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Valve Itch phono
Valve Itch phono
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Old 31st March 2020, 11:58 AM   #3381
merlin el mago is offline merlin el mago  Europe
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What's the best SQ?
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Old 31st March 2020, 03:34 PM   #3382
zz1969 is offline zz1969  Russian Federation
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The power supply in the latest version is much simpler to save the space (CLC). I believe this resulted in a bit muddier bass. In the first version it was cLCLC. But the difference is very subtle I would say. Maybe as Salas said there were/are some parasitic capacitances.
I haven't done any testing yet btw.
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Old 31st March 2020, 06:20 PM   #3383
Salas is offline Salas  Greece
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Valve Itch phono
There is always parasitic capacitance in layout styles but I wonder how different between each p2p build and the specific board.

It maybe changes the input capacitance or second stage's Miller effect a bit. If there is measurable difference in the response between p2p and board builds it can be adjusted by tweaking C3 value.

But that is in the same area of how much treble preference also. Other changes between builds like in the PSU configuration may bring differences of course.
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Old 4th April 2020, 01:23 AM   #3384
jphabc54 is online now jphabc54  United States
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Finally did some side by side with my Graham Slee Reflex M. First of all, I was shocked that the Valve Itch is significantly quieter. I had always thought the Slee a bit “thin” in my system and the test bore this out. The Valve Itch is incredibly accurate but just extracts a richness of detail that the Slee doesn’t. I’m listening to the new MoFi one step of Mingus Ah Um, which is a remarkably layered, complex recording. On Better Got It in Your Soul there is a presence with the Valve Itch — air between the horns in collective improvisation, the cymbals crackling with tremendous accuracy, and Charles Mingus himself shouting in my room. These details were there with the Slee, but with less lifelike presence. Then on the somber ballad, Goodbye Pork Pie Hat, the gooey midrange comes out, but the air and space remains.

Anyway, just some listening notes. I am really enjoying this thing.

Rest of system:

Hana SH > Rega P8 > Valve Itch > Rogue Cronus Magnum II > Harbeth 30.1
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Old Today, 07:10 AM   #3385
vgeorge is offline vgeorge  Greece
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Valve Itch phono
Took me some time, but finished assembly my itch too. Only power supply has a box for the moment and have to find a nice one for the main amp in the future.
I attach also some measurements I took, a zoomed RIAA response and an FFT.
THD+N drops about tenfold if you up the output voltage to one volt.
Also at the end I had to shield the small tubes and C4 capacitor for a cleaner FFT. Some spikes at the top will be dealt with when in a proper box.
Hopefully will have a listen with a shure V5 type III with a generic needle (no Jico for the moment!) the next few days.
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Old Today, 07:35 AM   #3386
Salas is offline Salas  Greece
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Very good noise floor and excellent RIAA tolerance for measuring an open plan tube phono build George. Congratulations.

Your little HF spikes to the right of your yellow FFT chart should be bench interference picked by either input valves or most likely by the inter-stage capacitors. Boxing and/or close shielding may eradicate them. Hum related needles at the lows are already almost absent. Excellent result in that commonly troublesome area. Jphabc54's remarks on surprising quietness and response accuracy to the ear you backed them up with some measurements now.

Do you have an up close 0dBV (1VRMS) 1kHz FFT so we could maybe discern the real THD spikes coming up from the noise floor?
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Old Today, 07:44 AM   #3387
Salas is offline Salas  Greece
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By the way, in case you did, don't use the anti-Riaa software filter for evaluating response when doing the 1kHz THD FFT.
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Old Today, 07:57 AM   #3388
vgeorge is offline vgeorge  Greece
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Quote:
Originally Posted by Salas View Post
Very good noise floor and excellent RIAA tolerance for measuring an open plan tube phono build George. Congratulations.

Your little HF spikes to the right of your yellow FFT chart should be bench interference picked by either input valves or most likely by the inter-stage capacitors. Boxing and/or close shielding may eradicate them. Hum related needles at the lows are already almost absent. Excellent result in that commonly troublesome area. Jphabc54's remarks on surprising quietness and response accuracy to the ear you backed them up with some measurements now.

Do you have an up close 0dBV (1VRMS) 1kHz FFT so we could maybe discern the real THD spikes coming up from the noise floor?
I did one with 1vrms, but did not record it. Maybe later.
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Old Today, 07:58 AM   #3389
vgeorge is offline vgeorge  Greece
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Quote:
Originally Posted by Salas View Post
By the way, in case you did, don't use the anti-Riaa software filter for evaluating response when doing the 1kHz THD FFT.
Thanks for the tip and the support so far!
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Old Today, 08:16 AM   #3390
Salas is offline Salas  Greece
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Because such a software filter in order to evaluate response against an EQ standard (Riaa) shows the phono noise flat on the display without being there as such in reality. The mid & lows grass should be getting gradually higher than the highs grass, roughly following the Riaa curve as noise floor when measured untouched by software EQ.
Its not working like a hardware anti-Riaa that prefilters the test signal to the phono's opposite way. It simply plots the phono's internal Riaa deviations vs a mathematically perfect phono EQ filter. Your test source signal is still flat.
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