Question on Z1/2 and Heat Sinks
I'm about to begin stuffing my F6 boards and UPS board but had one quick question before getting too far in. I have a Mouser order ready for the items I've found so far as updates in working through the F6 build thread - at 166 of 225 pages and counting down. I could have missed a PN reference for Z1/2 in the ZenMod suggestion, but is this one acceptable?
https://www.mouser.com/ProductDetail/625-BZX85C6V2
Please recommend an alternative if not. I've seem 6.2V, 6.8 and 6.9 mentioned with [seemingly] more comments of 6.2 - correct or order the 6.8s?
For those who've built with the Conrad MF35-151.5 heat sinks. http://www.conradheatsinks.com/products/flat100_350.html. How has your thermal performance been? I'm pondering these and look for chassis parts vs. the DIY store link 4U. I have an Antek AS-3218 - no mono blocks or dual mono as yet - want to get a stable "standard" build in place first before considering next options. I have some UPS questions also, but will post up in that thread for them. Thanks!
I'm about to begin stuffing my F6 boards and UPS board but had one quick question before getting too far in. I have a Mouser order ready for the items I've found so far as updates in working through the F6 build thread - at 166 of 225 pages and counting down. I could have missed a PN reference for Z1/2 in the ZenMod suggestion, but is this one acceptable?
https://www.mouser.com/ProductDetail/625-BZX85C6V2
Please recommend an alternative if not. I've seem 6.2V, 6.8 and 6.9 mentioned with [seemingly] more comments of 6.2 - correct or order the 6.8s?
For those who've built with the Conrad MF35-151.5 heat sinks. http://www.conradheatsinks.com/products/flat100_350.html. How has your thermal performance been? I'm pondering these and look for chassis parts vs. the DIY store link 4U. I have an Antek AS-3218 - no mono blocks or dual mono as yet - want to get a stable "standard" build in place first before considering next options. I have some UPS questions also, but will post up in that thread for them. Thanks!
Hi, this just caught my eye ...
The Conrad heatsink MF35-151 (151mm long fins, 350mm long front-back) are rated at 0.21*C/W and each F6 channel will generate approx 75watts with a bias around 1.6A, so temp rise will theoretically be 0.21 X 75 = 16*C temp rise, so for an approx summer indoor temp of say, 30*C, the heatsink will be about 46*C.
Now, a small detail- the heatsinks don't work as well at these lower temperatures so a derating factor is used and this is set for the actual operating temp so on a colder day, the sinks aren't as effective and the derating factor for a temp of 46*C is 1.2 so your efficiency is reduced by this amount, so your 0.21*C/W becomes 0.21 X 1.2 = 0.25*C/w so the corrected temp rise will now be 0.25*C/w X 75 = 19*C temp rise and on a 30*C day, this'll mean your sinks will be about 50*C - quite hot, but not too bad.
Now, if your base, front panel, etc are mechanically fixed to the heatsinks, there's a bit more heat radiated from them which will reduce this approx 50*C down a few *C.
I've used the shorter 300mm version of this (still 151mm long fins) with the +/- 23V rails and current set at 1.6A (= 75W) and the temp rise is about 20*C so there's a margin in the calculations.
I also use a small 4mm space between the bottom plate and the heatsinks to allow an extra stream of air to flow over the insides of the heatsinks/boards and this functions quite well.
Many posts about those zeners - the ZM recommendation is to use the 6.2v ones and increase the current thru them by changing the 10kR resistor to 3k3R - I later replaced these with 'pico's "3 green leds" with 3kR resistors which created a similar 6.3v voltage and added a 10uF cap across those - I was rather pleased with the change in the sound.
A brief mention about a somewhat contentious subject, the power supply - I would start with the basic type caps like the CDE, Nichicon, Panasonics, etc and good quality GB bridges (or discrete Soft Recovery diodes) and maybe get fancy later on - I'm of the view that the components of the power supply makes quite a difference in the amp's performance (and sound) and have "gone over to the darkside" with synchronous bridges, high spec transformers, boutique caps, regulators, etc and I think it's well worth the trouble but it's also much more expensive and for some/many people, the $s are better spent elsewhere - just my 2 cents here ...
All the best with the project of a really nice NP designed amplifier indeed.
The Conrad heatsink MF35-151 (151mm long fins, 350mm long front-back) are rated at 0.21*C/W and each F6 channel will generate approx 75watts with a bias around 1.6A, so temp rise will theoretically be 0.21 X 75 = 16*C temp rise, so for an approx summer indoor temp of say, 30*C, the heatsink will be about 46*C.
Now, a small detail- the heatsinks don't work as well at these lower temperatures so a derating factor is used and this is set for the actual operating temp so on a colder day, the sinks aren't as effective and the derating factor for a temp of 46*C is 1.2 so your efficiency is reduced by this amount, so your 0.21*C/W becomes 0.21 X 1.2 = 0.25*C/w so the corrected temp rise will now be 0.25*C/w X 75 = 19*C temp rise and on a 30*C day, this'll mean your sinks will be about 50*C - quite hot, but not too bad.
Now, if your base, front panel, etc are mechanically fixed to the heatsinks, there's a bit more heat radiated from them which will reduce this approx 50*C down a few *C.
I've used the shorter 300mm version of this (still 151mm long fins) with the +/- 23V rails and current set at 1.6A (= 75W) and the temp rise is about 20*C so there's a margin in the calculations.
I also use a small 4mm space between the bottom plate and the heatsinks to allow an extra stream of air to flow over the insides of the heatsinks/boards and this functions quite well.
Many posts about those zeners - the ZM recommendation is to use the 6.2v ones and increase the current thru them by changing the 10kR resistor to 3k3R - I later replaced these with 'pico's "3 green leds" with 3kR resistors which created a similar 6.3v voltage and added a 10uF cap across those - I was rather pleased with the change in the sound.
A brief mention about a somewhat contentious subject, the power supply - I would start with the basic type caps like the CDE, Nichicon, Panasonics, etc and good quality GB bridges (or discrete Soft Recovery diodes) and maybe get fancy later on - I'm of the view that the components of the power supply makes quite a difference in the amp's performance (and sound) and have "gone over to the darkside" with synchronous bridges, high spec transformers, boutique caps, regulators, etc and I think it's well worth the trouble but it's also much more expensive and for some/many people, the $s are better spent elsewhere - just my 2 cents here ...
All the best with the project of a really nice NP designed amplifier indeed.
3.3K on R7/8. what about 9/10?
Thanks for the comments on the Z1/2 - and heat sinks. I meant to ask also if R 9/10 change as they're listed in the BOM w/ R7/8 as 10K originally. Still looking for a head nod - or not - on the Mouser PN.
Good input on the Conrads - I should run a calculation set against them and the default 4U/400 I guess. The 4U/400 fins just "seem" close to what I've seen on ABs / have on a Halfer AB amp, so I started looking for improvements.
I've used Munford caps in crossovers so was actually considering theirs for the UPS - and yes, there's a cost associated there I know.
Thanks for the comments on the Z1/2 - and heat sinks. I meant to ask also if R 9/10 change as they're listed in the BOM w/ R7/8 as 10K originally. Still looking for a head nod - or not - on the Mouser PN.
Good input on the Conrads - I should run a calculation set against them and the default 4U/400 I guess. The 4U/400 fins just "seem" close to what I've seen on ABs / have on a Halfer AB amp, so I started looking for improvements.
I've used Munford caps in crossovers so was actually considering theirs for the UPS - and yes, there's a cost associated there I know.
With your stated goals of keeping things simple at least initially; one of the easiest things to do is to replicate what's provided in the kit. I have not seen anyone post that they've not had a functioning amplifier (when properly built) with the provided components.
I don't know the diameter for the holes on the boards, but 3W diodes you posted typically have a comparatively larger lead size.
Examples below for what I'd assume to be similar parts to those from the kit.
I don't know the diameter for the holes on the boards, but 3W diodes you posted typically have a comparatively larger lead size.
Examples below for what I'd assume to be similar parts to those from the kit.
