Preamp Deal of the Century

I had my Cortese for sale and just cancelled the ad. I can't bring myself to give it up. I really enjoy the dynamics and transparency of the Cortese. My Audio Aero Capitole AI, which I had connected directly to my amp, sounded smeared without the benefit of the Cortese. The Cortese made everything sound right to my ears. For the record, mine has operated flawlessly for 2 years, other than tube issues, and Mick has been very responsive to my emails, even recently. Horses for courses, I guess, but I really like what I have. For what it's worth, and I know some of you don't give a rat's ass: In my limited experience, I have also owned 2 other "Class A" preamps with built in phono stages and 1 "Class A" stand alone phono stage. As a caveat, these were all in the lower price range of "Class A" components. That said, the Cortese is much superior to any of those other pieces that I had in my system. But then again, I can't say that what I like is necessarily what someone else would like. Horses for courses.

Right On Thaluza!

I got my sauvignon about a year ago. I waited for it almost 9 months. It was when Supratek had announced that it was about to close. My sauvignon came into a Chardonnay exterior (there is the chardonnay name engraved on it) but Mick assured me that it was indeed a sauvignon. They had run out of sauvignon exteriors and as supratek was closing, he used a chardonnay exterior. He gave me a paper that was assuring that it was indeed a sauvignon.

I am extremely satisfied from Mick. His emails were very responsive, and there was a response to every of my (more than 60) emails I sent him. I did not get any rude response, and I was very excited that he was promptly answer even my most silly questions.

I love my pre. The finish is spot on, no problems at the chrome plates. It also has a headphone out for my Sennheiser 650 (matching their 300 Ohms).

I can not be more satisfied than I am. I hope Mick is well...

There is a Chenin just listed today for sale finished in chrome and piano black.

"there is a" = "my"

I have made another mod to my Chenin that may interest some. As you know, I have converted it to run 7193 tubes in place of the 6SN7s; that's still humming along fine.

I recently decided to replace the no-name electrolytic filter caps in the power supply with 630V Solen PP film caps. I used the same value caps as the electrolytics - that would be 100uF and 33uF. The 100uF 630V cap comes in a metal can with radial leads, the 33uF is a standard film cap with axial leads. It is a very simple swap, just unglue the old caps from the chassis, remove the wires one at a time, and transfer them to the new caps. I fabricated clamps for the new caps, and also glued both of them down wth "Amazing Goop", a very strong adhesive/sealer. I recommend clamping all power supply caps (even though the stock caps aren't!) as it would be unfortunate to have one come loose and touch a part of the metal chassis.

How does it sound? I noticed a pretty obvious difference immediately. Cymbals and drum thwacks sound sharper, there is more detail in the highs, and the background seems a bit blacker. In general, the sound is more robust and dynamic - I heartily recommend this mod. Keep in mind the rest of my Chenin is not stock, so your mileage may vary. One more bonus: the film caps will last forever, unlike the electrolytics.

If you try this - enjoy!

I did the same thing to my Chardonney, only I used motor run caps. Definitely made the preamp better. Tighter bass, cleaner, more dynamic, better soundstage. I also replaced the stock caps in the linestage with Mundorf Silver/Oil caps - big improvement. I did not have the Auricaps there but, some square blue caps. I tried replacing the other square blue caps near the rectifiers and it messed up the sound. Emailed Kevin Covi about this and he said those caps are not critical and just leave them in. I put them back and the preamp sounds tremendous.

Those square blue caps are probably Wima caps - OK at best, not what anyone would call high end. My Pre has the Auricaps and I'm really enjoying the sound now; I've though about replacing the Auri's a million times, but still haven't done it yet as I like the warmth they bring to the sound.

Now if I stumbled across some Duelunds, maybe I would change my mind...

I bet the Duelunds are more linear not as warm. I emailed another Supratek owner that upgraded to Vcaps from Mundorfs and he likes the change. He GAVE me his Mundorf caps! What a saint! Gotta love him for being so generous! I have read that one reviewer did not like the Vcap upgrade over the Auricaps. Enjoy listening I know I am!

Glad you're enjoying the Mundorfs, Jeff

I think there is a real synergy between the Solens in the PS and the 7193 tubes. Since I put the Solens in, the highs I'm hearing a really astounding - they seem to float out into the room with me; everything sounds much more 3-dimensional than before. I would suggest that anyone who does the 7193 mod also do the Solen mod, it's that good!

