Latest King/Cello preamp

Joe Galbraith

Senior Member/Sponsor
Apr 22, 2010
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Nice. What are the controls on the output box? Three for each channel I see.
 

Ki Choi

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May 13, 2010
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Nice. What are the controls on the output box? Three for each channel I see.

Looks to be Gain, HF and LF. Glad Charles added LF to tame the excessive head bumps on some heads including Studer - something I had been suggesting for from the beginning.

So Manley Tube Tape Head Preamp and above K/C model have LF adjustments.
 

Dre_J

Industry Expert
Mar 5, 2012
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Looks to be Gain, HF and LF. Glad Charles added LF to tame the excessive head bumps on some heads including Studer - something I had been suggesting for from the beginning.

So Manley Tube Tape Head Preamp and above K/C model have LF adjustments.

Ki,

That's an interesting comment. Is there a frequency response chart/graph that shows what this bump looks like? How big is a typical bump like this? Does it show up in playback, record, or both?

Thanks,
Dre
 

Bruce B

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Apr 25, 2010
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Ki,

That's an interesting comment. Is there a frequency response chart/graph that shows what this bump looks like? How big is a typical bump like this? Does it show up in playback, record, or both?

Thanks,
Dre


I don't notice a "head bump" with Flux heads


Studer head bump.gif
 

rockitman

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Sep 20, 2011
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those adjustment knobs sure beat the micro screwdriver pot type I have on the sides of my unit for HF only. How much is this unit w/o VU console ? Is the circuitry basically the same cello layout as before save for LF adjustment or has something been done to improve the sound ?
 

Bruce B

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Apr 25, 2010
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Thanks Bruce.

Can you give me a quick reply of what I'm looking at (red and blue lines represent) in the frequency response graph? Left and right channel? Head output? Line output from tape pre? or something else?

Dre

Blue line is 15ips
Red line is 7.5ips
 

stellavox

Well-Known Member
Apr 23, 2010
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Hi Guys,

A few comments. Ki correctly noted the functions of the potentiometers for each channel. There is also a fixed (50dB) / variable gain switch.

Regarding "head bumps", these happen when the wavelength of the recorded signal gets close to the physical length of the face of the head's pole pieces. In effect, certain low frequencies on the tape resonate with the head and the "ringing" shown in the above low frequency response curves reflect this fact. Designers of tape playback amplifiers have two choices to "tame" or dampen this effect: put a variable dampening resistance across the head or across the equalization circuitry - most do it in the EQ network.

Measuring the "bumps" is tricky because if the actual test signal recorded on the tape is wider than the width of the tape head, "fringing" will occur which will overemphasize the magnitude of the bump. Most alignment tapes are full track and MRL does provide a table in their documentation which lists "correction factors" to be applied to the measurements.

Per a lot of trial and error, I've found a single "suitable" resistance value that seems to work with most of the heads I've experienced and put this fixed value in all my "standard" preamps. Otherwise, nothing new.

Charles
 

JackD201

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Apr 20, 2010
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Those look ready to ship out Charles. ;)
 

Bruce B

WBF Founding Member, Pro Audio Production Member
Apr 25, 2010
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Per a lot of trial and error, I've found a single "suitable" resistance value that seems to work with most of the heads I've experienced and put this fixed value in all my "standard" preamps. Otherwise, nothing new.

Charles

Considering all the variables (head brands, tape formulations, wire and electronics), the only true solution would be a parametric EQ with variable Q. Otherwise, it is best left alone.
 
Last edited:

Ki Choi

Member Sponsor
May 13, 2010
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I don't notice a "head bump" with Flux heads


View attachment 8869

Dr. Brice:

I assume your graph is the output of FMEFR Head via Studer preamp electronics where bass response (~40Hz-~50Hz) has already been "tamed" during the calibration process. Otherwise, it is impressive to see how "flat" it is... in comparison to what I had personally experienced with Studer and Nagra heads via outboard tape head preamp I had on hand.

Rich Brown was visiting me with once with his King Cello. We had ~+4dB response in the bass region with my preamp and ~+10dB with Rich's King Cello. That was almost two years ago...
 

jdza

Well-Known Member
May 3, 2010
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IME the effect of fringing on measurements can be huge. Stellavox referred to this above.I recently acquired calibration tapes with fringing compensation and was startled at how different they measure from the regular MRL tapes in the bass. Jay McKnight refers to this in his excellent papers but reading something and measuring it are two different things.

All calibration tapes are not created equal! Like everything in tape all is never as it appears. In the end I just have to trust my ears but if the absolute reference closest to the original is under scrutiny it can be very tricky!
 

stellavox

Well-Known Member
Apr 23, 2010
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Hey Guys,

Let's not make "a crevasse out of a head bump", and scare people away. The result, when listening, can actually be very small. As you increase the LF "dampening", the resonance peaks are tamed, but too much and the lowest frequencies start rolling off.

Compromise time.

And the main "bump" depending on where it is - in conjunction with the music on the tape - and the speakers/room - can actually be "quite euphonic".

I've mentioned to a few folks that, "I never met a headbump I didn't like"!

Charles
 

flez007

Member Sponsor
Aug 31, 2010
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Hey Guys,

Let's not make "a crevasse out of a head bump", and scare people away. The result, when listening, can actually be very small. As you increase the LF "dampening", the resonance peaks are tamed, but too much and the lowest frequencies start rolling off.

Compromise time.

And the main "bump" depending on where it is - in conjunction with the music on the tape - and the speakers/room - can actually be "quite euphonic".

I've mentioned to a few folks that, "I never met a headbump I didn't like"!

Charles

Good point Charles, the sum of benefits is way larger than the omissions.
 

stellavox

Well-Known Member
Apr 23, 2010
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Ki,

Didn't take (or send Rich) a pic of the "backside". Just a cable to a (second) jack on the pre, where it gets it's power and signal, and two RCA's for the auxiliary (switched) input.

Charles
 

Ki Choi

Member Sponsor
May 13, 2010
764
29
1,590
Seattle WA area
Ki,

Didn't take (or send Rich) a pic of the "backside". Just a cable to a (second) jack on the pre, where it gets it's power and signal, and two RCA's for the auxiliary (switched) input.

Charles

Hey Charles:

Those of us with previous versions of King Cello Preamps would be interested in how the new model is different sonically from what we already have and how we can fit the new VU meter Panel into the older version KC preamps to see the VU meter needles dance.
 

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