Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
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 2nd January 2018, 11:51 PM   #361
Max Headroom is offline Max Headroom  Australia
diyAudio Member
 
Max Headroom's Avatar
 
Join Date: Jan 2013
Location: West Australia, near to the beach, natural ambient sounds mostly.
Quote:
Originally Posted by jameshillj View Post
Well I played around with different components (this same circuit) and each time the components made a substantial difference, some more noticeable than others -

For the first attempt (Verobrd) I used Zfoil Vishays for the input (a bit 'full of myself here!) some Takman and Phillips metal film resistors and the input cap was a Wima mkp10 and the 1n5 and 100nF were some Rifa pfe216 styrene - that 0R33 was a power Caddock met film - diodes were BYW29 (not the smoothest ones!) - power caps were Nichicon GoldTones - the sound was rather bright in my system and also in the AKG k701's but plenty of 'punch' and a but deficient in the bass - too much treble after awhile, annoying.

Number 2 went the other way - carbon resistors (mostly kawame, ABradley, etc) and the 0R33 was a handmade from Manganin resistance wire - input cap was an Audiophiler, the 1n5 & 100nF were Vishay PP, diodes MBR860 and Mundorf power caps - the sound was very 'laid back' in comparison - a bit dull actually - rather surprised.
Change in excess noise level and change in excess noise spectrum...that 0.33R resistor is mission critical as is the excess noise contribution of the carbon resistors.
Excess noise causes masking and modulations/intermodulations, the result can sound 'nice' or decidedly 'not nice' according to the materials involved.
Quote:
Manganin is a trademarked name for an alloy of typically 86% copper, 12% manganese, and 2% nickel. It was first developed by Edward Weston in 1892, improving upon his Constantan (1887). A resistance alloy with moderate resistivity and low temperature coefficent.
Quote:
Constantan is a copper–nickel alloy also known as Eureka, Advance, and Ferry. It usually consists of 55% copper and 45% nickel. Its main feature is its resistivity, which is constant over a wide range of temperatures. Other alloys with similarly low temperature coefficients are known, such as Manganin (Cu86Mn12Ni2).
An interesting experiment would be to swap the current sense Manganin R with Constantan R.

Dan.
  Reply With Quote
Old 3rd January 2018, 12:32 AM   #362
Joe Rasmussen is offline Joe Rasmussen  Australia
diyAudio Member
 
Joe Rasmussen's Avatar
 
Join Date: Jan 2003
Location: Sydney, Australia
Quote:
Originally Posted by Max Headroom View Post
Excess noise causes masking and modulations/intermodulations, the result can sound 'nice' or decidedly 'not nice' according to the materials involved.
Hi Dan, it's been a while. Mine definitely sound good, so I must have done something right?

I think I used three Dales CW-5 1R 6.5W resistors in parallel =0R333, no inductance.

Cheers, Joe.

PS: Sounds way better than whenLM3875 is used conventionally.
__________________
The "Elsinore Project" DIY Speaker System & DIY "Trans-Amp" - 40 Watt Transconductance Amp
- "Don't take anything I say as an affirmation, but as a question." Niels Bohr

Last edited by Joe Rasmussen; 3rd January 2018 at 12:54 AM.
  Reply With Quote
Old 3rd January 2018, 01:06 AM   #363
jameshillj is offline jameshillj  Australia
diyAudio Member
 
Join Date: Feb 2005
Location: Melbourne
The guys of the HK audio club developed a pcb for a 2 channel amp and found it far better than my vero board unit - it is quite dependent on the way it's laid out - Tom Christianson did quite a detailed development around this (see the Neurochrome site)

I have also quite a bit of the wire known as Isotan that is another name for the Constantan - there used to be a lot of the old Isabellenhutte wire on Ebay from Russia and this is a lot 'smoother' than the current production Isotan wire from China

It's quite hard to get the IsabH production power resistors themselves unfortunately but the 1/4W ones from Rhopoint have a similar characteristic - some of these are available from RS and Farnell, but generally silly prices - I got a surprisingly improved detail using that little ldr 'resistor replacer' circuit of Uriah Daley's on the input signal line - a neat little pcb.

I find the Isotan/Constantan to be quite bright and don't use it much and didn't try it in the T40 but have tried it as the source resistors of the F5 amp with similar 'too bright' result - the Nickel certainly brings out the extra top end detail if required

Enjoying the Hoppman cup this week?
  Reply With Quote
Old 3rd January 2018, 01:08 AM   #364
jameshillj is offline jameshillj  Australia
diyAudio Member
 
Join Date: Feb 2005
Location: Melbourne
Afternoon Joe ... James
  Reply With Quote
Old 9th May 2018, 02:13 AM   #365
keantoken is offline keantoken  United States
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
I got Esa's current drive book and have been thinking over things.

For one, what is wrong with physically damping a speaker rather than using the RLC? Why not stuff the enclosure with old socks? Or what about a sub-enclosure with a stuffed port? I'm ignorant, I know.
__________________
The Kmultiplier rail filter! -=- The Simple Kuartlotron Superbuffer!
Need something built, repaired or modded? PM me and ask what I can do!
  Reply With Quote
Old 9th May 2018, 02:54 AM   #366
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
If the old socks are wool or cotton they will work. Stuffed port is a techinique used to make aperiodic enclosures. If you can get the impedance peak at the bottom flat (or complentary to the speakers natural roll-off) a current amp should work well.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 9th May 2018, 02:59 AM   #367
keantoken is offline keantoken  United States
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
Well why don't people just use their old socks instead of buying hundreds of dollars of RLCs?
__________________
The Kmultiplier rail filter! -=- The Simple Kuartlotron Superbuffer!
Need something built, repaired or modded? PM me and ask what I can do!
  Reply With Quote
Old 9th May 2018, 03:38 AM   #368
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
I’ve never used RLCs. They should be considered a last resort.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 9th May 2018, 03:41 AM   #369
keantoken is offline keantoken  United States
diyAudio Member
 
keantoken's Avatar
 
Join Date: Aug 2006
Location: Texas
So a normal woofer could be sufficiently damped with socks to get close to meeting Joe's flat impedance criteria?
__________________
The Kmultiplier rail filter! -=- The Simple Kuartlotron Superbuffer!
Need something built, repaired or modded? PM me and ask what I can do!
  Reply With Quote
Old 9th May 2018, 04:14 AM   #370
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"
Maybe, maybe not. You want to start with something that had low Qms.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote

Reply


Joe Rasmussen "Trans-Amp" - 40 Watt Transconductance "Current Amplifier"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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Building "The Wire AMP" Class A/AB Power Amplifier" wirewiggler Solid State 13 24th January 2015 12:22 PM
"WTB" "The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral enantra Swap Meet 3 23rd December 2012 06:36 PM
That curious extra knob, or: "Trans-Amp" Duo Solid State 111 24th November 2011 11:57 PM
What makes an amplifier "bright", "warm", or "neutral"? JohnS Solid State 51 13th December 2009 06:42 PM
WTB: Focal & Audiom & Volts 11", 12", 13", 15" woofer gengis Swap Meet 0 17th March 2005 02:29 AM


New To Site? Need Help?

All times are GMT. The time now is 09:10 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki