PassDIY F5 Amplifier

TomS · « **on:** 1 Feb 2009, 11:37 pm »

After building a pair of F4's I finally finished up my First Watt DIY F5. This amp was constructed with CViller's (from DIYAudio.com group buy) power supply board and amp boards. It is a very simple and inexpensive amp to build from an electrical standpoint with only 2 output Mosfets and no capacitors in the signal path. It biased up easily and is very stable without problems.

zybar · « **Reply #1 on:** 1 Feb 2009, 11:42 pm »

Looks great Tom.

How does it sound?

George

richidoo · « **Reply #2 on:** 1 Feb 2009, 11:46 pm »

Nice job Tom. Big power supply!

TomS · « **Reply #3 on:** 1 Feb 2009, 11:51 pm »

Quote from: zybar on 1 Feb 2009, 11:42 pm

Looks great Tom.

How does it sound?

George

Well, it's warming up on the Merlins downstairs, but there is a room full of kids here for the Super Bowl at the moment...

SET Man · « **Reply #4 on:** 2 Feb 2009, 12:41 am »

Hey!

That's neat.

Could you share with us more info on the schematic, parts used and building process?

Take care,
Buddy

TomS · « **Reply #5 on:** 2 Feb 2009, 01:03 am »

Buddy,

You can find the original Pass article here http://www.firstwatt.com/articles.htm.

I used pretty much the same method as my F4's. I just bought all the metal at Metal Supermarket here and hacked away with drill press, taps, and files. The heatsinks are Conrad MF35-151.5 from Australia, boards are from the group buy on DIYAudio.com, Panasonic TSHA caps, PRP resistors from SonicCraft, 400VA 18-0-18v Antek transformer, and other bits and pieces from Digikey. I used the Fairchild equivalents for IR Mosfets, which are more readily available. No transistor matching is required in this case since there is just a single N and P channel pair.

It's really a fun little project but most of the work is in the chassis work. I've built mine such that any of the Pass FirstWatt amps can go in there. They all run on +/-24v rails at about 300VA, so the power supplies can be interchanged easily.

Tom

Wind Chaser · « **Reply #6 on:** 2 Feb 2009, 02:02 am »

Wow! I'm impressed. You sir, have talent. Unlike Tim Rawson's work, that's a beauty. Wasn't the F series designed to be mated specifically with single drivers?

Very nice. Is it for sale?

TomS · « **Reply #7 on:** 2 Feb 2009, 02:17 am »

Quote from: Wind Chaser on 2 Feb 2009, 02:02 am

Wow! I'm impressed. You sir, have talent. Unlike Tim Rawson's work, that's a beauty. Wasn't the F series designed to be mated specifically with single drivers?

Very nice. Is it for sale?

Thanks, but just don't look at her with the lights turned up

Each of the F series really is a different animal. The F4's are current gain only and probably the most versatile as long as you have a preamp that can swing +/- 20 volts. The F5 is about 15db gain and 25wpc class A, so not really suitable for inefficient speakers. It works just fine on my Merlins and will be just right for the CS2 CD/waveguides with mono F4's on the bass.

Definitely not for sale... I think I have everything I've ever built, just ask my wife

mgalusha · « **Reply #8 on:** 2 Feb 2009, 03:56 am »

Very nice Tom. I'd like to build an F5 at some point but at the rate I get stuff done it will be a long time before that happens.

mike

richidoo · « **Reply #9 on:** 5 Feb 2009, 06:07 pm »

How's the burn-in coming?? How do you like it? (Dumb question) I heard it at RMAF and can't get that sound out of my head. I think I will follow your lead Tom.

Links:
DIYAudio F5 Topic It's a long one....
Official diyaudio F5 PCB

TomS · « **Reply #10 on:** 5 Feb 2009, 08:37 pm »

Quote from: richidoo on 5 Feb 2009, 06:07 pm

How's the burn-in coming?? How do you like it? (Dumb question) I heard it at RMAF and can't get that sound out of my head. I think I will follow your lead Tom.

Links:
DIYAudio F5 Topic It's a long one....
Official diyaudio F5 PCB

Sorry, I've been really busy this week so haven't had any real serious listening time yet. I'm trying to get my modded DCX put back together soon (with new goodies) with the CS2's so I can do the F4 mono's on bass and F5 on HF. So far I probably prefer the F4 on bass and the F5 in mids and highs on the Merlins. It is VERY transparent and pristine, but not harsh at all. It is remotely akin to the XA-J I had for a couple of weeks, which was an insanely smooth and satisfying amplifier to enjoy music. A smidge more syrup added there. Methinks any XA would be killer on the BE-20's. I just can't get that XA.5 lust out of my head either...

blizzard · « **Reply #11 on:** 5 Feb 2009, 08:48 pm »

Hey Tom,
How do you like the Antek transformer? Is there any mechanical buzz of hum? Or, dead quiet?

I have used both Plitrons and Avels and have been pleased. I was thinking about using Anteks on my next build.

Thanks,
Steve

studley · « **Reply #12 on:** 5 Feb 2009, 09:02 pm »

Quote from: TomS on 1 Feb 2009, 11:37 pm

After building a pair of F4's I finally finished up my First Watt DIY F5. This amp was constructed with CViller's (from DIYAudio.com group buy) power supply board and amp boards. It is a very simple and inexpensive amp to build from an electrical standpoint with only 2 output Mosfets and no capacitors in the signal path. It biased up easily and is very stable without problems.

