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Summit TPA200B hum/buzz Dual-Channel Preamps
Old 12th May 2016
  #1
Here for the gear
 

Summit TPA200B hum/buzz

Hello Everyone!

After 20 years of recording, I finally bought myself a Summit TPA200B. I waited a month and a half for it to arrive. When it did, it arrived broken. One channel was 20dB quieter than the other. Now, 3 months later, they've finally sent it back to me repaired.

I've been using it the past couple days, and it sounds wonderful... big, open, wide, blablabla.

The thing is, I now realize that it puts out a horrible buzz when I send phantom power to specific microphones. New 414XLSs make a huge buzz, but my 414 BULS is clean and pristine. My old C451EBs buzz, my U87s and Gefells do not.

The buzz will change volume depending on where the input and output knobs are set. There's a sweet spot, specific to each microphone, where the buzz is much quieter. Flipping the pad switches change the tone of the buzz. the gain can be turned all the way down, and the output will still buzz.

Does this make any sense to anyone? This has been thoroughly tested: different mic cables, different power cables, bypassing my patchbay altogether, everything... I plug a 414XLS straight into the back, and as soon as I turn on phantom, the buzz. Replace the 414 with a different mic, no buzz.

So, 2 questions:

Anyone see anything like this before?

If I return this thing, I would like to get a different tube preamp in it's place. What are your recommendations? I want something versatile... from clean and pristine to full blown tube distortion.

Thanks!

Colin
Old 14th May 2016
  #2
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toledo3's Avatar
 

How are you gain staging the TPA? While your description does seem to sound like something is possibly wrong, I will describe my take on gain staging the pre...

The output gain is your clean gain. If you want to run the preamps with the least saturation, what you would do is to jack that as high as it goes, then reduce the first stage accordingly, either by turning the input gain down and/or switching on the pad positions (usually for close drum mic and similar).

If you wanted to get more saturation, you would bring the output down, and jack up the input more.

In my experience, if you had the input jacked all the way up, and the output low, it would seem to magnify noise because those settings have a saturation/overdrive effect on the signal. If you have set the preamp up this way, different output levels of various mics might seem to cause different amounts of "noise".

But if it's setup to run clean and you're still getting that, seems like something is wrong.

I can definitely use mine and set them to run with no more noticeable noise than any other professional mic preamp, maybe even less than some.
Old 16th May 2016
  #3
Here for the gear
 

Thanks for your reply

The buzz I'm describing sounds like a full blown 300Hz square wave... it's as though the pre starts oscillating..

Since you haven't experienced my issue, I'll assume that this thing is still broken.

What a shame, I think that Summit have really lost it... a 4 month wait for a still broken preamp.

I guess I'm gonna have to return this thing and get something else.

Thanks again!
Old 18th May 2016
  #4
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toledo3's Avatar
 

Darn, that's too bad.

The only other reasons I can think that I have ever had it hum, is when I have had a macbook laptop power supply hanging around it, but the same macbook PSU does that to a number of other devices. I would also double check that you aren't ground lifting anywhere, because some gear really relies on finding proper ground as part of it's noise isolation system... and it's not bad for safety either. If neither of those things are happening, then I'm tapped out of ideas.

It's a shame that happened that way, because it is a great Dave Hill design, so versatile. I got mine used from Vintage King though, so they teched it on their bench first.
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