F-5 boards

[stijn001]

Thanks, 6L6! I've gone with 100R.

btw, thanks for your excellent build guide on the F5!

 

[kkerwin]

i have the f5 rev 3.0 clone boards for the f5 amp. the store note that one of the differences between the rev 2.0 and 3.0 is the re-labeling of resistors to match schematics and makes reference to the schematic in the f5 turbo article. additionally, at the beginning of this thread there is a link to the v3 schematic (in the f5 turbo article). is the v3 schematic the one on the second page of the article?
thanks
k

 

[kkerwin]

sorry
my question is already answered in previous posts.
thx
k

 

[slowikpl]

Hello ,

I wil be needed for my Aleph-X upgrade some matched JFET`s.
I need Toshiba 2SJ74BL JFETs 2 x 2 matched pc`s. Does anybody know where to get them ?

Robert

 

[6L6]

fetaudio.com

 

[slowikpl]

And those are no good? 8 pieces of LSJ74 ULTRA LOW NOISE SINGLE P-CHANNEL JFET - Parts

 

[6L6]

They are very good.

However, they are unmatched, so you will need to buy 2-3 packs to ensure getting 2 tightly matched pairs.

 

[slowikpl]

Understood. Thx. I wait for answers from fetaudio.

 

[dutchgfx]

Anyone know what JFETs I can use from mouser?

 

[BobEllis]

Why make do with something Mouser when you can get the right parts from the DIY Audio Store? Parts

 

[dutchgfx]

Because mouser is cheaper and easier, I don't need the highest quality parts I just need functional parts.

 

[BobEllis]

The challenge will be finding a suitable P channel device that matches an N channel you want to use. Filtering Mouser's offerings to Idss >8 mA and through hole mounting limits you to a dual P channel device that may be a compliment to another Interfet dual N channel.

I understand that the store's P channel pricing can be hard to swallow but you're getting a device that works in this circuit and has an N channel compliment. Not to mention that it still a small portion of the cost of a build if you use a decent power supply and build/buy an enclosure worthy of the amp's sound.

Also try member H_A - I think he may have some original Toshibas. Not sure if they will save you money, but you'll get Idss matched sets.

 

[Bigtone]

Fets new stock update!

Hi All,

I have heard it from a good source that DIY Audio has ordered more fets from Linear Systems, when will they be available, as B grade have been on my want list for some time now?

Cheers

Tony

 

[wendelltate]

Will this list of parts work correctly for the v3 boards? I would like to get started stuffing my boards. Thanks

 

[DrG]

I have a tube gain stage (John Broskie's CCDA) which I'd like to mate to a SS output, making a hybrid. The F5 has a little too much gain for this.

Would it be as simple as altering the feedback network resistors to reduce the gain to say, x3? Or are there some hidden consequences?

 

[AndrewT]

decreasing the gain increases the feedback.
That could make compensation mandatory.
As standard the F5 has no added compensation. It works, but with more feedback you may have to add some compensation.

 

[DrG]

Hi Andrew and thank you.

Could you be more specific.
Do you mean HF compensation by means of a cap by-passing the series fb resistor?

Thanks

Sheldon

 

[AndrewT]

No, that can make stability worse. When used correctly it can improve stability, but the range of correct is quite small.

More likely, but it's not an area I am any good at, is added capacitance across gate feed to the output device.
There should be others more qualified that could give better ideas on where to locate comp if it is required to restore the stability margins.

 

[brunogiovs]

Tips on a F5 parts

Hello ALL

I decided to build a F5 , I ordered the pcbs from diyaudio shop.
I got the jfet from ebay . Toshiba 2SJ74GR , 2SK170GR. are those good fit?

any tip on the v3 of f5 in general?

for P1 P2 and P3 could I use cement trimmers? any better fit? 25 turns?

for the TH1 and TH2 is this one a good fit? : http://www.digikey.ca/scripts/DkSearch/dksus.dll?Detail&itemSeq=186603471&uq=635868849650788702

Thanks in advance.

 

[AndrewT]

The 2sk170/j74 GR will require higher value drain load to turn on the output devices.

The Ebay jFETs will need to be measured against the datasheet parameters to prove they are jFETS and to find what Idss and what gm they are.
You may find thay are not jFETs, or are low gm types.