For many of my projects I am a big fan of genuine Toshiba 2SC5200N (and complement 2SA1943N) for outputs and genuine Toshiba TTC004 and TTA004 drivers. I buy them from Mouser or Digikey because faked outputs and drivers really are a plague that can cause degradation and destruction of amplifiers. I also use genuine 2SC5171 (and complement 2SA1930) which I obtain from scrap receivers. I think the 2SC5171 (and complement) are really good but out of production. I also like genuine Sanken devices removed from scrap receivers (or from real distributors).
Now for the Quad I did not replace the drivers so I am a little hesitant to suggest such high gain (and frequency) Toshiba drivers because I don't want to cause you trouble. I don't want to recommend something that I have not tried. I wonder if anyone else out there has experience and data on which genuine current production drivers are the best choice for the Quad 405.
Now for the Quad I did not replace the drivers so I am a little hesitant to suggest such high gain (and frequency) Toshiba drivers because I don't want to cause you trouble. I don't want to recommend something that I have not tried. I wonder if anyone else out there has experience and data on which genuine current production drivers are the best choice for the Quad 405.
Do you think it may be worth using a c-r-c filter with the quad. I am thinking of soldering caps on the underside of the boards, underneath the 0.1uf caps next to the fuses.
Nelson pass uses crc filters in his amplifiers and from what I can gather, caps do not really reduce noise, they just shift the noise to a different / higher frequency that you cannot hear. Only the resistor in the crc filter can actually reduce noise. I have the 10,000uf caps in the power supply, then a 0.5 ohm resistor, then I can solder 2200uf caps on the underside of the amp boards. Do you think this may lead to a smoother DC and an improvement in audio quality
Several of my class A projects have a CRC power supply while none of the class AB projects do. [I guess the Quad is really Class C-ish?] I suppose if the second "C" in the CRC is large enough then the transient currents (and thus drop across the "R") should be ok.
Here is an old post where AndrewT discusses this:
https://www.diyaudio.com/community/threads/pi-filter-or-not.302374/post-4958224
In terms of the Quad 405 (clone) I think the most important upgrades are the gain modification, the op-amps, good output devices and then possibility the current limiters.
Also in addition to optimization of a single project I consider it important to compare to other well regarded projects. For example, I consider the Krell KSA-50 and Marantz MA-9S2 as very good examples to compare to. I do not know what you have built, but perhaps you might enjoy and benefit from comparing to a KSA-50 or MA-9S2 before (and/or after) upgrading the Quad 405? [So far I have built a number of "Douglas Self" type projects, the Quad 405 and then the KSA-50 and MA-9S2. (And a few others here and there such as MOSFET based Class A and a variety of chip amps.)]
My personal recommendation is that anyone who enjoys building project amplifiers should try a project involving building two KSA-50 mono-blocks (or two MA-9S2 mono-blocks). I used two huge scrap home theatre receivers (victims of HDMI failures and lead-free solder) as donors of the cases, large extruded aluminum heatsinks and large transformers.
A mono-block placed on the floor next to the speaker (with a 2-3 foot speaker cable) is a real improvement to consider. Especially based upon the KSA-50 or MA-9S2.
Here is an old post where AndrewT discusses this:
https://www.diyaudio.com/community/threads/pi-filter-or-not.302374/post-4958224
In terms of the Quad 405 (clone) I think the most important upgrades are the gain modification, the op-amps, good output devices and then possibility the current limiters.
Also in addition to optimization of a single project I consider it important to compare to other well regarded projects. For example, I consider the Krell KSA-50 and Marantz MA-9S2 as very good examples to compare to. I do not know what you have built, but perhaps you might enjoy and benefit from comparing to a KSA-50 or MA-9S2 before (and/or after) upgrading the Quad 405? [So far I have built a number of "Douglas Self" type projects, the Quad 405 and then the KSA-50 and MA-9S2. (And a few others here and there such as MOSFET based Class A and a variety of chip amps.)]
My personal recommendation is that anyone who enjoys building project amplifiers should try a project involving building two KSA-50 mono-blocks (or two MA-9S2 mono-blocks). I used two huge scrap home theatre receivers (victims of HDMI failures and lead-free solder) as donors of the cases, large extruded aluminum heatsinks and large transformers.
