I purchased one of these from a Hong Kong seller at ebay.ckwong99 said:
There are actually 4 heatsinks, 2 on each side. Since the Leach board has the output transistor on one side of board, a heat spread plate is needed because there is no way for one heat sink to dissipate the heat, but then a 0.25" copper plate will cost as much as a Conrad heatsink, duh!! The fins are only 1" tall, so I don't think it is adequate for any high rail voltage (60+??) and hotter than "stock" bias. Also, the silk screen in the front is somewhat annoying, any suggestion on how to get rid of it
Edit: I paid close to double the price with shipping and profit of the ebay middle-man
The price already list in the WEB site is CNY 650 , so that exchange to other countries USD$95 and EUR$75.
Currency exchange ref link :
http://finance.sina.com.hk/cgi-bin/forex/calculate.cgi
I have even contact the shop if ship to HK about HKD$140. This WEB DIY component is quite popular in China and Asia. If anyone interest it can try the following email quote a shipping price. They can read English .
lsaudio@pub.guangzhou.gd.cn
Actually, China can find many fake things but in general I will choose some hardware like this stuff. It should not be fake making and easily be discovered.
Few years ago I bought a Peramp case all alumnium only HKD260 on this site. So far so good use up to 3 years.
Currency exchange ref link :
http://finance.sina.com.hk/cgi-bin/forex/calculate.cgi
I have even contact the shop if ship to HK about HKD$140. This WEB DIY component is quite popular in China and Asia. If anyone interest it can try the following email quote a shipping price. They can read English .
lsaudio@pub.guangzhou.gd.cn
Actually, China can find many fake things but in general I will choose some hardware like this stuff. It should not be fake making and easily be discovered.
Few years ago I bought a Peramp case all alumnium only HKD260 on this site. So far so good use up to 3 years.
Carl,
Thanks for the update on the Super guy.
What kind of deminsions are you needing for the heatsinks. I have several 6x6x2,5 heatsinks which I use and mount to a .250 plate. Would you consider them.
Any hints on what kind of rail juice you are using for the tests. We all have been patiently waiting for this beast for quite some time. There is some serious interest in it. Thanks for all of your hard work.
Bob,
Of course most of us do not need 250 plus watts it is just something leftover from the old rock and roll era. Kind of like 600 horsepower cars and big motorcycles. Never enough juice. You know a guy thing. Wonder why we are like that. Heck you road around in a 50000 horsepower jet. Now that is cool. One percent of one percent. Not many get to go there.
Tad
Thanks for the update on the Super guy.
What kind of deminsions are you needing for the heatsinks. I have several 6x6x2,5 heatsinks which I use and mount to a .250 plate. Would you consider them.
Any hints on what kind of rail juice you are using for the tests. We all have been patiently waiting for this beast for quite some time. There is some serious interest in it. Thanks for all of your hard work.
Bob,
Of course most of us do not need 250 plus watts it is just something leftover from the old rock and roll era. Kind of like 600 horsepower cars and big motorcycles. Never enough juice. You know a guy thing. Wonder why we are like that. Heck you road around in a 50000 horsepower jet. Now that is cool. One percent of one percent. Not many get to go there.
Tad
Tad,
What I am really looking for is something for use on the test bench. My plan is to first build a single channel and then excersize that channel with an AP box attached. A pair of the described heatsinks joined with an aluminum plate would work for that purpose. What do you want for them?
I will be running 70 volt rails (at least initially) and experimenting with a variac to find an optimum.
Once I get data from the test bench I expect to order extrusions from a source yet to be determined. Would builders here be interested in doing a group buy on a custom chassis? We would be getting chassis from the same shops that do commercial product cabs every day. I would expect that a custom chassis (including heatsinks) would be $130 to 150 each. That's US $$ coming from southern California.
What I am really looking for is something for use on the test bench. My plan is to first build a single channel and then excersize that channel with an AP box attached. A pair of the described heatsinks joined with an aluminum plate would work for that purpose. What do you want for them?
