Aleph J for Universal Mounting Spec

6L6

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R27 will set bias as measured across one of the output fet's source resistor. About 1.0 amp to start. (.45V) You could make this a resistor, the addition of the pot is for those who wish to experiment. (Also, there are two pads marked R27, one in-between the caps, and the one with the holes to mount the pot. Use one, and jumper the other.)

R7 is set to make the DC offset zero. This one should be used from the start.

R8 should be a resistor, only use the pot if you need to adjust the bias of the front end pair. (If you use BL grade Jfets, you will likely not need the pot)
 
Mosfet Matching

I've been reading the "how to build a better Aleph" thread. As I understand it, matching the JFET input transistors and output MOSFETs are key. I see that Zen Mod tried to explain which mosfets match which in post #392, but I didn't understand it.

Can you guys point me to "how to match transistors guide"? I've done the method suggested for the Salas power supply, but I'm not sure that's the best choice here.

Any suggestions on how many mosfets I will need to buy to get a reasonable match?

Alternatively, in post #401, 6L6 suggested that possibility of buying matched output transistors. Is that a real possibility?

Sorry for the newbie question, but I'm far more used to working in ICs. All this component matching is relatively new territory for me.
 

6L6

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Joined 2010
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The input Jfets need to be matched for Idss. A good DMM and 9V battery is all you need to do that. The current issue is actually buying the J74 or J108 for the front end.

Buying matched outputs is easy - contact member ' buzzforb ', he has them for sale.

The little bipolar transistors in the CCS and limiter are generic, just get a few from Mouser and don't worry about matching.

Alternatively, you can buy a full set of transistors from member " h_a "

Member " spencer " has the jfets available matched.
 
I'm still waiting for my aleph j board come,it shoud be yesterday based on invoice tracking :(

I'm collecting parts to be used, and need advice: if I want to use riken/amrg resistor, which position that I can/better use? Mostly I'll use prp mf, but I just love blue body and colourfull ring of riken, but not all value available, amrg come as my 2nd choice. I find that riken/amrg are used on tube amp,haven't seen any preference on SS yet

this will be my first SS build after gainclone :)
 
thanks 6L6,

Do you mean on source & output R as 0.47 3W? I'll use panasonic erx on that position, can't find any replacement for that yet. PCX is the only one source of riken that I can find, where only 4 values available for aleph-j,others matched with amrg
 
I was thinking to use Dale LVR/CW-5 on that position, to get higher heat dissipation. however my friend suggested that panasonic is better, even koa is better than dale. So i just follow the suggestion from the expert

is necessary to get 4 matched irfp per channel or 2 matched pair is enough?
 
I have 12 pcs of this heatsink, i'll put 6 pcs on each side that will make 20cm H and 50cm D. IRFP240 attached as size comparison

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An externally hosted image should be here but it was not working when we last tested it.


Since my project plan will include Aleph J, F4 and SIT 2SK82 choke version where all supply will be 24Vdc, i think that i can put 3 amplifier in 1 casing, but run only 1 at one time. psu supply will be 2 pcs toroid 2x18V 225VA with CRC where each toroids will be in paralel, since that toroid is the highest VA that i can get, but it's not enough to use 1 toroid only.

My question is which method is the best to switch power supply on these 3 separated amplifier:
1. use thick cable jumper on backside of casing, so manual jumper must be done, maybe use thick speaker cable and spade
2. using 2 relays on each voltage + - GND,2 relays should be rated around 20A on each rail but not sure for stability

this switch will be placed after CRC supply before amplifier to ensure only 1 active amplifier. don't suggest me to separate these 3 amps, can't afford extra money for another casing,toroids and cap bank :D
 

6L6

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Joined 2010
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Your heastinks are beautiful!

If you make stereo amp, make everything dual mono, the only common will be the chassis and AC mains connection. One torroid, one power supply PCB, one amp PCB per channel.

You mention 3 amp in one casing? Are you making multi-channel amp? Home theater?
 
Your heastinks are beautiful!

If you make stereo amp, make everything dual mono, the only common will be the chassis and AC mains connection. One torroid, one power supply PCB, one amp PCB per channel.

You mention 3 amp in one casing? Are you making multi-channel amp? Home theater?

i think he is putting 3 different amps in one chassis.
sharing one power supply and sinks so he can change from different topologies one at a time.

cool idea.

i would do the spade lugs myself, but if you do relays makesure they are up for the current surge
 
it will be stereo amp only, never have any plan to build home theater, i'd rather go to cinema and pay $5. I choose those 3 amplifiers to represent my understanding for the reading over the last 3 months. Aleph J for voltage source, F4 for current source, and SIT 2SK82 for single ended. Aleph J will be the first build since it's most common amplifier. My current loudspeaker is a branded 3 way floorstand "acoustic monitor reference 2", next DIY speaker project will be Elsinore that's good for current source, and Jericho Fostex206 for single ended

I've already got un-obtanium parts such as 4 x quad match pair K70+J74 on 7,8,9,10 mA range and Sony 2SK82 KD-33, while others parts can be easily found. And the hardest thing to come is drilling those heatsinks properly

Actually i'm inspired on XA30.5 casing,and my friend showed a local build with the same heatsink that i have, but each heatsink is 30cm length, it's too gigantic for me :D

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that's right @sakellogg, so i can switch different amps on different speakers. I find that being a dual mono is just too complicated, 4 bridge rectifiers and 4 rows of cap bank. Using a lockable binding post can utilize spade/banana, but i'm still curious if i can use the relays for simplicity but can not find any reference on high DC current relay circuit yet and which relay that can be used. I'm just worried that relay will be melted
 
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6L6

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Joined 2010
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With your transformers, you really should build dual mono powersupply in one chassis, and then drill your heatsinks for the UMS (Universal Mounting Spec)

http://www.diyaudio.com/forums/imag...sal/universal-mounting-specification-v2.1.pdf

Use bridge blocks, not discrete. They are easier to use, sound better, and much cheaper. As your capacitance will essentially double, due to having two power supplies, you are not going to need enormous caps, so keeping to, say 30,000uf/25V will keep that expense down. Two of the old DIYaudio PSU boards will hold everything. Or two of the Peter Daniel PSU boards.

Once that is done, now you can make the chassis so it's very easy to change the amplifier PCB, and you can swap out the F4 boards and replace them with the Aleph J, F5, F6, whatever strikes your fancy.
 
No. Set the pots to the nominal resistor value as specified in the schematic. It should be quite close to optimal.

1. I've been looking at several of the schematics and it seems that they are all missing values on certain resistors, including the potentiometer paths. Since the BOM lists the potentiometer max value, can someone please point me to the nominal values for all resistors? Specifically on the schematic I am looking at, nominal values for R7, R8, and R27 are needed.

2. For the power resistors, R16 - R23, I know everyone says that the Aleph is not very sensitive to sound based on resistors, but I am curious since the board is made for both axial and TO-220 style power resistors. In the past, metal film resistors like Panasonic ERX have sounded very detailed but a little cool. Thick film TO-220 resistors like Caddock MP930 have sounded slightly less detailed and a little warmer. Is something like this been experienced in the Aleph?

Thanks in advance for your help and experience.