F2 Initial Listening Impressions

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#61
apassgear said:



Bill,

Even though I haven’t tested it myself it seems odd that you have a higher resistor on R4 position than on R5.

As far as I have work on similar Zen circuits R4 has been about half of R5 to have a symmetrical clipping at the output. But this can only be confirmed with an Oscope, and this is the reason to use a pot at R4 position which will enable adjustment for symmetrical clipping. All this will ensure you have maximum output power before clipping occurs.
🙂
Click to expand...

Hi Tony,

Thanks for the feedback, will try the F2 with a pot later on.. However at the moment the sound I'm getting from the Corals are most outstanding.. We tried some rock stuff yesterday like Pink Floyd, Metallica... and it sounded great with lots of drive... :bigeyes:
 
#62
Hi Tony. Been busy lately, but I wanted to follow up on your question about the F2 with Fostex drivers. I've been listening to the Fostex 166E in the Abbey. The Abbeys do sound different with the F2 as compared to the F1. Some things are lost, others are gained. On the plus side is a little more harmonic richness while still keeping the same basic tonal balance. I also find the F2 provides a better soundstage than the F1. On the down side, the pace and rhythm are reduced somewhat. The greatest loss is in the overall dynamics. That said, I do not mean to imply that the F2 sounds bad with the Fostex 166E. Rather, the two produce a very relaxed sound that many people would like. In my experience, Fostex drivers are very interesting because while they are not as transparent or resolving as some of their full range cousins, they always sound musical. So far, for lower resolution speakers, I like the F1. For high resolution speakers, the F2 takes me to were I want to be. So continue your experiments with a F2 design. In addition to the contemporary speakers, there are some vintage high-sensitivity drivers that would mate well with F2.
 
#63
Hi Biosonar

Reading your listening impression with a great interest.
By the way, are you using balanced or unbalaced input for both F1 and 2? Thanks.

I do not remember if you have already mensioned it . . .

Regards
jH
 
#64
jh6you said:
By the way, are you using balanced or unbalaced input for both F1 and 2?
Click to expand...

Hi JH. I use the Bent Audio passive TVC preamp that supplies both balanced and single-ended outputs. I run the F1 balanced. I've now listened to the F1 both ways, and I think it sounds just a bit better balanced. However, other people I've talked with drive it single-ended and like it. Try both. The difference is very small, but my perception thinks balanced a little more transparent. Your perception may be different.

As to the F2, it can only be driven single ended. Its sound reminds me of high quality SETs driven by CCSs. Single-ended amps are usually more linear with horizontal load lines, less influnced by speaker reactance, and sound less "tubey" The F2 shares this toplogy and has wide bandwidth. With the right speaker, I could live with this amp for many years and be happy. But that is my personal peference.
 
#66
Hi Biosonar,
Nice to hear from you in relation to your experience with F2+Fostex which is very explicit and clear. From your explanation it seems that F2 will mate well with most any FR, not that I didn’t believe what Nelson has said about it, but is always interesting to hear comments from someone who is using the amp on a home installation.

I read you have a very good preamp and guess your front end should do justice to the rest of the equipment so what you say I consider it quite a neutral opinion on the amp. The more I read the better I like the F2.

But the real test will be when I can test drive myself this amp. At present I have only been able to design the PCB’s. Its taking so long that first maybe I will make some changes to the original Zen in order to have a taste.

If anyone would like to have the designs of the PCB’s please let me know and will be happy to send the files.🙂 🙂 🙂
 
#74
Can anyone point to the thread where the F2 was back engineered???
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The backengineering isn't an excact F2.
There are minor details that differ from the F2,as NP stated😉
Nonetheless, with the fishing season comming to an end, I am gonna finish these very well layed out boards waiting for the etch
bath🙂 Its the work of Apassgear😎 I just obtained 3 great heatsinks that could produce an "oldstyle" Aleph chassis, and the F2 clone will end up in that particular chassis😎 The sinks were on their way to the scrap container at work! But a friend of mine saw them and knew about my DIY thing. Great!
Here is a pic of the boards, waiting to be etched, thanks Tony 😉

Steen😎
 

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#75
steenoe said:
The backengineering isn't an excact F2.
There are minor details that differ from the F2,as NP stated😉
Click to expand...

They are indeed minor. The biggest of them is that I loaded
the output with 15 ohms to get a slightly higher damping factor,
if you call .5 higher, and my Source resistor was more like 1 ohm.

😎
 
#77
That's correct; originally it was set at 15 ohms as per Nelson tips. But I recall him saying that that was somewhat an arbitrary value since it will depend on the speaker load/characteristics it was used with. This is also related to Nelson's Current Source Amp/Full Range Drivers paper.

So one should experiment with this value for best performance and taste
 
#79
I was referring to the Source resistance of the Gain device,
where the N channel on the bottom is set more around an
ohm, which set the gain to X8 or so with an 8 ohm load.

The higher bias is certainly nice - at 2.7 amps it's higher than
needed, but increases the linearity of the device.
 
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