Best Valve pre-amp match for ME 550 amp - Page 5 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th January 2013, 12:32 AM   #41
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
Quote:
Originally Posted by treuben View Post
Sound quality is not affected though the unit may be more susceptible to hum and noise if you have very high efficiency speakers. See if you can't get rage audio or Peter Stein to send you a diagram. They ought to have them somewhere. Or you can post a high res picture and we can point them out..
OK, Ill get back to you on that - thanks

In the meantime, what do you think of the 2 pre-amp designs I put links up for??
  Reply With Quote
Old 8th January 2013, 12:38 AM   #42
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
...something worth noting: I got this cheap buffer pre-amp eBay Australia: Buy new & used fashion, electronics & home d?r
...and put it between the pre-out and main-in connections of a NAD Surround T773, and it is sounding much more life-like, transparant, and like a stereo amp rather than a surround amp.

Worth buying I reckon. Music is much more 'present' in the room, although I did modify it, I took the volume pot out, and hard wired it on max. I resoldered every connection with Munforf silver solder. I does make quite a nice difference, esp. regarding a greater sense of detail and life-like transparancy....

Last edited by TigerScent; 8th January 2013 at 12:48 AM.
  Reply With Quote
Old 8th January 2013, 01:23 AM   #43
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by TigerScent View Post
Hey, thanks for that - that is what I figured. A tube-pre would be just the ticket.

Do you suggest I remove the resistors? Would sound quality be affected? (where are they lol )
You should not just remove the resistors. The ME550 was different to the ME750, ME850 and ME1400/1500 amps in that it was capable of bridged operation. As such, merely removing the resistors will not provide a suitable high input impedance for your needs. The amp needs to be completely re-configured for straight stereo operation, thus removing the possibility that it can be bridged. And yes, sound quality is affected slightly. The amp has been specifically designed for low input impedance operation. Any changes will alter sound quality somewhat.

Quote:
Originally Posted by TigerScent View Post

Or just find a very low impedance (ie: 400ohm) tube pre, such as this one: 12AU7 Balance Tube Valve Preamplifier Amplifier DIY Kit ref AR (No Tube) | eBay
No. Output impedance is still far too high. You should be searching for a maximum output impedance of around 10 Ohms. You could consider an ME preamp. They are superb performers, readily available and modestly priced. They exhibit a 2 Ohm (open loop) output impedance. Contact me via PM or email and I can assist you. I am in Sydney, if that helps.
  Reply With Quote
Old 8th January 2013, 01:38 AM   #44
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by treuben View Post
The me-550 had a pretty usual input topography - the unusual low input impedance was set with a couple of resistors plugged into small sockets on the boards inside. Some people just cut or lifted a leg to give a more normal 50k unbalanced input that most things can drive. He used to have an info sheet he sent out regarding that.. Peter Stein's pre's were as powerful as little headphone amps (I used to drive my High impedance Sennheisers with them pretty happily.) but an all ME system, while about as dynamic as it gets, can be short on tubey warmth and depth of soundstage and plain listenability. A tube pre can be just the ticket to make low volume listening more satisfying and flesh out the acoustic guitar and vocals. I'm surprised Mr Stein didn't tell you though perhaps, like a lot of good engineers, he's better at answering the question you actually asked and not the one you *wanted* to ask. 8) I like ME stuff.. nicely made and great dynamics - very accurate, a lot like later Krell or Spectral. The 850 was pretty special with Apogees.
No argument from me there.

Quote:
Originally Posted by treuben View Post

A lot of them (all models) blew up for various reasons though..
Oh really? Do tell? How many "blew up"? How many were sold?

The reality, I'm afraid, is somewhat more prosaic. ME power amps are about as reliable as any other high end, well designed power amp. Even better for consumers is that when a problem was uncovered, the manufacturer worked to eliminate that fault from any future amps. Thus, a consumer with a (say) 1988 version of the ME850 could have the 2006 enhancements fitted to his/her old amp. That includes the now notorious optical fan sensor.

