Valve Itch phono

[merlin el mago]

Could be good to know a proper anti RIAA schematic for Valve Itch.

 

[neskor]

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

 

[merlin el mago]

Where did you bought the EQ LCR units?

 

[neskor]

Where did you bought the EQ LCR units?

got them 10 years ago from local audio builder "Solaja Audio"

 

[Salas]

Could be good to know a proper anti RIAA schematic for Valve Itch.

Bonsai explains well and has circuit: An Accurate Inverse RIAA Network

 

[Salas]

Just need to invest in some mu metal case

Absolutely. Hum can be its Achilles' heel.

 

[vgeorge]

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

 

[Salas]

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.

 

[Salas]

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.

 

[merlin el mago]

It's this one?

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

 

[Salas]

It's this one?

No, this: http://hifisonix.com/wordpress/wp-content/uploads/2016/12/Accurate-Inverse-RIAA.pdf

Ask Bonsai the man himself how to get if he makes any, he is a very well known member here.

 

[Salas]

yes, it was the same power supply

Also coupling capacitors were same types between your RC Riaa and LCR Riaa phonos?

 

[merlin el mago]

OK thank you.

 

[Salas]

You are welcome. All guys be careful as much as possible, soldering and listening is home staying friendly activity and a kind of a stress relief, stay safe in these strange days.

 

[jphabc54]

You are welcome. All guys be careful as much as possible, soldering and listening is home staying friendly activity and a kind of a stress relief, stay safe in these strange days.

Couldn't agree more. Stay safe everyone.

On the inverse RIAA, I built the -40db of Hagerman's circuit here using spare parts on hand.

http://www.hagtech.com/pdf/iriaa2.pdf

 

[Salas]

That one has an extra 3.18uS (50kHz) time constant indeed.

If accurately made it can work for valid up to 3kHz square wave testing of the Itch for tweaking C3. That Anti-RIAA could be having some intrinsic droop beyond 15kHz. Keep it in mind when checking for flat response in combination with the Itch.
You could first try document your anti-RIAA build's curve alone against the published RIAA standard. So to know on what deviation basis from flat to judge when a phono is combined.

 

[merlin el mago]

You are welcome. All guys be careful as much as possible, soldering and listening is home staying friendly activity and a kind of a stress relief, stay safe in these strange days.

Here confined 15 days & Spanish Government prolongued for 15 days more so till 11/04/2020 but I guess will be more days of confinement at home.

 

[zz1969]

Transferred p2p to a board today. Maybe I will switch to a classic 2-box setup with better components after a while. But now let's listen to some more music.

 

[Salas]

Performing the same tonality as previously P2P? Because construction style parasitic pF maybe different.

 

[zz1969]

You are right, Salas. The sound is a bit different. I am not sure I can describe it. It is the same but it is different at the same time. Maybe it is just psychosomatics.