Just ordered the F6 parts from the DIY Audio store (the "kit" - boards + transformers, the B-grade Jfets, and the Mosfets).
I'll place an order with digikey tomorrow for the resistors, pots and caps that I need to populate the board if I don't already have them.
After all the commentary I could find, it seems the F6 (from an audio listening perspective) is similar to the Aleph J, but with more detail in the mids and and a little more drive.
I really considered an F5 (since I already have the mosfets) but am concerned about a little upper-midrange energy that became fatiguing after a while. I used to have an F5 and found this to be the case, but that was with a VERY different set of speakers.
My Zu Omens are 12ohm, so the F6 may not actually "sound" more powerful than my Aleph J, but it will be an interesting journey.
Listening to my AJ while I write this (Steven Wilson - Hand. Cannot. Erase.) and it really is a wonderful amp. So even if I hate the F6 (unlikely), I can just put the AJ boards back in.
At the expense of someone telling me to go read the 1,200 pages of Jim's build guide (ok, maybe not 1,200), does anyone have any advice for the F6 build? There appears to be much consternation over the value of the Zeners - many people found 5.8v to not be enough to get the amp to bias up... although, it appears a simple remedy is to reduce the value of the resister that sits in front of the Zener (maybe I'm confused).
Thoughts?
Thanks!
Matt
I'll place an order with digikey tomorrow for the resistors, pots and caps that I need to populate the board if I don't already have them.
After all the commentary I could find, it seems the F6 (from an audio listening perspective) is similar to the Aleph J, but with more detail in the mids and and a little more drive.
I really considered an F5 (since I already have the mosfets) but am concerned about a little upper-midrange energy that became fatiguing after a while. I used to have an F5 and found this to be the case, but that was with a VERY different set of speakers.
My Zu Omens are 12ohm, so the F6 may not actually "sound" more powerful than my Aleph J, but it will be an interesting journey.
Listening to my AJ while I write this (Steven Wilson - Hand. Cannot. Erase.) and it really is a wonderful amp. So even if I hate the F6 (unlikely), I can just put the AJ boards back in.
At the expense of someone telling me to go read the 1,200 pages of Jim's build guide (ok, maybe not 1,200), does anyone have any advice for the F6 build? There appears to be much consternation over the value of the Zeners - many people found 5.8v to not be enough to get the amp to bias up... although, it appears a simple remedy is to reduce the value of the resister that sits in front of the Zener (maybe I'm confused).
Thoughts?
Thanks!
Matt
Do the Zenner mod while building, it is a pain if you decide to do it later.
Replace R7 and R8 with 3k6 resistors. You replace the zeners (Z1 and Z2) with LM329 DZ's which are precision reference 6.9V zeners. On the LM329 DZ, cut off pin 1. Then connect Pin 2 to the pcb cathode and Pin 3 to the pcb anode (where Z1 and Z2 originally were supposed to be).
Use a light bulb tester for power up.
Be prepared for the bias adjusters working backwards.
Replace R7 and R8 with 3k6 resistors. You replace the zeners (Z1 and Z2) with LM329 DZ's which are precision reference 6.9V zeners. On the LM329 DZ, cut off pin 1. Then connect Pin 2 to the pcb cathode and Pin 3 to the pcb anode (where Z1 and Z2 originally were supposed to be).
Use a light bulb tester for power up.
Be prepared for the bias adjusters working backwards.
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Silly question - should I put a dab of heat-sink goop on the Jfets before I zip-tie them together?
Don't know about using goo.
I used heatshrink tube to hold them together.
Zip ties seemed loose.
I used heatshrink tube to hold them together.
Zip ties seemed loose.
you should also do the mod on the PCB in order to build the 'output degeneration' version of the circuit so that the 2nd harmonic is controlled via the resistor, opposed to a transductance difference in the mosfets
I have already ordered all the parts for the standard implementation. Also, I am not advanced enough to start messing with PCB traces.
Thanks for the recommendation though.
So no-one thinks I need heat-sink grease between the jfets? I could swear I saw that somewhere. 6L6 does not mention it in his build guide, so I'm not sure what he did.
