Zsolt
I am a bit confused.
If you followed my mod and shorted C11 etc. but did not move C8 that could be the problem – although I strongly suspect the real problem is the speed of the new output transistors as my mod makes for a more stable amp with all else being unchanged.
Even if you don’t have a scope I guess you could check for a.c. voltages where there should be none.
Measuring d.c. voltages around a transconductance amp like the 405 is almost meaningless.
You could try increasing R35 and R36 to say 10R and remove L1 and L3 – this should make the amp stable and give you a chance to measure the quiescent currents in the output.
A "normal" 405 with no signal input should take no more than 120mA.
What did you do to the input stage ??
Regards
Keith
PS updated "QUAD 405 Evolution" and "QUAD 405 Service Data" pdf available from my site may help.
I am a bit confused.
If you followed my mod and shorted C11 etc. but did not move C8 that could be the problem – although I strongly suspect the real problem is the speed of the new output transistors as my mod makes for a more stable amp with all else being unchanged.
Even if you don’t have a scope I guess you could check for a.c. voltages where there should be none.
Measuring d.c. voltages around a transconductance amp like the 405 is almost meaningless.
You could try increasing R35 and R36 to say 10R and remove L1 and L3 – this should make the amp stable and give you a chance to measure the quiescent currents in the output.
A "normal" 405 with no signal input should take no more than 120mA.
What did you do to the input stage ??
Regards
Keith
PS updated "QUAD 405 Evolution" and "QUAD 405 Service Data" pdf available from my site may help.
Keith,
I modified the input stage for non-inverting as specified on your site with the following comment: I did not added the non polarized C2B 3.3uF capacitor and leaved R12 = 3K3.
Regarding C8 issue. I already tried to put back C11 and R23 but the Tr7 collector voltage remains the same 1.65V; C8 is now at Tr2's collector.
I measured the current taken by one of the amplifier board's when idle:
+ takes ~110mA
- takes ~102mA
Other measurements taken with no input and no speakers connected, with open input:
- a current of ~36mA through R38
- a collector current of ~22mA for Tr8
Regards,
Zsolt
I modified the input stage for non-inverting as specified on your site with the following comment: I did not added the non polarized C2B 3.3uF capacitor and leaved R12 = 3K3.
Regarding C8 issue. I already tried to put back C11 and R23 but the Tr7 collector voltage remains the same 1.65V; C8 is now at Tr2's collector.
I measured the current taken by one of the amplifier board's when idle:
+ takes ~110mA
- takes ~102mA
Other measurements taken with no input and no speakers connected, with open input:
- a current of ~36mA through R38
- a collector current of ~22mA for Tr8
Regards,
Zsolt
I got your point Keith 
Yes, I'm happy with the amplifier
however, I plan to remake the pcb's in some spare time to an original Quad 405-2 clone, they looks like a trench with too many hard-wires. I plan to include some of tvicols's modifications too and post the Protel project in a new thread, probably I will have some questions too
Stefaan promissed me some pictures with the backside of a Quad 405-2, but he must be busy or forgot about it.
Keith, do you have a Quad 405-2 around (newer is better )? if yes, could you be so nice and make some pictures with it and send them to me.
Thank you,
Zsolt
p.s. on google I found pictures of pcb's for Quad 405 only
Yes, I'm happy with the amplifier
however, I plan to remake the pcb's in some spare time to an original Quad 405-2 clone, they looks like a trench with too many hard-wires. I plan to include some of tvicols's modifications too and post the Protel project in a new thread, probably I will have some questions too Stefaan promissed me some pictures with the backside of a Quad 405-2, but he must be busy or forgot about it.
Keith, do you have a Quad 405-2 around (newer is better
)? if yes, could you be so nice and make some pictures with it and send them to me.Thank you,
Zsolt
p.s. on google I found pictures of pcb's for Quad 405 only
Zsolt
Tried to attach 800k scan both sides of last 405-2 PCBs for you but site says maximum size is 1024K ?? email me I will send it to you - If I were doing this I would use a layout package linked to the schematic - Less mistakes and room to make a better layout.
