To reduce the output current you set the drive voltage for biassing the output lower (P1/P2). You do not have to change the output source resistors.
- You could lower the source resistance, but you can do that to change the output impedance/DF (lowering the value will increase DF for instance). But because the bias is variable this is not the main trick (in Hiraga's designs this is the way forward, but he used fixed drain resistors (R3//P1//R15)).
With a low load, paralleling devices helps to drive them.
The big question is: how efficient are the speakers? And how loud must they sound? Must they shout when loud (i.e. third harmonics creep in, many love that) or keep it soft & fluffy (the 1541 sound with always dominant 2nd harmonics)? If the latter (and I trust that is your style), better is increasing the idle but reducing the Vb from 22-24 volts to 18-19 volts, and give that a try.
Once built it is easy to change the idle current by changing the settings of the output stage bias, but is is a bit more work to change the Vb (I took out some windings off my transformer)
albert
Probably the F5 Turbo will not quite make Xmas schedule. Before
leaving for the coast, I fired up the prototype. Literally.
At the moment the design is destined to provide much short-term
entertainment for DIYers, what with the sparks and all. I wish I could
have had it ready for 2011 BAF...
Fear not, I'll change it.
leaving for the coast, I fired up the prototype. Literally.
At the moment the design is destined to provide much short-term
entertainment for DIYers, what with the sparks and all. I wish I could
have had it ready for 2011 BAF...
Fear not, I'll change it.
You are not telling me that a new version is coming while I ordered boards and parts for the F5 as we know it (only yesterday) ?!?!
So F5 Turbo: big changes and new PCB's ?
So F5 Turbo: big changes and new PCB's ?
..... I fired up the prototype. Literally.....
naah ...
it's not fried properly without the stone ; you still have something for sending for proper disposal
go back several posts ; you're sleeping in class
I should be building and not reading in the scarce free time.If that isn't a good excuse 🙂
I want amps to be neutral, not "shouting" or "soft and fluffy", both are not my style if that is what you thought. I don't know where that idea cam from but I don't have s single DAC with TDA1541A.
The amp will be driving Elac BS243 speakers which are not an easy load. So I thought to have it idling at low current i.e. fairly hot class AB with 0.22 source resistors and bias adjusted that 0.3 to 0.6 A will run.
I want amps to be neutral, not "shouting" or "soft and fluffy", both are not my style if that is what you thought. I don't know where that idea cam from but I don't have s single DAC with TDA1541A.
The amp will be driving Elac BS243 speakers which are not an easy load. So I thought to have it idling at low current i.e. fairly hot class AB with 0.22 source resistors and bias adjusted that 0.3 to 0.6 A will run.
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Folks, you heard the man, send everything you've not yet completely charcoaled to the Serbia outback.
I hope that , one day , my usual "proper disposal" jokes will not give me major headache .....
matched fet and ebay kits
Hi 🙂
I build the Zen v4 a few years ago and realy loved the sound, i know that amp didnt need a pre-amp to get a good volume, would the F5 definetly need a pre-amp to drive it ? line level not good enoth ?
other question is does anyone think thise two ebay kits are ok ? or best to stay with the ones on diyaudio store. perhaps the DELUXE version is a better bet, but i do not know what the benifits are in having mached transistors?
http://www.ebay.co.uk/itm/4380364731294?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
eBay - The UK's Online Marketplace
sorry lots of questions! any help apreciated thankyou!
Hi 🙂
I build the Zen v4 a few years ago and realy loved the sound, i know that amp didnt need a pre-amp to get a good volume, would the F5 definetly need a pre-amp to drive it ? line level not good enoth ?
other question is does anyone think thise two ebay kits are ok ? or best to stay with the ones on diyaudio store. perhaps the DELUXE version is a better bet, but i do not know what the benifits are in having mached transistors?
http://www.ebay.co.uk/itm/4380364731294?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
eBay - The UK's Online Marketplace
sorry lots of questions! any help apreciated thankyou!
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I would recommend the board from diyaudio store, and kits from tech-diy.com, or transistors from HA (I think) from EU.
Buying the diyaudiostore boards helps in keeping the diyaudio site 'alive'
Buying the diyaudiostore boards helps in keeping the diyaudio site 'alive'
If you buy from China, you will most likely have a problem with counterfeit parts. I agree with Tea-Bag, buying the boards from an authorized source (DIYaudio store, or Peter Daniel) is a good suggestion.
As for needing a preamp? Not necessarily... The F5 needs 4v for full output, but the need full output is usually dependent on your speaker efficiency. I have 2v sources, a buffer preamp, and 90db speakers and have little need or desire for preamp gain. But that is my experience, and as we say here in the States, your mileage may vary.
As for needing a preamp? Not necessarily... The F5 needs 4v for full output, but the need full output is usually dependent on your speaker efficiency. I have 2v sources, a buffer preamp, and 90db speakers and have little need or desire for preamp gain. But that is my experience, and as we say here in the States, your mileage may vary.
Hi,
I second the others advice to buy from the DIYAudio store or Peter Daniel's boards. For the single pair mosfet output F5, matching is not necessary. Matching is required for paralleled mosfet pair outputs or balanced (F5X).
