Spitfire Clean Channel + Jcm800 Overdrive Channel possible?

[Vdelli]

Hello,
I´m Christopher from Germany  . This is my first topic here on this nice forum.

I am a Beginner. So far I have built three amps successfully. A Soldano SL60 on PCB with a lot of help, a 3.5 Watt Trainwreck Express Clone and a Matchless Lightning Reverb I have just finished.


Now I want to build a two channel amp with two of my favorite sounds, if it is possible.

For the clean sound I want a kind of a Matchless Spitfire channel and for overdrive sound a JCM800 style channel.
I thinking about to use a 2x 6V6 Powersection, maybe 4x 6V6...I´m not sure.

Do somebody have an idea whether this could work, becouse of the different rectifiers and maybe the PI?


I hope my English is acceptable 


With best regards

[PRR]

Welcome!

> I hope my English is acceptable

Better than most of us.

> different rectifiers and maybe the PI?

This is mostly cut-and-paste design. The key is knowing where to cut. Usually the PI "goes with" the power tubes, so cut that whole chunk. The power supply often goes with this whole chunk, though anything of the right voltage and current can be used (go with the parts you can get). Then figure out the Spitfire and JCM *up to* the PI, paste those. You want either a switch or a mixer to select/mix one or the other path.

All of this can be done roughly with some schematic images, a screen-capture tool, and basic image edit software (even MS Paint).

When you have the electrical idea mostly right, then you may want to think about a layout plan. Since your several "chunks" may have originally been built differently (lugs, turrets, PCB, parallel or criss-cross parts), this may be more of a headache.

[uki]

Welcome to the forum !!

This place rocks man !!

[Vdelli]

Thanks for the answers!

Okay I understand! So I try this way!
I bring the JCM800 preamp + spitfire preamp + Hoffman Plexi 6V6 power section on a sheet of paper and see how I put this together.

CeriaTone has for both preamps working layouts, maybe this could bei a good point  to start.

[Glennjeff]

Hi Vdelli,

Put a circuit diagram together, paste it here and folks will give opinions.

Once the theory is good then proceed with layout, which is quite an art form and some very experienced people here would be quite happy to help.

Wrecks usually use EL84's in the PA and that is a big part of the magic in my ignorant opinion.

Take the time to get the ideas down on "paper", parse it through willing folks and then do the building.

It is almost difficult to go wrong with valves (tubes) .

[Vdelli]

Hello Glennjeff,


thanks for answer!
Yes I try to put the circuit diagrams together, but that will have to wait a 3 weeks.
Next week I will fly to USA for 18 Days. My second time in the US. 4 days Chicago then 14 days with a car from Jacksonville to Key West. A typical tourist tour ;) . 

Maybe I'll find this weekend time to start, than I let see you!

Thanks!

[shooter]

Welcome

Hoffman Plexi 6V6 power section

Take a look at "how" doug used a single input to feed V1a and b, you might get some insight on combining  your 2 channels prior to the PI.  I did a *stitch* together using the Plexi pre and a matchless power section.
Great amp!
good luck

[Vdelli]

Hi shooter,

thanks! I have a look at the circuit diagram of doug 's plexi 6V6 . I have pretty much done the same with my Matchles Lightning clone . I only use one Hi - input.

Sounds interesting! Deos it sound like a plexi, or more like a Matchless Nighthawk?
 

[turtle441]

Christopher, welcome to the forum!  Having recently finished the design on my first "stitch job" amp, a bit of practical advice:  While you can just use a photo editing program to piece together the schematic, it's sooooooo much easier if you use a program designed for editing schematics.  There a bunch of freeware programs to choose from.  I used ExpressSCH for the schematics and DIY Layout Creator for the layout.  Makes it much easier to adjust things after the smarter guys on the forum give you feedback.

[shooter]

Deos it sound like a plexi

Mostly yes, I used the clubman power section, I also used an inter-stage 1:2 tranny as my PI, which gives it's own unique sound when distorted, the musicians tell me don't touch it, it's great!  I'll take that

[Vdelli]

 Hi turtle441,

thanks! I just downloaded ExpressSCH...looks good! I think that is a nice tool, I only need to install a components libary for tubes.

