The Sluckey Marshall Dual 50

[shortfuse]

 Ok its been a while since I have built something and I am gearing up to start a new project and will need some help and opinions (good bad or indifferent).  I have been intrigued with Sluckeys dual pre – amp design http://home.comcast.net/~seluckey/amps/misc/Marshall_Dual_50.pdf for a few years now and was going to build the 50w version.  But I started playing out again and now it seems 50w is too loud for venues we will be playing and even at practice sessions.  I am having to use an attenuator with my Hoffman 50w 2034 and my dsl 50 it does the job but I just don’t like them.  I contemplated Tubenit’s TOS which I will probably build after this amp as a 112 combo but that’s another project (that one has been on the list for a few years as well).So I contacted Sluckey and inquired about cutting out the 50w power section and replacing it with a 36w section and ½ power switch.  The ceria tone 36w amp came up as an option http://ceriatone.com/productSubPages/BS36watt/BS36W_Complete.htm I am also looking at his November project http://home.comcast.net/~seluckey/amps/november/november.pdfas it has both fixed and cathode bias (just another bell and whistle).  Other things I am wanting to add to this build is switchable diode / tube rectification, and Effects loop.I see there are several OT transformers available for 4) EL84’s but they all vary from 4, 6, & 6.6k for 4, 8, 16 taps.  What is the difference going to be with the overall sound and performance?  Recommendations, brand and model # Please.

Will post layout when I complete it.

 

[SILVERGUN]

My 2 cents..
Since you're building from scratch, you could get 36 watts from a cathode biased pair of EL34's if you want.
Put VVR on the power tubes with a PPIMV in front of them and you have ultimate output control.

Tell us more about why you want what you want and what type tones / response you're looking to get out of the amp.

 

[sluckey]

This is a set of ClassisTone iron that's being bundled and sold for Vox AC-30.

     http://www.classictone.net/40-18049.pdf

     http://www.classictone.net/40-18050.pdf

     http://www.classictone.net/40-18043.pdf

I like Silvergun's suggestion too.

[shortfuse]

Well SG I knew this would happen I waited until I thought I knew exactly what I wanted to do and now you got me thinking again which is what I was looking for in the first palce.
If we went with the EL34's I could stick to the same design.  But on the flip side running the 4 EL84's may work better on the plexi side with natural break up earlier.  Head room break up Head room break up.  Too many choices.
The 800 and the plexi are my 2 favorite amps I have one of each in separate heads but lugging them around with a head switcher and a stereo 412 is a PIA.  Now the newest delima is the shear volume at which we are playing at.  I think I can achieve close to that tone at lower levels with the EL84's and with the half power switch gets me to 18 naturally but I guess I could do the same with the EL34's.  I have never played an amp with a VVR read a lot about them in the TUT books and always wanted to try it but never have.  I just know I am not real fond of attenuators they do the job some better than others but it's just not the same tone.  I like the word bloom that Tubenit uses sometimes the sound just does not bloom the same too me and sounds very compressed.  I even just tried my friends new Rivera rock crusher and it is very good just don't like it.



Steve that may be a good set to utilize for this experiment.

[printer2]

Not like an extra preamp tube will hurt, but I drew this up for myself to get both amps in one package.

[tubenit]

I like Silvergun's suggestion too.

I do also!  With respect, Tubenit

[HotBluePlates]

If we went with the EL34's I could stick to the same design.  But on the flip side running the 4 EL84's may work better on the plexi side with natural break up earlier.  Head room break up Head room break up.

Which distorts first: Tube A with 36w of clean output or Tube B with 36w of clean output?

There may be minor tonal differences between the tube types, but you'd use 4x EL84's or 2x EL34's. If the power supply and output transformer allow 36w of clean output, each has essentially the same "headroom" or volume from the speaker before the onset of distortion.

This is also true of 6L6's and 6V6's. "The 6V6 is the smaller output tube, so it has less headroom, right?" But 4x 6V6's get just as loud before distortion as 2x 6L6's...

