Hi, Stephan
Thermal stability is not an issue with this amp. It runs rather cool, being a (almost) class B design. But even when I had the output biased to 100mA, the drivers hardly got warm. Even driven hard, the drivers hardly manage a blush. It's a brilliantly simple and effective configuration: the fact that the devices that undergo the largest changes in temperature (o/p transistors) are not critical to output stage stability.
So much for thermal stability of the output stage...
This amp is not dc coupled, though, and the dc gain is unity, so that dc drift is not an issue here. However, in my PCB layout, I did provide for the possibility of dc coupling. The differential pair and current mirrors are placed close to each other, face-to-face, respectively. So, after gain-matching them, they may be mechanically/thermally coupled. This should prevent any possiblilty of thermal drift.
As for the next meeting venue, I'll only get to see the contact person this evening.
I'll email you the schematic.
Thermal stability is not an issue with this amp. It runs rather cool, being a (almost) class B design. But even when I had the output biased to 100mA, the drivers hardly got warm. Even driven hard, the drivers hardly manage a blush. It's a brilliantly simple and effective configuration: the fact that the devices that undergo the largest changes in temperature (o/p transistors) are not critical to output stage stability.
So much for thermal stability of the output stage...
This amp is not dc coupled, though, and the dc gain is unity, so that dc drift is not an issue here. However, in my PCB layout, I did provide for the possibility of dc coupling. The differential pair and current mirrors are placed close to each other, face-to-face, respectively. So, after gain-matching them, they may be mechanically/thermally coupled. This should prevent any possiblilty of thermal drift.
As for the next meeting venue, I'll only get to see the contact person this evening.
I'll email you the schematic.
Local Component Suppliers & Knowledge Base
Stuart,
Thanks for the info. I'll contact them this week to check prices.
I think the online idea is good. I have some webspace that I've never really used over the last few years. However, it would need to be static for now.
I'll put a basic one together and post the link when its ready.
I want to include the following:
-Heatsinks,
-Pots (stereo conductive plastic eg Bourns, Vishay etc)
-Lateral Mosfets eg 2SK1058/2SJ169
-Complementary Power Transistors eg 2SC3281/2SA1302, MJ15003/MJ15004
-Chokes (used to be an RF engineer working in Highveld Techno Park - can't remember the company - that would wind this )
-dials (access to milling machine eg engineering companies)
-Faceplates (eg http://brian.darg.net) - aluminium
etc
Anyone with info on suppliers for the above (including approx pricing) and anything else you want to include, please post it or email.
Stuart,
Thanks for the info. I'll contact them this week to check prices.
I think the online idea is good. I have some webspace that I've never really used over the last few years. However, it would need to be static for now.
I'll put a basic one together and post the link when its ready.
I want to include the following:
-Heatsinks,
-Pots (stereo conductive plastic eg Bourns, Vishay etc)
-Lateral Mosfets eg 2SK1058/2SJ169
-Complementary Power Transistors eg 2SC3281/2SA1302, MJ15003/MJ15004
-Chokes (used to be an RF engineer working in Highveld Techno Park - can't remember the company - that would wind this )
-dials (access to milling machine eg engineering companies)
-Faceplates (eg http://brian.darg.net) - aluminium
etc
Anyone with info on suppliers for the above (including approx pricing) and anything else you want to include, please post it or email.
OK, found the prices of some transformers from W. Gardner & Son:
400VA: R310.50
225VA: R240.50
Plus (optional)-
Vacuum impregnation: R15/R10 resp
Dipping: R20/R20 resp
Heatsinks
Mantech have a nice 200mm heatsink, which can be ordered to your length. It is not anodised.
Transistors
Beware counterfeit transistors. I'd rather buy from ON Semi directly, but MOQ is 25 pieces.
Communica should be able to supply chokes and mains filters
400VA: R310.50
225VA: R240.50
Plus (optional)-
Vacuum impregnation: R15/R10 resp
Dipping: R20/R20 resp
Heatsinks
Mantech have a nice 200mm heatsink, which can be ordered to your length. It is not anodised.
Transistors
Beware counterfeit transistors. I'd rather buy from ON Semi directly, but MOQ is 25 pieces.
