[robertwstephens]

Hello!  I have a Cornet2 and am building a Clarinet pre-amp.  I am trying to figure out what to do for an amp and whether 8 watts will drive my speakers to a decent volume.

1.  Can you compute what the output voltage of the Clarinet will be when I use my turntable?  I have a Denon DL103R that measures .28mV and am using the AU-300 10x step up with my Cornet II.

2.  I have Infinity speakers that have a sensitivity of 91dB at 2.83v@1M.  Is there anyway to calculate the efficiency?  Can I drive these to 100dB with an 8 watt amp?  Does the 15dB of gain from the Clarinet figure into this at all?

I love my Infinity's, but could give them up if I really had to.  Any input would be appreciated.  Peace.  Robert

[hagtech]

I forget, but I think for 10dB more sound you need 10dB more power (which needs 20dB more voltage), or 10W will get you to 101dB out of those speakers.  Or something like that.  But that is past the clipping point of an 8W amplifier.  You get no headroom.  Those are peaks.  Then again, it's pretty dang loud at that level.

The Denon at 0.28mV >> stepup-up = 2.8mV >> Cornet = 0.44V >> Clarinet = 2.5V.  That's enough to drive most amplifiers to clipping.  But this is for 5cm/s (or 4cm/s), which is a reference level.  You can often find peak levels 16dB above this.  So you have more than enough system gain.  I bet you rarely turn the dial past 12:00.

The limitation is power output, not gain.

jh

[robertwstephens]

Thanks for taking the time to reply!  That information helps.  Friends and family still can't believe the sound I am getting out of my modded Cornet 2.  There is ALWAYS a look of bewilderment on their faces that vinyl can sound that good.  Can't wait to get my Clarinet up and running!  Peace.  Robert

[amandarae]

Hello Robert,

The 103R's spec is 0.25 mV at 100 Hz.  Most cartridge are specified at 1000 Hz.  In the "real" world, the true output of the 103R is between 0.17 - 0.20 mV.

Regards,

Abe

[robertwstephens]

Hello!  Mine came with the test sheet for just my cartridge.  The left channel is .29mV and the right channel is .27mV.  I averaged the 2 in my question.  I am not sure why it would measure higher than standard.  It replaced a wood body Grado that I had a love/hate relationship with.  I buy lots of old vinyl for .50 each at a place down the street from my house.  The Grado sounded great on new vinyl and accentuated every scratch, tick and pop almost to a fault on used vinyl.  The DL103R does not have the sweet midrange of the Grado, but plays fairly quietly on even the most ravaged discs and has a very nice level of detail with the tweaked Cornet 2.  I am still loving your posted tweaks Amandarae with the caps on the Cornet 2!!!  It was like buying a new piece of equipment.  Peace.  Robert

[hagtech]

If you want the best out of those old cheap LPs, get a Dynavector XV-1.  It is unbelievable.  Somehow it turns the regular oldie into what sounds like the latest audiophile-grade virgin-mint vinyl.  Except, of course, that it costs more than your entire LP collection...

jh

[amandarae]

Hello!  Mine came with the test sheet for just my cartridge.  The left channel is .29mV and the right channel is .27mV.  I averaged the 2 in my question.  I am not sure why it would measure higher than standard.  It replaced a wood body Grado that I had a love/hate relationship with.  I buy lots of old vinyl for .50 each at a place down the street from my house.  The Grado sounded great on new vinyl and accentuated every scratch, tick and pop almost to a fault on used vinyl.  The DL103R does not have the sweet midrange of the Grado, but plays fairly quietly on even the most ravaged discs and has a very nice level of detail with the tweaked Cornet 2.  I am still loving your posted tweaks Amandarae with the caps on the Cornet 2!!!  It was like buying a new piece of equipment.  Peace.  Robert

So true!  Same here!

