Smaller Leach Amp V1 - Page 154 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 7th March 2010, 01:40 AM   #1531
Luke is offline Luke  New Zealand
diyAudio Member
 
Join Date: Sep 2001
Location: Wellington NZ
Send a message via AIM to Luke
Quote:
Originally Posted by Loboone View Post
Hi Luke,

Hopefully it will live up to my expectations and by all accounts it should be a good one. (I will have to build some new speakers to go with it though).

The regulator is the one from Jens and Bob Ellis. It is intended as a +/- 15volt supply but with some alterations will go to 75 volts.

I am trying to upload the schematic but the file is too big so I am having dificulties.

The heat sinks were not that exspensive if I remember correctly. But I will add that as someone commented on the new thread these are not cheap amps to build. (Especially in NZ) I would have spent up to 1k on this one (mostly freight I mite add). And this has probably added to the length of time it has taken also.

But it is a hobby remember!!!!! (I keep telling myself)

Ian
Im finding that anything complex in design is not cheap and higher power levels need more outputs bigger transformers etc.
So is this using mosfets on the output, Ive never heard of this configuration on a leach.
__________________
If you give a man a fish he will eat for a day. But if you teach a man to fish he will buy an ugly hat. And if you talk about fish to a starving man then you are a consultant. Dilbert
  Reply With Quote
Old 7th March 2010, 01:42 AM   #1532
Luke is offline Luke  New Zealand
diyAudio Member
 
Join Date: Sep 2001
Location: Wellington NZ
Send a message via AIM to Luke
Quote:
Originally Posted by Byrd View Post
Fantastic Loboone.

Yes - Hobby or obsession

Would be interesting to have someone do a writeup of their subjective opinion of the difference between regulated and non regulated frontend.

Mine sound good as is - but maybe ...
yes and power stage as well would be nice to hear about.
__________________
If you give a man a fish he will eat for a day. But if you teach a man to fish he will buy an ugly hat. And if you talk about fish to a starving man then you are a consultant. Dilbert
  Reply With Quote
Old 7th March 2010, 08:10 AM   #1533
Loboone is offline Loboone  New Zealand
diyAudio Member
 
Join Date: May 2005
Location: Hamilton Waikato NZ
Hi all,

Sorry for the confusion but the mosfets etc to the left of the Leach are for my other (some may say dark side) of my hobby. Parts and boards for ZEN9 amp and symetrical supply B1 pre-amp.

I was just trying to show off the fact that I have some Power J-Fet LU1014
as I believe they are somewhat hard to come by!!

So if you all are thinking that I am even close to the level of expertise that you good people are you are sadly mistaken. I am I true believer in if it aint broken (or works perfectly well) why try and re invent the wheel. So the Leach will be as per plans accept for the regulated front end.

Thankyou all for the nice comments though. I would be more happy to answer any questions with regards to the amp etc.

I'll keep you all updated.

Ian
  Reply With Quote
Old 16th April 2010, 03:13 AM   #1534
...truth seeker...
diyAudio Member
 
Ed LaFontaine's Avatar
 
Join Date: Feb 2004
Location: where the Appalachians rise from the Blue Grass
bump for the current Leach clone build
  Reply With Quote
Old 28th March 2011, 02:36 AM   #1535
cfbuck is offline cfbuck  Canada
diyAudio Member
 
Join Date: Mar 2004
Location: London, Ontario
I am just getting around to the Small Leach build from 5 years ago and need some advice to proceed further. The pcb is stuffed except for the output transistors. Bob Ellis and AndrewT have helped with building a regulated power supply. Now the project is to the point of connecting the pieces together for testing, but before that occurs, some advice is needed for the enclosure. I am a woodworker so I was leaning towards a wood enclosure.

The heatsinks were obtained from ApexJr a few years ago--a pair of sinks 2.3 x 4.6 x 12.5 inches which can form a tunnel 4.6 x 4.6 as shown in the photos below. The mounting plane of the sink is 4.5mm or .175 inches thick. I have no idea of the exact cooling capacity of the sinks or even if an estimate of their cooling capacity is possible.

The enclosure, if built with the tunnel, would be too high at 12.5 inches. Would anyone hazard an opinion if the sinks would be adequate to cool the unit if they were to be cut down to about 8.5 inches. The tunnel would be oriented vertically. A muffin fan is available in the tunnel size if 12 VDC can be obtained to feed it to help augment the heatsink cooling. But whether a fan is advisable or not is another question.