I will be running 70 volt rails (at least initially) and experimenting with a variac to find an optimum.
Once I get data from the test bench I expect to order extrusions from a source yet to be determined. Would builders here be interested in doing a group buy on a custom chassis? We would be getting chassis from the same shops that do commercial product cabs every day. I would expect that a custom chassis (including heatsinks) would be $130 to 150 each. That's US $$ coming from southern California.
When I rough costed this 30 days ago it was for mono chassis using a single MK6243 extrusion from M&M Metals. The package measured (roughly) 13 inches deep by 10 inches wide by 7 inches tall. Essentially a three sided box with 10mm brushed aluminum faceplate. Black powder coated with a natural aluminum face. The cost for box and heatsink was $130 to $150 dependent upon number purchased.
No pictures or drawings to share as of yet. My conversation with the vendor was ballparked based on experience accompanied by a lot of hand waving. At some point there will be drawings. If there is interest here I will share them at that time.
Here is the heatsink profile. http://www.mmmetals.com/extrusions/drawings/MK62430.jpg
Here is the heatsink profile. http://www.mmmetals.com/extrusions/drawings/MK62430.jpg
"Would it be possible to get a quote on a stereo chassis?"
Sure. But be clear it will be after the Holidays before I get a chance to generate drawings, post them here and get a real quote to have them fabbed. My first order of business is to wring out the SuperAmp and document the results. Let me extend my heartfelt thanks to both Professor Leach for the original design and to Jens Rasmussen for revving it to use modern parts.
Sure. But be clear it will be after the Holidays before I get a chance to generate drawings, post them here and get a real quote to have them fabbed. My first order of business is to wring out the SuperAmp and document the results. Let me extend my heartfelt thanks to both Professor Leach for the original design and to Jens Rasmussen for revving it to use modern parts.
Hi,
my 230:40+40Vac transformer, feeding the 3pair PCB, gave 411W into 4r0 when mains was ~240Vac.
This would require a transformer between 400VA and 800VA for a single channel.
I chose 1000VA for a two channel amp, I don't have any 4ohm speakers.
A 45Vac transformer should be even bigger due to the extra power potential. 750VA for a 4ohm single channel amplifier (5pair PCB)?
my 230:40+40Vac transformer, feeding the 3pair PCB, gave 411W into 4r0 when mains was ~240Vac.
This would require a transformer between 400VA and 800VA for a single channel.
I chose 1000VA for a two channel amp, I don't have any 4ohm speakers.
A 45Vac transformer should be even bigger due to the extra power potential. 750VA for a 4ohm single channel amplifier (5pair PCB)?
While I tend towards big transformers, I am less aggressive than Andrew. I have no 4 ohm speakers either. I have 1,000VA in my A75s - 2 channels idling at 300W total. I also run a 4 channel Leach on an 800VA dual 40V transformer. This is for a biamp setup crossing at 2,000 Hz, so half the channels produce very little power. The rails sag from 59V to 56 at unreasonable loud volume.
At 40VAC rated you'll be safer using 63 rated caps. Notice above that my 40VAC transformer gives me 59V rails. I've seen as high as 61. This is because the transformer is designed for worst case mains conditions, at 115/230VAC input it will produce its rated 40VAC output. Higher input voltage leads to higher output. Also, many transformers are would a little hot, so a 40V transformer may give you 41 or 42 VAC.
My mains are sitting at 123V this morning which should give me 60V rails. I've never seen Mains voltage less than 117 according to the power conditioners at my offices. A transformer rated at 45VAC output with 115 Volts input will theoretically give you 62V rails. Now feed it 123 VAC and your rectified voltage is close to 67V. You need to go with 80 or 100V rated filter caps to be safe. They are more expensive than 63V caps, how much can your budget stand?
So, after my long winded background, my opinion is that either transformer should be suitable for a single channel, with a slight preference for the 40V.
