| Nordic |
I am trying to guage interest in a groupbuy for Carlos' (Destroyer X) second version of his DX amp.
Rated at about 100W @4 ohms
and 50W into 8 ohms...
This is not the destructive point however, only the point at which distortion becomes more.
Not being able to make paypayl withdrawals presents me with a bit of a problem, so I needed to make enquiries into geting a merchant acount to deal with credit card payments on a secure basis...
This means that I will not be able to produce the boards unless there is good interest...
Boards will be provisionaly (I still have to go check their production plant out) made in South Africa. Which will provide a more stable price, as any increase in the dollar would otherwise push sales price and production costs into the wrong direction to make it viable...
Construction is single sided, with solder mask and silkscreen.
Prices are estimates as there may be hidden costs to me... so keep anothr $5 or so in the back of your head.
Quoted as stereo pairs i.e. 2 channels
total production 10 sets +-$30 per set
total production 20 sets +-$22 per set, which is lower than the qoute from Olimex, as well as saveing the shipping cost and time from there to here, and back to you
Resistors exluding the 3 power resistors can be provided at a dollar or 2, saveing you to stock up on unused components.
Here is an example of one channel etched at home...
Total size for 2 channels is 1 eurocard... i.e 10cm x 16cm (4" x 6 1/4")
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| Ed LaFontaine |
| I am interested in at least 1 set. I would also be willing to distribute boards from my location in Kentucky to any point on the continent where some economy in shipping would be realized. |
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| Jack C. |
I am interested too : 1 set.
Many thanks
J |
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| atiq19 |
Nordic,
Can I have one?
Regards
Atiq |
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| Nordic |
| if you mean 2 channels, then sure... we have to first get to the 10 board breakeven point... so we need 7 more takers... but its only been a few hours now... |
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| atiq19 |
Nordic,
Two channel pls.
Cheers.
Atiq |
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| konkret |
Hello Nordic,
can you please put me on your list?
I am interested in 2 channels.
Thanks!
---------
konkret |
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| RKH |
I'm in for a stereo set
RKH |
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| Nordic |
First 6 guys.. wonderfull!!!!!!
Come people, sign up, this is an incredible sounding amp.
You will be under no obligation until we have enough takers and have been asked to confirm. |
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| Nordic |
| 7th in via e-mail...... come guys, aim for 20...... |
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| Harry3 |
Hi,
I will buy one stereo pair and if the volumes increase and the price drops I will buy another pair.
Thanks |
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| Nordic |
So far we have potentaly accounted for 8 sets... If we can get another 7, pricebreak comes down to about $25 a set allready...
The amp will work well over a large range of supply voltages... just varying the zeners...
It can be built with or without capacitance multiplyer, produceing about half a farad per channel.... or these transistors can be omitted and bypassed with simple resistors, if that is your fancy...
Constructors will be given A4 size schematics, layout overviews, and voltage measurement points for faultfinding, So no advanced knowledge is required...
Total BOM cost exluding the 2 output transistors and their 2 decoupling elcos (2200uf -10000uf 50V 25mm or less diameter)...
was about 112 Rand...i.e. about $15... so not terribly expensive as far as these things go....
The last one I built, only used loosely matched (multimeter hfe) transistors, in the input pairs... with no matching anywhere else...
and still only has an offset of about 1mV.
So please add your name, noone is under any kind of obligation until we proceed to the second stage, where I have to fund this from my pocket...
Thank you for your time.
Nico
P.S. Thanks Ed I got your mail...or was it Bongo's :whazzat: |
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| Ed LaFontaine |
| quote: | | P.S. Thanks Ed I got your mail... |
Just let me know...
That was from the Ed in me. Mongo's fingers are like clubs. He gets no enjoyment with an iron in his hands. He has found out it will burn. The screams can be heard out in the garden, to say nothing of the tables and chairs to be replaced. :bawling: |
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| maxlorenz |
Hi Nordic,
I am interested in every outstanding, low cost amp, specially if it is Destroyer's X amp :D
BUT, first I have to read +3500 replies that the thread now has! Or better, read DX amp description at Greg's website ;)
(OK, my wife is already mad at me so a couple more boxes won't hurt :clown: )
Cheers,
M |
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| RKH |
Just to keep things going, if this all goes, i'll likely get 2 sets (4 boards).
Tell your friends, build an amp for your friends ... let's get to 30 |
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| meanman1964 |
Hi Nordic
Count me in for 1 set.
