Hi,
my bigger FH9 is working at +-45 Volt. I have adjusted the bias to 26,4 mV/120 mA. The offset on one channel 20mV, the other channel 25 mV.
The irfp 240/9240 are matched, the KSC1845 too. The driver KSA1381 and KSC3503 i could not match. CDIL and Onsemi/Fairchild KSA1381 get an hFE of 120, the KSC3503 CDIL 150 hFE and Onsemi 70 hFE. Could not find a similar pair.
Is there any way to get a bit lower dc offset ?
The sound is real good. Bass is a little bit deeper. I think because of the 4700 µf per rail instead of 2000 µf.
I took my little FH9 amp with me and presented it to a regular table of the Analog Forum. All members were astonished about the very good sound of the FH9.
I sell 4 pcb at self-cost price immediatly...only had the four pcbs...🙂
Peter
my bigger FH9 is working at +-45 Volt. I have adjusted the bias to 26,4 mV/120 mA. The offset on one channel 20mV, the other channel 25 mV.
The irfp 240/9240 are matched, the KSC1845 too. The driver KSA1381 and KSC3503 i could not match. CDIL and Onsemi/Fairchild KSA1381 get an hFE of 120, the KSC3503 CDIL 150 hFE and Onsemi 70 hFE. Could not find a similar pair.
Is there any way to get a bit lower dc offset ?
The sound is real good. Bass is a little bit deeper. I think because of the 4700 µf per rail instead of 2000 µf.
I took my little FH9 amp with me and presented it to a regular table of the Analog Forum. All members were astonished about the very good sound of the FH9.
I sell 4 pcb at self-cost price immediatly...only had the four pcbs...🙂
Peter
Fine Peter,
yes this amp is really good.
as i read, you have a regular meeting with some hifi fans...thats great!
chris
yes this amp is really good.
as i read, you have a regular meeting with some hifi fans...thats great!
chris
Hi Chris,
most of the analog forum members building valve tube amps or classA amps. I can learn a lot. One event in the the year i like very much is the "Berkamener Hörtest".
If you are interested you can have a look to some pictures https://flickr.com/photos/_hb/albums/72177720311456207/with/53214106539
Have a nice day
Peter
most of the analog forum members building valve tube amps or classA amps. I can learn a lot. One event in the the year i like very much is the "Berkamener Hörtest".
If you are interested you can have a look to some pictures https://flickr.com/photos/_hb/albums/72177720311456207/with/53214106539
Have a nice day
Peter
Hi Peter,
we already orderd all the parts and power-supply for two more APEX FH-9 XRK-MOD amps,
hopefully running soon in MS.
🙂 uli & uli
we already orderd all the parts and power-supply for two more APEX FH-9 XRK-MOD amps,
hopefully running soon in MS.
🙂 uli & uli
Glad there is interest in this amp is picking up again. It’s a fun sounding and powerful amp.
If I may be so bold as to suggest the layout developed by myself and JPS64 - which provides very low impedance current paths and low noise topology also with options for outboard mounted MOSFETs on flying leads. The FH9HVX is well supported and tons of successful builds.
If I may be so bold as to suggest the layout developed by myself and JPS64 - which provides very low impedance current paths and low noise topology also with options for outboard mounted MOSFETs on flying leads. The FH9HVX is well supported and tons of successful builds.
Hi,
MS means Münster, a town in Germany, north rhine westphalia...sorry. The license plate begins with MS. I am living in DO, means Dortmund. In "MS" we meet to hear on different amps and vinylplayers and talk about and we have have some fun....
Peter
MS means Münster, a town in Germany, north rhine westphalia...sorry. The license plate begins with MS. I am living in DO, means Dortmund. In "MS" we meet to hear on different amps and vinylplayers and talk about and we have have some fun....
Peter
The car was my second hobby, but now is ready build, with a little tuning..faster than a starting big plane... 😎
No news about the FH9 in Münster. I decide to write a mail. No new meeting day for a regular table in sight...
Perhaps it takes more time. Other people are slower with their projects...😉
I have time enough and can build a new amp in one week and have done. The Blame ST is ready for test, LJM L20 Mod pcbs are in production. Orderd new 10 µF CCB capacitors for a Apex P30ZF preamp...
In China all slows down in the moment because of their holidays, i think. Shippingtime is much longer as 12 days as usual.
I the last days have heard often with the FH9 Mod amp, the bigger one i build. I like this amp very much and more than the FX8. The FH9 sounds a bit clearer. Not easy to describe...and subjective.
Greets
Peter
No news about the FH9 in Münster. I decide to write a mail. No new meeting day for a regular table in sight...
Perhaps it takes more time. Other people are slower with their projects...😉
I have time enough and can build a new amp in one week and have done. The Blame ST is ready for test, LJM L20 Mod pcbs are in production. Orderd new 10 µF CCB capacitors for a Apex P30ZF preamp...
In China all slows down in the moment because of their holidays, i think. Shippingtime is much longer as 12 days as usual.
I the last days have heard often with the FH9 Mod amp, the bigger one i build. I like this amp very much and more than the FX8. The FH9 sounds a bit clearer. Not easy to describe...and subjective.
Greets
Peter
Hello Forum Members,
I thought I would offer my experience building the FH9HVX using XRK Audio boards.
I built this amp one year ago and absolutely love it. I think it sounds better than any commercial amp I have ever purchased.
