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Old 11th December 2006, 09:14 PM   #1
amt is offline amt  United States
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Default Minimalist preamps - Morrison, Samuals??

Ive been looking at building a new preamp and came across the Morrison ELAD and Ray Samuals' CA-2. After reading reviews, it appears that people either hate them or love them. I believe they both use AD797 or similar and are fairly simple. I also found what looks to be a similar design on Rod Elliotts site (project 88).

So is the ELAD a good design and very transparent or not? And has anyone built something along the same lines, and if so, what was the general concensus?

amt
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Old 12th December 2006, 03:53 AM   #2
lineup is offline lineup  Sweden
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Rod Elliott project88
is a very good pre amplifier
.. as he tells in his instructions, you may use other op-amps than OPA2134

I know there are several topics in forum
where people show images of their Project 88 grand looking amplifiers!
And they love their preamp and its performance!

High Quality Audio Preamp


I have recommended this amplifier to members before.
Rod Elliott makes no bad amplifiers.

That man from Australia certainly knows what he is doing - when it comes to audio amps
===============================

diyaudio topics, with some Images! and informations about Project88

There are plenty of more, later topics
if you http://www.diyaudio.com/forums/search.php this forum
Search Keyword: project88

Pics of my preamp
Rod Eliot project 88 question

One diyaudio member Project88 construction, Attached:
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Old 12th December 2006, 05:01 PM   #3
Nordic is offline Nordic  South Africa
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I have PCB files for this project if you want...
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Old 12th December 2006, 05:33 PM   #4
amt is offline amt  United States
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lineup:
Yes, Ive read good things about the P88. Ive purchased several PCBs from Rod and know his website well. My main interest in this is whether the AD797 is a standout in performance and why it seems some people find the sound excellent and absolutely neutal and others dislike the it. Or is it a Gaincard thing: few parts and sorta high cost.

I also see that instead of one pair of opamps, these other designs use a pair per channel. If the extra gain isnt required, do the extra devices help the performance is some other way. This are already very low noise so whats the purpose?

Nordic:
Are you talking about the P88 or one of the other designs? If I build the p88, I will just purchase Rods boards. He has an awesome DIY resource there and I feel he can use the support. Now if its another design, I may be interested. Thanks for the offer.

amt
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Old 12th December 2006, 06:31 PM   #5
Nordic is offline Nordic  South Africa
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Nope, its for Rod's, worst case I would mail it to you, as I don't want to actualy post it here, best he gets all the support he can, such a great resource.
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Old 12th December 2006, 07:21 PM   #6
lineup is offline lineup  Sweden
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Quote:
Originally posted by amt
lineup:
whether the AD797 is a standout in performance and
- why it seems some people find the sound excellent and absolutely neutral and
- others dislike the it.
.............
these other designs use a pair per channel.
If the extra gain isn't required,
do the extra devices help the performance is some other way.
This are already very low noise so whats the purpose?
I am sure Nordic has got some PCB for Project88.


AD797 performance vs. listening impressions.
------------------------------------------------------------------
First, it is so easy to get false impression,
and those saying the one thing may have read what some says
and those saying other thing may have read the other group.

There are so many of all sorts of audio myths around
... and like one member told, or even had in his signature:
Once such a myth has begun to circulate - it is almost hopeless to kill it off.
Such myths, or conspire theories, most non-audio, are traveling this world constantly.

Especially when adding VERY hifi components - those that adds nothing to sounds = no distortion
it is so easy to start imagining things.
May also be the lack, the absence of some coloration, that was there before.

The high price of AD797 gives call for EXPECTATIONS - strong such.
A component with such BAD qualities for HIFI that you can here anything of it
I personally would not like to have in my pre amplifier sound chain
- where we still are at low line level voltage.


It is different for my LoudSpeakers
- them I want to be able to hear - and most of them will make sounds with different character.
That's what they are for, at last mine.

But my amps should be as faithful, fidel to deliver output=input signal, as possible.
In-Fidelity we may have heard of - but it ain't High Fidelity ... if this is what we are after.
But some do not care for HiFi, as long at it sounds good = pleases their ears.
It is the choice of them, in their own full right
- there are no laws or punishments for what we should like or not like.


AD797 is just one of those - that at least properly handle
would have almost zero distortion.
For myself I am not much bothered or concerned, if something sounds this or that
as long as distortion is a low as I can pay for.


One thing you should know, that AD797 may not be optimal for
the first gain stage of Project88 and probably not for second either.
If you go for OPA2134, the original choice of Rod .. in MKII version,
you probably come as close to hifi as possible
and the circuit would have near maximum fit for this very OPA2134 Op-Amp.
OPA2134 - SoundPlus™ High Performance Audio Operational Amplifiers


What is different for AD797 from for example OPA2134,
is that it performs best in an environment of fairly low resistors <= 2kohm.
( I have today read AD797 datasheet very closely and
made a discrete, 11 transistors, Clone of AD797 Circuit.
So I might know.
See my new topic:
AD797 Clone people! Who can make a better one. )


Click the image to open in full size.
Click the image to open in full size. Click the image to open in full size.

