exact andrew, life is learning till the last hour.
mouser was fast, the 68ohm resistors are soldered for r2/r3 and now everything is perfect. have a bias around 100ma and the offset is stable floating +- 0.4mv after 2h. i didn't need to change r10/r21 to get the bias down to 0v. amp gets warm but verry moderat due the big heatsink. now i have to wait for the 10k poti to arrive.
would like to thanks prasi and xrk971 for your help. sorry for my laziness didn't match the mosfet, often the adjustment range is big enough for a 2 mosfet design, learned something new. sorry prasi that you get troubled asking questions for me.
nedd to punish myselft for that:
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
Don't be too hard on yourself. A two MOSFET in push pull should not require matching to achieve zero volts DC offset. The design should have enough adjustment range built in. Many N and P channels don't even have the same range of Vgs so can't match. Like IRFP240/9240. One is in 3v range and other is closer to 4v. Just differences in N and P channel.
exact andrew, life is learning till the last hour.
mouser was fast, the 68ohm resistors are soldered for r2/r3 and now everything is perfect. have a bias around 100ma and the offset is stable floating +- 0.4mv after 2h. i didn't need to change r10/r21 to get the bias down to 0v. amp gets warm but verry moderat due the big heatsink. now i have to wait for the 10k poti to arrive.
would like to thanks prasi and xrk971 for your help. sorry for my laziness didn't match the mosfet, often the adjustment range is big enough for a 2 mosfet design, learned something new. sorry prasi that you get troubled asking questions for me.
nedd to punish myselft for that:
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
i should not mount unmatched mosfet. i should not mount unmatched mosfet. i should not mount unmatched mosfet.
Hi rumina , sorry for being away, i was a bit busy and had an exhilarating time making preparations and attending my child's annual day at school.
I want to congratulate you on getting it working to your liking.
Dont punish yourself, you have done a wonderful job in finding how to build for rest of the builders. i am grateful for that.
You have taken risk in building this untested pcb and come out with flying colors.
do let your listening impressions be known here for the benefit of rest of the builders.
I request you to post your final values/changes here for psu and ha both so that others may follow
as you are holding the Flambeau for this PCB.reg
Prasi
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Hi rumina , sorry for being away, i was a bit busy and had an exhilarating time making preparations and attending my child's annual day at school.
I want to congratulate you on getting it working to your liking.
Dont punish yourself, you have done a wonderful job in finding how to build for rest of the builders. i am grateful for that.
You have taken risk in building this untested pcb and come out with flying colors.
do let your listening impressions be known here for the benefit of rest of the builders.
I request you to post your final values/changes here for psu and ha both so that others may follow
reg
Prasi
for the nazar psu with the prasi pcb take care of the wrong marked diode (d10) all 4 diodes point in the same direction (d9-d12). i would take 68ohm resistors for r2,r3. i could archive a adjustment range up to 120ma bias (or 1.2v over r13), very stable offset. the adjustment range is narrow, would be nice to be more flexible and get high as 250ma.
i took a first listen with a alps pot (which i don't like) and it's a nice quite neutral sounding amp (a little touch warm sounding, but less then a big f5), post better feedback when a better pot is in.
power output is ideal for dynamic low ohms headphones, wiht 15v it's more a medium-low power amp, likes dynamic headphones better then planar, it's a very quiet amp.
so the potentiometer arrived yesterday and the amp is finished.
had a quiet 50hz hum at the beginning due the small case that was inducted from the trafo, shielding it with some mu-metal was a easy fix. not a new problem from me when you like small cases.
the best pairing for me is with the fostex th-900, gives a detailed sound with a good soundstage, bass goes controlled down but don't touches the super deepest parts (only few amps that i know can do that). the amp is neutral and only a touch of warmth comes with it, so with the fostex which has a strong presence that is a very fine match. more demanding headphones likes planars are ok but the amp is loosing a bit control with these headphones. i would say the amp plays in the leauge of the th-900, above it's a bit tricky. due the nice pairing with the fosex the project is finished for me.
i think the design could deliver more, with my experience i would try to get the bias higher (mine i now maxed at out around 135ma) and let the mosfet run hot. i had amps that gained a lot of authority and easiness setting the bias high.
don't fortget every build is different and its based of personal preferences not absolut truth, one likes sport cars the other limousines.
had a quiet 50hz hum at the beginning due the small case that was inducted from the trafo, shielding it with some mu-metal was a easy fix. not a new problem from me when you like small cases.
the best pairing for me is with the fostex th-900, gives a detailed sound with a good soundstage, bass goes controlled down but don't touches the super deepest parts (only few amps that i know can do that). the amp is neutral and only a touch of warmth comes with it, so with the fostex which has a strong presence that is a very fine match. more demanding headphones likes planars are ok but the amp is loosing a bit control with these headphones. i would say the amp plays in the leauge of the th-900, above it's a bit tricky. due the nice pairing with the fosex the project is finished for me.
i think the design could deliver more, with my experience i would try to get the bias higher (mine i now maxed at out around 135ma) and let the mosfet run hot. i had amps that gained a lot of authority and easiness setting the bias high.
don't fortget every build is different and its based of personal preferences not absolut truth, one likes sport cars the other limousines
.Attachments
Here is my build of the HA.