I also used an inter-stage 1:2 tranny as my PI   

I see thats on a few old HiFi Amps or old radios, but never in a guitar amp. Sounds interesting!

[shooter]

never in a guitar amp

I stole it from Gibson's GA-5T, who probably stole it from PA or audio amps?
I like it because It keeps the PI simple, the downside, it can't handle current.

[Vdelli]

Hi,

has anyone of you ever listen to a Mark Huss  6V6 Plexi or the Hoffman 6v6 Plexi ? Can it be that this amp sounds a bit like  somethin between a JCM800 and  a Plexi ? In some YouTube videos, the 6V6 Plexi Sound modern to me with much more gain as a normal Plexi....

[tubenit]

Vdelli,

I love innovative ideas so I like it that you are trying to capture two sounds that you like.

It will be a challenge to accomplish those two "exact" tones. 

The Spitfire has one gain stage going into an LTPI that has significantly different values then the JCM800 LTPI values.

The JCM800 has essentially 3 gain stages going into an LTPI.

IF you are wanting to go from a clean tone to the overdrive tone while playing,  it would be a challenge to accomplish that without having a HUGE volume boost.

The Spitfire uses EL84 power tubes and the JCM 800 uses EL34 power tubes.

The Spitfire is cathode biased  and the JCM800 is fixed biased.

What I do think you could do is build Hoffman's Plexi 50w with his hot switch & that would accomplish both a nice clean tone and overdrive tone. You could use his relay switching for the Hot Swith. 

I am not trying to discourage you from pursuing the idea that you have.  I am just pointing out the challenges in making it happen and trying to offer another consideration for a nice clean and nice overdrive tone in the Marshall type sound.

With respect, Tubenit

[tubenit]

Take a look at this thread that has a hot switch with pots to dial in the volume/tone.  Look at the schematic in reply #7

http://el34world.com/Forum/index.php?topic=20613.0

With respect, Tubenit

[tubenit]

And here is another nice option from Sluckey (moderator) on the forum.   I've attached a SCH version that you can edit to whatever you want.

It also allows the possibility of a cleaner Marshall tone AND an overdriven JCM800 tone.

You could modify some of the component values on the Plexi 50w side to ensure the clean tone and also modify the component values on the JCM800 side to increase the overdrive. 

Just an idea to consider.  I am NOT saying that you "should" do this.

With respect, Tubenit

[Vdelli]

Hi Tubenit,

Thank you very much! This Plexi / JCM 800 schematic looks very interesting! Before I came to the idea of a Spitfire Channel, I had the idea to build an amp with only one channel. A JCM800 with a switch which bypasses the third gainstage or something like that for a plexi sound. I don´t need tons of gain. I have a JVM 410 H and a Soldano SL60 Clone....both have too much gain and are simply too loud...especially the SL60.


The clean channel doesn't need sound exactly like a Spitfire.

I just like this ... I dont know how to describe it in English. I like this ´"microphonic" "percussive" "- as if you had a contact microphone on the guitar clean sound". The Matchless Lightning has the same feeling when you play it clean.

Is that a Vox clean sound?   


An important point would be the wattage. I want 20-30 watts.
I think 2 6V6 could be a good choice for that wattage.

[tubenit]

To offer some more information and thoughts to consider.............

I have two amps that are cathode biased and can either use 6V6's for about 14 watts ........ OR 5881's for around 17 watts to 23 watts of power at 360v - 390v on the plates depending on what rectifier I am using. The amp does not have to be rebiased to switch tubes.

The PT for those two amps is 300-0-300 with about 173ma.

With respect, Tubenit

[Vdelli]

Thanks Tubenit!

what kind of amps are these two?

23 watts sounds good to me! Do have schematics for this kind of power amps?


thanks!

