F5 Listening Impressions & Discussion

Unless your amp has more than 100% efficiency, the power at the output has to come from somewhere... the AC from the wall.

What is the typical efficiency for a Class A P-P amp?

So, take the total draw from the wall and multiply by the typical efficiency, that is still likely more power than the amp's output!

Btw, it's closer to 31 watts... I didn't bother to plunk it into the ohm's law formula to see, but seat of the pants, that's about right...

_-_-bear
 
Offtopic
Pulse or instantaneous or what ever Power came from what is stored in the caps and with 50mU and 200 mm of 2.5 wire is enough.

What eficency of Class A got to do with it most of it is lost as heath while signal is zero pushing me on posting more wrong numbers?

You still going on a bit triing to teach math to one that does not realy care much for it.

Already said I did the wrong thing by posting that number and put up with to full sides of Bon Iovy as self punishment can we go back on topic now.


Cascode F5 tried one channel on my totaly subjective set up (poor SS1 pre for now)
much more natural and less harsness in the Hi band.
Worth it?

IMO yes.
 
The efficiency of Class A has everything to do with it!!

No matter what you may have stored in the caps, the amp still can not deliver or swing more than the circuit design will permit.

Fwiw, Class A PP does NOT change power between sitting around and running a speaker!
Assuming you stay in Class A, and don't swing into class B at any point. That's not strictly correct, but close enough for this discussion and in any event it's within 3dB worst case, iirc.

I do not care that you posted the wrong number, I'm not big on analyzing everything down to some decimal place, it's more important to get the concept and to be close to how it is working.

_-_-bear
 
If you would like to experiment a little, I have a suggestion for a trick to 'see' the clipping starting, by using the limiter circuit.

If you dare, take out the collector of the two limiter transistors and connect them via a 3k reistor to a LED. When the circuit triggers, the light starts.

OK, OI understand that is not what you like (dangerous area?),
then double the transistor and take the collector of the doubled one out like above.
Looks like a fancy way to really see it. - This should work in life music.
Might add a little cap to make the light shine longer.
albert
;)
 
Cascode F5 tried one channel on my totaly subjective set up (poor SS1 pre for now)
much more natural and less harsness in the Hi band.
Worth it?

IMO yes.

Interesting Bksabath. Have you tried the balanced and cascoded version. What about Juma's version with 2sk2013/2sj313? His version sounds good enough that i am going to build a preamp version for BA outputs like BA2 ad BA3.
 
Hi buzzforb

I have not tried the balanced version so far for 2 reasosns.

1 ) I have run out of Kerafol 86/83 I got same of it camming in next month.
2) I was going to build Pumpkin but I can not get the boards and matched dudas.

Yes I know I could make my own boards but I think it is more "moraly" correct to pay a bit of money in this case.

I am not ready to try the Juma version altrought from what I have read it is well worth a try.

Agree with you BA2 BA3 are on the plan (my sinks should cope with it thats why I got 2 maybe 3 time big enough for a F5 and space on them for at least 12 Mosfets), truth is I played a bit with OP amps before so I am realy new to this and the F5 is such a simple and EXTREAMLEy rewarding project that IMO one wanting to Learn things could not pick a better one.

F5 as pre again that is a very good plan.

One thing is in the back of my mind

Papa mentioned a possible F6 or F7 so would I have enoug spare cash to dump my F5 efforts and start with those new ones?

I supose I culd sell the VR4 (20 miles to the gallon) and get an Astra instead.

Since the post you quoted is a month old..

I have the 2 channels running in cascode since that last post and I can confirm my impression of beter HI (less harsh) and much more slam.

I must say this is my personall impression probably I am deluding myself but at least I give it a go.

I am not going to say I can not be done because such and such said so if you catch my drift.
Eventualy I could fit the 2 different boards and do same back to back testing but I got quite lazy latley spending to much time rediscovering my record collection...

I must say a real + would be to be able to listen to somebody else efforts and share opinions maybe over a few scoops.
 
--- they sound wonderful, relaxed and very clear highs, very good bass, mid range was also very good but the clean highs were what impressed me most. And, the amp is dead quiet inbetween - it's almost shocking when the music starts again.
--- what particularly stood out was how this amplifier was able to control the Quads. Finally a good amplifier for these speakers!!! Before, I felt the highs were not good and even considered servicing, now I know everything's fine with the speakers - it was a case of amplificus notfittus ;-)

thank you Nelson for this nice design, I like it a lot! And my next build will be monoblocks with bridged F5s and a better power supply...
sorry for the long post
alfred

Support that, I have had a long struggle for years and could not give up. Oh, how often I thought of setting them for sale. Yes, with tube amplifiers the mids shine (warm) but elsewhere there is lacks. I had the Le Monstre, built in 1984, but that is good for high efficiency units (horn & 103Sigma) not for a Quad. I tried all kinds of tube amps - SE lacks highs, PP tends to have ringing or metallics.

My new F5 brings up the best in my Quad ESL 57.
The F5 is slightly laid back, has an effortless presentation of instruments and groups, shines in the highs and mids (those little things the mixer thinks we like in the bakkgrounds), gives very convincing voices without nasality, and slams the bass when needed in a proportionate way. Yes, voices, they are marvelous.

