Awful Quiet Here

[Bob S]

Edit - latest schem added here to avoid confusion. This is a work in progress - don't try this at home - unless you really have to...
So here's the latest beast on my bench.
Not finished by any means. A test mule for a couple of ideas from senior members here, for which I am grateful.
Will get a loop soon.
395 B+ with KT77s.
Marshall Reel front end, D type overdrive & 1 tube reverb.
Little bit of hiss to the OD - haven't started to chase it down yet.
Verb is very good.
What's on the agenda for you Marshall guys this Winter?

[Colossal]

Lovely to look upon Bob! I like your heater wiring. I am a heater hater too (necessary evil). Great layout!

For this winter's Marshall Madness Sale, I have 100W Mercury JCM800 iron, black tolexed Marshall head cab, four preamp tube chassis (extra gain stage), and hopefully lots of snow. Oh yeah, and coffee.

[ampgeek]

Sweet!!

Sounds like the 1 tube reverb is working well in this plan. I have added that to three different Bassman (5F6A) builds over the years and liked it in all.

However, one of the owners felt that it wasn't quite enough "surf sound" for him. So....I threw in another socket and tube and all is well!

I have a pair of KT88s looking for a project as well as a spare JCM800 chassis. I also have a couple of Express OT's on the shelf from RJ that are getting anxious to do something.

The voice in my head is saying...start with a Marshall plan....but I haven't gone much further than that...yet!

Any thoughts from the group on where to go from here?

Cheers,
Dave O.

[M Fowler]

Nice looking build Bob should rattle the walls just fine.

[10thTx]

So is what you've done something like this but with fixed biased and KT77's?

I attached an editable SCH schematic IF you'd like to edit it and share what you've done. There is a second page on the SCH schematic showing the power rail.

With respect, 10thtx

[Reeltarded]

Holy shit Bob is off the ranch!

I want to hear that thing squat!

[Bob S]

I'll post an SCH schematic this weekend (hopefully).
I want to verify where I'm at & add some voltage info to it.
It's a "work in progress" still. I might ditch the KT77's in favor of 66's or 6L6's. Hmmm. Methinks the PI needs some tweaking anyway.

[10thTx]

Bob,

I'll look forward to what you come up with in editing the SCH file. I redrew it closer to what you may have by adding fixed bias, removing the PPIMV and adding solid state rectifier.

Hopefully with a few edits, this SCH file will be useful to you.

I don't know if you're using dumblish LTPI or a Marshallish LTPI values?

With respect, 10thtx

[menger66]

Looks great Bob, I've got a 50watt heyboer PT and OT ready to go and starting to actually
Think about what I'm gonna do with it, I was thinking maybe a jtm45 with ss retro and el34 but that's not for sure yet, I got my turrets yesterday from anouther of our awesome members. And am starting to get excited about buildings a big amp mark

[Smokebreak]

Looks great Bob. I'm quite curious as how to ow you're incorporating D style OD in that thing.

[10thTx]

Bob,

My original Marshall preamp idea into a Dumblish OD etc..... was the D'Mars. I started off with fairly close values to the Marshall tone stack but things kept evolving.

Some things to note:

- The tone stack is now bypassed going into the OD section. This has made
a significant difference in giving the OD a THICK tone, IMO. I simply
could not get enough of a THICK tone in the OD going thru the clean
tone stack ........... or it would be thick but too distorted and harsh. The
OD now is very transparent to my ears.

- I am using the CF as the "buffer" for an active FX

- Using a 12AY7 in V1 has allowed a very nice clean tone with plenty of
contrast (between clean and overdrive) into the OD tone

- I am using a GZ34 with a 300-0-300 PT with 173ma

- The 250p across the 82k resistor going into the LTPI is VERY useful in
helping reduce harshness in high frequencies with no loss that I can
hear in the actual high frequencies. Seems to just smooth them out.

- Note the larger value cathode cap in the first gain stage of the clean
and the OD followed by a much smaller value cathode cap in the
second gain stage of clean and also 2nd gain stage of OD.

Just thought I'd share this with the hope that there may be a useful idea in there somewhere?

I've built a D'Mars (with just 12AX7 and no 5879) for a band that has keyboards and often other instruments like cello, harp (not harmonica), viola's etc....... & it cuts thru the band mix really well even using 6V6's.

With respect, 10thtx

[Structo]

Hi Bob

Like I mentioned in another thread, I need to issue a cease and desist on these Marshall amps being built.

It is totally unfair and cruel to subject fellow members with quality amp builds from our British heroes.
One cannot help but envision El34's glowing and that sound they do so well.

I have no doubt you guys are going to cost me dear this Winter......

J/K

Is this going to be a Marshall Winter?

[Bob S]

Move drawings to the first post (page 1) to avoid confusion.
Added voltages.
Some tweeks - mainly in the power supply.
just did a crash course in SCH... Bit clunky but adequate. And free!
Anyway - PT is Heyboer PT-600. OT is MM O50JM. Choke is Hammond 159P - 10H. Reverb driver is a PTF-22921 from AES I believe. Numbers on the tank look like 4AB3C1B - it's a re=cycle & difficult to read.
V1 - V5 are all AX7s so far. KT77s (so far) biased at 46mA by ear.
Elevated filament supply - was aiming for 80-100v but ended up @ 123 - oops. Don't think it'll hurt though.
I'll add the filters & voltages later today.
Many thanks to 10thtx for all of his ideas I cobbled together. And Miles for his work on the Marshall gainiac front end. And everyone else here that makes this possible - this amp is 10 times more versatile than I am on guitar.
This thing is Wicked. Must get some clips together.

[10thTx]

Bob,

I surely appreciate your generousity in sharing your ideas! I like your design really well. Bravo!

I had not thought of the additional gain stage on the Marshall preamp.

IF you've never used SCH before ............ wow, you sure figured it out very quickly.

There are a bunch of D-style editable SCH schematics, some Trainwreck and Vox, Fender and Marshall on TAG.

With respect and thanks, 10thtx

[cbass]

Dang