New Cornet 2 Build

Bobzilla · « **on:** 19 Sep 2010, 06:07 am »

My second Hagerman project is finally taking shape.
The Clarinet Line Amp that I finished months ago not only exceeded my expectations but inspired me to overhaul and modify my Acoustat 2+2 speakers. Somewhat time consuming, but worth every second. I've often found that substituting 25 or 30 year old electrolytic capacitors with new film caps can make dramatic improvements in the sound!
Anyway ... I digress ...
The Cornet 2 board is all but complete. I mounted the Mundorfs on the bottom and the Russian teflon bypass caps on the top. Increasing the nylon spacers by just 1/4" allows plenty of room.

I used Nude Vishay resistors in locations that I felt they where pertinent and could handle the current.

I'll load some shots of the metal work as it forms. I don't enjoy that part of the creative process nearly as much as the electronics, but it has to be done. 99.9% is in the sound but the visual presentation carries a lot of weight too!
Stay tuned ...

christos · « **Reply #1 on:** 20 Sep 2010, 05:17 am »

Quote from: Bobzilla on 19 Sep 2010, 06:07 am

My second Hagerman project is finally taking shape.
The Clarinet Line Amp that I finished months ago not only exceeded my expectations but inspired me to overhaul and modify my Acoustat 2+2 speakers. Somewhat time consuming, but worth every second. I've often found that substituting 25 or 30 year old electrolytic capacitors with new film caps can make dramatic improvements in the sound!
Anyway ... I digress ...

Please do digress! I have a pair of Acoustat 2's and I am in the process of overhauling the interfaces. The caps are being replaced (a combination of Blackgates, Sonicaps and Mundorf SIO), the socks are down and the panels are vaccumed and re-tightened (they come lose after so many years) and some wire and resistors are being replaced (the big slider). I'd love to hear what you are doing with the 2+2's and what you use to drive them.

Quote from: Bobzilla on 19 Sep 2010, 06:07 am

The Cornet 2 board is all but complete. I mounted the Mundorfs on the bottom and the Russian teflon bypass caps on the top. Increasing the nylon spacers by just 1/4" allows plenty of room.

I used Nude Vishay resistors in locations that I felt they where pertinent and could handle the current.

I'll load some shots of the metal work as it forms. I don't enjoy that part of the creative process nearly as much as the electronics, but it has to be done. 99.9% is in the sound but the visual presentation carries a lot of weight too!
Stay tuned ...

The new build is looking great. Can you give a brief run-down of your component choices?

Let us know how it sounds!

Bobzilla · « **Reply #2 on:** 21 Sep 2010, 04:42 am »

Christos,

For Acoustat work, first do research to decide what you wish to do, and how far you want to go. I suggest the following, in no particular order:

http://www.integracoustics.com/MUG/MUG/tweaks/acoustat/

http://www.diyaudio.com/forums/planars-exotics/18817-acoustat-2-2-mods.html

http://www.diyaudio.com/forums/planars-exotics/58583-acoustat-tweak-forum.html

http://eslrepair.com/default.aspx

http://www.audiocircuit.com/index.php?c=ACO

http://forums.delphiforums.com/ESLForum1/start

http://www.audiocircuit.com/index.php?c=ACO

http://www.audiocircuit.com/A-HTML/AA-Brands/A/Acoustat-ACO/941-ACO-GEN-
AS_CMOD_-M-A01.htm

http://www.izzy-wizzy.com/audio/spkrif.html

http://www.diyaudio.com/forums/planars-exotics/57310-high-voltage-supply-filtering.html

Here are some shots that are self evident:

I used solid silver, teflon insulated wire. Capacitors were Solon, Mundorfs and Russian teflons. I kept the rotary pot and cleaned it of the twenty plus years of corrosion that had grown. (not unusual for components in close proximity of high voltage) Maintain as much insulating space around conductors as posable and always be aware that ...

THESE SPEAKERS ARE CAPABLE OF DELIVERING A FATEL SHOCK. EVEN IF NOT HAVING BEEN PLUGED IN FOR SOMETIME, IF DISCHARGED ACROSS THE CHEST, THERE IS THE VERY REAL POSSIBILITY OF CARDIAC ARREST.
BE RESPECTFUL!!!

That said ... have fun!!!

christos · « **Reply #3 on:** 22 Sep 2010, 02:31 am »

Thanks for the links and the pictures! I have seen most of the links but there are some new stuff in there. I am sceptical about some of the mods, especially those that relate to the bias circuit. Better components, yes, changes in the basic interface design, not so sure.

I see that you still have the old non-medallion transformers and the old 6-ohm pot. What is not clear is if you changed over to the C-mod, which I assume you did. Also it is not clear from the pictures if the 1-ohm resistor is still there! Did you remove it?