[shooter]

2x 6V6 Powersection, maybe 4x 6V6...I´m not sure.

If you're cathode biasing you might be hard pressed to get 20-30W with 2, 4 doable.  I mostly use cathode bias and to get to mid 20w clean-ish I used 4XEL84's, 2XKT88, and 2XEL34's.  I settled on the 34's since that's what the clubman had.  They fit nice between the KT's too clean, and the 84's to crunchy.

[tubenit]

23 watts sounds good to me! Do have schematics for this kind of power amps?

Do a search for the D'Mars which is sort of a Marshallish clean into sort of a Dumblish inspired overdrive section.

Here is a sound clip for the D'Mars:   

http://www.soundclick.com/player/single_player.cfm?songid=11824794&q=hi&newref=1

And the other amp is the Tweed BluezMeister which I play both with 6V6's and 6L6's/5881's.

with respect, Tubenit

[Vdelli]

@shooter,

yes I think, I have to use 4 6V6 or 2 EL34, 6L6, 5881 or so...is it a big difference in sound between cathod-biased and fixed-biased? I saw some guys here in a german Forum they put a switch for both ways, but they say, that there is no big difference. 

@Tubenit

Wow! I love that sound of both amps! they sound really nice! For my taste i like the bluezmeister a bit more!

Tanks!

[tubenit]

 

i like the bluezmeister a bit more

Hoffman sells a turret board for the Tweed BluezMeister. 

There is an ExpressSCH schematic and layout here:  http://el34world.com/Forum/index.php?topic=9498.0

Not trying to talk you into building one, just providing information for you.

With respect, Tubenit

[Vdelli]

 
Not trying to talk you into building one, just providing information for you.   

Thats okay, I have to say thanks for all this informations!

This Kind of amp + a kind of a jcm800/plexi channel would be the perfekt amp for me 

How does the Bluezmeister handle distortion/overdrive pedals? Most the time I use the OD1 green channel of my JVM with gain on 9 / 9:30 clockwise...for more drive I use a combination of a Klon Clone with a tubescreamer or something like the Nobels ODR1.

[tubenit]

How does the Bluezmeister handle distortion/overdrive pedals?

I almost never use overdrive, distortion or fuzz pedals even though I have a few.  The Tweed BluezMeister clean channel is very nice with OD pedal the overdrive channel is just OK.

I always use either delay or reverb in an effects loop.

With respect, Tubenit

[Vdelli]

Thanks Tubenit!


I had a lot of time here in holiday to think about what is the best for me. So I think the Idea of the Plexi/Jcm 800 amp would be a nice  choice, if I use the Plexi channel as "clean" channel.

I have to say, you guys live in a wonderful country! last week I was in Chicago, very nice with all the Blues Bars like the " Blue Chicago" or the "Kingston Mine". I never heard that kind of "real blues" live. awesome!

After this week here here at the Florida Keys I'm back in Germany, than I can start with  the new  amp :)

[tubenit]

I don't know if it is the case,  but you might send Sluckey a personal message to see if he has a Visio layout to go with the JCM800/Plexi50
schematic that he provided?

His layouts are phenomenal!  And very easy to read and follow. If he has one, it will be drawn up well and very useful to you.

With respect, Tubenit

[Vdelli]

Thank you Tubenit!

I found a complete pdf file with schematics, layout and a drill tamplate from sluckey on the web (attachment)

With that, it looks quite easy to do.

I do not know if it is necessary to use a separate tonestack for each channel to make the amp more flexible.
Maybe I double the tonestack from the schematics and add a second mastervolume. So I can switch between two full preamps. So I have to put the channelswitch between the PI and Master 1 or Master 2. Is this a possible idea?


the only thing I want change for shure is the wattage. 50 watts are really to much.


With best Regards

[shooter]

50 watts are really to much

Might consider using Cathode biasing vs fixed bias, would drop your output into the 25ish watt range, but you'd be surprised how may plays tell me; "that can't be 23W"!

