Another Maggy Thread

[brimat66]

Man that turned out nice!:thmbsp:

 

[stanbp64]

WoW!! Looks great!:yes: How do you like the 6GK6's compared to EL84's? Look foward to the schematic, I think this will be my next project after i whip together a little guitar amp for a friend. How well will those trannies work with 8ohm speakers? Stan

 

[jaymanaa]

Thanks all, The TXs seem to love the 8 ohm load of the Heresies. If I had to go out on a limb and compare the 6GK6s to 6BQ5s, I'd say they sound "more powerful" (faster maybe and more dynamic). They are certainly not a "lesser" tube.:thmbsp:

 

[Redboy]

Another nice amp, Jay! :yes: I particularly like the cage you put together for that butt ugly iron!

 

[bricktop]

Nice work Jay. If you didn't notice, that rectumfier is a 5U4G in a 5U4GB bottle. A bit more drop than the GB - and people revere the G more than the GB as you probably already know

 

[jaymanaa]

Nice work Jay. If you didn't notice, that rectumfier is a 5U4G in a 5U4GB bottle. A bit more drop than the GB - and people revere the G more than the GB as you probably already know

Ha, I didn't even notice. I just grabbed the first thing I found in a box of old rectum fires. I could use a little more juice, so I'll have to correct that.:yes:

 

[gogofast]

that is a really nice looking amp.
i specially like the wood work around the amp. how many coats did it take to look that nice? i'm not even gonna ask you about the metal inlay...:drool:

 

[jaymanaa]

That's about 8 coats of Formby's tung oil, and yes, that metal inlay was a PITA. I originally planned to do a mahogany corner "inset", but screwed up the cut on the table saw. I didn't want to throw the base out, so I came up with that idea. It turned out OK, but getting it carved just right, took a lot of patience as well as exacto blades. The amp really looks cool in a dimly lit room. The copper reflects the filaments as does the finished cherry veneer. It sounds really nice too, so I think it will be around for a good long while.:yes: I'm trying to post the schematic, but I'm having trouble. I'll get it figured out though.:thmbsp:

 

[jaymanaa]

Schematic as promised. I tried to make it detailed, but feel free to ask questions. The cathode R didn't show, but it's 150R 5watt per channel.

 

[stanbp64]

Jay, I re-drew your schematic w/ tinycad and thought I would post it. If you see any errors let me know. Un-educated question alert!!!-- why the extra 470k and b+ leg on pins 1 and 6 of 12ax7? Stan

 

[stanbp64]

Anybody?

 

[jaymanaa]

why the extra 470k and b+ leg on pins 1 and 6 of 12ax7? Stan

Ha, because I goofed.

 

[stanbp64]

Well, shows how little I know.... I wasn't sure if it was really a mistake or not. I updated the schematic.

 

[stanbp64]

Keg or anyone, Is there a quick (simple) explanation for determining the load of the current tap (constant current) when modeling a p/s in psud2? How was the load determined in the attached example which came from an earlier post? Thanks, Stan ( i can't attach the schematic of the 8601 again)

 

[Kegger]

Keg or anyone, Is there a quick (simple) explanation for determining the load of the current tap (constant current) when modeling a p/s in psud2? How was the load determined in the attached example which came from an earlier post? Thanks, Stan ( i can't attach the schematic of the 8601 again)

Pretty easy and straight forward.

How much current is in each output tube?
So for this let's say 35ma, times that by 2 get 70ma, toss a couple for losses, 72.

Each tube in the front end draws lets say 1ma each and each screen say 3.5ma
so we have 2 plus 7 for a stereo amp, toss in 1 for loss we get 10.

Measure the current in each tube by deviding the voltage present at the cathode
by it's cathode resistor value, calculate your total current an plug it into the sim.

The screen is a little more difficult to measure, usually look at the tube data sheet
for that, but it is very small anyway so not much to make a significant difference.

 

[jaymanaa]

Keg, what improvements can/would you make to that schematic?

 

[Kegger]

You mean your Push Pull one?

If so I haven't really looked it over that hard, many things goin on in my head.
(when I get a chance I can see if I have any suggestions though)

If it's the single ended one I did up I'm done with it, works great! (Listening to it)

 

[jaymanaa]

You mean your Push Pull one?

If so I haven't really looked it over that hard, many things goin on in my head.
(when I get a chance I can see if I have any suggestions though)

If it's the single ended one I did up I'm done with it, works great! (Listening to it)

The PP one back just a few posts. Take your time.:yes:

 

[stanbp64]

Thanks for the info Kegger!

 

[stanbp64]

Pretty easy and straight forward.

How much current is in each output tube?
So for this let's say 35ma, times that by 2 get 70ma, toss a couple for losses, 72.

Each tube in the front end draws lets say 1ma each and each screen say 3.5ma
so we have 2 plus 7 for a stereo amp, toss in 1 for loss we get 10.

Measure the current in each tube by deviding the voltage present at the cathode
by it's cathode resistor value, calculate your total current an plug it into the sim.

The screen is a little more difficult to measure, usually look at the tube data sheet
for that, but it is very small anyway so not much to make a significant difference.

Please excuse my ignorance but I am trying to get a handle on this. It seems easy enough if I have an amp to measure but what if all I have is a schematic? Take the attached RH84 schematic for example. how do I figure the current to use as current tap if modeling the p/s?