Thanks Bob
I was hoping that you were still subscribed to the thread, Bob.
I will read of the A75 Article. If it is feasible with my limited experience to pursue the voltage doubler circuit, I will certainly take you up on your offer to help guide me through it. I will probably have questions. Thanks so much.
Fred
I was hoping that you were still subscribed to the thread, Bob.
I will read of the A75 Article. If it is feasible with my limited experience to pursue the voltage doubler circuit, I will certainly take you up on your offer to help guide me through it. I will probably have questions. Thanks so much.
Fred
I have looked at the A75 article link that you posted. I have copied the voltage doubler circuit, as I understand it, from the Pass article into the attached bitmap. Could you have a peek and see if it is correct?
If it is correct, can the Pass values for the components be used although the supply in the article is only 30V?
Also, if I can paraphrase your earlier post, the transformer would feed both the voltage doubler and a bridged circuit. The voltage doubler would then supply the PSU 2.2 board which then connects to the VCC and VSS posts on the Leach pcb to feed the front end of the Leach. The bridged circuit would connect at the forward end of the fuse component on the Leach pcb to supply the output transistors only.
Thanks for your help. Fred
If it is correct, can the Pass values for the components be used although the supply in the article is only 30V?
Also, if I can paraphrase your earlier post, the transformer would feed both the voltage doubler and a bridged circuit. The voltage doubler would then supply the PSU 2.2 board which then connects to the VCC and VSS posts on the Leach pcb to feed the front end of the Leach. The bridged circuit would connect at the forward end of the fuse component on the Leach pcb to supply the output transistors only.
Thanks for your help. Fred
You've got the DC voltages connected to the wrong spots. The rail with C6 should go to AC1-1, the rail with C7 to AC2-2. You can jumper D3 and D13 and leave the rest of the components in that area out. Leave the other AC connections alone and connect the board grounds to the star.
The output stage power connects to VCC and VSS on Jens' Leach board. Doubler connects to PSU2.2 which in turn connects to VC and VS. Be sure to OMIT R1 and R23, which are the connections between front end and output in the unregulated versions.
The output stage power connects to VCC and VSS on Jens' Leach board. Doubler connects to PSU2.2 which in turn connects to VC and VS. Be sure to OMIT R1 and R23, which are the connections between front end and output in the unregulated versions.
Forgot to comment on parts selection.
Yes, 470 uf 00V caps are fine.
The diodes can be anything good for 1A/200PIV. I use 1N4007 because there's no penalty for higher PIV and it's cheaper to buy in large quantity. You can try something like MUR120 if you want to be creative.
The resistors can be almost anything. They are there to reduce the dissipation in the regulators by dropping some voltage. Although Pass doesn't specify, I used 10R/3W in mine.
Yes, 470 uf 00V caps are fine.
The diodes can be anything good for 1A/200PIV. I use 1N4007 because there's no penalty for higher PIV and it's cheaper to buy in large quantity. You can try something like MUR120 if you want to be creative.
The resistors can be almost anything. They are there to reduce the dissipation in the regulators by dropping some voltage. Although Pass doesn't specify, I used 10R/3W in mine.
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Thanks Bob,
I've had another go at the diagram as attached. I tried to match the polarities in the Pass document and I hope that I have them correct as well. I am not yet sure that the connections to the PSU are labelled correcly yet but I should be getting close.
I misread the Pass transformer power as 30V but it was 38V so of course the component values would work here as well. Pass also used the 10R resistor in his circuit.
Your instructions of how to connect the PSU and transformer bridged power to the Leach pcb was very clear. I have just begun to re-read the Leach thread and I can't recollect reading where it explains how to do this. One should be building along with the thread development but I never had the parts at hand and put it off too long. Now its an uphill struggle to reread everything and put it together comprehensively. As an inexperienced builder it is difficult to read the threads, the Leach site information which has different component numbers, electrical schmatics and also master what the electrical components functionally do. But I am finally determined to accomplish this project. Jens' boards and development efforts along with all the work that you did are just too good to be wasted.
My PSU is fully stuffed from when I first built it (2006?), so I will remove D2, D4, D12, D14, C1, C8, C19, C26 as per your post on page 18.
I've had another go at the diagram as attached. I tried to match the polarities in the Pass document and I hope that I have them correct as well. I am not yet sure that the connections to the PSU are labelled correcly yet but I should be getting close.
I misread the Pass transformer power as 30V but it was 38V so of course the component values would work here as well. Pass also used the 10R resistor in his circuit.
Your instructions of how to connect the PSU and transformer bridged power to the Leach pcb was very clear. I have just begun to re-read the Leach thread and I can't recollect reading where it explains how to do this. One should be building along with the thread development but I never had the parts at hand and put it off too long. Now its an uphill struggle to reread everything and put it together comprehensively. As an inexperienced builder it is difficult to read the threads, the Leach site information which has different component numbers, electrical schmatics and also master what the electrical components functionally do. But I am finally determined to accomplish this project. Jens' boards and development efforts along with all the work that you did are just too good to be wasted.
My PSU is fully stuffed from when I first built it (2006?), so I will remove D2, D4, D12, D14, C1, C8, C19, C26 as per your post on page 18.