[shortfuse]

Ok so Dave has a good idea and some pretty respected opinions say  "I kike SG's suggestion too" and another respected opinion is politely telling me it is going to make no difference for head room and break up.
So this would mean I could utilize Sluckeys plan as is and just use a 36w OT instead of the 50.  Or because I would be utilizing the VVR and the PPIMV just keep it all  as a 50 because it will achieve the same thing (this would be the best scenario for me)
If I was going to use a VVR would I use this one http://www.londonpower.com/power-scaling/ps-kit-cathode-bias along with this http://www.londonpower.com/power-scaling/voltage-clamp-kit or this one http://www.londonpower.com/power-scaling/two-thirds-power-scaling-kit-tube-amp or http://www.londonpower.com/power-scaling/two-thirds-power-scaling-kit-tube-amp or is there another VVR that works better.  Looks like I will be getting back to TUT again today and doing some more studying.
The PPIMV goes between the PI and the Grid of the power tubes correct?  Sluckeys design is PPIMV?  Most I have seen in schematics are are dual 250K pot but Printer2 has them in his schematic above at dual 1M?  Is the dual pot a better way of installing?  If so i would have to do a little design change to the layout but I dont think thats a big deal.
SG you are taking me to uncharted waters.....  But I like it, this is why I love this amp forum.

[printer2]

I have 1M in the schematic because that was the value of my dual pots on hand. I ordered some 250k pots and will be using them when they get here. One of the guy's at work installed the SV2 kit in his 18 Watt, made a mistake in wiring, and I should hear how he likes it on Monday.

[SILVERGUN]

Ok so Dave has a good idea and some pretty respected opinions say  "I kike SG's suggestion too" and another respected opinion is politely telling me it is going to make no difference for head room and break up.
So this would mean I could utilize Sluckeys plan as is and just use a 36w OT instead of the 50.  Or because I would be utilizing the VVR and the PPIMV just keep it all  as a 50 because it will achieve the same thing (this would be the best scenario for me)
If I was going to use a VVR would I use this one http://www.londonpower.com/power-scaling/ps-kit-cathode-bias along with this http://www.londonpower.com/power-scaling/voltage-clamp-kit or this one http://www.londonpower.com/power-scaling/two-thirds-power-scaling-kit-tube-amp or http://www.londonpower.com/power-scaling/two-thirds-power-scaling-kit-tube-amp or is there another VVR that works better.  Looks like I will be getting back to TUT again today and doing some more studying.
The PPIMV goes between the PI and the Grid of the power tubes correct?  Sluckeys design is PPIMV?  Most I have seen in schematics are are dual 250K pot but Printer2 has them in his schematic above at dual 1M?  Is the dual pot a better way of installing?  If so i would have to do a little design change to the layout but I dont think thats a big deal.
SG you are taking me to uncharted waters.....  But I like it, this is why I love this amp forum.

If it were me and I was going to use 2 EL34s, I would go with the 50w JCM OT. I suggested cathode biasing because VVR is easier to install and the power tubes will "self bias" as you change the supply voltage.

Your OT choice depends more on what output tubes you will be using more than how much power you want the amp to put out. You want the OT to be able to handle the max. power out of the amp, with or without VVR.

Yes, the PPIMV goes between the PI and the power tubes.
My reasoning for my suggestion is that it offers you the best of both worlds by allowing you to control the potential output of the power tubes PLUS control the amplitude of the signal you're feeding those tubes.....

So it kinda seems like you could set it up either way:
- VVR set down low on the power tubes and a big signal going in will get you more breakup, while VVR set high and a smaller input signal should get you more headroom

Here's a little PDF that I picked up recently that should help:

[Willabe]

The 2/3's Power Scaling is really for BIG amps where trying to scale down a 200w to 400w amp results in too much heat in the mosfets, so Kevin just scales the screen grid for a more economical way to PS a big amp.

Your really not going to need to turn down a 200w to 400w amp to a whisper, just use a smaller amp.


               Brad     

[HotBluePlates]

Your OT choice depends more on what output tubes you will be using more than how much power you want the amp to put out.

Respectfully, this is a common misconception. I've started a new thread to help explain a better way of looking at the OT and output tube pairing.

[jjasilli]

The problem you post is the same old same old.  Enough wattage for clean headroom - amp is too loud when it overdrives.  Overdrive at lower volume - not enough clean headroom. 


"Solutions" are pedals; attenuators; di; mic the amp and use a PA system; get overdrive in the preamp and use a master volume; KOC single ended mod; power scaling; VVR; etc. 


Volume is logarithmic - factors of ten.  Twice the power is 10 X the power (wattage).  So 1/2 or 1/3 the wattage is relatively  insignificant.




 

[HotBluePlates]

The problem you post is the same old same old.  Enough wattage for clean headroom - amp is too loud when it overdrives.  Overdrive at lower volume - not enough clean headroom. 

"Solutions" are ...

Yep.

