As you don't know realy what quality you have to expect from an amplifier, only by viewing the schematics, it is always usefull to get the opinion of others. So here is the possibility for DIYer to confront amplifieres from different designers and to advance a personal and objective opinion. So if you have the possibility to compare, you are welcome to give an opinion, together with some pictures of the amplifiers.





Here a review to the Sirius V4 from “thinker”:

and a very detailed review in german from “kathala”:







Mr. Buchmann from swizerland is owner of a Stax SRM007t. He has built the Alpha Centauri V2.0 and made the following experience (translated from the german):

The result has convinced me completely. The sound of the hybridamp is clear, outlined and transparent, with a transparent bass that goes down deep. The stage is wide and deep, the staggering of the instruments is precise. Even at complex passages the structure is maintained.
Compared to the SRM007t there is a major difference audible. The sound of the SRM007t is more flat and unclean. Now the Omega is everything I always have wished for.



To contact Mr. Buchmann please use his homepage




Mr. Dierkes
  is owner of a SRM-1/MK-2 and also of a Jecklin Float Headphone. He has built the Canopus to drive the JF and a STAX Lambda professional and made the following experience (translated from the german):


First it was difficult to me to find a difference between the Jecklin Float driver unit and the RTR400. But after a short warm up time it turned out: The high frequencies of the RTR400 especially when listening to trumpets and strings sound more natural and clear. The bass is more precise and not so slack.

The Stax too sounds more balanced and has a wider range, maybe a little bit euphonic too. The sharpness of the SRM-1/MK-2 is gone. It’s a tremendous amusement to listen to the RTR400, all in all a great benefit in sound.

For the input stage I use  TAD 12AT7 / ECC81 Premium Selected (, for the output tubes selected 6S4A from RCA ( The enclosure I bought at  (10 mm Alu-Frontplate) Front- and Backplate have been worked out at The big ALU-knobs come from


Here are some pictures of the completed RTR400 from Mr. Dierkes:

The email-address of Mr. Dierkes is  (remove the underline in the address).





Mr. Seyler
  has build both Sirius and Alpha Centauri V1.0, both are running with regulated pws and arrives at the following conclusion (translated from the german):


As you can see on the picture I’m using the BU2722AF as output transistor for the transistoramp. Both amps are supplied by one pws, and the headphone is connected to a switch, that allows me to switch from one amp to the other. So I’m able to directly compare both amps. Even after listening for hours and with different styles of music I was not able to figure out one amp to be the better one. My opinion was reinforced by three other persons that enjoy to listen to music too. All were filled with ethusiasm from the amps. I will order the suggested transformer and put all in a enclosure. Two of my fellows are now also owner of a stax, that means two additional amps have to be build.

Added on 01.08.08 from Tobias Seyler, the nephew of Mr. Seyler:

I want to advance my opinion to the Sirius amplifier.

The difference between the amplifiers (your transistoramp and SRM-1/MK-2) is marginal. After long audition I noticed a light difference. Your amplifier has a better impulse reproduction. The difference is not as major as the difference between two headphones, especially between dynamic and electrostatic, but you can hear it clearly. Also the voices sound more realistic, the mid range is more exact. In bass, both amplifier sound equal, also in high frequencies. But now the topic that separates both amplifiers: The resolution. The sound stage seams much bigger, the instruments are better seperated, you can better point out there position.

All in all the difference in sound is audible and not only measurable, as I suspected.


Here a pictures of the not yet completely finished amp of Mr. Seyler
Hybridamp und Transistoramp
from the finished
new edition of the


The EAGLE-Layouts for the amps from Mr. Seyler you can download here:
Hybridamp (with heating voltage regulater and delay on board)

The email-address of Mr. Seyler is:  (remove the underline in the address)




Mr. Lihl  is owner of a Stax SRM 313. He has built my Alpha Centauri and made the following experience (translated from the german):


The hybridamp seems to sound significant better.(voices are smoother, tremendously resolution). The hissing ess and the aggressiveness of the SRM 313 are not present. Amazing! I'm completely enthusiastic. My wife (she does not have anything to do with highend) is on the same opinion that voices sound smoother. Can this be? This time the amplifier is connected to the pre-out of my DIY preamplifier. I'm not familiar with other STAX-Amplifiers, but it would be interesting to make a comparison. Indeed the hybridamp can be ranged at least one class above the SRM 313. I have to pay you the biggest compliment. I did not expect this quality. Furthermore the amplifier will be placed in a nice housing.


