F6 Illustrated Build Guide

[ItsAllInMyHead]

^ Given the order of events, here's what I'd consider doing.

Other than cutting the secondary leads shorter, did you change anything else AT ALL other than the mount? No barrier strips or anything else adding to the parts list? Post a pic of your mounting. Also, look up posts for shorted turns. That doesn't sound like your situation, but make sure you mounted it properly.

Prep

• Remove transformer from mount. Set it outside again if wires permit. Otherwise determine how to run w/o mount safely.
• Check fuse and replace if needed.
• Disconnect PSU from amp boards
• Visually inspect PSU for any damage. Sniff test.

Check for any PSU shorts / issues / measure rails. Install toroid in chassis.

• Hook up DBT and/or Variac
• Fire it up (slowly with Variac if equipped). Check and report. Fix any issues
• If everything looks good. Disconnect DBT. If not fix / report.
• Measure rail voltages (ramp up slowly with Variac if equipped)
• Make sure to check posts re: shorted turns and adjust mounting technique if needed.
• Put the toroid back in the chassis. Adjust mounting if needed.

Inspect amp boards, check, and listen to music... You didn't mention any smoke, so that's potentially good.

• Inspect amp boards / sniff test
• Hook up one amp board at a time and do DBT (and/or Variac) / power-up check. If good, remove DBT/Variac
• Hook up both amp boards
• Power up
• Listen to beautiful music

Others may have better suggestions and/or additions, but that's the general sequence I'd run through. Good Luck!

 

[Mikerodrig27]

Now the amp won't turn on

Hey Arthur,

Please post some pics of your work in detail from different angles to show as much as possible. Also, note whether you built the amp to the stock schematic etc.

I would try taking the channels off of the power supply and run the amp on a dim bulb tester first. Check voltages etc. Then install one channel, test, confirm functionality. In your case, it may be a good idea to do one channel at a time confirming their functionality. Take pics first though if you are able.

Best of luck!

 

[platon.rado]

The sound with the green LED is better

 

[Zen Mod]

hardly

just autosuggestion

 

[sndlvr]

Hey folks, a quick update and another thanks. finishing this has made be disproportionately happy this week 😁

I’ve tidied some cables, but I need to address the transformer and that was a pain to fit. I might talk to a pal to help make me can or a couple of L brackets to stand it up and shield it. I can hear a buzz if I stick my ear over the case and the same tone coming through the drivers. it’s not loud and you have real close to notice. The cables outside are a rats nest too. So a bunch of thing to address in slow time.

Bias is even, 0.604/0.00 on both sides. It spent about 10 hours at 0.500/0.00 last week and the increase in bass is amazing since raising it. Well not just bass, it’s all bigger. The heat sink is about 42 degC but I’m getting mixed temps on the 2nd pin so loathed to increase the bias at the mo, until I get a better way to measure temp (I’ve got heat transfer paste on the thermistor).

I really am super stoked about it. My good lady has passed comment too, so results and plaudits all round.

Hats off to papa and the gang on here.

Alistair, I appreciate your comments on sound quality as it is affected by bias. My F6 isn’t fully functional yet but playing with the bias setting is definitely a question on the horizon.

 

[sndlvr]

Hi folks,

Had my F6 up and running since last weekend (biased beautifully to about 0.6v, 0v offset) with the transformer simply plugged and resting outside the chassis while waiting for an L bracket to arrive. The amp sounded amazing (so much better than the Prima Luna I've been listening to...).

Yesterday, upon receiving the L bracket, I drilled the baseplate and fixated the transformer vertically after trimming its secondary leads. Things went very bad from there: turning the amp on I noticed the PSU and amplification LEDs kinda wavered strangely before shutting off. Then went back on very brightly... Before shutting back off. Now the amp won't turn on (guessing the fuse is out, have to confirm tonight).

While the amp was on, I managed to check voltages across PSU rails and things looked rather normal. AC on these was a good bit higher than when I measured the PSU unloaded, which seems like expected behaviour.

My intuition tells me it's a short, do you have any recommendation as to how to start the troubleshoot? First time builder here.

Thanks in advance 🙏
Arthur

@Roosterwing, I am a neophyte like you but based on good advice I recently received I would disconnect both channels from the PSU then start the PSU on a dim bulb tester, if things look normal then I would connect One channel at a time well still being on the dim bulb. This way you can isolate where the short may be. Assuming your wiring is all as it should be I would guess that there is a possibility you could have blown a MOSFET or two and this would be the cause of the short. Those with more experience please feel free to jump in and correct anything that I have said.

 

[Roosterwing]

Hi everyone and thank you all for getting back to me with advice.

First let me state that the amp was built religiously following the values indicated in the build guide. I got JFETs, MOSFETs, Zeners and boards from the DIY Audio shop and followed the schematics as closely as I can. Only difference is that having only one set of primary wires on the 400VA transformer, I connected the single CL60 in series (running on 230V here). It was advised to me on this thread last week.

Now to be honest I feel extra shameful with regards to how things went after my post yesterday. As I was taking the chassis and boards apart for proper inspection, a stray screw fell out from under the the filtering board. I think I've found the root of my short...