If I would build a real high class pre amplifier - with Attenuator, Volume Control,
I would do it same way.

amp - attenuator - amp

The first amp serves mainly as a buffer, towards different sources.
The last amp serves also as buffer, towards different loads.
(this is the terms we use:
source = input signal device which can be of many different kinds, with many different qualities
load = output device, into what we send the signal, also can be different, be 'difficult or easy' load)

This makes whatever (almost) you attach to input/output of this amplifier Project88,
it will not be able to effect the quality of operation.
Some other, one Op-Amp stage pre amplifiers,
would often be able change the frequency roll-off,
sometimes even at both high and low end of audio spectrum,
depending on the position of your volume control attenuator.



hope this answer most of your wonderings
i am confident i have done my best to answer in a good way

Much regards to you, amt
who had good sense in asking the right, the good questions
that out of my own interest made me author a fairly good reply


thinks
lineup
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Old 12th December 2006, 08:04 PM   #7
Nordic is offline Nordic  South Africa
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I'm certainly giving these a shot as we speak, just took the boards out of etchant.... I think maybe OPA2227 for the second gain chip, and opa2132 for the first, as the circuit has 100k input impedance, 2228 would probably also work for the first IC as long as you use gain > 0 where the previous stage has very low output impedance
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Old 12th December 2006, 08:49 PM   #8
lineup is offline lineup  Sweden
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Quote:
Originally posted by Nordic
I'm certainly giving these a shot as we speak, just took the boards out of etchant....
I think maybe OPA2227 for the second gain chip,
and opa2132 for the first, as the circuit has 100k input impedance,

2228 would probably also work for the first IC as long as you use gain > 0
where the previous stage has very low output impedance

Yes, Nordic.
I think it would work great.

---------------------------------------------------------------------

1.) The first we should think of - is using good Op-amps.
And I do not mean just good - there are plenty of extremely 'good' op around,
that simply is not fit for audio frequencies.

As they were optimized for video and very high frequency operation
and sometimes also optimized for other things - like settling time
- capacitive loads - high output current.
When optimizing for one thing, this means most often you sacrifice or compromise other things.

So, if an op-amp is told in datasheet, to be used for audio apps
or even professional audio applications
- this is not something we should ignore so easily, as some seems to do.


And if first at the top of applications list, even in headline!, it says very fast or video
we should know it is NOT optimized and intended mainly for good audio operation.
It is true, if we know how to handle such chips, we may be able to tweak the chip, a little bit - but only little,
from the outside pins.
But it wont change the main character and qualities of the chip- as it was put together and trimmed and compensated.

Those you mention Nordic are all, as far as I know,
told they can be used for good audio.
-----------------------------------------------------------------

2.) The second to think about, as you mention too,
is the impedances the chip likes to have around its pins.
But this is not as critical as many like to think.
And even they are afraid for this, I have seen!
I have some courage - I think .....
I ain't the very easily scared one, when comes to audio.


My rule of the thumb, after seeing some comparing diagrams
of commonly used JFET input contra BJT input transistor op-amps,
is that at 10-47 kohm, we could use either for same noise results.
Lower than 4.7 kohm or lower we go for a low noise BJT input OP
and for 100 kohm or higher we go for JFET input OP.

This is for theoretical best results.
Now NE5534 which is typical and old BJT input chip
with acknowledged very good performance (considerably better than NE5532 which is another circuit! in fact)
has been used in many audio circuits with high impedance resistors at input.
And it still wont stop NE5534 from perform very well.

And NE5534 has not a low bias input current.
Like 0.2-0.5 uA, if I remember correctly.
Theoretically this current should create current noise in those higher value resistors
but when summing up the performance in s practical application,
it wont hurt to much at all.
NE5534 even may beat up some other Op-Amps with only input bias that is maybe 1/1000 of 0.2uA.


So you just go for using those nice Burr-Brown you mention, Nordic.
Rod Elliott has no way use any extreme resistor values in this project.
In fact, on the contrary, they are all very typical and optimal values
for audio line level resistors.
And for best audio operation.
-----------------------------------------------------------------------------

3.)
My firm opinion here:
-- You can't go much wrong from a very good result
-- whatever Audio Operational Amplifier you use, in ESP Project88.
-- Trust me!
( if you think I can be trusted, somewhat )




Regards
form very north - to very south
lineup
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Old 12th December 2006, 09:41 PM   #9
Nordic is offline Nordic  South Africa
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OK, just need some pots and a little PSU, got a tiny PCB mount trafo that can do 2 x 12V at about 100mA at max load before rectification... hope its enough, till I can make better plans...
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Old 12th December 2006, 09:45 PM   #10
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Default Re: Minimalist preamps - Morrison, Samuals??

Quote:
Originally posted by amt
Ive been looking at building a new preamp and came across the Morrison ELAD and Ray Samuals' CA-2. After reading reviews, it appears that people either hate them or love them. I believe they both use AD797 or similar and are fairly simple. I also found what looks to be a similar design on Rod Elliotts site (project 88).

So is the ELAD a good design and very transparent or not? And has anyone built something along the same lines, and if so, what was the general concensus?

amt

These preamps seem minimalist mostly as far as their sound is concerned. They're certanly easy to build but don't expect them to blow your socks off.

How transparent can the Elad be if the designer guarantees is to mask all cable differences? Pathetic texbook opamp ****.
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