Yes, the Denon 103 series, at the moment, might not be as good in the midrange as the Grado.  Not because it is inferior to the Grado, I am not capable of arriving to such a conclusion, but because it takes a lot of experimenting to get the right sound of the 103R IME.  First, you have to have the right amount of gain so that you can load it starting at 14 Ohms.  From there you will have a great feel, as you move the load 10 ohms at a time, what the 103R can really do.  

I also have a Koetsu Rosewood Sugano (original!).  The Cornet 2 is a great match to it IMHO.

[robertwstephens]

OK Abe, now you have opened up a can of worms.  I have the Denon AU-300LC.  I believe it is a 10X step up.  Does that give me the "right" gain?  From there how do you load the cartridge?  Thanks for any advice.  I am new to some of these concepts, and definitely willing to experiment.  I have a DMM if that helps me any.  Peace.  Robert

[amandarae]

OK Abe, now you have opened up a can of worms.  I have the Denon AU-300LC.  I believe it is a 10X step up.  Does that give me the "right" gain?  From there how do you load the cartridge?  Thanks for any advice.  I am new to some of these concepts, and definitely willing to experiment.  I have a DMM if that helps me any.  Peace.  Robert

Robert,

According to my research, the spec of the AU-300LC is

gain = 20 dB (1:10)
Recommended Cart Z = 40
Natural impedance = 470 Ohms

I am pretty sure that since it was designed for the Denon carts in mind,  it should work well even if you load the cart at say 100 ohms.  The Denon 103R has a resistance of 14 ohms while the 103 has 40 Ohms.  So looking at the data, it seems that the optimal cart to use for the AU is the regular 103 if you want to load at the carts resistance as stated by the manufacturer.

It should be noted that it will work fine with the 103R too.  One thing to keep in mind is that once you load the cart equal to its rated resistance, the cart's output will be halve!  This is the important factor.  With the 103R at 0.25 mV (for example) loaded at 14 ohms, the output after the transformer to the preamp will only be 1.2 mV (0.12 mV x 10)!!  The phono preamp output (approx 157 times the input at 44 dB)will be 188 mV!!  Very small for the linestage input isn't it?
This is why the need of higher gain should be consider when loading it close or equal to the rated resistance.

With your current setting, the transformed impedance that your cart sees is at 470 ohms (47k/10x10).  To load it at 100 ohms you need to use 12.7k Ohms resistor connected in parallel to the secondary outputs (L and R) by using something like this


Of course, there are other ways to do it like soldering the resistor directly to the output of the SUT but I believe that this is the simpliest way to try it and see if you will find a specific loading value to your taste.  A good table to look at for calculating other resistor values is here http://www.bentaudio.com/parts/tx103loadhow.html  for your 1:10 loading scheme.

IME, you will find the 103R sound to change dramatically if you load it at 100 ohms compared to your current loading scheme at 470 ohms.  Your 1:10 SUT should be fine and you do not need more gain if you are going to load the cart at 100 ohms.   I am highly recommending it!

Try it, maybe you will like it.

regards,

Abe

[robertwstephens]

Wow!  Thanks for taking the time for the thorough reply.  I really appreciate it!  So if I have things figured out, I put one of these in line on each channel between the SUT and the Cornet2.  It looks like both wires of the resistor are connected to the positive on the male rca.  Where do you source the t's?  I will definitely try this and post my results.  Just when I think I have some of this crazy obsession figured out.......   Peace.  Robert

[hagtech]

Serendipity, as I just updated my cartridge loading page with a calculator for step-up resistor calculations.  It's at bottom of page...

www.hagtech.com/loading.html

This will help you guide your loading.  Unfortunately, it is a trial and error type thing, which requires a lot of critical listening across many LPs.  So it will take some time to dial in the best sounding value.

I solve this problem in my next phonostage design.  It will have adjustable loading you can change on the fly by remote control - as you listen.

jh

[PatOMalley]

What level Phono Preamp? Half-kit like the Cornet or high end like the Trumpet. I really want my next phono pre to be the Cornet but I would like to get the flexibility as well.