Unfortunately I don't have either variac or dim bulb tester. All components and all connections showing no sign of damage whatsoever, I chose to put the unloaded PSU back together as orderly as possible (as seen on attached messy picture, chassis is too small). I powered it and voltages were the same as they'd been before the incident. Only changes were:

1. PSU LED (only one lighting up since the beginning, I must have screwed up the polarity of the other one) was a LOT brighter than it used to be, almost blinding : I'm thinking the LED resistor is cooked.
2. The V+ and V- voltages take ~5min to reach zero after switching off an unloaded PSU. Would that mean the bleeding resistor(s) is fried too? Both are close to each other on the board after all.

At any rates I decided to check with one of the amp boards. Things went nicely and the first one turned on and showed the correct bias.

That's when things went south. After powering off I prepared to connect the second amp board to check it as well, and touched the IEC socket with the pliers I was holding. It was late, and being a tired and forgetful idiot I had not removed the power cord. I got my pliers a big spark that blew my spare fuse. Now waiting for the ones I ordered to arrive and once again connect and test things one by one, in a more careful way this time.

I will take and post more pictures in my next update.

 

[Mikerodrig27]

Well, I don't think you're screwed yet. Get that new fuse in there and see what happens. Maybe disconnect the channel again since you have the screw terminals. I think it is supposed to take a while for the bleed resistor to drain the caps without the channels as a load on the power supply.

 

[Mikerodrig27]

Question. I am going to order some transformers for my F6 to go dual mono. I currently have a Antek 400va 18v which I can use for another project (which is what sprung this idea). I want to install two 200va 20v transformers on the F6. Until I get the 2nd set of bridges, CRC board etc, can I tie the secondaries of the transformers together to simulate having one transformer with two secondaries?

Thanks!

 

[6sX7]

Question. I am going to order some transformers for my F6 to go dual mono. I currently have a Antek 400va 18v which I can use for another project (which is what sprung this idea). I want to install two 200va 20v transformers on the F6. Until I get the 2nd set of bridges, CRC board etc, can I tie the secondaries of the transformers together to simulate having one transformer with two secondaries?

Thanks!

No direct experience with doing it as I haven't done it myself. I asked the same question in my quest for monoblocks but didn't get a firm answer but got some questions that pointed me towards not doing it. I took away that there could be current hogging in one over the other. Also, could be some odd "resonances between them if their winding ratios aren't close enough.

I found this article related to large power distribution in doing a quick search. https://electrical-engineering-portal.com/principles-of-transformers-in-parallel-connection-1

 

[Zen Mod]

Question. I am going to order some transformers for my F6 to go dual mono. I currently have a Antek 400va 18v which I can use for another project (which is what sprung this idea). I want to install two 200va 20v transformers on the F6. Until I get the 2nd set of bridges, CRC board etc, can I tie the secondaries of the transformers together to simulate having one transformer with two secondaries?

Thanks!

yes, just take care of phasing and that's it

 

[Mikerodrig27]

Zen Mod & 6sX7, thank you. That clears it up.

 

[6sX7]

Zen Mod & 6sX7, thank you. That clears it up.

Yeah, I think I'm being overly cautious. The article linked doesn't help much because it is for very large power distribution transformers. Since I have a couple 220VA Hammonds sitting around now, I should hook them up and see for myself. As long as it is a fused circuit, I'll be ok, right?

 

[jameshillj]

As your monoblock assembly is 2 separate single channel amplifiers (in the one case), each amplifier will require separate central 0v ground lift components - often forgotten.

 

[Mikerodrig27]

Okay so each should have it's own dedicated CL-60 thermister coming off of chassis ground? Than you for that!

 

[Roosterwing]

My F6 lives! after getting my new fuse in, putting things back together, and testing, the amp is back to normal and sounding great. I love this first diy amp, and enjoyed building it so much I am already planning for a pair of M2 monoblocks

Quick question regarding amp layout:
as you may see on the attached picture, my chassis is small and there's not much space in between the different elements. Fortunately it is completely silent on my 96Db speaker. My question is: although it is silent, can the proximity between the toroid and the Jensens still affect sound quality? Or as long as it's silent, it means it's not interfering in the signal?

Thank you all for your super quick responses during my troubles

 

[TungstenAudio]

As long as it is silent, you are good to go. The Jensen transformers seem to be less susceptible to interference.

 

[6sX7]

Quick question regarding amp layout:
as you may see on the attached picture, my chassis is small and there's not much space in between the different elements. Fortunately it is completely silent on my 96Db speaker. My question is: although it is silent, can the proximity between the toroid and the Jensens still affect sound quality? Or as long as it's silent, it means it's not interfering in the signal?

Congratulations and enjoy!

The way you have them set up, will not affect sound quality. You've got them as far apart as they can be without going to a separate PS chassis.

 

[iplayforme]

Hello,

Can someone tell me what voltage LED to order for the F6 boards.Or any other important value if it is important. I have found, best I can tell, everything else but not that. I haven't actually found a BOM. All those links are dead apparently so I pieced everything else together without much trouble. I tried the search function but LED appears quite a bit so I think its probably in here but a needle in the haystack.

Thankyou

 

[zman01]

iplayforme,

The LEDs suggested by 2 picoDumbs were LTL-4231N.

And here you go with a post by diyAudio member mikerodrig27 that nicely shows how to do the LED mod:

https://www.diyaudio.com/community/...y-dumbest-idea-yet.348969/page-5#post-6851970