Valve Itch phono

[merlin el mago]

I always trusted in the combo TT & valve pre, is the way I start my love to music 30 years ago.

I'm tempting to refurbish my mono blocks Jadis JA-80, could you help me? I will post in the valves forum.

Now I'm ready to finish my 26# preamp

Attached Valve Itch pic

 

[Salas]

Hmm very clean build, worked on first go... from now on you show how they make an Itch, Fran and Salas you made to Itchers emeritus.

 

[merlin el mago]

It's silent like a tomb, Valve Itch have a very good characteristic: pops & cracks noise coming from vinyl sounds low level.

 

[Salas]

Keep clean notes, now you said dead silent, newer to tubes phono people will be asking, Merin, how you grounded this and how you connected that. Photos from underside they will ask also.

 

[merlin el mago]

I followed Fran's grounding, star ground, ground wire coming from PSU not direct to star ground: between them I use the ground loop breaker. I learned doing other valve phono preamps it's very important twisted wires & for heater & B+ wires don't cross or be near between them, heater wires also must be always near chassis so chassis acts like a shield avoiding noise in the heaters. Heaters regs I used PRP resistors, BG NP & Panasonic FM. Only boutique parts are used in the phono:

Resistor 22K B+ between 6SN7 & 6N2P-EV (Mills+Shinkoh)
Load cartridge resistor 47K (Audionote tantalum)
Resistor R3 47R Takman carbon
Rest of resistor are common cheap carbon

Heater elevator cap 1uf 450V Auricap
Output caps 3.3uF 450V Auricap

Step-up resistor Shinkoh

Ground loop breaker used

An externally hosted image should be here but it was not working when we last tested it.

Attached pic, enjoy.

 

[Salas]

Is the orange/red/brown/black you use from reg to phono good for HV, or is it some general purpose signal cable?

 

[merlin el mago]

It's a 4 x 24 AWG silver plated copper, shielded silver plated all teflon

 

[RCruz]

Splendid... ultra clean build... nice soldering works...

Interestingly I learned a lot from esp gnd loop breaker you use.... Where exactly do you connect arm earth wire in the schematic you posted ?

 

[merlin el mago]

Only to chassis, inside the chassis I have sanded the painting in order that it was doing good contact.

 

[The Space Egg Corp]

Si.

 

[merlin el mago]

Thanks Si.

 

[merlin el mago]

The subchassis is a sandwich aluminium, mumetal/permalloy, stillpoints, connected to star ground.

 

[massimo]

Very nice blue grommets, Felipe

 

[merlin el mago]

Thank you twice massimo, I will use also in the #26 preamp

 

[merlin el mago]

Changed interstage caps 47nF 600VDC MKP to 47nF 1000VDC teflon film & tin foil

 

[The Space Egg Corp]

Arrh !

You make 26 as well Felipe !

I looked at this also...
...good with attenuator between Itch & 26 maybe.

Felipe...You told me a year ago...but I forget...
...You are using 'balanced amps'...yes ?
..I think you built yourself Nelson something ( F? ).

What line-stage do you use/build ?
This is what you listen to 'Itch' with now...before amps/s ?

Si.

Hope that makes sense.

( nice grommets !!! )

 

[RCruz]

Only to chassis, inside the chassis I have sanded the painting in order that it was doing good contact.

Nice... so TT GND is connected only to preamp chassis and NOT to circuit gnd.

The chassis itself connects to the circuit MINUS only throu the GND loop breaker circuit....

 

[merlin el mago]

TT gnd it's only connected to chassis, the gnd coming from separate PSU goes to the ground loop breaker so you have a clean ground star without any ground loop where to connect all grounds, see attached pic.

 

[merlin el mago]

Marked with red black wire to ground loop breaker and from ground loop breaker to star ground

 

[merlin el mago]

Is the orange/red/brown/black you use from reg to phono good for HV, or is it some general purpose signal cable?

I need to change for other more thick?