Noisy eTap2hw

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Re: Noisy eTap2hw

Postby GuitarPhil » Thu Nov 29, 2012 7:21 pm

Thanks for checking your op-amps Dick. I'm about to do my swap test 8-)
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Re: Noisy eTap2hw

Postby Echotapper » Thu Nov 29, 2012 7:40 pm

Forwarded difference to Newtone. My part list is leading. :o

I need to also explain the signal/noise in more detail. I've measured -70dB and regard this as the standard in my design. In literature on tape devices from the 1957-1964 era I have in my archive here the HIFI tape signal/noise standard was to be >55dB.

A nice anecdote in the early phase of the project was my urge to inject weighted white noise into the return path ( yes, no signal would be no noise) this was achieved by a mechanism adding noise at each signal detected in the feedback loop. It did the job nicely but the early adaptors 'kindly' requested to take it out! So, your unit should be around -70dB Signal/Noise.


Piet
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Re: Noisy eTap2hw

Postby GuitarPhil » Thu Nov 29, 2012 8:47 pm

Piet,

I think the op-amps may be 'not guilty'. I swapped IC1 and IC2 with two from another kit (also the P types) and the noise is still present. I also used Dick's idea to trace the source by using my amp (actually my interface/headphones nd the first point I detect any hiss is at the drain of the FETs (both are similar). The hiss level at the pre amp outputs is louder (obviously as they amplify the incoming noise) so it looks like the Fetzervalve circuit is behaving like a real valve, it's hissing nicely ;)

Without the ability to measure it, I can't tell if my signal/noise ratio is worse than -70dB. Interesting anecdote about the noise you were going to synthesise :D

I am going to leave the circuit as it is now until we test it through the AC30 at our Shadows Club meeting next Sunday. We'll see what the veterans think - I'm just a relative noob as far as authentic sounding vintage units are concerned :mrgreen:

Incidentally, Piet, I love the tone the eTap2hw input circuit gives my guitar (Fender 59/62 pickups) so I may just end up enjoying the 'authentic' hiss as well ;)
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Re: Noisy eTap2hw

Postby GuitarPhil » Thu Dec 06, 2012 2:50 pm

Well I have tried out my eTap2hw through an AC30 at our Shadows Club meeting last Sunday and apparently I am complaining about noise that the old hands scoffed at! Certainly in the live band situation it's really not noticeable and the AC30's own noise and hum etc does a good job of masking it :D

As a relative noob I didn't know what to expect but I am assured that the real vintage echo units were always pretty noisy - oh well, you live and, hopefully, learn :lol:

Phil.
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