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MF X-Can V2 tweaks - Page 2

post #16 of 71
Thread Starter 
Quote:
Originally Posted by Juergen
You mention that the cap upgrades greatly improve the stock V2 but those Mullards do alot also (so I have heard). I replaced my stock valves with the Sovtek 6922s. They were really inexpensive. I can't seem to find Mullards for less than $100 US a pair. I might power up my V2 tonight. I haven't listened to it in about a year
That's a really cool looking knob Juergen it'll look great on your V2 for sure

I love the sound of the Mullard valves and in my valve comparison they came out on top at the time. I will be trying some more valves and will include them on that page.... just taken delivery of some brand new NOS Military specification ultra low noise 6N23P-EV triodes made by the Reflector Corporation, (Saratov) and they run for around £5 for a matched pair which certainly is as cheap as chips! They come in sealed boxes direct from the factory and each valve has its own data sheet written in Russian...... I'll give them a try later on and can only hope they sound as good as the Mullards (you never know!) they certainly look very well made and a little birdie in the know reckons they are very similar to the Sovtek valves...... off to roll them in now and will report back later.

The guy I used to buy the mullards from (Sean Redshaw of highendaudio.co.uk) can no longer source them and he now uses electro harmonix valves in his amps instead of the Mullards and he swears by them...... I've got a pair of them on their way to try so will also include them in the comparison.

Valves certainly do play a big part in the V2 and can influence the sound greatly..... the stock Jan Philips 6922 are "OK" but there are much better sounding valves out there, it's just a case of finding them..... fingers crossed hope these £5 a pair jobs will sound good.
post #17 of 71
Hey Pinky,

Have you ever thought of re-casing a V2? I had been thinking about re-casing my PPA (http://www4.head-fi.org/forums/showp...68&postcount=6) and adding a STEPS psu (I have a bare pcb from Tangent). I have yet to see a re-cased XCan V2 (nothing against the stock enclosure, it's quite unique). I have been admiring some of the DIY valve amps and think it might be pretty cool to have an amp with exposed valves. I know it has nothing to do with the 'sound' but like I said wouldn't it be COOL! Plus it would give me more room for future tweeks.
post #18 of 71
Thread Starter 
Quote:
Originally Posted by Juergen
Hey Pinky,

Have you ever thought of re-casing a V2? I had been thinking about re-casing my PPA (http://www4.head-fi.org/forums/showp...68&postcount=6) and adding a STEPS psu (I have a bare pcb from Tangent). I have yet to see a re-cased XCan V2 (nothing against the stock enclosure, it's quite unique). I have been admiring some of the DIY valve amps and think it might be pretty cool to have an amp with exposed valves. I know it has nothing to do with the 'sound' but like I said wouldn't it be COOL! Plus it would give me more room for future tweeks.

I've thought about recasing it but I like the look of the X-can so probably won't recase it. If you rehouse yours you'll be able to fit a lot more capacitance to the PSU which has proven to be very worthwhile indeed... you'll also have room to do lots more should you want

On the subject of tweaks I see Antony Michaelson has been up to his old tricks again spouting off how valve rolling is BS and how potentiometers like the RK27 are just audio jewelry etc. He was once quoted as saying "capacitors don't make any difference to the sound, cheap ones are as good as expensive ones" great marketing stuff indeed, specially if his philosophy is "cheap components sound best"

This V3 review may be of interest where he discusses valves and pots. He forgets to mention that the V3 is pretty much identical to the V2 except for the ALPS RK27 pot and the 2200uF PSU capacitors (instead of the 1000uF caps in the V2) hmmmmm........

Maybe I've got different ears from Antony Michaelson....... rolling in different valves and swapping out the caps makes an absolutely incredible improvement to the sound. It is night and day and certainly not subtle.. for him to say that all caps and valves sound the same is total BS IMO and his philosophy is probably based more on cost than it is on performance...... I've heard from over 100 people who have changed the valves and either fitted more capacitance or a different brand of capacitor and every last one of them reports "stunning improvements" I'd love to get Antony Michaelson strapped onto a chair blindfolded and get him to listen to stock V2 and V2 with more capacitance and different valves...........