[tubenit]

I found a complete pdf file with schematics, layout and a drill tamplate from sluckey on the web (attachment)

Sluckey is the man!   Very cool!  Not surprised that he had such a thing.

I would do it exactly as he has drawn it up & use the DPDT switching as he suggested.

There is ALOT of good information on relay switching here:  http://el34world.com/Forum/index.php?topic=14348.0

IF you are genuinely concerned about the 50w being too much, then you would have some options:

1)  Use a 300-0-300 PT with at least 140ma or more.  With solid state rectification you would probably get 420v estimated.  You can run the
     6L6/5881's or JJ 6V6's at 420v with no problem.  You probably have to change the bias for the tubes to change between those.

2)  You could opt for a tube rectifier.   With 5Y3GT = 330v,   With 5V4 = 360v,  With GZ34 = 390v and you can still use a solid state rectifier
     plug in like Hoffman sells.  Lower voltages on the preamp will change the tone.  However, it would be possible to change the dropping
     resistors on the B+ rail to keep the preamp voltages fairly normal/original and still have lower power tube voltages.

3)  You could make it cathode biased to lower some wattage and use 250-330 ohm/10w resistors.  I personally like cathode biased amps.
     With cathode biased, you simply change between the 6V6 and 5881/6L6 tubes. No rebiasing.

4)  You could add PPIMV  (post phase invertor master volume) and that will help reduce volume and still allow the preamp to be somewhat
     cranked.

5)  If you wanted a more elaborate way to reduce volume, you could use London Power Scaling:  http://www.londonpower.com/power-scaling

With respect, Tubenit







 

[tubenit]

I personally have an amp that uses a 300-0-300 173ma PT and I use tube rectification and usually alternate between 5V4 and GZ34 tubes.

The amp is cathode biased and produces about 23 watts with 5881's.

And I have a PPIMV added to it.  It also has an active FX and the FX level acts as a master volume prior to the LTPI. 

I don't have too much of a problem in controlling the volume and getting the tone I want.

With respect, Tubenit

[printer2]

Thought of making a pedal sized switching amp with a tube preamp. Took a circuit that I cooked up that changed a Plexi to a JCM800 amp. Could switch it with a DPDT foot switch.



But what if you want to use the low gain section of the JCM and then switch in the second triode to go hi gain, easy enough with the DPDT switch. Now if you still want the Plexi, you need another switch to share the input between the channels and change the cathode resistor and cap on the low gain channel. Other than the 910R and 22uF cap pretty much can fit on a Plexi layout.

[Vdelli]

Thank you guys!

Might consider using Cathode biasing vs fixed bias, would drop your output into the 25ish watt range, but you'd be surprised how may plays tell me; "that can't be 23W"!   

   
3)  You could make it cathode biased to lower some wattage and use 250-330 ohm/10w resistors.  I personally like cathode biased amps.
     With cathode biased, you simply change between the 6V6 and 5881/6L6 tubes. No rebiasing.
       

This sounds good, becouse of the wattage and the opportunity to change between different tubes without rebiasing

     1)  Use a 300-0-300 PT with at least 140ma or more.  With solid state rectification you would probably get 420v estimated.  You can run the
     6L6/5881's or JJ 6V6's at 420v with no problem.  You probably have to change the bias for the tubes to change between those.   

And this option seems to be the easier way, or isn't it?


The question is, what sounds more like the "real" thing.

I read that the JJ 6V6s sounds more like a 6L6 becouse of the bigger plate than regular 6V6, but a 6V6 breaks up earlier than a 6L6.
Maybe thats a good choice if I want use the fixed bias thing?!



@printer2

Thank you! That looks interessting too!


with  best regards

[shooter]

what sounds more like the "real" thing.

can't help ya there

[Vdelli]

After reading the whole day about 6V6 vs. 6L6 vs. El34  and fixed biased vs. cathode biased etc. I will try this with cathode biased 6L6 tubes. I also like to use SS rectifier.

Now I have to look what changes I have to do on the schematic.

Is a 300 -0- 300 PT still the right choice?