Konkret, please contact me. |
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| Nordic |
Hi Max, Like Greg I will put up a website shortly.
The circuit is a later version than the one on Greg's site...
Glad to see we are up to eleven guys (and girls) after so little time...
I have no hesitation in recommending this amp. It is extreme value for money... will run circles around any chipamp... and I mean equater sized ones... I have built one or two headphone amps in the past that came close to seperating singers from background singers like this... in fact just sitting infront of one speaker (plugging it in) I was amazed at how the sound seemed to beam infront of the box, placeing the instruments in clearly defined levels from back to front...
Then my wife, who had to climb over the mess for two weeks, while I took over the living room, started handing me CD after CD... all grumbles about the mess forgotten... and tonnes of praise. |
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| Westley |
Hi Nordic,
Please count me in for 2 sets (4 boards). Thanks,
Westley |
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| konkret |
Hi meanman,
as a new member of diyaudio.com
I do not have access to other member e-mail addresses yet,
so I cannot contact you this way.
Since you should not have this problem,
please do not hesitate to contact me via my member e-mail address.
Cheers,
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konkret |
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| meanman1964 |
| quote: | Originally posted by konkret
Hi meanman,
as a new member of diyaudio.com
I do not have access to other member e-mail addresses yet,
so I cannot contact you this way.
Since you should not have this problem,
please do not hesitate to contact me via my member e-mail address.
Cheers,
----------
konkret |
yOU CAN MAIL ME PATRICK.ROVERS@SCARLET.BE |
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| dudaindc |
Hi Nordic
Please count me in for a stereo set.
(Pending final costs I may increase that...)
Cheers! |
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| Harry3 |
Hi,
What is the pitch for the plastic caps eg 100nF?
Hopefully there is provision for 5 and 10mm pitch on the PCB.
Also is the spacing for the resistors wide enough to take the Vishay RN60D series resistors?
Regards
Harry |
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| Nordic |
Hi Harry
I am not sure, but I believe those resistors are larger than the 7mm pitch of standard 1/4W metalfoil resistors. The witdth should not be a problem, as few resistors are "blocked in", alll resistors on the board are 7mm pitch, except the 3 power resistors which were spaced for non inductive R's, the 2 47R resistors at the diff pair also allows for 9mm pitch and input resistor is a 5mm 1/8W jobby (space constraints). In fact I mounted my input cap and this resistor "offboard" in my unit to allow for larger input caps... you can simply solder a 180R resistor to the positive pin of the input RCA socket...
To keep size of PCB (cost) and inductances low, I had to minimise traces, and in the process, component sizes....
Trust me, there is not a single "audiophile" component in my box, and it sounds better than anything, I have had the honour to listen to... Small caps are all 5mm pitch... you ca fit a mica cap in the space provided for the Cdom cap... I did this in mine...
If you'd like to start stocking up, you will need 20 x 100nf caps if you also want to bypas elcos... else you will need 12 of those caps for the 2 channels....(I can provide these at a cost of about $2 as they cost me only about 9 south african rand + VAT) Same type as provided with the Twisted pair Kits, not sure ofthe brand... they are little yellow caps, they work well.
I can also provide the resistors at about the same cost... there are about 50 resistors between the 2 channels...
Welcome to the new faces, we are at 13 sets (26 boards) after just one weekend... |
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| AndrewT |
Hi,
0.28inch (7mm) is very small.
The normal minimum pitch for low watt resistors is 0.35inch (8.9mm). Most PCBs use 0.4inch or more for minimum resistor pitch.
When space is available I always recommend at least dual pitch for as many caps as possible. But you are excused when PCB space is scarce. |
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| Nordic |
I have seen the larger resistors RS sells a .333W unit in this size..., but 7mm pitch worked just fine... legs take a standard 90degree corner straight down the hole... with no unnessecary leads.. The issue is to not go to a larger PCB size... without going for miniature parts...
I have constructed 2 units with no construction problems up to now.. did get the idea to provide holes for a BG or other NP elco type input caps though...
I know there are those who believe in "audiophile" parts, but Carlos made me experience for myself that topology means more in the big scheme of things... I still believe in nice input caps though (big fan of Ampohm brand), but without fast swapping AB, I will not be able to say wich one I am listening to...