Tibi and I have exchanged ideas over the years and I generally like his approach - beware chaning R30 R31 and C10 you loose the bootstap and gain little.
Did you download "QUAD 405 Evolution" from schematics on my site - the last drawing is my much reduced 405(3) that I think is about as good as it gets - LESS IS MORE - I am also looking into removing the current limit from a 306 to make it similar to my DCD 405 mod-3.
Best regards
Keith
Tried to attach 800k scan both sides of last 405-2 PCBs for you but site says maximum size is 1024K ?? email me I will send it to you - If I were doing this I would use a layout package linked to the schematic - Less mistakes and room to make a better layout.
Tibi and I have exchanged ideas over the years and I generally like his approach - beware chaning R30 R31 and C10 you loose the bootstap and gain little.
Did you download "QUAD 405 Evolution" from schematics on my site - the last drawing is my much reduced 405(3) that I think is about as good as it gets - LESS IS MORE - I am also looking into removing the current limit from a 306 to make it similar to my DCD 405 mod-3.
Best regards
Keith
Keith
My email address is zsolt_vadaszi@yahoo.com, you can send the pcb photos there. Thanks!
I saw your "QUAD 405 Evolution" document, it's a nice job.
I have some questions regarding your modification:
- why have you ommited C7, R13 from Tr2's collector?
- did you purposely shorted R35 and R36?
- you used an adjust on test resistor for R15 -> 200R-AOT; how should it be adjusted? can I use a fixed resistor there? like a 220R as Tibi did in his Revision 2 Quad Reborn?
- Tr1 and the operational's positive rail shouldn't be at the other side of R35 (of course if it's not shorted )
- what other transistor types could I use instead of 2SC2547E and 2SA1085E? I just can't find them not even on Farnell. Is it ok to use 2N5551 for Tr2, BCY71 for Tr1a/b and MPSA92 for Tr3? or a specific low noise device is needed?
Regards,
Zsolt
My email address is zsolt_vadaszi@yahoo.com, you can send the pcb photos there. Thanks!
I saw your "QUAD 405 Evolution" document, it's a nice job.
I have some questions regarding your modification:
- why have you ommited C7, R13 from Tr2's collector?
- did you purposely shorted R35 and R36?
- you used an adjust on test resistor for R15 -> 200R-AOT; how should it be adjusted? can I use a fixed resistor there? like a 220R as Tibi did in his Revision 2 Quad Reborn?
- Tr1 and the operational's positive rail shouldn't be at the other side of R35 (of course if it's not shorted
)- what other transistor types could I use instead of 2SC2547E and 2SA1085E? I just can't find them not even on Farnell. Is it ok to use 2N5551 for Tr2, BCY71 for Tr1a/b and MPSA92 for Tr3? or a specific low noise device is needed?
Regards,
Zsolt
Zsolt
you say..
"I have some questions regarding your modification":
- why have you ommited C7, R13 from Tr2's collector?
Because I see the amp as a transconductance stage and R13 only causes undesireable voltage swings and it looks like C7 is to bypass the undesireable affects of the voltage swings at higher frequencies! can cause stability issues so take care.
- did you purposely shorted R35 and R36?
Yes current limiting out - then more out!
- you used an adjust on test resistor for R15 -> 200R-AOT; how should it be adjusted? can I use a fixed resistor there? like a 220R as Tibi did in his Revision 2 Quad Reborn?
Yes if it gives the correct current Tr1a Vbe/R = about 3mA 180 t 240R probaly OK.
- Tr1 and the operational's positive rail shouldn't be at the other side of R35 (of course if it's not shorted )
Depends on the version of PCB you mod. I did have a dotted line to show both at one time sorry about the confusion.
- what other transistor types could I use instead of 2SC2547E and 2SA1085E? I just can't find them not even on Farnell. Is it ok to use 2N5551 for Tr2, BCY71 for Tr1a/b and MPSA92 for Tr3? or a specific low noise device is needed?
MPSA92 93 and equiv. should work fine for PNPs - I have used ZTX65n but not as good as MPSA43 for Tr2.