[amandarae]

Wow!  Thanks for taking the time for the thorough reply.  I really appreciate it!  So if I have things figured out, I put one of these in line on each channel between the SUT and the Cornet2.  It looks like both wires of the resistor are connected to the positive on the male rca.  Where do you source the t's?  I will definitely try this and post my results.  Just when I think I have some of this crazy obsession figured out.......   Peace.  Robert

You are welcome Robert!

No, one leg of the resistor connects to the + pin of the RCA plug, and of course the other to the "-".  You will then connect this to the secondary of the transformer (output).  So, looking at the tee, one end is where you plug the resistor (on RCA plug), the other end is the cable from the output of the transformer to the input of your phono preamp.

You can get the tees from RadioShack, Circuit City or Best Buy etc.  You do not need to buy fancy ones just for this purpose.  It makes more sense to get better resistors with 1 or 2 % tolerance once you figured out what loading values you like than spending a lot on fancy "tees" IMO because, you need the channel as balance as possible (resistor value) , the signal that will pass through this goes directly to ground anyway.

Check out what Jim posted in order to calculate loading values corresponding to your step up gain.  Very easy and as usual, very useful!

Regards

[amandarae]

Serendipity, as I just updated my cartridge loading page with a calculator for step-up resistor calculations.  It's at bottom of page...

www.hagtech.com/loading.html

This will help you guide your loading.  Unfortunately, it is a trial and error type thing, which requires a lot of critical listening across many LPs.  So it will take some time to dial in the best sounding value.

I solve this problem in my next phonostage design.  It will have adjustable loading you can change on the fly by remote control - as you listen.
jh

Uh oh!    Let me see, what can I sell on my current equipment at the moment..........

[analog97]

The more I learn about cartridge loading, the less I understand.  All I can tell you is I use a Denon 103/Au300lc into my Cornet2 and it sounds SUPERB.  I don't think I could ask for much more.  JH told me this loads the Denon 103 at about 500 ohms.  If I get curious, I might try that resistor scheme also.  Thank you for those detailed posts.  They make this doable.

[amandarae]

The more I learn about cartridge loading, the less I understand.  All I can tell you is I use a Denon 103/Au300lc into my Cornet2 and it sounds SUPERB.  I don't think I could ask for much more.  JH told me this loads the Denon 103 at about 500 ohms.  If I get curious, I might try that resistor scheme also.  Thank you for those detailed posts.  They make this doable.

470 ohms, ideally, is what you got when your SUT is configured at 1:10  (Transformed Z = 47k/(10 squared)).  

Do not worry, if that works for you, then stay with it and nevermind what others say about trying different loading values.  FWIW, I cannot discern any difference when loading my 103R at 470 ohms to 1k ohms to 47k.  Change occured to me as I go below 200 ohms down to the carts specified resistance (14 ohms).

cheers

[analog97]

Abe,

I like your "T" concept for experimenting with loading and I will try to get my regular Denon 103 down to 100 ohms from 470.  From what everyone seems to believe, i.e."hear", the BIG sound difference occurs low, <500 ohms just as you suggest.  There must be some obscure electrical principle operating, i.e. halving 400 ohms causes a larger difference than say halving 47K ohms. 

But, since I still don't quite understand the language here, is it a large inconvenience to ask you to post a picture of your transformer outputs showing  the tees and the RCA's going to the phono preamp?  It would be a great help to see this!! 

[robertwstephens]

Hello!  I went over to Rat Shack today and picked up parts to load my Denon 103R.  I bought a bag of 500 resistors with an assortment of values.  I put in a 12K resistor to get the load down to 96 ohms.  The highs became a little distorted.  I am curious if anyone has dialed in a value besides 100 or 470 ohms that they really like the sound of with the 103R?  This is an interesting experiment!  Peace.  Robert

[hagtech]

470 ohms, ideally

I used "500 ohms" because we don't live in an ideal world.  First order, you calculate the value to 470 ohms.  And that works for most people.  Sometimes I like to take it farther, and in audio it's a lot of the little things that can add up.