Or a clean amp and a lower power dirty amp. I once had a setup of a Princeton Reverb and a '54 5B2 Princeton with an ABY pedal. The tweed amp was well-distorted at the same ear-volume as the Princeton clean, and the small amp's midrange filled in the scooped mid of the big amp nicely.

Instant small-scale SRV tone.

[SILVERGUN]

So shortfuse,
I hope we haven't confused you more than helped you....
I know how it can be when you're trying to make decisions, and you ask for help / opinions,,,and then you get some and they just create more questions.

Keep telling us what you're thinking and hopefully we can help you more than hurt you.
 
Personally I'm sorry for the mis-information, and I'm glad we have HBP here to keep us thinking correctly.
For the record, what I was suggesting was to settle on which output tubes you were going to use first,,,based on how you want the amp to sound.
And leave enough wiggle room in the OT just in case the VVR starts slowly creeping it's way out of use, and you wind up with the max.
 power that your output tube choice could possibly produce.....and since you're basically hoping to clone the sound of 2 Marshalls that I normally associate with EL34s, I just figured you would use that OT, with those tubes.

I think your plan of using sluckey's dual pre-amp makes sense, and if the guys liked my idea of 2 cathode biased EL34s, then that sounds like a good plan.
From here,,, if you keep asking questions,  I'm sure we can all help you get the details sorted out....
If you're sold on 4-EL84s,,,then that's OK too, and nobody would want to railroad you into any one specific choice.

So I guess i'll ask a question for both of us:
If he wants the classic Marshall tone and he uses 2- EL34's with max plate voltage at 460vdc (because he uses the "standard" JCM PT), but has VVR installed and will have the B+ reduced "most" of the time,,,is there a better choice for primary K on an OT?.....and, should he still use a 50watt'ish OT just in case he wants to use the amp at max. power occasionally? ....and can we give him an example of an actual OT to purchase?

Or, does it make more sense to use a lower secondary PT voltage and just limit the potential max. power,,,and therefore change the specs of the appropriate OT even further?

Volume is logarithmic - factors of ten.  Twice the power is 10 X the power (wattage).  So 1/2 or 1/3 the wattage is relatively  insignificant.

One thing you can take from that is...
Your not gonna notice much difference at all in max. volume between a 36 watt amp and a 50 watt amp...they are both loud...a decibel or 2 isn't gonna be the difference in preventing hearing damage for the guy in the front row

[SILVERGUN]

I spoke with shortfuse briefly and this was one of the options he is considering for adding VVR to his cathode biased build.
The cathode biased version is at the bottom of the page.
He is most interested in simplicity and reliability, and is only concerned with having VVR control of the power tube voltages.

http://www.hallamplification.com/main.html?src=%2F#2,2

[shortfuse]

 Dave
 Even though I thought I finally had it down to what I wanted to build when I made the 1st post.  I fully expected someone to rattle my cage and make me rethink the whole build.  Some forum members I have a very high respect for chimed in and helped in my prelim decision making process.  And a special thanks for all the offline answers Sluckey has provided me with this design over the past 2 years on and off.
BTW the whole thread HBP started is great, informative and a huge help as well Thanks HBP.

 That all said I have decided to go with Sluckey’s full design the EL34's and full 50w iron package.  Going to try the VVR and see what it will do.  If it sounds like and attenuated amp I will pull it off and just keep it as a 50w amp.  It will still get used every Thursday if I like it.  If the VVR thing works well it will get used 3 times a week.  So it will be a win win if I like it with the VVR.  I fully understand the whole its only 2db difference.  But if I wanted a 50w amp it think it sounds better as a 50w amp not a 100 at ½ power.  Same with a 36w and 18w I guess.  Gut tells me I should build it as a 36w for what I need right now but I will learn new things in the process, build the amp that has been on my next to build list and maybe I will be pleasantly surprised with the finished product.  But those are topics for another day I want to move forward on this build.
Do I need to adjust the layout for the dual pot PPIMV?  I think I asked this before but isn’t Sluckeys design a PPIMV?  Just not a dual pot?  My still a rookie status is going to become very evident in some of my questions.
 
I have to read some more on the VVR stuff.  What are the pros and cons to VVR the whole amp opposed to just the Output tubes.  Is one going to work out better than the other for this build?  If I remember correctly Tubenit pulled his VVR from the TOS because he thought it sounded better with out it.  Again Pros and cons on the VVR please.

Also now that I am not making it a 36w can one of the Moderators change the subject or topic to "The Sluckey Marshall Dual 50" Nevermind it did it when I modified the 1st post.
 

