Finally my SOHA II
Seeing as the original "splurb" was primarily focused on the amps that have gone to new homes, I decided to revamp the details of the SOHA II
First off, this is a superb amplifier. I am not selling it because I am unhappy with the sound, it is merely the process of DIY. I am no longer based in a lab (where the amp was used) and this amp will soon be gathering dust once again.
The finer details of the amplifier can be read on Alex's web site where he does a great job of detailing the technicalities of the design. For those unfamiliar with the amplifier, it is a hybrid which in this case means that the tube is providing the voltage gain while the solid state output supplies the necessary current to drive any headphones you care to connect. Low impedance, high impedance, notoriously difficult to drive ( yes even the new and vintage orthodynamics ) The tube has a reasonable plate voltage of 90V. The bias current is 3mA which keeps most tubes happy. ( to contrast to the original SOHA which ran at 40V and 1mA ) The output buffer is a beefy single ended design heavily biased into Class A ( not an opamp ). It has an integral servo to keep the offset at zero and an ouput relay to protect your headphones during power up and down. The tube heater voltage is adjustable between 6.3V and 12.6V , making the number of tubes which can be rolled in this amp quite extensive.
The front and rear face plates are oak and there is a plexiglass window in the front to allow you to visualize the tubes and some of the electronics. There are both top and bottom vents for heat management but I included a silent running fan in situations where the ambient temperature is higher than anticipated. ( the lab where I had this amp used to generate a lot of heat ) It uses a good quality transformer ( a torroid ) from avel lindberg. I added bias point on the rear of the amp should you wish to adjust the bias of the buffer - this allows easy access to the necessary points on the board.
The amp is built into a solid steel chassis ( it is surprisingly heavy for such a small amp ). I have incorporated an alien dac into the chassis which makes this an ideal desktop amp , a switch on the rear switches between the usb dac and the RCA input.
I will say that the sound is excellent but there is enough praise for it's performance that I will allow you to read the thread to gleam a more impartial opinion.
PM me if interested.
..dB
******
Another Cavalli tube hybrid , this build incorporates an “alien” usb dac making it an ideal desktop amp. The build is pretty standard, it is set for a B+ of 90V, cathode current of 3mA and buffers are biased into class A ~ 60mA ( yes it runs hot ). I included a “silent” running 12V fan inside that chassis but have not found the need to use it. It is there if needed but runs less than silently. ( cannot be heard over music but is noticeable when on )
This is a solid little amp and a great performer.
Price : SOLD
( I will include a selection of tubes for tube rollers )
All 3 of these amps are capable of driving any headphone you care to use, I have used them with ATH 2000 , GS1000, AKG K1000 , K501 , many many orthodynamics – all have enough gain and current to handle these loads.
************************************************** *************************************
I have been going back and forth about this for the past few weeks and this seems like the only way to go.
This is an interest check for 2 of the amps listed here, I will keep one.
First up is my Stacker. - SOLD
This is a one off, most likely never to be repeated. There has been much said about it in various forums and in my unbiased opinion, it is the best amplifier EVAR
.
It is not without its quirks and anyone interested should know a few things. **** see edit below*****It has a voltage spike when turned on or off ( much like any hybrid ) , so you need to be sure to unplug your headphones before / after use. The current potentiometer is not fantastic and I will replace it if it ends up finding a new owner. It has been through the wars and revived again – the last time I shipped it out, it was not treated well by usps upon it’s return. The result is there are a few battle wounds. It has been working and functional without any concerns since I initially built it. (3 odds years ago) It can use most 12AU7 noval variants as well as the 6922 series. ie 12V heaters 12AU7, 5814, 6680, 8416, etc 6.3V heaters – 6DJ8, 6CG7, 6FQ7, 6GU7 ( my preferred tube is the 6CG7 ) . The undercarriage of the amp is open, if you stick your fingers under the chassis it will likely kill you – there are exposed high voltage points.
The amp is built p2p and was never intended to be owned by anyone other than myself. Excuses excuses but basically this amp is not a Ferrari, Nate or Headamp build, it is however pretty solid.
Price : sold
The EHHA is next up .
This amp probably invested the most of my time. The details of the amp and design are over on Alex’s web site. The build is unique and will appeal to some but not others – front and rear plates are solid copper (~10mm), my original plan was to use an acid bath and create a patina which would have been more of an art work but my initial trials proved my a terrible metalsmith/artist potential and I did not go down that route. The amp has off board heatsinks to give it a bit of a vintage/steampunk look. The cost of the raw metal is OTT but it sure created the look I wanted.
