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Author Topic: Phono Preamp Frequency Response  (Read 11195 times)

John Roberts {JR}

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Re: Phono Preamp Frequency Response
« Reply #20 on: December 27, 2013, 09:32:19 am »


JR,
Please don't confuse my statement concerning quality components with the precision of said components. High quality components are just that, regardless of degree of precision.

And please don't confuse mine... This thread is about phono preamp frequency response, which IMO is/was a precision exercise, at least for premium preamps.
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I'm fully aware of the desired goal concerning the design of a pre amp, and I can appreciate the overall increase in quality of the majority of the off the shelf pre amp packages which has been achieved over the decades. However, please be aware that the goal when building, designing, or rebuilding the first gain stages of any guitar amplifier is to also provide the following gain stages with a quality distortion free signal. Granted the majority of most guitar and high end audio components is built around the all too common 12AX7, however, there are at least a dozen or so suitable substitutes I can use in it's place.
 

I'm not sure the 12AX7 is a problem but I am not a big tube guy... I did share lab space and friendships with senior guitar amp engineers over a 10-15 year period, and we would often chew the fat over our respective design challenges. Yes, first guitar amp stage is clean (linear), very high input impedance, and must handle voltage peaks from hot/active pickups without saturating.
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My other statement concerning component choice and quality has nothing to do with component precision. It has to do with the component tonal factors, which I can guarantee exist. The ability to tailor these circuits to specific tonal needs keeps me away from the "bug" making me unqualified to design or alter those solid state circuits. However, this is not the case with tube circuits, which to me, and based on the ability to modify those circuits well beyond the original design, makes those type circuits more appealing overall.
 

Another potential difference perhaps, in phono preamp design, components that add coloration are avoided. I would use polystyrene caps for EQ because of their near ideal behavior. Polystyrene are not widely used today because they don't tolerate the temperature of modern soldering processes. These days they make NPO/COG capacitors that are quite neutral. I don't know if they come in large enough values for use in tube circuits (or in leaded packages).
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I find it very strange this has become the discussion as I have a Labsters Fender "The Twin" up on the bench as we speak. The problem? Overcoming the poor sound quality and distortion introduced through the solid state portion of the pre amp circuit. Not one of Fenders best designs.

Solid state does not have to suck, while solid state clipping sounds crap. I recall near the end of my tour at Peavey working with one junior amp engineer to investigate using JFET front ends, which will exhibit tube like input impedance. Coincidentally during this time, Peavey worked on a solid state mimic of tube overload that did not suck (transtube), but that's a whole nother discussion.

I don't know how this became about guitar amps. IMO Apples and oranges. I am surely repeating myself, but one is a precision playback path to accurately reproduce a prerecorded signal, the other is an extension of a musical instrument creating original sounds.

Merry Christmas Bob..

JR   
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Steve M Smith

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Re: Phono Preamp Frequency Response
« Reply #21 on: December 27, 2013, 11:23:01 am »

the other is an extension of a musical instrument creating original sounds.

That's exactly how I think about guitar amps.  They are a part of the instrument and shouldn't be thought of as an additional item to make it loud.


Steve.
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Tim McCulloch

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Re: Phono Preamp Frequency Response
« Reply #22 on: December 27, 2013, 02:47:00 pm »

That's exactly how I think about guitar amps.  They are a part of the instrument and shouldn't be thought of as an additional item to make it loud.


Steve.

How about an extension of the instrument that does not, buy it's very nature, make the instrument too damn f@#(&ng loud?
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Steve M Smith

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Re: Phono Preamp Frequency Response
« Reply #23 on: December 27, 2013, 08:44:06 pm »

How about an extension of the instrument that does not, buy it's very nature, make the instrument too damn f@#(&ng loud?

Possibly.

I think I'm the only guitarist who gets asked to turn up instead of down!


Steve.
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John Roberts {JR}

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Re: Phono Preamp Frequency Response
« Reply #24 on: December 27, 2013, 09:31:34 pm »

There are some actual reasons why guitarists tend to play loud.

#1: to create an acoustic feedback resonance between the amp speaker output and the guitar/strings takes SPL, not gonna happen turned down at easy listening levels.

#2: The characteristic tube saturation sound occurs at clipping, so at peak amp power output.

This does not excuse the loud sound, just kind of explains it.

JR
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Bob Leonard

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Re: Phono Preamp Frequency Response
« Reply #25 on: December 28, 2013, 02:55:29 am »

The very reason for the right amp for the size room. Back in our day JR FOH didn't really exist and amps of the day filled the room. Today there's no excuse for having the right tool for the job, and in most cases that means a smaller amp.
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BOSTON STRONG........
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I did a gig for Otis Elevator once. Like every job, it had it's ups and downs.

Steve M Smith

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Re: Phono Preamp Frequency Response
« Reply #26 on: December 28, 2013, 05:15:39 am »

I can get all the speaker to guitar resonance I want and the right sound with enough volume to fill the smaller pubs we play in using a seventeen watt WEM amplifier (2 x EL84).

For larger pubs I have a Line 6 Flextone with 65 watts.

Larger venues where a PA is provided, I go back to the WEM and put a microphone in front of it.

However, I'm playing 1950s rockabilly, not rock.

Trying to get back on track, the difference between an RIAA pre-amp and a guitar amp is that RIAA defined the characteristic and left it to circuit designers to create a pre-amp which conformed to it.

In the case of the electric guitar, the deficiencies inherent in the technology of the time such as overdriving the output stage and compression caused by loading the power supply actually defined what we now know of as the classic electric guitar sound.  If 1940s amplifier technology was better, we might be playing much cleaner, more clinically sounding guitars and rock might never have happened (Imagine Jimi Hendrix with a hi-fi guitar sound!).


Steve.
« Last Edit: December 28, 2013, 05:23:10 am by Steve M Smith »
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Bob Leonard

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Re: Phono Preamp Frequency Response
« Reply #27 on: December 28, 2013, 10:57:07 am »

What's the model of what appears to be a blonde Gretsch? Looks like a Setzer 6136, but it's hard to make out.
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BOSTON STRONG........
Proud Vietnam Veteran

I did a gig for Otis Elevator once. Like every job, it had it's ups and downs.

Steve M Smith

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Re: Phono Preamp Frequency Response
« Reply #28 on: December 28, 2013, 01:53:29 pm »

It's a 6120 Amber Maple.

I didn't want to go for the cliche orange finish and when I saw this one with gold hardware, I knew I had to have it.


Steve.
« Last Edit: December 29, 2013, 04:15:59 am by Steve M Smith »
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Bob Leonard

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Re: Phono Preamp Frequency Response
« Reply #29 on: December 29, 2013, 04:00:47 am »

The perfect guitar for rockabilly. Nice choice!!
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BOSTON STRONG........
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I did a gig for Otis Elevator once. Like every job, it had it's ups and downs.

ProSoundWeb Community

Re: Phono Preamp Frequency Response
« Reply #29 on: December 29, 2013, 04:00:47 am »


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