Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Archives of favorite topics => Topic started by: phsyconoodler on October 18, 2007, 01:31:37 am
-
I finished my 'overdrive rocket today,and it sounds marvelous! It has a sweet clean tone and a thundering overdrive.I have 6V6's in this one with Hammond Transformers.sounds likea *umble should.Cleans have tones of headroom and the overdrive is from mild to over-the-top insane.Sustains for days.
I'm really happy with this one!
-
Another shot.
-
I've built two...one lite and one full blown umblot with all the relays and bells and whistles. They are great amps and the lite is, hands down, my main amp now. I can walk into a gig carrying all my gear in both hands. I run a little delay through the effects loop. I keep the overdrive channel on and I don't touch the amp again. I just use the volume on my guitar. Nice looking build too!!
-
The channel switching is done with mini switches right now,but I want to put relays in there to make it foot switchable.This chassis is a small one I had laying around but the relays are relatively small so I'll see if I can cram them in there.The board is a glass/epoxy one with hole drilled in it.This circuit really is brilliant,I can see why people like it.The cleans are quite impressive,but they don't excell for rythym work.The notes jump out at you when you dig in though.It doesn't distort on the clean channel until you pin it and the overdrive is very pleasant sounding.If you play lightly it seems to be muted a little.It needs to be played a bit aggressively to make it really shine,but it does indeed shine when pummeled.The orange drops are mallory and they seem to be a mate to this amp.
Now off to make a head box.....
-
Sorry bluez!She's married!
-
Go to www.brownnote.net .The layout and schematic are there.
-
It took some looking, but I found one in their forum>>>
http://www.brownnote.net/forum/viewtopic.php?t=274
-
Which particular Hammond transformers did you end up using?
-
I used a 272HX and a 1650H.
Here's a shot of it in it's headbox.Excuse my lousy photography.
-
Black goop on a clone?
I really need a new camera or a lesson in photography!Here's the last shot.
-
Here's one I prepared earlier. ;D
It's as small as I could go with a 12" speaker 17" x 15.5" x 9".
Added a switchable Fender clean channel, called it the vintage channel and the Dumb side modern channel ( because I lack imagination and originality).
I used relays for channel, preamp boost, overdrive. It does 'pop' switching between fender and dumb so will have to sort it out .
-
That is one great looking combo!
I built my own chassis and it's considerably smaller that the D'Lite chassis,consequently I can't fit the channel switching relays inside the chassis.I'm putting them outside the chassis.I originally planned on a 2-10 combo but I wanted to hear the amp before I built the cabinet,so I stuffed it into this head I threw together one morning.I'm overwhelmed by the tone of this circuit!
A friend came and tried it out and made me an offer I couldn't refuse,so it's sold.I'm building another now and won't have any reservations about building a combo.But the speakers will be paramount I think.It sounds lovely with greenbacks,but maybe a G12H-30 would be better,or a couple of Eminence 10's.
Thanks for your kind words phsyconoodler but yours is a much nicer build. I too
made a chassis from an offcut of alu' I had laying around. Used a hammer and 4x2 block off wood , so it's very rough. Much easier to buy one from mr hoffman imho. This whole build came about to use up leftover parts and make an amp that was small and light.
Your idea of putting relays on the outside of the chassis may be the cure I'm looking for. I think this amp has high freq' osso or crosstalk between clean channels. I turn either volume or treble knob on each channel past 12o'clock and it squeels like a cut pig. Hence all the shielded wire( which will come out eventually as soon as I can cure it). With the relays on the outside it might make for better leaddress ( I've never had or heard hi freq' osso before). I'm also thinking the unused channel may have to be grounded when switched out, I don't know but it's a learning experience. I think the best speaker for a D amp is the EV. I have a couple which I'm saving for future builds ( I can't afford them really), I AB'd them against many other speakers and for this type of build there is no equal. I guess that's why he used them.
-
Any features on the amp that did NOT impress you as a "must have" feature like the PAB
(pre-amp boost) or treble boost or .............. ?
Could anything else be removed to go from Lite to Ultra (Lite)?
For example I found I don't change presence knobs much so my last build, .... I just used a resistor and cap and lost the pot.
Anything beside have it relay switchable that you'd do different?
With respect, Tubenit
Hi Tubenit.
On my build I ditched all the preamp switching. Bright, mid boost, jazz/rock, deep, LNF ect. as I never use it ,interesting in it's day I think but now days I think guitarist want it at hand ( built in guitar). There's so much diversity in guitar manufacture and add on parts, pickups ect today. If you took the time you could simplify it down to what's really needed for good tone and ease of use. Like you say about about the presence pot , not needed if you don't use it. I did a recap on a mid '60s bassman head for a customer last week, had to change a couple of noisy 1watt 100k CC plate resistors as well (used allan bradleys). Plugged it in to a box with a 12" eminence speaker and played a cheap asian strat copy. I was gobsmacked with the sound. It felt great,played great, sounded great. Now I want one. Leo was a genius.