My idea was to have a small foot print amp which was attached to the psu via an umbilical. The psu chassis is nothing special, a recycled chassis with a coat of paint. The psu houses an S22 with the higher VA rated torroidal transformer. The S22 suplies the voltage rails for the amp itself. I built a DC heater supply capable of supplying up to 3A, it is a 12.6V supply which runs the heaters in series , allowing 6.3V to each tube. Tubes compatible with this amp are the 6922/6DJ8, 6GM8 and 6H30.
Quirks; no real quirks other than the DC awareness at power up down ( again a hybrid tendency ) So plug & unplug headphones as with Stacker. The psu chassis is a little scratched up and I will be happy to paint it prior to shipping it off. Oh, it has 3 power switches – the heaters need to come up before the rails , I thus have a main power toggle , then a heater toggle and finally a rail toggle which powers the amp rails – leave about 30seconds between powering the heater and the rails. Nothing will blow up if you don’t do this but it is better practice to power it up sequentially and limit the possibility that the amp swings to one of the rails.
Price SOLD
Please PM me if you are interested, based on response, I will sell off 2.
Thanks..dB
***EDIT***
I have had a few questions about the voltage spike stability issues
This spike I mention is typical for many builds - most any of the hybrids will have a voltage spike, YAHA, Millett, Cavalli - they all do it. Some use a relay on the output to delay the output connection to the headphones , this spike settles very quickly due to the servo, it has no output capacitor. The buffer on this amp is stable, I have been using it since 2007 and it has been mostly without any issues ( I say mostly as it did come back in pieces after one shipping experience and I had to rebuild it. ) I was using an output relay for a while but the e12 was a serious pia tripping for no reason, this has been a not too uncommon problem for several people and I opted to remove it and unplug my headphones.
I mentioned the amp can kill you , much in the same way as a toaster will kill you if you stick your fingers where they don't belong. The amp is not inherently dangerous but high voltage electricity is. I may even fashion a protective cover for my own piece of mind.
Seeing as the original "splurb" was primarily focused on the amps that have gone to new homes, I decided to revamp the details of the SOHA II
First off, this is a superb amplifier. I am not selling it because I am unhappy with the sound, it is merely the process of DIY. I am no longer based in a lab (where the amp was used) and this amp will soon be gathering dust once again.
The finer details of the amplifier can be read on Alex's web site where he does a great job of detailing the technicalities of the design. For those unfamiliar with the amplifier, it is a hybrid which in this case means that the tube is providing the voltage gain while the solid state output supplies the necessary current to drive any headphones you care to connect. Low impedance, high impedance, notoriously difficult to drive ( yes even the new and vintage orthodynamics ) The tube has a reasonable plate voltage of 90V. The bias current is 3mA which keeps most tubes happy. ( to contrast to the original SOHA which ran at 40V and 1mA ) The output buffer is a beefy single ended design heavily biased into Class A ( not an opamp ). It has an integral servo to keep the offset at zero and an ouput relay to protect your headphones during power up and down. The tube heater voltage is adjustable between 6.3V and 12.6V , making the number of tubes which can be rolled in this amp quite extensive.
The front and rear face plates are oak and there is a plexiglass window in the front to allow you to visualize the tubes and some of the electronics. There are both top and bottom vents for heat management but I included a silent running fan in situations where the ambient temperature is higher than anticipated. ( the lab where I had this amp used to generate a lot of heat ) It uses a good quality transformer ( a torroid ) from avel lindberg. I added bias point on the rear of the amp should you wish to adjust the bias of the buffer - this allows easy access to the necessary points on the board.
The amp is built into a solid steel chassis ( it is surprisingly heavy for such a small amp ). I have incorporated an alien dac into the chassis which makes this an ideal desktop amp , a switch on the rear switches between the usb dac and the RCA input.
I will say that the sound is excellent but there is enough praise for it's performance that I will allow you to read the thread to gleam a more impartial opinion.
PM me if interested.
