This is the chassis. I am actaully quite impressed with it. Especially for the price:
Chassis
I bought it because I like the bulky heatsinks That match the old Threshold. Also, it is only a little smaller than the Threshold. One thing to keep in mind that the nearly 3" deep heatsink makes it so you have a little less internal width.
Chassis
I bought it because I like the bulky heatsinks That match the old Threshold. Also, it is only a little smaller than the Threshold. One thing to keep in mind that the nearly 3" deep heatsink makes it so you have a little less internal width.
Nice! Not the one I was thinking, but I do have the little 4U brother of this one. I was also pleased with mine.
I'm happy camper, having Modushop sorta locally
I mean, on same side of Big Splash
My routine is - what you see on their site for price, add 10% IVA ('Talian VAT), obviously they boxed up good contract with Fedex so shipping is more than decent price for entire Europe and then (due to fact that my Tribe is not in League of EU tribes) it is less cumbersome for me to pay my guy 10% of package price, to get it smuggled from his address in EU Tribes Fence - in my Tribe Fence, than coping with my Tribe Customs
Life is good, even if complicated ..... once when you realize that you need to give some greenies to worry less
I mean, on same side of Big Splash
My routine is - what you see on their site for price, add 10% IVA ('Talian VAT), obviously they boxed up good contract with Fedex so shipping is more than decent price for entire Europe and then (due to fact that my Tribe is not in League of EU tribes) it is less cumbersome for me to pay my guy 10% of package price, to get it smuggled from his address in EU Tribes Fence - in my Tribe Fence, than coping with my Tribe Customs
Life is good, even if complicated ..... once when you realize that you need to give some greenies to worry less
Yes, Modushop is a no-brainer for a lot of people. I am sure if someone sent the drill pattern to them, they would be accommodating in predrilling everything for you.
Attached are some pics of the boards. Hopefully they are clear enough to help someone.
The last picture is of the pair in Q1 and Q2. It goes, Q1, mica, heatsink, mica and Q2. I mounted the resistor that goes in that location onto the bottom of the board.
Also, something interesting is that some songs that sounded not so detailed before actually weren't being reproduced in enough clarity to bring out the finite details.
Attached are some pics of the boards. Hopefully they are clear enough to help someone.
The last picture is of the pair in Q1 and Q2. It goes, Q1, mica, heatsink, mica and Q2. I mounted the resistor that goes in that location onto the bottom of the board.
Also, something interesting is that some songs that sounded not so detailed before actually weren't being reproduced in enough clarity to bring out the finite details.
Attachments
As in the bitrate isn't high enough for the amplifier 😉
I have a bunch of these connector sockets in gold. I am wondering if you could put them in place of the resistors that would need to be chabnged for SET. Skimming the schematic briefly, They would need to be in R44-R46 and R47, R50 to pull and install things. Leave the SET transistors in place assuming they would be completely out of the circuit without the resistors. Maybe one for the BFR too.
What do you think?
What do you think?
if you take a look at any of my T-Bed adventures, you'll see exactly those in few/several locations, pictures taken while fine-tuning construction or/and trying different arrangement
after experimenting, I'm usually lazy to pull them (sockets) and install resistors normally, so I'm just soldering resistors ditto in sockets
I did mention use of these in several occasions, but time taught me to better avoid involving too much variables, which would be the case if I include these in kits (and they're cheeeeeeeaaaaaaaap, practically pulls from IC sockets or cut from stripe)...... just another ( in fact, few of them ) positions demanding occasional question(s)
exactly from same reason, when one pcb is serving more than one arrangement/amp ( as is case here - 3 amps in all), I'm always publishing agregate schematic and then dedicated schematic for each of amp arrangements, just to avoid, as much is possible, any dilemma
in short - use them if you need them; it is absolutely in line with real DIY Spirit
after experimenting, I'm usually lazy to pull them (sockets) and install resistors normally, so I'm just soldering resistors ditto in sockets
I did mention use of these in several occasions, but time taught me to better avoid involving too much variables, which would be the case if I include these in kits (and they're cheeeeeeeaaaaaaaap, practically pulls from IC sockets or cut from stripe)...... just another ( in fact, few of them ) positions demanding occasional question(s)
exactly from same reason, when one pcb is serving more than one arrangement/amp ( as is case here - 3 amps in all), I'm always publishing agregate schematic and then dedicated schematic for each of amp arrangements, just to avoid, as much is possible, any dilemma
in short - use them if you need them; it is absolutely in line with real DIY Spirit
Very cool. I think I'll pull the amp apart and a month or so and give those a shot. Thank you 👍
Real nice XA252 build Mikerodrig!