Any by the way, this is all with one of my backup sets of speakers, Dahlquist M905s. My Infinity RSIIb speakers are currently being completely re-worked by me, with outboard x-overs, internal bracing, etc. I can't wait to hear how they sound in this setup!

Hey Fiddler! Thanks for the caps they sound great! I bet your Supratek is sounding incredible. I will have to try the 7193 tube mod sometime. I actually think the stock EH 6sn7 tubes sound best most extended although the Tunsol Black Plates are a little more nuanced and tubbie sounding. Think I should sell these since they command a high price and are all but gone. I have 6f6 Sylvanias in the regulator position and the 6106 Bendix tube as recitfier. I wonder if a 5ar4 tube would give me a little more warmth in the mids and a little more snap (snare and the like) in dynamics. Not sure.
I still have a Modwright SWL 9.0 preamp which betters the Supratek in dynamics. Different sound. Gotta sell one preamp. I think I'm going to keep the Supratek can get them anymore! The Modwright is a great preamp also but they are selling for so cheap right now. I'll get killed on it! Everything is going cheap now!

I'm using a 5AR4 rectifier in my setup, but not the stock one. I'm using a NOS GE 5AR4, the one with the copper sides on the plates. I think it sounds excellent and it is nowhere near as expensive as the Mullard GZ34 (I haven't heard those, however). You can get the GEs for ~$50 at Antique Electronic Supply.

I have been playing around with the regulator tubes since I did the Solen mod. Here are my opinions:

Stock Sovtek 5881/6L6WGC: The worst of the bunch. Sounds glary and brittle, with deficient bass

NOS Tungsol 5881/6L6WGB: I picked up a used pair at a swap meet a year or so ago for ~$30, I think. They immediately replaced the Sovtek 5881 in my setup, and have been there ever since. They sound much better than the Sovtek 5881, with more bass and without the glare on the highs. They only read about 63 on my tube tester, barely in the "good" region, but they still sound very good.

New Sovtek KT-66: I picked up a matched pair of these a couple days ago from Parts Express for $50. I like them! They have a very full sound, with killer bass, yet still retain most of the high-end shimmer and detail. I can see why Mick recommended these to people who want to tube roll. They do not get very good reviews online as power tubes, but they seem to be excellent regulators. Very beefy construction, with copper grid posts and a larger plate structure than the Sovtek 5581/6L6WGC, so they are definitely not just re-badged versions of that tube in a different bottle. The metal base and coke-bottle shape look cool as well. I'm very pleased with this purchase.

Just checked with AES - they're out of the GE 5AR4s, even though they're listed on the website. Bummer. Glad mine still have many years of life in them...

PS cap replacement - anyone tried any other options - I have done the V caps and they were definitley an improvement so I am keen on upgrading power supply ( alps RK50 pot was also very good but pricy ) - another tweak I recomend is replacing the bottom plate in both pre and PS with something more rigid and using proprietry footers - I used symonite sandwich panel ( like alucabond ) - I drilled new vent holes of course

Cheers

Experiences with GZ33 vs GZ34? I'm looking for anyone who has compared and contrasted these two rectifier tubes in a Supratek preamp. The GZ33 is very cool looking, but how does it sound versus the GZ34/5AR4?

I've had numerous rectifiers in my sauvignon and cabernet. They include the 6106, Sylvannia 5a45, Mullard GZ33, Mullard GZ37, and the Mullard/Amperex metal-base GZ34. The Mullard/Amperex metal-base GZ34 is by far the best in my preamp. The improvements have been in the areas of reduced noise, longer note sustain/decay and to a lesser degree better harmonics which has increased the timbre. I've had my GZ34 in the system for about 5 years and my system is always powered on and playing.

From what I recall about the GZ33 and GZ37 specs the heater current is a good deal more than the GZ34. I think that anyone rolling regulators or rectifiers in the suprateks should consider the impact of one upon the other. Some of the larger regulator tubes place their own demand upon the power supply.

Well, I think my GE 5AR4 with the copper sides on the plates sounds great, but I just bought a Mullard GZ33 on e-pay, and I'll try it out when it arrives. If it doesn't sound as good as the GE, I'll take it out. I'm not running 6SN7s anymore, I'm using the 2C22 single triode, so I've reduced the demand on the power supply already - I guess I'll find out what the GZ33 sounds like soon enough...

