PASS DIY F4 beaten hands down by my class D amp, what's wrong?

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generg

generg

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Joined 2009
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I can understand that you are disappointed......

I think F5 has more of the aspects you like when hearing your class D amp, what is it's name?
I liked more F4 coming from Accuphase, that sound was very detailed and precise.
I liked the less revealing and more coherent sweeter sound I heard with F4 and I even left therefore F5.
Before selling the Accuphase I made a long hearing session, but there was no way back for me. As I pre I preferred slightly pumpkin over the BA-1 front you used.
Another problem maybe really your speakers low efficiency, the First Watt line is not intended for 4 Ohm and low efficiency speakers.
Would be interesting to hear a commercial product of Nelson, with sufficient power in comparison to your class D amp.

I changed from an 4 Ohm Thiel wit 87 db to an open baffle with Lowther and Tone Tubby.
All First watt amps sound now much more dynamic and detailed, I did it to have security in building further FW amps, that are intentionally low watt not to be concurrent to Nelsons commercial products.

And to be honest If I had to choose between a perfect commercial amp and less perfect FW amps I would decide nevertheless for the last possibility because I want to build amps and learn something and have communication here......
 
buzzforb

buzzforb

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Joined 2010
mr_push_pull said:
I have decided to build/buy the F4 as my first venture into class A, being not completely satisfied by the class D/Dynaudio match. even the advocates of class D admit that the class A should be better but instead of having a revelation I was turned off. I've listened to other (commercial) class A amps in the past and even in comparison to my class D and the general feeling was that the A class has a thicker, more solid sound, while keeping the detail of the D. but not with the F4.

if you're willing to accept that this is not meant to be a class A bashing thread I'll go into more detail and describe the implementation.
Click to expand...

Please share your thoughts. It might help us determine what is going on. Most likely scenario from other opinions is inadequate power. You have 86dB speakers and further lossses from XO.
 
P

pdul

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Joined 2009
There might be nothing wrong at all. I have been using a Denon and a Nad poweramp for years. very happy, good sound, but after I tried a class D, I could not go back anymore. I quickly became an addict of the analytic sound from the class D. All three amps 200w+:)
 
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ra7

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From your description of a crappy soundstage, it looks like there is something wrong with the F4. At the level of the firstwatt designs, there are only small margins for improvement in sound. It will do all the basics right and some more. What it has to come down to is taste. But if you say the soundstage is crappy, there appears to be something wrong with the amp itself.
 
B

BTW

Member
Joined 2002
Sounds to me like your DIY F4 amplifer's wired out of phase... Just switch the + and - of your speakers terminals and take another listen to it...



mr_push_pull said:
it is not the kind of difference that is just a matter of preference, it simply sounds worse and makes me want to shut it off and connect the class D. others have confirmed it without any prior bias from my side. I can't really describe it, but if I try by comparison the sound of the class D could be described as clean and displaying a lot of texture with everything, chords, voices, brass etc. with the F4 that is simply gone and makes me feel like listening to mp3's instead of CD's. the imaging is not precise, the sound sounds like a poor replica of the one coming out of the class D amp.
Click to expand...
 
moe29

moe29

Member
Joined 2002
The F4 isn't a piece of audio gear you plug into your current system and pass judgement on.

It's one piece in the overall sound chain. A chain that has to be purposed built to get good sound.

I think you're missing the whole point of the FirstWatt raison d'être.

You need to start from the beginning... the very beginning! Say the Zen Amp!!

I think Mr. Pass knows what he's doing. But he's not going to do it for you

---Well he can... it's called Pass Labs gear! :) Lots of combinations that will run any speaker. plug and play, with no praying!
 
A

Andy5112405

Banned
Joined 2006
ra7 said:
From your description of a crappy soundstage, it looks like there is something wrong with the F4. At the level of the firstwatt designs, there are only small margins for improvement in sound. It will do all the basics right and some more. What it has to come down to is taste. But if you say the soundstage is crappy, there appears to be something wrong with the amp itself.
Click to expand...

Could it be a simple matter of phase? If one channel is out of phase then the soundstage will be non-existent.
 
W

wirewiggler

Member
Joined 2005
You really have not provided enough info to make any kind of diagnosis. The F4 is capable of resolving detail and soundstage (I have a balanced DIY set). A picture of the amp may be helpful to determine if adequate power supply ect. An audio system is a sum of its components as well, some are better suited for each other knowing the rest of the chain would be helpful. Being a power buffer it requires the extra gain of the BA front to work in your system, it is not being implemented as it was designed (preamp with large voltage swing). it would have not been my first choice with those speakers while it will operate into 4 ohms they simply need more power for dynamics. Even with reasonably efficient speakers I run a balanced set to get suitable output to drive the speakers ( I do enjoy loud rock on accessions). Some testing would be required to determine if the amp was indeed operating correctly or if it is implementation or just personal taste. If you lived close to someone who had one working satisfactorily and was able to audition it that would be helpful as well.

Bill
 
Nelson Pass

Nelson Pass

The one and only
Joined 2001
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Setting aside the possibilities that the implementation is faulty or that the
listener simply prefers the sound of the Class D amp, you should remember
that the F4 has no voltage gain. Whatever is driving it is having to operate
at probably 10 times the output voltage.

Perhaps you should listen to the Class D amp with an input attenuator
dividing the signal down by whatever the gain figure of the Class D amp
is and see what happens to the sound.

:cool:
 
M

mr_push_pull

Member
Joined 2004
Hi Nelson,

I feel that I need to emphasize again that I don't by any means intend to bash your product but rather track down the issue. I'm confident that at the level of sound degradation I'm experiencing it really is an implementation fault.
I'll come back tomorrow with pics and detailed description of the implementation, momentarily I'm unable to remove the lid so I can take pics and look at details as transformer rating, filtering etc.
 
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