I hope at some point to build a compact, lower-power version that I can use with bookshelf speakers. This is in anticipation of moving to an apartment where a low-power version would be more appropriate.
If anyone is considering building this amp, I would encourage them to do so. It's an awesome project. Also, I had great success using the anplifier boards and PSU boards I purchased from XRK Audio. Happy Building!
P.S. Please excuse the "rats nest" wiring, it was my first project.
I thought I would offer my experience building the FH9HVX using XRK Audio boards.
I built this amp one year ago and absolutely love it. I think it sounds better than any commercial amp I have ever purchased.
I hope at some point to build a compact, lower-power version that I can use with bookshelf speakers. This is in anticipation of moving to an apartment where a low-power version would be more appropriate.
If anyone is considering building this amp, I would encourage them to do so. It's an awesome project. Also, I had great success using the anplifier boards and PSU boards I purchased from XRK Audio. Happy Building!
P.S. Please excuse the "rats nest" wiring, it was my first project.
Attachments
Here. I just purchased an audio analyzer and in the near future, hope to characterize the amplifier a little more.
Best,
Anand.
Hi unclemud
nice amp build.
yes this small version PCB is very tight done. fit nearly in every nice small amp case ---> see at Kleinhorn (Peter)😎
your amp:
which board is what? 😉
chris
Hi Peter
BMW M2....omg.
just have an 525XD...family car..(9 years...its has to stay as long as the mechanic shake his head...)🤣
yes i like the FH9XRK. it is a clear and powerful very musical amp. its not doing very sharp edges to couture the instruments and body but the VFETs are smart in bass and open in the high...like it!
FX8 is more fluid
Wow ...Your are really busy. 👍
want to check again FX8 and FH9 with changed bias...lower, because now i have "semi Class A"...740mA...
ACA PSU done.
i am working an AA14, ....Quasi amp ...reading..
next will be mooly´s lat amp...will see
very interesting is M2OPS Whammy...with Patricks OPV bootstrapping!
chris
BMW M2....omg.
just have an 525XD...family car..(9 years...its has to stay as long as the mechanic shake his head...)🤣
yes i like the FH9XRK. it is a clear and powerful very musical amp. its not doing very sharp edges to couture the instruments and body but the VFETs are smart in bass and open in the high...like it!
FX8 is more fluid
Wow ...Your are really busy. 👍
want to check again FX8 and FH9 with changed bias...lower, because now i have "semi Class A"...740mA...
ACA PSU done.
i am working an AA14, ....Quasi amp ...reading..
next will be mooly´s lat amp...will see
very interesting is M2OPS Whammy...with Patricks OPV bootstrapping!
chris
@UncleMud
Your Amp looks fine, ok...the wiring is ok in my opinion. If the amp works fine and the sound is very good, let it remain as it is...
Fine to hear a opinion about the XRK pcbs from a member. I only saw pictures in the past. I need space at home... 🙄
@chermann
I think you are busy too...i have read about your problems with the Apex AA14. I am afraid i cant help....good luck to finish the amp and success to make it working.
why omg? ...its a M2Competition wih a little more power as usual...even more than the CS...but does not fly...🙂
Peter
Your Amp looks fine, ok...the wiring is ok in my opinion. If the amp works fine and the sound is very good, let it remain as it is...
Fine to hear a opinion about the XRK pcbs from a member. I only saw pictures in the past. I need space at home... 🙄
@chermann
I think you are busy too...i have read about your problems with the Apex AA14. I am afraid i cant help....good luck to finish the amp and success to make it working.
why omg? ...its a M2Competition wih a little more power as usual...even more than the CS...but does not fly...🙂
Peter
Attachments
My FH9HVX output stage is biased at 250mA, so about P = [(2*0.25)^2]*8 = 2 watts peak Class A in 8 ohms or 1 watt peak Class A in 4 ohms before transitioning to Class B.
Class A peak for a push pull/complementary output stage is calculated as: [(2*bias in amps)^2]*load impedance.
Reading post #56 by @chermann, did you have the vertical mosfet version of this design (i.e. FH9XXX) biased at 750mA? No issues with thermal runaway? 0.75A bias will give you 18 watts peak Class A/8 ohms or 9 watts peak Class A/4 ohms before transitioning to Class B. Your voltage rails are only +/-31V. How warm were your heatsinks? Your dissipation would be 62V*0.75A = 46.5 watts. I am considering increasing my bias until my heatsinks reach about 50 degrees C. If I do, I might consider adding a cap bank immediately before connecting to the voltage rails on the main board since increased bias current puts a bigger load on the power supply - although I do have a fair amount of capacitance already.
Best,
Anand.
Class A peak for a push pull/complementary output stage is calculated as: [(2*bias in amps)^2]*load impedance.
Reading post #56 by @chermann, did you have the vertical mosfet version of this design (i.e. FH9XXX) biased at 750mA? No issues with thermal runaway? 0.75A bias will give you 18 watts peak Class A/8 ohms or 9 watts peak Class A/4 ohms before transitioning to Class B. Your voltage rails are only +/-31V. How warm were your heatsinks? Your dissipation would be 62V*0.75A = 46.5 watts. I am considering increasing my bias until my heatsinks reach about 50 degrees C. If I do, I might consider adding a cap bank immediately before connecting to the voltage rails on the main board since increased bias current puts a bigger load on the power supply - although I do have a fair amount of capacitance already.
Best,
Anand.
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