Del V across R13 and R13’ is 1740mV and on one ch and 1730mV on other after 2 hours. So hefty bias.
I mounted the IRFP on separately thro wires and that’s why all the wiring.
Heat sink is a bit small for this dissipation and gets hot.
Offset jumps around a bit from -3mV to +6 to 7 mV.
Listened on my sennheiser 25ohm HPs (don’t have a model name/specs as they are quite old, 2009). HPA Sounds good and true but bass is a tad bit less.
No hum/hiss of any kind, PCB designer is a brilliant guy.
Used a 21 step MFR 10k volume pot, no issues there.
Next on build list is the ESP HPA.
The case is supposed to be a universal HPA cabinet and will probably see a lot different HPA’s and small amps.
The nazar PSU doesnt use shunt components, so its a plain LM317/337.
Del V across R13 and R13’ is 1740mV and on one ch and 1730mV on other after 2 hours. So hefty bias.
I mounted the IRFP on separately thro wires and that’s why all the wiring.
Heat sink is a bit small for this dissipation and gets hot.
Offset jumps around a bit from -3mV to +6 to 7 mV.
Listened on my sennheiser 25ohm HPs (don’t have a model name/specs as they are quite old, 2009). HPA Sounds good and true but bass is a tad bit less.
No hum/hiss of any kind, PCB designer is a brilliant guy
.Used a 21 step MFR 10k volume pot, no issues there.
Next on build list is the ESP HPA.
The case is supposed to be a universal HPA cabinet and will probably see a lot different HPA’s and small amps.
The nazar PSU doesnt use shunt components, so its a plain LM317/337.
Attachments
Well rumina and other GB subscribers,
I have tried to listen to this amp on various materials and sources, and I too conclude that the bass is not sufficient despite building it to designer's suggested specs (if you can boost bass frequencies, it sounds very good). Lot of money invested in case and components (nichicon gold caps and 20-30 transistors of each type for matching purpose). I am going to change my build to ESP's P113 , lets see if it sounds better (neutral)....this was my first HPA (honestly), and more to come, including XRK's HPA with listening review on status OB-1 HP's ..
sincerely,
Prasi
I have tried to listen to this amp on various materials and sources, and I too conclude that the bass is not sufficient despite building it to designer's suggested specs (if you can boost bass frequencies, it sounds very good). Lot of money invested in case and components (nichicon gold caps and 20-30 transistors of each type for matching purpose). I am going to change my build to ESP's P113 , lets see if it sounds better (neutral)....this was my first HPA (honestly), and more to come, including XRK's HPA with listening review on status OB-1 HP's ..
sincerely,
Prasi
hi prasi
to be honest i wasn't to impressed of the sound, bass amount get's better after i pumped the bias up to 240 ma (but no real deepbass). then it's ok for the th-900, tamed the overpowered bass of the th-900 a bit. the amp is similar to the amb m3, a good and quite neutral sounding amp but a bit lifeless in my opinion - but - better then a lot of commercial avaible smaler amps.
but it's not in the league of a dnalo or dynahi which are my favorite headphone amps at the moment. i finished the dynahi last week and it pumps the power up of the dynalo to new levels. if you want a great neutral and dynamic headphone amp with a lot control and bass try the dynalo, when it should sound a bit more relaxed the ksa5 is superb.
and if you want a monster try the dynahi ;-), you find my little monster here rumina - Albums | Head-Fi.org and the other desings.
ps isn't your bias to much for this psu/transformer? have you measured the power consumption from the power outlet? maybe the amp sound also bad because your psu/transformer is overloaded.
to be honest i wasn't to impressed of the sound, bass amount get's better after i pumped the bias up to 240 ma (but no real deepbass). then it's ok for the th-900, tamed the overpowered bass of the th-900 a bit. the amp is similar to the amb m3, a good and quite neutral sounding amp but a bit lifeless in my opinion - but - better then a lot of commercial avaible smaler amps.
but it's not in the league of a dnalo or dynahi which are my favorite headphone amps at the moment. i finished the dynahi last week and it pumps the power up of the dynalo to new levels. if you want a great neutral and dynamic headphone amp with a lot control and bass try the dynalo, when it should sound a bit more relaxed the ksa5 is superb.
and if you want a monster try the dynahi ;-), you find my little monster here rumina - Albums | Head-Fi.org and the other desings.
ps isn't your bias to much for this psu/transformer? have you measured the power consumption from the power outlet? maybe the amp sound also bad because your psu/transformer is overloaded.
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I found my PCBs! Thanks for sending me these a few years back, Prasi! They got lost in my heap but coming out for a quick build, hopefully. All easy to source non unobtanium stuff.
Perhaps a little tweaking in LTSpice and they can even be made into a 5W speaker amp?
@rumina
I have had a dynalo head to head blind ABX comparison once in my lab and it lost badly to one of my SE Class A amps in terms of preference by 3 different listeners. I think it’s hard to generalize that the dyna-X are superior to other amps.
Perhaps a little tweaking in LTSpice and they can even be made into a 5W speaker amp?
@rumina
I have had a dynalo head to head blind ABX comparison once in my lab and it lost badly to one of my SE Class A amps in terms of preference by 3 different listeners. I think it’s hard to generalize that the dyna-X are superior to other amps.
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