I didn't have any more nice large film caps to aid in comparison listening, will get a few diffirent ones of e-bay again... and I like my chipamp best with the ampohm jobbies... so I settled for cheap hitano non-polar 10uf cap to get the amp boxed again, and the livingroom cleaned up.....I would never have believed this cheap cap can sound so "good" |
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| dw1narso |
Hi Nordic,
count me in for a stereo channel... (a PCB pair, right?)
I would be interrested to get as many parts as possible from you too to build it, if you have surplus to sell...
(I'm living in a country of very little DIY offerings... even for some chips like LM3875 or audio transistors I have to order overseas...)
I'm contactable at david_winarso at yahoo dot com
Thanks,
---
David |
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| A'af |
sorry out of topic..
howmany LM you need from innerseas dwinarso, let me know... ;)
all the best,
a'af |
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| Greg Erskine |
hi Nordic,
1 pair of PCBs (2 off) for me thanks.
regards
Greg |
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| Nordic |
Wonderfull and welcome on board, sorry for not posting today... busy with my first SMD project... boy 0805 is alot smaller than I thought.... but, I have a large supply on a dead PC motherboard...
Only have to buy 2 values to complete the boards... I guess 1M and 470k, is not all that popular on PCs.. Maybe I should just get 1M and paralell 2 for 470k...
Managed to reduce my Pedja Rogic buffer to 3 x 4 cm...yep it will fit in a matchbox...but, I am dead tired now...
The group buy looks more or less like a sure thing at this point in time... I will let it run on till Friday, if noone objects, before finalising costs...
David we will sort you out partswise.... Let me know if you can get large electrolytics though say from 2200u to 10000uf under 25mm diameter, 50V.
Also if you can get 2sc5200 and 2sa1943 localy... else we will have to get you some off ebay... my regular suorce, sell fake ones... I can get real ones localy at good prices through the official distributor... but need to take a whole tube... will only happen if more people need those...
Welcome Greg... father of the DX amp layout...!!!!!! |
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| AndrewT |
| quote: | | Let me know if you can get large electrolytics though say from 2200u to 10000uf under 25mm diameter, 50V. |
Hi,
I can find upto 4700uF 63V in 25mm diameter.
I have not been able to find any 4700uF 50V as small as this, possibly due to the low profile high diameter that seems to be more common at this voltage.
To find any decent uF for smoothing and high local decoupling at under 25mm will be an achievement.
Any sources out there? |
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| Nordic |
Just a quick scan through RS Components catalog.
Panasonic TSUP 50V 4700 stock no. 3396865
Phycomp 50V 4700 sn. 4406777 both pretty expensive
enter 38 zar in usd, or whatever your currency is, in google
Looking at the datasheet TSUP is available in 10000uf 25 x 50, panasonic parts no. ECOS1HP103C. Not sure where one would source that...
I settled for jamicon 4700uf which I think were about 22mm...
Local price about ZAR14 + 14% VAT.
A 2200uf cap has a ripple current rateing of about 2A a 4700u 3A...
The output pair's caps I took out the spades and used over 30mm 10000uf caps there, but this is way overkill I believe...
I doubt any diffirence would exist if I used the 4700ufs all around.. especialy not with driving 8 ohm loads...
I think Carlos is useing even less...
The original DX specified 47uf... On Graham Maynard's advice I upped this to 10000uf on the output, with amazeing results.... so that concept... and the capacitors stayed with me...
P.S. 50VDC cap has 63VDC surge rateing.
I would say a reasonable supply voltage would be between 24 and 38VDC so there is the chance... that if you operate at the smaller scale, that you could even use say 35VDC caps
The board is at the limit for half a eurocard, and I am seriously thinking in hindsight, we might need to go for a 2oz copper thickness for the guys running 4ohm speakers. |
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| Ed LaFontaine |
Nordic,
For those traces which would really benefit with the additional copper thickness: What about using the "standard" copper and remove the solder mask from the traces that need an increase in capacity? Would the solder overlay be an acceptable, effective way to increase current carrying capacity? |
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| Nordic |
I'm pretty sure a solder layer is more than adequate, and you do have a fairly good idea there... I was looking into the wall of how will people get more current through there with the silkscreen on... Then I typed some number into a trace calculator... and it suggested I'd be OK provided I went for the ticker copper....
Your way sounds wonderfull... Into 8 ohm loads, this is not a worry....
P.S. no wonder I had such a battle with the SMDs last night... turns out they were 0603... only realised this when I picked up the remaining values in 0806 from the shop... these look much easier to cope with... allthough according to my multimeter I did OK last night... |
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| rellum |
Hello Nordic,
One set (2 boards) for me.
