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Hello RossW, Thank you for your reply. I certainly can't hear any difference with the new part in and didn't expect to. It's the only 100ppm resistor now in the amp, out of boredom during Covid lock down I have replaced practically every component on the amplifier boards with high spec...

Hello All, If I have two standard through hole metalfilm resistors of the same resistance, the first rated 50ppm at 250mW and the second rated 100ppm at 1W, both operating at the same temp. Is my understanding correct that both these resistors will suffer resistance drift at their specified...

Hello mbz, vsat88 & rickl, Thanks for your replies. I'm basically happy with the NJM2068DD opamp and will stick with it, but had mbz actually of compared it to OPA2134 I might have been tempted to try.

Hello mbz, Before changing from LM4562 to OPA2134 in the tone circuit did you try the NJM2068DD opamp as recommended by Leestereo? I'd be open to trying OPA2134, but would like to know what your thoughts were about the opamp I'm currently using NJM2068DD? Thanks

Hello zaskarx, The Quad I'm using is a 405-2 and it has been modified so its sensitivity is now 1.5v (C4 is 150nf, R4 6.8k and R6 100k), the speakers are 89db. The sensitivities of these two should match perfectly and that's why I'm surprised by the results.

Hello vsat88 & rickl, Yes the schematic above is the correct one featuring resistors 41/42 I'm interested in. Thanks for your replies.

Hello All, Having done the mods to my C1, I have recently paired it with my modded Quad 405-2, this amp has a sensitivity of 1.5v, but when using it with the C1 the volume is just too high when the volume knob of the C1 is at the 9 O'clock position. It's unusable the beyond 9 O'clock. R41/R42...

It's done! At last! I've really struggled to find the time to do this little project, the longest time I've put in is two hours in any session, but it's done now. The original: Disassembly & Soldering: It was problematic not being able to disconnect those wires from their binding posts...

I'll try the diagram method, it looks more professional than my method.

I've ordered those Philips polypropylene caps, I did some research they are 10mm x 4mm approx, they will have to stand off away from the circuit board, the board lead spacing is about 3.5mm and so the leads will form a V shape. It will look a bit strange but should be do-able. Thanks for...

Hello Leestereo, Thanks for your prompt reply, For C3/C4 I am not sure if the caps below are COG or X7R dialectrics, are COGs definitely required...

Hello Leestereo, I've 99% completed this upgrade except for a few components that look different to your C1. In the Phono stage/EQ amp, the two little brown ceramic capacitors (100pf) C1 and C2 are not present in my preamp, the holes are there along with their names and on the copper side...

Hello BinaryMike, To use you name, I wish this was a binary decision, a simple 1 or 0. I really like this little amp and want to set it up for a long period of ownership, as Powertech has indicated what's up stream of the big caps is only stressed momentarily and then little sips are taken by...

Hello Powertech, The pro's and con's were laid clearly out in your excellent and concise post, thank you. I was looking at these two capacitors: TDK/EPCOS B41560 series 15000uf, 63V :::: Ripple (Amps max temp) : 9.1 ---- ESR(max...

Hello ConradH, As I said to Lavane, I suspect these specs of the stock caps were probably closer to the modern standard than the past, I'd like just a little bit more certainty. The caps from the picture above certainly look like a modern type. Thanks for your post, Rob

Hello I LIKE MUSIC, There's actually a lot of Quad 405s out there with 22,000uf caps in them, but they all seem to be (2 x 405) mono setups with just a one channel amplifier board inside instead of two in each amp. Having said that, in these mono setups wouldn't these caps be stressing the...

Hello Lavane, I've had a look for the specs, but can't find them anywhere, the service manual just indicates 10kuf, if they were -50%/+100% that would solve a lot of my problems. The stock cap were: STC 10,000UF 63V, CT 501 063, Q04 ASS, 8511 all record of them has disapeared. The Quad amp...

Hello All, I have a Quad 405-2 amp and I am about to do a major upgrade on this amp with new smoothing caps and optimisations to the amplifier boards. The amp currently has two stock 10,000uf smoothing caps, but many replace them with 15,000uf with no need to make any further mods to cope with...

Hello all, I've been a bit busy with things away from the this C1 project, but I've done all the soldering except for D3,D8 and Q1 which I took a out and tested and I wasn't happy with Q1 and also D8 was borderline. I didn't bother putting them back in, so now it's still in bits waiting for...

I haven't desoldered any of the pin/coiled wire arrangement and have been ok soldering 'as is', it just looked a bit awkward turning the boards over with wires attached. The new soldering station arrived and it's better that the old iron, I've completed the power supply section except for...

Hello, A quick update to where I'm at with this C1 upgrade. I've got all the components, I've taken the C1 apart and was about to get started when I discovered my soldering iron is not regulating properly, It's either stone cold or sizzling hot. Being a cheapo type and a good few years old, I...

rjsalvi & leestereo, Many thanks for your help in pointing me to to these components and the specs. Leestereo, I've checked the soldering on R62 and you were correct, it's very definitely stock. It was simply the colour difference that aroused my suspicions, all those big resistors seemed to...

D8: 0.74v & OL D3: 0.62 & OL Transistor behaved normally, but when reverse biased, with the base/collector it gave a voltage. All of the components were still soldered to the pcb, how will this affect readings? Also the soldering on D3,D4 and D5 looks very poor quality, the all have readings...

I've received all the components last week from Mouser, but the kids have been off school with mid term holiday/vacation and I've have had no peace or quiet until today, they've gone back to school. However, when looking at the C1 before starting I've noticed a replacement resistor has been...

The beer fest I went to the night before probably didn't help things either, I wasn't the sharpest knife in the rack that day. Let's hope there's plenty of plates full of fish!