luvdunhill

another interesting preamp design: Detailed write-up at: The Difference Engine Preamp Version 1.0 Exploring a 'secret' circuit called a differential. Article By Grey Rollins

meh. My Teclast T50 plays FLAC and is 1/1000th the size

Your Freight Total $5.65

no, they saw that it could hold a camera and accessories and assumed it would be that big.

Assuming a normal attenuation curve, which was what I wasn't sure about.

yes, their packaging is how do you say..... copious. Try ordering about 50 values of Dale resistors, and see what you end up with Last few times I've ordered stuff from Farnell via Newark, and they have payed shipping on this side of the pond for me (well, I payed that $15 surcharge I suppose). This time I selected USPS Priority, and I haven't gotten this shipping amount yet.

Newark is a strange beast. They care a nice intersection of Digikey and Mouser parts. The strange thing is, there are always "sale" items that are marked with a P. They isn't much rhyme or reason to it, for example the 1.00K resistors of a certain line may be heavily discounted, or a cable gland for a large multipart Amphenol assembly. I've never seen "sale" items at Mouser or Digikey... The neon lamps are a little trick I'm playing with to help ease the large turn on voltage that tubes see on start due to plate CCSes.. the idea is if you have two tubes connected together, and the first tube has a plate CCS, if it is not warmed up, all the current is forced into the second tubes grid until the first tube warms up... the bulb is placed across the grid / cathode of the second tube. It seems to work pretty well, the neon bulb is on at start-up then turns off as the plate CCS comes up. I'm going to try and play with a few different strike voltages and see if I can optimize things some more.

parts at Newark using 25% coupon (as if anyone cares really): NATIONAL SEMICONDUCTOR LM317HVT/NOPB NATIONAL SEMICONDUCTOR LM329DZ/NOPB VISHAY GENERAL SEMICONDUCTOR 1N4001GP-E3/1 VISHAY SEMICONDUCTOR 1N4733A-TR CADDOCK MK132V-200K-1% AVAGO TECHNOLOGIES HLMP-D150 3M 929952-10 Jumper FAIRCHILD SEMICONDUCTOR TIP50 MULTICOMP MC08030000 Neon Lamp; MULTICOMP MC08020000 Neon Lamp; MULTICOMP MC08310015 Neon Lamp; BOURNS 3296W-1-501LF VISHAY BC COMPONENTS 5093NW22K00J VISHAY BC COMPONENTS 5093NW18K00J VISHAY BC COMPONENTS 5093NW16K00J VISHAY BC COMPONENTS 5093NW20K00J

cool! how does the left/right matching work, or do you mean it has better channel matching than most DAPs? and is there some sort of gain switch?

I'd recommend cryoing the clay first to realign the structures

I don't know if you guys ever buy from this guy, but he has some in stock: MachMat tube sales There's also a local guy in Austin that often has them, if you're really interested edit: heh, here he is in fact. Strange guy... http://www.diyaudio.com/forums/showthread.php?threadid=130519

I like the way you went with that. The other way was just too plebeian.

They are at the same place you got your variac

Hey Ray, why don't you give this a try and see if you can copy the Blue Hawaii with your A-10 http://www.carveraudio.com/CarverChallenge.pdf

Just noticed some Japanese ASCs go up for sale, and started wondering what you ever decided to do with your upgrades?

Thank god there are other devices available now that weren't produced 45 years ago.

hey no fair, you edited your post and it changed my quoted portion of your post

not really luck, just buy 500 of them.. also, most system problems are easily alleviated with a simple buffer, if you have to be able to support every possible equipment chain out there...

Depends how close you match the devices. 0.5dB is pretty normal, and 0.1dB is definitely possible for stereo operation. Attenuation, take your pick, -70dB is a reasonable amount.

I don't see why they wouldn't fit, the optos are around 6mm by 5mm or so. All you need other than that is a crappy pot, so a thumbwheel would work great, since it's not in the signal path. That's what I'd do at least. As for current draw, it's no different than powering a few LEDs... shrug. Same thing as the volume control in the higher end Melos amps of old, I'm surprised you haven't heard of it before.

I have received all the parts for the two prototype boards, just waiting on the board themselves from Jacob. I have received all of the small device heat sinks from Hong Kong as of yesterday. In other news, I may pass on the group buy for the passive parts. I have a very large order to place to Parts Connexion and will go ahead and order a bunch of the parts then and just match them myself. I'm hoping to have time this weekend to work on my case. I had a chance to cut the aluminum angle brackets and mark the holes on the heat sinks already. With this much heat, we need to pay close attention to the thermal junctions, hence I'm looking into various types of isolators and grease. I think I have a very workable solution and will be testing it soon in another design. I'm hoping to get a 5-6 degree temperature drop, which is pretty significant. Stay tuned, we're getting oh so close.

Justin, glad you solved this one Why did you decide against using the Silonex LDRs, with a thumb wheel pot, for example? Very compact and not "digital" and sounds fantastic.

nah, I'm using it for a preamp. CLC to get 400V then a HV regulator (http://www.national.com/an/LB/LB-47.pdf) to get down to 350V. 6SN7 as a single gain stage and a ECC99 as a phase splitter on the output. Transformer input and AC coupled output (gasp!). Fully balanced stereo preamp only using two tubes

There's a lot you can do with 400 VDC .. but maybe I'm using a voltage doubler