Regards,
Francis |
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| dw1narso |
Hi Nordic,
thanks for count me in... with also the parts to go with...
I'm little worry with the solder layer as discussed laterly...
My speaker go down to 3.9 ohm...
Would this be a problem?
REgards,
---
David |
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| Nordic |
No, Bongo gave Ed a good idea... we will place no soldermask over the large current traces... you can just apply a coat of solder to them...
... now Ed is going to claim he thought of it himself... |
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| Ed LaFontaine |
| quote: | | ... now Ed is going to claim he thought of it himself... |
If only I were that smart...I came into the world with nothing...what I know comes from others, even Mongo...as it was given to me I should give it to others...
 |
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| meanman1964 |
Help,
Is there someone in Europe that can take my order so I can pay with IBAN and SWIFT number.The reason is I don't use visa so I can't pay with Pay-Pal.:bawling: |
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| lgreen |
I'm in for a stereo set.
Having read a lot of carlos posts, I think I owe it to him to try this one out. |
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| Francois G |
Hi Nordic,
I would like a stereo set too, please.
Cheers and thanks for all your good work on this one.
Francois |
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| Nordic |
| Welconme on board you two.... thanks for trying to help our european friend, Ed. Most kind of you, sir. |
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| Ed LaFontaine |
Can one of you be of assistance to meanman 1964?
His request is simple: he needs some assistance in the transaction to acquire boards. I'll do it from the US, however without paypal the next option requires a money transfer penalty...the banking system is your friend????...
Could someone step up who is willing to accept his boards and send to him.
Meanman, we will get you boards, let's see if someone steps forward. |
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| meanman1964 |
Ed,
Thanks for the trouble you're doing. |
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| destroyer X |
I am very happy to see so many folks interested.
My thanks to each one of you.... really..thank you!
I hope you will apreciate the sonics...i have confidence you will.
regards,
Carlos |
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| meanman1964 |
thanks Nordic and Ed
Jack C has responded to my call and we gonna arange something. |
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| Jack C. |
Hi, Nordic.
So, I want now 2 sets : 1 for Meanman1964, and 1 for me.
Cordialement
J |
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| meanman1964 |
Hi Jack,
Thanks, man I own you one |
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| Jozua |
Hi
Can I order a set of Boards? Cost
Where can I see the circuit and parts list ?
Jozua |
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| Greg Erskine |
hi Jozua,
Good timing, I have just uploaded Carlos's DX HRII schematic and bill of materials (BOM) yesterday.
http://users.tpg.com.au/users/gerskine/dxamp/
I believe Nordic will also have a website for the DX HRII shortly.
regards |
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| Nordic |
The schematic on Greg's site is close to the one you will find on the board...
Some small diffirences, are
space for 2 zeners in series on the VBE to make up smaller voltages for lower supplies...
Also for some reason, the output resistor on mine is marked for 0R22, Greg's would probably be the correct value there...
I'm runnig mine without the output inductor, but if you like to listen with a scope, you should add these...... I need to get used to the new sound (changed to passive preamp on Friday, but will soon compare with adding the output inductors... of coarse you are a clever Krell builder so no need to explain what it does.....
Also the board makes provision for larger caps on the power rails... you should at least be able to fit 4700ufs in the space...
My working prototype is running with 4700u + 10000 per rail on the PCB... this is excluding the power supply.
We are approaching the $20 a set point now, if everyone goes through with their orders at this stage... might be a dollar or so either way...
Feel free to contact me directly, you have my e-mail address, I think I can get it down a few rand for you, as you probably won't have to use the credit card payment facility.
Greg: nice work on the site..... was not aware you added DXII, thought you just overhauled the DX site. |
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| Ed LaFontaine |
I'm very happy to see people come together with common interests...good things happen. Thank You Jack C. for extending a hand to help.
I've been thinking about asking for a BOM and it appears, followed closely by Nordic's comments on things.
Those who are unsure can go ahead and get on board.
Rest assured as new things are discovered about the amp they will be shared.
Thanks for the update, Greg.
I'm looking forward to hearing an amp from Carlos.
I'm smiling :D |
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| rabbitz |
| Put me down for a stereo pair please (2 PCB) and let me know how and when to pay. |
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| Nordic |
Welcome, Rabbitz.
I will try to finalise the payment facilities this week...... all major credit cards should be OK.
I will try to keep you guys ... and gals...informed.
