It looks like my krell clone is going to be monblocks using Aleph 2 chassis (Ha!). So, for those that have peeked inside an Aleph, exactlty how are the sinks coupled together to form the chassis? From the external pictures I have, it looks like there is a central pillar on each side that holds together the sinks to form each side. I gather there are also four pillar in the corners that link the sides? Also, since each case is capable of plenty of dissipation, I am wondering how best to use that feature to the best advantage. More bias, more output devices, 30-30 (insead of 25-25) trafo? Any suggestions? This project is going to be a lot of fun. 
I find it hard to believe that your 50 is not tight and clean.... mone certainly is and it continues to amaze everyone that stops by for a listen!! What speakers are you using Jozua? I am going to hook up 2-500VA 30-0-30 volt toroids tonight and we'll see how they work. I've been runnning mine from 2-680 VA toroids cranked down from a 20 amp variac so that I have 40 volt rails.... this is about the maximim rail voltage you'd want to go to without doing at least some changes to the zener resistors. I will report back later on tonight or tommrrow as these toriods are readily available on E-Bay and inexpensive.
Mark
Hi Mark,
my memory defeats me again, remind me, is the 500VA per channel or 2 off 500VA in a mono block set up?
A 20A variac, wow some machine!
Zener resistor is specified as 1k5, using a 500mW Zener then the resistor is suitable for a wide range of Vrail. Resistor dissipation shown in table below and assuming a minimum current in the Zener of 10% of maximum.
36v 54mW
38V 81mW
40V 113mW
42V 150mW (250mW resistor getting hot)
46V 241mW (250mW resistor now at limit & resistance out of spec)
50V 353mW (600mW resistor getting pretty hot)
55V 523mW (probably needs a 1W resistor)
Hope this helps and/or allays fears.
my memory defeats me again, remind me, is the 500VA per channel or 2 off 500VA in a mono block set up?
A 20A variac, wow some machine!
Zener resistor is specified as 1k5, using a 500mW Zener then the resistor is suitable for a wide range of Vrail. Resistor dissipation shown in table below and assuming a minimum current in the Zener of 10% of maximum.
36v 54mW
38V 81mW
40V 113mW
42V 150mW (250mW resistor getting hot)
46V 241mW (250mW resistor now at limit & resistance out of spec)
50V 353mW (600mW resistor getting pretty hot)
55V 523mW (probably needs a 1W resistor)
Hope this helps and/or allays fears.
niles said:Also, since each case is capable of plenty of dissipation, I am wondering how best to use that feature to the best advantage. More bias, more output devices, 30-30 (insead of 25-25) trafo? Any suggestions? This project is going to be a lot of fun.
Depends on the speakers: if they're a difficult (low impedance) load it's worth increasing the bias, otherwise increasing the voltage will give more headroom.
http://www.tcaas.btinternet.co.uk/jlhupdate.htm
Aleph 2 heatsinks handle 300 watts.
If you intend to take full benefit of such large heatsinks you will have to increase the number of output devices.
Quicky wet thumb :
number of output devices = 2 * Rjc/Rsink
For my setup i only need 20 volts continuous, which is already enough to increase my headaches.
Above that will trigger the protection of my loudspeakers.
As their minimum impedance is kind of low, i favor a high bias.
On the Pass front there is agreement that the bias level has an effect on sound, higher bias improves the sound quality.
Now that is single-ended stuff, of which output level is directly limited by the level of bias.
I am curious if it has an effect on pushpull outputs.
Besides, plenty of higher power class A amplifiers been done.
Only a handfull of very high bias pushpull versions.
You certainly do have the engineer spirit, Niles.
Upupa Epops said:Instead neverending thinking about biasig and overbiasing, try to ask Bruce Candy, how to make good amp, Jacco....
wow, I just googled Bruce Candy and found a review of his Halcro something-or-other - $25000 and it doesn't even heat the greenhouse!
Puts the cost of the Klone heatsinks into perspective...
Bass Speed of clone
Hi
Guys, please accept my apologies for responding so late. Many thanks for your input.
K-amps and Pinkmouse - I am toying with the idea of using smaller caps but the idea of keeping as close to the orginal was the only motivating factor in buying the large caps. I have tried adding by-pass caps (Sonicaps & polarised Hovlands) but on the long term I did not like the effect they had and removed them. If I buy the 100 volt Mallories they can possibly be used as spares for my aging KSA100 so it would not be a complete waste. The question I still have which is the better caps Mallories or Vishay ?