A mono-block placed on the floor next to the speaker (with a 2-3 foot speaker cable) is a real improvement to consider. Especially based upon the KSA-50 or MA-9S2.
Thanks! Very good ideas. Just want to get this quad project finished off before i move on to other projects. I do want to ask you, your amp board uses kd1047 and mine use 2sc5200, is mine the better board?
I did replace the stock 2sc5200 output transistors yesterday and noticed an immediate improvement in sound quality, so i think the transistors are fake. Now i need to replace the ka1049 driver transistors, i'm pretty sure these are fake as well. But what should i replace them with.
I did replace the stock 2sc5200 output transistors yesterday and noticed an immediate improvement in sound quality, so i think the transistors are fake. Now i need to replace the ka1049 driver transistors, i'm pretty sure these are fake as well. But what should i replace them with.
I believe you have the more recent board. I believe it is basically the same as my Quad 405 v2 except with better outputs and drivers. It is unfortunate if those "upgrades" turn out to be fake. Unfortunate but not surprising.
The D1047 do not have has good a SOA (Safe Operating Area) as a genuine 2SC5200. The 2SC5200 is a better transistor in several respects.
Can you confirm the model of the drivers? I thought the newer boards came with KTA1659A. Perhaps post a photo of the board and then a closeup of the drivers?
Is your op-amp the TL071 or TL081? (V2) Or the LM301? (V1/Original). I have the V2 which was TL071/81 but I upgraded that.
The D1047 do not have has good a SOA (Safe Operating Area) as a genuine 2SC5200. The 2SC5200 is a better transistor in several respects.
Can you confirm the model of the drivers? I thought the newer boards came with KTA1659A. Perhaps post a photo of the board and then a closeup of the drivers?
Is your op-amp the TL071 or TL081? (V2) Or the LM301? (V1/Original). I have the V2 which was TL071/81 but I upgraded that.
Did you complete the 405-2 project, if so did the amp sound good, what would you compare it against, the krell ?
I did complete the 405-2 but later disassembled the amplifier because I needed the chassis for testing other projects. My chassis currently have the KSA-50 (two mono-blocks) and the MA-9S2. The KSA-50 mono-blocks are my favorites and what I would recommend but I plan to do more work on the MA-9S2 in the next year or so. I plan to make bigger versions of the MA-9S2 and also make them mono-blocks. I tried the 405-2 out of curiosity since it was such an usual design. It sounded better than I was expecting especially with the speakers I was using (which have four mid-bass drivers) and dip down to about 3 Ohms. I certainly had fun on the project and listening to them. However the best that I can recommended (based upon what I have built so far) would be the KSA-50 and the MA-9S2. I think a well done KSA-50 or MA-9S2 would be considered quite a good amplifier. (Built with quality genuine transistors, proper solid/quality transformer/power supply, etc.)
Edit: So I am putting my effort into the MA-9S2 however I just read that there is a Quad707 clone out now. I don't know anything else about it but I wonder if the Quad experts can offer any insight into the 707 versus 405. Perhaps those interested in the 405 project might want to consider the 707? I have not looked into it but perhaps the Quad experts can chime in?
Edit: So I am putting my effort into the MA-9S2 however I just read that there is a Quad707 clone out now. I don't know anything else about it but I wonder if the Quad experts can offer any insight into the 707 versus 405. Perhaps those interested in the 405 project might want to consider the 707? I have not looked into it but perhaps the Quad experts can chime in?
Thanks! Yes, i already started a thread on the ljm 405 vs 607 vs 707, but can't get any replies, seems no one has done a comparison.
I accidentally blew up my quad 405 boards by soldering a cable in the wrong place, stupidly did not pay enough attention
Ljm himself said the 405 is better than the 707, but changed his mind later on. Here's the thread if you could take a look.
https://www.diyaudio.com/community/threads/quad-amplifier-boards.404949/#post-7495432
I built a small class-a amp in the mean time, and have ordered another pair of the china quad 405 boards today, so am waiting for them to come through, in a week or two.