OK, my description was flawed. I meant to say the rail connected to C6, etc.
So ground the negative side of C6 and the positive side of C7. The connection that you labeled AC2-2 should be AC1-1. The terminal you labeled AC1-2 should be AC2-2. Out 1-1 and Out 2-1 connect to the star ground - if looking at the output connections from the LED end of the board the grounds are on the left. You can see their ground plane connections quite easily.
You won't hurt anything leaving the diodes and caps in place as long as the other AC connections are left unused. In fact, with the diodes in place it doesn't matter which AC connection you use. Just connect the positive output of the doubler to one of the AC terminals of the positive regulator and one the negative double output to one of the negative side terminals. On both regulators leave the other AC terminal un-connected. The net result will be ~.6V less into the regulator, which won't be an issue, just a few mW less to dissipate in T1 and T8.
Jens addresses the split supply in the BOM, with the comment n teh value of R1 and R23:
The other TBD resistors are protection circuit resistors. Towards the end of the Jens Leach thread is a spreadsheet for calculating the values. Use the one that follows mine. This will give you dual slope protection. There are spots for resistors that aren't on the schematic for triple slope protection. This would allow using more of the SOA, but it is unclear to most how to calculate the appropriate values. Just leave them out.
P1 can be 5K, much easier to find on this side of the pond.
So ground the negative side of C6 and the positive side of C7. The connection that you labeled AC2-2 should be AC1-1. The terminal you labeled AC1-2 should be AC2-2. Out 1-1 and Out 2-1 connect to the star ground - if looking at the output connections from the LED end of the board the grounds are on the left. You can see their ground plane connections quite easily.
You won't hurt anything leaving the diodes and caps in place as long as the other AC connections are left unused. In fact, with the diodes in place it doesn't matter which AC connection you use. Just connect the positive output of the doubler to one of the AC terminals of the positive regulator and one the negative double output to one of the negative side terminals. On both regulators leave the other AC terminal un-connected. The net result will be ~.6V less into the regulator, which won't be an issue, just a few mW less to dissipate in T1 and T8.
Jens addresses the split supply in the BOM, with the comment n teh value of R1 and R23:
Just use the Jens supplied BOM and build up. R3 and R23 are calculated as R(Kohms)=(V-40)/8.2 The V is your front end voltage. So if you use 65V, R2/23 are 3.05K The only impact of being off a bit is to alter the current in the zeners, so it's better to err on the low resistance side. 3k or 3.01K are fine.
The other TBD resistors are protection circuit resistors. Towards the end of the Jens Leach thread is a spreadsheet for calculating the values. Use the one that follows mine. This will give you dual slope protection. There are spots for resistors that aren't on the schematic for triple slope protection. This would allow using more of the SOA, but it is unclear to most how to calculate the appropriate values. Just leave them out.
P1 can be 5K, much easier to find on this side of the pond.
Version 3
Bob, you are too fast for me but more than helpful. You have already anticipated and answered many of my questions pertaining to the Leach and the PSU. Hopefully, I can find out most of the remaining information myself through reading and searching the old threads.
Yes, the PSU ground plane became apparent after your first post when I saw on an unpopulated pcb, how the pad has an insulating ring around it on the upper side if it is not connected to the ground plane or no ring if it is connected.
I have populated most of the front end of the Leach pcb. Unfortunately I had soldered in the 20V zeners before reading the instructions in the thread to match them. I understand that it makes the biasing less accurate but I will have to order some more and replace them later if the biasing is too far out. Similarly the 340/350 transistors should be matched but I only have 4 of each with one even from a different manufacturer. So matching may be difficult here as well but I will see how they measure.
Your resistor value calculations were very useful and most timely. Only R1 & R22 (not used), R3, R22,R26 &R34, R28 & R30, R68 & R69, the vertical fuseholder (which I don't have), the hardware for F1 & F2, VCC & VSS remain to be soldered in the pcb. I have not found the spreadsheet that you mention posted on the forum but I did email AndrewT to send it as he stated in numerous posts. The resistor values that you supplied in the past post are the same as those for Still4Given with the same voltage for the FE in the thread and verify your math. Just so that you know, my output transistors are the 4281/4302 combo in the output section.
I hope that I have the voltage doubler circuit is correct now. I get the gist of its operation but have to study it in more detail to fully understand how it operates. However, if the circuit is good, I will just go from there to develop it on a piece of breadboard and tie it to the PSU without full understanding.
Thanks again. Fred
Bob, you are too fast for me but more than helpful. You have already anticipated and answered many of my questions pertaining to the Leach and the PSU. Hopefully, I can find out most of the remaining information myself through reading and searching the old threads.
Yes, the PSU ground plane became apparent after your first post when I saw on an unpopulated pcb, how the pad has an insulating ring around it on the upper side if it is not connected to the ground plane or no ring if it is connected.
I have populated most of the front end of the Leach pcb. Unfortunately I had soldered in the 20V zeners before reading the instructions in the thread to match them. I understand that it makes the biasing less accurate but I will have to order some more and replace them later if the biasing is too far out. Similarly the 340/350 transistors should be matched but I only have 4 of each with one even from a different manufacturer. So matching may be difficult here as well but I will see how they measure.
