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PostPosted: Tue Aug 30, 2016 8:15 am 
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Audiomat Owner’s Resource

Over the last couple of months I have scoured the internet to find everything I could about Audiomat amplifiers, their design specs, and how to run them to achieve top performance. As many of you know, there is not a lot out there, a few crumbs here and there and a few forum comments from folks who have owned them. This thread will hopefully act as a place to deposit knowledge and experience on all Audiomat amplifiers.

For years I have lusted over and looked forward to acquiring one of these amps, last week I took the plunge and purchased a Prelude Reference. The amp arrived in great shape from a great CAM member, thanks Jim! Upon first listen I was very impressed by the power and authority from this amp. It never seems to lose composure and it is very quiet, not a bit of noise while idle. I do notice though that there is something uneasy about parts of the frequency spectrum, some very subtle distortion is making it hard for me to fully engage in the music. So what’s up with that?

These amps are special?
The forums and some reviews elude to these amps being mysterious in that somehow, only an Audiomat tech is capable of working on them. I really hate not being empowered, so I need to know why it is so crucial. I have come to find out some of the things one must consider. Please feel free to correct any of my assumptions…..
1. Preamp is passive, the three tubes in the amp are drivers and a phase splitter.
2. Power tubes have a fixed bias, which means that tubes must be selected to perform in a specific range of operation that will require closer matching of power tubes.
3. I remember reading somewhere that this amp has no global negative feedback…this will become important later.
4. Prelude Amp was originally voiced and came stock with 1960’s Sylvania 12ax7’s and Winged C Svetlana EL34.

So, back to my little distortion bug…….
The first thing I do is suspect the tubes, so I roll most of my good vintage 12ax7’s in and out of the amp over the course of the next day. I notice differences in the presentation but the distortion stays, incidentally I observe less difference in the sound during tube rolling than you would normally expect to observe in a tube preamp.
Next, I roll in an identical set of winged C’s I have lying around, nope…same.

At this point I am convinced of a couple of things. I start to wonder if the nice Valvo 12ax7 tubes that came in the amp were stock? All indications are…no. So, based on that assumption I take the leap and assume that somewhere along the way somebody popped in these nice tubes and then neglected to adjust the two pots that control AC balance in the amp. This, I believe, is one of the reasons why folks are adamant about the need to have these amps “tuned” by Mutine.

AC Balance?
Lots of amps have pots for AC balance. I have a Dynaco ST-70 with a new board that has AC balance pots on it, some Scott amps have them, and Citation, Audio Research……many amps have this adjustment. In most amps this adjustment is not that critical, but after reading some forums I am convinced that in some amps, this is very critical! I eluded to a post I saw about there being no negative feedback in the Audiomat amps, is this true? I also saw a post stating that amps with no negative FB will be very susceptible to distortion if AC balance is not properly adjusted…..as in just put the pot in the middle. Hmmmm…
I am now convinced that my amp had some tubes rolled in but the pots never adjusted, here is one way of explaining how to do it. The methods vary slightly but the idea is to have balanced signal at the power tubes.
http://dynacotubeaudio.forumotion.com/t270-ac-balance-pots-on-board

Now here is where I lay my disclaimer, I am not an electrical engineer so delving into the various designs and circuits to any degree is beyond my level. What I do have is pretty well trained ears, so based on my experiments leaning towards the amp being out of adjustment, I figure I should be able to hear improvement if I happen to make it happen. So, I start spinning pots…..I trim by ear listening for the distortion artifacts to guide my adjustment. The conditions for this were not ideal but I did manage to get the amp sounding much better, to the point where the nagging obstacle preventing me from fully enjoying the music, was now almost gone. Now, the amp sounds very good! I know I have some adjustment to do that will require more than my ears but I was pleasantly surprised to see that it was possible to achieve gains by ear and that my theory was starting to look correct. I’ve seen other threads relating to this ac balance topic with huge observable gains made after adjusting, but I do think it is very dependent on the circuit.

Today I have 4 nice 1969 Sylvania 12ax7’s coming in the mail, I will drop them in and attempt another “AC balance by ear” tuning on it, wish me luck! I do want to get this done properly and will either find a tech in Ottawa that can do it, preferably one who has a distortion analyzer…..but it can be done with a scope as well, or I will take it to Montreal to the Mutine suggested tech.
Please feel free to share your experience with these wonderful amps, especially if you have had one re-tubed or are able to share any knowledge in the effort to demystify these amps and educate other folks on how to keep them running the way they were intended.


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PostPosted: Tue Aug 30, 2016 8:59 am 
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I don't believe that at any point you mentioned exactly which Audiomat amplifier you own.

I know from experience that a Audiomat OPERA REFERENCE has to have the 4 El34L replaced my Mutine themselves.

They keep a record of each OPERA REFERENCE according to serial number and they then send El34L tubes which are numbered to fit the proper tube socket...

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PostPosted: Tue Aug 30, 2016 9:06 am 
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I owned the Opera for a while. Very, very nice, but as mentioned, you need to send it to Mutine to have the tubes changed and properly biased.

