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krell ksa5 klone


kevin gilmore

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Hi. Just completed my own set of PCB for this amp, see pictures. I also took detailed measurements.
KSA5 Power SupplyKSA5 Amp PCB

KSA5-Noise Floor_ STD Supply_into 16 ohms.jpg

Here some measurements:

Sensitivity: 1.25Vin max, for 6.9Vac Out Max. into 8 ohms
Power: 5.95W into 8 ohms max.
BW (Ref 1Khz, 1V): 0.3Hz to 145Khz
Noise (gnd input): 0.08mV (Lab. power supply), 2.2mv (Standard Supply), see graph
THD (1V, see load): 0.042% (8 ohms), 0.007% (16 ohms), 0.008% (no load), see graph
IMD (1V, 1 & 2Khz): 0.007% (16 ohms)

In normal use, max volume, gnd inputs, no noise can be hear...

 

You can see the complete files at http://www.diyaudio.com/forums/headphone-systems/109618-krell-ksa5-9.html

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  • 1 month later...

this is a customizable bass mid and high level control with optional pre-amp with jumper up to +4 db at the signal way with the Motorola 33079.
A very good preamp. All Sound change components are removed in the signal away everything runs through. I use a very good epcos for the bass adjustment and a very fine old ERO for the tips.

here the circuit board.

 

DSCN2388.jpg

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  • 2 months later...

Pars. PSU is running @ 23.2 V DC. Transformer is 27.5 V AC.

I no not mean opamps in the PSU. as i already know that they either work or or not work. I think you told me that previously ;-) so i changed the op27 to the cheaper op07 and the psu seems fine.

I have heard Operational amplifier have their own sound charecteristics or signature, therefore looking if changing OPAMPS in the amplifier will "improve" or change anything. I have testes the op27 and OPA 445 i find the forst one less precise with to much lows.

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If they are DC servos, then no, they will not change the sound signature if the servo is implemented correctly. But as long as the opamps you are trying can handle the voltage requirements, who knows? The opamp in question is probably implemented with dual supplies. Most opamps seem to be rated for +/- 18V. The OP27 is higher (don’t recall what exactly) and the OPA445 higher yet (quite a bit). If the offset is low and stable, you could try it without the opamp(s) in place. I don’t have a copy of the Krell schematic though, so can’t say for sure.


Sent from my iPhone using Tapatalk

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I am still testing. Yesterday my burson v5i s opamp arrived, they still need to run for a dozen of hours for the final test, however as of now I can tell that they bring much more improvement in my DAC (DIY based on ESS9028) than in my preamp (that is the the KSA5).
The idea of "upgrading" the opamps in the KSA5 came after i received counterfeit OP27 from ebay: the sound was terrible with lots of noise. Once i replaced them with Analog Devices original OP27G from Mouser, the KSA5 started to sound great, and then with BurrBrown's OPA445 even better IMHO, as i find it sounding natural.

I also think about replacing my nichcons KA with KG, not sure what it will change, or if it will change anything though.

Building, replacing, testing is an activity i really enjoy, that relaxes me a lot after a hard day at work. I should have chosen electronics instead of economics for my studies ;-) my lack of knowledge is a serious limiter for me, but you gentlemen and a great support and help. thank you!

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