Where do you want the C2 cap connected, between the source and resistor or after the resistor. There has been much discussion about this. Your opinion is appreciated.
there is no dilema about that , and I wrote it already
caps must be connected to include source resistor in gate circuit, thus shaping output device output characteristic
for SS devices , source resistors are there strictly for that purpose , not being necessary for thermal stability of Iq
for verticals , source resistors are necessary for thermal stability , but I'm damn sure that Pa made them of different values (upper vs. lower) with reason ..... and that reason demands caps connected where they belongs
anyway , where exactly is Papa's first/initial post with mosfet iteration schematic ?
caps must be connected to include source resistor in gate circuit, thus shaping output device output characteristic
for SS devices , source resistors are there strictly for that purpose , not being necessary for thermal stability of Iq
for verticals , source resistors are necessary for thermal stability , but I'm damn sure that Pa made them of different values (upper vs. lower) with reason ..... and that reason demands caps connected where they belongs
anyway , where exactly is Papa's first/initial post with mosfet iteration schematic ?
Last edited:
dilema-including MOSFET source resistors in AC path or not , solved by Papa's post
OK , found exact post from Papa :
#658
so, I didn't get it right previously - about his exact intentions
however , I'm liking more iteration where source resistors are included in AC path
OK , found exact post from Papa :
#658
The Fairchilds in the F5 have a bigger temperature coefficient, so they
drift more with temperature than the IR N channel parts.
Also, you can use higher values for the Source resistors on the F6 if you want,
as they are not seen in the AC performance, only the DC.
I see that we have lost cool icon again.
so, I didn't get it right previously - about his exact intentions
however , I'm liking more iteration where source resistors are included in AC path
Bare, what bias did you set your amp to?Also did you let it warm up for an hour or so before listening.This amp takes a long time to come up to final bias.If I was you I would definitely re route the caps negative to the bottom of the source resistors.Try that and listen and let us know.Seems a shame to just let it sit.Thanks.
Merely immediate dissapointment /ranting
I'll get over it.
Likely revisit it all in the fall.. prolly experiment with it then
All bits from DIYAudio shop including matched jfets.
Following the recipie seemed important
Tannoys NEED heavy current capable amplifications.
Those big heavy cones do poorly without significant current control. (I've learned a little bit about them since '72 )
Forget that and weak bass /dynamics result.
That reminds me, I have not varied the stock store board configuration to "put those resistors where they belong" yet...time to heat up solder iron.
Russellc
To Bare, at first I did not respond because it seemed that you already made up your mind. You seemed more intent on proving your theory that new technology is better than old than to get your F6 to sound as good as it should. All your detailed descriptions in post #6 do not indicate the F6 sounds mediocre...it shows that something is wrong with your F6, given all the overwhelming evidence of glowing results of fellow DIYfers with FW amps and 6Moon reviews as stated before. If you drove a friend's Porsche and it had only the pickup of a Honda Civic, that would not prove that Porsches are slow, it shows that something is wrong with that Porsche, like a spark plug wire came off.
I am writing with the hope that you will eventually "dig into" your amp, and also to encourage any "quiet" reader who maybe has or might have a problem building a FW amp, but has not posted. All the hints to diagnose the cause have been given by Zen Mod and others, and I can only repeat the important steps. Post detailed pics. Tell about any deviations from the build guides. Check all joints and parts with power off with a DMM. Check voltages with power on and post results. You already said you bought DIY store jfets, but some people might have bought jfets and mosfets from ebay (probably fake) so give Vds measurements. Borrow a scope or buy a cheap USB one and check for oscillations, ect. with and without an input sine and square wave. Get with another diy'fer in your area. The members in this forum will go to great measures to help anyone get their FW amp working and sounding superb, but not so much to help prove a FW amp is mehhh and old technology. I think most of us consider these Pass designs as being the "New" technology. Building your own amp is supposed to be fun, so it is ok to take a little time off to recoup, but please do not give up.
BTW, I really enjoyed what Zen Mod did with his Tannoys to increase the WAF. That is an issue many of us continually deal with. For example my wife still reminds me that the dining room table is not for building amps.
I am writing with the hope that you will eventually "dig into" your amp, and also to encourage any "quiet" reader who maybe has or might have a problem building a FW amp, but has not posted. All the hints to diagnose the cause have been given by Zen Mod and others, and I can only repeat the important steps. Post detailed pics. Tell about any deviations from the build guides. Check all joints and parts with power off with a DMM. Check voltages with power on and post results. You already said you bought DIY store jfets, but some people might have bought jfets and mosfets from ebay (probably fake) so give Vds measurements. Borrow a scope or buy a cheap USB one and check for oscillations, ect. with and without an input sine and square wave. Get with another diy'fer in your area. The members in this forum will go to great measures to help anyone get their FW amp working and sounding superb, but not so much to help prove a FW amp is mehhh and old technology. I think most of us consider these Pass designs as being the "New" technology. Building your own amp is supposed to be fun, so it is ok to take a little time off to recoup, but please do not give up.
BTW, I really enjoyed what Zen Mod did with his Tannoys to increase the WAF. That is an issue many of us continually deal with. For example my wife still reminds me that the dining room table is not for building amps.
I am betting something is wrong with your F6. It will be interesting when you take it back out for experimentation. Please do post back, Whenever that is.
Russellc
I also think that you got something wrong,just like my SIT L'amp which sounds dull, it'running well but not sound right. Just need extra effort to check where it's culprit, but i'm lucky it's more simple than your F6 but still have no time.
Maybe you can send your F6 to me if you dont like it
Maybe you can send your F6 to me if you dont like it
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.