- Z1/2 5.1v Zener (4) (Marked "31B") - https://www.mouser.com/ProductDetail/onsemi-Fairchild/1N5231BTR?qs=SSucg2PyLi4jKyKWJywUyQ==
- Z1a/2a 6.0V Zener (4) (Marked "33B") - https://www.mouser.com/ProductDetail/onsemi-Fairchild/1N5233B?qs=SSucg2PyLi7cQocVn5ubiw==
The 3.3kR is to provide the 5mA current thru the zener diodes (ie 17v drop across the 3.3k = 5ma). Use the smaller BZX79c6v2 1/2w zeners (Mouser part 512-BZX79C6V2) or the 1n4735. R9/10 stays same as 10kR.
THe 4U/400 are actually considerably bigger sinks than the Conrads at nearly 8" tall and 400mm long so will run quite a bit cooler. It depends on how high you bias the amp, for example if you set the amp at 1.3A with +/- 23v rails, the sinks receive about 60watts to dissipate but at 1.7A, this increases to about 75w - with the large Dissipanti (?) 4U cases, neither current set will be a problem.
You might look towards the F&T electros if you favour the Mundorf caps - as far as I know, the F&T factory still makes them but sells the similar caps under the F&T brand - I don't know if they're the same quality caps but F&T have earned a good reputation over the years
THe 4U/400 are actually considerably bigger sinks than the Conrads at nearly 8" tall and 400mm long so will run quite a bit cooler. It depends on how high you bias the amp, for example if you set the amp at 1.3A with +/- 23v rails, the sinks receive about 60watts to dissipate but at 1.7A, this increases to about 75w - with the large Dissipanti (?) 4U cases, neither current set will be a problem.
You might look towards the F&T electros if you favour the Mundorf caps - as far as I know, the F&T factory still makes them but sells the similar caps under the F&T brand - I don't know if they're the same quality caps but F&T have earned a good reputation over the years
Thanks to you both! I've updated my Mouser order and now there are a couple of additional PN refs in the build thread 
@jameshillj - I was hoping to be able to use a chassis somewhat smaller than the seriously large 4U/400 as I plan to bias to the nominal in the build thread. I really appreciate the insights, but may also go reread the comments on a 3U /400 version - or the 4U/400 may just be the size appropriate here. I've not been able to locate dimensions on a factory F6, but photos suggested [to my view that could certainly be askew] it may be less than 8 in. tall - even though the heat sinks are vastly different than store chassis versions - hence the search.
Great pointer on the F&Ts - a quick search found them to be only [lietrially] a couple of dollars cheaper than the MLytics - or equal / smidgen more depending on seller. But I'll continue to chase them
@jameshillj - I was hoping to be able to use a chassis somewhat smaller than the seriously large 4U/400 as I plan to bias to the nominal in the build thread. I really appreciate the insights, but may also go reread the comments on a 3U /400 version - or the 4U/400 may just be the size appropriate here. I've not been able to locate dimensions on a factory F6, but photos suggested [to my view that could certainly be askew] it may be less than 8 in. tall - even though the heat sinks are vastly different than store chassis versions - hence the search.
Great pointer on the F&Ts - a quick search found them to be only [lietrially] a couple of dollars cheaper than the MLytics - or equal / smidgen more depending on seller. But I'll continue to chase them
I have an "official" F3 amp case here with the 'side fins' and now houses the 'basic' F6 - it's 125mm high (5") x 370 long (14.5") and 430 wide (17") so yes, quite a bit smaller than the 4U/400 cases but it does get a bit 'toasty' in the summer heat at the 'nominal' 1.6A bias - I've allowed a small gap between the bottom plate and the heatsinks for an extra cooling draught and that helps and it has about a 23+*C temp rise.
I think the idea that the extra size of the 4U/400 case is so you can use the same case for adding extra things later and also to keep the power devices and the caps that much cooler, but it is a big unit - even the 3U case isn't small at about 6" high and still rather long at 400 and from most posts it seems quite satisfactory for the job.
I'm a bit conservative with electros and tend to use a higher voltage range than required hence either 40v ds or 63v dc for these First Watt amps - they're a bit dearer, etc but ....
I was initially a bit sceptical about the small sizes of some of them like the Panasonics, for example, but they work just fine - even the long life Epcos are now much smaller and quite a bit cheaper, if you can find some - looking at some of the supply houses, it appears that there's a general shortage of these electros - that makes it a bit awkward ...
I think the idea that the extra size of the 4U/400 case is so you can use the same case for adding extra things later and also to keep the power devices and the caps that much cooler, but it is a big unit - even the 3U case isn't small at about 6" high and still rather long at 400 and from most posts it seems quite satisfactory for the job.
