69 wiring vs 68 wiring

[sixpakldp]

I'm just about to start installing the circuit board components on my 100 watt kit. At this point, can I install the circuit board components to make the amp a '68 spec amp (less the visual differences and the caps being mounted on top of the chassis) or am I past that point already?

If I'm not past that point and all you have to do is install the components on the board differently, does anyone have a picture that I could follow to do so with the components I have?

I can't wait to get done wiring and fire this thing up! My only other undecided option is whether or not to install the PPMIV or not. From the research that I've done it seems like the best way to get a good tone is to get some distortion via an attenuator and some via a master volume. Let me know what you think on this one.

Thanks,

Paul

[neikeel]

The board is really very similar between 68 and 69 lead specs (68 is 330uF/820R and 0.68uF/820R on V1 and 47k NFB resistor.

68 spec would mean a dual 32uF can in the preamp space (kit will have dual 50) but it is wired in exactly the same way, if you are impatient to get going make the wires between board and can a little longer and instead of bus wire use a black wire to earth lug so that if you send of and buy a 32/32 you do not have to flip the board up just undo the clamp bolt slip the can up and solder a new one in.

The 68 filtering can be obtained by only using one 1/2 of the PI cap for 50uF (the kit has both +ves tied), and one 1/2 of each of the screens (50 of one can in series with 50 of the other is v close to 32 ~ 32 of a 68). Still wire the mains cans as standard to give 50uF and full voltage handling. Your cans are 500v rated I believe and your amp will have 480-490v initial B+ which is a bit tight but should be fine on the screens and PI.

Hope this makes sense, if not post back.

Oh and I think a PPIMV of the Fischer/LarMar type is a good idea. It will get you up and running and then you can decide on an attenuator (I have a Hotplate and Elemental but others swear by the Ultimate Atenuator and there is a new kid on the block too http://www.vintageamps.com/plexiboard/v ... =1&t=84109) Not sure about the Powerbrake.

[tonepilgrim]

Agree with all of the above. I basically did the same thing when I built my first amp. The only thought I would add is this: consider finishing the whole amp as a '69 first (particularly if this is your first time through). Be sure it works. It's easier to debug this way. Then you can very easily start doing things like changing the filtering, trying different coupling caps, add a PPIVMV, etc.

Finally, do a search on user name SDM. He has a website that has very good layouts, including what a '69 looks like with '68 components. That will be all you need.

[neikeel]

Finally, do a search on user name SDM. He has a website that has very good layouts, including what a '69 looks like with '68 components. That will be all you need.

Wish I had thought of that

although I cannot find the diagram you mean today

[SDM]

It was supposed to go in the Wiki section here at Metro. The wiki link doesn't work though lol. Can find it on the second page of thread here:
http://forum.metroamp.com/viewtopic.php?f=3&t=24665" onclick="window.open(this.href);return false;

Not on my site as it was made specifically for George/Metro.

[neikeel]

This link here:

http://forum.metroamp.com/download/file.php?id=7397


http://forum.metroamp.com/download/file.php?id=7396

although this layout has 64uF for PI (my original has 48uF 16+32 can) and uses 32+32 in series with 32+32 to give 32 ion screens which is twice that on my original (=16uF).

Depends on how wary you are of being close to the 500v limit on your filter cans?

[sixpakldp]

Thanks guys. I'll be using this link in the future. My original plan was to get up and running as a 69 and tweak later. However, I figured if there is anything I could do to minimize doing things twice down the road I may as well.

I'll probably buy a hotplate, I had one previously that I used with my DSL 100 that I sold. Didn't do much for that amp in particular other than cause problems, which is why I'm building a metro.

I just wanted to see if you guys thought it would be good to go 1/2 master volume and 1/2 power tube saturation.

Later on.

[Big Mike]

In general I think a combination of methods IE: Hotplate AND a master both minimized in how much they're used, IE 1 click on the HP, 2/3rds up on the mV sounds better than just cranking the master down to 1/4.

[neikeel]

In general I think a combination of methods IE: Hotplate AND a master both minimized in how much they're used, IE 1 click on the HP, 2/3rds up on the mV sounds better than just cranking the master down to 1/4.

My opinion too