The output transistors positionally mount on top of the heavier and deeper fins of the sink. If you see any obvious problems with the pcb feel free to comment as well.
Attached Images
File Type: jpg 3HS640.jpg (85.7 KB, 321 views)
File Type: jpg pcbonHSsm.jpg (101.1 KB, 331 views)
File Type: jpg TunnelHSsm.jpg (71.9 KB, 314 views)
__________________
Signature
  Reply With Quote
Old 28th March 2011, 03:29 AM   #1536
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
Another project for you - find a temperature sensitive fan controller circuit. Rod elliot has one and there are a few here, including a two speed controller. Mount the sinks horizontally and have a fan kick on only if they get too warm. Burying the fan inside a wooden case will help keep it quieter, although it probably would be slightly more efficient sucking air through the sinks.

I have four channels of Leach amp (V4.5 on Leach boards) on those sinks mounted horizontally running at ~100 mA bias each for 45W. The amp gets warm but not hot in normal use. Although I haven't really driven it hard I hadn't connected without a fan until recently. I'm using a 10W 120VAC fan - I don't remember its flow rating, but I cranked the bias up to 750 mA/channel (~330W) and the output end of the sink gets to about 50C (after an hour I can put my fingers on it for more than 10 seconds, but it is hot). The amp is doing double duty, making music and giving my bhut jalokia and other hot pepper seedlings nice warm days in my indoor hot house. Another month or so I'll turn the bias back down when it warms up enough to move the plants outside.
  Reply With Quote
Old 28th March 2011, 07:38 AM   #1537
diyAudio Member
 
Join Date: Nov 2004
Location: manila,PH
The challenge would be to balance the size of heatsink with optimal bias vs temperature. With the thermal compensation diode feeding a fan controller circuit from ESP site that could make this automatic is definitely worth the look. This would be used to control fan speed.
__________________
Pinoy ikaw ay pinoy... ipakita sa mundo... kung ano ang kaya mo...
  Reply With Quote
Old 28th March 2011, 09:43 AM   #1538
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Vertical sink tunnels are best. They need the least power assistance to achieve a certain cooling ability.
Blowing the sink is more efficient than sucking.
Blowing also exposes the fan motor to cooler temperature.
An early Pass had blown vertical sinks. Was it the *40?

Three temp switches on the sink would be great. all off = fan off.
first on = slow fan. Second on = fast(er) fan. Third = power down.
or use a variable as Bob suggests, but still fit a power down switch, or at least a loud/bright alarm.

BTW,
the emitter resistor value and the PSU voltage determine the amplifier Pq.
Watch for blowing fuses with those on board capacitors. 4700uF and +-58Vdc needs a long current duration to charge up.
There is space for 15mF, but that is virtually un-fuse-able.
__________________
regards Andrew T.

Last edited by AndrewT; 28th March 2011 at 09:47 AM.
  Reply With Quote
Old 28th March 2011, 11:42 AM   #1539
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
That Pass amp was the A75.

I was thinking a multi speed fan, too. Seems easier to design/build a controller to me. Good idea for a cool down after shut down.

The Hafler DH500 uses an AC fan and a couple of 300R/7W resistors in series. As temperature rises thermal switches sequentially close, increasing the fan speed. With 600R in series, the fan is virtually silent. You could add a lower temperature switch to shut off the fan completely at lower temperatures. Not the most efficient way to reduce the speed of an induction motor, but it does the job.
  Reply With Quote
Old 28th March 2011, 07:29 PM   #1540
cfbuck is offline cfbuck  Canada
diyAudio Member
 
Join Date: Mar 2004
Location: London, Ontario
Thanks for all the help guys. I have my homework. I'll have a look at the ESP solution. The consensus as I see it, do not cut the heatsinks shorter.
The heatsink tunnel is more efficient vertically but fan-driven horizontal orientation is just fine especiallyif Bob can run 4 channels off these sinks instead of the 2 that I`m using. I don`t have a greenhouse to heat either.

Andrew, the emitter resistors are 0.47., the transformer is 39.8-0-39.8 so it should be about 56V at the PSU.
__________________
Signature
  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



New To Site? Need Help?

All times are GMT. The time now is 11:58 AM.


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