KISS
- karatestu
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Re: KISS
I think my next foray into the discarding of components will be trying a home made passive pre. I do love Les'821A preamp boards but there are two dc blocking, phase altering caps on there. My Cdp has no dc output and i assume the phono 1 has none either so i will be ok just putting a volume pot in. Martin T did say when removing the input coupling cap on my power amp that dc may get back to the vol pot and make it noisy. Dont know about that unless i give it a go.
Stu
Stu
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- Dr Bunsen Honeydew
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- karatestu
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Re: KISS
Thanks for the link Doc.
Which one should i go for ?
I presume i need a 10k, mono or stereo (2x mono for a balance control) , shunt version with tantalum resistors. I think i should avoid the ladder types and smd resistors ?
Stu
Which one should i go for ?
I presume i need a 10k, mono or stereo (2x mono for a balance control) , shunt version with tantalum resistors. I think i should avoid the ladder types and smd resistors ?
Stu
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Re: KISS
Stu, great that you are about to start this passive preamp project!
The Doc is clearly the expert on passive preamps, so the following are just my humble thoughts / two cents as someone who loves to DIY a bit:
It's funny, I finished a little DIY passive pre last weekend with two switchable input pairs and one output pair as I had some spare parts laying around. I used an Alps blue stereo pot 10K linear, some good quality RCA sockets, a 2-pole silver contact switch and some silver solid core wire and built everything into an open chassis out of plywood. And I like the results a lot (maybe because I built it? ). This little pre has detail, bass, nice mids and a sweet top end.
Maybe one day, I will go for one of the quality NVA pre's Richard builds, to get the best out of my system!
The Doc is clearly the expert on passive preamps, so the following are just my humble thoughts / two cents as someone who loves to DIY a bit:
It's funny, I finished a little DIY passive pre last weekend with two switchable input pairs and one output pair as I had some spare parts laying around. I used an Alps blue stereo pot 10K linear, some good quality RCA sockets, a 2-pole silver contact switch and some silver solid core wire and built everything into an open chassis out of plywood. And I like the results a lot (maybe because I built it? ). This little pre has detail, bass, nice mids and a sweet top end.
Maybe one day, I will go for one of the quality NVA pre's Richard builds, to get the best out of my system!
Norbert
Tubes and Vinyl rule, Music rocks!
Tubes and Vinyl rule, Music rocks!
- Dr Bunsen Honeydew
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Re: KISS
You choose, more expensive better, he builds them, he doesn't do bad ones. Lots of bad ones on ebay, surface mount ones are crap.
- karatestu
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Re: KISS
Cheers Doc. There are some really expensive ones. I will have to give them a good look. Tantalum resistors seem to be good. You can even use charcroft z foils for the series resistor.
Naim used alps pots, maybe still do. I have a noble pot at the moment but its 50k and no good for a passive .
Naim used alps pots, maybe still do. I have a noble pot at the moment but its 50k and no good for a passive .
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Re: KISS
For "YUK!" it sounds astonishingly good I have to say. And the good thing is, to swap the poti for a better one is a quite easy task...
Norbert
Tubes and Vinyl rule, Music rocks!
Tubes and Vinyl rule, Music rocks!
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Re: KISS
Hello Stu.karatestu wrote: ↑Sat Feb 17, 2018 7:56 am
Hey Alfi how's it hangin',
What you need to do is this;
Remove input stage coupling capacitor
Remove wiring between zobel and cap bank 0V
Remove wiring between output spade and positive output on back of amp
Solder a wire from the big pcb area where the ballast resistors (0R22) are joined to the output inductor, to the positive speaker output on back of amp.
There are a few unused holes in the pcb in this plane which were put on to accommodate different component sizes. Use one of those.
This will improve the sound considerably. I found the result to be more satisfying than giving the front end its own regulated power supply. I cant wait to combine the two modifications
But none of this will fully remove the "rip" as Les calls it. To do that you need to convert the board to a fully complimentary output stage. Remove the baxendall diode and a resistor, change the value of 6 resistors and swap the output transistor on the negative side to a pnp.
When i have found out the exact details and tested it myself you can just send me the amp modules and i will do it for you - free of charge of course
Stu
All fine here Sir, thankyou!
That's a very kind offer and one I will repay by carrying out the work on your LP12 gratis when the time comes.
Best wishes.
Alfi.
I am in the hi-fi trade.
Status: Manufacturer.
Company Name: Analogue innovation.
Contact: a_innovation@btinternet.com