Here are some pictures of the not yet completely finished Alpha Centauri from Mr. Lihl:


The email-address of Mr. Lihl is: (remove the underline in the address).



Mr. Link  is owner of a Stax SRM T1S. He built the Canopus and made the following experience (translated from the german):


For the start I want to thank you for the great construction manual.
That's exactly that what I was looking for.
At first go I like the RTR400 more then the SRM T1S - very nice resolution and more volume in the low frequencies.
The optical characteristic has changed (photo), but inside there are the original boards.

The first tests I made with my mothballed Sony CDP XA50ES and was totally enthusiastic. Then I connected it to my Accuphase DP67 - hmmmm sounds in this combination a little bit too restrained - maybe the tube sound you mentioned on your homepage. With my Sony it blends better - especially with the filter 3a (switchable digital filter). Certainly it depends too a little bit on the kind of music you listen to. The most demonstrative differences RTR400 to T1s: Absolutely impressive in deep bass - drums and bassguitars are more authentic.

In the meantime I have experimented with the input tube TU1.
Initially I used the 12ATWC from EH, this used to become better after 10 hours on-time at the Accuphase - in the internet I found a hint that this tube gets best after 50 hours on-time! Then I used the standard 12AT7 from EH, but sounded a litte bit to harsh. Last I tested two used Siemens ECC81 - sound wonderful at the Accuphase - very consistent over the whole range!

Added on 27.03.07:

My 6s4a are from RCA - they suit me very well.
GE I have too - testet them these days - oh well...
The RCA plays significant better!
Meantime I have got some Siemens for TU2 - but with 4 Siemens it somehow was not the right thing.
Now I have replaced TU2 with some american 6201 (labeld with National, I think they are from GE)
Now this combination I like very very much - for the first time I will keep this combination!
The whole thing rises and falls with the tubes that are used - I did not expect this!
From highend to oh well it's all possible!!


And so does Mr. Link’s Canopus look like:





Mr. Maindok  has build two Gilmore-amplifier and the Alpha Centauri and arrives at the following conclusion (translated from the german):


I have checked the transfer behavior of my three amps and the result looks like this.

The AC coupled tubeamp brings up the clearest square wave without any tendency to overshooting. Unfortunately it misses the deep frequencies and the maximum output swing (-3db at 45KHz).

From the Blue Hawaii I was badly disappointed - the 3dB bandwidth is already reached at 22KHz.
I have build the design from HeadAmp, with a reduced BIAS for the Tubes, 22pF and 220pF respectively at the anode in order to contain the amplifier.
Mr. Gilmore did not envisage C's in his layout, but then suggests to use 400-500pF capasitors.

Your hybridamp now realy provides the desired sound characteristics. It combines the saturated, structured bass of the BH and the high areal resolution of the AC coupled tubeamp. Moreover it is small - has low drift and is warmed up within short time.

Unfortunately I can not offer results of a distortion level measuring - the distortion level of my signal generator exceeds the expected distortion level of the amplifiers.

On search for the reason for the badly areal resolution of the BH I made the following discovery.

If you examine the phase shift between the two stator outputs of the amplifier (XY input at the oscilloscope - Lissajous), you receive a clear straight line in nearly all conditions at the output of the AC coupled tubeamp. The hybridamp shows two small loops at the ends of the line at high output swing - the BH instead draws the prettiest 8s on the screen. Accordingly an impulse will be reproduced lower and wider as it should be. Probably this is the reason why the BH sounds so smooth.


The amps of Mr. Maindok look like this:

Blue Hawaii
AC-coupled Tubeamp
(with a regulated powersupply from thel-electronic)