Metropoulos Forum

so im building a 100w plexi based amp but modded with extra preamp tube.
it will be a gain lovers delight.

the question and really why i made the post.

which trannys would you use?

mercury?
heyboer?
hammond?
******?
other?

lemme hear ya,

Mark

I would get the ****** since he can voice it the way you want.

I've gone with ******, But they still haven't arrived as yet for a 12xxx 67-68 can't wait to get my hands on them when they do arrive.

Talked to Chris acouple of times on the phone great guy ( so is Geoge ) both very helpfull and informative.

Chris came highly recomended by a tech friend of mine and read / heard great things about his work so I went with him for my iron on my first build. (I think I need all the help I can get to capture the MOJO)

I'm sure i won't be disapointed when they arrive.



havent got the choke yet , but I'm going for a large one got to ask George about that one Chris doen't do chokes

rockstah wrote:so im building a 100w plexi based amp but modded with extra preamp tube.
it will be a gain lovers delight.

the question and really why i made the post.

which trannys would you use?

mercury?
heyboer?
hammond?
******?
other?

lemme hear ya,

Mark

You know what I think hey Mark?

5150loveeddie wrote:

rockstah wrote:so im building a 100w plexi based amp but modded with extra preamp tube.
it will be a gain lovers delight.

the question and really why i made the post.

which trannys would you use?

mercury?
heyboer?
hammond?
******?
other?

lemme hear ya,

Mark

You know what I think hey Mark?

i do indeed man.

i figured while im building i could try heyboers as well thinking this is going to be a high gain amp and maybe i shouldnt use a ****** tranny in it? maybe ****** would be better of in a plexi. ( this amp will have an extra preamp tube).

but them i started thinking more that i should get ****** no matter what.
i must talk to Chris.

what about a choke for this amp? 5h 10h 20h?

A 3H will be dirtier sounding and going cleaner with more Henries, I think 7H is a nice "in between", it will be a little tighter also, one thing to really consider here the dc resistance specs, I'd go with a 300ohms around there, not those 100ohms or lower ones.......

What are you looking for in general? A gain monster?

5150loveeddie wrote:A 3H will be dirtier sounding and going cleaner with more Henries, I think 7H is a nice "in between", it will be a little tighter also, one thing to really consider here the dc resistance specs, I'd go with a 300ohms around there, not those 100ohms or lower ones.......

What are you looking for in general? A gain monster?

i hear ya - it will be a gain monster in its first incarnation - ( you know me) first spec will be an added tube - 4 stage but i would imagine it will end up close to plexi spec eventually.
so 300ohm atleast. hmmm 3 - what did evh use i wonder... seems i have seen schems of the early amps and they are like 20H.

The schems all said 20H but it seems they threw in whatever they got their mitts on, the RS 20H, the 3H like George's '66 had, probably others too......

so 7h is happy medium how so over say a 3h? more headroom - not as much hair? do tell.

I like the 10H's as a "happy medium" meaning simply an average of what got put in the amps.

When I experimented with the 10H vs. the 3.3H in my Super Bass I didn't really notice any difference in the amount of hair of the amp. The extra tightness in the bottom was readily apparent though, just like adding filtering in that respect. Less compression, punchier by a bit.......but it didn't help much with ghosting like I was hoping so the 3.3 stayed.......

Flames1950 wrote:I like the 10H's as a "happy medium" meaning simply an average of what got put in the amps.

When I experimented with the 10H vs. the 3.3H in my Super Bass I didn't really notice any difference in the amount of hair of the amp. The extra tightness in the bottom was readily apparent though, just like adding filtering in that respect. Less compression, punchier by a bit.......but it didn't help much with ghosting like I was hoping so the 3.3 stayed.......

good food for thought there - Thanks Andy!

just found this thread! i ordered the mm 3.3 last night. i hope it sounds good in a 12 series...

Good question: I am building a JTM50 right now (no Master) and in my research I am finding that the classic Marshall heads that broke up early and had the "good" distorsion ie from power tubes, Trans, & Speakers .
Had Low B+ Voltages . . So . . I have been working with Mercury Magnetics to get the rigyht transformer for me . . Why MM well I have not run into a tranformer company that can quickly model a transformer based on desired B+ voltage . .

Theory the lower the voltage the warmer the bias . . and the more head room the amp has before it breaks up

Hope this helped

Most manufacturers shouldn't have a problem setting the secondary windings for a particular voltage. The secondary voltage should be 0.707 times the desired B+. This is only for power sections with a diode bridge rectifier, like a 100W Marshall. So for a nominal B+ of 460V, you'd want 325VAC at the secondary windings. Manufacturers don't seem to like taking B+ as a spec, but prefer to know the desired secondary voltage since they don't know how you have designed your power supply.

As for the series resistance of the choke, this will directly contribute to the sag of your amp. When the preamp is drawing a lot of current due to a jump in the input signal, the DC voltage drop accross the inductor increases, which reduces the supply voltage to the preamp. This is sag. If you want less sag, you want to go with a choke with a lower DC resistance, like 100 ohms. If you want more sag, go with the 300 ohm models.