Quote:
Originally Posted by treuben View Post

they're not the simplest of animals and I guess that can be bad news for durability.
Bollocks. The cooling system can appear complicated to the untrained, but, in fact, ensures a much longer life for all the components than more mundane cooling systems. For instance, the cooling system in the ME550/ME750/ME1400/ME1500 amplifiers, draws air past the main filter caps (thus keeping them cool), then past the output devices. Thermal feedback from the output stages, combined with the tacho sensor on the fan/s ensures that the output device temperatures is maintained at a fairly precise figure (around 55 degrees C +/- 5 degrees C). This keeps them in the lowest distortion part of their operating curve and keeps thermal stress at a minimum.
Quote:
Originally Posted by treuben View Post

Australia is also pretty harsh on high-bias power amps.. hell, it's not that habitable for humans a lot of the time!
True enough, but the ME uses demand responsive fans. As the amp heats up, the fans spin faster. Typically, on a 25 degree C day, the fans will be operating at around 200 ~ 300 RPM. Maximum RPM is around 2,000 RPM, so there is enormous cooling 'headroom'.
  Reply With Quote
Old 8th January 2013, 02:32 AM   #45
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by TigerScent View Post
OK, Ill get back to you on that - thanks

In the meantime, what do you think of the 2 pre-amp designs I put links up for??
Have you bothered trying an ME preamp? After all, that is what they are designed for. Re-inventing the wheel can be very tiring.
  Reply With Quote
Old 8th January 2013, 02:57 AM   #46
diyAudio Member
 
Join Date: Sep 2009
Location: Australia
Quote:
Originally Posted by Zaphod Beeblebrox View Post
Have you bothered trying an ME preamp?
ME preamp = best audio product I have owned. Honestly I'd be getting a ME pre, and if you wanted to change the sound look at the rest of your system. Anways.


Re: ME550-Mk1 ... I was advised that I could just disconnect one end of a resistor to increase the input Z (no other reconfiguration of the amp required).

I did this, and FWIW did notice a change in the sound.
  Reply With Quote
Old 8th January 2013, 03:01 AM   #47
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
Quote:
Originally Posted by Zaphod Beeblebrox View Post
Have you bothered trying an ME preamp? After all, that is what they are designed for. Re-inventing the wheel can be very tiring.
No; I havent come accross one yet in my travels. None so far in pawn shops...

...I would however, still want to have a tube pre-amp to try out how it would sound never-the-less...
  Reply With Quote
Old 8th January 2013, 03:02 AM   #48
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by TigerScent View Post
No; I havent come accross one yet in my travels. None so far in pawn shops...
How many would you like?

I have several to choose from.
  Reply With Quote
Old 8th January 2013, 03:10 AM   #49
diyAudio Member
 
Join Date: Mar 2006
Location: Australia
... with DIY its a work in progress..., and over time can end up with a rather good product; if you get better components etc: ie Ansar solid silver caps etc...

...I would like an ME though, at the right price...

...although I still want to work out a tube pre-amp solution: there must be a way to do it, and lower the impedance etc...

Last edited by TigerScent; 8th January 2013 at 03:37 AM.
  Reply With Quote
Old 8th January 2013, 03:54 AM   #50
diyAudio Member
 
Join Date: Feb 2010
Quote:
Originally Posted by TigerScent View Post
... with DIY its a work in progress..., and over time can end up with a rather good product; if you get better components etc: ie Ansar solid silver caps etc...

...I would like an ME though, at the right price...

...although I still want to work out a tube pre-amp solution: there must be a way to do it, and lower the impedance etc...
If you're trying to build a product as good as an ME preamp, good luck. You'll need several thousand transistors, in order to arrive at the right matching. The cost will far exceed the price of a new one. A good second hand one will cost you less than a good valve preamp kit. And you'll never manage the low impedance you need with a valve preamp, unless you resort to transformers. As for price, PM me and we can discuss.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best type of pre-amp for valve/tube power amp elgee Tubes / Valves 10 11th November 2011 10:40 AM
any advice on how to match a headphone level output to valve amp input levels? mondogenerator Headphone Systems 1 18th December 2009 03:08 AM
what guideline to match pre and amp? milen007 Tubes / Valves 5 2nd June 2008 05:58 AM
Valve Pre Amp & Class D Power Amp Puffin Tubes / Valves 7 16th June 2006 04:41 PM


New To Site? Need Help?

All times are GMT. The time now is 09:51 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2