[KTS]

This is the Aleph Jzm it is the Zen Mod’s version available on the DIY audio website and uses 3.3uF cap in the c-1 position, I mention that because the original Aleph J used a 1uF cap and I am not sure which version you have and did not want to lead you astray. I built this one as a dual mono, it sounds more to my liking than anything I have had to this point.

[Tyson]

This is the Aleph Jzm it is the Zen Mod’s version available on the DIY audio website and uses 3.3uF cap in the c-1 position, I mention that because the original Aleph J used a 1uF cap and I am not sure which version you have and did not want to lead you astray. I built this one as a dual mono, it sounds more to my liking than anything I have had to this point.

Mine are all 1uf.  Which cap should I replace?  It looks from your picture that it's the one in the middle of the board?

[KTS]

Mine are all 1uf.  Which cap should I replace?  It looks from your picture that it's the one in the middle of the board?

It should be C1, but I am not sure what iteration you have. It is best to find the schematic and use it to determine, however all the Aleph J’s I have built it has always been notated as C1 on the board and the schematic.

[Tyson]

Perfect- thank you!

[KTS]

Not sure if you have the rectangle or square boards, but here is how I set mine up, be sure you cover your leads with heat shrink to prevent any unwanted contact if you run them behind the board to solder.

[jmimac351]

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[mkrawcz]

Walmart sells an electronics toolkit that should have the small sizes needed.
https://www.walmart.com/ip/Hyper-Tough-77-Piece-Precision-Tool-Kit-with-Magnetic-Screwdriver-Standard-Size-Bits-and-Case-New-Condition/909383908?wmlspartner=wlpa&selectedSellerId=0&selectedOfferId=873C31391DA944A2B5A3F6414D3109B1&conditionGroupCode=1&wl13=1831&gclsrc=aw.ds&adid=22222222278909383908_117755028669_12420145346&wl0=&wl1=g&wl2=m&wl3=501107745824&wl4=pla-394283752452&wl5=9005083&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=local&wl12=909383908&veh=sem_LIA&gclsrc=aw.ds&gad_source=1&gad_campaignid=12420145346&gbraid=0AAAAADmfBIo1-gXg3xOz6vR0SaOm0oeq8&gclid=Cj0KCQjw-ZHEBhCxARIsAGGN96IQOatLkYFeUvFNQ1WH0i_1CqOLc6ynJZHl6cmqy7jk2fQ5ETTzJB0aAsctEALw_wcB

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[Jaytor]

Just got my Iron Pre balanced up and running. This thing is Mighty! The problem now is I have to finish wiring up all the inputs and that involves turning it off. 

Are you still enjoying your Iron Pre?

This design has inspired me to try a similar concept with a transformer volume control. The inputs will be relay switched (like the Iron Pre) and directly feed balanced Jfet buffers, but I am planning to use two of each Jfet in parallel (i.e. two 2SK170s and two 2SJ74s for each phase of each channel). The drains and sources will be connected together, with separate gate-stopper resistors. This doubles the bias current, halves the output impedance, and reduces noise by 3db. The only downsides are double the input capacitance (although this is very low at around 40pf) and needing twice the number of Jfets which have to be well matched. Fortunately, the DIYAudioStore offers matched NP octets (four 2SK170s and four 2SJ74s).

The balanced buffers will feed a Silk Audio TVC which can be strapped for 0db or 6db of gain. This TVC has 22 outputs with 2-4db steps between outputs (2db in the middle range where you'll most often be operating). These outputs will be switched with the same high-quality Panasonic relays I've used for my relay switched attenuators, but in this case, there will only be one relay in the signal path at any time. Since we're using a transformer, the output can be balanced or single-ended.  I'll implement an Arduino-based controller for switching the relays so I can have a rotary encoder and IR remote, and a nice display showing the volume setting.

[mkrawcz]

Jaytor, yes I love the Iron Pre. I have since converted it to a single 4gang pot,
But at some point I will change all that out to something else with a remote. I bet a similar design using Toshiba JFETs will sound very good.

[jmimac351]

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[mkrawcz]

I am going to start digging into the diyaudio store and find something to play with that (hopefully) doesn't involve "cubic dollars".  I think I have just enough experience and taste of what I like to parse the words for those projects enough to find a good fit.

Get yourself on the email notification for when the Zenductor 2 monoblocks become available again. They’re stupid good for the money. I love them, they’re one of my favorite amps and they require no fiddling at all once the bias is set. Also probably the easiest amp you can possibly build.

[jmimac351]

Get yourself on the email notification for when the Zenductor 2 monoblocks become available again. They’re stupid good for the money. I love them, they’re one of my favorite amps and they require no fiddling at all once the bias is set. Also probably the easiest amp you can possibly build.

Roger, Roger...

[Jaytor]

My latest DIY Linestage is now complete.



This is a two chassis design - power supply in one chassis and all audio circuitry in the second chassis.





There are three umbilical cords - one for the B+ and chassis ground, one for the two filament supplies, and one for the low voltage supplies (+/- 15V and + 12V).

The main chassis includes relay switched inputs with Jensen input transformers to convert balanced to single ended. The single-ended signals are then attenuated by a relay-switched attenuator. This feeds two separate line stages - a discrete solid state line amplifier with JFET inputs and BJT outputs which drive the RCA outputs (to connect to single ended subwoofer inputs), and a DHT stage employing EML 20A triodes. The triodes use a Lundahl choke load and employ filament bias using Rod Coleman current regulators. The plates are AC coupled to a Lundahl line output transformer, currently configured as 11.8:1, so the overall gain is about 3db with an output impedance of about 50 ohms.

An Arduino microcontroller is used to control the input selection and stepped attenuator and drives a large bright LED matrix display (so I can easily see it from across the room with my declining vision). 



The power supply is controlled with another Arduino processor to provide a soft start for both the B+ and Filament supplies, and a 12V trigger output. The filament supplies are turned on 30 seconds before the B+, and stay on for 30 seconds after B+ is turned off on power off.

There are no electrolytic caps in the B+ supply (or audio circuitry). The B+ uses a 10H choke input feeding a 175uF Polypropylene Clarity cap followed by another 10H choke into another 175uF cap, which feeds another 175uF cap through resistors to adjust the B+ voltage. The B+ is split in the main chassis through separate resistors and 4-terminal 100uF Kelvin capacitors.



I haven't had a chance to listen to it much yet, but if sounds very nice so far.

[tremrej65]

My latest DIY Linestage is now complete.

Wow. Super nice looking pre-amp.
Is this your design? Impressive.