So, I tried the Mullard GZ33 tonight, and I like it a lot! I bought a pair, and both had good getter flashing, full lettering, and tested 100%+ on my tube tester (set to 5V4, 5U4 and 5AR4 settings). Compared to the GE 5AR4, the background is cleaner, the soundstage is more focused (I can tell more easily where the instruments are) and the bass is a bit tighter and deeper. Cymbals are cleaner and have more focus. I swapped the two tubes back and forth twice each (I didn't want to stress the preamp with too many rapid on/off cycles). It just sounded more powerful and focused with the GZ33 than the GE 5AR4 - I'm keeping it in.

So my current optimum combo is:

Mullard GZ33 rectifier
Sovtek KT-66 regulator
Ken-Rad 2C22/7193 output tube (sub for 6SN7)
Solen PP Caps (33uF and 100uF, 630V) for power supply

It sounds incredible, IMHO.

Those older late 50's,early 60's Mullard rectifier tubes have a certain magic to them that is truly musical. Legend has it that they were made by Elves in the Black Forest. Those same Elves today are making Keebler cookies. (O:

I had occasion to very recently e-mail Mick. My Chenin that I purchased direct from Down Under is still purring quite nicely. My question to Mick involved some machinations that I was doing for which I was seeking his advice. As when I was preparing to place my order, asking many questions, in as many e-mails, Mick responded to my most recent question quite promptly. Thanks Mick .!!!

For those folks that think it's risky to buy boutique equipment, I own three pieces, plus two others that are semi-boutique, and support for all, has been first rate. Moreover, performance to value has been far more than first rate.

Obviously, the phrases your mileage may vary, and let the buyer beware apply; however, for me, these purchases have been the most rewarding over the many years and purchases that I've made while being immersed in this crazy hobby!

More importantly, believe it or not, I’m probably more risk adverse than most; however, after beginning in this hobby well before the internet, my advice was from periodicals spouting all amps sounded the same etc The internet and sites such as this have changed all of that and thankfully so! I’ve found that a little risk has paid me back in a ratio that both the house wins and the buyer in my case, has never lost!

For all of those folks that want to keep their purchases coming from established company’s so be it. I wanted to continue working for General Motors 15 years ago, when my Division was sold. Today, well not so much !!

Cheers to all,

-Mike

So, I tried the Mullard GZ33 tonight, and I like it a lot! I bought a pair, and both had good getter flashing, full lettering, and tested 100%+ on my tube tester (set to 5V4, 5U4 and 5AR4 settings). Compared to the GE 5AR4, the background is cleaner, the soundstage is more focused (I can tell more easily where the instruments are) and the bass is a bit tighter and deeper. Cymbals are cleaner and have more focus. I swapped the two tubes back and forth twice each (I didn't want to stress the preamp with too many rapid on/off cycles). It just sounded more powerful and focused with the GZ33 than the GE 5AR4 - I'm keeping it in.

Hello,

Good for you! I hope you are posting this as a result of your "own" experiment only and not for the others who have no time to understand what is going on in the circuit to try.

With all due respect, are you saying that the preamp PSU (5V filament supply) rated for 5Y3/5AR4 current draw (2.0 amps) according to the circuit design is good for a GZ33 with current draw of 3.0 amps? Very dangerous situation for those who are not aware of this limitation I would say. Did you check the filament transformer rating of the rectifier supply or noticed any change in heat from the filament transformer? If not the proper rating and noticed an increase in heat from the PT, turning ON/OFF the unit as frequent to avoid stress to the PSU is the last thing I would be concerned of.

Another thing, the 5AR4 drops 17 V at 225 ma, the 5V4 is 25 Volts at 175 mA, the GZ33 being similar to the 5U4 drops 44 V at 225 mA for G/GA and 50 V at 275 mA for the GB. Not really the same (21/27 volts change!) and I bet that is why the change in sound because you are changing the OP of the tubes. A Mullard GZ33 cost a lot. It seems that a 25W aluminum ohmite dropping resistor on the B+ line will work also no?

Do you have a measurements of the B+ from GZ34 to GZ33 and see the difference? Since you are being adventurous, what is the reason why you did not try a 5U4?