It is also interesting that you have four capacitors as opposed to the stock three. It's great to have the space to work with the 121 interfaces. What values did you use? Did you go with 50, 10, 0.1 and 0.01uf?

And to bring the discussion back to Hagerman products, how did you like them with the Acoustats? I assume tube gear works well with 'stats since they may complement each other (warm tube sound vs, analytical presentation from the electrostatic speakers).

Bobzilla · « **Reply #4 on:** 22 Sep 2010, 04:21 am »

Christos,

Correct. Those are indeed the basic capacitor values I used. I applied the following "factory authorized" Medallion mod, minus the Medallion Transformers themselves. I think there is little difference in the high freq. transformer and, supposedly, no difference in the low freq. transformer.

http://www.audiocircuit.com/A-PDF/AA-Brands/A/Acoustat-ACO/MK-121-2_MED________-M-EN2-941-ACO.pdf

Notice that in addition to the capacitor value change, there is a major change in the audio circuit. I took a shot and I feel it sounds absolutely superb! (The additional resistors called for in the above mod are Mills wirewound 12 watt pieces, on the terminal strip mounted on the high freq. transformer. They are three in parallel with each other and in series with the 6 ohm pot. (again as per mod)
I didn't mod the bias supply at all. I did, however replace all of the high voltage ceramic caps. I also match every component as closely as I can to maintain left/right channel consistency. I am aware that many things are completely out of my ability to match them, but this is one of the differences between "production work" and passionate love of ones hobby. Even if it is (audibly) imperceptible to everyone except me ... that's enough. I balance at EVERY opportunity! Example: the high pass capacitor banks left speaker/ right speaker differ only by 0.003 mfd.
It works for me.
I am very much impressed with Jim Hagerman's work at all levels. The engineering is excellent and frighteningly quiet. The PC board is among the best I've ever worked with, both in layout (this is an underrated art form and it's far beyond just making things fit!) and quality of materials. I then use (what I think is) the best components for the circuit requirements to enhance the previously mentioned points.
It really works well for me. Please see following for my first Hagerman project:

http://www.audiocircle.com/index.php?topic=63343.0

As to compatibly with the Acoustats, I am presently bi-amping my system with the 2+2's powered by a Haffler XL-280. I'm very happy with this. I typically run them with fully modified Curcio MKIII's but these are next in line for a complete overhaul.
I mean after the Cornet 2!!!

david62 · « **Reply #5 on:** 23 Sep 2010, 01:42 pm »

Beautiful work on the Cornet 2.What do you plan to use for a case?Be sure to give a review after you let things settle in.
Dave

christos · « **Reply #6 on:** 23 Sep 2010, 11:42 pm »

Bobzilla,

This is all great info, thanks for the link to your past build! I now have a much better understanding to what you are doing with the Acoustats. Your thinking is very close to mine, although I managed to find a pair of interfaces with the medallion transformers, which I am using. But I agree that the interface C-mod and the new capacitors are much more important than the transformers - a view also shared by ex-Acoustat engineer Roy Esposito. Once I have replaced all the capacitors I will report back with results.

Regarding your Coronet build, I think you are doing the right thing going with a custom case. Will you do something similar with the Clarinet case?

I just received the Lancing case in the mail, and although it is of good quality, it leaves something to be desired. What I don't like about it is that it "rings" a lot! I think that some sort of dampening material on the top and bottom plates is absolutely essential to keep the ringing down, especially for a tube project. Perhaps a few pieces of Dynamat would help. However, for a $100+ case I was expecting something I can use as is. Thicker metalwork would also have been nice, the top/bottom plates are too thin for my taste. If I build more Hagerman projects I think I will go a different route with the case. I am thinking a wood case with copper internal lining - anyone tried that?

Bobzilla · « **Reply #7 on:** 26 Sep 2010, 12:15 am »

The case I'm using is a full size Lancing Case. I agree fully on your feelings about the "quality and feel" of these boxes. but they seem to be above average for the money we paid. It's not just DIY people that deal with these compromises, the same issues plague the pro's as well. Worse yet, they have to guess at what level their customers will accept and an error at that point may doom their entire production run, regardless of the "sound".
We don't have that complexity, we just have to satisfy ourselves.
The ringing of the box can be dealt with in several ways. I chose to begin by bisecting the inner cabinet with an aluminum rib. This wall, with a thin layer of "Sorbothane" on top and bottom separates all line level conductors, serves as an additional mounting position and achieves a surprising level of damping. Note that half of the transformer also mounts directly into threaded holes in this rib.

