A guide to building the Pass F4 amplifier

[ItsAllInMyHead]

I've built a few tube kits and I just finished two Amp Camps and a B1 Korg. They work and sound great.

<SNIP>

So all that said, other than ordering the F4 and PSU boards, the Deluxe Aluminum 4U chassis, some Keratherm insulators and everything on the BoM, what do I need? I guess I'll need binding posts, IEC and RCA sockets, wire, etc.

I recommend getting the back panel kit if you're already getting the deluxe chassis. The other thing that I'd recommend is building a dim bulb tester if you don't have one.

This thread and the OPs accompanying blog may help.

Aleph J build guide for noobs

It's a different amp, but it could help with sorting out a few odds and ends that you may forget to order that are common to many amp builds. It may also help with some of the PSU choices and the PSU build if needed.

Am I biting off too much?

Not based on the previous builds you listed. Have fun!

 

[william2001]

Oh something else... I highly suggest using two multimeters so that you can watch the bias voltage and DC offset at the same time whenever you are setting up a newly built amp.

 

[Russellc]

?

Avel Lindberg Y236502 160VA 18V+18V Toroidal Transformer

I went with these:

Avel Lindberg Y236651 250VA 18V+18V Toroidal Transformer

Russellc

 

[Alan Cohen]

OK, I'm committed. Thanks for all the tips. I'll work my way thought the Aleph J thread now before I place my PE order.

I placed my BoM order for the F4 including the extra 431s.

This is what I have from the DIY store. Anything else?

Still have to work on the PSU BoM

 

[william2001]

Are those wire wound resistors inductive? If so I would avoid. I would probably use these Panasonic metal films you see in a lot of Pass projects: 667-ERX-3FJR47

 

[Alan Cohen]

The .47R 3W I chose are wire wound. This might be an education opportunity for me.

I've read that metal film resistors <100R are inductive as well. How much so, I don't know. I can't seem to find inductance specs for either.

Since this amp appears to be a current gain amp as opposed to voltage gain, what effect would these resistors have vs a metal film in this application?

UPDATE:

I just found these. Not cheap, considering I need 12, but they are 1% WW non-inductive. Maybe best of both worlds?

https://www.mouser.com/ProductDetail/Vishay-Dale/NS02BR4700FE12?qs=W7Nw27pQsKm5Agv1HbHygA==

 

[william2001]

Probably a non issue. I just follow Nelson's lead on some of this stuff. He uses a bazillion of these Panasonics at that position.

 

[Alan Cohen]

It seems I need a bunch more for the PSU, so add some more for the F4.



Speaking of PSU, any mods I have to make to accommodate the F4?

 

[6L6]

No.

 

[william2001]

Probably wouldn't matter much either way but I would install the wire wounds on the supply board and the ERX Panny's on the F4. I might try the KOA BPR series next time, if I build another amp.

 

[myleftear]

?

Avel Lindberg Y236502 160VA 18V+18V Toroidal Transformer

Being in europe, I got a toroidy, and being cautious not to bungle, 2 x 18 V 500 VA audiograde...

 

[2 picoDumbs]

?

Avel Lindberg Y236502 160VA 18V+18V Toroidal Transformer

You would need 2 x 160VA for a dual mono setup.
Otherwise get a single 300VA or bigger transformer for a standard power supply setup.

 

[2 picoDumbs]

OK, I'm committed. Thanks for all the tips. I'll work my way thought the Aleph J thread now before I place my PE order.

I placed my BoM order for the F4 including the extra 431s.

This is what I have from the DIY store. Anything else?

Still have to work on the PSU BoM

Buy a pico toxic masculinity chassis.
Get on the list.

 

[Alan Cohen]

You would need 2 x 160VA for a dual mono setup.
Otherwise get a single 300VA or bigger transformer for a standard power supply setup.

Antek is about 20 minutes from me and they carry a whole range of Avel Lindberg toroids. What is the value of getting a higher voltage rating? I can get a 18v x 2 500V for $55.

 

[2 picoDumbs]

For good performance get a VA rated transformer around 3x greater than dissipation of amp.
2x is bare minimum

F4 is 2 x 46V (rail to rail) x 1.3 A = 120 W

240VA would be absolute bare minimum.
300VA is generally considered the Firstwatt standard for most of the amps
360VA or greater would be the most optimal.

Going with a bigger transformer will result in:
Better voltage regulation
Radiated heat from the transformer will be minimised

 

[2 picoDumbs]

If you're talking about secondary voltages

20V secondaries would be a little better on this amp - just marginally. You would need to use 35V caps in the power supply though. Most people do this anyway so that shouldn't be a problem for most people.

 

[2 picoDumbs]

If you don't have a chassis yet.
Get this bloody awesome amp chassis

https://www.diyaudio.com/forums/pass-labs/360807-ultimate-4u-500mm-chassis-38.html#post6410433

 

[Alan Cohen]

Got it. That makes perfect sense. I ordered a 500VA 20v secondary toroid. Same $55.

I already ordered the chassis, but the TM sounds neat. Next one...

 

[2 picoDumbs]

Good job.

 

[Alan Cohen]

BTW, this is a very interesting preamp to use with the F4. It is tube rectified with zero feedback and has variable gain up to 20dB. Oh, and it has a phono stage.

https://www.transcendentsound.com/slider.html