Request : DIY PASS LAB Power Amp GroupBuy

[jls001]

Sajith,
Like Mishra said there are plenty of options. It need not be Class A only.

But class A is special One needs to live with the heat generated, and the slowish warm up time of about 1 hour. In my experience of running a 60W hybrid tube amp and pure class A solid state outputting 80W in my setup, I can tell you that the tube hybrid runs much hotter than the solid state.

Your ATC's are 85dB@1m and spec'ed at 112dB max. I figure thats 27dB, which needs 10log27 = 14W of real Watts. I trust the ATC spec sheet and Stereophile reviewed it very favourably here.

From the limited that I know of ATC speakers, they need the best power they can get (which speaker doesn't? :lol due to their transparency and great dynamic prowess, and they can play real loud without causing fatigue. I guess that would be cmsajith's experience as well.

I am a fence sitter at this point of time. I honestly don't need another amp but find the Pass DIYs very tempting. Till a few days ago, I was seriously contemplating the F5 till I was unceremoniously told that it produces only 25W. I doubt that will suffice for my speakers.

 

[sachu888]

I am a fence sitter at this point of time. I honestly don't need another amp but find the Pass DIYs very tempting. Till a few days ago, I was seriously contemplating the F5 till I was unceremoniously told that it produces only 25W. I doubt that will suffice for my speakers.

Now first watt has F5 Turbo,power can be extended upto 100W/channel.
http://www.firstwatt.com/pdf/art_f5_turbo.pdf

Regards,
Sachin

 

[jls001]

Now first watt has F5 Turbo,power can be extended upto 100W/channel.
http://www.firstwatt.com/pdf/art_f5_turbo.pdf

A fellow forumer in Mumbai had purchased the boards, power supply board, power supply components and the toroid. I just had to buy these from him, get myself the active components, heatsinks and cabinet and I would have been on my way to the build but for my belated knowledge that it is rather under powered for my speakers.

I am not too sure but the existing board may not be easy to modify for the higher power.

 

[pdhanwada]

Last few days have been going thru the F5 reviews on the diy audio.com
The dual output one which anilva built should provide 50W in class A. WHich I feel is pretty good for medium to high efficiency speakers.

Sajith,

Alpeh -4 is 100 W per channel. It might help u out on your low efficiency speakers. It has bigger heatsink than the F5.

Thanks
pandu

 

[jls001]

http://www.firstwatt.com/pdf/art_f5_turbo.pdf

I read through the whole article. This is crazy. I think I should queue up for the inevitable build on DIY

 

[cmsajith]

My purpose for a new amp is to have atleast a significant step up from my current Quad 909 (class A amp with current dumping for high power which is ~140w @ 8 ohms). Moreover on comparing it with symphonic line RG1, I didnt find a huge difference except a slight harshness at the top end and the bass in not as tight as RG1, but the dynamics, tone esp mids were very good.

To be honest my only worry is that if i couldnt get a significant difference, the entire effort will be wasted. please advice if I am wrong...

 

[pdhanwada]

DIY is usually meant for learning.

It may be better or may be not. Only it can be found by trial and error.

DOnt go by watts per channel on the amp.

My AMp has 200Watts per channel. Kevian bought a 30 Watts per channel amp, it was as good as my amp.

 

[Tanoj]

Today i noticed that my Amp has a pre out

however there is jumber on that which goes to the Main in

i can remove that jumper too , so i removed the jumper thinking that my amp will work like a preamp , so i connected a rca from pre out to the aux in of my Altec lancing 5.1 , however there is no sound output

so i had put back the jumper

what is pre out ?

 

[omishra]

DIY is usually meant for learning.

It may be better or may be not. Only it can be found by trial and error.

DOnt go by watts per channel on the amp.

My AMp has 200Watts per channel. Kevian bought a 30 Watts per channel amp, it was as good as my amp.

Yes you are right. My amp designed for 25W in 8ohms / channel. But it delivers ~42W. Same time for 4 ohms it delivered >70W.

BTW this new design is quite interesting. As always simplicity is best thing in Nelson Pass designs. Looking forward.

 

[doors666]

Today i noticed that my Amp has a pre out

however there is jumber on that which goes to the Main in

i can remove that jumper too , so i removed the jumper thinking that my amp will work like a preamp , so i connected a rca from pre out to the aux in of my Altec lancing 5.1 , however there is no sound output

so i had put back the jumper

what is pre out ?

pre out is basically pre-amp output. in your case, it looks like its straight input signal being sent out from the pre outs due to the jumper. put the jumper back in and then try it.

 

[sunilj]

Sajith,

At 140/250W the 909 will be a hard act to beat with a DIY solution. Think many-many output devices.

Looking at it logically....it weighs 13Kg. 140W @78% efficiency means a min of 38-0-38 / +-53V (38x1.4) tranny. 140W needs about 4.75A, lets say 6A. So the transformer is ~ 500Va (38*2*5).

This leads me to think - are the ATC's current starved with the Quads. I haven't heard of a >4ohm capable amp with 500Va.

Just food for thought...I'm not technically inclined, these numbers can be got of any decent electronics book

 

[sunilj]

WOW, I just found this. The tranny is a 500Va but 80V secondaries, which means 3.125A capable.

C'mon you technical guru's, the numbers don't add up. What wrong with this picture ?

Sajith, these guys do upgrades of the 909, might be worth a shot.

 

[cmsajith]

Thanks Sunil on your comments...
I am also thinking on the Quad 909 upgrade and going back to my previous plan (Biamp with another Quad 909 and do the upgrade for both). Dada Electronics is very well known for Quad upgrades and I had contacted them before on this (thru' QuadHiFi yahoo group, one of our old member is also there, Arup)
I am trying to figure out a best way to get the parts imported here.

 

[sunilj]

Sajith,

You mean bi-wire with a separate amp or will you be separating the internal x-over on your ATC's .....sacrilege.

With Bi-amping you need to separate the frequencies that are going to the drivers and the only way with that is to disconenct the internal crossover.

All in all, the extra 909 cost might be worth putting into a high-power DIY effort.

 

[GeorgeO]

Another option is to use the Hypex modules.

 

[kroyin]

If you have a question about 'How much Power will i need?' the following link might be helpful

A Test. How much Voltage (power) do your speakers need? - diyAudio

 

[doors666]

looks like suds is reviving the gb for pass f5 on diyaudio.com forums. anyone interested in it can go for it.

 

[doors666]

If our group buys gurus aren't yet tired and bored of arranging group buys, then O2 headphone amp is another good idea. its open source hardware, so the gerber files etc are also available. cost is around 30-40usd only for pcb and parts from mouser.

Any one has any idea about the fc100 group buy going on at diyaudio. what are the specs of this amp, searched but couldnt find it.

 

[anilva]

looks like suds is reviving the gb for pass f5 on diyaudio.com forums. anyone interested in it can go for it.

I will not recommend this particular source. Quite erratic on response and commitments.

 

[omishra]

We can think of ourselves, but only problematic thing I can see is chassis with those large heat sinks. Because PCB parts and transformers can be arranged. But that chassis is big hurdle.