[Danberg]

I still have my GAS Theobe Pre amp that has a built in phono amp.  Recently purchased a low output MM cartridge.  Any opinions on how I can use this older GAS unit's phono pre amp and connect to my Audio Research LS-16 MkII line stage? 

Is there a way not to use the GAS volume control. Do I connect to from the GAS output jacks to the AR LS-16 inputs?  I'm concerned about overdriving the AR LS-16 line stage and possibly damaging it.  Basic hook-up info would be appreciated.  I'm a newbie so keep the description detailed.

[TheChairGuy]

Hi Dan,

Does your GAS Theobe have Tape outs (in other words, does it have a 'Tape' function?)? 

Does the GAS Theobe have a moving coil stage (or, I think maybe GAS labelled it 'Head Amp')...if not, you cannot use your newly purchased low output moving magnet with it. (what cartridge did you buy?...that's just an aside - I'm curious  )

However, if you do have 'Tape Outs' (look for rca outputs on the back that say this or very similar) AND a selector on the front of the unit (and corresponding inputs on the back labelled 'Phono In' MC or Moving Coil or Head Amp).....you're in business.

Here's the steps to do it:

1. Take the rca leads from your turntable and plug them into the GAS rca jacks marked Phono/MC/Head Amp or some such on the backside.

2.  Hook up an interconnect from the 'Tape Outs' of your GAS, to a jack on the back of your AR marked 'Aux' (or similar)

3.  Hook up your AR to your power amp as you normally would

In this fashion, you are using your moving coil phono stage of your GAS, into your AR....and you bypass the GAS volume controls.  The AR will be your volume control. I am not an engineer, nor a technophile on these kinda' things, but I don't believe there is any chance of 'damaging' your line stage in our AR preamp - at all.

About the worst thing that can happen is that, for some reason, you don't like the combination...then you can just try the GAS as your main preamp for phono listening (simply shut your amp off first and move the interconnects from one preamp to another - a 30 second procedure).  This way you have a dedicated preamp for your phono pleasure and one for your tuner/CD, etc.   

Whichever you choose - have fun and we hope to see you chiming in on matters here on the Vinyl Circle 

John

[Danberg]

Thanks for the detailed information.
My turntable is a Clearaudio Champion (purchased used)
Cart. - Micro Benz ACE - moving magnet  (0.9mV)
RB-350 aftermarket arm
Thanks for asking

[TheChairGuy]

Dan,

For a newbie - you sure are starting your vinyl adventure right.  Your choice of starter package is really good

However (sorry, there is a however), a good bit of getting your vinyl rig to sing is implementation.  Getting that cartridge aligned in the headshell, making sure your TT is on a stable platform, etc.  If these things aren't met, you'll soon feel all the time and efforts assembling your nice system have been wasted.  It's a process of learning, so don't be dismayed if it takes a while to 'get the hang of it'.

About your system:

* The Benz-Micro ACE is actually a moving coil, not moving magnet.  As such, your particular one probably sounds best with a resistive load of 500 ohm or so.  Anything higher and it might sound 'bright'; if you load it lower it might sound overdamped and 'dead'. Proper resistive load is an oft-overlooked critical link in getting your rig to sound 'whole'....improper loading will get you lackluster results most often.

If your GAS only has an MM input...the load would likely be 47,000 ohms....far too high for your particular cartridge.  If you have a MC or Head Amp function, it will likely be loaded at 100 ohms or so....too low for your particular cartridge.

* A potentially larger issue for you is that your cartridge is actually a middle output device (neither low nor high at 0.9mv).  It likely needs somewhere in vicinity of 46-50db gain to sound dynamic and fully fleshed out. If you only have a MM function it is likely 36-40 db - your output will sound weak.  If you use an MC stage (if you have one), it's probably got a gain of 56-62 db....your sound will be overboosted and sound shrill and, to many, unbearable.

I don't mean to throw a monkey wrench in your fun....but I also don't want you to throw your hands up in disgust if you're not happy with the set-up at first.  There are remedies to the issue, and not all cost an arm-and-a-leg to overcome.

Put what you have together, and listen.  If you like what you hear (it COULD happen) it's all moot. But, what will likely happen is that you'll not quite get it right the first time out...just keep reading, learning and asking questions and it'll soon sort thru for you in and over time.

