Valve Itch phono

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#321
Found something plausible. H1 has mic/line 2kOhm input, H2 has dedicated line 10kOhm input. I would expect around 400 Ohm Zout from the 6SN7 Mu follower upper tier output point that the Itch utilizes. Guess why I missed ''sparkle'' in the H1 recordings, when it was OK on the stacked Quads through Aikido to Fran, and also OK to my PC on H2 last track. Another mystery solved by your trusty Hot For Valves!😀
 
#322
oooh, good work!

Just for others not tuned in.... the earlier recording was using a zoom H1 which I had borrowed from a friend. The second is using a zoom H2. I had intended buying a zoom H1 (for on-camera use with a shock mount) but then very luckily found a H2 2ndhand locally. To say these would be like hens teeth is putting it mildly.

Seems like I lucked out!


Anyway, we could do with some more builders around here. This must be one of the best sounding phonostages around today. An object of desire for anyone with a TT, whether using MM or MC carts.

Fran
 
#324
I would like to make a bid here for the record for the longest time to build an itch. I started in January and have still not got to first switch on. Anyway so far it's going well thanks to Salas and the crew on this thread! I am sure you would all laugh at my current spaghetti wired version which once tested will then be rebuilt inside it's much tidier boxes. I must get some pics posted for the record. Anyway thanks for help so far.
 
#325
Its not easy to get it totally non humming if not certain building techniques have been followed as you saw earlier with Fran's build. Any high gain low level input circuit for that matter, especially HV. But the test build will be good to check if it is connected up right circuit wise, if it biases well, that there is signal, nothing blows etc. Waiting for pics then. Good luck firing it up.
 
#327
Here is the initial hash up, not finished yet so not quite ready for firing up. With some rather long wire runs necessary at this stage I expect I may get a bit of hum....

I have one box ready, need to make second. Might have gone overboard with the box build with old oak floorboards dovetailed for that built like a tank look.
An externally hosted image should be here but it was not working when we last tested it.
 
#328
You will need grounded metal encasing its highly possible. Even partial for the audio board only. For when finishing a totally quiet one that is. After grounding debugging etc. But lets see if it basically works correctly first and foremost.
 
#331
I believe if the cap is simetric (parallel stacked foils like the rectangular Wimas) it does not matter.

If the cap is cilindrical type, probably with an outer foil, you should take that in consideration and find it.... outer foil should be connected to the lowest impedance side of the circuit (gnd or output of the stage)
 
#332
Hi Nick,

After the superb sound of the Puresound P10 phono MM preamp I decided to make your Itch, please let me know if the following schematics are updated:

Schematic
129351d1237317075-valve-itch-phono-valveitch.gif


PSU
147613d1258842614-valve-itch-phono-valveitchpsusm.jpg


Also I need advice where & exact type of valves are the best & cheapest.

Thanks in advance for kind help.

Felipe
 
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