The ultimate Marshall Head??

[bnwitt]

My project to hand wire a version of the DSL401 is delayed due to someone begging the stock amp off of me some time back so,  I've decided to build myself the ultimate Frankenstein one from column A and one from column B Marshall head amplifier.  The only problem is I'm not sure what kind of bells and whistles I should put in it.  I definitely want it to be EL34 100/50 watt switchable and have foot switchable overdrive/gain.  I'm not sure if I should use a master volume or a VVR for low output or just have the pentode triode switch.  As far as the base preamp circuit, I'm wavering between the 1959, 2403 and the DSL401 (with a 100 watt power section) or maybe even starting with a JTM 45/100 layout.  

I want to build a versatile amp that has a great Marshall clean and high gain sound and can fit multiple venues (bedroom not included).  I think maybe a real two channel amp with dedicated tone stacks and volume controls per channel is necessary.  As ususal I'm looking for feedback and opinions from all of you Marshall tone aficianados.  This would be a great "Team Hoffman" project.  I think this amp will have lot's of pull switch controls for different bypass caps, shared/split cathodes etc. etc.  I think maybe a footswitchable Hoffman hot switch gain boost or one wire mod type gain too.  Maybe a reverb or on board delay circuit.  Lot's of things running around in my head.  I will be getting my hands fixed in the next few months and want to start playing again.

[bigdaddy]

I have played so many to me the ultimate Marshall head was a 1970 MKII 50 watt through a 4x12" 120 watt bass cab. I felt like it was magic, every note said something and any little technique I used had it's own special sound and did not run into other notes. Of course the volume was on 10 as was the treble with the presence almost off, bass and mids were low too. I had a Norlin White Les Paul Custom with a 60s T top in the neck and a DiMarzio Super distortion in the bridge, one of the first batch of production models.

The other time I used a full 100 watt stack. Those gigs were the first time as a teenager I actually sounded like live Cream, Mountain and Zeppelin. I learned at an early age how to handle being very loud and how to control those monsters. Even though I Loved the sound of a BFSR and BF Bassman and some of the White amps from fender, nothing else made the hair on the back of my neck stand-up like those Marshalls. They sounded best right before they blew up!!!!!!!

[bnwitt]

So Bigdaddy I take it that was a 1987 circuit.

[bigdaddy]

I'm not sure, but it was the big box heads so I think it was the 1987, it was a bit before I was really into and learned about what was what. I did know that it had the .68 cap on one channel's cathode and another on the CF. That added a lot of high end gain which gave it that sound. When I tried the other versions I could not turn it up all the way because of the bass output. Those models with the lower cathode caps could be cranked without the lows, that also went a long way to saving the speakers which would blow like crazy for people.

If you want to hear a small boxed head with the 8x10 cab watch Woodstock, Carlos Santana used one and that was his best sound ever. He used a P-90 SG, but it was a little bassy.....that's why I like the .68mfd cathode caps. I even had some reissue JTM-45 heads and changed the cathode caps to .68mfd. Those amps sounded very good stock with that mod and a good set of tubes, rebiased. I also did that mod to tweed bassman type circuits and that also made the amp much more usable for me.

Many guys jumpered both channels rather than crank it. That gave you a full sound but without the total raunchy grind I liked.

[Tiny_Daddy]

For all-out playing, make that first filter section is at least 100uF (for example two 220uF in series) and use 3Amp diodes.

[bnwitt]

what about two 50uf's in parallel after the rectifier like the standard Marshall setup?

[rzenc]

what about two 50uf's in parallel after the rectifier like the standard Marshall setup?

I guess TD was referring to 2x220uF in series in order to increase voltage rating, maybe.

I would definitevely go with lower voltages, around 380VDC on EL34 plates. Way up more sustain and clarity.
12AY7 @ V1 made it sound how it was supposed to sound to us 

Also what bigdaddy said about the cap on V2a cathode is true about giving it "magic" to cut thru the mix with strengh  - without the cap it sounded cool, but that partial bypassed cathode makes it hot.

Hope this helps
Best regards

Rzenc

[Tiny_Daddy]

Capacitors: Check your voltage. Some Marshalls run over 500V until the tubes warm up.