-
Yeah i agree.Leo was a genius.I really love bassman heads like the AA864.Killer!
This *umble lite however is really brilliant too.I don't use the mid-boost in this amp but have the OD and preamp boost which just lifts the tone stack.It is useful for some music.The overdrive is thick and surupy and sustains for days.It does a good classic JCM800 rock tone without the brashness the marshall gives.Lead dress is important for quiet operation but I only have one shielded cable to the input.Mine is relatively quiet.
-
What brand caps are the blue ones on the left (I'm assuming filter caps)?
(http://www.el34world.com/Forum/yabbfiles/Attachments/guts.JPG)
Regards,
Dyna
-
These amps look good in red . . .
-
Hey Drew, Are those two red boxes behind the preamp switches the switching relays? It would be great if you can post a picture of that area . Thanks Punky
-
Those are the switching relays.There are real clear pictures on the Brownnote site.
I just finished my relay and power supply boards and I'll post a pic when they are installed.Mine will be in different locations than the brown note build and I used 6.3v for the relays with a regulator.
-
Here's a shot of the relays.
I made the relay board months ago. Since then, guys have been going to triple-relay systems (bright, OD, PAB with a three-button footswitch, or a two button footswitch controlling PAB and linked OD and bright), and PCB's have been made available. If I had it to do over again, I would have gone that route.
-
Thanks for that info Drew.
-
Psycho,
Another VERY nice looking build there. Likewise for the other D'Lite examples in this thread!
I notice that you didn't go the MF plate resistor route on yours. Many of the folks building these believe that they are a part of the required "magic" for the D tone. Any thoughts/comments/experience that you could share on that topic?
I threw mine together and stuffed it into a Bogen enclosure many months ago and have been tweaking/experimenting with all of the various mods and changes being discussed ever since. Finally ended up with the Bluesmaster/Dogears mods and am extremely satisfied with the results. Currently using a 1X12 Avatar oval back loaded with a G1265.
Somewhat outdated thread here:
http://www.brownnote.net/forum/viewtopic.php?t=382
I have since cleaned it up quite a bit.
Played my first gig with it this Saturday (Blues/Classic rock covers) and was very pleased with it's performance! Very full, round and 3D'ish tone. Liquidy, "sustain for days" OD tone to die for.
A couple of strangers (and fellow guitar playing bretheren) were, well....dumb-founded.....by the fact that I was using only a single amp and a single 1X12 cab. They were convinced that I had a microphone hidden somewhere in the cab and was piping it out to the PA mains!
I am not sure that the purists would give it the thumbs up for nailing the D'tone. But, it certainly is a unique sounding and enjoyable to build and play plan.
Dave O.
-
Sorry about that!
There was a lot of discussion on the use of metal film resistors on V1 and V2 plates at the BrownNote and AmpGarage forums back at the beginning of the year when the D'lite plan "hit the street". IIRC, the Vishay Dale RN65D seemed the gold standard for this application. Most of the experienced D'guys felt that they were an important part of the puzzle.
I am not smart/experienced enough to be skeptical so I just followed suit.
Just wondering if you had a strong opinion one way or the other about their use.
Thanks much,
Dave O.
-
These . . .
-
I'll have to read that thread.I can't possibly imagine what difference the 'type' of resistors have to do with anything here????
-
Phsyco,
Like I said, I am not smart/experienced enough to provide any useful info/data on this topic.
However, I know that MF use was discussed/debated/"tested"/etc frequently on a couple of the other forums.
Here is just one example over at the AmpGarage forum:
http://ampgarage.com/forum/viewtopic.php?t=2884
I don't think that this excercise was totally conclusive though.
My understanding is that HAD utilized MF's exclusively(?) in certain locations/applications. Hence, their use became one of those pieces of the tonal puzzle that should be reproduced when trying to obtain that D tone (whatever "that" is!).
It is my understanding that every D is a little different and, as we all know, an amp's tone is to a certain extent due to the interactions of the various components. So it is nearly impossible to point to a single component and say "this is why it sounds like that". That would be way to simple.
Anyway, when the hobbyists like me see the respected experts like you leaning in a direction believed to be different than the "herd", it becomes worthy of a question or two. Call it looking for enlightenment! I was just wondering if you had contemplated this topic.
Thanks much,
Dave O.
