Best Valve pre-amp match for ME 550 amp - Page 7 - diyAudio
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Old 10th January 2013, 12:31 AM   #61
treuben is offline treuben  Australia
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I found Mr Stein helpful also btw. Nice, amiable chap with a sharp mind too.
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Old 10th January 2013, 12:39 AM   #62
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I found Mr Stein helpful also btw. Nice, amiable chap with a sharp mind too.
Yes, he also volunteered information that was quite helpful (apart from what I asked for)...,

....and sent photocopies and links etc..., something about switching 180 degree phases esp. with regards to cartridges on TT's, etc...

Last edited by TigerScent; 10th January 2013 at 12:49 AM.
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Old 10th January 2013, 12:47 AM   #63
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Originally Posted by TigerScent View Post
No idea. There is no schematic supplied.

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Originally Posted by TigerScent View Post

...also, what are the steps in transformer coupling with regards to the JP200
The transformer is the easy part. Connect it to the output. You will also need to alter the gain of the preamp to compensate. This will alter the sound of the preamp.

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Originally Posted by TigerScent View Post

...and what mods would you suggest to help with the loop feedback?
I wouldn't. The preamp is designed to incorporate global NFB. Removing it would be difficult and time-consuming for someone (else) to work out.

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(As I do this in stages, Its more affordable, and I end up using better components)

Once I build this, I still would like to try the ME preamp:installments work well with me ...
You should try the ME preamp FIRST, not last. The ME preamp is as good as the best valve preamps available and far better than cheap crap. And by the best I mean products like the Conrad Johnson Premier 16, et al.
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Old 10th January 2013, 12:53 AM   #64
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Originally Posted by Zaphod Beeblebrox View Post
No idea. There is no schematic supplied.



The transformer is the easy part. Connect it to the output. You will also need to alter the gain of the preamp to compensate. This will alter the sound of the preamp.
Can you elaborate a bit on how to do this?

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Originally Posted by Zaphod Beeblebrox View Post

I wouldn't. The preamp is designed to incorporate global NFB. Removing it would be difficult and time-consuming for someone (else) to work out.
how is global NFB in the preamp going to affect the ME 550 sound quality typically?

Quote:
Originally Posted by Zaphod Beeblebrox View Post

You should try the ME preamp FIRST, not last. The ME preamp is as good as the best valve preamps available and far better than cheap crap. And by the best I mean products like the Conrad Johnson Premier 16, et al.
Which ME preamp would you suggest as a best performance/value match for the 550, which includes a phono stage?

Last edited by TigerScent; 10th January 2013 at 01:00 AM.
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Old 10th January 2013, 12:59 AM   #65
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Originally Posted by treuben View Post
They were well designed products and sounded special - especially with low impedance brute speakers like Apogee, Thiel, Duntech, Ambience etc lots of control and dynamics where others amps could sound kinda muted and flat. Mr Stein is an accomplished designer certainly and the temperature thing does make a difference to dynamics and linearity. The ME15 isn't too expensive s/h. I see units go for 400-600 on ebay pretty regularly and the 25 for 800 or so with the phono stage. You can pay more for the latest "upgrades". Details of what exactly (components please if anyone knows enough to talk about them) they are might be would be nice else it's tricky to know what you're paying for of course.
Fair question. Here are the differences between the old and new ME preamps:

Old:
Power Transformer: 4VA, EI core type.
2,000uF in external power supply box.
Total of 6,000uF capacitance on internal power supply PCB.
Regulation provided by LM340T15, with series pass transistor for -ve rail.

New:
Power transformer: 40VA, 'R' core type.
20,000uF in external power supply box.
23,000uF on internal power supply PCB.
Pre-regulation and capacitance multiplication, via series pass transistors.
Line level regulation via LM317T/LM337T devices.
Phono regulation via LM317T/LM337T devices.
Muting on board.
Provision for remote control if required.


All alterations are centred on power supply and regulation.

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Originally Posted by treuben View Post

The 15 is nice enough (same line board) if you don't need two tape loops and phono. They (the pre's) also make a nifty headphone amp if you have high impedance (>300ohm) cans - with a very similar sonic signature to the power amps - dynamic and open and clear. A possible config might be source>tube buffer>me pre>me power to give you some tubey goodness. My unit also got a slight power hum when it was converted to high impedance operation (in only one channel) so be aware of that if you have silly efficient lowthers or something..unless you like humming..
It's more likely something else was wrong. Converting to high input impedance has never, IME, ever led to more noise (though there will be a VERY slight increase in theoretical noise performance - in reality, the difference will be academic).
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Old 10th January 2013, 01:02 AM   #66
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Originally Posted by TigerScent View Post
Can you elaborate a bit on how to do this?
Connect one pair of terminals of the primary of the transformer to the output and earth of the preamp. Take the secondary connections to the power amp.

Quote:
Originally Posted by TigerScent View Post


Which ME preamp would you suggest as a best performance/value match for the 550, which includes a phono stage?
An ME15 or ME25 will suffice. The ME15 is less expensive but far less commonly available. Both are sonically identical. If you are in/near Sydney, I will be happy to loan you an ME preamp. If you are outside the Sydney area, then I will post one to you for evaluation. You pay freight both ways.
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Old 10th January 2013, 01:10 AM   #67
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Originally Posted by Zaphod Beeblebrox View Post

I wouldn't. The preamp is designed to incorporate global NFB. Removing it would be difficult and time-consuming for someone (else) to work out.
how is global NFB in the preamp going to affect the ME 550 sound quality typically?
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Old 10th January 2013, 01:14 AM   #68
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Originally Posted by TigerScent View Post
how is global NFB in the preamp going to affect the ME 550 sound quality typically?
Placing an inferior product in series with your ME550 will destroy much of the niceness that your ME550 does. Products that use global NFB are inferior. Part of what makes (some) valve amps and preamps sound good, is the fact that they do not use GNFB.
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Old 10th January 2013, 01:15 AM   #69
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Originally Posted by Zaphod Beeblebrox View Post
Connect one pair of terminals of the primary of the transformer to the output and earth of the preamp. Take the secondary connections to the power amp.
So the Primary of the transformer used in the preamp; has one pair of terminals connected to the preamp - while the secondary connections go to 'where' in the power amp?

(I assume they are also connected to the preamp : as well as wherever (please specify) on the 550 right?)
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Old 10th January 2013, 01:21 AM   #70
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Originally Posted by TigerScent View Post
So the Primary of the transformer used in the preamp; has one pair of terminals connected to the preamp - while the secondary connections go to 'where' in the power amp?

(I assume they are also connected to the preamp : as well as wherever (please specify) on the 550 right?)
The secondary windings are connected to the input of the ME550.
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