Smile, this is not part of the amplifier, it's simply a chair!
An externally hosted image should be here but it was not working when we last tested it.
WOW !!! what a good idea,
a chair with F5 as a cushion, that will be warm to sit on during the cold winter months.😀
a chair with F5 as a cushion, that will be warm to sit on during the cold winter months.😀
I love projects wich are running from the beginning.
No debugging needed (I can assure you, it is not always like this) 🙂
It's the first half hour, the amp is playing music. I set bias at 1A.
The heathsinks and the trannies are getting warm but not hot. I can touch it as long as I want.
Maybe I go up to 1.3A
But I have to look at the rails voltages: actually, with 1A each, I have rail voltages of +-11.2VDC. It should not drop much more, when I increase idle current, otherwise I will loose all headroom.
Here a more inside view:
Franz
No debugging needed (I can assure you, it is not always like this) 🙂
An externally hosted image should be here but it was not working when we last tested it.
It's the first half hour, the amp is playing music. I set bias at 1A.
The heathsinks and the trannies are getting warm but not hot. I can touch it as long as I want.
Maybe I go up to 1.3A
But I have to look at the rails voltages: actually, with 1A each, I have rail voltages of +-11.2VDC. It should not drop much more, when I increase idle current, otherwise I will loose all headroom.
Here a more inside view:
An externally hosted image should be here but it was not working when we last tested it.
Franz
I thought you said your transformers are 108VA ?
1.3A bias for 2 channels on 108VA, magical medical transformers ? 😱
1.3A bias for 2 channels on 108VA, magical medical transformers ? 😱
Now, the amp is running about one hour.
The room temperature is 24C.
The heathsinks are at 45C nearby the transistors, the trannies iron 52C.
So, I could go to higher bias.
What do you think?
Franz
The room temperature is 24C.
The heathsinks are at 45C nearby the transistors, the trannies iron 52C.
So, I could go to higher bias.
What do you think?
Franz
maybe just settle where DC adjust is most stable ?
probably need to adjust again after some time
why not just leave it till then
give it a listen, and report, please
probably need to adjust again after some time
why not just leave it till then
give it a listen, and report, please
I'd reckon you end up with less than 3W continuous power per channel, for 7 times the dissipation.
Like a tube amp, isn't it?
The little difference: the F5 is sounding awesome...
Jacco: I build this amp to drive my high efficency midrange and highrange horns. Not more power needed.
Franz
/Edit
To be honest: 4 times dissipation is more exactly. Like the big F5.
Last edited:
Hmmm, I think these kits are not authorized by Nelson...
Look for the seller tubeshunter at ebay.
Franz
Look for the seller tubeshunter at ebay.
Franz
Exactly!!!
So DON'T look for sellers on ebay. There's two sellers through approved group buys on the forum, cviller and Peter Daniel
Talking of eBay, I've been looking at chassis' and heatsinks, and I came accross something perfect for an F5 though Krell might not be so happy about the ready availability:
A HIEND full Aluminum power AMP Chassis?box) 16KG on eBay (end time 21-Aug-10 10:59:06 BST)
Looks perfect for an F5 though, but pricey.
Then there's this, but I'm not sure it can take the heat:
Silver Aluminum Audio Power Amplifer Chassis Case D988 on eBay (end time 13-Aug-10 18:00:58 BST)
The Krell might be a reasonable way to get a top notch chassis. Making one from Conrad sinks and sheet alu might be pretty much as pricey, though I've never done it. Whacha think?
A HIEND full Aluminum power AMP Chassis?box) 16KG on eBay (end time 21-Aug-10 10:59:06 BST)
Looks perfect for an F5 though, but pricey.
Then there's this, but I'm not sure it can take the heat:
Silver Aluminum Audio Power Amplifer Chassis Case D988 on eBay (end time 13-Aug-10 18:00:58 BST)
The Krell might be a reasonable way to get a top notch chassis. Making one from Conrad sinks and sheet alu might be pretty much as pricey, though I've never done it. Whacha think?
These eBay boards are nice, but have a bug on the input jfets (With the supplied jfets), the serigraphy and the holes are bad (On one of the jfets).
I have a pair of these boards on my first F5, as well the cviller board (my next approach to the F5 nirvana)
Cheers
Another thing to consider, and I quote from the Krell eBay listing:
"if you are a supper completist,don't bit it please......"
So, don't bid unless as a rule, you leave some of your evening meal. 🙂
"if you are a supper completist,don't bit it please......"
So, don't bid unless as a rule, you leave some of your evening meal. 🙂
The italian cases are nicer and cheaper, the F5 works well on the Pesante Dissipante 4U 30cm deep.
Hi-Fi 2000 contenitori per l'elettronica, case modding HTPC, Galaxy, rack, DIYaudio, computer cases, front panel express, knobs,milled Handles, milled fronts, hi-end,
Yesterday evening I replaced this two t-amps by the Mini F5 to drive the horns:
There is still one TK2050 T-amp driving the four FW250 woofers, waiting for the "big" F5.
After reajusting the levels of the crossover, the thing sounded quite fine, but I missed the magic from my other F5 experiences.
Even the small Veravox 3S I used for the inital test of the Mini F5 showed this fascination: they also play bass, driven by the F55!
After one hour, I removed the big black caps between the amp and the speakers.
Thats it! The fascination comes through now, but still missing some punch in the bass area. Waiting for the big F5 as I already wrote...
I remarked, that the Mini F5 standing in the rack and playing music, gets up to 55 degree on top of the heatsinks, about 32 degree over ambient level.
So, 1A idle current will be the max for my setup.
I will try some other bias settings as soon as I have time. Maybe I can drive the tweeters with different bias than the midrange.
Franz
P.S.
I cannot find any error with the input transistors on my prints.
An externally hosted image should be here but it was not working when we last tested it.
There is still one TK2050 T-amp driving the four FW250 woofers, waiting for the "big" F5.
After reajusting the levels of the crossover, the thing sounded quite fine, but I missed the magic from my other F5 experiences.
Even the small Veravox 3S I used for the inital test of the Mini F5 showed this fascination: they also play bass, driven by the F55!
After one hour, I removed the big black caps between the amp and the speakers.
Thats it! The fascination comes through now, but still missing some punch in the bass area. Waiting for the big F5 as I already wrote...
I remarked, that the Mini F5 standing in the rack and playing music, gets up to 55 degree on top of the heatsinks, about 32 degree over ambient level.
So, 1A idle current will be the max for my setup.
I will try some other bias settings as soon as I have time. Maybe I can drive the tweeters with different bias than the midrange.
Franz
P.S.
I cannot find any error with the input transistors on my prints.