There may be other ways, but I am not aware of them. That is sort of why I sold it.


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PostPosted: Tue Aug 30, 2016 9:11 am 
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meiwan wrote:
I owned the Opera for a while. Very, very nice, but as mentioned, you need to send it to Mutine to have the tubes changed and properly biased.

There may be other ways, but I am not aware of them. That is sort of why I sold it.


I don't know...but today you needn't send the amp (at least not the OPERA REFERENCE) back to Mutine, who are now located in France!!!

I am in the process of waiting for my new El34L's to arrive in the next couple of weeks.

As I mentioned, Mutine know according to the serial number what tubes to send for your particular unit.

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PostPosted: Tue Aug 30, 2016 9:12 am 
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Voodoo Funk wrote:
I don't believe that at any point you mentioned exactly which Audiomat amplifier you own.

...


2nd paragraph, 1st sentence....Prelude Reference. ...


Last edited by Jimmi on Tue Aug 30, 2016 9:16 am, edited 1 time in total.

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PostPosted: Tue Aug 30, 2016 9:15 am 
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Jimmi wrote:
Voodoo Funk wrote:
I don't believe that at any point you mentioned exactly which Audiomat amplifier you own.

I know from experience that a Audiomat OPERA REFERENCE has to have the 4 El34L replaced my Mutine themselves.

They keep a record of each OPERA REFERENCE according to serial number and they then send El34L tubes which are numbered to fit the proper tube socket...


2nd paragraph, 1st sentence....Prelude Reference. ...


Thanks Jimmi...

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PostPosted: Tue Aug 30, 2016 10:03 am 
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I'm less concerned with the "Yes, you have to send it back to Mutine because XYZ." I found lots of that already, I'd like to know what exactly is in the design/circuit that requires such care? I'm not doubting that it is required but I want to know which aspects of the circuit require this attention. We know these amps sound terrific....what trade-offs and what design considerations were made and is there another amp out there of a similar design requiring similar care? Also, let's say i want to change only the driver/splitter tubes.....can I hook up a scope and easily adjust the AC balance as described in some of the methods for this? I'm a hand-on guy and would like to do as much as I can without electrocuting myself!

-- 30 Aug 2016 18:12 --

Quote:
I am in the process of waiting for my new El34L's to arrive in the next couple of weeks.

As I mentioned, Mutine know according to the serial number what tubes to send for your particular unit.


That's interesting.....so I can assume that the current draw of each tube position has been noted and they are sending tubes to satisfy the spec, this makes sense in that I would expect that to be necessary in a fixed bias amp. I'm curious if you will just pop them in and go, or will you have to have the drivers adjusted for AC balance? I guess the question is.....is AC balance affected by a change in outputs tubes? Anyone?

-- 30 Aug 2016 18:14 --

Oh BTW, Mutine's site references a repair shop in Montreal for maintenance, not that far for me....anyone do business with these guys?

Acoustic Technologies Inc.
1970, Beaubien Street East
Montreal, Quebec H2G 1M1
Contact: Joe De Melo
Phone (514) 387-4944
Email info@acoustic-tech.com
Web http://www.acoustic-tech.com


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PostPosted: Tue Aug 30, 2016 11:58 am 
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kukakunga wrote:

Quote:
I am in the process of waiting for my new El34L's to arrive in the next couple of weeks.

As I mentioned, Mutine know according to the serial number what tubes to send for your particular unit.


That's interesting.....so I can assume that the current draw of each tube position has been noted and they are sending tubes to satisfy the spec, this makes sense in that I would expect that to be necessary in a fixed bias amp. I'm curious if you will just pop them in and go, or will you have to have the drivers adjusted for AC balance? I guess the question is.....is AC balance affected by a change in outputs tubes? Anyone?

-- 30 Aug 2016 18:14 --

Oh BTW, Mutine's site references a repair shop in Montreal for maintenance, not that far for me....anyone do business with these guys?

Acoustic Technologies Inc.
1970, Beaubien Street East
Montreal, Quebec H2G 1M1
Contact: Joe De Melo
Phone (514) 387-4944
Email info@acoustic-tech.com
Web http://www.acoustic-tech.com


Just gonna 'pop them in'...

Yes...I have dealt with Acoustic Technologies Inc...Joe De Melo
President.

My advice would be to try to deal with Mutine directly.

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PostPosted: Tue Aug 30, 2016 12:02 pm 
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One thing I can say with absolute certainty is, if you put it up for sale I won't be buying it.

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PostPosted: Tue Aug 30, 2016 12:07 pm 
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Che Cavolo wrote:
One thing I can say with absolute certainty is, if you put it up for sale I won't be buying it.


Why...a little bit of work and effort and patience is not your forte? lol

The OPERA REFERENCE is one of the finest sounding musical amplifiers out there and the fact that the company's approach is the way it is just might have a lot to do with why that is...

Of course...there is always BOSE...that doesn't require any effort.

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PostPosted: Tue Aug 30, 2016 12:31 pm 
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Interesting post.