The red heat shrink covers a short piece of 1/2" conduit which conveniently shields the transformers secondary conductors and delivers them directly to the opening on the PC board.
The metal work continues ...

david62 · « **Reply #8 on:** 11 Oct 2010, 07:12 pm »

Mundorf SOL caps are a point of contention for some here.How does your Cornet 2 sound?

Bobzilla · « **Reply #9 on:** 12 Oct 2010, 04:16 am »

I'm really surprised that there appears to be some growing disinterest in the Mundorf SOL capacitors. I've used them in both my (Hagerman) Clarinet and the interface assemblies of my Acoustats.
I recommend them highly, especially bypassed with a Russian teflon!
I haven't tried all the esoteric brands and types of capacitors, I have neither the time or the money. I can however state this ... if you haven't been involved with this hobby for a long, long time let me assure you there are literally hundreds of brands, internal compositions and methods in which to use them.
They all have a "sound".
Is this "sound" good?
That's up to you. I can say that often the difference is striking. Remember that there is only one person you have to please, assuming that you're building this for yourself.
Be truthful to that person!

david62 · « **Reply #10 on:** 12 Oct 2010, 03:06 pm »

I like the SOL caps in my Clarinet.My CD player has harsh highs,but I attribute that to the player.My vinyl sounds good using the Clarinet with SOL caps bypassed with Russsan teflons.I am using the phono stage of my Mac. C24 into the Clarinet.I am using Amperex 12au7's in the Clarinet,which I find nice.

Bobzilla · « **Reply #11 on:** 20 Oct 2010, 03:33 am »

Never having devoted this much time and effort to a dedicated phono stage , it occurred to me that I had no way to accurately test it for correct operation. Sure, the tubes light and the scope shows that a signal is passing through and being amplified but what of the accuracy of the equalization?

The Hagerman RIAA2 kit.
I think this tiny piece of test equipment is absolutely necessary for the completion of this (or any) phono stage. The only suitable substitute I could think of would be using a test record and your vinyl front end but, in all honesty, that is going to be far from easy and may not be all that accurate. Another aspect of this method is that it would be difficult to isolate the origin of a problem: "Is it the unheard phono stage? Is it a cartridge problem? Alignment? Stylus?" Too many variables ...
The point is, one just could not be sure.
The RIAA2 is an ingeniously simple circuit that alters an input in a manner that simulates the reverse of the RIAA equalization. Feeding this output into the input of a phono stage should give a completely equalized output. That is to say that any signal injected into the RIAA2 and then through the phono stage should produce an identical amplified signal out.
Elegant!
Recommended!
It was also a welcomed break from the metal work!!!

david62 · « **Reply #12 on:** 20 Oct 2010, 02:06 pm »

I'm anxious to hear your review and see pictures of your new Cornet 2.
Dave

Bobzilla · « **Reply #13 on:** 23 Oct 2010, 10:57 pm »

The cornet2 is complete. The pictures show the final metal work and my minimalist approach to esthetics.

I added nothing to Jim's design. Signal wire is #24 teflon insulated solid silver. Resistors are PRP, Nude Vishay, and Mills. Plugs are Vampire. Power cord is non-exotic, shielded #16. Feet are Isopods. Tube compliment consists of a Sovtek 5Y3GT, a JJ ECC802 S, and a pair of 12AX7A -c's. After cleaning the pins and tube sockets, I wove a tight strand of teflon tape around each of the pins where they enter the base. I think this is cheap and effective microphonic control. The signal tubes will also be fitted with a Teflon "O" ring for the same reason.
Preliminary testing looked good except for the 1Khz. square wave shot.

I've done something wrong ... and I did it really well! All voltages are well within spec. and the channels are identical.
Sometimes one has to get away for a while, put it down.
Well maybe after one puts it on line ... just to hear it ... it does have to work in ... Right?
I sent a request for advice from the mother ship (Jim!) and put it into my system.

First, it is dead quiet! No hum, no buzz. I wasn't even sure it was functioning. I lowered the stylus into the lead in grove of my test record and heard my first grove in years.
Very nice.
The first impression is that it's shy in the lower octaves. This almost certainly is to be expected with the first hours of burn in and with my malfunctioning square wave response. I would be shocked if the two were entirely related, that is if the poor square wave was demonstrative of the virgin capacitors, tubes and electronics. I've not experienced anything like that before.
That's why I contacted Jim.
I'm withholding any true critical listening for a while. I also have some time consuming tuning to do on my Souther Tri-Quartz tone arm.

Everything effects the sound. I've repaired and calibrated Horizontal Situation Indicators and Angle Of Attack devices used on military aircraft and I can honestly say that properly setting up this tone arm is, by magnitudes, harder than anything I ever incountered in Avionics Repair!!
Almost done ...

poty · « **Reply #14 on:** 24 Oct 2010, 09:55 am »

Quote from: Bobzilla on 23 Oct 2010, 10:57 pm

Preliminary testing looked good except for the 1Khz. square wave shot.
I've done something wrong ... and I did it really well! All voltages are well within spec. and the channels are identical.

