The diyAudio Firstwatt F6

[cygnus x1]

I ended up purchasing the CineMag with leads, so I can fit any board layout. Makes it easy for me to mount and proceed with P2P. Another question, I have a bunch of IFRP250 left over from a repair, is it OK to try to use them? Getting ready to order from Mouser, so if not the IRFP240 are cheap. Do they need to be matched or just close?

 

[Zen Mod]

250 are good

try close , if not ...... coin is yours at both sides ..... it'll work ;

try to make PC based THD setup and you'll know are they adequately oriented (which one is having slightly more xconductance )

 

[Marra]

I have been listening to this amp for the last couple of weeks and am very much enjoying its sound. The bias and offset settings have been checked and reset twice as they had drifted somewhat. The amp being very sensitive to trimmer adjustment in particular the offset and to whether the lid is on or off.
Sound quality is superb and the F6 has the deepest/widest soundstage of any amp that I have built in the last thirty years; the majority of which have been Nelson's designs. A big thank you Papa

 

[Dennis Hui]

Marra, thanks for the update. Very exciting.

Cheers,
Dennis

 

[vdi_nenna]

Thanks Marra.

 

[jugi63]

Has anyone compared the sound of separate diodes to the diode bridges most commonly used with the First Watts?

Nelson seems to use diodes in his Pass Lab amps. You'd think they are superior? If one wanted to try out, which ones to use? Which one's does Nelson use - you guys know?

 

[6L6]

For power amps, I prefer the $3 bridges to discrete diodes. More natural sounding.

Line level projects I use fast diodes.

 

[biju55]

For power amps, I prefer the $3 bridges to discrete diodes. More natural sounding.

Line level projects I use fast diodes.

Fast diodes are less natural sounding in power amplifier ?.

 

[buzzforb]

Any way you looks at it, it's a very small part of the sound. It may change it for the better, but the topology and active components determine the sound. Don't tweak until you are sure you like the sound of the general amp. Then you can chase the rabbit and get into the ge of diminishing returns.

 

[Zen Mod]

fast diodes ........ only with killer Donut and decent (if not also overkill) big cap bank

if going economically , fast diodes will reveal budget tightness

edit : so , conclusion - cherry on top , strictly

 

[PKI]

I wonder why nobody(?) tried schottky...

 

[Zen Mod]

sorry - I referred exactly to Schottky

 

[jugi63]

Any way you looks at it, it's a very small part of the sound. It may change it for the better, but the topology and active components determine the sound. Don't tweak until you are sure you like the sound of the general amp. Then you can chase the rabbit and get into the ge of diminishing retur

.

Yups, this is exacly what I've been doing. The F6 has been my default amp for quite a while now. Also my system is really quite good - so every, even small, change does make a difference. It's already been diminishing returns for some time now...

So am I to understand Schottky is the part to try? Would you give some exact part reference/number, please?

 

[Zen Mod]

100V/20A part

choose

 

[labjr]

I have these fast recovery bridges in my parts collection. You have to be extra careful with inrush current. They blow up easier than standard bridges. And they cost a lot more.

http://www.partsconnexion.com/PDF/l363.pdf

 

[jugi63]

100V/20A part
choose

Well... there are at least a dozen different versions even with these specs... The whole point of me asking was not having to choose blindly - hoping there is some consensus or at least someone’s experience of which one(s) sound the 'best'. Obviously, after building a couple of First Watts, I trust Nelson's ears, so that's why I asked what he prefers.

labjr, the IXYS is a bridge again. Would you have any comment on the sound compared to a standard bridge?

 

[6L6]

I use these.

GBPC3502 Fairchild Semiconductor | Mouser

In my experience, there is no sound difference in diodes in this kind of PSU. I strongly prefer the bridges like this as they are smaller, cooler, much less expensive, and easier to mount.

High-speed diodes are made for a completely different purpose than a huge linear PSU.

And anyway, if there is a 'sound' to the PSU, it's going to be completely dominated by the second row of filter capacitors.

 

[marconi118]

are IRFP150 good for F6?

 

[Zen Mod]

look at them as on two IRFP240 in parallel

so - more capacitance

though - try ..... maybe you'll like it

 

[jugi63]

OK - thanks 6L6 and Zen Mod!
We'll if I get to trying out the difference one of these days...