F5 Amps - Building a Quartet of Amps in search of the Ultimate F5 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th February 2011, 08:22 AM   #1
NYCOne is offline NYCOne  United States
diyAudio Member
 
Join Date: Jul 2010
Blog Entries: 1
Default F5 Amps - Building a Quartet of Amps in search of the Ultimate F5

I've decided to post all my builds in one place going forward.

A few months ago I came to the conclusion the F5 amp was the most accessible amp for my purposes. As I learned more and more about Class A and Pass Labs, I wanted to try to build my own F5. I'm a scientist by training, and in reading the F5 thread, I became interested in the various permutations of the F5 that seemed obvious. These include the Cascoded F5, the Balanced "X"ed F5, the Standard F5 with multiple outputs.

I was a little surprised at the relatively small amount of information available on some of the designs. While folks were clearly building these amps, only small bits of information have come to the Forum for a few of the efforts. I tried to encourage better flow of information around some of these designs to better understand them myself and have a successful build.

My efforts to date have shown me building these amps is relatively straightforward. They hold only a few surprises, and I have embarked to build as many of them as feasible to try to help myself understand their benefits, and also to help anyone else that asked. I am a neophyte in this domain. Every time I pick up a soldering iron I learn something new. I've had lots of help from other forum members, and could not have gotten this far without J, TB, ZM and NP.

Over the next few weeks, I hope to post side by side impressions of my:
  1. Standard F5
  2. Cascoded F5
  3. Balanced F5 with IRFP outputs
  4. Balanced F5 with Toshiba outputs
  5. Balanced - Cascoded F5 with IRFP and then Toshiba outputs
These are actually four different builds (thus the title of the thread), even though there are more than four permutations of what can be done with these builds.

I'm happy to answer any question I can, to try any experiment I can, and post everything I do, whether it works or not. I've already had a warm welcome via PM with folks who've asked for PCB layouts, advice, etc.

I post as fast as I can - sometimes it will be daily, other times I might go days without a new post.

I'm not an "expert" and I hope to never become one. I'm an average guy interested in technology, trying to get the most out of my DIY audio budget.
  Reply With Quote
Old 17th February 2011, 11:35 AM   #2
diyAudio Member
 
Join Date: May 2001
Location: Bangalore, India
From Juma's very positive comments, his version of the F5 also deserves to be compared, ie., with Toshiba outputs 2SJ313 and 2SK2013.
__________________
Sam
  Reply With Quote
Old 17th February 2011, 12:44 PM   #3
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Quote:
Originally Posted by NYCOne View Post
I've decided to post all my builds in one place going forward.

A few months ago I came to the conclusion the F5 amp was the most accessible amp for my purposes. As I learned more and more about Class A and Pass Labs, I wanted to try to build my own F5. I'm a scientist by training, and in reading the F5 thread, I became interested in the various permutations of the F5 that seemed obvious. These include the Cascoded F5, the Balanced "X"ed F5, the Standard F5 with multiple outputs.

I was a little surprised at the relatively small amount of information available on some of the designs. While folks were clearly building these amps, only small bits of information have come to the Forum for a few of the efforts. I tried to encourage better flow of information around some of these designs to better understand them myself and have a successful build.

My efforts to date have shown me building these amps is relatively straightforward. They hold only a few surprises, and I have embarked to build as many of them as feasible to try to help myself understand their benefits, and also to help anyone else that asked. I am a neophyte in this domain. Every time I pick up a soldering iron I learn something new. I've had lots of help from other forum members, and could not have gotten this far without J, TB, ZM and NP.

Over the next few weeks, I hope to post side by side impressions of my:
  1. Standard F5
  2. Cascoded F5
  3. Balanced F5 with IRFP outputs
  4. Balanced F5 with Toshiba outputs
  5. Balanced - Cascoded F5 with IRFP and then Toshiba outputs
These are actually four different builds (thus the title of the thread), even though there are more than four permutations of what can be done with these builds.

I'm happy to answer any question I can, to try any experiment I can, and post everything I do, whether it works or not. I've already had a warm welcome via PM with folks who've asked for PCB layouts, advice, etc.

I post as fast as I can - sometimes it will be daily, other times I might go days without a new post.

I'm not an "expert" and I hope to never become one. I'm an average guy interested in technology, trying to get the most out of my DIY audio budget.
Your straight forward efforts are greatly appreciated. I am preparing in the next couple of weeks to make an order of 2 pairs of heat sinks from M&M metals, and plan on building at least 2 of your versions.

will all of your builds be utilizing the same size heatsink? I dont know if the usual 12 x 6.5 inches with 2.3 inch fins that I have been using would be adequate for the balanced or multiple output versions?

Also, on your cascoded version, will you be upping the PS rails, or standard 18 + 18 transformer? You are further up the learning curve than I am, but I thought the purpose of the cascode (and please feel free to correct) is less distortion, but also some great advantage with increasing the rail voltage for increased power? I got this notion in an exchange concerning a cascoded, increased rail voltage BA-2, which I want to build, but I am not ready for that. Hopefully by the time I get the next F-5s built I will be ready. A normal BA-2 would be built first.

In the mean time, I want to construct a "Mule" chassis with power supply adequate for several Pass power amp builds, which should facilitate my small efforts.

