Best Valve pre-amp match for ME 550 amp

[TigerScent]

Hi, I am looking for a hi Q valve pre-amp kit/plans that would have an <10 ohm (preferably) or up to 100 ohm output impedance, ... to match a ME 550 amp.
The ME 550 has a balanced input of 2 ohms, and unbalanced 1000 ohms.

...any suggestions??

[ChrisA]

Originally Posted by TigerScent

The ME 550 has a balanced input of 2 ohms, and unbalanced 1000 ohms.

I looked up the specs an found a very different answer. What I found was a very conventional 100K input impedance. But then there might be more than one amp called "ME 550" Do you have a link to this amp's specs?


That said if you ever have the open to use balanced inputs, then use the balanced inputs.

If building with tubes you really are going to need a transformer to get such low impedance and I seriously doubt anyone would be selling a kit with such uncommon specs. Check the specs again 2 ohm balanced seems wrong and so does 1000 ohms

[TigerScent]

Originally Posted by ChrisA

I looked up the specs an found a very different answer. What I found was a very conventional 100K input impedance. But then there might be more than one amp called "ME 550" Do you have a link to this amp's specs?


That said if you ever have the open to use balanced inputs, then use the balanced inputs.

If building with tubes you really are going to need a transformer to get such low impedance and I seriously doubt anyone would be selling a kit with such uncommon specs. Check the specs again 2 ohm balanced seems wrong and so does 1000 ohms

...yes, I emailed the designer/producer of the ME amps, Peter Stein, who gave me that information.

Part of email reply...

"In standard configuration the ME 500 has a 2Kohm balanced input (or 1K unbalanced)..... Output impedance would need to be 100 ohms or lower (all good solid state high end preamps can do this easily) ...It is always good engineering practice to have at least 10 times lower driving impedance for Audio. 100 times is better."

I think he meant 2ohm balanced and 1K unbalanced....

the model is a ME 550 Type I

[kevinkr]

No, a 2K balanced input makes sense, particularly in conjunction with a 1K unbalanced input.. No one makes a balanced input of 2 ohms - driving it would require more power than most solid state pre-amps are capable of.

If you want to drive this thing with a tube pre-amp a design using a 600 ohm line transformer or White cathode follower output would be good choices. The octal version of the Aikido using a 6BX7 as the output tube with large output coupling caps probably work.

[TigerScent]

Originally Posted by kevinkr

No, a 2K balanced input makes sense, particularly in conjunction with a 1K unbalanced input.. No one makes a balanced input of 2 ohms - driving it would require more power than most solid state pre-amps are capable of.

If you want to drive this thing with a tube pre-amp a design using a 600 ohm line transformer or White cathode follower output would be good choices. The octal version of the Aikido using a 6BX7 as the output tube with large output coupling caps probably work.

...my apologies, the info I got was for a ME 500, not a ME 550, Peter Stein responded in a subsequent email, where I informed him I initially thought it was a 500, that the ME550 had an input impedance of 1000 ohm

[ChrisA]

Originally Posted by TigerScent

...yes, I emailed the designer/producer of the ME amps, Peter Stein, who gave me that information.

Part of email reply...

"In standard configuration the ME 500 has a 2Kohm balanced input (or 1K unbalanced)..... Output impedance would need to be 100 ohms or lower (all good solid state high end preamps can do this easily) ...It is always good engineering practice to have at least 10 times lower driving impedance for Audio. 100 times is better."

I think he meant 2ohm balanced and 1K unbalanced....

the model is a ME 550 Type I

No, he meant 2K balanced and if you use only one of the two sides you have 1K unbalanced.

You want to use the balanced input. the way to get there with a tube amp is with a transformer. Yes you might use cathode followers or whatever. But that just adds more tubes. Transformers are noiseless and provide perfect galvanic isolation. and the transformer will have perfect balance too.

What you would be building is a very low powered stereo amplifier. You will not find kits or plans for this. It will be a design exercise. Likely take some Spice simulation and bread boarding. Not rocket science as it need not be complex.

The simplest approach is just to go single ended class A. Use something like a parallels 12AU7 or 6sn7 as an output tube.

[TigerScent]

Originally Posted by ChrisA

No, he meant 2K balanced and if you use only one of the two sides you have 1K unbalanced.

" In a follow up email, he stated: "I also mentioned a 2 K ohm input impedance but as I now understand this is irrelevant as you have an ME 550 and not an ME 500 - the input impedance in standard form is 1K ohm or 1000 ohms. To get good performance from any preamplifier connected to a standard ME 550 I would suggest an output impedance (from the preamplifier) of 100 ohms or less."

...are there any hi-Q DIY plans I can use as a base plan and modify to suit, that you know of...Im entirely new to all this, but have modified some output caps on some NAD's with Nichicon Muse etc, with noticable improvement in clarity - definition - musicality ?

[cjcc67]

Start with Kevins suggestion of the octal version of the Aikido. It's well regarded and documented.

[Zaphod Beeblebrox]

Originally Posted by cjcc67

Start with Kevins suggestion of the octal version of the Aikido. It's well regarded and documented.

Curious suggestion. How much experience have you had with the ME550, when connected to a valve preamp?

Are you suggesting that the ME550 owner should trust the opinions of someone who has no experience with the combination?

Perhaps the ME550 owner should consult someone who actually knows the capabilities and limitations of the combination.

[kevinkr]

Originally Posted by Zaphod Beeblebrox

Curious suggestion. How much experience have you had with the ME550, when connected to a valve preamp?

Are you suggesting that the ME550 owner should trust the opinions of someone who has no experience with the combination?

Perhaps the ME550 owner should consult someone who actually knows the capabilities and limitations of the combination.

Interesting, any reason you would have an axe to grind with me? In what past life have I transgressed against you?