I assume you didn't try SET mode yet and that's why the preparation for sockets in key locations. Can you give a few details about voltage, bias current and heatsink temperatures. I have the same chassis waiting in the wings..... 😉
Enjoy the music!!
I assume you didn't try SET mode yet and that's why the preparation for sockets in key locations. Can you give a few details about voltage, bias current and heatsink temperatures. I have the same chassis waiting in the wings..... 😉
Enjoy the music!!
Hey Vunce, absolutely. I will do a little writeup later on tonight. You are correct, I have not tried SET mode yet. The chassis is a good one. Especially for this project. I used these for the heat spreaders if you would rather tap through holes than bottom tapping:
https://www.ebay.com/itm/334665495273
https://www.ebay.com/itm/334665495273
Okay so I took some measurements.
I measured one of the MOSFETs, The heat spreader next to the MOSFET and then the heat sink on the outside between the fins in the direct center of the heat sink. My measurements are
Ambient room temperature: 16.9
Outside heat sink: 42
Heat spreader next to MOSFET: 42.9
MOSFET case temperature: 43.3
So this yields a Delta of 25.1° which is about right on target.
Bias across the current source resistors is 200 millivolts. The bank of three paralleled resistors come out to 1.1 ohms. From the way I understand it, .200v/1.1 ohms gives me 1.8 amps
I have a Antek AN-5428 which is way overkill. However, it is not much more expensive than say a 300va or a 400va. It has 28v secondaries which put me right at around 36 volts at the rails at full temperature.
I still have to wire the switch in as well as put in this snubber boards for the rectifiers. However, I have to be willing to turn it off first 😬
A couple notes about the chassis. It is a very good chassis for the price. There were a couple little spots where the anodizing had been dinged off, however they were in spots that didn't matter and again, for the price... Honestly I have not had chassis yet where that hasn't been the case.
Mine came with a lot of extra screws and no instructions which threw me off for a little bit.
The back panel screws directly into the heat sinks. There are these little aluminum bars that tie the top, front, back and the bottom together. Then there are two bars that tie the faceplate to the heat sink.
Once you have a big transformer in the way, you will likely not be able to get the bottom screw of the front corner block in. I don't really think that's a big deal though. What's a couple loose screws?
-----------------------
So I had some time to listen to it and compare this standard MOSFET version of the XA252 to my modded threshold. I would say that the bass on the XA252 is equally as strong, much more precise and faster. Bass hits are less bloated etc.
The threshold up until now, I considered a very detailed amplifier. Kind of my reference to compare to other amps as far as detailedness. How they present the soundstage and how they Make you feel the room that the musicians are in. The XA252 makes the threshold sound like an Aleph in regards to sugar. I like them both for different reasons. However, I think that the XA252 would be the more universally appreciated amp.
The threshold has a lush bold and more forward presentation. The XA252 has a more exact and further back presentation. The Threshold has this kind of bloominess in the lower mid to bass range that is really neat. It is a very romantic sounding amp. The XA252 is not as romantic sounding but is very easy to listen to.