Thank you guys for all your help and informations!

[shooter]

6V6 vs. 6L6

Is a 300 -0- 300 PT still the right choice?

As long as your Fil current is there, the 6L6 is more demanding

[Vdelli]

I found a PT that should work.

It´s for a marshall 36W amp.

Primary: 230V @ 50 Hz
Sec. 1: 600 V C.T. @ 200 mA
Sec. 2: 6,3 V C.T. @ 5 A
Sec. 3: 0V / 5V (@2,5A) / 6,3V (@2A)

[Vdelli]

Hi,

I tried to change the EL34 fixed biased schematic to a 6L6 cathode biased schematic. I looked at some Fender stuff wit 6L6 cathode biased.



Please tell me if this is right or total bullshit 


With best regards

 

[sluckey]

Looks right.

[Vdelli]

Thanks sluckey!

Wich power transformer did you use for this amp?


With best regards

[sluckey]

I never built it. Hoffman's 'Marshall Style 50 watt Power transformer' would be nice if using a pair of EL34s.

[Vdelli]

Okay!

A friend told me, that I have to use 270V platevoltage to get around 25W Power with 2 6L6 in cathode bias Mode. What do you guys think?

with Best regards

[tubenit]

Both of my amps with cathode bias using 5881 or 6L6 at around 360v gets around 23 watts.

I measured the output based on the method that Sluckey describes in Reply #1 on this thread from ARCHIVES about measuring output wattage:

http://el34world.com/Forum/index.php?topic=2291.0

With respect, Tubenit

[Vdelli]

thanks Tubenit,

I'm sorry, that was my fault! He told me to use a 255-0-255 V or 260-0-260 V transformer to get around 360V after rectification with a SS rectification.  The problem is to get a 255V or 260V transformer with enough amp. The best transformer I found is a Vox AC30 transformer with 270-0-270 @ around 200mA.

[Vdelli]

Hi guys,
sorry for the long brake here. I was working on an other amp. A friend of me loved his Jet City JCA20HV but it burnt down after a few month on the road. So I sad to him that I can build a stable one if he like. I used a Hammond 369JX powertransformer and 1750PA 18 watt outputtransformer. So the amp delivers real 17 watt with 350V on the anodes. The amp is not exactly the same like the original. I did some changes, I added a 1M depth pot instead the switch an added a switch on the rear to switch out the cathodebypass cap on V2 for a little bit more headroom and less bass.I learned a lot new things while building this amp. I draw my first layout out of a schematic and stuff like this. Before, I only used finished layouts from ceriatone for example.

So this is what came out:

[Vdelli]

some more pictures...

[Ritchie200]

Wow!  That is a beautiful build!  Very nice job.  Do you have any sound clips?

Jim

[sluckey]

Very nice! Inside and out. Good job!

[Vdelli]

Thanks guys!

Sluckey, the layout of your Marshall Dual 50 was a big help to do this layout 

I just finished this amp 3 days ago. Yesterday I had the first chance to play the amp on high volumes and it sounds not that good. It gets fizzy with  thin overdistortion. So I checked all the Voltages again and saw that the negativ grid voltage on g1 was to high. It shows -19,7V/-20V. In the most jca20HV there are arround -15V. So I put a 7k5  resistor in to get -15,3V. Now I get only max 15mA for bias. The amp sounds much better but don't get very loud. Today I try to make the bias higher....

[Vdelli]

I fixed the problem.
The original Jet City transformer use a 27V  bias tap, the Hammond use a 50V tap, so the negative voltages were too high. The next problem was a bad volume pot. Now I'm happy how the amp sounds.
In the next 2 weeks I have to move to a new aparment, after that I do some soundclips.


After moving to the new apartment, I will go on with my first 2 channel amp, based on sluckeys Marshall Dual 50. A couple weeks ago I played a JCM800 clone with KT66 power tubes. That was one of the best JCM800 sounds I ever heard...A little less agressive and more woody/warmer....Very nice! Maybe I will try that too....