At 40VAC rated you'll be safer using 63 rated caps. Notice above that my 40VAC transformer gives me 59V rails. I've seen as high as 61. This is because the transformer is designed for worst case mains conditions, at 115/230VAC input it will produce its rated 40VAC output. Higher input voltage leads to higher output. Also, many transformers are would a little hot, so a 40V transformer may give you 41 or 42 VAC.
My mains are sitting at 123V this morning which should give me 60V rails. I've never seen Mains voltage less than 117 according to the power conditioners at my offices. A transformer rated at 45VAC output with 115 Volts input will theoretically give you 62V rails. Now feed it 123 VAC and your rectified voltage is close to 67V. You need to go with 80 or 100V rated filter caps to be safe. They are more expensive than 63V caps, how much can your budget stand?
So, after my long winded background, my opinion is that either transformer should be suitable for a single channel, with a slight preference for the 40V.
You've discovered that there is no hard and fast rule for class AB, other than as big as your budget allows is best. I think that Andrew's approach is closer to being able to deliver full rated power 24/7. I go a bit overkill, but temper that with my cheapskate tendencies.Some AB amps (musical instrument and inexpensive PA) will use a very small transformer so that rail sag acts as another protection circuit. My son trash picked a Fender guitar amp that had a (barely) 100 VA transformer for its 100W rating. MI amps tend to be driven to rated power for extended periods and the thermal fuse in the transformer was blown.
In most home applications, your amps will not be driven anywhere near full power for very long, so heating the transformer is less of an issue. Toroidal power transformers can handle substantial overloads for short periods. Not that I would size it for average use (<50W out), but you see why I think that you can get away with smaller than continuous power rating. If I can, I like to go with the transformer rating at 2x the expected power out, for the speakers I intend to drive.
Class A amps are another beast. If you are dissipating 100W in the output your transformer sees a load of 200VA - the capacitor charging current is equal to the load current. (simulate this in PSU Designer). So if you size a class A transformer at 2x the dissipation, you are really running it at its maximum. This is where the 3-5x dissipation rule of thumb comes from. At 3x dissipation you are running the transfromer at 2/3 its max, and you will see noticeable heating.
Professor Leach recommended 600-800VA for a stereo amp. You'd be fine with 500 VA per monoblock. At 45VAC you might see a bt of rail droop pushing 400W+ into 4 ohms, but chances are you won't be pushing it that hard except on the test bench.
That said, if you are buying new transformers, the price difference between 500VA and 800 VA is only about $20 at Parts Express, so why not?
thx Bob
I like to find a universal solution for a using a same transformer In both power amps - Leach and Krell 100 MKII I am building
I like to try also how will sound Leach amp with 1 transformer for a stereo amp and 1 transformer per channel
I like to get a quote for a custom audio grade transformer - thats why I am trying to clear some aspects
at moment I am at - 800 VA transformer 2 x 37.5 VAC
there will be 1 or 2 pcs for a Leach stereo and 2 pcs for a Krell stereo
I think that 37.5 Vac will be enough for a Input stages of the amps, also I will try using Regulator Board for LTP
what do you think
I am asking because I have found at nuvotem.com the 500 VA transformer which Is fine looking - encapsulated and with very low noise at reasonable price
I like to find a universal solution for a using a same transformer In both power amps - Leach and Krell 100 MKII I am building
I like to try also how will sound Leach amp with 1 transformer for a stereo amp and 1 transformer per channel
I like to get a quote for a custom audio grade transformer - thats why I am trying to clear some aspects
at moment I am at - 800 VA transformer 2 x 37.5 VAC
there will be 1 or 2 pcs for a Leach stereo and 2 pcs for a Krell stereo
I think that 37.5 Vac will be enough for a Input stages of the amps, also I will try using Regulator Board for LTP
what do you think
I am asking because I have found at nuvotem.com the 500 VA transformer which Is fine looking - encapsulated and with very low noise at reasonable price