Very nice! I remember using my Nitty Gritty Religiously back in the day. Before ever playing, carefully removing the record from the sleeve, precleaning with a Blue soft velour/felt pad (don't remember the name). Then the wetting process , bought the expensive fluids; then learned to make my own from a couple of recipes. Made it by the Gallon. Soaked the record with another soft foam brush. Then ran the Vacuum., one side at a time. I had the manual Nitty Gritty, which worked just fine. Before I ever played a record I LASTed it and put in custom,, soft, clear vinyl/rice paper sleeves I bought. to replace the crap paper sleeves record usually came in. And then carefully positioned a Golden Last sticker on the album cover. I would always clean the record before playing it. And of course always clean the stylus on my cartridge before playing. Ah the "Ceremonial Purifying Ritual of Listening to Vinyl"!
I bought a lot of record collections, some of which from an insurance auction, many of these I have never played. I decided to run two turntables. A direct drive that will be used for initial testing and a belt drive for those records that are in near perfect condition. I will draw up plans for a stand, plinth, and possibly a suspension system for that turntable, the other I will most likely keep in my shop.
The harmonics at 8kHz and 16kHz are artifacts, I think something is up with the ADC in my interface, they are present on loopback without the amplifier in the path. The amplifier can only take credit for the low order harmonics, I'll have to redo the measurements at some point once I've got the issue sorted out. The noise floor is also higher than expected. I've noticed some erratic behavior from the MOTU M4 lately, considering upgrading to the UltraLite-mk5.
Well I got the noise floor issue figured out, it was coming from my lovely mains power, now running everything off my laptop (except the amp obviously). Still not sure about the 8kHz and 16kHz artifacts.
The measurements are actually even better with the noise issue resolved, this is a very low distortion tube amp. Too bad about the 8kHz and 16kHz harmonics, the other harmonics are so low that the artifacts are actually making a significant contribution to THD. In the 32ohm spectrum, the 8th harmonic is highest!
More work to be done. Measurements are such a drag.
I came up with a solution to the 8kHz and 16kHz artifacts, I call it Microsoft Paint ADC patch. As you can now see, the harmonics are gone and the distortion is much improved.
Sorry I know measurements are boring, but one more just for fun - seeing how much power is available while keeping THD < 1% for 32ohm and 300ohm loads (closest I can get to 1% THD without going over using a stepped attenuator and adjusting the DAC output). These are obviously unlistenable volumes!
Those are some great measurements Keenan, congrats! Low noise, low distortion and great bandwidth for an OPT coupled amp!
For those 8 and 16 khz measurement artifacts, I get those as well with my Motu M4. I can't remember if it was changing the bit depth, sample rate, or just unplugging my laptop from mains that removed those artifacts for me. It may have also been a windows mixer issue that I'm not remembering how I solved.
Those are some great measurements Keenan, congrats! Low noise, low distortion and great bandwidth for an OPT coupled amp!
For those 8 and 16 khz measurement artifacts, I get those as well with my Motu M4. I can't remember if it was changing the bit depth, sample rate, or just unplugging my laptop from mains that removed those artifacts for me. It may have also been a windows mixer issue that I'm not remembering how I solved.
Thanks, Mischa! Good to know, let me mess around with some settings and see if I can get them to go away, I'll check it out tomorrow since I put away the measurement gear for the night, I will report back
The amp came back to me for a tune up before I send it to @Monsterzero . It got pretty banged up in transit going back and forth to the west coast, tip top now and ruggedized. It will be heading to him this weekend.
Zach kindly gifted me a Pelican case for shipping my amps around, so I can now ship with confidence, it is a beast (cat for scale). The postal workers thought I was shipping guns when I picked it up lol.
One perk of the amp coming back for a few days is I got to listen to these Fivre 6V6G, they sound awesome. Have some 6550 coming tomorrow, might try to give them a quick listen before I ship the amp.
The amp came back to me for a tune up before I send it to @Monsterzero . It got pretty banged up in transit going back and forth to the west coast, tip top now and ruggedized. It will be heading to him this weekend.
Zach kindly gifted me a Pelican case for shipping my amps around, so I can now ship with confidence, it is a beast (cat for scale). The postal workers thought I was shipping guns when I picked it up lol.
One perk of the amp coming back for a few days is I got to listen to these Fivre 6V6G, they sound awesome. Have some 6550 coming tomorrow, might try to give them a quick listen before I ship the amp.
Nice cat. I named my amps after some of my cats. When dealing with pedigreed cats you get a couple chances then the controlling bodies name your cats for you thus I used Latin. One of my cats was Incubus Elegans (elegant nightmare) and I used that for a headphone amp. I called him Gonzo after Gonzo journalism, think Hunter S Thompson. Life gets complicated.
The amp came back to me for a tune up before I send it to @Monsterzero . It got pretty banged up in transit going back and forth to the west coast, tip top now and ruggedized. It will be heading to him this weekend.
Zach kindly gifted me a Pelican case for shipping my amps around, so I can now ship with confidence, it is a beast (cat for scale). The postal workers thought I was shipping guns when I picked it up lol.
One perk of the amp coming back for a few days is I got to listen to these Fivre 6V6G, they sound awesome. Have some 6550 coming tomorrow, might try to give them a quick listen before I ship the amp.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
