Oatley has continued to improve their headphone amp\preamp
with the release of the K272C. I had something to do with this progression consulting
directly with Oatley. In fact there was a K272B between the K272A and the “C”. Here
are two K272C headphone amps, assembled from the new kits which sell for $40
from Oatley.
The improvements over the original K272 are:
- · 18V working
- · Separate filament and B+ batteries
- · Filament and B+ battery health LED indicators
- · OPA2134 driver chip
The kits are very easy to assemble with the excellent PCBs
being screen printed and solder masked with through hole plated. The sound has
improved with better bass response.
In this build I Al lined the ABS compact enclosures and used
switched 6.5 stereo phone jacks. Only with both source and headphone plugs
inserted and the press button switched “on” at the rear will power flow.
Wire-wrap wire has been used in the signal path and the battery health LEDs
have been brought out to the front of the enclosure. The sound appears to have
better bass than previous models but the tubes will ring if struck.
1 comment:
Hello, this is a very nice kit indeed (I have de K272B). Based on the K272C circuits, I made some alterations that might be worthwhile to test ( I am only a hobbyist and despite my ears and a multimeter do not have more adequate equipment or knowledge to test the real audio performance). The alterations was :
1) Changed de JAN 6418 for 1ZH18B (Soviet minitubes);
2) Changed C1 and C2 for 470nf PIO caps (also Soviets);
3) Excluded C4 and C5;
4) Instead of OPA 2134 I used the OPA 2107 (was on hand);
5) The rest was only minor alterations (power supply, etc);
Best Wishes,
Roberval
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