Regards,
Keith
you say..
"I have some questions regarding your modification":
- why have you ommited C7, R13 from Tr2's collector?
Because I see the amp as a transconductance stage and R13 only causes undesireable voltage swings and it looks like C7 is to bypass the undesireable affects of the voltage swings at higher frequencies! can cause stability issues so take care.
- did you purposely shorted R35 and R36?
Yes current limiting out - then more out!
- you used an adjust on test resistor for R15 -> 200R-AOT; how should it be adjusted? can I use a fixed resistor there? like a 220R as Tibi did in his Revision 2 Quad Reborn?
Yes if it gives the correct current Tr1a Vbe/R = about 3mA 180 t 240R probaly OK.
- Tr1 and the operational's positive rail shouldn't be at the other side of R35 (of course if it's not shorted )
Depends on the version of PCB you mod. I did have a dotted line to show both at one time sorry about the confusion.
- what other transistor types could I use instead of 2SC2547E and 2SA1085E? I just can't find them not even on Farnell. Is it ok to use 2N5551 for Tr2, BCY71 for Tr1a/b and MPSA92 for Tr3? or a specific low noise device is needed?
MPSA92 93 and equiv. should work fine for PNPs - I have used ZTX65n but not as good as MPSA43 for Tr2.
Regards,
Keith
OK, one last time, for the drivers use B536, for the power-transistors 2N3773.
If you know a better alternative (no way) post it to http://quadrevisionspot.blogspot.com/
If you want those transistors in your IRL-mailbox this week look @ http://stores.benl.ebay.be/DadaElectronics
Stefaan
If you know a better alternative (no way) post it to http://quadrevisionspot.blogspot.com/
If you want those transistors in your IRL-mailbox this week look @ http://stores.benl.ebay.be/DadaElectronics
Stefaan
Keith
Thanks for the answers I will consider them!
I'm undecided regarding R13 and C7 so for stability issues in mind I plan to leave them in place.
Stefaan
I personally haven't tried neither 2N3773 nor MJ15003. As far as I see in their specs they are pretty close, I read good reviews about both of them and presume that both are good transistors for this purpose, so probably it's a matter of taste wich one to choose. I think I will go with MJ15003 output and MLJ15031 for drivers.
If you have other experiences with them please write about them.
Andrew
Thanks! I have to check if they send to Romania.
Regards,
Zsolt
Thanks for the answers I will consider them!
I'm undecided regarding R13 and C7 so for stability issues in mind I plan to leave them in place.
Stefaan
I personally haven't tried neither 2N3773 nor MJ15003. As far as I see in their specs they are pretty close, I read good reviews about both of them and presume that both are good transistors for this purpose, so probably it's a matter of taste wich one to choose. I think I will go with MJ15003 output and MLJ15031 for drivers.
If you have other experiences with them please write about them.
Andrew
Thanks! I have to check if they send to Romania.
Regards,
Zsolt
Stolen Quad 405
Quad 405 S/N 13824 "disapeared" last month in France while being sent with Postal service.
The amplifier belongs to Frédéric Marçot (Frejus, France).
If you have any information about this amplifier send an e-mail to: info@dadaelectronics.eu
S.
Quad 405 S/N 13824 "disapeared" last month in France while being sent with Postal service.
The amplifier belongs to Frédéric Marçot (Frejus, France).
If you have any information about this amplifier send an e-mail to: info@dadaelectronics.eu
S.
Odd offset
Hi Guys
I have a clone 405 with boards from china, built they test left 0.03 ma and right 14.0 ma
I suspected the earths, and connections at both ends of R2 to stop potential voltage, all are connected and check out with 0v at the capacitors, input v is 50-0-50.
Any idears suggestions would be welcome, thanks
Hi Guys
I have a clone 405 with boards from china, built they test left 0.03 ma and right 14.0 ma
I suspected the earths, and connections at both ends of R2 to stop potential voltage, all are connected and check out with 0v at the capacitors, input v is 50-0-50.
Any idears suggestions would be welcome, thanks
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