I'm a bit conservative with electros and tend to use a higher voltage range than required hence either 40v ds or 63v dc for these First Watt amps - they're a bit dearer, etc but ....
I was initially a bit sceptical about the small sizes of some of them like the Panasonics, for example, but they work just fine - even the long life Epcos are now much smaller and quite a bit cheaper, if you can find some - looking at some of the supply houses, it appears that there's a general shortage of these electros - that makes it a bit awkward ...
F6 can be use with 3ohm load speaker ?
My 3way Diy speaker is using bi amp
Plan to use tweeter and mid are using tube power and 2x6ohm bass driver by first watt F6.
I use before tube and lazycat power amp same speaker too ,but power amp is fire .
I really scare to see again if I use f6 power amp
For these driver .
My 3way Diy speaker is using bi amp
Plan to use tweeter and mid are using tube power and 2x6ohm bass driver by first watt F6.
I use before tube and lazycat power amp same speaker too ,but power amp is fire .
I really scare to see again if I use f6 power amp
For these driver .
It depends on where the "bass" crosses over to the high frequencies. Somewhere around 800Hz is the middle of the audible 20Hz - 20kHz frequency range, so it may not be just "bass". Otherwise, we could just use any old speaker for the "bass".
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... we could just use any old speaker for the "bass".
Um, I'd suggest you rethink this as "Getting the bass right" is the most trouble-some challenge in any domestic listening room and using "any old speaker for bass" is asking for trouble, despite the first impressions and cost saving - high quality bass is not cheap plus room treatment adds considerable to that.
I'm with Nicoch in that using the F6 just for bass is a waste of potential and suggest a good quality higher power class AB amp for bass duty for wider speaker choice such as Link Transform - possibly, even a 2nd hand amp too.
[technically, the bass range is actually 30 <-> 120Hz but most of us use somewhere around 40 <-> 250Hz].
Um, I'd suggest you rethink this as "Getting the bass right" is the most trouble-some challenge in any domestic listening room and using "any old speaker for bass" is asking for trouble, despite the first impressions and cost saving - high quality bass is not cheap plus room treatment adds considerable to that.
I'm with Nicoch in that using the F6 just for bass is a waste of potential and suggest a good quality higher power class AB amp for bass duty for wider speaker choice such as Link Transform - possibly, even a 2nd hand amp too.
[technically, the bass range is actually 30 <-> 120Hz but most of us use somewhere around 40 <-> 250Hz].
As I've found out moving into a new house. Same F6s, same speakers, a whole lot less bottom end.
A little help requested.
A channel of my F6 has developed a hum. While it passes a signal and plays, the gain is definitely lower than the working channel.
Hooking her up and checking bias drop over R2, starting from cold, good channel runs up to and settles in as set (close to 500mV), bad channel runs up to about 440, then slowly dwindles its way down to low 200s. Adjusting P2 brings it up a little, but then it settles right back down. I kept adjusting it and suddenly it started climbing and running away, but I shut it off before any magic smoke was released. I brought P2 back down to its current behavior- from cold, it ramps up to 440ish, then dwindles away.
I thought perhaps the voltage into the gate of either of the MOSFETS was bad, but the zener's hold steady and signal passes.
Resistors check out across the board comparatively; the 3W source resistors provide consistent drops and measurements as I check the bias.
Thoughts or suggestions?
A channel of my F6 has developed a hum. While it passes a signal and plays, the gain is definitely lower than the working channel.
Hooking her up and checking bias drop over R2, starting from cold, good channel runs up to and settles in as set (close to 500mV), bad channel runs up to about 440, then slowly dwindles its way down to low 200s. Adjusting P2 brings it up a little, but then it settles right back down. I kept adjusting it and suddenly it started climbing and running away, but I shut it off before any magic smoke was released. I brought P2 back down to its current behavior- from cold, it ramps up to 440ish, then dwindles away.
I thought perhaps the voltage into the gate of either of the MOSFETS was bad, but the zener's hold steady and signal passes.
Resistors check out across the board comparatively; the 3W source resistors provide consistent drops and measurements as I check the bias.
Thoughts or suggestions?