That is spooky; I have a pair of F4s and have just about gathered all the parts to build an F5. How do they compare when used to drive a full range speaker do you think?

TomS · « **Reply #13 on:** 5 Feb 2009, 09:03 pm »

Quote from: blizzard on 5 Feb 2009, 08:48 pm

Hey Tom,
How do you like the Antek transformer? Is there any mechanical buzz of hum? Or, dead quiet?

I have used both Plitrons and Avels and have been pleased. I was thinking about using Anteks on my next build.

Thanks,
Steve

I have two Plitrons in my F4's as well. So far, the Antek is dead quiet both into the dedicated 20a outlets I have and through the RSA Haley. He was great to deal with as I bought several transformers to fill up the same $10 flat rate box. They showed up in 3 days nicely packed.

TomS · « **Reply #14 on:** 5 Feb 2009, 09:04 pm »

Quote from: studley on 5 Feb 2009, 09:02 pm

Quote from: TomS on 1 Feb 2009, 11:37 pm
After building a pair of F4's I finally finished up my First Watt DIY F5. This amp was constructed with CViller's (from DIYAudio.com group buy) power supply board and amp boards. It is a very simple and inexpensive amp to build from an electrical standpoint with only 2 output Mosfets and no capacitors in the signal path. It biased up easily and is very stable without problems.

That is spooky; I have a pair of F4s and have just about gathered all the parts to build an F5. How do they compare when used to drive a full range speaker do you think?

See my comments a couple posts back...

dweekie · « **Reply #15 on:** 5 Feb 2009, 10:00 pm »

I wish I had a fraction of your chassis skills; I'm completely lost when it comes to building them. I find it interesting that you picked just about every single part I planned out in my head for F5 from resistors to caps to transformer. I think I will follow suit once BarredBoss starts selling the big heatsinks. Does that mean your Stratos are getting the boot? I believe Nelson Pass had the F5 on top with the XA30.5 on bottom when he showed off his Lowther OB speakers. I suppose there is something special about the top end of the F5 even in regards to the XA.5 series for NP to choose that combination.

TomS · « **Reply #16 on:** 5 Feb 2009, 10:59 pm »

Quote from: dweekie on 5 Feb 2009, 10:00 pm

I wish I had a fraction of your chassis skills; I'm completely lost when it comes to building them. I find it interesting that you picked just about every single part I planned out in my head for F5 from resistors to caps to transformer. I think I will follow suit once BarredBoss starts selling the big heatsinks. Does that mean your Stratos are getting the boot? I believe Nelson Pass had the F5 on top with the XA30.5 on bottom when he showed off his Lowther OB speakers. I suppose there is something special about the top end of the F5 even in regards to the XA.5 series for NP to choose that combination.

Thank you for that, but seriously, I don't have any metal working skills at all. I guess I should have taken photos of all my pieces before they went together. Since all of them are pre-cut by the supplier, most of the work is just drilling and tapping a few holes. The step drill bit is also a miracle for the unskilled with a sparse tool box/shop (like me).

I've looked at those heat sinks since he is within driving distance to me, but I'm still not sure it's the optimum setup for these amps. The nice thing about the Conrads is they are about 14" deep which makes very nice clean side panels/rails for the overall case. There may be another group buy starting up on those with milled tops/bottoms and tapped holes, so I would jump on that.

The Stratos are great amps, especially for the money, but have been turned off for quite awhile. I still do highly recommend them to many people looking to spend $2-3k and need the muscle they provide.

Yes, Nelson certainly has a unique amp for every taste and application. Knowing how to mix and match those properly can make a terrific system as you heard at RMAF. I sometimes think about begging on the streets to get my own XA30.5, but building your own first class amps on the relative cheap has some real charm. I'm sure if you try the F5 you'll be glad you did!

richidoo · « **Reply #17 on:** 7 Feb 2009, 06:38 am »

Quote from: TomS on 5 Feb 2009, 10:59 pm

I sometimes think about begging on the streets to get my own XA30.5

Hey, if you think that'll work I'm right there with ya!

XAXAXAXAXAXAXAXAXAXAXAXAXAXAXAXAXA

Colin told me the 30 is the best sounding one of all, I guess I don't look much like a XA100 customer...

RAAL owner Aleksander says the F5 is killer on single driver speakers like Feastrex. That's what I wanna try.

TomS · « **Reply #18 on:** 7 Feb 2009, 12:30 pm »

Quote from: richidoo on 7 Feb 2009, 06:38 am

Quote from: TomS on 5 Feb 2009, 10:59 pm
I sometimes think about begging on the streets to get my own XA30.5

Hey, if you think that'll work I'm right there with ya!
XAXAXAXAXAXAXAXAXAXAXAXAXAXAXAXAXA

Colin told me the 30 is the best sounding one of all, I guess I don't look much like a XA100 customer...

RAAL owner Aleksander says the F5 is killer on single driver speakers like Feastrex. That's what I wanna try.

Now that Rick seems to be cranking out new RAAL based designs like rabbits it would be really nice to hear that combination too

richidoo · « **Reply #19 on:** 7 Feb 2009, 05:19 pm »

We live within 5 miles, I hope to hear them "RAAL" soon!