-
hey phsyco, I am building one of the umbolt also, and was wondering on the hammond tranny there is no bias feed. I was wondering if you used the same bias setup and resistor values as the schematic bias becuase i am gonna have to feed the bias off of the 300v secondary. any help would be great. thanks, Jgriffes
-
If you look back at the pictures you'll see a little board above the main filter cap board.That's where the bias supply boartd is.It is identical to a Marshall 2203/4.I just had to alter the range resistor to get the bias in the right range for the 6V6's.
-
thanks aton, I figured thats what you did but it's kinda hard to see from the pictures. What value did you end up using for range resistor? (I plan on using 6v6's as well, I haven't built one with them in yet so I figured I'd give them a shot.) Thanks again.
-
It depends on the PT you are using.I think I ended up with a 65k range resistor,but yours may be different.I can bias for any octal tube now.KT77's are particularly tasty sounding,but 6v6's are the best for my particular transformers.
-
I've just noticed that I somehow ended up using a 1/4 watt, Vishay Dale RN65C (instead of the 1/2 watt D) 121K resistor on V2. :( Is this a high-priority item to change out?
-
there is no 121k resistor on V2.If you are referring to the 120k plate resistor,it has to be at least 1/2 watt or 1 watt would be best for plate resistors.
-
Here's a shot of my latest Overdrive rocket with reverb underway.
-
For whatever reason, those Vishay Dale resistors don't come in 120K, 180K, or 220K, so you end up using 121K, 182K, and 221K. (But there is a 150K.) http://www.mouser.com/catalog/632/545.pdf
From this data sheet http://www.vishay.com/docs/31027/cmfmil.pdf , specifically the table on the lower part of page 3, it looks like the RN65C is rated at 1/4 watt at 125 degrees C, and at 1/2 watt at 70 degrees. :-?
I'll see what the Dumble gurus on ampgarage.com think.
-
Well it sounds like you answered your own question.Your amp can easily get to 70 deg.C. inside so that resistor is not good enough.
-
your builds look great! Where do you get your face plates? and also for the relays, I am using 5v relays. Do these call for 12v relays?
-
I make my own faceplates now.I have the use of a laser engraver.I use Omron 5v relays.About 35ma current draw.
-
Lead dress is important for quiet operation but I only have one shielded cable to the input.Mine is relatively quiet.
Do you recommend not shielding the Volume, Master Volume and Overdrive connections like the D'Lite layout then?
Mark.
-
Not every build will be quiet.I would shield the input to grid,the overdrive and overdrive level.The original dumble didn't shield the master.There is no need to shield the volume control.
-
Looking at how others reportedly have had success with adding a one tube reverb .......... I drew this up.
Any comments or observations?
Reportedly, only a small amount of reverb is used with these amps which makes sense to me.
I don't have any plans to build this amp but thought I'd post this for comments and discussion. The reverb idea could be good for other amps also like Marshalls etc....
Tubenit
-
Tubenit - two (ignorant?) questions: did you select the 5uf cathode bypass caps for the reverb driver & return to reduce a certain amount of bass in the reverb?
Also, have you tried using a single 12AT7 instead of a single 12AX7? I realize that the recovery stage would fall short on gain, but think that there would be more current driving the reverb tank.
My apologies if this is too far off topic.
Chip
-
I haven't built a D'Lite and have no plans to at this point. Simply reporting what others seems to have found successful including the 5uf and the 12Ax7.
Just trying to create some dialogue and thought among the successful builders here on using that design.
If you look at Hoffman's "add reverb to a Western circuit" layout, he uses .68uf with 820R for his one tube reverb. I did that with a Marshall clone I made and it worked great. My guess is oscillation is less of an issue within the reverb more highs and fewer mids/bass being verbed.
I have used a 6.8uf and found it helped tame the reverb a bit.
With respect, Tubenit
-
well, i finished the umblot lite. After corrrecting a few stupid mistakes, she's rockin. anyway, the clean sounds pretty good, but the distortion channel sounds a little(for lack of a better word) ragged. I do however have a pair of crappy 5881's in the power section and plan on picking up a pair of 6v6's tommorrow. hope fully this will help. thanks phsyco for all the help, i'll get it ironed out i'm sure.
-
Just remember the output impedance changes with 6v6's.Double the speaker impedance with 6v6's.
Here's a shot of the Reverb Rocket in progress.Still waiting for a 2 meg pot for the reverb.
-
Here's a shot of the completed amp.Just have to test it and finish the cabinet.
