A blast from the past (well, hopefully not!)

Aussiebottlehead · 2406

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Offline Aussiebottlehead

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on: October 30, 2024, 09:11:29 PM
Hi folks, my first posting for many years! I have been happily listening to my Foreplay pre-amp as part of my home-made system until a couple of years ago. I then made the decision to retire my CD player and use a PC with JRiver Media Centre, which allows me to take advantage of some parametric EQ, high-res downloads and other 21st century innovations. As a consequence I bought a Wadia DAC/pre-amp and have been using that for a couple of years. What I now want to do is connect a DAC to my PC and start to use my Foreplay again. I bought a Topping D10 DAC and as a result of a long story I ended up with a balanced output unit rather than the unbalanced D10s unit. I think I have a handle on making a suitable cable to convert the TRS output on the DAC to an RCA input for my Foreplay, but I suspect that I should also attenuate the signal, as it will be 4V and therefore too high for my Foreplay. I searched the Forum and found an old thread ("Add XLR Input to BeePre2") which indicated that I should install a resistor on the Foreplay input. Is that all I have to do and if so, what value resistor should I use?
PK



Online Paul Joppa

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Reply #1 on: October 31, 2024, 04:00:42 AM
Foreplay has had several different input controls over the years.What version do you have? Maybe a photo of the inside would help.

Paul Joppa


Online Paul Birkeland

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Reply #2 on: October 31, 2024, 04:36:01 AM
I searched the Forum and found an old thread ("Add XLR Input to BeePre2") which indicated that I should install a resistor on the Foreplay input.
No, that thread says you should add two input transformers and two resistors...

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Doc B.

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Reply #3 on: October 31, 2024, 06:00:08 AM
Without knowing the source's balanced output circuit the transformer method is the best way to go from balanced to single ended. There can be simpler ways to do it with certain output circuits in the source, though those methods can cut the source level in half.

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


Offline Aussiebottlehead

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Reply #4 on: November 01, 2024, 02:20:24 AM
Hi folks, thanks for the replies! Paul B you are quite right, I misinterpreted the thread, it does say transformers, and BEYOND THAT, resistors. The DAC I wish to use has a TRS output, so what I'm thinking now is to just use a cable with TS plug at one end and an RCA plug at the other end for my Foreplay. But that will still leave me with a 4V source, which will be too high for the Foreplay wouldn't it? Paul J, I can't get at my Foreplay to photo it, as I'm repainting my listening room ATM and everything is stacked in one corner. My Foreplay instruction book is dated 1998 and I have installed the Anticipation upgrade. I also installed an Alps 438t 50kAX2 controller - is that the input controller information that you wanted?



Online Paul Birkeland

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Reply #5 on: November 01, 2024, 05:31:19 AM
But that will still leave me with a 4V source, which will be too high for the Foreplay wouldn't it?
Do you have the Sweetest Whispers attenuator or the two mono carbon potentiometers? 

The Foreplay can be made to accept any source voltage by adding a resistor either between the selector switch and volume controls to reduce the sensitivity of the Foreplay as a whole, or between the RCA jacks for one input and the selector switch to just pad one input.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Aussiebottlehead

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Reply #6 on: November 02, 2024, 08:10:01 PM
Thanks for that PB! With the constraints around where the ALPS volume control is placed in my amp, I think I'll pad the input. I also made a newby mistake by saying that I'd have 4 V input. If I use just one of the active wires from the balanced output, it should be half that, So there shouldn't be too much padding needed.
Once again, thanks for all the advice folks!
Regards
PK