Songs with rich tones like Sinne eeg's My Treasure sound enveloping on the threshold. The stand up bass is more around you. Her voice is rich. On the XA252, the stand up bass is front and center and you can hear the detail in her voice much better. It takes a lot of clarity to make it so that you can pick up enough on the overtones of a stand up bass to get a strong center image. On the XA252, You can hear Sinne's lips open before she sings and you can hear the bass creaking on the floor with more fidelity. The XA252 handles more complicated songs much better. Things like orchestras or large groups of musicians in general. The instrument separation is much better
Songs that have good recordings of hands hitting drum skins sound really neat on the XA252. It sounds great with the threshold but with the XA252 you hear more of the skin. With the threshold, I can hear the background singers very well and I can separate them from the singer and really zone in on them. With the XA252 I can hear the airiness in their voices and sometimes I can hear them breathe before singing. Things that decay like reverb or drum hits etc, stand out more with the XA252. Not only do you hear the reverb but you can hear the type of reverb more clearly. Really neat
I have a feeling that running the XA252 in SET mode may give you more of that romantic sound if that is what you're after. That'll be one of the next things I try.
The really cool thing about the XA252 is that the threshold has 20 output devices per channel and has about 80 watts class A with a pretty stout power supply. The Xa252 has two MOSFETs per channel and sounds equally as big but faster and exacting.
I know it's kind of hard to describe how things sound but hopefully this will give people some insight into at least my listening impressions.
One thing I will say, you're going to need a nice set of speakers to be able to really pick up on what the amp is capable of.
I measured one of the MOSFETs, The heat spreader next to the MOSFET and then the heat sink on the outside between the fins in the direct center of the heat sink. My measurements are
Ambient room temperature: 16.9
Outside heat sink: 42
Heat spreader next to MOSFET: 42.9
MOSFET case temperature: 43.3
So this yields a Delta of 25.1° which is about right on target.
Bias across the current source resistors is 200 millivolts. The bank of three paralleled resistors come out to 1.1 ohms. From the way I understand it, .200v/1.1 ohms gives me 1.8 amps
I have a Antek AN-5428 which is way overkill. However, it is not much more expensive than say a 300va or a 400va. It has 28v secondaries which put me right at around 36 volts at the rails at full temperature.
I still have to wire the switch in as well as put in this snubber boards for the rectifiers. However, I have to be willing to turn it off first 😬
A couple notes about the chassis. It is a very good chassis for the price. There were a couple little spots where the anodizing had been dinged off, however they were in spots that didn't matter and again, for the price... Honestly I have not had chassis yet where that hasn't been the case.
Mine came with a lot of extra screws and no instructions which threw me off for a little bit.
The back panel screws directly into the heat sinks. There are these little aluminum bars that tie the top, front, back and the bottom together. Then there are two bars that tie the faceplate to the heat sink.
Once you have a big transformer in the way, you will likely not be able to get the bottom screw of the front corner block in. I don't really think that's a big deal though. What's a couple loose screws?
-----------------------
So I had some time to listen to it and compare this standard MOSFET version of the XA252 to my modded threshold. I would say that the bass on the XA252 is equally as strong, much more precise and faster. Bass hits are less bloated etc.
The threshold up until now, I considered a very detailed amplifier. Kind of my reference to compare to other amps as far as detailedness. How they present the soundstage and how they Make you feel the room that the musicians are in. The XA252 makes the threshold sound like an Aleph in regards to sugar. I like them both for different reasons. However, I think that the XA252 would be the more universally appreciated amp.
The threshold has a lush bold and more forward presentation. The XA252 has a more exact and further back presentation. The Threshold has this kind of bloominess in the lower mid to bass range that is really neat. It is a very romantic sounding amp. The XA252 is not as romantic sounding but is very easy to listen to.
