I think the difference is whether people are paying with a PayPal balance or a credit card to their PayPal account. International orders tack on an extra point.
Have you thought of making a voltage doubler? Just steal the circuit in the A75 front end PSU. It wouldn't take a big piece of real estate.
Have you thought of making a voltage doubler? Just steal the circuit in the A75 front end PSU. It wouldn't take a big piece of real estate.
Bob, This is my A-75/250 amp. My trannies have extra auxiliary windings - 12 and 20 volt - I am going to series the 12 volt with the main secondary winding and then I should have a good 16 volts dc over the rails for the frontend. I think this will work. I tried it temporary and all was well. I guess I should put a 100 ohm resistor in there to keep the available current in check. I made two little boards with the electrolytic and film caps you recommended for the supply to the frontend, also has a small homemade rectifier on it. Just makes me mad I did not order the correct trannies. Not thinking again.
Thanks Tad
Thanks Tad
That should work fine as long as the windings are completely separate. The 100R is also a decent idea - Use a 1-2W resistor for reliability.
I've got a couple dual 15V transformers for just the same application.
I've got a couple dual 15V transformers for just the same application.
Actually, the previous owner "hacked it up"; I just saw it as a huge power supply and lots of heat sinks for the money... The original design was prone to blow-ups(usually caused by DC offset frying the unlucky loudspeakers)...Also, I read that both the original input and output devices are obsolete and now impossible to source (Per Paul McGowan himself).
Here's a picture of how this particular 200C's front panel looks (it really was "hacked up"!!) I'll have to refinish it somehow... any ideas for refinishing scratched/scuffed anodized aluminum?
Thanks for your input guys! 🙂
-chas
Attachments
clm811
You might not be able to put the black finish back on real easy but sanding the front in one direction with good 220 grit paper will give you a nice brushed aluminum look. Then you can seal it. You could anodize it at home -- lots of stuff on the web-- but it might be more project than you want.
Tad
You might not be able to put the black finish back on real easy but sanding the front in one direction with good 220 grit paper will give you a nice brushed aluminum look. Then you can seal it. You could anodize it at home -- lots of stuff on the web-- but it might be more project than you want.
Tad
Assuming you're not in a hurry, I've heard that commercial anodizers can remove the old coating and anodize fairly cheaply. The way to get the cost down is to leave the parts with them to fit in when they have extra space in a batch.
That's the usual deal overhere, and cheaper than most would guestimate.
Same same for chromed parts, but for chroming there's the risc they won't pay much attention to it and not much later the chroming starts to peel off. (speaking from repeated experience)
Alternative is to have the front panel powder coated, other than looks it makes little sense to have an anodised front, especially with the heatsink set up of the 200C.
Still looks like a great deal to me, even after 25? years the 200C chassis is oh-so-pretty.
Same same for chromed parts, but for chroming there's the risc they won't pay much attention to it and not much later the chroming starts to peel off. (speaking from repeated experience)
Alternative is to have the front panel powder coated, other than looks it makes little sense to have an anodised front, especially with the heatsink set up of the 200C.
Still looks like a great deal to me, even after 25? years the 200C chassis is oh-so-pretty.
Guess I should get total of four...
If there are any defaults/cancellations, I'd like to increase my order to 4(FOUR) boards. standing by with Paypal ready to go...
-chas
BTW are there any listener impressions or reviews of the Leach amp online? I did a google and didn't find .
TIA
-chas
If there are any defaults/cancellations, I'd like to increase my order to 4(FOUR) boards. standing by with Paypal ready to go...
-chas
BTW are there any listener impressions or reviews of the Leach amp online? I did a google and didn't find .
TIA
-chas
There have been some inquiries for more boards than we have available. I really need those folks who are on the wiki to send confirmation emails. If you do not want the boards please take your name off the wiki list so others may get involved or SEND CONFIRMATION.
Tad
Tad
I will try but some of the diy audio signatures are hard to match to the actual person. Do it yourself would work best. Tad
confirmation order 2 pcb
Thank's to tryonziess for the new group buy.
Ted I have send an email confirmation to you at email ***address removed by moderating team*** for 2 pcb to ship at my address in Italy.
I hope that the email will arrive.
Best regards, Giuseppe.
[EDIT] Email removed by the Moderation team[/EDIT]
Thank's to tryonziess for the new group buy.
Ted I have send an email confirmation to you at email ***address removed by moderating team*** for 2 pcb to ship at my address in Italy.
I hope that the email will arrive.
Best regards, Giuseppe.
[EDIT] Email removed by the Moderation team[/EDIT]
Hey Guiseppe -
For future reference, it's not nice to post people's email address in forums. Web bots look for fresh email addresses to add to spam lists. Wonder how I know? 🙁
I hope the mods notice and delete Tad's address.
For future reference, it's not nice to post people's email address in forums. Web bots look for fresh email addresses to add to spam lists. Wonder how I know? 🙁
I hope the mods notice and delete Tad's address.
