? specs on Bugle Pro - no subsonic filter

PatOMalley · « **on:** 31 Jan 2006, 02:27 am »

Hey Jim,

Can you explain the specs for the Bugle Pro?
RIAA Response 30Hz to 60kHz
Bandwidth 15Hz to >150kHz

Does this mean that the bottom is 30Hz which means that a subsonic filter is not needed because the equilizer does not reproduce even down to 20Hz?

If so, what does the bandwidth spec represent?

And does all this mean that in the end we will not see any woofer pumping?

hagtech · « **Reply #1 on:** 31 Jan 2006, 04:48 am »

The bandwidth is the -3dB points. The EQ is within +/-0.5dB over a smaller bandwidth. This has the equivalent of a 15Hz subsonic rolloff.

I don't like to push the bandwidth too low for phono stages. Nice to hit 20Hz without too much loss, but you really gotta drop it or you get a lot of amplification for warps, rumble, tonearm resonance, etc. And as you mentioned, woofer pumping and burning extra power. You needlessly heat up those voice coils.

The graph on the Bugle page says it all. Flat from 13Hz to 450kHz.

jh

jcoat007 · « **Reply #2 on:** 1 Feb 2006, 11:18 pm »

Interesting post, as I have woofer pumping when I use my TT. I have posted here about it with little or no response as to what causes it. I am using an EAR 834p. I have used other phono stages, and not had this pumping.

I guess I should think about another phono stage, or a subsonic filter.

analog97 · « **Reply #3 on:** 2 Feb 2006, 12:42 am »

You should check out the Cornet2. You can build one for less than half of the price of an EAR 834. Compare the guts of the EAR to the guts of the Cornet2. That's what I did. I have no sub-woofer pumping. The Cornet2 is very well behaved. It is an absolutely phenomenal phono stage. The EAR uses some pretty cheap capacitors. I did the Cornet2 with premium Auricaps.....still half the price of the EAR. To me the comparison is a no-brainer. Sorry about the woofer-pumping.......

jcoat007 · « **Reply #4 on:** 2 Feb 2006, 02:22 am »

I have a fairly upgraded and hot-rodded 834p, but the woofer pumping is annoying.

I do need to check something else out.

Thanks

Steve

analog97 · « **Reply #5 on:** 2 Feb 2006, 02:36 am »

I had subwoofer-pumping once with a lesser phono stage than the Cornet2. It occurred when I closed the lid on my turntable. I had read that this can somehow amplify the low frequencies and cause the problem you experience. The EAR is competent and should not be the culprit. Let's see if someone else with more experience chimes in. Larry

hagtech · « **Reply #6 on:** 2 Feb 2006, 07:13 am »

Quote

I guess I should think about another phono stage, or a subsonic filter.

The problem isn't likely the phono, it's the TT. Or more likely the stand or rack. My guess is that you can hear foot falls too? You might need a wall mount. Depends on your floor.

Aha, but you be right. Is this only when playing music? What if needle is up? If you still have pumping, then it is related to the power supply in the phono. Maybe power line fluctuations are getting through.

jh

PatOMalley · « **Reply #7 on:** 2 Feb 2006, 12:24 pm »

... but if there is no subsonic filter and the freq range is below 20Hz then the phone pre will send subonic signal down the chain.

To get rid of this you can use a filter or rolloff.

If the pre is not doing either then the signal gets thru.

Does the EAR use a filter or rolloff in the sameway that the Hagerman does?

I am really only a piker in this area and defer to the more-experienced.

hagtech · « **Reply #8 on:** 2 Feb 2006, 06:59 pm »

I'm pretty sure the EAR has an output coupling capacitor. When paired with the input resistance of the next stage (volume control), you get a high pass rolloff. That can be the subsonic filter.

In the CORNET I use C5, earlier in the circuit to set this frequency. That makes it consistent and not dependent on system interactions or other equipment. It also helps to eliminate overloading of the second gain stage.

jh

PatOMalley · « **Reply #9 on:** 2 Feb 2006, 08:38 pm »

Quote from: jcoat007

I have a fairly upgraded and hot-rodded 834p, but the woofer pumping is annoying. Steve

maybe the mods changed something.

hagtech · « **Reply #10 on:** 3 Feb 2006, 04:04 am »

Oh, I didn't notice the hot rodding. If you just swapped out caps, fine. But if you played with the circuit, could be unstable. Motorboating. Maybe shifted values too far. There are often precise reasons why a designer does certain things. Usually, it's not possible to determine such by mere inspection. Many things are not obvious.

Anyway, the 834 is a feedback type phono stage. Could be prone to oscillation. You might have too much open loop gain at the low end.

jh