If any of this is over-year-head in understanding now...it'll be understandable in time. Just be patient and give it all time to gel.  I really believe that vinyl offers up a better musical experience than CD/digital for less money on average....most folks that haven't found this to be true haven't gotten all the nasty little, infuriating  details right - or have never tried at all.  Give your new analog set-up some love and nurturing and it will pay you back in many ways in the future 

John

[Danberg]

Thanks again for all the information.  I WILL take the time to take advantage of your suggestions.

My 1st interest in this "audio" hobby started right out of high school.  At that time the only playback medium was 1/4" tape and record albums.  I know how good albums can sound as I was "raised" on them. 

However, I don't recall all the fussing around in cartridge installation, VTA, or having to worry about "loading" of the cartridge.  I'd just purchase various cartridges, install them in the headshells, use a simple device to check for overhang, and they all sounded fine. Just put the record on the turntable, play the records and enjoy the music.

My 1st "good" turntable was a direct drive Kenwood KD-500 (concrete resin base) with the standard Kenwood "S" shaped arm.  I still have it in fact.  The cartridges I used (and still have) were Audio Technica XLE-40 and AT-122.  Also, miscellaneous Shure and Grado cartridges.  While each having it's individual sonic characteristics, they all sounded fine.

I am disappointed with the "new" turntable set-up I currently have.  My Cd's have a fuller sound in general.  More bass (deeper bass) which gives them that fuller sound, I'd imagine.  My records tend to have more of a tinny sound in general.  Without question my older turntable setup had a more balanced sound as I recall.  I just assumed that the Audio Research LS-16 MkII line stage is more detailed and lended itself to (more compatible with) the CD format.

*One more critical piece of information I never told you.  The phono preamp I am presently using (purchased used): 
Monolithic Sound HC-1b power supply,   Monolithic PS-1 Phono Stage modded by Dan Wright. 
Settings:
Subsonic filter = "off"
Load Impedance = 1k
Capacitance = 370pf
Gain Level = Hi-Gain
Interconnects: Nordost Quatro-fil

With this information if you have any other comments, I'd appreciate them.
   

[TheChairGuy]

Dan,

Why do you want to use your GAS as your phono stage if you have a Modwright modded CIAudio phono amp at your disposal?  Maybe I missed something 

Hi gain, I think on that model is 53db...probably too high (there are many factors that o into that, however).  46-50 should be about right...and I think you have adjustable gain on that baby. Use as little gain/boost as you can (it's quieter)....but judicious use of gain and you will find that dynamics and the overall presentation just snap in place for you. You need a little trial and error on this...but try 46db to start (or something close to it)  and move up from there until you dial it in right.

Anyhow, Benz recommends 200 ohm loading for your version of the ACE....if CIAudio has that load value, use it.  If not, toggle between 100 (that's a usual place for most makers to set values) and 1K to hear which you prefer a little better.

Also, put the subsonic filter 'on'...it's rarely a bad thing. For moving coils, capacitance does nothing sonically (there is a loooooong reason for this - never mind now - your head's about to explode  ).  Switch capacitiance to zero.

I think Nordost cables are likely high capacitance..it is of no concern with a moving coil, but if you mound your Shure be careful not to use too much capacitance as it will greatly reduce top-end response.

If you still have your Shure and Grado's you may want to mount them too.  I haven't heard enough low output moving coils to make a definitive statement about them, but thus far I find the Grado's to sound more musically natural and pack a better bass line.  Moving coils are more nuanced - greater detail and quieter internally (due to lower inductance and resistance figures), but it seems to be a trade off for fullness, bass lines and a bouncy good time.  It's all a tradeoff and you end up taking one side or another if you  stay in vinyl.

Do set your moving coil up right...then put your Grado on afterwards.  You may end up preferring it 

fyi, I never fussed with VTA, loading, etc either until recently.  It's wringing that last 2-5% performance from your rig all these things....it probably won't make a vinyl rig enjoyable to you if it isn't before all the fussing. If you don't like your cartridge no how all the fussing on that last 2-5% ain't gonna' fix it.

Frankly, a good vacuum cleaning machine, I've found, is worth more than all the fussing and, possibly, any swapping of cartridges, too.  My CD player often sounds preferable to my vinyl...until I clean that record (I only do it once per lifetime....once you clean the deep seated gunk out and spot clean with a carbon fibre brush, it stays clean for perpetuity).  Once cleaned, I've rarely found a CD that equals that (cleaned) record. 

Records just sound phenominally better after a good vacuum cleaning...but that's another $300 or so to spend on this veritable sink hole of a hobby. I hate the process of cleaning them , but I've found for 25 years the benefits of doing so. 