Since i blew up my quad boards i never got to hear them and was wondring what you thought of them, if it is a project worth pursuing, I mean there’s a lot of boards out there, so am wondering if the quad 405 boards are worth the time, effort and expenditure, if the quad is a mediocre amp or if it holds any promise
I accidentally blew up my quad 405 boards by soldering a cable in the wrong place, stupidly did not pay enough attention
Ljm himself said the 405 is better than the 707, but changed his mind later on. Here's the thread if you could take a look.
https://www.diyaudio.com/community/threads/quad-amplifier-boards.404949/#post-7495432
I built a small class-a amp in the mean time, and have ordered another pair of the china quad 405 boards today, so am waiting for them to come through, in a week or two.
Since i blew up my quad boards i never got to hear them and was wondring what you thought of them, if it is a project worth pursuing, I mean there’s a lot of boards out there, so am wondering if the quad 405 boards are worth the time, effort and expenditure, if the quad is a mediocre amp or if it holds any promise
Now that I have built the KSA-50 and the MA-9S2 I would not go back to the 405.
I had two (large) "donor" home theatre chassis/extruded heatsinks/high current transformers that I turned into KSA-50 mono-blocks. I don't know what sort of space and chassis you have to work with. But if you build up your 405 and then later build a pair of KSA-50 mono-blocks I suspect that you will enjoy the project. I also suspect that you will go with the KSA-50 long term.
I had two (large) "donor" home theatre chassis/extruded heatsinks/high current transformers that I turned into KSA-50 mono-blocks. I don't know what sort of space and chassis you have to work with. But if you build up your 405 and then later build a pair of KSA-50 mono-blocks I suspect that you will enjoy the project. I also suspect that you will go with the KSA-50 long term.
Thanks! I would have a problem getting rid of the amount of heat a pair of ksa 50 boards would produce, how are you controlling all that heat
I contacted one of the clone ksa-50 sellers, and he said he could reduce the bias a little, what do you think of this approach, would it ruin the sound quality
I contacted one of the clone ksa-50 sellers, and he said he could reduce the bias a little, what do you think of this approach, would it ruin the sound quality
I would not reduce the bias. The donor home theatre chassis that I used came with large extruded heatsinks. (They were higher end home theatre receivers that had to be scrapped due to bad HDMI boards.) Since I made two mono-blocks the heat is quite manageable with one amplifier per chassis. The home theatre receivers were 7x140W originally and not with the lightweight sheet aluminum type heatsinks. Since the HDMI boards had failed they were almost free for a huge transformer and heatsink. (They also had a number of quality Toshiba transistors: Outputs, drivers and some TO-92.)
As for the heat we need all the heat we can get with the freezing temperatures.
As for the heat we need all the heat we can get with the freezing temperatures.
Thanks! Krell sound like a good amp manufacturer, are there any other good krell amps out there, perhaps with less heat production.
I built a pass labs F5 amp which is 25 watt/channel class a, and had to use 10kg heatsinks per channel. So i'm nervous about what kind of cooling a 50 watt/ channel amp would need
Also any chance you could please expand on your comments about the quad 405 boards, i purchased them and they should be arriving any day, but now i am not so sure whether to proceed with that project or ignore it and move straight onto the krell. What amp would you compare the quad against in terms of sound quality, just so i can get an idea in my head of roughly what i will be dealing with
Thanks
I built a pass labs F5 amp which is 25 watt/channel class a, and had to use 10kg heatsinks per channel. So i'm nervous about what kind of cooling a 50 watt/ channel amp would need
Also any chance you could please expand on your comments about the quad 405 boards, i purchased them and they should be arriving any day, but now i am not so sure whether to proceed with that project or ignore it and move straight onto the krell. What amp would you compare the quad against in terms of sound quality, just so i can get an idea in my head of roughly what i will be dealing with
Thanks
I would go straight to the KSA-50 and/or MA-9S2 if you want really good sound. I would personally skip over the others unless you are interested in learning and comparing. I have built all sorts of different kits and clones such as JLH, chip amps, many "blameless" types, QUAD405 (and mods), couple of Pass Labs clones, couple of Denon circuits, several Class-D, KSA-50, MA-9S2, several DIY Audio projects, etc. I personally have enjoying building, modifying, listening to, comparing, etc. But at this point I personally have settled on the KSA-50 and MA-9S2 and variants.