Also still looking for safest low cost way to mail the parcels and get them to their destinations quickly...... I don't trust our post office system..... I'll be looking at mail couriers like DHL etc.... this normally also speeds up customs processes on the receiving end. |
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| konkret |
Hello Nordic,
since I am a new forum member and still under moderation I do not have access to your e-mail address.
If you see my e-mail under my member properties, could you please send me a short message such that I can reply?
I do not like posting my address here because of web page scanners, and my mail account is already filling with spam too much ...
Thanks!
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konkret |
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| AndrewT |
| quote: | Originally posted by konkret
.......I do not like posting my address here because of web page scanners, and my mail account is already filling with spam too much ... |
corrupt your Email address so that only humans can interpret it. |
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| Greg Erskine |
| quote: | Originally posted by Nordic
Greg: nice work on the site..... was not aware you added DXII, thought you just overhauled the DX site. |
Hi Nordic,
Thanks for the kind words. Yes, after a discussion with the boss, it was decided to keep the original DX Amplifier pages intact and just add the DX HRII schematic and BOM. The table of contents was changed a bit to accommodate both amplifiers.
| quote: | Originally posted by Ed LaFontaine
I'm very happy to see people come together with common interests...
Thanks for the update, Greg. |
Hi Ed,
No problems. My efforts are very, very minor compared to Carlos and Nordic.
regards |
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| Bearman |
Hi Greg,
You can put me down for 2 stereo sets please (4brds)
Bearman |
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| Nordic |
No, but I can... welcome on board...
Sorry for takeing so long to respond... crazy weekend, and today is a public holiday...satelite dish broke... had to spend hours to get a technitian to come out. Then one cat went awol... found her inside the house eventualy...
Right now I am about ready for bed after all this stress...... and it is only 5pm.
P.S. Konkret, I will keep ane eye open for that e-mail link of yours... should'nt take much longer before you are a full member... maybe shoot a post to one of the mods, they have been known to make an exception here and there....
Greg, I dissagree, I only copied and modified your hard work from before... Ecat also requires some thanks as he provided schematic files etc... which reduced my job to fiddleing with placements for a few hours every night... I normally lay out a few random circuits to help me fall asleep. |
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| Bearman |
Sorry...Thanks Nordic.
I have only built chipamps before. this will be my first SS amp.
Looking forward to it. |
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| Nordic |
Hey the DX original was my first DIY SS amp... The DX HDII board can be used to construct the orinal one too with a few minor part sustitutions/ommissions.
My previous experience was also chipamps...... worthy training ground. I won't claim to be on top of the DX amp seen from a macroscopic point of view, but through building it (and finding my errors and blown components), I learned enough to fix many old solidstate amps now, by focusing on it as little modules.
The silkscreen will at least make it less likely that you will make the same mistakes I did.
Plus the group of people that can pitch in with advice is steadily growing...... We try to keep things practical, and keep the scientists at a good distance...those guys who listen with scopes instead of ears...
The realy smart ones give us advice that anyone can understand... |
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| Jozua |
Nordic
I have some questions:
Is the PCB groupbuy on track. Is there a list where one can confirm if you on the list ?
Has anybody ever build the amp with high-end parts?
Are there any reviews available ?
Are you only supplying the PCB or parts as well ?
Thanks
Jozua |
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| SamL |
Hi Nordic,
I would like a stereo set too, thanks.
What about the power supply PCB? Will that be available? |
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| Stevox |
Hi Nordic,
I'm interrested too.
Count me in for one stereo set.
Peter. |
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| Nordic |
Sorry guys I will have to get back to you later with answers, hectic morning... yesterday was public holiday.....
Just received some new written quotes from the guys that quoted me last time... I asked for quotes on both 1 and 2 oz boards, based on our new numbers... looks like we can now get the 2oz boards for about the price I was qouted on 1oz originaly...
Waiting for written confirmation on the transactional cost part, hopefully will also receive this today. Then I can give you firmer prices. I think for the less than $4 per set diffirence it is well worth it.
Watch this spot. |
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| Jozua |
Hi
I auditioned Nordic's amp tonight and have been very pleasantly surprised. Very natural sound, lots of inner detail and deep tight bass.
It very hard to believe the results with such a small cost outlay !
I am definitely interested in this project.
Jozua |
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| destroyer X |
preference (Dx Corporation is only a game, kidding)....but we do not pay to dream.