Andrew- As a long term Krell owner I am reasonably certain that the KSA100 design is fine. In fact despite it age it is still capable of putting many modern amps to shame. The mere fact that is still working after 20 years says something re it build quality. Despite what some members might say size and overkill design obviously has advantages.
Mark: I am using various Newform Research Ribbon Loudspeakers which are a easy load (plus/minus 5 ohm) to drive.
I might just add that each channel has a 25-0-25 transformer with a 500 VA rating.
I always assumed that the clone would have the same phase as the KSA100. By mere fluke I reversed the speakers polarity last night only to discover that the amps sounds better. This might be something to take note of.
Despite my concerns I am already beginning to work on collecting parts for a second clone using the Pinkmouse boards. I want to bi-amp with identical amps.
Regards
Jozua
Hi
Guys, please accept my apologies for responding so late. Many thanks for your input.
K-amps and Pinkmouse - I am toying with the idea of using smaller caps but the idea of keeping as close to the orginal was the only motivating factor in buying the large caps. I have tried adding by-pass caps (Sonicaps & polarised Hovlands) but on the long term I did not like the effect they had and removed them. If I buy the 100 volt Mallories they can possibly be used as spares for my aging KSA100 so it would not be a complete waste. The question I still have which is the better caps Mallories or Vishay ?
Andrew- As a long term Krell owner I am reasonably certain that the KSA100 design is fine. In fact despite it age it is still capable of putting many modern amps to shame. The mere fact that is still working after 20 years says something re it build quality. Despite what some members might say size and overkill design obviously has advantages.
Mark: I am using various Newform Research Ribbon Loudspeakers which are a easy load (plus/minus 5 ohm) to drive.
I might just add that each channel has a 25-0-25 transformer with a 500 VA rating.
I always assumed that the clone would have the same phase as the KSA100. By mere fluke I reversed the speakers polarity last night only to discover that the amps sounds better. This might be something to take note of.
Despite my concerns I am already beginning to work on collecting parts for a second clone using the Pinkmouse boards. I want to bi-amp with identical amps.
Regards
Jozua
From John Atkinson's October 2004 Review:
An interesting claim - Has anybody heard of another amp using vertical fets? Atkinson really knows electronics. 
The Halcro patent references the Pass Stasis patent, but I was unable to view the images on the USPTO site.
Now, with all due respect to those who prefer not to heat their homes with their amps, back to our regularly scheduled high bias class A discussion.
An interesting claim - Has anybody heard of another amp using vertical fets?
Atkinson really knows electronics. The Halcro patent references the Pass Stasis patent, but I was unable to view the images on the USPTO site.
Now, with all due respect to those who prefer not to heat their homes with their amps, back to our regularly scheduled high bias class A discussion.
My first clone uses one 30-0-30 500vA transformer for both channels. The one I am finishing now uses two 28-0-28 500vA set up as mono block PSUs. I have not had it all hooked up yet.
I am still waiting to get the materials to build the chassis. One thing I did notice and posted earlier in this thread was how much of a difference it made in the bass when I turned up the bias. That was testing with a 25-0-25 400vA trannie. Ihadn't received the 28-0-28 trannies yet.
Before you change a lot of things, try increasing the bias a bit and listen to the difference. You might be surprized.
Blessings, Terry
I am still waiting to get the materials to build the chassis. One thing I did notice and posted earlier in this thread was how much of a difference it made in the bass when I turned up the bias. That was testing with a 25-0-25 400vA trannie. Ihadn't received the 28-0-28 trannies yet.
Before you change a lot of things, try increasing the bias a bit and listen to the difference. You might be surprized.
Blessings, Terry
I received my boards from Mark yesterday evening. They are wonderful Thanks go to Mark and Pinkmouse and everyone else involved in their design. I have a few questions to get me started:
1) I will start building once I get the parts GB but in the meantime can anyone point me to the posts that list what's included in the GB and what other components I need to order myself.
2) Does anyone have a line on a suitable pair of transformers? I was thinking of going with the ones that parts express sells which seem to be good value and easily available.
3) I understand that there is a PCB for the power supply. Can anyone point me in the right direction for those?
Thanks everyone. I am looking forward to putting together this project and sharing my experiences.
Philip
Thanks go to Mark and Pinkmouse and everyone else involved in their design. I have a few questions to get me started:1) I will start building once I get the parts GB but in the meantime can anyone point me to the posts that list what's included in the GB and what other components I need to order myself.
2) Does anyone have a line on a suitable pair of transformers? I was thinking of going with the ones that parts express sells which seem to be good value and easily available.
3) I understand that there is a PCB for the power supply. Can anyone point me in the right direction for those?
