luvdunhill

Jacob et al. One thing to think with regard to the attenuator will be the input transformer. The input transformer has needs to help inform the circuit, or it will turn out to be a problem. That being said, I don't think a Joshua Tree type attenuator is a good choice, due to varying impedance. The choice of RC loading the secondary, plus the impedance of the volume control mechanism after the transformer will have to be chosen carefully. These interact with the input capacitance of the amp, as well as any input filter or feedback capacitance. My experience with input transformers is mostly with the Jensens. Does anyone else have an opinion on this?

14 pairs, so 28 transformers? The price breaks are: 1-11 = 0% 12-24 = 10% 25+ = 15% 50+ = 20% 100+ = 25% (Maximum discount)

So, latest cost on these is right around $150 a pair. If we get up to 12.5 pairs, it goes down by a whopping 5%. I'm in for 2 pair.

It's a slight mechanical hum, not EMI. Doesn't effect sound really that I can tell.

That Grado reminds me of the tone arm reminds me of the Gray viscous damped arms:

with regards to Pars post in the business thread, I'd definitely go with the larger transformer and go with the same transformer for all builds. I'd recommend 160VA 2x30 VAC with universal primaries. Again, reference Plitron 057017201. With regard to SumR, they are a bit of an unknown. The ones I have seem to have a bit of mechanical noise, but perform okay. Plitron is pretty much the industry standard in audio. I just wanted to throw this out to the crowd, and maybe those who have an opinion on this matter can give their $0.02. This is pretty much a no-compromise type of build and from what I've seen so far, this is the only already I'd consider a slight compromise, just because of the unknown-factor. ... gotta run for a bit, I'll comment more on the other thread later..

Will you use another transformer (PCB mount?), or perhaps an external wall-wart to power this circuitry? Sounds good, but I wouldn't really want to tap the main toroid for this.

don't forget that the input transformer likes to see a certain load after it. Please add a resistor in series with a capacitor after the input transformer so the loading can be adjusted.

Agreed. I think this the best way to go forward. I'd like to handle the Sowter group buy as well, as I need 4 input transformers just for myself. I have worked out a custom version from them that should be amenable to everyone. I'm also planning on offering this to builders of another project at DiyA as well. AMB will sell matched transistors for the sigma22 boards. You may also consider working a deal out with Jeff at glassjaraudio for some discounts. I think this route would be easiest, as there are a lot of parts to kit. There is pretty much no way I can do this for everything. I can and have for the Toshiba JFETs, but that's about all I can do. I'll have to wait for money before I can order the small heat sinks and the small signal BJTs and the output devices. I can also do a build for someone as well. I'd prefer a balanced build. That sounds reasonable. sounds like a good way to cut costs! One other option is to order heat sinks from Conrad that have already been milled and tapped. Then you're just looking at the top and bottom, which can be cut easily and the front and rear custom panels. In this case, things are very easy to assemble and will be cost effective as all that is shipped from overseas is the heat sinks. I've worked with R-Theta as well, as since they are closer, they may offer us a better deal. In the case we're interested in Conrad, I have a contact there that has done this exact thing in the past and we may be able to use previous drawings. The final product, including shipping in the US to the final destination was under $100 a pair. Spritzer has a pair of these heat sinks, they are extremely nice. Just another option, one I think would be the cheapest, assuming your brother can cut the top and the base plate and do the machining on the angle brackets. $150 is low. I'd say $300 is spot on. Thanks for your work guys, sorry I was AWOL... I was out fighting crime and all that stuff...

Do any of them use DF1704 as well?

excellent thoughts guys. I guess we're still waiting on firm numbers. I can live with that.

I agree. However, it shouldn't be that hard. For example, if I order the semiconductors and everyone pays me for them, once ordered if my estimate is over, then I can just use the 90 day refund period within PayPal to return unused money. Is there any reason this sort of strategy won't work? I'm supposing you're worried about the case when you pay me for semiconductors, then I just turn around and pay you for the toroids? In this case, would it be feasible if those who were purchasing items just didn't pay until the end, after all parts were ordered and then of course the purchasers would be required to pony up some extra money for the other purchasers until things could get worked out?

still waiting on one last quote for the Renesas Technology parts... geez they're slow. I've talked with Sowter as well, since I need a pair of input transformers for another project and got the following quote. The model is very similar to the unit on Voltron's Doshi preamp (see Sooper Secret Internals thread), but has upgraded features. The model isn't available on their website directly (at the moment I think it's OEM only), but is similar to the 3575. It is PCB mount with UPOCC wire upgrade. Since I'm pretty sure not everyone is interested in this, I got a quote for 6 pairs and including shipping from GB and shipping from me to you, I'm estimating $130 a pair. The next step up would require 12.5 pairs and would only net a 5% discount, which doesn't really seem worth the effort to me. Soon I need to collect money for the small heat sinks and a deposit for some of the semiconductors to get the ball rolling. I think $120 for stereo build and $240 for a balanced build is a good start. If there are left over funds, they will go to the prototyping of the boards and free heat sinks to Kevin. I took these prices from Pars BOM. In actuality, I will probably be purchasing the 2SA1145 and 2SC2705 in bulk (sealed Toshiba packaging as they are still current part numbers) so if you have any desire for extra parts there will be a lot available. Also, if you want extra EDM heat sinks, please let me know as I can order them. Also, I'd recommend the builders to take a look at the schematic and note areas which it is important to match transistors and resistors. Thanks everyone!

It may be worthwhile to talk with Parts Connexion, as they still service these units and may have some upgrades and mods available if you're interested in putting some more money into this DAC down the line ..

solid state

I think Grawk was getting at the fact that no matter what you do and when you do it, you've already really injured your credibility by making the statement above directly to the vendor which you'd be reviewing.

yes no

oh, so a three-way dispute now. I say you guys have to roshambo...

wait, conflicting info here!! You two must resolve this! I knew Al talked with Pete at length at the Dallas meet about iron, so 909 must reveal his source as well!!

well, I can help there. The PSU are very simple CRC supplies. Which means, you need capacitors and resistors. Minimum you could get by with $50 or so plus whatever Peter is charging for the PSU PCB (for stereo amp). You could easily point-to-point this, but I'm not sure I'd recommend that for a first project. Then you need 2 bridge rectifiers and things like jacks wire and what not. Say, another $50. Finally the transformer itself, so say another $100. Heat sinks and the casing materials might be around this same cost, who knows. Depends if you go with surplus heat sinks and how easily you might be able to fabricate a case.

heh, just razzing you a bit. Anyways, the owner of that place is a nice guy. The boards pictures above can be bought at the links posted in my Spring Cleaning for sale thread. The designer and seller of those boards is the guy who built the amp that is posted above

ya mean other than the link I gave to tech-diy that sells kits? heh anyways, Peter's build is using some premo stuff.. ever what makes a resistor cost $15?

actually, I don't think this is correct. (But correct me if I'm wrong). I think it has more to do with the fact that CD started as 14-bit and as a result had non-linearities at high frequencies and low volumes.

So, just a question for ya'll.. how many CDs do you have with pre-emphasis and what do you feel is the best way to handle playback of these CDs? In my case, they are mostly Japanese recordings. If you rip music off these discs, do you handle this in the software domain? If you're not ripping music, it seems like a lot of newer equipment doesn't handle this spec at all... In the DIY realm, what do you think of handling this in a passive fashion, much like an RIAA circuit, pros/cons?

so, it's not that hard to park the needle on the grid and slide the base without stressing the cartridge suspension?