[blakep]

Using the Monolithic:

Based on what I read about your phono stage (before modifications), I'd suggest trying hi-gain (I don't think medium will be enough), 100 ohm load and probably just turn capacitance off as Chair Guy suggests-in the worst case scenario you could experiment with capacitance.

I don't think medium gain (at around 46 db. I believe) will do the job for you for you with .9 mv., and the load at 1K is killing you as far as I'm concerned. That is probably the bulk of your problem.

Other than that, check VTA, VTF and alignment to make sure they are all really dialed in.

[Danberg]

To answer your question ChairGuy... Why do you want to use your GAS as a phone stage if you have a Modwright CIAudio phone amp?

Simple, the GAS years ago sounded much better than my current CI Audio phone amp.  Wasn't sure how to set all the switches settings on the CI Audio phone amp.  Your response will be used next time I get to listen to my system. I'm sure your info will help greatly.

Also, the medium gain is WAY TOO LOW, no sound at all... the medium hi-gain is also quite low. Moderate listening levels has my AR line stage volume between the 3 o'clock to 4 o'clock position (5:30 o'clock is FULL VOLUME).  For me, moderate listening level is in the 75 to 82 db range.  Hi-gain setting closely matches volume of my CD player (which is about 11 o'clock on the volume indicator for 75 to 82 db playback level).

I assume from your comment that you feel that the CI Audio Modwright phone amp was a good starter choice for getting back into vinyl.  That unit is not the source of my unhappiness with the general sound of my records.  From your experience could the synergy of the equipment be the problem (turntable, arm, phone amp, interconnects)?  The cartridge?   I could mount the Shure cartridges which I was most familiar with on my GAS system and see how it sounds with my current system.

[TheChairGuy]

Hey Dan,

Gain is a function of your amp, too. If your amps have low gain, you'll need to use more gain at your phono stage to get the boost you need.  Unfortunately, if your GAS does not have a hi gain/MC/head amp setting....you'll have to use your CIAudio phono pre for boosting your signal(with the Benz).

If your not thrilled with how the CIAudio sounds in-line, it may not be the fault of the preamp.  Those eeny-weeny cartridge signals, measured in millivolts and many hundreds times less than line level sources, hate jumping over barriers...ie., solder points, metal-to-different metal, and, of course the kicker, RCA inputs/outputs.  Using a phono pre (which you have little choice in doing to boost your Benz 50+db needed), you have added another set of inputs and outputs.

Your Shure, Grado et al, ran straight to a phono stage, picking up no extra noise in the process, and runs thru only one RCA input until it reaches your amplification stage of your preamp.  I hear the degradation of the phono signal every time I go thru an intermediary...as opposed to run straight to the preamp with internal MM gain stage.  Every time. Less is very much more with phono signals.

I'm not one to stress 'synergistic' issues.  I think synergy is about 4/5th's electrical reality and 1/5 subjective hearing differences we all have. 

I hear an extra rca input/output added and polluting the signal.....but I don't hear phase well (while others sit slack jawed at my profound dead ears to that phase effect  )  I can hear a violin or piano that sounds off for some reason.....but I don't carefully distinguish bass lines (I know only if I like it or don't - I have trouble specifying/quantifying that aspect of sound).  But, those differences are only about 1/5 of the picture. 

The rest is some aspect of your systems electrical reality.  I found getting rid of my otherwise excellent BPT power conditioner and a shrillness vanished from my system that I could track down otherwise.  Some can't live without their BPT, mine was a clear trade-off that I can live without.

So, swap out those IC's, change your cartridge, turn your lights and computer off (I can hear serious degradation of phono, but not CD, with either overhead lights or 'puter on).  Above all, the experience with vinyl is different...the dynamic range of perhaps 50db is far less than CD's 96db, about the lowest frequency on even the best albums is perhaps 35-40Hz (CD reaches right down to the 20hz). 

So, if your DC playback is even just average, you'll find it more dynamic and bass heavy.  On the other hand, you should find your vinyl to have far more pleasing high-frequency reproduction and more detail and life to the music.  It's a trade-off.  When you dial in your vinyl finally right, it should sound a bit CD-like, yet retain some virtues that CD can never match.

It's just maddening getting to that point     

[Psychicanimal]

Do you have the Monolithic instructions?

http://www.monolithicsound.com/ps1.pdf

It's important that you become familiar with the dip switch settings.

Like Chair Guy said, it would be good to install the other cartridges and play around with the setting.  You'll learn how the parameters affect sound.

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