Your resistor value calculations were very useful and most timely. Only R1 & R22 (not used), R3, R22,R26 &R34, R28 & R30, R68 & R69, the vertical fuseholder (which I don't have), the hardware for F1 & F2, VCC & VSS remain to be soldered in the pcb. I have not found the spreadsheet that you mention posted on the forum but I did email AndrewT to send it as he stated in numerous posts. The resistor values that you supplied in the past post are the same as those for Still4Given with the same voltage for the FE in the thread and verify your math. Just so that you know, my output transistors are the 4281/4302 combo in the output section.
I hope that I have the voltage doubler circuit is correct now. I get the gist of its operation but have to study it in more detail to fully understand how it operates. However, if the circuit is good, I will just go from there to develop it on a piece of breadboard and tie it to the PSU without full understanding.
Thanks again. Fred
the protection spreadsheet is here: http://www.diyaudio.com/forums/grou...mp-pcb-group-buy-interest-32.html#post2364365
Not sure how you can match the 340s and 350s. Are you confusing them with matching the front end T2-T3 and T4-T5? Matching the zeners is ideal, but you may find everything works just fine without any effort.
Just ask if you need help.
Not sure how you can match the 340s and 350s. Are you confusing them with matching the front end T2-T3 and T4-T5? Matching the zeners is ideal, but you may find everything works just fine without any effort.
Just ask if you need help.
The 340/350 reference was to T8, T9, T13 and T14. There was a reference in a thread which gives a circuit to measure the closeness of pairs, If I recall correctly it was in the Leach site. Perhaps it is not too important. But I can certainly be confused especially as I do the computer work in front of a TV and not anywhere near the documentation and pcbs.
Thanks for the ss. Will have a look at it tomorrow.
Cheers, Fred
Thanks for the ss. Will have a look at it tomorrow.
Cheers, Fred
You were correct Bob.
I attempted to find the reference and it is in the Leach notes. But the transistors to be matched are the T1, T2 etc. So I was confused. At my age one should never write from memory late at nighwithout checking the references.
I never matched those either but I will see how it goes before pulling any.
I attempted to find the reference and it is in the Leach notes. But the transistors to be matched are the T1, T2 etc. So I was confused. At my age one should never write from memory late at nighwithout checking the references.
I never matched those either but I will see how it goes before pulling any.
It's been a while but I would like to report back, Bob.
I have just hooked up the voltage doubler and the PSU. When first powered up the output of the +ve channel was 64.2 and the -ve one 68.3. Adjusting the pot on the -ve channel brought it down to 64.2 also. they are now matched. So that is the voltage that will go to the VC and VS connections on the Leach pcb.
I have made rather amateurish capacitor banks for the amp which will accomodate 5 10K 80V caps each. If I am understanding this correctly, both the voltage doubler and diode bridge which feeds the smoothing caps will connect to the transformer. The cap banks will connect at the VCC and VSS. No resistors will be inserted at R2 and R21. The voltage at VCC and VSS should be around 40*1.4 or 56. Is my interpretation correct?
Any further questions I will submit to the Leach thread.
Thanks so much for your help Bob.
I have just hooked up the voltage doubler and the PSU. When first powered up the output of the +ve channel was 64.2 and the -ve one 68.3. Adjusting the pot on the -ve channel brought it down to 64.2 also. they are now matched. So that is the voltage that will go to the VC and VS connections on the Leach pcb.
I have made rather amateurish capacitor banks for the amp which will accomodate 5 10K 80V caps each. If I am understanding this correctly, both the voltage doubler and diode bridge which feeds the smoothing caps will connect to the transformer. The cap banks will connect at the VCC and VSS. No resistors will be inserted at R2 and R21. The voltage at VCC and VSS should be around 40*1.4 or 56. Is my interpretation correct?
Any further questions I will submit to the Leach thread.
Thanks so much for your help Bob.
LOL. It'll be a while before the Leach gets to the speakers. But it is a lot closer than it was 3 weeks ago-a blank board.
Thankyou both. I appreciate your help and patience with me. BTW, Andrew, the B1 powered up just fine, thanks to your help. I haven`t yet hooked it up for a performance. I have a lightspeed clone (dvb-projekt) to go with the B1 for volume control. Hopefully they will combine with the Leach just fine.
Bob, the resistors for R3 and RR22 are 3.9K 1W. The protection circuit .5W values that I have are:
R41-43, 60-62 1.2K
R28,30 270
R26,30 4.3K
Emitters .47R 5W
Thankyou both. I appreciate your help and patience with me. BTW, Andrew, the B1 powered up just fine, thanks to your help. I haven`t yet hooked it up for a performance. I have a lightspeed clone (dvb-projekt) to go with the B1 for volume control. Hopefully they will combine with the Leach just fine.
Bob, the resistors for R3 and RR22 are 3.9K 1W. The protection circuit .5W values that I have are:
R41-43, 60-62 1.2K
R28,30 270
R26,30 4.3K
Emitters .47R 5W
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