Thanks everyone. I am looking forward to putting together this project and sharing my experiences.
Philip
philiprst said:I received my boards from Mark yesterday evening. They are wonderful
1) I will start building once I get the parts GB but in the meantime can anyone point me to the posts that list what's included in the GB and what other components I need to order myself.
2) Does anyone have a line on a suitable pair of transformers? I was thinking of going with the ones that parts express sells which seem to be good value and easily available.
3) I understand that there is a PCB for the power supply. Can anyone point me in the right direction for those?
Thanks everyone. I am looking forward to putting together this project and sharing my experiences.
Philip
1) I believe you will need to buy your output devices and the drivers. I think Troy is including the small transistors.
2) I'm using two or these. I would send John Ngo and email and ask for a special deal for a pair. Tell him Terry sent you. I have used a few of his transformers and they work very well and are quiet.
3)I believe Mark is handling those as well.
Looking forward to seeing your progress and hearing you opinion once you're done.
Blessings, Terry
Krell Xfmrs
Okay, now you and Mark have me confused. Using a single 30-0-30 or 28-0-28 to power two PSUs makes sense to me. But if you use two 28-0-28s, are you applying a 56v potential to each PSU? Then the rectifier bridge would be outputting about 79vdc to the regulator section on the PSU....correct? Quite a large voltage drop for the regulator to get down to the desired rail voltage. Am I missing something? It seems if you are using two xfmrs, you only need a single secondary at 28 to 30v.
Robert
still4given said:
Okay, now you and Mark have me confused. Using a single 30-0-30 or 28-0-28 to power two PSUs makes sense to me. But if you use two 28-0-28s, are you applying a 56v potential to each PSU? Then the rectifier bridge would be outputting about 79vdc to the regulator section on the PSU....correct? Quite a large voltage drop for the regulator to get down to the desired rail voltage. Am I missing something? It seems if you are using two xfmrs, you only need a single secondary at 28 to 30v.
Robert
Funny, I just bought 4 of these:
http://cgi.ebay.com/25V-400VA-Toroi...QitemZ3865085021QQcategoryZ4660QQcmdZViewItem
From John and received 23 volt transformers instead of 25. I’m not concerned since they are still plenty large enough for my uses.
I plan on making 2 mono Krell KSA-50 clones and 2 Mono Pass Mini-A / A30 clones.
I also bought several of the Apex.jr 68K 50 or 63 volt caps and the BrianGT pwr supply brds from the Mini-A GB.
As for parts, I used Al’s last BOM and ordered everything except the output devices, and resistors (Emitter?). All parts for the main board and driver board should be included, and we are just awaiting the remainder of the Welbonre Labs order. (THEY STILL HAVE NOT CONTACTED ME WITH AN ESTIMATED DELIVERY DATE!)
This was the order #
Date: Mon Sep 26 08:31:54 PDT 2005
From: wlabs@ix.netcom.com
To: stgrab@yahoo.com
Subject: welbornelabs # 11834
------ Begin of Receipt -----
Confirmation #........... = 11834
Total.................... = 52.80
Handling Charge.......... = 8.00
Grand Total.............. = 60.80
Amount paid.............. = 60.80
Payment Method........... = master card
Merchant's Note.......... = Thank you for you order
------ End of Receipt
Almost @ 30 days!
http://cgi.ebay.com/25V-400VA-Toroi...QitemZ3865085021QQcategoryZ4660QQcmdZViewItem
From John and received 23 volt transformers instead of 25. I’m not concerned since they are still plenty large enough for my uses.
I plan on making 2 mono Krell KSA-50 clones and 2 Mono Pass Mini-A / A30 clones.
I also bought several of the Apex.jr 68K 50 or 63 volt caps and the BrianGT pwr supply brds from the Mini-A GB.
As for parts, I used Al’s last BOM and ordered everything except the output devices, and resistors (Emitter?). All parts for the main board and driver board should be included, and we are just awaiting the remainder of the Welbonre Labs order. (THEY STILL HAVE NOT CONTACTED ME WITH AN ESTIMATED DELIVERY DATE!)
This was the order #
Date: Mon Sep 26 08:31:54 PDT 2005
From: wlabs@ix.netcom.com
To: stgrab@yahoo.com
Subject: welbornelabs # 11834
------ Begin of Receipt -----
Confirmation #........... = 11834
Total.................... = 52.80
Handling Charge.......... = 8.00
Grand Total.............. = 60.80
Amount paid.............. = 60.80
Payment Method........... = master card
Merchant's Note.......... = Thank you for you order
------ End of Receipt
Almost @ 30 days!