[bnwitt]

Ok, so now I'm thinking 2204/1987 two channel amplifier with typical 690VDC (345-0-345) PT.  However, I've got a few  matched quad sets of KT88EH tubes I bought back in the late 90's that I'm thinking I should put to use so maybe a KT88 and EL34 power section with a wide range toggle switchable bias circuit instead just EL34 tubes alone.  Maybe even a rotary switch for KT88, EL34, 6L6, 6550 etc.  It seems to me that I've seen a 2204/1987 mixed preamp somewhere before.  I can add the V2a 0.68 capacitor on a pull switch along with other possible pull switch mods too.

[rzenc]

I really like 6550 on high gain amps. Less is more school of thinking.
And if you really plan on different output tubes - EL34 and 6550 - how about Dual Post P.I. Master Volumes?? one for each pair of tubes, i.e.: one for El34 and one for 6550??

With respect
Best Regards

Rzenc

[TubeGeek]

Sluckey helped me with the same idea a few years ago.  He designed a dual preamp 1987/2204 switchable amp.  I can email the pdf he created if you'd like, just let me know.

Here is a screen snapshot of the layout...

[sluckey]

I can email the pdf he created if you'd like

And I still have the Visio file for that dual Marshall if you want it.

[bnwitt]

Tubegeek,
Thanks for the reply.  How does the amp sound?


Steve,
I'd love to have the Visio file.
Barry

[TubeGeek]

I built two of these and the customers are very pleased with them.  Both builds were quick jobs so I couldn't take time to evaluate them like I normally do.  I didn't even have time to take pics of the projects.  I built them away from my shop on a weekend.  From the 20 minutes I did have to play them, they sounded really nice.

I used Hammond Iron on both amps.  I do have the parts set aside to build myself one of these amps.  One of these days I will get around to it.

[topbrent]

Another version of the multi-era sounding Marshall amp is the October from AX84.com

Gives up the different flavors and eras of the jtm45-1987 circuits.

Loud and louder versions:
http://ax84.com/static/october/AX84_October_Stage_090501.pdf
http://ax84.com/static/october/AX84_October_Club_090519.pdf

[bnwitt]

Ok, so after a quick review of the Dual Marshall layout my first question is why the 3@ 35uf filter caps and why on the board instead of the typical Marshall 6@ 50uf can layout?  What does that do to the bass response in the amp?

Topbrent,
thanks for the AX84 files.  I'll take a good look at them too.

Barry

[sluckey]

According to the schematic, all caps should be 50uF. The 33s on the board should be 50, but since those 3 caps are used in the preamps, I doubt there will be any noticable change in bass response between 50s or 33s. The power amp will still be plenty stiff.

The amp uses a total of 7 filter caps due to the extra preamp. I could have used 3 each 2x50 cans and only one single 50, but I chose to use 2 each 2x50 cans and put 3 single caps on the board. I like having the preamp node caps as close to the preamp circuit as possible. Doing it that way allows you to connect all grounds for a particular tube stage directly to the filter cap that feeds that stage. And, you have direct access to the filter caps since there's no hidden can underneath the board. It'll work either way. I prefer my method. You could shave a couple inches off the board if you use 3 cans though, but you still got to have one single.

[bnwitt]

Gotcha

[rzenc]

I'm following this topic with great interest since I also plan to build something along these lines. and for another mod, if you compare 2203 preamp and Mr. Hoffman's Hot Switch, you will note that on 2203 there is a 10K resistor which biases V1b fairly cold, while Doug uses 2K2. How about a rotary switch in order to select between them? If I recall it right, under the Title the ultimate JCM800 from  tales of the tone lounge, he calls for 4K7... So, I was thinking about installing a rotary switch with these values plus something in between...Soldano, on SLO100, goes with 39K.

http://tone-lizard.com/Ultimate_JCM800.htm
http://www.schematicheaven.com/newamps/soldano_slo100.pdf

Hope this helps

Best Regards

Rzenc

[topbrent]

Here is another PDF to glean some ideas from.  It is a hot rodded JCM800 2204 design.  (4.7k cathode resistor/10uf cap on v1b)

ThunderTweak topfuel 50 http://www.triodeamplification.com/files/Top_Fuel_Plexi_50.pdf

[rockgod212]

hey can anyone explain in detail to me how i can add a filter cap to my 2203 with 2 extra stages? im only running a dual 16uf can for the preamp and i want to run another 16uf cap for my 2 extra stages.

[bbirling]

I can email the pdf he created if you'd like

And I still have the Visio file for that dual Marshall if you want it.

Iwould be interested in the visio file. I just completed an 18 watt and for some reason I am now on this Marshall kick.

Bruce
bbirling@memphis-amps.com