First Build - Fantastic!

[Paul Joppa]

A few years back I bought several inexpensive attenuators. The Harrisons had a 10K input impedance, low but workable. The others I got were all 600 ohms, far too low for our purposes. None of them had a specification for this important parameter. I think the low impedances are widely used in car audio systems.

[Kris]

A few years back I bought several inexpensive attenuators. The Harrisons had a 10K input impedance, low but workable. The others I got were all 600 ohms, far too low for our purposes. None of them had a specification for this important parameter. I think the low impedances are widely used in car audio systems.

Interesting... Thanks for sharing Paul.

[Adrian]

For reference, the attenuators I'm using are from Rothwell.  I'll have to look it up cause I don't know the particulars for this attenuator.  I know I like the sound now but you have me wondering if I need to be more critical and do an A/B comparison.  Maybe I can have my wife swap them out and make it a blind test?

I got Harrison Labs 12 dB attenuators. They were mentioned couple of times here on BH forum and people reported to have good results when matching them with crack amp, but it looks like they are not good in my setup.
I strongly suggest to pull your attenuators out and give your amp a listen without them... just don't forget to post back as I you got my curiosity now.
 
Cheers,
Kris

I will try my best to A/B test these on the Crack.
I've got to say that I have used these Rothwell attenuators in my system for several years.  I have a Marantz 2325 Receiver and have used them between the pre-amp and the main amp and also tried them on direct input from the CD.  I remember immediately hear less noise leaving a clearer signal.   I have never had any perceived loss in frequency response nor heard any stray sounds that weren't there without them.  The system's response, especially at lower volume, was always smooth and clear.
Now that I can use them with this new piece of equipment I have an opportunity to see if they measure up to their performance in the solid state amp.  This "test" will probably take 2 - 4 weeks to give the proper critical listening required for the fair-shake it deserves.  I'll post back with my "findings".
It's amazing how subjective this audiofool hobby is.  I can find something to be absolutely awesome while someone else will not.  Kinda like Lenard Audio and Elliot Sound Products flameing on single-ended vs. the coveted Class A push-pull!

[Adrian]

Results of my A/B test of the Rothwell attenuators on the Crack OTL:

I tested with/without the attenuators in both the Crack and my Marantz 2325 receiver.  With the exception of having a finer control of the volume at low levels I honestly cannot tell any sonic difference with or without the attenuators when used on the solid state 2325. However, I can perceive some difference when used on the valve driven Crack.

First, I tried to keep the source material as high quality as possible.  I chose mostly vinyl analog albums from Speakers Corner and Mobile Fidelity of 180 or 200 gram weight.
The selections were:
Theloniuos Monk with John Coltrane
Charles Mingus (Tiajuana Moods)
Dave Brubeck Quartet (Live at Carnege Hall)
The Who (Quadrophenia)
Linda Ronstat (Don't Cry Now)
Diana Krall (The Look of Love)
Norah Jones (Come Away With Me)
Miles Davis (E.S.P.)
The Beatles (Sgt. Pepper)
The Eagle (Hotel California)

I selected these because I am familiar with them and think they cover a wide range of styles, instuments, vocals, etc.
Bottom line:  I did find some difference with using the attenuators.  The difference in all cases was very slight and I had to be very critical when comparing selections and passages to notice the difference.  What I heard with the attenuators was a veiling of some sounds.  Again, this was a small difference but perceivable.  For example, some of the brush strokes on the drum heads on Thelonious Monk with John Coltrane were not as present; Charles Mingus' and John Entwhistle's (The Who) bass lines seemed just not all there (if that makes sense).  Miles Davis' trumpet appeared unchanged but Herbie Hancock's keyboard stepped back a little in the mix.  Linda Ronstat, Diana Krall, and Norah Jones vocals were just a tiny bit backed off and not as present.  Some passages and notes of The Dave Brubeck Quartet were not as sharp.  Imaging on The Beatles and The Eagles was unchanged.
All of these differences I perceived with the attenuators would not be noticed if I wasn't really listening for something.  I realize that when we look for something we either find it, lose it, or it really doesn't exist (like in physics:  if you are looking for wave properties then that is what you see, and when looking for particle properties you cannot see it as a wave).
I will probably use the Crack without the attenuators on vinyl playback.  This is partly due to the somewhat lower input signal strength of the phono stage (provided by my Marantz receiver).  The stronger input signal from the CD I can live with but if I want to listen to the FM tuner the signal is so strong that I find using the attenuators more enjoyable.
Like I said in an earlier post, this audiofool hobby can be separated into objective and subjective tastes.  Objectively it boils down to "how does it measure" and subjectively it is all about the experience.  I am of the subjective camp (mostly) and my experiences when listening to music are subject to change.

[lordnikon]

Let's see if this works:
First pic shows the in-line attenuators (from Rothwell)

Where did you get the L-shaped 1/8 adapter?

[Adrian]

lordnikon:  At Radio Shack.

[Adrian]

Done with the Crack OTL.
Stripped and stained the base (ebony) to match my S.E.X. 2.1.
Masked and painted plate to also match.

Now, saving for the Submissive, then EROS, then Stereomour.....

[xcoolhandx]

nice set up Adrian ,congrats