I recently retubed my Arpege Reference. I also dealt with Joe De Melo @ Acoustic Technologies Inc..

I don't recall providing a serial number but the complete set of tubes are marked as J J 12AX7/EL34. I had purchased the Arpege used and it had Winged C EL34 and I believe Sylvania 12AX7. I had no way to determine age of existing tubes in amplifier but much prefer the J J supplied as a much clearer, balanced sound. Lost a touch of warmth but not needed with the speakers I'm running (Spendors).

I've owned a lot of gear and the Arpege really checked all the boxes for me. I especially like that this amplifier does PRAT..not quite NAIM territory but light years better than the ARC (Classic 30) and Audio Space gear I'd owned.

As previously noted finding information on these amplifiers is difficult and shortly following purchasing the unit I never received any replies from Mutine which was a first for me on contacting an audio company. I had the distinct feeling that support of their used equipment was far from a priority vs. Naim and ARC who are exemplary.

Regardless I really like the way music is reproduced through this amplifier and only wish I could afford some of Audiomat's other toys.....


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PostPosted: Tue Aug 30, 2016 1:10 pm 
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Voodoo Funk wrote:
Why...a little bit of work and effort and patience is not your forte? lol

Of course...there is always BOSE...that doesn't require any effort.


No, my forte is not: mystification, uncertainty, service entrapment, and shipping delicate heavy valuable equipment overseas for minor adjustments like a tube change. My forte is being able to take my gear to a trusted audio tech guy with a few decades of experience and knowledge, just 15 minutes from home.

Thank you for your recommendation to try Bose, I'll keep it under consideration. Any particular model you recommend? :lol:

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PostPosted: Tue Aug 30, 2016 1:17 pm 
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Che Cavolo wrote:
Voodoo Funk wrote:
Why...a little bit of work and effort and patience is not your forte? lol

Of course...there is always BOSE...that doesn't require any effort.


...and shipping delicate heavy valuable equipment overseas for minor adjustments like a tube change...


Just for the record...you do not need to ship overseas for minor adjustments like a tube change...like I stated...Mutine have a record of your particular unit and send you numbered tubes (1-4) to replace in their corresponding socket.

Interesting fact I don't believe has been mentioned...Audiomat were originally a Canadian company...my unit was made in Canada about 10 years ago...has never had a problem but now it is time to replace the tubes.

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PostPosted: Tue Aug 30, 2016 2:46 pm 
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I thought it was always a French company started by two brothers near Marseilles. It was my understanding they opened a facility in Quebec where only a few models like the Arpege were made.....

Appears I've learnt someing today....


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PostPosted: Tue Aug 30, 2016 2:54 pm 
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Quote:
I don't recall providing a serial number but the complete set of tubes are marked as J J 12AX7/EL34. I had purchased the Arpege used and it had Winged C EL34 and I believe Sylvania 12AX7. I had no way to determine age of existing tubes in amplifier but much prefer the J J supplied as a much clearer, balanced sound. Lost a touch of warmth but not needed with the speakers I'm running (Spendors).


Thanks for chiming in, the more experience we can compile in one place the better! Like me some of you have probably scoured every corner of the internet searching for info on these amps....there just isn't much out there. I did find a schematic for the Arpege front end on some French site!

I just got my Sylvania 12ax7's today and popped them in. I've rolled many very good tubes through in the last week, Mullards, Tele's, RCA's, and a bunch of great 5751's. The one I found best out of my bunch was the command series RCA 5751. That tube sounds very good almost anywhere I've tried it. So I pop in the new Sylvanias and holy **** de godamn! Best yet, nothing sticks out, a lot of separation and room in the sound, composed and balanced top to bottom. It really sounds as if this tube is putting the amp in a very good tonal balance. I'm stoked, I'm not hearing any distortion artifacts so I can't be gravely off on the ac balance...but if it's this good now then I can't imagine it getting tighter!

I think in your case your power tubes may have been toast, but I bet your 12ax7's were fine...and I bet the improvement you are mentioning is more due to the power tubes. I know they are using JJ's now for re-tubing and I'm sure they are fine, they likely ran out of Sylvanias a long time ago, they aren't getting any cheaper.

Quote:
The OPERA REFERENCE is one of the finest sounding musical amplifiers out there and the fact that the company's approach is the way it is just might have a lot to do with why that is...

That's the way I feel too, I'm very happy the designers decided on a no compromise approach, I don't mind the extra effort for the payoff of a super quiet, distortion minimized tube amp that sounds amazing! I've had some good tube amps, this one has the most effortless authority and bass control out of any amp I've owned, SS or tube!


Quote:
Interesting fact I don't believe has been mentioned...Audiomat were originally a Canadian company...my unit was made in Canada about 10 years ago...has never had a problem but now it is time to replace the tubes.


My understanding is that they started in France and then launched this distribution/manufacturing model later as they attempted to break in in North America. My Prelude Reference is made in France. From what I've been reading, the distributor...Mutine, is basically a one man in semi-retirement operation now and there are numerous accounts of it being near impossible to get info from them/him. I haven't tried.


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