On the subject of valves........ I've found a valve which sounds better than the Mullards and only costs about $10 (£5) for a brand new pair, I'll have a good old listen today before confirming this but so far these are pretty much streets ahead of other valves I've tried..... ethereal detailed sound, instruments / performers presented in a holographic soundstage, rock solid imaging, liquid mids, detailed highs, energetic fluid "tuneful" bass. Top class sound indeed
post #19 of 71
Quote:
Originally Posted by PinkFloyd
...... I've found a valve which sounds better than the Mullards and only costs about $10 (£5) for a brand new pair, I'll have a good old listen today before confirming ...
I can't stand the suspense....
post #20 of 71
Thread Starter 
Quote:
Originally Posted by Juergen
I can't stand the suspense....
No real suspense they're 6N23P-EV triodes made by the reflector corporation and cost £5 for the pair (NOS).

Let's just say, the Mullards will not be going back under the bonnet and I've ordered a few more pairs of these as they sound "that" good.. totally took me by surprise and they're nothing short of a bargain
post #21 of 71
Quote:
Originally Posted by PinkFloyd
No real suspense they're 6N23P-EV triodes made by the reflector corporation and cost £5 for the pair (NOS).
That's a great price. The cheapest that I can find them is from http://thetubestore.com/rus696h.html for $20 each. That would be close to $50 US after shipping for a pair. Still a great price compared to the Mullards but not exactly loose change
post #22 of 71

Some progress

Well, I've made some progress....

I completed my utilitarian style power converter, basically a 120 to 12 Vac converter to power the X-CAN. The only real twist is I'm using a 30 VA toroid transformer, and added a DC blocking filter to it. See the electrical schematic for a Bryston 4BST to get an idea of what I'm talking about. My new problem is that the fuses keep blowing due to in rush current. I'm currently looking for either slow-blow metric fuses, or an NTC thermister.

In order to determine what the ground scheme is about, I disassembled the X-CAN and traced the power supply board, and partially traced the amplifier board. The body of the power jack is connected to the chassis.

The power supply appears to be a text book voltage doubler, but has what looks like a voltage regulator on the output. However, the transistor is very small, so it can't be regulating all that much. Anybody happen to know what part that is? The part number printed on the body doesn't cross to anything. I haven't put a scope on the output yet to determine voltages, noise, etc.

Although I haven't figured out the circuit topology for the amplifier, yet, I did learn that there's a 10uF electrolytic cap on the input, and a 220uF bipolar electrolytic cap on the output. If I were to begin replacing caps, I think I would begin here. Unfortunately, MF didn't provide a lot of real estate around the 10uF caps (they are very small) to accomodate a metalized polypropylene cap.

Also, this amp appears to be a hybrid output, with TIP110 and TIP115 Darlington pairs in the output stage. I would bet the power rating could be increased by attaching heat sink(s) to the TO-220 cases.

Regards,

Rob
post #23 of 71
Quote:
Originally Posted by weinstro
My new problem is that the fuses keep blowing due to in rush current. I'm currently looking for either slow-blow metric fuses, or an NTC thermister.
I used a 30VA Hammond. I'll take a look tonight at the fuse. I think my first fuse was rated too low so I blew a couple then bumped up the value or changed type (I can't remember).
post #24 of 71
Thread Starter 
250mA 20mm time delay fuse should be fine with 30VA. I've used a 250mA with loads of X-can PSU's and they've never blown.
post #25 of 71
30VA / 120V = 250 mA (full load current). Of course it won't be anywhere close to being fully loaded but as mentioned, the inrush current is the issue. The time delay generally takes care of this. You still may need a larger fuse. Pinky, you run at 240V? That would be 125 mA full load at 240V. I suggest buying a few different ratings, maybe 250mA & 500mA and starting low.
post #26 of 71
This is a nice thread. There has been way too little attention to this classic the last years. It is still a frequent object on the auction sites and it does still fetch good prices as well as very satisfied new users.

