output section for small venues - JCM800

[pjd3]

Hi there.

Has anyone had good luck building and using a low watt Marshall JCM800 for small clubs?

I build a Marshall Plexi with 6V6 output tubes BUT, while having great tone, the amp can still get pretty loud.

So, I imagine that although having more gain/distortion in the preamp than a Plexi, a JCM800 would still be very loud even with a 6V6 pair or an EL84 pair.

I was curious if anyone had tried a JCM800 preamp with a 6V6 or EL84 in Class A. Or perhaps some British style speaker designed with a very low efficiency, but still maintaining a good tone.

I should probably add in that this amp would only be used for moderately heavy overdriven tones, 70's and 80's heavy rock and hair band type Marshall tones.

Thanks, I'd be very grateful for some pointers and direction on this. I had great luck with a Blackface Fender build and a 20 watt Plexi build and would like to add a good sounding JCM800 amp that can be pushed and still maintain a reasonable stage volume for small clubs and restaurants.

Thank you!
Best,
Phil Donovan

[romberg]

I've had good luck using a 2204 with both a pre and post PI master volumes. Having both gives you the ability to really crank up the preamp while keeping the overall output low. You will also be able to push the PI into clipping with the volume still low. To my ears this sounds fairly close (but not identical) to power amp clipping. It is a good compromise if one of your constraints is that you can't be loud.

Mike

P.S. Plus with both M.Vs you can crank the post master to full and have a full on jcm800 when you can be loud.

[Stevem]

The use of a class A output stage will allow more even order harmonics out to your ears when both played clean and especially when driven hard enough to be into clipping.

It’s bottom end response will also be different when cranked.

Personally I can’t believe that with playing thru a amp with only 2 6V6 output tubes that your too loud.

If the amp is not a combo then the first thing I would be looking into is using fewer speakers or a less efficient one then your playing thru now, or getting a attenuator/ load box.

[gldtp99]

Years ago I built an EL84 x 2 2204 type head and ended up installing both the pre-PI MV and a PPIMV

Also added a fixed Resonance/Depth circuit and added a bit of extra gain to the preamp (and cutting some low freqs in preamp to counter higher gain flubbiness)

I still have this one and it is useful at very low volume levels

Here it is cranked through a Marshall 4x12 but the amp still sounds very good when played in my living room where the acoustic string noise of a solid body guitar is almost louder than the amp's output

[Reeltarded]

I dont like small tubes. I use big tubes and two masters. 800 style plus CF master. You would like it.

[M Fowler]

Your opening post was about low wattage JCM800.

I build a JCM800 2 EL84 combo that is loud and has seen a lot of usage by it's owner.

JCM800 18w front.jpg

JCM800 18w gut 2.jpg

Fowler Marshall 18w JCM800 combo.jpg

[Littlewyan]

I’ve built a 20W Plexi style amp and that is still loud. Not surprising given 20W is only roughly 3dB quieter than 50W. I think your best bet is to build or buy an attenuator. There’s a really good one on the Marshall forum.

[The Ballzz]

Hi there.

Has anyone had good luck building and using a low watt Marshall JCM800 for small clubs?

I build a Marshall Plexi with 6V6 output tubes BUT, while having great tone, the amp can still get pretty loud.

So, I imagine that although having more gain/distortion in the preamp than a Plexi, a JCM800 would still be very loud even with a 6V6 pair or an EL84 pair.

I was curious if anyone had tried a JCM800 preamp with a 6V6 or EL84 in Class A. Or perhaps some British style speaker designed with a very low efficiency, but still maintaining a good tone.

I should probably add in that this amp would only be used for moderately heavy overdriven tones, 70's and 80's heavy rock and hair band type Marshall tones.

Thanks, I'd be very grateful for some pointers and direction on this. I had great luck with a Blackface Fender build and a 20 watt Plexi build and would like to add a good sounding JCM800 amp that can be pushed and still maintain a reasonable stage volume for small clubs and restaurants.

Thank you!
Best,
Phil Donovan

The best solution is a REALLY GOOD attenuator! I'm not speaking of a cheap, crappy unit like the Bugera, Weber and many others, including the RockCrusher that is not cheap, but still crappy, by design! I'm also not referring to active, re-amping style units like the BadCat Unleash, Fryette PowerStation or several others. I AM speaking of GOOD attenuators that don't mess with your tone, feel and tactile response. While you can spend a bundle on one of the ToneKing Ironman II or their "Mini" version, or you can build a REALLY GREAT passive attenuator, designed by JohnH over at the Marshall forum. This design combines a specific balance/ratio of parallel and series resistance with a reactive choke/inductor coil, to preserve not only tone, but feel and response. These attenuators are the most liberating pieces of gear I've ever owned in +50 years of SCREECHIN' & SQUAWKIN' with guitars through tube amps. They allow me to crank any of my 5 to 50 watt amps to their sweetest sonic spot and then adjust the volume to suit the room. The reactive inductor portion allows the amp to see the same kind of "reactive" load that it does when just driving a speaker.

I have tried nearly every attenuator brand and/or design since the late '70s and have found all of them severly lacking in various ways! The JohnH design is simply many times better than any others I've tried! The thread linked below is VERY lengthy, but has a lot of great testing and theoretic info along the way. While there may be a bit of chaff, it is easily skimmed past and is well worth the read. I've already built two of these and am endeavoring to "custom package" one to eventually have one actually installed in every amp I own. The materials cost for a basic (no frills, bells or whistles) unit is between $75 and $125, depending on parts sourcing. All the component values and raw diagrams are in Post #1 of the thread, but recent additions of actual layouts, pics and wiring diagrams start at page #110 or so of the thread:

https://www.marshallforum.com/threads/s ... ing.98285/

Happy Building and Attenuatin'
Gene

[bepone]

for home use even 1W is too loud, (97dB on 1 watt is still 97 dB and is too loud)

so why not to reduce volume with the speaker efficiency or defficiency? try some hifi midbass with bandwith of 5 kHz , take 83-88dB, maybe yoll like it. steal some box from the cheap stereo mini system

[pjd3]

Hey, thanks for all your great feedback and replies.