I am only reporting back what has worked for me, YMMV. Remember, my unit is not exactly stock anymore, as I stated above. The Mullard GZ33 is actually less expensive than the Mullard GZ34 - I bought two for the price of one GZ34. I am very aware of the larger voltage drop of the GZ33, and was not expecting better sound from it, yet that's exactly what I got.
Mick recommends the GZ37 as an alternate for the 5AR4 in the manual for the Chenin, and it also has 3 amp current draw, so that does not seem to be a problem...

I have to say, I just went back and listened again to the difference between the 5AR4 and the GZ33 in my preamp. It's very clear to me that the Mullard GZ33 is superior to the GE 5AR4. The sound is clearer, cleaner, more focused, and overall just has more guts to it. Not what I expected from lowering the B+, but it's what I got.

Is the OP of the tubes changed? Most certainly! Is that a problem? No, isn't that the whole point of rolling rectifier tubes? It's not like the signal goes through them, you know...

Hello Ait,

Oh, do not get me wrong, I am just curious following your experiment. Yes, I am aware that your unit is not stock anymore. The same reason why I asked if you know the rating of the rectifier filament supply.

Yes, you are right, on the manual the GZ37 is listed as "ok" replacement of a 5AR4. He also listed a GZ32 but not a GZ33 or a 5U4. That is my point. I thought the GZ37 has a current draw of 2.8 amps max, 200 mA amps difference from a GZ33 (with 3 amps).

regards,

Abe

No argument here as far as rolling the rectifier. Yes, no signal goes to it except the dc voltage it provides is the whole signal that is amplified. Besides, your unit is different now compared to stock. Let's say your preamp is a new design using the psu of a Supratek preamp and any experiment you have may or may not be applicable to stock Chenin's.

Oh well, as long as u have fun doing what you are doing.

Regards,

Agreed. My Chenin is not stock anymore. By the way, the Radio Museum site lists the current draw of the GZ33 as 2.8 amps, same as the GZ37, which is why I figured that there would not be a problem since the Chenin is approved by Mick to run GZ37s. They even have a picture of a Mullard GZ33 on the page (looks just like mine, except mine has yellow lettering - only done in 1964 from my understanding).

http://www.radiomuseum.org/tubes/tube_gz33.html

By the way, the Radio Museum site lists the current draw of the GZ33 as 2.8 amps, same as the GZ37

Hmmmm......different on mine. I thought the 5U4 is the same as a GZ33, current draw-wise, and the GZ37 is 200 mA less.

GZ37

GZ33

regards

So to settle this once and for all I emailed Mick, to see if he would weigh in on this. His typically succinct reply:

"33's are fine - good tubes actually."

So I would say that everyone should feel free to use the GZ33 if they so desire, since the designer of the preamp says it's OK to do so.

There you go, it is settled. Let the GZ33 frenzy begin!

No problem here. Besides, my all stock Supratek Chenin is in the corner of my listening room collecting dust for almost 10 months now and counting. I was hoping a little bit that it becomes a collectors item in the future. We'll see...

regards

Hello,

Are any of you using Synergistic IC's with active shielding?

I get a hum if I use them on the output section going to the
amps (Nagra VPA, 50 watt, Class A). If I disconnect the shield, the buzz is diminished yet not completely removed.

Thanks for your thoughts,

Cr

Cr - I have DIY active ( 12vdc) shielded single ended IC from dac to cortese and there has been no hum at all - I am doing similar to amp ( solid state) - a rough prototype did not hum - it all gets very complex with lots of different currents at the rear of the rack though -
I did try them on a a passive pre to OTL graff amp of a friend and there was quite a hum

Cheers

Rectifier tube question. I know i could probably find answers to this question if I spent an hour looking through these threads, but thought I'd just save time and ask outright. What is the best rectifier tube I can try for my Supratek Syrah? I've been using Mullard GZ37, comparable to this one:
http://www.kraudioproducts.com/Mullard-Brimar/ProductDetail.aspx?CatID=65&ProductID=150
and have gotten fantastic results from it, but it went dead last week. I've since been using a Bendix, but it's nearly as good as the Mullard. Should I just get another one of these GZ37? Might this more pricey GZ37 do the trick:
http://www.kraudioproducts.com/Mullard-Brimar/ProductDetail.aspx?CatID=65&ProductID=155

or do I need to refocus elsewhere. thanks in advance! Still looving my Syrah after about 7 years now!!! It's the only piece of my equipment that hasn't changed!

(I meant to say that the Bendix is not nearly as good as the Mullard, IMHO of course..)

