We have a lot of money invested, and the build needs to be done right. This is my first major build from a schematic, and I'm pretty nervous about making sure things go as planned. I don't want the smoke check to be that - smokin'. I think an updated BoM would be a great future reference for all. I know there are people lurking, and if you have not kept up on a daily basis, there is no way to really know what's being built. There have been subtle and not so subtle changes since this project began. And yes, my head hurts too.....Regards, Colin

This is a new experience for me as well. I suppose I should give you less choices *OR* more clearly defined reasons/options. In the past when I have responded to a "how shall I build a linestage?" there has been a bit more noise in the background and even more options.

On caps, I think I got them from RS as well. If you're careful with making sure there is a load, you can get away with 25 volt rated caps. Root2 times 12.6 is less than 25 and an L-C filter with 25 v-in also yields less than 25 volts.

I've worked with two other folks who built regulated PS versions of this line-amp and it took months longer than this. forgive me for getting excited on your behalf.
regards,
Douglas

ask more questions like open ended 'Why?', you'll not upset me.

Further grounding instructions: gather all the signal grounds, like the jacks and cathode and volume pot negative together and lead a single connection to the cap's negative terminal.

I forgot that one and chased a bit of noise out of the new one when I rolled the last one over( to take its stepped attenuator volume box out ) and discovered the difference.
regards,
Douglas

No one is more excited about getting this done then I am (OK, maybe my wife's pretty excited too but for different reasons.)
- I finished punching and polishing the copper top last night.
- The heater is ready to go, except I'm waiting on a 1 ohm 5W resistor.
- The CCS is done.
- The base was completed, but thanks to my 2 yo son and some paint is wating to get remade.

Any thoughts on a possible 2A3 PP. I've got two 12 x 18" copper plates that are getting lonely.....Colin

I am working on the 2A3 circuit. With the power Iron, a suitable choke must be specified. I don't know if an off-the-rack Hammond would be a better deal than a custom from Heyboer. Going to have to examine that one a bit...GZ34 rectifier, and one motor run ought to take care of the rest. A bias supply capable of -75 volts is easy enough. A votlage doubler with 30vac input and decent caps will be adequate I think.

And then there is the OPT design. I think a 6k6 with 10-20% E-Linear taps would be an ideal sol'n. Something like an Acrosound TO-300 with a modified tap location. I did some work with a PP 6A5 amp and found that a bit of proper NFB was better than none. The usual doctrine says no NFB with Triodes, but I have reached other conclusions.

We need a driver which can do 120V p-p per phase. Out of a 250-260 VDC B+, this puts some restriction on the plate resistance( lower plate z valves have a more nearly vertical V-grid=0 plate line). The closer to vertical it is the greater percentage of B+ you can swing. Look at 6SL7 and 6SN7 curves, try a 60k plate load and see which can swing more AC.

A 5687 is a likely suspect. It would be a bit light on the gain, but with Guinevere at the input, I think it can be done quite well. It is also a bit simpler with one stage. ECC99 is slightly higher gain, and is reputed to be a good sounding valve too.

The grid choke is available from a few suppliers and is a *BIG* benefit to sonics. Every single amp I have wired one into has been improved drastically over resistive grid circuits. Even fairly low value ones ( down to 47k v. the usual 100k, or 270k for a Dynaco St.70 ).

that's the bones of it at this time now. You could also do a SE 300B at a fairly conservative OP point with the Guinevere power Iron. Finding OPT Iron for SE is not something I have any practice doing.
regard,
Douglas