Communica should be able to supply chokes and mains filters
Wow, at last a few more South Africans.
My interest mainly high power amps, (son's a DJ) Presntly building a TO3 version of the ESP P68 300 watt amp.
I bought TO3 MJ15022/3 from Candy Electronic in Durban, about R 14.00 each, however the first lot tried blew when tested on my revised amp, now Ive gotta figure out if I messed up or if they are fakes. Weird actually, the amp worked fine with only two outputs full voltage, I then fitted the new trannied on a big heatsink, three per side, amp worked but on testing at high volume blew, and took the drivers with. I think I should opne the trannies and have a look inside before I carry on.
We build our own speaker boxes, and scrounge old rack mountable amp boxes from local music shops, but it all looks rather tatty and a database of good South African suppliers would be very handy. I will start getting all my previous suppliers detaisl together and will mail to whever wants them.
Proudly South African
My interest mainly high power amps, (son's a DJ) Presntly building a TO3 version of the ESP P68 300 watt amp.
I bought TO3 MJ15022/3 from Candy Electronic in Durban, about R 14.00 each, however the first lot tried blew when tested on my revised amp, now Ive gotta figure out if I messed up or if they are fakes. Weird actually, the amp worked fine with only two outputs full voltage, I then fitted the new trannied on a big heatsink, three per side, amp worked but on testing at high volume blew, and took the drivers with. I think I should opne the trannies and have a look inside before I carry on.
We build our own speaker boxes, and scrounge old rack mountable amp boxes from local music shops, but it all looks rather tatty and a database of good South African suppliers would be very handy. I will start getting all my previous suppliers detaisl together and will mail to whever wants them.
Proudly South African
Yeh, seen that,
Funny story, I first built 2 P68s using 2SC3281 and 2SA1302's salvaged from a dead Sammick amp, worked well so I decided to build two more. I ordered parts from Protech in Durban, was quoted about R 20 per pair, so I bought 8 pair. (They dont stock anymore!!)
After a while, and after reading that article I was convinced they must be fake. I built the amps anyway and my son now uses that one more than the other cause it runs cooler. Had absoluely no hassles, so they must have been genuine despite the price.
Anyone know where I can get equivalent TO3P "flatpacks" to the above in RSA, I have converted the P68 to take metal trannies but Rods design and board are really good and I would prefer to build them as designed.
DieterD
Funny story, I first built 2 P68s using 2SC3281 and 2SA1302's salvaged from a dead Sammick amp, worked well so I decided to build two more. I ordered parts from Protech in Durban, was quoted about R 20 per pair, so I bought 8 pair. (They dont stock anymore!!)
After a while, and after reading that article I was convinced they must be fake. I built the amps anyway and my son now uses that one more than the other cause it runs cooler. Had absoluely no hassles, so they must have been genuine despite the price.
Anyone know where I can get equivalent TO3P "flatpacks" to the above in RSA, I have converted the P68 to take metal trannies but Rods design and board are really good and I would prefer to build them as designed.
DieterD
Free Samples
Thats cool, but at the rate my sons need amps that will last me two weeks.
I have just discovered I have been supplied fake MJ15022/3's from Candy Electronics in Durban, do any of the South Africans out there know where I can get "proper" ones in RSA, I need about 30 odd to build a new mobile DJ rig.
Any ideas?
DieterD
Thats cool, but at the rate my sons need amps that will last me two weeks.
I have just discovered I have been supplied fake MJ15022/3's from Candy Electronics in Durban, do any of the South Africans out there know where I can get "proper" ones in RSA, I need about 30 odd to build a new mobile DJ rig.
Any ideas?
DieterD
DieterD, your best bet is buying them from OnSemi. I bought some stuff from them and it arrived within the week by courier. This way you are guaranteed to get real parts and you don't pay the retailer's rent. They only sell in sets of 10 or 15, but it doesn't sound like that will trouble you.
Hello from sunny South Africa- feedback
Hi
The Cape Town Hifi Club is in the process of being revived.
At this stage there are not many members so it would be nice if more people could join. The club is an excellent venue where people's interest in audio can be nutured into a serious interest in High-end audio.