You see, the transformers always have series resistance in their windings.  The secondaries may be on the order of a hundred ohms or more.  It doesn't end up changing the calculation much, but the resistance on the primary does.  Depending on the tranny used, you can get another 20 ohms added to the reflected impedance.  Or more.  Maybe less.  That's why I round up to 500 ohms. 

The other reason is that many values in a circuit do not require 1% tolerances.  In fact, 20% is often good enough.  Loading is one of these.  You just have to get in the ballpark.  The difference between 500 ohms and 100 ohms will be quite noticeable.  But 400 ohms?  Probably not.

On the other hand.  One brand of 470 ohm resistor may sound a whole lot nicer than another brand of 470 ohm resistor.  So you have plenty of things to play with here.  In the end, it's your ears and personal judgement that decides.  It doesn't matter what the number is.  It doesn't matter what I think, either.  You only have to make yourself happy.  Oops, I didn't mean to get preachy here.  Just keep in mind that what works in one guy's system might not work for you.  It doesn't make you wrong.

What level Phono Preamp? Half-kit like the Cornet or high end like the Trumpet

More like a reference unit.  Not a kit.  Probably cost ten or twelve grand.

jh

[amandarae]

470 ohms, ideally

I used "500 ohms" because we don't live in an ideal world.  First order, you calculate the value to 470 ohms.  And that works for most people.  Sometimes I like to take it farther, and in audio it's a lot of the little things that can add up.

You see, the transformers always have series resistance in their windings.  The secondaries may be on the order of a hundred ohms or more.  It doesn't end up changing the calculation much, but the resistance on the primary does.  Depending on the tranny used, you can get another 20 ohms added to the reflected impedance.  Or more.  Maybe less.  That's why I round up to 500 ohms. 

The other reason is that many values in a circuit do not require 1% tolerances.  In fact, 20% is often good enough.  Loading is one of these.  You just have to get in the ballpark.  The difference between 500 ohms and 100 ohms will be quite noticeable.  But 400 ohms?  Probably not.

On the other hand.  One brand of 470 ohm resistor may sound a whole lot nicer than another brand of 470 ohm resistor.  So you have plenty of things to play with here.  In the end, it's your ears and personal judgement that decides.  It doesn't matter what the number is.  It doesn't matter what I think, either.  You only have to make yourself happy.  Oops, I didn't mean to get preachy here.  Just keep in mind that what works in one guy's system might not work for you.  It doesn't make you wrong.

What level Phono Preamp? Half-kit like the Cornet or high end like the Trumpet

More like a reference unit.  Not a kit.  Probably cost ten or twelve grand.

jh

There you go!  Im pretty sure this will clear out a lot of confusion.  Thanks for straighting them out for us Jim.

But, since I still don't quite understand the language here, is it a large inconvenience to ask you to post a picture of your transformer outputs showing  the tees and the RCA's going to the phono preamp?  It would be a great help to see this!!

 


Here's some pics.  Hope this will help you.



The first pic is the transformer (SUT).  Note the "IN"put and "OUT"put terminals.  The second one shows the tee connected to the output.  The other plug from the tee is where you connect the IC to your phono preamp for the Left and Right channels respectively.  The third pic shows whats inside the silver plugs connected to the tee.  It is the loading resistor with one end connected to + and the other end to - on the RCA plug.

Cheers

Hello!  I went over to Rat Shack today and picked up parts to load my Denon 103R.  I bought a bag of 500 resistors with an assortment of values.  I put in a 12K resistor to get the load down to 96 ohms.  The highs became a little distorted.  I am curious if anyone has dialed in a value besides 100 or 470 ohms that they really like the sound of with the 103R?  This is an interesting experiment!  Peace.  Robert

Hmmm...just like what Jim said, it is all system and taste dependent.  Although I do not understand why the highs becomes distorted at 100 ohms load.   In my experienced, I loaded the 103R at 14 ohms without a hint of distortion in my system.  Sounds different, yes compared to other loading values, but not distorted.   Try 150 or 300 maybe.

regards