I see some of the WIKI starting to fill in. Some in front and after me. Should I be concerned that I haven't seen the invoice yet?
I sent in my addy and preferance.
Ray
Information is not knowledge
Knowledge is not wisdom
Wisdom is not truth
Truth is not beauty
Beauty is not love
Love is not music
Music is the best !
Frank Zappa.
I sent in my addy and preferance.
Ray
Information is not knowledge
Knowledge is not wisdom
Wisdom is not truth
Truth is not beauty
Beauty is not love
Love is not music
Music is the best !
Frank Zappa.
Using T03 Transistors with Leach clone boards?
I suspect that the MJ21195/6 Transistors (TO3 case )will work best for my PSA 200C power supply 75v-0-75v- especially if I want to still use high-bias output. (My speakers are a pretty even 4ohm load) & I can get these devices cheaply from Digikey...
I was wondering if it would be possible(or problematic-?) to run these from the 10 transistor Leach clone boards, say by running short leads to the transistors...?
My 4.5"x 7" heat sinks and pos/neg copper rails are set up for this type of T03 case transistor...
Photo attached, showing one Leach board silkscreen superimposed above the old 200C PC boards.
(Am I barking up the wrong tree here?)
TIA,
chas.
I suspect that the MJ21195/6 Transistors (TO3 case )will work best for my PSA 200C power supply 75v-0-75v- especially if I want to still use high-bias output. (My speakers are a pretty even 4ohm load) & I can get these devices cheaply from Digikey...
I was wondering if it would be possible(or problematic-?) to run these from the 10 transistor Leach clone boards, say by running short leads to the transistors...?
My 4.5"x 7" heat sinks and pos/neg copper rails are set up for this type of T03 case transistor...
Photo attached, showing one Leach board silkscreen superimposed above the old 200C PC boards.
(Am I barking up the wrong tree here?)
TIA,
chas.
Attachments
-or...
Would you all recommed using 5 pairs of MJL4281/MJL4302 instead, with my 75-0-75v rails, and horizontal mounting the board (not using the copper plus/minus rails) w/just the twin 4.5"x 7"heat sinks, one for the 4281's and one for the 4302's )?
Again, thanks for any input here.
-chas
Would you all recommed using 5 pairs of MJL4281/MJL4302 instead, with my 75-0-75v rails, and horizontal mounting the board (not using the copper plus/minus rails) w/just the twin 4.5"x 7"heat sinks, one for the 4281's and one for the 4302's )?
Again, thanks for any input here.
-chas
5pair of MJL4302/4281 (To264 230W) is a superb output stage and will work very well on a +-75Vdc supply. If the PSU is up to the job I would expect 550W into 4r0 and capable of driving a severe reactance speaker with phase angles approaching 60degrees.
Direct connection of the outputs to the heatsink is always better than using an aluminium mounting block/angle, except when the angle is formed from thick copper. This distributes the heat more evenly along the sink particularly when few devices and a thin backplate are combined.
Your 5pair and thick backplate cannot use the copper to any significant advantage. I suggest you ditch it and go for direct fixing.
Are you building 2channels? i.e. 10off each device. Buy 12off each and select the 5 closest in the lower group and 5 closest in the upper group for the NPNs. Repeat for the PNPs. This should give adequate matching of the BJTs.
Direct connection of the outputs to the heatsink is always better than using an aluminium mounting block/angle, except when the angle is formed from thick copper. This distributes the heat more evenly along the sink particularly when few devices and a thin backplate are combined.
Your 5pair and thick backplate cannot use the copper to any significant advantage. I suggest you ditch it and go for direct fixing.
Are you building 2channels? i.e. 10off each device. Buy 12off each and select the 5 closest in the lower group and 5 closest in the upper group for the NPNs. Repeat for the PNPs. This should give adequate matching of the BJTs.
brutepuppy, I sent you an invoice Saturday and again this morning. I am not getting any information that the email did not go through. It was sent to the reply on your confirmation.
Do not be looking for and attachment just the simple addition of all the charges for you to remit. Nothing formal. Tad
Do not be looking for and attachment just the simple addition of all the charges for you to remit. Nothing formal. Tad
Tryonziess: You've got mail!
Tryonziess: You've got mail(and payment)!
Andrew T:
Actually, I'll probably buy 25pcs each, so I can match and do a total of 4 channels. 😉
& Thanks to you both (plus all the other contributers,especially Jens )! 🙂
-chas
p.s. I picked up another PS Audio 200C yesterday(although for double the price of the first); These make a MONDO platform for this amp (plus I'll recycle all that copper to offset my parts cost). 😀
Tryonziess: You've got mail(and payment)!
Andrew T:
Actually, I'll probably buy 25pcs each, so I can match and do a total of 4 channels. 😉
& Thanks to you both (plus all the other contributers,especially Jens )! 🙂
-chas
p.s. I picked up another PS Audio 200C yesterday(although for double the price of the first); These make a MONDO platform for this amp (plus I'll recycle all that copper to offset my parts cost). 😀