Songs with rich tones like Sinne eeg's My Treasure sound enveloping on the threshold. The stand up bass is more around you. Her voice is rich. On the XA252, the stand up bass is front and center and you can hear the detail in her voice much better. It takes a lot of clarity to make it so that you can pick up enough on the overtones of a stand up bass to get a strong center image. On the XA252, You can hear Sinne's lips open before she sings and you can hear the bass creaking on the floor with more fidelity. The XA252 handles more complicated songs much better. Things like orchestras or large groups of musicians in general. The instrument separation is much better
Songs that have good recordings of hands hitting drum skins sound really neat on the XA252. It sounds great with the threshold but with the XA252 you hear more of the skin. With the threshold, I can hear the background singers very well and I can separate them from the singer and really zone in on them. With the XA252 I can hear the airiness in their voices and sometimes I can hear them breathe before singing. Things that decay like reverb or drum hits etc, stand out more with the XA252. Not only do you hear the reverb but you can hear the type of reverb more clearly. Really neat
I have a feeling that running the XA252 in SET mode may give you more of that romantic sound if that is what you're after. That'll be one of the next things I try.
The really cool thing about the XA252 is that the threshold has 20 output devices per channel and has about 80 watts class A with a pretty stout power supply. The Xa252 has two MOSFETs per channel and sounds equally as big but faster and exacting.
I know it's kind of hard to describe how things sound but hopefully this will give people some insight into at least my listening impressions.
One thing I will say, you're going to need a nice set of speakers to be able to really pick up on what the amp is capable of.
Attachments
Last edited:
You explain the XA252 like many explain the XA25 ... which is a testimony to Zen's ability to engineering 🙂 and I would build right away If I could and I would build the balanced version.
it should be
Bias across the current sense resistors is 200 millivolts. The bank of three 0R33/3W paralleled resistors come out to 0.11 ohms. From the way I understand it, .200v/0R11 ohms gives me 1.8 amps
later reworked to have groups of 5 paralleled 3W resistors, so one can use either 5*0R56/3W or 3*0R33/3W , which gives me more leeway when buying them in quantity, regarding availability and/or price
and that sez - in Summer you'll have 52-55C at sinks
depending how you're going to feel about temperature of case inside, you can make nice Babysitter, and be happy - knowing that caps are not exactly cooking
no need to worry about Iq ( rock solid) and pucks temperature, for these 55C is just idle warm
Yes, yes, the world of no degeneration is new to us all, even papas article is only a few years old.
Unfortunately, I am allready so degenerated this new tech merely impedes further worsening of the situation
Unfortunately, I am allready so degenerated this new tech merely impedes further worsening of the situation
What is your reason for wanting the balanced version? What speakers do you have?
I currently do not have any speakers and live in a small apartment. I am in no position to build anything. I plan on building a house a few years from now with a full media/home cinema/music room, so I have to wait.
Beyond that, balanced operation is just that, balanced. Both speaker polarity's are actively driven and ground is not references, just like for PASS XA30.8 and up and some of Yamaha's better A-S amplifiers (Circlotron), In a world where the electronics and circuits are so fine tuned, there is only one level left... balanced operation 🙂 .. Its not a law and everyone is free to do as they please and yes, I will build a std XA252 first such that I can compare. Too bad it isn't soon. I will however pick up a bunch of pucks and JFets this summer such that those are secured ... and sorry for rambling.
Beyond that, balanced operation is just that, balanced. Both speaker polarity's are actively driven and ground is not references, just like for PASS XA30.8 and up and some of Yamaha's better A-S amplifiers (Circlotron), In a world where the electronics and circuits are so fine tuned, there is only one level left... balanced operation 🙂 .. Its not a law and everyone is free to do as they please and yes, I will build a std XA252 first such that I can compare. Too bad it isn't soon. I will however pick up a bunch of pucks and JFets this summer such that those are secured ... and sorry for rambling.
Hey, I may have rambled on too much so... Speaking of which, if you eventually build both, it would be interesting to hear your thoughts on how they sound. If you can design the dimensions of the room, see if you can manage the golden ratio L' x W' x H'.