..dB
******
Another Cavalli tube hybrid , this build incorporates an “alien” usb dac making it an ideal desktop amp. The build is pretty standard, it is set for a B+ of 90V, cathode current of 3mA and buffers are biased into class A ~ 60mA ( yes it runs hot ). I included a “silent” running 12V fan inside that chassis but have not found the need to use it. It is there if needed but runs less than silently. ( cannot be heard over music but is noticeable when on )
This is a solid little amp and a great performer.
Price : SOLD
( I will include a selection of tubes for tube rollers )
All 3 of these amps are capable of driving any headphone you care to use, I have used them with ATH 2000 , GS1000, AKG K1000 , K501 , many many orthodynamics – all have enough gain and current to handle these loads.
************************************************** *************************************
I have been going back and forth about this for the past few weeks and this seems like the only way to go.
This is an interest check for 2 of the amps listed here, I will keep one.
First up is my Stacker. - SOLD
This is a one off, most likely never to be repeated. There has been much said about it in various forums and in my unbiased opinion, it is the best amplifier EVAR
.It is not without its quirks and anyone interested should know a few things. **** see edit below*****It has a voltage spike when turned on or off ( much like any hybrid ) , so you need to be sure to unplug your headphones before / after use. The current potentiometer is not fantastic and I will replace it if it ends up finding a new owner. It has been through the wars and revived again – the last time I shipped it out, it was not treated well by usps upon it’s return. The result is there are a few battle wounds. It has been working and functional without any concerns since I initially built it. (3 odds years ago) It can use most 12AU7 noval variants as well as the 6922 series. ie 12V heaters 12AU7, 5814, 6680, 8416, etc 6.3V heaters – 6DJ8, 6CG7, 6FQ7, 6GU7 ( my preferred tube is the 6CG7 ) . The undercarriage of the amp is open, if you stick your fingers under the chassis it will likely kill you – there are exposed high voltage points.
The amp is built p2p and was never intended to be owned by anyone other than myself. Excuses excuses but basically this amp is not a Ferrari, Nate or Headamp build, it is however pretty solid.
Price : sold
The EHHA is next up .
This amp probably invested the most of my time. The details of the amp and design are over on Alex’s web site. The build is unique and will appeal to some but not others – front and rear plates are solid copper (~10mm), my original plan was to use an acid bath and create a patina which would have been more of an art work but my initial trials proved my a terrible metalsmith/artist potential and I did not go down that route. The amp has off board heatsinks to give it a bit of a vintage/steampunk look. The cost of the raw metal is OTT but it sure created the look I wanted.
My idea was to have a small foot print amp which was attached to the psu via an umbilical. The psu chassis is nothing special, a recycled chassis with a coat of paint. The psu houses an S22 with the higher VA rated torroidal transformer. The S22 suplies the voltage rails for the amp itself. I built a DC heater supply capable of supplying up to 3A, it is a 12.6V supply which runs the heaters in series , allowing 6.3V to each tube. Tubes compatible with this amp are the 6922/6DJ8, 6GM8 and 6H30.
Quirks; no real quirks other than the DC awareness at power up down ( again a hybrid tendency ) So plug & unplug headphones as with Stacker. The psu chassis is a little scratched up and I will be happy to paint it prior to shipping it off. Oh, it has 3 power switches – the heaters need to come up before the rails , I thus have a main power toggle , then a heater toggle and finally a rail toggle which powers the amp rails – leave about 30seconds between powering the heater and the rails. Nothing will blow up if you don’t do this but it is better practice to power it up sequentially and limit the possibility that the amp swings to one of the rails.
Price SOLD
Please PM me if you are interested, based on response, I will sell off 2.
Thanks..dB
***EDIT***
I have had a few questions about the voltage spike stability issues
This spike I mention is typical for many builds - most any of the hybrids will have a voltage spike, YAHA, Millett, Cavalli - they all do it. Some use a relay on the output to delay the output connection to the headphones , this spike settles very quickly due to the servo, it has no output capacitor. The buffer on this amp is stable, I have been using it since 2007 and it has been mostly without any issues ( I say mostly as it did come back in pieces after one shipping experience and I had to rebuild it. ) I was using an output relay for a while but the e12 was a serious pia tripping for no reason, this has been a not too uncommon problem for several people and I opted to remove it and unplug my headphones.
I mentioned the amp can kill you , much in the same way as a toaster will kill you if you stick your fingers where they don't belong. The amp is not inherently dangerous but high voltage electricity is. I may even fashion a protective cover for my own piece of mind.
wow .