It sounds like the attenuator over at the Marshall forum is a well working piece of gear to build. I would even consider using EL34's if its that good. (I did include pre and post master volumes on the plexi and like the options). You'd be surprised how many restaurant owners are putting a ceiling on the volume of their bands. They don't want to ruin customers meals. I get it. But personally, believe me, I love the loud chest thump and feedback from an amp that's pushing itself. Those are the tones I grew up on so thats my hardwired reference to proper guitar tone. A friend of mine just offered me today, his old Carvin dual channel combo. I'm thinking of gutting that thing and making a really versatile JCM800 type amp for gigs. And sure, I'd love if an amp like that could fill up a big open stage, but also be set for small venues and still maintain its tactile response, overdrive and dynamic envelope characteristic. Gezzis that would be great.

Well, very good relevant info here. I will allow myself to be influenced by the good ideas, watch outs, and links from this thread.
Thank you!
I'll be back

Best,
Phil Donovan

[The Ballzz]

Hey, thanks for all your great feedback and replies.

It sounds like the attenuator over at the Marshall forum is a well working piece of gear to build. I would even consider using EL34's if its that good. (I did include pre and post master volumes on the plexi and like the options). You'd be surprised how many restaurant owners are putting a ceiling on the volume of their bands. They don't want to ruin customers meals. I get it. But personally, believe me, I love the loud chest thump and feedback from an amp that's pushing itself. Those are the tones I grew up on so thats my hardwired reference to proper guitar tone. A friend of mine just offered me today, his old Carvin dual channel combo. I'm thinking of gutting that thing and making a really versatile JCM800 type amp for gigs. And sure, I'd love if an amp like that could fill up a big open stage, but also be set for small venues and still maintain its tactile response, overdrive and dynamic envelope characteristic. Gezzis that would be great.

Well, very good relevant info here. I will allow myself to be influenced by the good ideas, watch outs, and links from this thread.
Thank you!
I'll be back

Best,
Phil Donovan

Yes Phil, this attenuator design IS that good, with one small caveat. The amount of harmonic feedback obtainable is still somewhat at the mercy of how much actual volume the speaker is producing in relation/proximity to the pickups! Simply more evidence that the universe provides no FREE LUNCH!
Just Sayin'
Gene

[pjd3]

Thanks Gene,

I never expect any freebies in life, only the highest quality concessions and compromises that I can muster. Nobody got off on the experience of an open, pushed roaring complex dynamic Marshall like I have but, I have seem to fallen into circumstance by which volume compromise has become the rule instead of the exception. So, from now on it is a quest to squeak the most out of the volume compliance for which I have to make.

So, ready to experiment with various levels of pre MV, PPIMV and attenuator to find a set of recipes that "compromise the least tone" under the specific circumstance. I've learned to live with less in terms of tone. But, I'm all for minimizing the fall out.

Thank you!

Phil D.

[The Ballzz]

Phil D.

You put that quite eloquently! I am in much the same boat, along with many others that want "THAT BIG BOY" sound, response and feel at "Little Boy" volume levels! It can be quite the balancing act, especially given that most commercially available amps "pare down" the features as they decrease the wattage & volume capabilities! I started my "attenuation journey" in the mid '70s with an ALTAIR attenuator and while it could certainly tame the volume of my fully cranked Black Face Fender Showman and Marshall 1987s and 1959s, as the volume decreased, so did the fun factor of response, tone and feel! I've tried most attenuator designs/brands, pre & post phase inverter master volumes and even delved into various forms of power scaling, all with varying levels of widely varied compromises and disappointments! The attenuator design I linked above is the closest I've found in terms of transparency and retention of all the things tube amp aficionados love!

With that said, if your amp approaches 50 watts, you'll need to at least actively cool it with a fan and/or double the wattage ratings of all resistors and the choke coil, and increase the current rating of the switches. To give an example, even my 13 watt 5E3 Tweed Deluxe needs between -7db & -10.5db attenuation, when cranked to it's sweet spot, to achieve the required volume levels. My 20 watt Marshall DSL20 needs -10.5db to -14db attenuation to get to the same volume levels! Neither of these amps get the unit any hotter than just a little warm. Conversely, my JTM30 (supposedly/nominally 30 watts, but actually tops out at 53 watts) only sounds its best when the master and clean channel are fully wide open and the gain channel dialed in to match. This amp gets the attenuator blazing hot to the point of only being able to touch it for a couple seconds. Safe, but still a bit concerning! A little bit better heat sinking and better ventilation may be just enough to avoid a fan for this amp! I'm endeavoring to build one of these units for installation in each amp I own and so far have only got the Tweed Deluxe and DSL20 completed. They are simple, easy and pretty inexpensive to build, depending on sourcing and choices of components. If you get your resistors on the slow boat from Chinesiawanoreanam, you'll be around $75-ish and if you get the OHMITE/ARCOL units from DigiKey/Mouser, etc, it'll bump up to $125-ish. Of course, all other sourcing of enclosure, switches, etc. impact that price!
Keep On Screechin' & Squawkin'
Gene