DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 18 Feb 2019, 12:58

All times are UTC - 6 hours [ DST ]

Post new topic Reply to topic  [ 127 posts ]  Go to page Previous  1 ... 9, 10, 11, 12, 13
Author Message
PostPosted: 03 Jun 2014, 23:41 
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1537
Location: US Pacific Northwest
skittle wrote:
Is this operating temperature too high or is this in th normal range.
The real question is, what is the device temperature? Measure the actual temperature of the device or the heat sink DIRECTLY under the device. Then tell us EXACTLY in what package the power devices are housed. Then we can determine the actual junction temperature and we'll see how much headroom you have.

It's all about the Glass!
Cascade Tubes Blog

PostPosted: 04 Jun 2014, 05:53 

Joined: 30 Dec 2010, 00:07
Posts: 4
From the tech data sheet the package is stated as TO-3BPL (TO264) Case 340G-02. Will try and get temperature at device when I get it back together and running again. Trying to fit it to a cabinet and need to rearrange a few connections etc. Should be back up and running in a couple of days.

What sort of maximum temperature would you want at the temperature would you want?

PostPosted: 16 Jun 2014, 12:09 

Joined: 16 Jun 2014, 11:43
Posts: 1
Thank you so much for these very useful explanations and pictures of the P03A. Kind regards Marc

PostPosted: 23 Feb 2015, 16:34 

Joined: 22 Feb 2015, 16:06
Posts: 1
Due to very good reviews of Elliot P3A amplifier, I want to experiment a SMD version of this little piece of art. The only problem is a SMD replacement for BD139 / BD140.
I found a DPAK case transistor MJD44H11G / MJD45H11G ... 4H11-D.PDF

I'm not shure if are suitable for this application and if heat dissipation will be a problem for these devices. Any advice will be helpful.
For the power devices I want to use MAG6333 / MAG9413. They are new, fast, powerful and not too expensive

Kind regards

PostPosted: 08 Jul 2015, 16:48 

Joined: 08 Jul 2015, 04:15
Posts: 1
Hi dtsup1,

Thanks for this awesome review of the amp, you made me ordering the PCBs :-P
I have few questions about this project, some points are differents than on Elliott's project page and I would like to know why.

First of all, PSU : why do you use two rectifier bridges and thus two PSU rails for each side of the amp ? One rail isn't enough ? According to Elliott, one PSU rail can be used for a pair of amps.
Furthermore, the filtering. Way more than announced (4x 22000µF instead of "max" 15000µF total recommended). I know, the more the better, but is it worth it ?

Next question is about preamplification. I plan to use CD player and auxiliary sources like iPod, iPhone, Sonos connect, etc...
Does this amplifier needs a preamplifier in those cases ? If not, can I use a simple 100k stereo pot at the input of the amp for volume control ?
Does the preamplifier have another role than (sometimes) coloring the sound and, you know, preamplifying weak audio signal ?

Please be kind if some questions sounds silly, it is my first SS hifi project !

Thanks in advance,


PostPosted: 23 Feb 2017, 17:32 

Joined: 23 Feb 2017, 02:02
Posts: 306
I went through the first 5 pages of this thread and haven't heard any one talking about fixing the speaker DC voltage to zero volts.

You should achive this by precisly matching your diffrential inputs. ... ching.html I suggest using this method to match your transitors, I had also used this method for mosfets too and it was extremly accurate.

Also to fine tune the voltage to 0mV consider adding a few ohms to the emiter of the diffrential input. No transitors are perfect and you'll always need to do adjustments to set it perfect.
Adding a potential meter 100 or 200 ohms and putting a 50 to 22 ohms in parallel with the pot will allow you to do some fine adjustments.
This may or may not work, its just a guess. I take no repnsiblity if you blow your amp.
This method should work for amps which take both inputs of the diffrential output, but P3A one only takes one output of the diffrential input.

From my exprience speaker dc voltage effects sound quality, amps with large dc voltage have unbalanced power transitor bias.

This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.

PostPosted: 12 May 2017, 13:06 

Joined: 03 Aug 2016, 13:08
Posts: 1
DC on output in my case is 4 and 10 mv. This is not a issue. Rod says that should be lower then 100mv. With unmached pair I get 16 and 20 mv... Also, input transistors needs to be tighten together, and also led diode and transistor next to it needs to be as close as possible. Do not mount driver transistors and bias sens transistor on same heatsink as output devices. Driver and bias transisstors need to be on moderate heatsink together.

Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 127 posts ]  Go to page Previous  1 ... 9, 10, 11, 12, 13

All times are UTC - 6 hours [ DST ]

Who is online

Users browsing this forum: Google [Bot] and 8 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© - Terms of Service - Privacy Policy