WAD HD-83 headphone amp
Feb 9, 2010 21:36:48 GMT
Post by PinkFloyd on Feb 9, 2010 21:36:48 GMT
Well, that slight hum was back again and I've being going NUTS trying to find out what was causing it It turns out that it was the stock chassis mount phono sockets making contact with the metal enclosure (or one of them)..... the insulating washers that were fitted weren't the "through hole" type so the phono socket was actually touching the enclosure.
I drilled out larger holes and fitted the better type of phono socket (with through hole insulating washers) fired the amp up and, voila!, it's as quiet as a mouse So happy I found out what was causing it.
I've also been experimenting with shunt V non shunt V stepped attenuator and decided to go with the stepped attenuator (I had one kicking about in a drawer).... I felt the resistors used on the shunted pot added their own "flavour" to the sound (it was nice but slightly coloured with an emphasis on "warm") The ALPS pot on it's own sounded more open and the stepped attenuator sounds extremely well balanced and open.
The pot that was in the amp was a 100K type and I believe, from looking at the manual, that it should have been a 50K type. The stepped attenuator I have fitted is a 50K type so whether this has anything to do with it sounding more open than the 100K ALPS pot I don't know.... I am certainly keeping the stepped attenuator on board though and will be ordering up a better quality one shortly.
I still have to tidy the wiring up a bit (nothing wrong with it as is but it could "look" a bit neater) and sort out a nice knob.... I've got this guy on for the time being but want something a bit bigger....
The SQ is sublime, no other word for it, I rolled in a fresh pair of Mullard ECL83 (circa 1969 in original packaging / never touched by human hand) and this amp is singing one VERY sweet tune.... it's big, it's ballsy, it's expansive..... it recreates music in a large, majestic way and it has such low end GRUNT.... I won't be tampering with "parts", the hood's being bolted down as soon as I tidy the wiring up.
Maybe I got lucky first time with the Allen Bradleys, the EPCOS caps, the Rifa 426 / mullard mustards etc..... I don't know...... one thing's for sure, I'm not changing the recipe.... way too easy to over egg your pudding and I am over the moon with what I hear so that's good enough for me. She's set up for 300 ohm 'phones and absolutely perfect with the Senn HD-250 linears so I'll keep it that way until such time I feel the urge to listen to 32 ohm 'phones through her. (32 - 300 sounds fine with it's present set up anyway)
It's been fun to work on and I hope, in time, it will become my reference amp once I get to know it more intimately. An absolute BARGAIN secondhand (if you can find them) and highly tweakable to your own preferences. Highly recommended to anyone looking for top quality sound at a reasonable price (believe me, it blows all the £500 - £1,000 commercial headphone amps into the dust) and hours of fun to be had if you're into DIY / tweaking.
I drilled out larger holes and fitted the better type of phono socket (with through hole insulating washers) fired the amp up and, voila!, it's as quiet as a mouse So happy I found out what was causing it.
I've also been experimenting with shunt V non shunt V stepped attenuator and decided to go with the stepped attenuator (I had one kicking about in a drawer).... I felt the resistors used on the shunted pot added their own "flavour" to the sound (it was nice but slightly coloured with an emphasis on "warm") The ALPS pot on it's own sounded more open and the stepped attenuator sounds extremely well balanced and open.
The pot that was in the amp was a 100K type and I believe, from looking at the manual, that it should have been a 50K type. The stepped attenuator I have fitted is a 50K type so whether this has anything to do with it sounding more open than the 100K ALPS pot I don't know.... I am certainly keeping the stepped attenuator on board though and will be ordering up a better quality one shortly.
I still have to tidy the wiring up a bit (nothing wrong with it as is but it could "look" a bit neater) and sort out a nice knob.... I've got this guy on for the time being but want something a bit bigger....
The SQ is sublime, no other word for it, I rolled in a fresh pair of Mullard ECL83 (circa 1969 in original packaging / never touched by human hand) and this amp is singing one VERY sweet tune.... it's big, it's ballsy, it's expansive..... it recreates music in a large, majestic way and it has such low end GRUNT.... I won't be tampering with "parts", the hood's being bolted down as soon as I tidy the wiring up.
Maybe I got lucky first time with the Allen Bradleys, the EPCOS caps, the Rifa 426 / mullard mustards etc..... I don't know...... one thing's for sure, I'm not changing the recipe.... way too easy to over egg your pudding and I am over the moon with what I hear so that's good enough for me. She's set up for 300 ohm 'phones and absolutely perfect with the Senn HD-250 linears so I'll keep it that way until such time I feel the urge to listen to 32 ohm 'phones through her. (32 - 300 sounds fine with it's present set up anyway)
It's been fun to work on and I hope, in time, it will become my reference amp once I get to know it more intimately. An absolute BARGAIN secondhand (if you can find them) and highly tweakable to your own preferences. Highly recommended to anyone looking for top quality sound at a reasonable price (believe me, it blows all the £500 - £1,000 commercial headphone amps into the dust) and hours of fun to be had if you're into DIY / tweaking.