Grado Statement with Mu

Jimvette · « **on:** 15 Feb 2006, 03:58 pm »

Has anyone tried a step-up transfromer, Mu or other, with a low output Grado cartridge.

John Chapman · « **Reply #1 on:** 15 Feb 2006, 05:09 pm »

Hello!

I have not tried a Grado myself but if you can let me know just what cart you have and your phono stage details, etc then I can let you know if it looks like a step-up would be needed and if it'd be a good fit.

Thansk!

John Chapman
www.bentaudio.com

Jimvette · « **Reply #2 on:** 15 Feb 2006, 06:09 pm »

Currently I am using a Grado Reference Sonata (4.5mv) with an EAR 834P phono stage. I would like to upgrade to a Grado Statement Reference (.5mv). They both are specked for a 47k load. I have changed the tubes in the EAR to V1 - 5751, V2 - 12Ax7 and V3 - 12AU7. Thes tubes greatly improve tonality, slightly increase hum and slightly reduces gain.

My plan would be to first try the Mu with Refernce Sonata (4.5mv) then purchase the Statement Refernce (.5mv)

John Chapman · « **Reply #3 on:** 15 Feb 2006, 08:01 pm »

Hello!

Couple thoughts. First with the 4.5mV cart you would not want a step-up in-line. The output to the phono stage would be too high and second a high output cart's output impedance tends to be high as well and would not suit a step-up. If you have enough gain with the Sonata / EAR combo then you are good to go. How is the gain now?

With the Statement you'll need more gain and a step-up might be the way to get it. Any step-up in the signal path will lower the load that your cartridge 'sees'. Although the Sonata and the Statement both show a spec of a 47K load if you look at the resistance number they are VERY different animals.

The Sonata shows a 475 ohm output impedance - NOT usable with a step-up - but with that high 4.5mV output a step-up is not likely needed anyway.

The statement has a 2 ohm output impedance spec - Very low and ideal for a step-up. The Statement should be fine into a lower load than 47K. A 1:10 step-up ratio would have it 'seeing' a 470 Ohm load and then by playing with load resistors you can load down from that point. There is no way to load up from the impedance the cart see's via he step-up ratio (at least not without ripping open the phono stage and modding it's input resistance. )

These guidelines are just the way the math works with step-up transformers. Any transformer of a particular ratio will 'translate' the load in this same way. Typically this works just fine. As diffent cartridges outputs get lower their output impedances tend to also get lower - meaning they are better at driving a step-up. Basically the more the cartridge needs gain the more it is capable of driving the step-up. One of the few examples of a free lunch. There are a few exceptions to this - the lower output denon's don't have low enough output impedances to drive high ratio step-ups - but are fine with lower ratio's like 1:10. Many moving coil carts are happy at loads of 200 ohms and lower so this loading change the step-up causes tends to put you in a nice range for loading as well.

Summary:

1- Hopefully you have enough gain in your system with the Sonata.!

2- If you go to the statement it should be o.k. to use a step-up in-line to get the gain you'll need. If for some reason the cart is much happier at 47K load (specs don't show it would have a problem lower but contact Grado to confirm) then the ONLY practical way to get that load to the cart is to get a high gain phono stage that does not employ a step-up. Be a bit careful with this since a lot of MM / MC phono stages have a step-up inside for the MC input and it will affect loading the same way.

I have likely made it sound more complex than it is! As mentioned above the gain vs. loading tends to work out naturally and it is hard to find exceptions that don't work out.

Many Thansk!

John

Jimvette · « **Reply #4 on:** 17 Feb 2006, 01:39 am »

John,

Thank you for the valuable information. I am, however, experiencing something unexpected. I have changed the V3 tube from a 12AU7 to a 5751, whilch further lowers the output of the EAR phono stage. The Reference Sonata seems to work a little better with the EAR's built in transformer switched in - blacker backround, more dynamic. There does not seem to be a problem with overload. According to posts I have come accross elseware, the EAR is not known for having a great built in transformer. I think the imput is set at 10 - 50 Ohms and is not user adjustable. It seems that a much better transformer set at 470 Ohms would work even better. Does this make any sence.

