F5 power amplifier

[fishski13]

Originally Posted by Tyimo

Hi Fishski13!
What are those "soldering pins"? Where did you buy it?

Greets:
Tyimo

they're called "turrets" and favored by guitar tube amp builders. they need to be "staked" from underneath by either a staking tool, or a center punch. i bought them and the red G-10 glass epoxy board here: Boards and Board Making Parts. i'm sure they would be fairly easy to source in the EU.

[tinitus]

Originally Posted by Ryssen

Yes,my problem was the amp got burning hot when the dac was connected.

Wasnt it transformer coupled ?
Could it be high inductive loading causing it ?
Or maybe your interconnects, both inside and outside ?

[Ryssen]

Yes the DAC (CS4398) is transformer coupled,what to do about the inductance?
I have used the interconnects with my Benchmark DAC 1 whithout any problem(Heat).

[Tyimo]

they're called "turrets" and favored by guitar tube amp builders. they need to be "staked" from underneath by either a staking tool, or a center punch. i bought them and the red G-10 glass epoxy board here: Boards and Board Making Parts. i'm sure they would be fairly easy to source in the EU.

Thanks Fishski13!

[alazira]

Originally Posted by Ryssen

Yes the DAC (CS4398) is transformer coupled,what to do about the inductance?
I have used the interconnects with my Benchmark DAC 1 whithout any problem(Heat).

Hi Ryssen,
Do you know what the output impedance of the DAC is? If it is very high then the addition of capacitance may be creating a low pass filter. As suggested by juma I've been reading Borbely's jFet paper (http://www.borbelyaudio.com/adobe/ae599bor.pdf). It describes a type of distortion that may be relevant to you if you have a high source impedance coming in.

from Borbely
"As though the existence and size
of the input capacitance were not
enough, it is also voltage dependent,
which might cause distortion
in certain applications. Figures 10A
and 10B show the voltage dependence
of Ciss and Crss, respectively,
of the K170 JFET.
Depending on the excursion of
the input/output signal, you get a
capacitance modulation, and this
can cause distortion of the audio
signal. This shows up mostly when
you drive the circuit from a highsource
impedance."

Perhaps you can try lowering the jFet capacitance by either cascoding or increasing the source resistors (R1&R2)

[Ryssen]

This is the trafo LL1517 http://www.canford.co.uk/ProductResources/ig/2735.pdf

It says,Secondarys in series(which i have) 600 ohm,that don seem so high.If it has anything to do with it it has 1k and 2,2nf in paralell,at secondary.

[Tripmaster]

Hi there

I am currently at page 176, only another 438 and counting!

I have built various chipamps over the last couple of years and now fancy having a go at Nelson's 'F'-series. I have heard that several versions can use the same unregulated power supply. Can I build one power supply to work with entire range? If not, which models are compatible with the supply below?





I am also trying to source an enclosure with a suitable heatsink.

modushop.biz

Would someone be kind enough to check the attached PDF and let me know which model would be suitable?

I will also be driving a pair of Brines FT-1600 Mk2 Speakers

Thanks for your help

[tinitus]

5U seems missing in your attached file
You may be fine with the 160mm 4U, but I would choose the 200mm 5U-300mm
300mm has to my knowledge ONE whole heatsink on each side, the 400mm is split into double heatsinks, and not optimal, unless you build your own boards to suit, or hardwire

btw, someone mentioned that new models are coming, completly aluminium instead the soft steel used now

[westend]

As tinitus stated, the bigger, one-piece, heat sink is a better choice. There is a lot of heat being dissipated.

I built the F5 using these sinks: M&M metals 62430.

The case is an all aluminum DIY affair and I've noticed that the case, itself, is acting as a complimetary heat sink. I am able to hold my hand or forearm on the top of the heat sinks, indefinitely. For reference, the faceplate (pic attached) is 19" x 8".

[Tripmaster]

Originally Posted by tinitus

5U seems missing in your attached file
You may be fine with the 160mm 4U, but I would choose the 200mm 5U-300mm
300mm has to my knowledge ONE whole heatsink on each side, the 400mm is split into double heatsinks, and not optimal, unless you build your own boards to suit, or hardwire

btw, someone mentioned that new models are coming, completly aluminium instead the soft steel used now

Thanks for the info

It will be nice to have a thicker aluminium base plate to tap a thread. At around £200 the cases are not all that cheap, oh well...