Noise using reduction preamp as tube buffer

Dustin · 1686

0 Members and 1 Guest are viewing this topic.

Offline Dustin

  • Newbie
  • *
    • Posts: 2
on: June 10, 2020, 06:21:51 PM
Hello,
I purchased a used phono tube preamp with the reduction kit and upgraded power cable.  I have some concerns adding this preamp using one of the Line In inputs on my integrated receiver (power and preamp built in). So far the results sound great.
I grounded the receiver to the preamp, and it sounds great when I listen to CDs, but when I cycle through the the different inputs on my receiver when everything is on, there is a low frequency cycle/hum that sounds like a car in idle, only coming through the right speaker channel (sorry if my terms arent good). When I switch back to CD input on amp, its not very noticeable.
I originally went through the Tape connection on my old receiver and a few of the LED lights were pulsing to the music (1/2 of board). But now I’m  running through the Line In input the LED lights are always on. Odd..

Thank you in advance for the help!
-Dustin



Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
    • Posts: 19406
Reply #1 on: June 11, 2020, 05:44:27 AM
The LEDs in the Reduction are pulsing with the music?  Are you using the Reduction with a turntable?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Doc B.

  • Administrator
  • Hero Member
  • *****
    • Posts: 9570
    • Bottlehead
Reply #2 on: June 11, 2020, 09:22:58 AM
Reduction as a tube buffer? That is the wrong application. Reduction is a phono preamp, not a buffer. I'm guessing this is maybe just a confusion of the terminology. If the LEDs were pulsing on the tape input but not pulsing when connected to the line input there is possibly a very low impedance at the tape input channel that is on the pulsing side, that is loading the Reduction output down. As to the noise - for starters try swapping the tubes and see if the noise follows a tube.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
    • Posts: 19406
Reply #3 on: June 11, 2020, 09:42:12 AM
You can definitely get the LEDs to pulse if you overdrive the circuit as well.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Dustin

  • Newbie
  • *
    • Posts: 2
Reply #4 on: June 12, 2020, 03:29:36 PM
Doc,
Thank you for the input (& from other members as well). Tube buffer probably isnt the right term for me to use then. Your knowledge on this matter is superior to mine.. haha.
I’m no longer using the tape connection, I’m using a line because it is safer with higher voltage devices from my understanding. And no I’m not using this with a turntable, just running it by itself at lower volumes (just adjusting volume from the integrated amp Yamaha R-S500. I’m impressed by the liquid mids I’m getting out of my CDs!  :o



Offline Paul Birkeland

  • Global Moderator
  • Hero Member
  • *****
    • Posts: 19406
Reply #5 on: June 12, 2020, 03:41:45 PM
This is totally the wrong use for this product.  The Reduction has equalization to undo the equalization that's used when records are cut.  If you play a CD through this, other than overdriving the Reduction, you will have +20dB of extra bass and -20dB of missing treble.  \

The Reduction is only useful with a turntable.  If you don't have a turntable, you don't need (and shouldn't use) a Reduction.


Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man