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Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
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Old 30th November 2019, 04:13 PM   #911
Seegs108 is offline Seegs108  United States
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Quote:
Originally Posted by poseidonsvoice View Post
He means a speaker with higher sensitivity than the Monitor Audio speakers you have. And the specifications listed on their website is usually optimistic, so I usually insist on an independent measurement.

Unless your room is small and you sit close, you might not get the “jump factor” that can be heard with small class A amplifiers and higher sensitivity speakers (say 93dB/2.83V/1m or more).

As most of us know here, it’s not in the retail cost of the product in high end audio, it’s in the implementation.

Best,
Anand.
I listen mostly in the near field, as I use these PL100 II's and VFET amp as part of my desktop PC audio system. This VFET amp is more than enough for this type of setup, despite the relatively low 88db spec'ed rating (probably less in real life). I was asking about the XA30.8 because I wanted to know more about the sonic quality differences more than anything else. How do these amps differ in the character of sound they each produce. From his previous comments, he indicated the XA30.8 may be a bit more clinical but more dynamic.

Last edited by Seegs108; 30th November 2019 at 04:19 PM.
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Old 30th November 2019, 04:19 PM   #912
nicoch58 is offline nicoch58  Europe
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Quote:
Originally Posted by Seegs108 View Post
From his previous comments, he indicated the XA30.8 may be a bit more clinical and dynamic.
6moons audioreviews: Pass Labs XA30.8
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Old 30th November 2019, 05:22 PM   #913
Rush is offline Rush  United States
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Quote:
Originally Posted by Seegs108 View Post
I listen mostly in the near field, as I use these PL100 II's and VFET amp as part of my desktop PC audio system. This VFET amp is more than enough for this type of setup, despite the relatively low 88db spec'ed rating (probably less in real life). I was asking about the XA30.8 because I wanted to know more about the sonic quality differences more than anything else. How do these amps differ in the character of sound they each produce. From his previous comments, he indicated the XA30.8 may be a bit more clinical but more dynamic.
Implementation also plays into the character of a DIY amp.
So hard to say. How large (VA) is your transformer, how much capacitance in the power supply, did you follow the best wiring techniques and use high quality wire, etc...?
The sound of any DIY amp, even though using recommended components, can sound much different. And I don't know what yours sound like or anyone else's for that matter, I just know what mine sounds like.

But for sure the 30.8 is implemented correctly and can be compared to other mass produced amps.

I would say, if you can afford a Pass 30.8, buy it. You won't be disappointed. (I think Reno has a money back return policy.)

Rush
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Old 30th November 2019, 05:50 PM   #914
Zen Mod is online now Zen Mod  Serbia
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Sony Vfet Illustrated build guide
sensitivity , not efficiency

bigger speakers , preferably old school ( no high power , so no heavy moving mass) are generally more dynamic sounding than smaller ones

rough thumb , so rule also rough ...... but that's why I prefer old school (made) drivers to modern FiFi ones
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Old 30th November 2019, 07:37 PM   #915
cjfrbw is offline cjfrbw  United States
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VFET tends to emphasize absolute separation with a brief, sweet, deep but natural tone. I have never heard that tone exactly from other solid state devices of any sophistication. VFET tends to be cleaner than tubes without losing the tone. A directly heated triode OTL type tube amp comes to mind.

I have heard Pass 30.8 a couple of times at shows and it sounds very good, but I like the XA25 better. I still don't think they have that last essence delivered by VFET.

However, sometimes I think I like the M2 better than DIY VFET when the First Watt M2 is warmed up for a long time.

I hate to say that as a long time VFET/SIT fan, but the VFET is more like the TV displays on the showroom floor in torch mode: blue emphasis, with contrast and detail dialed up to catch the eye. It is more 'audiophile' in that regard.

The M2 is more like a display calibrated for long term use with a slight organic impressionism and warmer hues. M2 is wholistic with bursts of energy, and after a couple hours of warm up, a compelling sheen to the upper midrange.

It's hard to say because they are all good, and whether you would prefer one or the other could just depend on mood and auxiliary equipment.
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Old 1st December 2019, 08:47 AM   #916
bajjisw is offline bajjisw  United States
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Default Output offset or ?

Hi everyone,



ACP+ from BA2019 gave me the extra push to try and finish this.


Dennis and Ben (ACP+ benchmates), 6L6, ZenMod, Tom, Variac, chefhat, big papa and everyone else - it is awesome to put faces to names. Thanks for making BA happen.




I followed the bias procedure for Part 3. I put in the VFETs for one channel. In Part 4, The output offset is ~10mV . The voltage across R32 is ~ 120mV.



Which of the two requirements are more critical? Should I try to get the R32 = 100mV or is the zero output offset more important? Should I stop here and proceed to the next channel ?



thanks
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Old 1st December 2019, 09:09 AM   #917
Rodeodave is offline Rodeodave  Austria
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Sony Vfet Illustrated build guide
I would move on to the next channel. The final tweaking must be done with both channels operating and with a closed lid after ample warmup time. The additional heat from the second channel would negate any fine-tuning to the first channel that you'd be doing now. It takes some iterations.
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Old 1st December 2019, 09:11 AM   #918
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generally,offset up to 100mV (any polarity) is OK, but let's say that 50mV is even better/normal when speaking of smaller amps

R32 reading correspondence with Iq , try to lower it to prescribed 100mV , thus increasing expected life of parts/amp

I can bet that , with some time invested, you can get both reading close to intended

edit: agree completely with what Rodeodave posted in a meantime , while I was typing
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Old 1st December 2019, 10:52 AM   #919
bajjisw is offline bajjisw  United States
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Onwards then. Thanks a lot for the quick replies.
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Old 4th December 2019, 01:16 PM   #920
bajjisw is offline bajjisw  United States
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Default No sound yet and afraid .....

The amp ran for a few hours with output offsets close to 20mV. All test voltages were close at the time.

However, when I plugged in a source and speakers, no sound.

Now for both channels, the V- LED is out, V- is close to 3V and the output offsets for both channels is around 7.5V

I hope the magic smoke is not out of the VFETs. It would be funny if it were not tragic - I was explaining what the magic smoke was to my family yesterday since I was wearing the BA2019 tshirt.

Any thoughts on how to proceed?

Thanks
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