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Valve Itch phono
Valve Itch phono
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Old 26th March 2020, 07:11 PM   #3361
merlin el mago is offline merlin el mago  Europe
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Could be good to know a proper anti RIAA schematic for Valve Itch.
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Old 26th March 2020, 07:15 PM   #3362
neskor is offline neskor  Serbia
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Originally Posted by merlin el mago View Post
I'm interested in the DIY LCR units about SQ & price, could you let me know more information?
Here is my DIY LCR attempt
Sounds good to me
Total cost around 70 EUR for the pair
Just need to invest in some mu metal case
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Old 26th March 2020, 07:17 PM   #3363
merlin el mago is offline merlin el mago  Europe
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Where did you bought the EQ LCR units?
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Old 26th March 2020, 07:19 PM   #3364
neskor is offline neskor  Serbia
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Originally Posted by merlin el mago View Post
Where did you bought the EQ LCR units?
got them 10 years ago from local audio builder "Solaja Audio"
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Old 26th March 2020, 07:21 PM   #3365
Salas is offline Salas  Greece
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Valve Itch phono
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Originally Posted by merlin el mago View Post
Could be good to know a proper anti RIAA schematic for Valve Itch.
Bonsai explains well and has circuit: An Accurate Inverse RIAA Network
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Old 26th March 2020, 07:24 PM   #3366
Salas is offline Salas  Greece
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Valve Itch phono
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Originally Posted by neskor View Post
Just need to invest in some mu metal case
Absolutely. Hum can be its Achilles' heel.
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Old 26th March 2020, 07:39 PM   #3367
vgeorge is online now vgeorge  Greece
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Valve Itch phono
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Originally Posted by Salas View Post
Another nice one. In black looks good too.

By the way, who has reliable method to check his build's Riaa response* do test it for what is the best treble capacitor value C3 for the board style.
Because it should have different parasitic capacitance than the hardwired prototype. Maybe with different make second stage tubes and bases the parasitic pF can vary a bit also.

*(either accurate anti Riaa, preferably without "lost constant", or digital anti curve FR filter)
I will use my Quantasylum Q-401 and will do some tests when I finish assembly.
Also got some optimized anti RIAA numbers from you
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Old 26th March 2020, 07:39 PM   #3368
Salas is offline Salas  Greece
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Valve Itch phono
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Originally Posted by jphabc54 View Post
Finally getting around to writing up my latest build of the Valve Itch. I was having issues with the valve sockets on the original (heater contact on V4 was touchy), so I ended up using my last PCB and starting from scratch using premium components.

Scratched together a Hagerman inverse RIAA, and ran 1K through the scope -- very nice channel match and gain is right as expected.

Not sure I could imagine a component being more transparent. This thing WILL convey what's on the recording (good, bad, and ugly). When it's a fine recording, it absolutely sings. When it's not, well..you'll hear it. When I get time I'll compare it to my previous solid state reference (Graham Slee Reflex M). The only area where I'm not 100% it's performing where it should be is in the bass. It sounds lighter than I think it should be with some recordings, but that may just be expectation bias. I unfortunately don't get too much time to listen critically.

Notable components include (everything matched within 1%):
C2 FT-3
C3 SSG Silver Mica
C4 FT-3
C6 Mundorf M-Cap Supreme

R1 Texas Components S2575
R2-R4; R7; R12 Takman REY
R5 Vishay S102K
R6; R8 Shinkoh .5w
R9-R11 Mills 5w
R13 Audio Note 1w

Anyone else thinking of building one?
Very very nice.

One last thing. You wouldn't be able to correctly see about 10kHz square waves for the Itch when your anti-Riaa has the "lost" constant implemented. Because the Itch does not use that "mythical" 3.18uS constant. On the other hand, a legacy anti-Riaa network will do fine.
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Old 26th March 2020, 07:47 PM   #3369
Salas is offline Salas  Greece
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Valve Itch phono
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Originally Posted by vgeorge View Post
I will use my Quantasylum Q-401 and will do some tests when I finish assembly.
Also got some optimized anti RIAA numbers from you
Hardware anti-Riaa difficult to make absolute. Software one easy. FR can be well tested.

Still, hardware anti-Riaa has one advantage. Allows checking say 1-5kHz square wave with gen & scope to can tell about possible ringing and the LF to HF transient balance too.
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Old 26th March 2020, 07:48 PM   #3370
merlin el mago is offline merlin el mago  Europe
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It's this one?

hifisonix accurate RIAA EQ amplifier board + PSU PCB 1 set ! - JIMS Audio
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