I see that many folks are interested...i feel very good, you are filling my heart with a very nice feeling, the one we have when we contribute with others...the best feeling i think.
Ed de La Fontaine is an old and good friend...thank you...you are also in my heart...you are very positive and strongly appreciated.
Nordic...you are running very well this group buy....of course i have to thank you and will order a raise into your payment from the Corporation.
Thank you Nordic....excelent work.
I am sure you will appreciate the sonics folks...enjoy the nice sonics of this little amplifier that will provide you hours of joy and happyness.
regards
Carlos
.....................................................................................................
Rabbitz, Greg and other aussies
Were perceived into this group buy.... thank you very much...you know i love you all Aussie friends.
Nice people.... very nice people.
regards,
Carlos |
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| Jozua |
Carlos
Your design is very good. I have a niggling suspicion that when the amp is playing into a easy load it going to sound much better than 90% of my commercial amps. The only problem I have is that I suspect that my speakers occasionally drops to a very low impedance.
Despite my concern I am going to build your amp. I shudder what will happen if one uses very high-end parts. With so few parts it crazy not to use the very best parts you can find.
I hope that you can make some money out of your design for it is incredible jumpstart to high-end audio for any budding audiophile on a budget.
I wish you and Nordic well with your endevours.
Jozua
Cape Town
South Africa |
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| Nordic |
Thanks for the kind words.....
I forgot to tell you, none of the components except the input pairs were matched.......
Instead of going for the huge $ components, another approach to improved performance, can be to buy larger volumes of transistors etc. and matching them as close as possible.
Like I said, just give me a shout, and I'll bring the amp over so you can test it with your own speakers, and in your own listeing room.
The group buy is, as far as am concerned, definately happening.
I will try to make a page in the site's wiki section today.
If there is a demand I can also produce PSU boards.
The schematic for the PSU will be posted on the new website, they are burried so deep in the DX thread it may take you a while to find it otherwise, in case you'd like to DIY them.
Alternatively I have another low cost PCB manufacturer useing CNC router that can make those for us at minimal extra cost....
The catch? No soldermask, no silkscreen.... but this part of the circuit don have any transistors that can be inverted, so it is not a dealbreaker... This guy is very cheap....... If we were to make the DX boards useing his product, the cost would have been about a 3rd of what it is. I'd rather you have proper 2oz boards with silkcreens than have to field faultraceing answers all day long due to a lack of silk screen, so, this option only applies to the PSU.
I know the DX thread is very long so guys may have missed the fact that the VBE multiplier (bias servo) is offboard, it is however so small and simple that I will provide you with prepared veroboard strips for simply soldering the resistor, trimpot and transistor on there.
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| Harry3 |
Hi Jozua,
the component spacing is an issue in using "higher quality" components eg Vishay/Dale resistors etc as the PCB is small. They designed it for small tracks which is a good idea. However as mentioned before matching good transistors should be an improvement. As for the amp running into difficult loads I think it should be quiet capable but I did ask Carlos to help show us a design using 50Volts with two output pairs. Another alternative is to bi-amp which is what I am thinking of doing as the costs are very low.
Regards
Harry
PS I am glad you like the amp as I know you have a number of Krell amps to compare it to. |
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| gbyleveldt |
| I've not read the whole thread, but was also hoping for a design using two output pairs running 55V rails. I've got a lot of MJL4281 and MJL4302 output transistors lying around. |
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| Nordic |
Carlos may or may not release a new version a little later on... if I can float the boat till then, I will gladly see if I can assist again.
Sadly in those thousands of posts, Carlos gave many people advice on how to build higher power versions. Doing calculations prototypes etc... yet only 2 people went as far as constructing it.
I have increased the package sizes for the matched resistors around the input pair, to accommodate other types... and will see what I can do to the ones on the feedback path before sending the boards in.
P.S. Welcome, Gert. Nice to have another South African here. |
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| Jozua |
Harry
I have a 200 watt amp that has a Led display indicating the wattage output. Dont be fooled that low listening levels always means a low wattage output. On occasion I easily get 100-150 watts peaks on speakers that are claimed to be easily driven.
I suspect that the only edge the 50. clones have is their ability to stay in control with low impedance speakers -meaning that the sound remains coherent and dynamic and you get a sense of absolute control. BUT I have a niggling suspicion that i.t.o. musicality the DX is at the forefront.
After the Krell clones- I am finished with big audio projects. From then on it's low cost minimalist projects only.
My thinking now is also to build a 4 channel version that I can use for experimental work.
