Treblog

I ordered a PCB for a First Watt B1 buffer preamp this week. I was planning on making this one using perfboard but the opportunity to order a high quality and relatively inexpensive PCB was something I couldn't let pass. I still was thinking about how to implement the large electrolytic caps. Now that's all being sorted by the PCB. I ordered the PCB from a fellow diyAudio.com forum member from Sweden and it should arrive early november.

This morning I cobbled together a JFET testing "rig". The JFETs for this project need to be matched for optimum performance. This means ordering more than the four JFETs I need, test each JFET on the rig and then pick two matched pairs.

I'm planning on making a few small changes to the schematic Nelson Pass has released for the diyAudio community. The big caps are gonna be 10000µF instead of 15000µF due to availability, 10000µF is still plenty of capacitance. This means R1 has to be increased from 1 Ohm to 1.5 Ohms to maintain the RC filter (R1, C1) time constant. The volume pot is gonna be a 50 KOhm since that's what comes nearest to the 47KOhm input impedance my CD player currently sees.

A heavy parcel from Italy arrived today... Containing: two heatsinks, a rear panel, a top panel, a perforated base and a 10mm aluminium front panel. Not bad, in only a week from Bologna, Italy to my door. The case comes complete with four brackets to put it all together, a bag of screws, nuts & bolts and four basic feet. The quality of the case appears to be excellent. It meets my expecations. Excellent service from www.moduship.biz, highly recommended!

per il facile avvitamento delle viti autofilettanti si consiglia di usare olio o grassi o sapone

What does it mean? I can only understand half of it... Babelfish to the rescue!

for the easy tailspin of the self-tapping lives it is advised to use oil or fat people or soap

Fat people!? Let's stick to grease instead.

I picked up my F5 parts at the post office yesterday. Yesterday evening I started stuffing the boards and soldering everything. The quality of the PCBs is excellent, a really good job Peter Daniel did in making the layout. Minor niggle, the PCBs are made with tiny resistors in mind. My 0.6W resistors are too large to be lying flat on the PCB, they have to stand upright.

I ordered 0.47 Ohm resistors for the source pins of the output MOSFETs but received 0.50 Ohm instead. I'll just have to account for their slightly higher resistance when adjusting the bias current. No problem though.

The PCBs are now almost done, they're still lacking the thermistors and output MOSFETs. The MOSFETS will have to wait until they're mounted on the heatsinks. The thermistors will have to be bought still. More pics in the F5 photo album.


I also picked up a copy of the new Chris Ryan novel Firefight. Something to read coming summer holiday.

Today I received my two matched IRF9610 pairs. Packed in an anti-static bag with the matched pairs tied together. With these last parts my mini Aleph amp boards are finished. There's only one thing left, solder the IRFP240's once the heatsinks will be here. It's a bad idea to solder the IRFP240's now, it will cause stress on the solder joint when I bolt them to the heatsinks.