iterations until I settled on my current setup.
I'll be trying a high power solid state speaker amp today too, my Anthem MRX540. It's an AVR meant for home theater but it's a surprisingly capable 2ch amp for music as well. 100wpc into 5 channels, fat toroidal transformers, class AB, 32-bit 768kHz DAC. I'm always pleased whenever I directly connect headphones to its speaker terminals.
