[rodrigaj]

This is my first Hagtech build. I am getting a low level hum out of both channels. I have read the manual's short paragraph on hum, and have tried moving things around, different interconnects, etc. Is there a logical way to approach this? I need some suggestions. The hum is there at all switch settings. When the Piccolo is turned off, the hum goes away.

thanks in advance for any suggestions.

[hagtech]

Does it hum with nothing connected to the inputs?

jh

[rodrigaj]

Yes. With inputs disconnected it still hums.

[poty]

How do you power your Piccolo? If you unplug the Piccolo from mains - how fast does the hum disappear? Does the amount or "pattern" of the hum depend on the gain or loading settings?

[rodrigaj]

I am powering by battery.

Hum is independent of gain or load setting.

Hum is gone instantaneously when powered off. This occurs after a loud "thump", which I am assuming is normal. I usually mute the system when changing gain settings, on - off, etc.

[poty]

Does Piccolo work (amplifies)?
Could you unplug the input cables and short out the input RCAs? I mean for each RCA connect the center pin to the shell.

[rodrigaj]

The Piccolo works just fine. Each of the gain settings do work. It's just the low level hum that bothers me. It does not interfere with the music, but I kept reading about how quiet the Piccolo is supposed to be and in my system it is not quiet.

I will try grounding each input to see if that eliminates the hum. I will need to do that later today.

[poty]

Battery powered devices do not have the source of hum internally, only from outside. Main question now is whether all is built right?

[rodrigaj]

If I ground the inputs the hum is still there and increases slightly.

Since the source of hum has to be from the outside. Could you suggest where to look on the circuit board? Unfortunately, I don't have any test equipment, but if you could point me in the general direction, I could try a visual inspection. Could you suggest where to look?

The Piccolo works fine, except for this low level hum.

[poty]

One more question before visual inspection: could you explain in details how you managed the ground system? I mean where the turntable ground is connected, Piccolo ground lug, phono-amp, preamp, power amp...

[steve in jersey]

It's just looking a friendly Flute!

[rodrigaj]

The tonearm ground is connected to the piccolo. I did try also connecting it to the phono stage, with a wire to the phono from the piccolo: Tonearm to piccolo - piccolo to phono.

[hagtech]

Try moving it around a bit.  Seems the PICCOLO or the input cables are in the middle of a magnetic field. 

jh

[rodrigaj]

Jh - Yeah, I was beginning to suspect that.

I had ordered a one foot length of cable from Blue Jeans cables, in order to minimize cable runs and I think that I inadvertently positioned the Piccolo in the magnetic field of the phono stage power transformer. It sits to the right of the rear of the phono stage and that is where the transformer sits.

I'll order a longer cable from Blue Jeans and report back.

[poty]

If the tonearm ground is not accidentally connected to the mains at the turntable itself I also agree, that the source is completely outside the Piccolo.
Maybe the contact of the ground connection to the case is not good?

[rodrigaj]

If the tonearm ground is not accidentally connected to the mains at the turntable itself I also agree, that the source is completely outside the Piccolo.
Maybe the contact of the ground connection to the case is not good?

Poty -

I don't think that that is possible with my turntable: VPI HW19MKIV w/SAMA motor. Tonearm: Moerch DP8. The tonearm is totally independent of the mains since the motor and switch are a stand alone motor assembly (SAMA).

I should also explain that my phono stage is the LFD LE/SE which has the large transformer.

The Piccolo is an experiment to see the various effects of loading on the cartridge. The designer of the LFD is a purist and feels that offering an MC gain stage with switchable loading, detracts from the sound quality, more than the benefits of the loading provide. Thus, he offers only the one load of 47k ohms in both the MM mode and the MC mode. His mc gain is also about 53db so it is a bit on the shy side with my Dynavector xx2 MC output of about 0.30mv. I also am listening with various Dennon DL103/R designs by Zu and Soundsmith and they all range in the 0.25 to 0.39mV range.

I thought I would experiment without spending $$$ and the Piccolo fit the bill nicely, with the gain and loading adjustable. It's no big deal if it does not work out. It was fun building it and having it work right away (except for the hum). I have not built a piece of stereo gear since the '70's.

I thought about the contact to the case and ground off the blue paint pretty thoroughly on both sides.