Thanks for any info,

Russellc

Last edited by Russellc; 17th February 2011 at 12:51 PM.
  Reply With Quote
Old 17th February 2011, 12:53 PM   #4
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Oh, one other thing, I get the idea you are making your own boards? Any info
on our methods would be appreciated, I guess I will finally get around to making my own, somwthing I've looked into for a while.

Again, your efforts are greatly appreciated!

Russellc
  Reply With Quote
Old 17th February 2011, 06:24 PM   #5
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
I have a sneaky suspicion that I will be building another F5 fairly soon... (for a friend) Dual transformers and Toshiba outputs, as well as fancy-pants audiophile resistors and power caps. I am very interested in other bits and pieces as well.

Looking forward to hearing about your observations of the various builds!
  Reply With Quote
Old 17th February 2011, 11:23 PM   #6
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Quote:
Originally Posted by 6L6 View Post
...fancy-pants audiophile resistors...
Just what are those? And where can I get them?
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 18th February 2011, 12:23 AM   #7
Lerg is offline Lerg  Canada
diyAudio Member
 
Join Date: Oct 2010
Fancy-pants resistors have belt codes instead of color codes to indicate their value.
  Reply With Quote
Old 18th February 2011, 03:45 AM   #8
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Fancy-pants resistors are much easier on the senses than common leisure-suit resistors...
  Reply With Quote
Old 18th February 2011, 05:34 AM   #9
expert in tautology
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Ummm... you'd better build a few versions of the base version F5 first!

Looking back at the thread on how changes, including just parts changes, to the base version altered the sound, you'd do well to establish a baseline before delving into other versions as what you find may or may not correlate back to the circuit quite so directly.

Experiments done by a good friend locally, with some help from myself, showed that the F5 is not exactly "one" amplifier with "one" sound. It varies rather quite a lot all over the map depending on things as simple as bias levels, and power supply implementation. Not to mention those pesky parts...

I started a thread last year on just this topic... it's still out there... I think it is...

_-_-bear
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
  Reply With Quote
Old 18th February 2011, 08:02 AM   #10
NYCOne is offline NYCOne  United States
diyAudio Member
 
Join Date: Jul 2010
Blog Entries: 1
First, I want to say thanks to all the folks who've PMed me over the last few months in support of my efforts - I really appreciate the kind words and sympathy for my frustrations. I have to say again, I would have given up had it not been for NP giving me some simple, but key information along the way. He knows more than any one else on the forum, and he's a real gentleman about teaching. A very classy fellow.

Next, apologies for the delay in my response - my day job has gotten quite busy of late.

To answer some questions:

Heatsinks:
All my builds are designed to use the Conrad MF35-151.5. There's not a lot of reason for this except I bought a pair, and want to use them. I drilled each with four holes to accept four output Mosfets for a total of eight on the two heatsinks. In retrospect, if I were starting again, I'd go for something bigger from HeatsinkUSA. I was thinking four 10"x8". Rough cut, it would double my heatsink capacity.

Juma's F5:
I agree, I'd like to include Juma's F5, I considered building it, but I had to draw the line somewhere, and to buy those outputs would be another $50 or $75 (I forget the exact number). If someone has a set and is in the NYC area, please come over and we can try them out. When I narrow down my efforts, perhaps I'll sell something and get a set.

PCBs:
Yes, I etch my own boards and YOU SHOULD TOO! It's so easy, and it lets you try anything and everything. I'd never etched a board in my life until about 2 months ago. I'll only buy a board if it's more than two layers, two layers is my home limit. I use the toner transfer method. I found great Staples paper that makes toner transfer a few minute issue. I buy PCB literally by the pound on eBay. I etch with HCl and H2O2. My all in cost per board is ~$2-3. I go from idea, to layout, to transfer, to etch and drill in about 2-3 hours total.

Transformers:
I'm going to be buying new transformers. Right now I only have 2x18V and 2x26V. I haven't come to a final decision, but I'm leaning toward 2x12V or 15V for the Balanced Circuit, and 2x24 or 26V (if I do 26V I'll need a larger VA rating than I have with my current tester toroid).

"Fancy pants" resistors:
I bought the Futaba MPC74 resistors. They are nearly impossible to get in the US at any reasonable price. In the EU, they're sold in Germany by a retailer. Do not buy from eBay, I believe the seller is selling counterfeits. Why these resistors? They're 5W, non-inductive, accurate metal plate resistors in the right, weird values needed for the Balanced F5. I bought a LOAD of them. I have more sets than I can use, if you want a set for your build, let me know. I also have hundreds of 2SK170BL and 2SJ74BL matched.

Evaluation of the F5s:
Finally, I'm pushing the build of my Martin King OB speakers - FF85K over Alpha 15s. I fired up the router (first time ever using one) tonight, and made a circle jig. I hope to do the cut outs over the weekend. Once I have these, I should be able to really test the amps.

On another note, I've said it before, I live right in the middle of Manhattan, if you're coming to NYC for work of fun, please feel free to stop in and see the efforts first hand.

Please don't forget my call to arms: Build! You can't go wrong - these are wonderful amps with forgiving designs. Build!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pass F4, F5 and Motif amps joda Swap Meet 2 24th December 2010 11:16 AM
Need parts for [2] f5 amps and power supply elecres Swap Meet 2 6th September 2010 09:59 PM
Mix of GB and F5 Amps idea fab Solid State 43 20th October 2008 11:30 PM


New To Site? Need Help?

All times are GMT. The time now is 03:27 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2