Jim

John Chapman · « **Reply #5 on:** 17 Feb 2006, 04:20 am »

Hello!

The EAR's internal trannie can only be so good - that phono stage is a great unit at it's price but to sell it at that price they can only afford to spend a modest amount on any one part. I think that the internal transformer in the EAR is 1:10 ratio which would give a load to the cartridge of 470 ohms - just like any other 1:10 ratio step-up would. That is if the 47K ohm input resistor is still in place. I have seen a couple EAR's that have been modded to set loading and that resistor was replaced with a much lower value - not taking into account the affect of the step-up on loading. If you want a 100 ohm load you want a 10K restistance after the step-up not a 100 ohm resistor as I have seen done......

Thinking about it one reason you do not get a huge leap in gain going with the Sonata / step-up is that the cartridges high internal impedance (475 ohms) acts as a voltage divider that eats away some of the output signal from the cartridge. This combined with the lower gain with the tube swap puts all the gain's back about where they are working.

You've tested by hooking it up this way that is seems to work for you. Despite the math saying it's not ideal if it works then it works! You are the second person I have talked to this week who mentioned using an MM cartridge with a step-up with decent results!

Personally I would not go to the trouble of adding the MU step-up unless you are swapping cartridges to a low output moving coil unit. Get the cart you are shooting for first (run it via the little internal step-up - it should sound good like that!) then after play with a step-up upgrade and adjust loading, etc.....

Thansk!

John

Jimvette · « **Reply #6 on:** 18 Feb 2006, 03:19 am »

Thank you again for your advice.

I did, however, try the internal EAR transformer with a second MI cartridge. This one is an old Signiture series Grado with a new stylus. In some ways this is a supperior to the Sonata. Warmer, fuller, more extended at the top. Again, there is a gain in performance when the transformer is switched in. With this cartridge, unlike with the Sonata, there is a slight roll-off in the high frequencies. Not with standing the math, I think I may be on to something here. Do you think that a transformer with a 470 Ohm input would reduce this roll-off. Did the other individual with a MM cartrildge you mentioned also find an improvement with the transformer. What inpedance was used there.

Regards, Jim

John Chapman · « **Reply #7 on:** 18 Feb 2006, 07:54 pm »

Hello!

The 470 ohm output impedance of the Sonata feeding a complex impedance (like a step-up or cables, etc) should roll off earlier than a low output impedance cart like the reference based strickly on the math. With phono front ends there are so may variables that it is hard to 'calculate' what might happen with many combo's......

In general when you go too low on the cartridge loading you get a HF rolloff. Do you have the stock 47K resistor still in the EAR?

I just called the fellow I spoke to last week. Turns out it is a high output MC type he was using - a Sumiko Blue Point Special No 2. It has a 2.5mV output and I suspect a highish output impedance - since that is how these things tend to work out. I can't find a spec for it's internal impedance so I kinda got stuck trying to figure if the same factors were at work in his case. He uses a lowish gain phono stage as well so it works out fine for him gain wise as well.

Thansk!

John

Jimvette · « **Reply #8 on:** 18 Feb 2006, 08:03 pm »

Other than the tubes, the EAR is completly stock.

John Chapman · « **Reply #9 on:** 18 Feb 2006, 08:12 pm »

Hello!

If the internal trannie is the 1:10 ratio as I think it is then the 'calculated loading' would be 470 ohms with it engaged - just like it would with the tx103. As a side note sometimes when you make a change like a cart you may need to reset up the table setup to tweek sonics. If you don't optimize with each change then you really can't say what works best. It's a bit of a pet peeve of mine - folks sometimes plunk gear into a system (worst case of this is these 'shootout events') then decide quickly which is 'best'..... end of rant....

If you still have the other cart to play with you may want to give it another go. Don't try too hard to like it though! It may be for your system the Sonata cart fits better via the internal step-up and maybe that combo is the trick.

Thanks!

John