A secondary benefit is members start to network with a lot of fellow audiophiles who can assist each other.
So if anybody is interested in joining, please contact me or Shaun.
Jozua
Hi
The Cape Town Hifi Club is in the process of being revived.
At this stage there are not many members so it would be nice if more people could join. The club is an excellent venue where people's interest in audio can be nutured into a serious interest in High-end audio.
A secondary benefit is members start to network with a lot of fellow audiophiles who can assist each other.
So if anybody is interested in joining, please contact me or Shaun.
Jozua
Amplifier enclosures
I'll be looking into the viability of getting some amp chassis custom made locally. Basically, a knockdown kit that would suit a wide variety of applications. Ideally, this would be a 420mm-wide box.
I'd imagine that there'ed be two sizes: one for preamp, and one for power amp applications.
Now I need to know what you guys think about:
a) what it should cost (be reasonable)
b) what the sizes should be
c) what features it should have (plain would be cheapest)
Basically, I want to compile a spec.
It might fly -or not. Let's give it a go.
I'll be looking into the viability of getting some amp chassis custom made locally. Basically, a knockdown kit that would suit a wide variety of applications. Ideally, this would be a 420mm-wide box.
I'd imagine that there'ed be two sizes: one for preamp, and one for power amp applications.
Now I need to know what you guys think about:
a) what it should cost (be reasonable)
b) what the sizes should be
c) what features it should have (plain would be cheapest)
Basically, I want to compile a spec.
It might fly -or not. Let's give it a go.
Feedback on Part Prices in Gauteng
Some feedback wrt part pricing:
Prices are ex-Vat
1) Mantech:
Pre-Driver Transistors
2SB649 - R11.18 (for equiv - NTE374)
2SD669 - R5.55
TIP31C - R2.52
TIP32C - R3.06
Drivers
2SC3281 - R45
2SA1302 - no stock (MOQ in effect)
2SK1058 - R45 (hard to find - limited stock)
2SJ162 - R45 (hard to find - limited stock)
2) Avnett Kopp
Drivers
MJ15003 - R17 (limited stock)
MJ15004 - R17 (limited stock)
Avnett had a few specials eg relays @ R1.10 but not much else.
They don't carry the popular 2SK1058/2SJ162 pair.
I was looking for Texas Instruments (Burr Brown) digital potentiometers but they don't carry the latest.
Get hold of their CD catalogues. Makes shopping a lot easier!
I have a reasonable stock now to move forward on the preamp and power amp - expensive shopping trips!
I like Shauns idea on a spec and getting a flatpack made. I'm busy trying to get this detailed on Autocad. I agree on the width. What I would like to suggest is a mounting arrangment that allows you the freedom to mount whatever faceplate you want.
Cost is going to be difficult. I would be happy to pay R350 for an amplifier case and R250-R300 for the preamplifier case.
If we could get someone to machine knobs for us, even better!
Some feedback wrt part pricing:
Prices are ex-Vat
1) Mantech:
Pre-Driver Transistors
2SB649 - R11.18 (for equiv - NTE374)
2SD669 - R5.55
TIP31C - R2.52
TIP32C - R3.06
Drivers
2SC3281 - R45
2SA1302 - no stock (MOQ in effect)
2SK1058 - R45 (hard to find - limited stock)
2SJ162 - R45 (hard to find - limited stock)
2) Avnett Kopp
Drivers
MJ15003 - R17 (limited stock)
MJ15004 - R17 (limited stock)
Avnett had a few specials eg relays @ R1.10 but not much else.
They don't carry the popular 2SK1058/2SJ162 pair.
I was looking for Texas Instruments (Burr Brown) digital potentiometers but they don't carry the latest.
Get hold of their CD catalogues. Makes shopping a lot easier!
I have a reasonable stock now to move forward on the preamp and power amp - expensive shopping trips!
I like Shauns idea on a spec and getting a flatpack made. I'm busy trying to get this detailed on Autocad. I agree on the width. What I would like to suggest is a mounting arrangment that allows you the freedom to mount whatever faceplate you want.
Cost is going to be difficult. I would be happy to pay R350 for an amplifier case and R250-R300 for the preamplifier case.
If we could get someone to machine knobs for us, even better!
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