[sluckey]

I think I asked this before but isn’t Sluckeys design a PPIMV?  Just not a dual pot?

The master volume on my amp is exactly like the stock MV on a JCM-800 2204 amp.

If you want to also use a PPIMV dual control, you wont have to change the layout.

[HotBluePlates]

Personally I'm sorry for the mis-information, and I'm glad we have HBP here to keep us thinking correctly.

No, you were giving him good advice. I like the part about "copy the known Marshall plan with these transformers, which also work well with VVR." Might as well make it as to-the-point as possible, especially when the overall goal seems to be focused on preamp changes, not the power section.

[SILVERGUN]

I still like the idea, and I'm glad you are gaining some clarity.
If I wanted to build this amp I would be thrilled to have the luxury of using sluckey's work....I have learned that it is much easier to follow the paths of the guys that have been down these roads before us, and have taken the time to document their work to the point of near perfection. It will take a lot of the stress out of an already stressful hobby.

Keep asking questions and we will get you to where you need to be....it will not be difficult to add the PPIMV to sluckeys amp

Here's a schematic of a common application...see if this makes sense

[alerich]

Going to try the VVR and see what it will do.  If it sounds like and attenuated amp I will pull it off and just keep it as a 50w amp
 
I have to read some more on the VVR stuff.  What are the pros and cons to VVR the whole amp opposed to just the Output tubes.  Is one going to work out better than the other for this build?  If I remember correctly Tubenit pulled his VVR from the TOS because he thought it sounded better with out it.  Again Pros and cons on the VVR please.

I built a 2x6V6 cathode biased amp that is essentially a clone of the Marshall Studio 15 amp (with cathode bias). I installed the Dana Hall VVR. I have a THD Hot Plate and a Weber MASS attenuator and the VVR definitely does not sound like those. The VVR doesn't exhibit any of the frequency anomalies (like the high end rolling off) that I hear with my attenuators under heavy attenuation. It took me a little while to get used to it and to reacquaint myself with it every time I fire that amp up.  It really does do just what they said it would - it takes whatever your basic tone is before you begin to dial in the VVR and makes it "smaller". Having said that, I can see how it would be an acquired taste and not suitable for everyone's palate. It's really one of those things you're going to have to try and see if it suits you.

Of course, any time you push less volume through the speaker it will impact your tone when you use any attenuator but I feel that the VVR stays clearer and puts out a much truer representation of my starting tone than an attenuator does. I was mesmerized by the VVR when I first installed it. I would run it up and down and marvel at how it worked. I really should install one of the bias tracking versions in my JCM 800 clone. That is one hella loud amp.

One thing I have noticed is that the VVR circuit does drop a little voltage across itself even when the voltage output is set to max. If it is installed in an environment where every volt counts it might be worthwhile to include a bypass switch that can remove it from the power rail entirely.

[tubenit]

I will offer my 2 cents worth.

To control volume without losing/changing tone, ................. an active FX has been the best choice for me. Besides allowing reverb or delay, it is a superb master volume. 

Geezer has a You Tube he did to demonstrate this, so you could PM him for a link to it. He demonstrates that you can preserve tone down to a whisper. Sort of like a stereo dialing down a cranked ZZ Top tune without ever changing tone.  Geezer uses a D'Lator.

I seriously doubt that I will ever build another amp without on board active FX.

The D'lator is an external option for this that the Dumblish cloners use to get 100w amps at bedroom volumes and maintain good tone. Going that route, you could use Sluckey's layout and passive FX jacks.

Second place is PPIMV for me.  I have built one amp with active FX & PPIMV.  PPIMV loses good tone below "6" in my opinion.

VVR is also good and I was happy with it.  This may be the best option for home recording?  However, below 4, it sounds kind of fizzy. And the tone does change slightly dialing from 10 down to 4. Still, I thought it was useful and worked well.

With respect, Tubenit

[shortfuse]

SG thanks again for your input thoughts and opinions. 

Aldrich you hit the nail on the head with the attenuators I have the same two.  THD much better at retaining tone in my opinion only, glad to hear you say VVR is not like them.  I will build the amp with provisions to install VVR but will have it where it can be pulled out if I don't like it and just leave it a 50w amp.

Tubenit I'm listening one of the things I want to do is put in an on board active loop.  I plan on using a a large chassis like a JCM 800 or DSL type the full with of the Marshall style large box.  So I will have room to work and add this in.  Would it be possible to shoe horn a D'lator in the build?  Or go with what you have drawn which I assume is similar to the TUT BFX which I am installing into a 1959HW this week so I will be able to see what that does.