Nordic
Please explore the PSU board option. The neater the better.
I have a DIY Nelson Pass "Bride of Zen" pre-amp which I suspect will work very well with the DX as it is also a very simple one stage design.
Jozua |
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| destroyer X |
There's a resistance to feed the zenner.... it is 2K2... and this one will need increase if you double the supply voltage, you must double this resistance...so...there's a ratio... easy to calculate.
Using 55 volts, a good idea is to place, at least, 3 pairs in the output...better to go to 4 pairs if you will use 4 ohms loads.
All your transistors will need a check up if they can hold the rail to rail voltage.... plus 55 volts and minus 55 volts can produce 100 volts of swing (some losses into transistors)...so... every transistor must be checked for that.
The current we have into the VAS is already enougth...do not need to change the bootstrapp resistances.... they are fine.
You will have more power, even in the stand by mode, because the increase of voltage...so...even the VAS transistors will need heatsink.... also you can use two BD139 as VAS
Each output transistor will need it's own emitter resistances, and those one can be 0.47 ohms if you will use 4 output pair, 0.22 ohms if you will use 3 output pairs.
Each output transistor will need Its own base resistance... 2,2 ohms to 4.7 ohms will be fine.
Your fuses will need to be re-calculated
And all your condenser will need increasing in insulation voltages.
The off set will work fine, also the bias adjustment.
The difference is that you may check the current you have into output units...at least 5 miliamps to each transistor....measure over the emitter resistances.
Good luck!
regards,
Carlos |
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| konkret |
Guys, I really look forward to building and listening to this amp!
After full-range testing I plan to use it in an active speaker setup,
where it shall drive a tweeter directly without a DC-blocking cap.
Do you think, turn-on clicks or pops could be an issue?
Somewhere down the thread I read that output DC should be quite low, so this one should be okay, right?
Would you recommend a turn-on protection with a relay?
Thanks for your help!
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konkret |
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| Nordic |
Bob, although your parts list will certainly work, I have a few changes mostly related to the power rail capacitors... buy 8 of those 3300uf caps and use them all around, I however use 4700u + 10000u on my boards, also the zeners for the VBE will vary on your rail voltages...
I have rather low rails at 35V and use 2 16V zeners in series, in stead of the 33V ones you listed, those will be fine for slightly higher supplies, also your part numbers matches Greg's schematic, and differs from mine, so thismay give builders a little hard time figureing out what goes where when they get their boards.
Feel free to get the components but wait for the official BOM before you get carried away, all resistors and small caps look right on your BOM, as well as transistors (once again some part numbering differs)
I don't feel it right for me to just copy Greg's work, therefore there will be some slight diffirences between our work, I am busy building the website that goes with the boards.
Thank you for your enthusiasm.
There is no turn on click with my unit and it plays long until draining the caps at which point it just softly fades away and it sounds like it exhales softly, nothing nasty.
Of coarse if you use large toroidals you will need to take the measures needed for softstart etc. just as for anything you would build for them... but this is not due to the amp part.
Yes, as long as your input transistors and their resistors are reasonably well mathced, the amp will take care of offset automaticaly. |
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| SamL |
| quote: | Originally posted by Nordic
Bob, although your parts list will certainly work, I have a few changes mostly related to the power rail capacitors... buy 8 of those 3300uf caps and use them all around, I however use 4700u + 10000u on my boards, also the zeners for the VBE will vary on your rail voltages...
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Hi Nordic,
Can your PCB take 35mm 10,000uF cap? I ordered 4 Nichicon KG by mistake and will be good if I have a used for them. |
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| Nordic |
Hi guys sorry the Wiki is not up yet... been trying to get one up, but it seems I'm getting old.. will look at the instructions again today.
Sam, the maximum size you can "make fit" is 30mm on the front ones (I did), requires removal of spades... I don't see how you can go bigger than that... design is for 18 to 25mm type.
You could probably mount them offboard with little wires... like I did in the original DX.. Or keep em for the PSU... |
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| Harry3 |
| quote: | Originally posted by destroyer X
The current we have into the VAS is already enougth...do not need to change the bootstrapp resistances.... they are fine.
You will have more power, even in the stand by mode, because the increase of voltage...so...even the VAS transistors will need heatsink.... also you can use two BD139 as VAS
Good luck!
regards,
Carlos |
Hi Carlos,
thanks for your help in the 50Volt version.
I do not understand what you mean by ".... also you can use two BD139 as VAS".
