Thanks Buzz & PKI. I'll keep a check on mine but this isn't the first time that I've had to reset things.Guess I'll order the store board when they become available as I really do like the SQ of the F6.
Would you mind posting big photos of your final assembly? It is always good to have another pair (or 2,3,4...) of eyes take a look 🙂
PKI, could temperature fluctuations be causing the drift? Maybe a HVAC vent too close to the amp?
There are some pics I posted in post 296 which shows my build.If they are not big enough I can take some more and post later.
My amp uses a single supply with a 500VA toroid;standard block rectifiers feeding a CRC supply with Rifa 47;000uf R15 47;000uf.
Thanks for looking.
My amp uses a single supply with a 500VA toroid;standard block rectifiers feeding a CRC supply with Rifa 47;000uf R15 47;000uf.
Thanks for looking.
Can you please tell me where I can buy these transformers as I desperately wnat to build this amp?
I contacted Jensen via an emailaddress given at their web page, sales@jensen.... I believe it was, and after a very short interval of time I was contacted, I asked for two JT-123-FLPCH, we agreed about payment via PayPal and i was sent the necessary information. The transformers arrived after cirka two weeks. Very good service indeed. 🙂
I wish Jensen was as fast as you at responding I have sent two emails now to them asking how to buy their transformers but no reply. Did you manage to have human contact with them? Hopefully someone at Jensen reads this forum and responds I'm dying to build the F6!
nearly there. I bought the semisouths for this in 2012 and the jensens off Buzz sometime in 2013 and then got side tracked.....finally put it together this week with irfp240s and the diyaudio circuit...casework is nearly finished so fingers crossed.....
can anybody that's built this give me an idea of the optimum bias point to get started?
can anybody that's built this give me an idea of the optimum bias point to get started?
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me dig your style
Iq - 50C at sinks (electrically - start with 1A5 , wait for temp equilibrium then keep cranking)
Iq - 50C at sinks (electrically - start with 1A5 , wait for temp equilibrium then keep cranking)
it lives!
switched it on yesterday(left channel only) and default setting for pots was about 514mv across R2(1.09A) so left it to sit for a while. After 30 mins the idle point had moved to 570mv and the wall
monitor showed 72 watts draw for the amp....
today connected both channels and set bias at 700mv across R2, this quickly climbed to 740 and 730mv left and right. measured VGS
LHS : Q1 4.19v, Q2 4.29v
RHS : Q1 4.20v, Q2 4.19v
these were IRFP240s from the bit box so they didn't seem too mismatched at this stage.
after 6 hours LHS measured 721mv and RHS 709mv so it had settled a bit. Sinks were hottish and the wall monitor showed 173 watts consumed. I hooked up the THD measurement for completeness but havn't done the sums yet.
I felt confident enough to have a listen through my TQWP Fostex 206s and liked what I heard.
Onward.....
Ed
switched it on yesterday(left channel only) and default setting for pots was about 514mv across R2(1.09A) so left it to sit for a while. After 30 mins the idle point had moved to 570mv and the wall
monitor showed 72 watts draw for the amp....
today connected both channels and set bias at 700mv across R2, this quickly climbed to 740 and 730mv left and right. measured VGS
LHS : Q1 4.19v, Q2 4.29v
RHS : Q1 4.20v, Q2 4.19v
these were IRFP240s from the bit box so they didn't seem too mismatched at this stage.
after 6 hours LHS measured 721mv and RHS 709mv so it had settled a bit. Sinks were hottish and the wall monitor showed 173 watts consumed. I hooked up the THD measurement for completeness but havn't done the sums yet.
I felt confident enough to have a listen through my TQWP Fostex 206s and liked what I heard.
Onward.....
Ed
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Vitalstates: What case and power supply did you use? One of the things this newbie has to figure out to build this .....
-Tom-
-Tom-
Hi Tom
heat sinks are from Conrad in Australia. Case is 1 piece of bent 2mm aluminium sheet with equal angle 15mmx3mm for jointing. I have 2mm sheet for the lid and 5mm sheet for the front. All up cost about £60. I used this method because I had sinks and bent sheet lying around for nearly 10 years after F2 and F4 builds. It may be possible to do it a bit cheaper, its certainly possible to do it more expensive.
edit: power supply is from Nelson's original circuit, same as I used for F4 some years back. Tx is an airlink 300va with all the shoelding added. Details on my website. I will post up the whole build detail on the web site in due course.
Hi Marra
I've only had about an hour of serious listening. So far I'm more concerned about the bias instability. Initial thoughts were that it's a tad grainy and seems to get a bit confused on orchestral and complex. It all means nothing cos it's all new parts and the quiescent point is not stable at the moment.....but it's certainly engaging. More later.
Ed
heat sinks are from Conrad in Australia. Case is 1 piece of bent 2mm aluminium sheet with equal angle 15mmx3mm for jointing. I have 2mm sheet for the lid and 5mm sheet for the front. All up cost about £60. I used this method because I had sinks and bent sheet lying around for nearly 10 years after F2 and F4 builds. It may be possible to do it a bit cheaper, its certainly possible to do it more expensive.
edit: power supply is from Nelson's original circuit, same as I used for F4 some years back. Tx is an airlink 300va with all the shoelding added. Details on my website. I will post up the whole build detail on the web site in due course.
Hi Marra
I've only had about an hour of serious listening. So far I'm more concerned about the bias instability. Initial thoughts were that it's a tad grainy and seems to get a bit confused on orchestral and complex. It all means nothing cos it's all new parts and the quiescent point is not stable at the moment.....but it's certainly engaging. More later.
Ed
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