kevin gilmore

Make sure you change out that electrolytic again, and throw the overvoltaged ones in the trash can. To everyone, power up the transformers on the bench to make sure you know how they are wired before you hook them to the boards.

So lets see, about 650 volts on a 450 volt cap. Yep that is probably going to cause it to get stinkin hot... And the regulator circuitry does not care, as it can handle 800 volts easy.

Actually the 2sc2240 would work just fine. But i was simulating absolute worse case. Lets say the current source on the top of the top input tube shorts, then the top tube shorts... Suddenly 250 volts on the cathode. Of course this has not happened yet, and is unlikely to ever happen. But i do wonder what would happen if just the tube shorted. This scenario would blow up the 2sc3381's anyway. And this is why i figured it would be easier to use the 300 volt versions. Which are still dirt cheap.

The simulation shows absolutely no difference between the 4 transistor current mirrors, and the single transistor circuit. Does need to be a 100 volt transistor however. Due to tube shorts, probably should be rated at 300 volts. Whatever the npn equivalent of the mpsa92 should work great.

just bought this, it will be here monday http://www.saeco-usa.com/en/products/household-automatic-machines/1/automatic/0/xelsis-digital-id/311/xelsis-digital-id.html replaces a 15 year old saeco magic deluxe that is finally beginning to show wear.

posted for linear http://gilmore.chem.northwestern.edu/servochange.jpg

So a couple of people have asked for a discussion of the design elements of the T2, and any observations and improvements that are possible. So as not to polute the T2 build thread, which is already seriously poluted, the discussion of T2 design elements, including kerry's dynamic amp should go here. doug wadsworth (wadia) should be stopping by soon Actually, a moderator change the thread title to discussion of the T2, and other circuitry as we see fit including but not limited to my other designs and shunt regulators and stuff like that etc...

Well with a set of linear supplies, it tips the scales at 800 watts of heat. I would say its kinda hot

I did pay extra to have the boards electrically tested. But who knows what really happened. I just don't see how the electrolytic can get hot unless its backwards, or over voltage. No matter what kind of load it sees. As far as kerry's amp... Turn up the bias current to 2 amps per leg. Replace the output fets with the SiC fets that nelson is using. BIGGER HEATSINKS. And my test bench thing works absolutely great with +/-24 volt power supplys, and does about 30 pure class A watts into 8 ohms. Currently using switchers for the power, and each amplifier puts out about 200 watts of heat. Sounds really nice into vintage VOTT's. REALLY NICE. OK, so VOTT's are really more like 12 to 16 ohms...

i'm pretty sure a while back i said in the range of $4500 to $5k. Looks like i was right on the money If i were you guys, to avoid getting ripped off, i would wait till someone reliable has them in stock for sale. elusivedisc, audioadvisor, woo audio...

has to be the cap or diode bridge. because it still makes the right voltage. my bet is the cap has the + and - mislabled. Caps get very hot this way.

And likely done on a very large bellows camera with a 6 x 10 inch plate. They don't do it that way any more. Too bad.

pretty sure the default pot is 50k. So use a series 25k resistor. Should work for any solid state source, but may not work well with a source that has a tube output stage. An input transformer won't help with the impedance, but will cause other grief. Also notice that very few pots actually go all the way to zero, so there will be some minimum volume. You are still going to have to punch holes in the back panel for the xlr jacks.

http://gilmore.chem.northwestern.edu/srm323aorig.pdf balanced no problem. But you would have to change out the input pot, or bypass completely.

5. Anonymous but it should be obvious who this person is.

I was wondering about all the flipped parts myself, as i have an identical unit with the same revision of the boards. No flipping on the pins of the regulator. No crossing of the diodes on the input fets either. Clearly the +15 is not being regulated with the regulator wired like that. Measuring that voltage would give you the answer, likely +18 or more and unregulated and filled with hum.

The power transformer has clearly shifted in shipping. This needs to be fixed first. If the bolt is touching the inside of the transformer, all sorts of ground current and vibration is getting into the chassis.

posted on behalf of linear http://gilmore.chem.northwestern.edu/t2schemip.pdf http://gilmore.chem.northwestern.edu/t2schemop.pdf http://gilmore.chem.northwestern.edu/t2schems&b.pdf http://gilmore.chem.northwestern.edu/mjt2a.jpg http://gilmore.chem.northwestern.edu/mjt2b.jpg http://gilmore.chem.northwestern.edu/mjt2c.jpg http://gilmore.chem.northwestern.edu/mjt2d.jpg

if you look at the insides of the original, the 22k resistor was mounted on the backside about .5 inch from the board so that you could put clipleads on it to adjust.

i'm sure inu could translate it. but i know a couple of people at work that can do it too. maybe in the next few days. really, these things are just the srx circuit with an extra tube stage for more gain so that you can have more feedback. 50ca10's are probably impossible to get, as are the sockets, 6ra9's might be easier. Still nothing wrong with 6ca7's. But the resistor plate loads are guaranteed to do the same thing that has happened to a bunch of the es1/es2's when the output tube lets go. So much better idea to replace with current source. Then make sure you have adjustable bias on the output tube. Pretty soon you end up with the modified singlepower schematic. There are errors in the schematics, in the 3rd one, "B" is actually -440 volts. With the 50c10's you can do adjustable self bias without an additional negative power supply.

inu sent me these which are variations on the srx circuit. http://earsp.web.fc2.com/log/stax-r/stax-r-3.pdf warning, the 1150 volt version is only for those that really know what they are doing. And obviously the output caps need to be rated for 1200 or more volts. With respect to high voltage electrolytics, and also mylar caps, a resistor across the cap is pretty much required at all times. Even if you discharge the cap, and then remove the resistor, the capacitor will self charge, usually to very dangerous voltages. The higher the rating on the cap, the worse it gets.

I still listen to 2 cd's, sometimes more every day when i get home. right after i let the dogs out. sometimes with added liquid refreshment.

Depends on which version of the power supply board you have, but 24 volt zeners across the gate to source prevents the pass transistor from blowing up. The fairchild part used in the T2 is way better anyway.FQPF8N80C or FQP8N80C and they are cheap. Probably still out of stock at mouser, so get them at futureelectronics.

In all 3 cases above, its the current source that is the problem. Has to have 1000 volts compliance. This requires stacked pnp's similar to the original circuit. And the capacitor (c1,c2,c3) necessary to stabilize the circuit is going to affect the quality of the current source at higher frequencies. the devil is in the details. Build it and test at appropriate voltages, then let me know. The SiC devices work great on paper. In practice, there are all sorts of other issues because they don't like to work at low currents for example.

Well i'm 30+ lbs LESS buddha than i was when i started this project 19 months ago. You can be pretty sure that if you do a spice analysis, and the results are poor, then if you actually build and test the device, it will be poor or worse. But a good spice result does not necessarily translate to a wonderful sounding amplifier. The ixys10m90s devices sound just fine, but blow up at about 925 volts. Rather consistently. Anything else at 1000 volts does not sound as good. Replacing the 2sc3675's with 2sc4686's does in fact work fine, and sound the same but you have to turn up the bias currents a bit. Same thing with the active batteries. The open loop gain is plenty high already. Anything over 15db of headroom seems to make lots of different amplifiers sound bad. Many of the portable opamp based toys with 50db+ of extra gain are a good example. The slew rate is more than sufficient with a rise time of under a microsecond large signal. Replacing the input tubes is still open to discussion.