I second the others advice to buy from the DIYAudio store or Peter Daniel's boards. For the single pair mosfet output F5, matching is not necessary. Matching is required for paralleled mosfet pair outputs or balanced (F5X).
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I saw a recent post here or another forum where some one had purchased some parts from that eBay seller and the JFETs were not those they purported to be. Could even see the abrasion where the original part numbers had been sanded off.
And, I held in my hands a F5 PSU kit from that seller and the capacitors were fakes. That is, they were not the capacitors their labels claimed they were: they were too small by 15mm as per the manufacturer's specs.
Dan
And, I held in my hands a F5 PSU kit from that seller and the capacitors were fakes. That is, they were not the capacitors their labels claimed they were: they were too small by 15mm as per the manufacturer's specs.
Dan
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I've had parts, kits, bit's & peices from both "Tubeshunter" and "Jim's Audio" over the years and never a dodgie part, and don't expect any either - same with Varlabs, hifiIC, etc - unfortunately, not all vendors are this reliable.
However, I do suggest you buy the pcbs from the diyAudio 'Store' as they're excellent quality and the Company Store" has all the parts you'll need, particularly the better Caddock resistor package (an extra, but well worth the $s)
Suggest the best power transformer your budget can stand with Shottky diodes (avoid the cheap block bridges), good quality capacitors (also look in the Group Buy & Vendor Section, this site) and decent wiring - I use dc protection/delay modules and suggest you do the same - plenty to choose from but again, avoid cheap relays, connectors, etc
It may be the last amplifier you ever build, it's a pretty good unit!
However, I do suggest you buy the pcbs from the diyAudio 'Store' as they're excellent quality and the Company Store" has all the parts you'll need, particularly the better Caddock resistor package (an extra, but well worth the $s)
Suggest the best power transformer your budget can stand with Shottky diodes (avoid the cheap block bridges), good quality capacitors (also look in the Group Buy & Vendor Section, this site) and decent wiring - I use dc protection/delay modules and suggest you do the same - plenty to choose from but again, avoid cheap relays, connectors, etc
It may be the last amplifier you ever build, it's a pretty good unit!
The last amplifier I build will still be unfinished when they put me in the ground 😉
Roscoe
I drive mine from a 2v output source, no preamp. More than enough volume. I listen to 88dB/W speakers (B&W CM-5) in a medium sized room, usually with the volume knob at 12:00, as much.
Hope it helps.
I built mine using Peter Daniel's boards, which are as compact and small as an F5 can be. diyAudio store's boards have way more optional features like paralleling mosfets, cascoding...
I am always in the process of building "The last amplifier", at least that's what the WAF belives
Never seems to end...Using an F5's gain of 6times to a source signal of 2Vac takes the maximum speaker level output to 12Vac ~= 17Vpk. This is comfortably under the clipping voltage of an F5 driving a reactive 8ohm speaker load.
That 17Vpk into an 88dB/W @ 1m speaker gives a peak SPL of ~103.5dBpk @ 1m.
Again the sums show that the gain of the F5 suits those speakers and most Members listening conditions.
I can understand that one would prefer listening at the 12o'clock position, which could be anywhere between -3dB and -20db of attenuation.
Rixsta gave us nothing to compare to. His post was almost useless.
That 17Vpk into an 88dB/W @ 1m speaker gives a peak SPL of ~103.5dBpk @ 1m.
Again the sums show that the gain of the F5 suits those speakers and most Members listening conditions.
I can understand that one would prefer listening at the 12o'clock position, which could be anywhere between -3dB and -20db of attenuation.
Rixsta gave us nothing to compare to. His post was almost useless.
Hello,
I'm ready to build my first f5. However I'm wondering about making the R1 version. I won't be able to adjust it for lack of equipmment, but was wondering if it sounded better with fixed values P3 in the middle) enough to be worth the shot.
Also looking through the forum, seems some people changed R values here and there. What are the recommended final values?
And finnally especially important, what's the story on heatsinking resistors? I'd prefer to buy some clip-on heatsinks as I don't see how I'd mount them on the main heatsinks.
Advice much appreciated.
I'm ready to build my first f5. However I'm wondering about making the R1 version. I won't be able to adjust it for lack of equipmment, but was wondering if it sounded better with fixed values P3 in the middle) enough to be worth the shot.
Also looking through the forum, seems some people changed R values here and there. What are the recommended final values?
And finnally especially important, what's the story on heatsinking resistors? I'd prefer to buy some clip-on heatsinks as I don't see how I'd mount them on the main heatsinks.
Advice much appreciated.
If you use Caddock resistors note that they will only dissipate a few watts in free air and so should be heat-sinked -- the Panasonics will dissipate more than the 3 W for which they are rated.
NP goes through the rationale for selecting R19/R21 in the original schema -- at one point, R21 changed to 22K from 10K.
NP goes through the rationale for selecting R19/R21 in the original schema -- at one point, R21 changed to 22K from 10K.
Oh boy! If you mean not even a multimeter to adjust current I wouldn't do it.
If you can afford to buy the needed heat sinks then you can afford to buy
even a cheap meter.