The 64 million dollar question!. I am betting on fx8.
Hi Guys,
I finally got a chance to hook up both amps. Each are running on their own PSU consisting of a 30-0-30vac 160VA transformer and a bank of 6-4700uF caps. The variac is turned down so they are providing +-36vdc to each amp. They are hooked up to my A/B setup which uses two, 15k DACT Type 21 Stepped Attenuator Potentiometers for independent volume adjustment, a speaker switch and being fed by a Technics CD player. I played some Larry Carlton, Ella, Techno and blues through them. I know you guys were hoping for a clear winner, but both of them are so true I just can't find a difference between them. I say take your pick. You will be more than pleased with either.
A couple of things to take into consideration. The FX8 has fewer parts but the outputs are more expensive so I think the cost ia about the same. The AX10 runs cooler unless you push both of them and then they seem to run about the same temperature.
Sorry I couldn't be more help.
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Did someone had the chance to compare these two amplifier (topology) next to each other
Terry maybe you?
I'm a fan of a symmetrical CF amps (that not mean they are better)
Greetings
No need to apologize...you were more than helpful with your comparison.
Terry, do you ever use some type of line stage before your amps or just the DACT attenuator?
Also, can you please post your Sprint file for the AX8?
Thanks...
Well, as suspected, they are both perfect. Beautiful!
The differences that I see.
FX9 needs to warm up for the offset to settle to +-2vdc. For the first minute or so it runs about 45mV. Once it warms up the servo will hold it very close to zero volts.
FX8 holds right around 10mV offstet or less.
The FX9 has a little higher gain. I have to run the volume control higher on the FX8 to make them equal. Once they are equalized there is no noticeable change when switching from amp to amp.
I already displayed the square waves of each amp earlier in the thread.
Blessings, Terry
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I used to have a B1 Mezmerize in front of the attenuators but a few guys thought it may be affecting the results so I bypassed it. The goal of the A/B setup is to compare amps so really the attenuators are all that is needed to equalize the outputs. I have built a few different line stages as well as preamps. Some of them "change" the sound of the music. Some add gain some don't. I like the little line stage that Mile posted earlier. I may add those to some of the amps once I get around to building some cases.
I'm attaching my sprint file for the FX8 you see in the pictures. It is basically a clone of Prasi's layout. Sonal uploaded his sprint file for the smaller layout he designed.
Blessings, Terry
You did great!. Thanks a lot for your tests and sharing your impression. May be I will build FX10 too. and yes APEX wins!!reg
Prasi
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Which line stage is this?
I have your FX8 Sprint file that you posted several pages back. I thought you might have a Sprint file for the AX8 that you built.
Thanks...
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-617.html#post4604825
Hi,
What are the component values for a 25-0-25 v (dc) power supply? Would appreciate information on how to compute these values for a different power supply voltage.
This query is for the Apex FX-8 circuit specified for 35-0-35 v (dc).
Thanks
I value your subjective evaluation more than your trying to be politically correct evaluation. I have mentioned elsewhere that almost all people are not trained to pass a controlled ABX well.
In real life situation, we may encounter clipping, very fast music transient, RF interference, etc (and access to sub-conscious mind). All these contribute to subjective feeling during long enough listening period.
Apex has mentioned that F8 was his new favorite amp (coming from him it is a must for me to build the amp). You have mentioned that you think you prefer F8 to VSSA. And you have mentioned that the bass of F8 is "to die for" and you have more than necessary mentioned that the mid and high is "very sweet"...
This is normal for such topology to have better bass than VSSA. Also the LTP tend to have more H2 dominance than symmetrical CFA. What matters imho is this subjective evaluation.
Just saying.
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An update.
Because the AX10 worked so well without a trimmer I wanted to try the FX8 with just the diode per the schematic. With just the diode in place of the trimmer I see 26mA on the rail. However, there is still no sign of crossover distortion and the sound is still very good. The amp will certainly work as designed if one chooses to not use a trimmer.
Because the AX10 worked so well without a trimmer I wanted to try the FX8 with just the diode per the schematic. With just the diode in place of the trimmer I see 26mA on the rail. However, there is still no sign of crossover distortion and the sound is still very good. The amp will certainly work as designed if one chooses to not use a trimmer.