Thanks for the reply, much appreciated.
The quad 405-2 boards have arrived, think i might play about with them until the krell boards come through.
Made a mistake straight away, i ordered the boards from the same shop without looking at the photo properly, looks like i have been sent the old boards with the kd1047 output transistors and the driver transistor is tip42. Did a search and the tip42 is not a respected component.
Can you tell me there is a capacitor at the bottom left of the photo, what can i replace this with, a low esr cap like panasonic fm, or a signal path cap like elna silmic II
Above this cap is a diode then a yellow film cap, do you know what the value of this yellow cap is
The quad 405-2 boards have arrived, think i might play about with them until the krell boards come through.
Made a mistake straight away, i ordered the boards from the same shop without looking at the photo properly, looks like i have been sent the old boards with the kd1047 output transistors and the driver transistor is tip42. Did a search and the tip42 is not a respected component.
Can you tell me there is a capacitor at the bottom left of the photo, what can i replace this with, a low esr cap like panasonic fm, or a signal path cap like elna silmic II
Above this cap is a diode then a yellow film cap, do you know what the value of this yellow cap is
The two 100uF Rubycon capacitors are the main power supply bypasses.
I would leave the capacitor above the Zener diode alone. (It is 680 pF on my QUAD-405-2 LJM boards.) The QUAD405 isn't a typical or simple amplifier. Safe changes include bypasses for the Zener diode op-amp supplies, the gain change, op-amp change and perhaps for the slightly more advanced disabling or changing the current limiters.
Perhaps consider limiting yourself to the Zener diode op-amp supplies, the gain change and op-amp change after thoroughly studying the sites/links dedicated to the QUAD-405-2.
However I suggest that you don't change anything until you have built up the amp carefully and have listened for a month or so. Perhaps build up the QUAD-405-2 and the KSA-50 and listen to (and compare) both for a month or two and then decide on which you want to keep.
I don't know what exact boards you have since my "LJM QUAD-405-2 2004-2018" are labeled with 1659A not TIP42 in silk screen. Mine came with KTA1659A not TIP42.
I would leave the capacitor above the Zener diode alone. (It is 680 pF on my QUAD-405-2 LJM boards.) The QUAD405 isn't a typical or simple amplifier. Safe changes include bypasses for the Zener diode op-amp supplies, the gain change, op-amp change and perhaps for the slightly more advanced disabling or changing the current limiters.
Perhaps consider limiting yourself to the Zener diode op-amp supplies, the gain change and op-amp change after thoroughly studying the sites/links dedicated to the QUAD-405-2.
However I suggest that you don't change anything until you have built up the amp carefully and have listened for a month or so. Perhaps build up the QUAD-405-2 and the KSA-50 and listen to (and compare) both for a month or two and then decide on which you want to keep.
I don't know what exact boards you have since my "LJM QUAD-405-2 2004-2018" are labeled with 1659A not TIP42 in silk screen. Mine came with KTA1659A not TIP42.
Thanks! What do you think is a good value for these two rubycon caps. I remember you changed the upper rubycon cap to 33uf.
On another thread someone changed it for 33uf polypropylene, saying he wanted to keep film caps in the signal pathway - but i can't remember if that was a 405 or 405-2 board
On another thread someone changed it for 33uf polypropylene, saying he wanted to keep film caps in the signal pathway - but i can't remember if that was a 405 or 405-2 board
Ok. I made a mistake in my last post. This board does not have Vcc bypass capacitors which I why I added them in the photos of my board.
Sorry for the mix-up. The capacitor that I change to a green 33uF Nichcon MUSE BP (Bipolar) is part of the op-amp circuit. It would be best that you lookup the gain modification for the values for the gain modification. I assume you will want to do that considering modern input levels. When you lookup the gain modifications you should also find the schematics.
However again I suggest that you don't change anything until you have listened to it for a few weeks. Just a suggestion. I would build up both the 405 and the KSA50 and listen back and forth in the stock configuration first.