Does this mean that I should use a transistor such as the MJE15032 instead of the BD139?
Also do I increase the 1K5 resistor that connects the positive rail to the 47uF cap?
Regards
Harry |
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| Nordic |
Just a small bit of feedback.
Today nothing much got done as I had to go to a medical specialist again. I did however rent the webserver this morning, but I am still battleing with the domain... registrar is haveing a problem with the nameserver... hope to have this resolved by tommorrow, as the website is nearly done. |
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| destroyer X |
one is small, and the second one is bigger (BD139)...i said that both can be BD139...those two transistors, together, constitute the VAS, the voltage amplifier.
All the voltage produced into the amplifier appear there.
The VAS stage, normally second stage, receive the signal from the first transistors into the differential..into the colector you may have a resistance or a transistor as a load for the first transistor.... transconductance happens there...current appear and will send to the VAS... this will be magically transformed into enormous voltage swing...more than 50 volts peak to peak.
............................
The amplifier has no noises into turn on or turn off..silent..dead silent.
regards,
Carlos |
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| Harry3 |
Hi Carlos,
now that you have explained...it's obvious. Many thanks.
regards
Harry |
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| Nordic |
Ok guys the domain www.dxamp.com is now live....
I have started to upload the information, but managed to break my template again... got it mostly fixed as I type this... so some pages are available, others will be unavailable for a few minutes as I work through them...
Orders are not active yet, as I am still waiting for authorisation to get a credit card facility.
Also the construction aids have not been uploaded yet, as I still need to do the artwork for that.
You can get a general feel for how things will work and what will be required, by going through the site so long.... there will be many typo's and things like that over the next day or two... I run the spell checker when I'm happy that I am more or less done. |
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| nogoodboyo |
Hi All
I'm excited to get started on this!
A question:
Is there a rock-solid trustworthy supplier in the US for the Toshiba output transistors? I've been hearing so much about fakes, and have got really concerned about this.
TIA
Andrew |
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| dudaindc |
| quote: | Originally posted by Nordic
Ok guys the domain www.dxamp.com is now live.... |
Nice work Nordic - well done! :worship:
Cheers! |
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| nogoodboyo |
| Thanks Kaos, they do have them, 2SA1943 and 2SC5200 are $5.29 and $3.99 ea respectively. Are these guys 100% trustworthy? |
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| kaos |
| I've never had any problems, and I've bought a fair number of Toshiba parts from them over the years. |
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| nogoodboyo |
Cool -- that's good to know.
The website says they are authorized dealers. |
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| Nordic |
Just to give you an idea of the price, I phoned the official Toshiba destributors quickly.... prices qouted in south african rand (ZAR)
sc5200 single R110, tube of 100 R18 each
sa1943 single R92, tube of 100 R16 each...
So even if you bought 100, the price comparison would be
5x18 + 5x16 = R170 (but you have to buy R3400 worth of transistors)
$35 = +-R240
So I think that $35 price is pretty fair. |
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| Nordic |
| How is their international shipping rates... I just happened to see the digikey price for these this morning.... pretty good. |
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| Greg Erskine |
From my last order:
"including $28.15 postage" |
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| Nordic |
Hey guys, some news...
I uploaded the first of the construction documents like, PCB, silkscreen, and schematic, for the amp today.
I also received the test merchant account, for setting up the orders page today, hope to have a shopping cart installed and running, shortly. |
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| gbyleveldt |
| quote: | Originally posted by Nordic
How is their international shipping rates... I just happened to see the digikey price for these this morning.... pretty good. |
Don't bother, any shipping to us is over $60. |
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| Nordic |
Ok, I looked at Farnell, they charge GBP2.5 per...
We can get that through manthech on special order... they add a bit to the price, but it is normally not too much.
PS... will someone do me a favour, I seem to be stuck behind a cashe, just go to the construction help page on the site, and see if you can open all the pdf's that have file sizes indicated... the other ones are not linked to anything yet...
I can see the files in my ftp browser, but IE won't open all of them.
Giving me gray hairs...
P.S. I know its still a little crooked in Firefox... working on it. |
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| dudaindc |
| quote: | Originally posted by Nordic
... will someone do me a favour, I seem to be stuck behind a cashe, just go to the construction help page on the site, and see if you can open all the pdf's that have file sizes indicated... the other ones are not linked to anything yet...
...
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Nordic
All (7) files open just fine... :darkside:
Cheers! |
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