I am sitting here with this X-10D (v2), and with all those pictures and excellent explanations to suitable modifications of this MF line, the water is running in my mouth. Perhaps I should heat up the solder iron after all...Thanks Pinkie!
post #27 of 71
Quote:
Originally Posted by Juergen
30VA / 120V = 250 mA (full load current). Of course it won't be anywhere close to being fully loaded but as mentioned, the inrush current is the issue. The time delay generally takes care of this. You still may need a larger fuse. Pinky, you run at 240V? That would be 125 mA full load at 240V. I suggest buying a few different ratings, maybe 250mA & 500mA and starting low.
That's the maximum continuous current rating for the transformer. However, the X-CAN actually draws 130mA with a wall voltage of 119 Vac, according to my current meter. A 200mA slow-blow should be adequate. If you go much larger than 250mA, than the transformer is protecting the fuse at some points in the current vs. time curve.

Even after accounting for transformer efficiency, ballast loads, etc., the power draw of the X-CAN is much higher than the 12Vac @ 500mA implies.
post #28 of 71
Quote:
Originally Posted by Juergen
I used a 30VA Hammond. I'll take a look tonight at the fuse. I think my first fuse was rated too low so I blew a couple then bumped up the value or changed type (I can't remember).
With a 500mA fast-acting fuse, my power converter is simply a fuse tester.

Raising the rating to 750mA works, as I can cycle power on/off without popping the fuse. I'd still prefer to have a 200-250mA slow blow.
post #29 of 71
Thread Starter 
Quote:
Originally Posted by weinstro
Well, I've made some progress....
Cool

Quote:
Originally Posted by weinstro
I completed my utilitarian style power converter, basically a 120 to 12 Vac converter to power the X-CAN. The only real twist is I'm using a 30 VA toroid transformer, and added a DC blocking filter to it. See the electrical schematic for a Bryston 4BST to get an idea of what I'm talking about. My new problem is that the fuses keep blowing due to in rush current. I'm currently looking for either slow-blow metric fuses, or an NTC thermister.
250mA 20mm slow blow is your friend in this application

Quote:
Originally Posted by weinstro
The power supply appears to be a text book voltage doubler, but has what looks like a voltage regulator on the output. However, the transistor is very small, so it can't be regulating all that much. Anybody happen to know what part that is? The part number printed on the body doesn't cross to anything. I haven't put a scope on the output yet to determine voltages, noise, etc.
TR1 = ZTX653 (NPN) and TR2 = ZTX753 (PNP) are those the two you're referring to?

Quote:
Originally Posted by weinstro
Although I haven't figured out the circuit topology for the amplifier, yet, I did learn that there's a 10uF electrolytic cap on the input, and a 220uF bipolar electrolytic cap on the output. If I were to begin replacing caps, I think I would begin here. Unfortunately, MF didn't provide a lot of real estate around the 10uF caps (they are very small) to accomodate a metalized polypropylene cap.
The 10uF input caps can be removed if your source has no DC on its output. Alternately, the 10uF electrolytics can be replaced with film caps or bypassed with film caps. The 220uF non polar output caps will block any DC on the output (if any) and could probably be dispensed with if the offset is very low...... 470uF - 1000uF would be a better value here, especially with low impedance 'phones, I'm using 1000uF Non polars and it improves the bass no end.

Quote:
Originally Posted by weinstro
Also, this amp appears to be a hybrid output, with TIP110 and TIP115 Darlington pairs in the output stage. I would bet the power rating could be increased by attaching heat sink(s) to the TO-220 cases.
Worth a try
post #30 of 71
Quote:
Originally Posted by PinkFloyd
TR1 = ZTX653 (NPN) and TR2 = ZTX753 (PNP) are those the two you're referring to?
Looks like a winner. Thanks. But, these have really small power ratings - only 1 W. The whole X-CAN draws about 11 W.

Quote:
Originally Posted by PinkFloyd
The 10uF input caps can be removed if your source has no DC on its output. Alternately, the 10uF electrolytics can be replaced with film caps or bypassed with film caps.
Most days, I use a portable Philips or iRiver CD player. No idea what the dc offset is. Could be measured, though....

Quote:
Originally Posted by PinkFloyd
The 220uF non polar output caps will block any DC on the output (if any) and could probably be dispensed with if the offset is very low...... 470uF - 1000uF would be a better value here, especially with low impedance 'phones, I'm using 1000uF Non polars and it improves the bass no end.
That might be something to try, bypassed with a film cap. Any idea what the value of the feedback cap is?

Regards,

Rob
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