Funny is I tweaked a bit with feedback (standard it gives 2,1 MHz, and even 5,6 MHz I can see on the scope) so I went for a feedback cap of 2,7 nF - above 1MHz. But wow, you can hear that on the speakers. Without caps it is open and laid back, with, the sound gets like vertical just a bit, sometimes edgy.

NP, what a nice design. Kudo's
albert
 
I'll let you know how the pre-amp sounds. I don't want to build the standard F5 because it seems redundant. Having pre-amp in front of F4 should give me a pretty good idea. Going to put all FE's in small cases and make it so they can be interchanged with BA outputs. Maybe doing AMB volume control in seperate enclosure as well. Thought about LDR based volume but can't decide if the warpspeed is too expensive now. FUN,FUN,FUN
 
Member
Joined 2006
Paid Member
The F5 is hard to beat. I've built a lot of these variations. I think the F2J atmospheric presentation and highs are even better, but it can't always deliver complex stuff. I think I've said before, I find the R1 variation with FQA's a bit more laid sweet sounding, with a little less dullness than the toshiba's-which I enjoyed for quite some time.
 
The F5 is hard to beat. I've built a lot of these variations. I think the F2J atmospheric presentation and highs are even better, but it can't always deliver complex stuff. I think I've said before, I find the R1 variation with FQA's a bit more laid sweet sounding, with a little less dullness than the toshiba's-which I enjoyed for quite some time.

Are you talking about the Toshibas in Juma's version. I listen to FR drivers like you, so your advice is helpful.
 
Member
Joined 2006
Paid Member
Are you talking about the Toshibas in Juma's version. I listen to FR drivers like you, so your advice is helpful.

I have those Fets too - it's on the bucket list of boards to build. I was thinking of using just two or even one-
These are the big TO-262 (I think) Toshibas.
At first I loved it though, better nuance in detail.
I've heard good things on the little one's for sure.

Too bad alot of this stuff is obsolete. I've been hoarding what I can.
I must try some TO-220 FQPs as well, since they are available online for reasonable costs. Reasonable inexpensive is a principle I like to adhere to, even if in practice I dont always achieve it. I moved to solid state after transformers and copper prices shot out the roof.
 
I can only say that you need to try the Juma version.Very simple and there is evena layout for etching your own boards. I have some fets i can sell you for $5 per pair matched to .1V. I coming off Aleph J monoblocks and like this better. At first i thought it was cold, but after listening in my main system, it is wonderful top to bottom. Has much better control over low end.
 
The F5 is hard to beat. I've built a lot of these variations. I think the F2J atmospheric presentation and highs are even better, but it can't always deliver complex stuff. I think I've said before, I find the R1 variation with FQA's a bit more laid sweet sounding, with a little less dullness than the toshiba's-which I enjoyed for quite some time.

Hi Tea-Bag,
The "R1" variation you mention, that's the one with .68ohm R7/R8, 4.7K R1? Did you use 2SJ108/2SK370?
http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-1086.html#post2667669
 
I have those Fets too - it's on the bucket list of boards to build. I was thinking of using just two or even one-
These are the big TO-262 (I think) Toshibas.
At first I loved it though, better nuance in detail.
I've heard good things on the little one's for sure.

Too bad alot of this stuff is obsolete. I've been hoarding what I can.
I must try some TO-220 FQPs as well, since they are available online for reasonable costs. Reasonable inexpensive is a principle I like to adhere to, even if in practice I dont always achieve it. I moved to solid state after transformers and copper prices shot out the roof.

Hi Tea bag I have 100 (well almost as I am using same)
FQP19N20
I am using them with the FQA12P20 complements witout problems

If you need same let me know
I am matching them at 24 V 2A constant 50 C
 
Member
Joined 2006
Paid Member
Hi Tea-Bag,
The "R1" variation you mention, that's the one with .68ohm R7/R8, 4.7K R1? Did you use 2SJ108/2SK370?
http://www.diyaudio.com/forums/pass-labs/121228-f5-power-amplifier-1086.html#post2667669
Yes, that one.
Just 2SK170, 2SJ74's. (I got from a member here)
I used no P3, std 10R for now. I have no distortion analyzer. I am interested in getting a USB solution if I can find one.

Hi Tea bag I have 100 (well almost as I am using same)
FQP19N20
I am using them with the FQA12P20 complements witout problems

If you need same let me know
I am matching them at 24 V 2A constant 50 C


I am all set for now, I have 25 pairs of the FQA N's and P's:D
Although the little critter one's should keep the amp build able with fairchilds into the future.
I figured since Papa was using them in R1, then I should go that route, not standard IRF's or Toshiba's
 
Last edited:
So I just switched my F5 from CRC to CLC using a 2mH inductor. The supply rails dropped a little and I biased the amp at .5V. Here are my initial findings, I have not had much time listening to it.

Bass is MUCH better, I didn't realize it was missing until I made the change. Everything sounds like it has much more weight behind it.

Dynamics seem to be a bit less, personally I love dynamics so I am not sure if I like this change. I am not sure if this is due to the lower rail voltage or something else going on. Would bypass caps possibly improve this? What about an increase in bias, the amp runs pretty cool.

The sound is a smoother, this could be due to the change in dynamics though.

I only have a few min on the amp but I will update this once I have some more listening time on the amp.


Next planed mod - P3.