PM sent to the geezer

[tubenit]

Would it be possible to shoe horn a D'lator in the build?

I don't see why not? 

Here is one example of a layout for the active FX.  And there are numerous other ways of laying this out. I probably would create a layout that is consistent with Sluckey's layout format.

With respect, Tubenit

[tubenit]

Here is Geezer's video showing the remarkable effectiveness of his D'Lator as a master volume preserving the tone over a wide range of volumes:

https://www.youtube.com/watch?v=Vny1G1JucXQ&app=desktop

And there is a thread here where he shares more info:

http://ampgarage.com/forum/viewtopic.php?t=25195&postdays=0&postorder=asc&start=0

With respect, Tubenit

[shortfuse]

 I watched both videos and now you have peaked my interest even further.  Gotta add DaGeezer is a player too.  Very nice clips.
With this I could leave the whole design as is, insert the active loop and most likely knock it down for what I need.  I don’t ever think I would have it at bedroom level, I have other amps and a rack unit for bedroom level and mp3 jamming.  In your design above the switch (also on the front) allows for true bypass as well?  I also notice your designs have the send return controls on the front of the amp great for access on the fly. 
The wheels in my head are turning.  Thank you for the suggestion.  I have so more deciding to do but I think I will be ready to order parts by the end of the week.

 

[shortfuse]

Playing around with Sluckeys Shapes tonight my vision so far.  Jeff do I need the recovery knob for it to be a volume control?

[tubenit]

I am going to suggest looking at the JPEG, the schematic and layout under post #5 on this thread regarding the D'Lator:

http://el34world.com/Forum/index.php?topic=10624.0

It should have enough information for you.  Geezer's is EXACTLY like the one in that post.   

With respect, Tubenit

[shortfuse]

 I think I am going to go with the on board D’lator that way I can keep everything in the board layout design the same and just insert it on a longer board between the Tone Driver and PI,  just need to make the board a bit longer.  This should not be an issue with a 27 X 8 X 3 chassis I intend to use.  I have not fully decided on this yet I may stick it down at the far end of the chassis on its own board and put it the knobs on the back as a normal loop would be.  But inserting it on the board as aforementioned with all controls on the front is growing on me.

Will a typical Marshall JMP/800 50w PT be able to handle adding this on board?
 

[tubenit]

I strongly advise to at least have the FX return on the front chassis panel. It is used as a master volume.

To me this is an essential "must have" with the FX loop.   The exception to that would be if you had a PPIMV pot on the front of the chassis, however ......... I still want the FX return on the front.  Both my amps have the FX send on the back chassis panel,  but the FX return is on the front panel.

I adjust the FX return pot on my amps more than any other pot control. Almost everything else is a "set and forget" for me.  I use the FX return to control the amp volume.  Note how Geezer used the FX return knob on his video demo.

Regarding adding another tube and the PT.  I attached a "data cheat sheet".  Look at ma of tubes ........ add it up....
look at ma rating of the PT.

With respect, Tubenit

[SILVERGUN]

I strongly advise to at least have the FX return on the front chassis panel. It is used as a master volume.

To me this is an essential "must have" with the FX loop.   The exception to that would be if you had a PPIMV pot on the front of the chassis

I just want to confirm what T is telling you here....
I have had the same positive outcome in my last amp by using the effects return pot as a Master Vol, and actually just wound up labeling it Master.
If you want the loop anyway, this is the way to go IMO.

By going this route you may not need the PPIMV 
Sorry to add another question to your list.

[SILVERGUN]

Will a typical Marshall JMP/800 50w PT be able to handle adding this on board?

Another thought......
If you use this PT it will enable you to use a low/high power switch that would act like two preset VVR points by using the lower voltage 560Vct winding for the low setting and the 690Vct tap for the high power switch setting.
http://www.classictone.net/40-18095.pdf

Hope this isn't TMI Steve

[Willabe]

That PT is only 150mA for B+.

I think that's a little low for a 50w amp?


            Brad     

[SILVERGUN]

That PT is only 150mA for B+.

I think that's a little low for a 50w amp?

I'll have to defer to the experts on that one...
I always use this current calculator :
http://www.dreamtone.org/Calculate_Current_Form.htm

Can anyone confirm the general accuracy of it?

If the calculator is correct and you enter 345-0-345 with diode rectifier, 2- EL34, 5- 12ax7, it comes out to 147.9mA

[shortfuse]

That PT is only 150mA for B+.

