Search found 4027 matches

by mediatechnology
Mon Dec 09, 2019 6:23 pm
Forum: The Peabody Lounge
Topic: Gentle persuasion over time
Replies: 75
Views: 1859

Re: Gentle persuasion over time

Beer trub has sugar (malt) in it, and the insects are responding positively.
Beer has that effect.
by mediatechnology
Mon Dec 09, 2019 3:10 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

Let's see what kind of NF we can get with the Jubilee's at 5Ω, 0.34 mV (1kHz 5cm/s) and 62 dB gain. For 62 dB gain Rg=1Ω 5Ω Rsource noise is -145.7 dBu (20kHz BW) The preamp Rnv is 3.5Ω (2X ZTX851) + 1Ω (Rg) = 4.5Ω In the test here I figured the Preamp's Rnv was 5Ω: I did some additional measurement...
by mediatechnology
Mon Dec 09, 2019 12:27 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

Thanks for the info. 0.34 mV and +52 dB gain would look to provide an output of -15 dBu at 1 kHz 5cm/s so with a hypothetical converter overloading at +9 dBu that would be -24 dBFS. With a +15 dBu OL point (4V RMS) it would be -30 dBFS. With a 4V RMS OL at the A/D it looks like you could use +56 or ...
by mediatechnology
Mon Dec 09, 2019 7:49 am
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

Thank you!

If I may ask "what is the output level of the cart and how much gain did you need?"
by mediatechnology
Sat Dec 07, 2019 6:11 pm
Forum: Test, Measurement and Repair
Topic: Focusrite Scarlett 2i2 Gen 3 Performance Measurements
Replies: 4
Views: 91

Re: Focusrite Scarlett 2i2 Gen 3 Performance Measurements

Found the high level THD measurements done at +10 dBu out and +8 dBu in.
Posted the FFTs in the OP.
by mediatechnology
Sat Dec 07, 2019 1:07 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

I did some gain calculations that I will need to confirm by measurement. Assumes -60 dB input pad and medium impedance load at the output. (49.9Ω X2 build-out.) Jumper settings J4, J5, J6, J7 linked = +62 dB gain. Output = +2 dBu J4, J5, J6 linked. (J7 open) = +56 dB gain. Output = -4 dBu J4, J5, J7...
by mediatechnology
Sat Dec 07, 2019 12:57 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

In practice the MM setup has more noise. Not in practicality, but at full volume 60Hz and harmonics dominate from the cartridge. Not so with the MC setup. This is solved. The headshell on the EPA-501H is composite, and the AT-150MLX lower body is not electrically connected to the upper. I used the ...
by mediatechnology
Fri Dec 06, 2019 8:47 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

One recommendation - put the 4K99 resistors in the BOM. I hadn't read the build guide in-depth so I didn't know to order them. Luckily I've a good stash of extra components. I think that's a good idea. I might want to increase the quantity of the ZTX851 as well so there are some extras for matching.
by mediatechnology
Fri Dec 06, 2019 5:37 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

I thought that chassis looked familiar.

I'll double-check my gain numbers on a board here.
The resistors looked right.
by mediatechnology
Fri Dec 06, 2019 3:54 pm
Forum: Build
Topic: Flat Balanced Input Moving Coil Phono Preamp Construction Information
Replies: 39
Views: 2103

Re: Flat Balanced Input Moving Coil Phono Preamp Construction Information

Glad it's quiet and working well for you. Thanks for joining us! That's a nice build. What chassis did you use? I'll need to think about it a little more but you might want to make sure that the jumper shunts aren't shorting to each other. They have windows on one face to retain the pin and when the...