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Old 13th February 2007, 05:39 PM   #1
daly41k is offline daly41k  United States
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Default Pass Tharagard A75 vs Pass Aleph 1.2's

I just wanted to share and interesting listening experience. I recently bought a DEQX unit so I could bi amp my speakers using a digital crossover, calibrate and correct the speakers phase and frequency response and do room correction.

Because my mono Aleph's 1.2 -2kva xformers buzz; for the testing while still using the passive 24db crossover at 2600hz, I replaced the Alephs with my 14 year old Pass/Tharagard A-75 stereo amp (dual mono ps).

After calibrating the speakers and doing room correction the sound from the speakers in all audiophile catagories was in your face improved (I was using a borbely balanced line amp before the DEQX). The DEQX converts everything to 96khz sample rates.
After executing the speaker and room correction I sat back for a listen using politically acceptable music. I have not done the biamping yet.

The interesting thing was that using the A-75, the images were very distinct and well placed. It is if the singer was in the room.
Depth was excellent and the tonal balances were like live. Even the Sax took on a 90%lifelike tone.

I then substitued the Aleph's, it was like blowing up a ballon bigger. Things were not as defined but I could hear instruments way off to the side and stage was immense. But the one thing that did stand out the most is what I call the echo affect on recordings where reverb has been added or it was a natural condition of the recording site. The Aleph's picked this up to a greater degree. The bass on the A-75 was still better. I don't have an explanation for such a noticeable difference in sound except that the circuits and their application are so different. It could be that the regulators in the A-75 account for the better focus and that amp has a j-fet input (I am going on memory).

I am also using a choke PS on the Aleph's PS and this may cause the increased image size?

I am hoping that the AX100 which is being planned (I am gathering parts) can do both. I have put the Aleph's on 4 wheel dollies since they must weigh over 100lbs each. The A-75 isn't light either. Just sharing--dave--I used to be daly21k but now I am daly41k.
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Old 13th February 2007, 09:10 PM   #2
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Assuming that your A-75 is built stock, the inputs are MOSFETs, albeit a different part than the one used in the front end of the Alephs.
As far as imaging goes, things are more murky. I've always regarded imaging as a phase-related phenomenon. There's clearly also a detail-retrieval aspect, because the echo off the back of a stage is many dB down from the main signal. People argue over whether bigger is better or smaller and more focused is more realistic. My response is that it depends. Something like a bass drum has a diffuse image no matter what. A castinet has a pretty precise image--or should.
The more amplification stages the music goes through, the more generic the image becomes. It gets diffuse. Sure, you can say that the musician is "over there" while vaguely waving a hand in the direction of one speaker or the other...and in fact many people are quite content with this sort of sound, but it can and should be better.
Feedback figures into the game, also. The more negative feedback you use, the tighter and smaller the image gets. Some people feel that this is the way things ought to be and use it as an argument for lots of feedback. I disagree. All it takes is listening to live, unamplified music to see that something is amiss. Most real-life images aren't that small or tightly defined. So clearly something is wrong. My take is that the more subtle interactions between the instrument and its immediate surroundings get obliterated by phase shifts in the feedback loop. Things like, let's say, the wall six feet to the left of the player are lost. In real life, that wall tends to bloat the perceived size of the image by providing a very fast reflection for the soundwaves. To drop that information is not an accurate representation of how that image actually sounded.
All of this is a round-about way of saying look at the number of devices and the amount of feedback in the two amps. You may find your answer there.
I've been experimenting with lower and lower feedback over the past two or three years. The results are very encouraging. Clearly, low feedback or no feedback designs can get loose in the bass if the woofer needs a lot of control, but otherwise, the sound has improved.

Grey
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Old 14th February 2007, 02:48 PM   #3
daly41k is offline daly41k  United States
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Default A75 vs Aleph 1.2

Grey, thanks for the feedback. I usually have never noticed big differences with amps because other devices had bigger impact in my set up. I have used mostly tube pre-amps that I have built from scratch or from established designs. The AR sp10, Borbely balanced line, some designs using miniature tubes, the Borbely tube hybrid phono stage and lastly the borbely SS phono stage to use with low output MC's.

I finally broke down and bought this DEQX unit becasue it offered speaker correction, room correction, and I could experiment with digital crossovers and bi-amping. It was after using this device that the difference in the amps became noticeable.

I like both the A75 and Aleph, and I want to build the AX100. I am hoping to reach audio Nirvana with this investment. Reading through the threads there is very little information on comparison of this design with other Pass designs or other designers.

I have also built my share of OTL's and I have moved away from tubes as amps. The high voltage scares me and I think that the mosfet designs have really improved.

I did own a McIntosh 402 for awhile and I really liked the safety controls in the design but it did not sound better than the Aleph's but it's transformer didn't buzz either. It was a fully balanced design with heavy feedback to get virtually no distortion.

I also have a Marsh A400 that I use for AV in my living room. It is an class AB stereo rig. Not bad, very quiet and good for TV.

Maybe Nelson is going to update his AX.5 series to a Jfet input and put us all back to work next winter.

dave
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Old 14th February 2007, 03:54 PM   #4
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Hi,

I did compare my Aleph 5 clone to my Aleph-X. It starts around here:
One Aleph-X working, One to go

to make it short it does give you tighter bass combined with the Aleph highs.
Displaying room echos is one of the things a combination of A-X (or Aleph) and X-BOSOZ does really outstanding and greatest was one of the greatest changes these components made.

William
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Old 14th February 2007, 06:18 PM   #5
daly41k is offline daly41k  United States
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Default A75 vs Aleph 1.2

William thanks, I appreciate the feedback. I like the Borbely designs as well. www.borbelyaudio.com as he uses all J-fets in his designs with mosfet outputs in Class A. I was thinking of building both the AX 100 and the Borbely 80watt class A and use both in a biamp situation. I like the borbely in my set up for the tweeters since it has a servo amp to regulate dc offset from the driver board which would help protect the tweeters.

I would use the AX 100 for the mids and bass. Anyway that is my thinking for now. dave
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Old 16th February 2007, 09:31 PM   #6
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Its very subjective to the point certain recordings will sound better on either amp.

I previously compared the stock A100 (different to the A75..same designer) to the Aleph 2 and it was interesting.

The Aleph was more engaging and romantic with a special natural quality and very clean in the mids.

The A100 was more cut and dried, tight bass and possibly not the resolving power of the Aleph.

The AX versions offer is different kind of excitment.

They are more an energy driven presentation where was the SE Aleph is more lusteful and softer, perhaps misty in some ways.

The new X0.5 amps are different again, quite spectacular actually. The ultimate in transparency and dynamics with a dab of peanut butter and chocolate.

I would try an Aleph J (diy)and see how you go.

Macka
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Old 16th February 2007, 09:45 PM   #7
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Default Re: A75 vs Aleph 1.2

Quote:
Originally posted by daly41k

Maybe Nelson is going to update his AX.5 series to a Jfet input and put us all back to work next winter.

dave

As far as I know, the .5 circuits already have JFETs in the inputs.

Grey
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Old 18th February 2007, 03:10 PM   #8
daly41k is offline daly41k  United States
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Default A75 vs Aleph 1.2

To Grey-your comment about the .5's having jfet inputs just goes to show us that when compared to NP we are a day late and a dollar short!!! I like the borbely j-fet designs as well. Those circuits would have to be bridged to get the push pull effect of the AX designs. dave
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