Grease between the jfets is a good thing.
Just don't do what I see sometimes which is heat shrink the two parts together covering the top of the parts.
They need air around them or else what's the point?
Just don't do what I see sometimes which is heat shrink the two parts together covering the top of the parts.
They need air around them or else what's the point?
Thank you! I have seen people use the heatshrink on the Jfets, and it looks cleaner, but I have no problems with the zip-ties. They worked fine on my Aleph J (and, I have no idea if I used heatsink grease on the Jfets when I built the Aleph J... 😱 ...all my mental bandwidth is pretty much used up by work)
I have a set of transformers (CineMag 1:2) left over from a F6 build, would they have enough voltage gain to use instead of the edcor? I realize I will need more output voltage from my preamp.
I finished the F6 last night around 2:00am, biased it up this morning and it's been playing on and off all day. (The power has been on for about 10 hours straight).
A couple of observations / comparative notes to my DIY Aleph J -
1) When I first started playing music through it, I was pretty surprised at how different it is from the AJ - Before making any real assessments, I figured I would let it fully warm up and break in for a little bit.
2) Initial thoughts are the F6 hits more of the Audiophile buttons - it has more resolution, feels "faster", does the imaging thing a bit better, and has more power (thus dynamic swing)
3) By comparison, the AJ has MUCH more body and weight to notes - instruments seem to have a richer tonal presentation. The leading edge of notes is slightly fuzzier than the F6 and the placement of musicians in the horizontal plane is less precise.
4) The F6 is clearly presenting all "inner detail" much better than the AJ - all the tiny little noises/effects that are lower in the mix are more identifiable.
What do I like better? Hard to say - my initial thought is that I may go back to the Aleph pretty soon as I love it's laid-back, tonally rich presentation that causes zero listening fatigue, even after listening for hours. When I first fired up the F6 there was a bit of an upper-midrange emphasis that I thought may become uncomfortable after a while. It seems to have subsided a little over the last couple of hours - either that or I am just getting used to it playing in the back-ground. I does not help that my room is lively.
I will give the F6 a couple of weeks before I decide to go back to Aleph J. Don't take this as me suggesting that I think the F6 is not a great amp - I just may prefer the Aleph J.
More to come. And thank you to everyone that responded to my questions and 6L6 for putting together is build guide.
A couple of observations / comparative notes to my DIY Aleph J -
1) When I first started playing music through it, I was pretty surprised at how different it is from the AJ - Before making any real assessments, I figured I would let it fully warm up and break in for a little bit.
2) Initial thoughts are the F6 hits more of the Audiophile buttons - it has more resolution, feels "faster", does the imaging thing a bit better, and has more power (thus dynamic swing)
3) By comparison, the AJ has MUCH more body and weight to notes - instruments seem to have a richer tonal presentation. The leading edge of notes is slightly fuzzier than the F6 and the placement of musicians in the horizontal plane is less precise.
4) The F6 is clearly presenting all "inner detail" much better than the AJ - all the tiny little noises/effects that are lower in the mix are more identifiable.
What do I like better? Hard to say - my initial thought is that I may go back to the Aleph pretty soon as I love it's laid-back, tonally rich presentation that causes zero listening fatigue, even after listening for hours. When I first fired up the F6 there was a bit of an upper-midrange emphasis that I thought may become uncomfortable after a while. It seems to have subsided a little over the last couple of hours - either that or I am just getting used to it playing in the back-ground. I does not help that my room is lively.
I will give the F6 a couple of weeks before I decide to go back to Aleph J. Don't take this as me suggesting that I think the F6 is not a great amp - I just may prefer the Aleph J.
More to come. And thank you to everyone that responded to my questions and 6L6 for putting together is build guide.
Nothing wrong with your assessment. If we all liked the same thing, we'd be listening to 5 stage, push-pull, class A/B amps. 😉
Ever see Moscow on the Hudson when he's trying to pick out coffee in the coffee isle?
This is how I feel about amp building today- too many choices, but it's better than 25 years ago. I could not find anything to build.
Variety is the spice o' life. Enjoy!
Vince
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