What is the source of the 1KHz sqare signal? If it is directly from the signal generator - you have rather predictable results, because there is the RIAA correction inside the device.
From the manual of the Cornet 2:
"Connect a 1kHz squarewave signal through an inverse RIAA Filter and into the
Cornet2. Observe output on oscilloscope."

david62 · « **Reply #15 on:** 24 Oct 2010, 12:41 pm »

Beautiful build!Keep us posted on how it ripens and your impressions of vinyl played through the Cornet 2.
Dave

Bobzilla · « **Reply #16 on:** 24 Oct 2010, 05:01 pm »

poty,
Understood.
I appreciate your input.

So what have I missed?
I woke up this morning at 3 AM thinking that the error must be in the equalization circuitry. I gave some thought to pulling it out and and returning it to the bench but ... well, that's just crazy.

Dave,
Thanks for your complimentary observations. Appearance matters. It's certainly not as important as the audible results but ...
There was a time long, long ago, a time many have called "The Golden Age of HI Fi", when McIntosh sent a mobile lab on a trip from dealer to dealer. The deal was that a McIntosh equipment owner could bring any Mac. product in to the "Lab" and it would be placed on the bench, checked for proper operation, repaired, and or, brought up to spec. glass cleaned, and returned, with a complete spec. sheet of its present condition. FREE! In real time, while you and as many people as could squeeze into the store watched, talked, and partied in a manner that only audio geeks could appreciate.
The Mac guys were superb. Not only were they extraordinarily competent technicians, but they loved their job and the showmanship they displayed. It was truly impressive! (Example: any tubed Mac that came in, before it was even plugged in, had ALL of its output tubes replaced. This was done by ceremoniously tossing them one by one into a metal garbage can as the audience cheered. Considering the reverence we have for tubes now ... it was amazing.)
Now, you could also bring in Non-Mac. equipment. They wouldn't repair it but they would put it on the bench and give you a graphic read out of its specs.
That's the ticket!!! I had no scope, signal generator, nothing but a VTVM. Opportunity was knocking.
This was around the early 70's. I had been modifying Dynaco equipment for some time and I had a "super hot rod" Dyna/Pass preamp that bore no resemblance to its original anything. It had a huge, external umbilical corded power supply, a selector switch and a difficult to rotate, stepped attenuator sticking out of the stock sub-panel of the pas with vacant holes were the many switches and potentiometers once were mounted.
Ugly.
At best ... ugly.
I waited for my number to be called and then pushed my way through the crowd.
"What, exactly, do we have here?" Mac. asked.
"It's my version of a preamp." I replied.
In a low voice he asked,"Does it sound good?"
"Oh Yeah, it sounds great."
"OK, Let's see how it looks."
His voice returned to showman. The fact that its frequency response tested as good as the Mac. preamps was shrouded by the fact that that was the only test they did on Non-Mac. amps. That was still very cool.
But ...
It looked repulsive. I had never really thought about it until I saw it crouching there among the chrome and back-lighted Mac. pieces.
I vowed to myself that I would never discount the appearance factor again. If it is worth doing, I'm going to make it such that one doesn't have to avert ones eyes to look in its general direction!
Minimalist, that's how I define the esthetics of my projects.

You may now return to 2010, but I will never forget the sound of literally dozens and dozens of 6550 vacuum tubes shattering and the crowd screaming for more ...

The Horror ...

david62 · « **Reply #17 on:** 24 Oct 2010, 05:57 pm »

Bob,

I enjoyed reading your piece about the McIntosh clinics of the '70's.I sure wish that I could bring my Mc240 in and get a new set of output tubes...I am using my Mc240 with my Clarinet line stage.I am using a C-24 for a phono stage into the Clarinet.Have you had the opportunity to compare or hear many Mcintosh pieces?How does your Clarinet stack up to high end pieces?The thoughtful quality of your build really shows,and it's true that with a good appearance,there are no excuses.
Dave

nrenter · « **Reply #18 on:** 24 Oct 2010, 07:43 pm »

It's almost like you're measuring a simple RC circuit:

poty · « **Reply #19 on:** 24 Oct 2010, 09:02 pm »

Quote from: Bobzilla on 24 Oct 2010, 05:01 pm

poty, Understood. I appreciate your input. So what have I missed?

You haven't really answered my question fully. What is the source of the signal?
How it looks like at the input jackes of inverse RIAA thing? At the output jackets of the inverse RIAA? It may answered your questions.
Another point - it seems you have too big attenuation of high frequencies. Please check all the "parallel" capacitors and resistors values.