Is anyone building the DIY Pass F-5

strider · « **Reply #160 on:** 7 Apr 2011, 02:26 am »

Smoke and solder burns whilest juggling vomiting babies (literally and not 100% literally, respectively) over the past 4 days have turned corner to one channel QC'ed, biased, and wired with the other QC'ed and waiting a couple hours free time to do the latter.

Had the trimmer pots adjusted for the Fairchilds and the Toshibas didn't like it. I changed both channels' MOSFETs out to the 'Shibas when I melted the one channel previously. No harm no foul (so far) as I had 100r resistors in series with the V+/V-. Turned the trimmers to zero, changed R3 and R4 from 2.2k to 1.5k per suggestion from the fellow who is selling the Toshibas on diyAudio.

I'll not have any real time 'til Sunday to fool with them again, but I'll sleep tonight with hope in my heart. Hope in my heart and the thought out of my head that I should shove the guts of an old gainclone in the chassis, solder the lid shut, and call it "my F5".

Russellc · « **Reply #161 on:** 7 Apr 2011, 01:14 pm »

Quote from: strider on 7 Apr 2011, 02:26 am

Hope in my heart and the thought out of my head that I should shove the guts of an old gainclone in the chassis, solder the lid shut, and call it "my F5".

No No No! Bad boy! Think pleasant thoughts, think pleasant thoughts...Guess I'd better order some resistors here.

Russellc

sts9fan · « **Reply #162 on:** 7 Apr 2011, 02:24 pm »

I have a bit of a cold so today is a perfect time to stay home and finish my F5. I have it mostly wired up and ready to go. I just need to hit a store and grab two more cheap DMMs. Fingers crossed.

Russellc · « **Reply #163 on:** 7 Apr 2011, 06:12 pm »

I'm watching!!!

Russellc

sts9fan · « **Reply #164 on:** 7 Apr 2011, 09:33 pm »

First channel up and running no problem. The bias is not perfect but I need to get two more DMMs. It made music and no buzz or hum. Now
for the next channel.

strider · « **Reply #165 on:** 7 Apr 2011, 11:01 pm »

Quote from: sts9fan on 7 Apr 2011, 02:24 pm

I have a bit of a cold so today is a perfect time to stay home and finish my F5. I have it mostly wired up and ready to go. I just need to hit a store and grab two more cheap DMMs. Fingers crossed.

Funny, I was sick today too.

Got my second channel together about 4 hours ago and am listening to music right now. Definitely needs to break in a bit, but it does sound promising.

Russellc · « **Reply #166 on:** 8 Apr 2011, 12:12 am »

Quote from: sts9fan on 7 Apr 2011, 09:33 pm

First channel up and running no problem. The bias is not perfect but I need to get two more DMMs. It made music and no buzz or hum. Now
for the next channel.

doesnt matter if it isnt perfect, as long as it isnt high....nothing wrong with letting it cook at low bias, .40 or so. You can tweek you output dc to near 0, then slowly ramp up the bias once warm.

Russellc

sts9fan · « **Reply #167 on:** 8 Apr 2011, 12:30 am »

The bias is ~0.5 with 0.0 vdc offset. Channel two is ready to bias but I doubt it will happen till sat morning.

Russellc · « **Reply #168 on:** 8 Apr 2011, 01:01 pm »

Sounds like its going fine. Sat morning when the other channel comes up and settles in, you'll be listening to beautiful music. Its almost as exciting for me watching as it is for you doing it yourself!

I think I'm ordering heatsinks, there has been so much controversey over whether or not a single pair of HeatsinkUSA's 10.08 inch extrusion would be sufficient for F-5. Testing I've seen says they are just the good side of borderline. Another well known builder on DIY says he thinks they will work, and with Kerafol pads should do just fine. I'll settle it with a build. If not sufficient, (which I'm pretty confident) I'll turn it into a mini Aleph or something. Plus, my Kerafols just got here from China! Woot Woot! I'm going to order two 8 inch slabs of the aformentioned heat sinkss, and we'll see.

Russellc

sts9fan · « **Reply #169 on:** 8 Apr 2011, 01:27 pm »

On the heatsink topic. I am using the big Conrads just like I did for my ZV9. The ZV9 draws 100W per side so 20% more the the F5. My ZV9 gets pretty warm but you can keep your hands on the fins no problem after hours powered up. After an hour or so heating up the first channel of the F5 was not nearly as warm. Of course it was open and in a cool basement. My case has a perforated top and bottom so has very good ventilation. I am just using Sil-Pads as I did witht he ZV9 which has been working flawlessly for over two years.

strider · « **Reply #170 on:** 8 Apr 2011, 02:43 pm »

The thing I'd be concerned with if using the smaller sinks is not having the option of adding the extra output devices in the future. From what I've read you'll really need a bigger heatsink like the Conrads if you add the second pair of MOSFETs per side.

Russellc · « **Reply #171 on:** 9 Apr 2011, 04:32 am »

I have an amp with the M&M which is every bit as large as the conrad, which I would have to use for a dual pair amp. The Heatsinkusa amp I'm going to build isnt intended to be a dual pair output F-5. The info I was talking about showed that there is no way that particular sink would handle dual pairs. It appeared right on the line with the standard pair.

Russellc

sts9fan · « **Reply #172 on:** 10 Apr 2011, 03:41 pm »

Channel 2 cooking after intial adjustment.

sts9fan · « **Reply #173 on:** 10 Apr 2011, 04:59 pm »

Up a d running in the main system. Both channels have a slight buzz but it's not that bad. I need to play with the wire layout a bit. Right now it's a
rats nest.

Russellc · « **Reply #174 on:** 11 Apr 2011, 03:20 am »

Great, but dont give up yet, it should be dead quiet.

Russellc

sts9fan · « **Reply #175 on:** 11 Apr 2011, 01:09 pm »

Yeah I know it should be dead quiet. I will do some experimenting when I rebias in a week. I will lift the power/signal gnd from the chassis earth gnd and see if that does any thing. Other then that I have a few things I can try but not too much. Honestly its not that bad and symetrical. So that rules out some things. We shall see

Russellc · « **Reply #176 on:** 12 Apr 2011, 11:56 am »

So how's the listening? Nice, eh?

Russellc

sts9fan · « **Reply #177 on:** 12 Apr 2011, 02:28 pm »

very nice but I need to track down this buzz.

Russellc · « **Reply #178 on:** 13 Apr 2011, 01:08 pm »

Possible instability? Hows the heat of the amp? If you check DIY I recently posted a question about checking amp instability w/o an O-scope. Replies were a nice little gizmo made from a couple of leds, and a few resistors and caps that will indicate high freq instability.

Rfi may also be a culprit. And, since its both channels equally, careful examination of the power supply is in order.

russellc

sts9fan · « **Reply #179 on:** 13 Apr 2011, 01:28 pm »

The amp is running as cool as I would expect. I am now getting distortion in the form of static in the highs. I have some work to do. I do have an o-scope I just need to harrass my buddy to teach me how to use it.