I think that's a little low for a 50w amp?

I'll have to defer to the experts on that one...
I always use this current calculator :
http://www.dreamtone.org/Calculate_Current_Form.htm

Can anyone confirm the general accuracy of it?

If the calculator is correct and you enter 345-0-345 with diode rectifier, 2- EL34, 5- 12ax7, it comes out to 147.9mA

With SG's link
Current Draw
 

  Your HV Current Draw:    145.7 mA

Your 6.3V Amperage:    4.2 Amps

Your Rectified Voltage at first capacitor:    469.2 VDC

Subtract 6 Volts if using a choke before first capacitor    

( +/- 8 Volts Tollerance )    

You Selected: 345-0-345   

[shortfuse]

I have call on a decision making buddy this evening.

[PRR]

> this current calculator ...Can anyone confirm the general accuracy of it?

Medium to none.

It isn't wholey wrong because most good(?) amp designs stay close to a pattern.

It does not ask what your OT impedance is. That is THE determining factor in power stage current (which is 98% of total amp current).

Compare:

two 6550
Your HV Current Draw: 183.5 mA
Your Rectified Voltage at first capacitor: 582.2 VDC
You Selected: 425-0-425

With actual factory values for 6550:
http://www.mif.pg.gda.pl/homepages/frank/sheets/135/6/6550A.pdf
top-right page 3
This suggested condition is 303mA at 600V, so 183mA at 582V is unlikely.

However it would be ~~183mA if the load were 8,200 instead of 5,000.

It isn't that hard to LOOK-UP factory data for the tubes, loads, and voltages you will be working at. If there isn't anything quite like your condition, you can extrapolate a bit. If two 6V6 with 8K suck 105mA at 285V, it might be 129mA at 350V. However if you find yourself far outside the factory suggestions, you may be in trouble.

[alerich]

The active FX loop and the VVR are two different things. The reason the active effects loop acts like a master volume is that it is basically just a master volume. Take the JCM 800 2204. They hang a master volume pot off of the treble wiper. The active effects loop adds two more tube stages and then... hangs a master volume off that. It's not essentially that different in theory to those little magic boxes they sell on eBay that you can plug into your effects loop and have a pot inside. Just more components. Everything after the effects loop operates exactly as it would without the effects loop. It's a buffered master volume.

The VVR is dropping the operating voltage globally across all of the power supply nodes. My VVR equipped amp is basically a lower wattage JCM style amp. I play it with everything dimed and then roll back the VVR to taste. I think my playing style and tastes differ a bit from the rank and file here. I ordinarily play hard rock loud enough to wake the dead three counties away. With the VVR everything is cooking. With the active FX loop everything after the loop is just idling as it reproduces this small "master volume-ized" signal. If you are playing like what is heard in the you tube clip above then you really don't need a VVR.

[shortfuse]

I have decided to build a stand alone d'lator and try it out with other amps I have.  Plexi and JCM 800 and see how it actually does work and sound then fall back on this thread because I am going to build the Dual 50 either way.

Alerich
Which VVR did you use?

[alerich]

I bought a small VVR board from Dana Hall but many guys just build them from scratch. The amp is about 20 watts and is cathode biased so it didn't need bias tracking. Truthfully, the amp I installed it in really didn't need it for my playing situation. It's loud into a 4x12 but not obnoxiously so. I was just intrigued by the idea and wanted to try it. My JCM800 50 watt clone could probably benefit from a VVR. That would involve a bias tracking feature and honestly there isn't any room in the chassis for it anyway. I use a Hot Plate for that one when I need attenuation. The Hot Plate is my favorite of the attenuators I have tried so far.

[Mike_J]

Your chassis is pretty big so I would Include the DLator in the amp.  You can probably add it for about $40 in parts.  Only need one tube (12AX7 or 12AT7s are commonly used.)  As a stand alone unit it would be hard to make one for under $200.  I have liked what it has done on all the amps I have used a DLator on.

Mike

[Tone Junkie]

Mike_J SG fine tuned it to use a 12au7 which they all thought sounded the best. In my hotrod marshalls when i had a left over triode section I have used the back end of the D'later for the master volume and recovery and really liked it to. Thats my current favorite master volume at the moment.
Bill

[drew]

Ampgarage thread about a Dumble-style build with onboard Dumbleator and loop-return-as-MV: http://ampgarage.com/forum/viewtopic.php?t=20551&postdays=0&postorder=asc&start=0