Sorry for the mix-up. The capacitor that I change to a green 33uF Nichcon MUSE BP (Bipolar) is part of the op-amp circuit. It would be best that you lookup the gain modification for the values for the gain modification. I assume you will want to do that considering modern input levels. When you lookup the gain modifications you should also find the schematics.
However again I suggest that you don't change anything until you have listened to it for a few weeks. Just a suggestion. I would build up both the 405 and the KSA50 and listen back and forth in the stock configuration first.
Thanks! I will follow your instructions and not make any changes.
Please to allow me to pick your brain for another moment: from the photos you uploaded on page one, it lools like you have taken out all of the 0.1uf orange film caps, can i do the same and replace with 0.15uf ceramic
You have placed 10uf caps on the back of the board for the opamp, is this across the 47NF cap which is on the side of the opamp and the 0.1uf just above the opamp
If so then the 47nf cap has now become 10.047NF, so no need to increase the 47hf to 147nf as you have described one page one ?
Please to allow me to pick your brain for another moment: from the photos you uploaded on page one, it lools like you have taken out all of the 0.1uf orange film caps, can i do the same and replace with 0.15uf ceramic
You have placed 10uf caps on the back of the board for the opamp, is this across the 47NF cap which is on the side of the opamp and the 0.1uf just above the opamp
If so then the 47nf cap has now become 10.047NF, so no need to increase the 47hf to 147nf as you have described one page one ?
So there are several different things going on:
1. The simpler issue is replacing existing capacitors with better ones that are on-hand. If it is a 100nF or 0.1uF bypass on a supply then I would use a good quality 100nF or 0.1uF polypropylene as a replacement. WIMA is considered a very good choice. I often don't have any extras left around so sometimes I have used lesser but still polypro models.
2. The op-amp has zener supplies but no bypass capacitors. So I added 47uF Panasonic M and 0.47uF polypro capacitors as bypasses. Pana FM are even better and WIMA would be great too. If one has the money and this is a priority hobby then it is sometimes nice to pick the best components. 10uF and 0.1uF might be perfectly ok too.
3. The gain change where I modified the resistors and scaled the capacitor in the signal path. For this I would refer you to the sites dedicated to the 405 modifications for explanation and details.
I tend not to use ceramic capacitors due to piezo electric effects, voltage coefficients, etc. Polypro is much better and affordable.
Also my board arrived with the lesser quality yellow film caps but the better driver transistors. I suspect your orange film capacitors are better than the yellow caps. Perhaps different vintage boards or clones of clones?
1. The simpler issue is replacing existing capacitors with better ones that are on-hand. If it is a 100nF or 0.1uF bypass on a supply then I would use a good quality 100nF or 0.1uF polypropylene as a replacement. WIMA is considered a very good choice. I often don't have any extras left around so sometimes I have used lesser but still polypro models.
2. The op-amp has zener supplies but no bypass capacitors. So I added 47uF Panasonic M and 0.47uF polypro capacitors as bypasses. Pana FM are even better and WIMA would be great too. If one has the money and this is a priority hobby then it is sometimes nice to pick the best components. 10uF and 0.1uF might be perfectly ok too.
3. The gain change where I modified the resistors and scaled the capacitor in the signal path. For this I would refer you to the sites dedicated to the 405 modifications for explanation and details.
I tend not to use ceramic capacitors due to piezo electric effects, voltage coefficients, etc. Polypro is much better and affordable.
Also my board arrived with the lesser quality yellow film caps but the better driver transistors. I suspect your orange film capacitors are better than the yellow caps. Perhaps different vintage boards or clones of clones?
Thanks! What got me confused is that on page one you said : " The TL071 operational amplifier is powered from 3.3k Ohm resistors and 15V Zener diodes which are bypassed by 0.1uF film capacitors. I am thinking of adding 10uF Panasonic electrolytics or 10uF Monolithic ceramic capacitors under the 0.1uF. "
Can you please tell me where you finally decide to put the 47uf panasonics, is it across the 47nf cap on the side of the opamp, and across the 0.1uf just above the opamp, or is this wrong.
Can you please tell me where you finally decide to put the 47uf panasonics, is it across the 47nf cap on the side of the opamp, and across the 0.1uf just above the opamp, or is this wrong.