Outlier, if you look a couple posts above yours, you'll see my review of the Mullard GZ33. It's approved by Mick, and I think it sounds fantastic.

Thanks Ait (Have you tried the GZ37 though - just curious about the comparison).

No, just GZ33 and GZ34/5AR4. I prefer the GZ33.

If you look at the ratings, the GZ37 should not be used with a first PS cap greater than ~4uF due to too great of a current draw on the tube; the first PS cap in my Chenin is 3uF. Yours is probably close to that. Maybe that's why the GZ37 died?

The GZ33 can handle a lot more (up to ~60uF, I think I read somewhere).

Ooops! I meant to type "the first PS cap on my Chenin is 33uF", hence why I wouldn't use a GZ37 - now my post makes sense!

Sorry if there was any confusion...

Thanks for the info Ait. I'll see can I get my hands on the GZ33. Just to mention, I was using the GZ37 on the Syrah for about 6 years, so it had a good innings. It really was so beautiful compared to the Bendix I'm using now which seems a bit hard/etched - it's subtle, but I hear it. Anyways, happy listening.

Hi guys, I just ordered my Chardonnay on June 5th. I think Supratek is still in business. My friend(who got the experience in repairing countless high end equipments, including one ongaku) is familiar with his previous venture - Micrex and he recommended me to go for it even though no one in my country seems to own one.

So, I guess this thread is going to go on for along time to come.

I was under the impression that Supratek had folded some while back- maybe a year ago or more. If they are back, I certainly hope that the new product does not have the same construction technique of using glue to hold components in place (as this represents a significant fire hazard).

Kevin Covi is a name I have seen before though- I am sure he knows better than that.

It's interesting to hear Supratek is taking orders.
Maybe there is a hope, Mick will pay me back from the proceedings.
I have to admit- my hopes have faded quite a bit.

Atmasphere, his website did not state he is closing shop. Perhaps, he wanted to quit but didn't do it or just doing it on small scale. BTW, which parts were glued together? The Chrome plat? That's normal and sometimes it is also possible for the customs to rip off to check them and glued them back. I once received Koala bears from Australia all ripped apart by customs for inspection.

Maril555, I am sorry to hear your unfortunate situation. Are you still having the Amp?

Mabil555, I just read all your earlier posts and found the answer to my question.

Chelvam, I've seen photos of the insides of 2 Suprateks (one photo is in a 6moons review). In both, the filter caps in the power supply were not secured by any hardware, instead were simply glued to the inside of the unit. This is a Bad Idea even if you are doing a DIY project. One drop in shipment (or otherwise) and you have a shock and fire hazard situation.

I am not aware of any of the parts coming loose from any inmates that own Supratek. Opened mine up to upgrade some caps and all was intact. The caps I replaced should not have come loose in shipping unless the unit was really banged around meaning probably damaged. It took some effort to remove the glued caps. I don't see them coming loose. If you were to buy one used as it looks like not to many are being made now, it wouldn't be a bad idea to open up the bottom and make sure everything is tight. I used "goop" to glue in the new caps. They are not going to move with this stuff! It appears that Supratek is still up and running on a smaller scale. Good to know. Love my preamp.

I too used Goop to secure my Solen PP filter caps when I replaced the electrolytics in my Chenin, but I also made a steel bracket that I screwed into the wooden side of the unit just in case. Do I think the Goop will come loose? No, but a little extra safety doesn't hurt.

One of my Syrah's phono battery holders was glued, and had come loose. Thankfully it was just the battery case and not a power supply cap...

It sounds like the original glue used is pretty strong. The concern I would have as a manufacturer would be what happens a few years down the road? The glue is aging, and also subjected to heating cycles. You know that it will degrade in due time. It is guaranteed that no matter how good the preamp sounds, if it is found responsible for a heart attack due to shock or burning someone's house down, the brand loyalty will mean nothing during the lawsuit.

It always amazes me, when somebody like Ralph (Atmasphere), who makes amplifiers for a living, makes a statement regard. proper building technics, in this particular case about why one should NOT use glue to secure parts to the chassis, there always be the other guy, with no professional experience of building anything, who would argue the opposite point, and will support his argument with a ridiculous and irrelevant statement, like " I do it all the time (use glue), and haven't had problems yet".
Puts other opinions of that same guy into a certain perspective, doesn't it?