-
hey physco, installed the 6v6's, sounds alittle better. the disortion is still farty sounding a bit. the distortion is not really that smooth sounding. what cuases this? cold solder joint? any help would be great. by the way, I used one of those impedence selectors for hammond trannies. it was worth the 15 bucks, but i am not sure which wire to hook the neg feedback to. thanks for all the help, i really appreciate it. by the way, your new build looks kick ass! that is some clean work my friend.
-
Whats the PAB switch do?
-
The PAB is preamp boost.
Not sure why you don't have better sounding distortion.Did you install the trim pot for V2 bias?If so,turn it up higher.
Hook the neg feedback wire to the + of the speaker jack.
-
Hey Physc, You have confused me.. The subject is *umbolt Lite. Whats the Reverb Rocket??
-
It's my name for my version of the amp.Actually I toss that name around rather than the *umbolt one.
The faceplate says 'overdrive rocket' The reverb works great but I'm having other problems I need to sort out.
-
But these recent pictures are a different amp than the other pictures on page 1 of this thread, right? (I gotta learn to keep up.)
What kind of problems are you having?
-
Volume and overdrive issues.Not enough of either.I have obviously done something wrong but it's eluding me.The only difference between this one and the last is the addition of the reverb.That works great.
Loose,keep up!
-
i had the same problem, i don't know if it's the same problem, but on the input jack to ground i used a 500 ohm resistor ( green, black, brown) instead of a 1 meg (brown, black, green). just a shot.
-
Is the tone stack responsive at all with all that gain behind it? I've tried a trainwreck style tone stack with three extra gain stages behind it kind of like that of the this Dumble Lite. I cant get any real tone shaping from this type of tone stack attached to the input tubes anode. I always end up going back to the cathode follower when using a high gain preamp.
-
My previous build was very responsive.I had none of the problems i'm having with this one.It drove like a muther and the tone stack was very sensitive.This one is pissing me off. >:(I did nothing different and I'm using the same parts and transformers.
You have to use a 1 meg on the input.
i am however,using CTS volume and master pots.They may be my issue if the taper is funky.I used Alpha's on the other one.The OD is not giving me the gain either.????
-
yeah, I was in a hurry and put in the 500 ohm by accident.
-
Here's a dilly for you:I was not getting the drive out of this reverb amp like the other one I built and guess what?After I triple and quadruple checked everything I looked at the pots.
It calls for linear pots in the circuit in the bass,OD and OD level positions and guess what I had put in there?Yes,audio pots! DUH!!!!
Popped in some linears and problem solved.Reverb works great,OD is great,and the amp sounds killer.I prefer the 6V6's for drive but the 6L6's are nice and round.
I bought a big batch of 100k pots and never even though of whether they were log or linear.The bag says linear and the pot has this big 'A' o it.
-
Just a big THANKS to Tubenit for his reverb circuit.It works very well.
you want reverb and can't figure it out?Ask Tubenit.He has it worked out and is very generous with his work.
He is the MAN!!! :)
-
Wished I could take credit for this one! [smiley=smiley.gif]
However, I took PRR's advice about this reverb circuit (& amp design in general ) ......... "plagerize, plagerize, plagerize " ........ or something like that. [smiley=wink.gif]
Still I am glad it worked out good for you, I am enjoying that circuit on my amps too. It does seem to adapt well to amps with LTPI.
Best regards & with respect, Tubenit
-
Phsyconoodler,
Out of curiousity, I know it's difficult to get high gain amps quiet at idle. With the boost stuff engaged, ....... how does the "noise" level compared to say the Fender AB 763 type amps you've done?
Looking forward to sound clips of these amps.
With respect, Tubenit
-
This amp is as quiet as can be.There is some noise at the highest gain setting but it is far less than a JCM800.
I used cliff jacks isolated from the chassis and a ground buss that is grounded to a bolt next to the input jack.Really quiet.
An AB763 is different so it's not really a good comparison.This amp is so quiet at idle you have to hit a string to tell it's on.
-
Here's another shot before it disappears into it's cabinet.
-
looks nice, as usual. Hey, this might be a stupid question but on the overdrive tube there are (2) 270 pf caps that run between pins 1 and 3, and pins 6 and 8, what do these do exactly?
-
alright, i just checked my voltages on preamp tubes 1 and 2. I have a little over 300 volts running to each one. does this seem a little high?
-
I don't know what those capacitors do either.But I do know they need to be there.I ran out of 270pf caps and used 500pf's and it sounds fine.
Your preamp voltages need to be taken in context to the rest of the amp.What is the B+ and plate voltages at the tubes?What is the voltage at the 'Y' of the plate resistors?Are you measuring with all tubes installed and the bias set properly?
Do you have the wire hooked to the proper filter cap?Did you use the right size decoupling resistors?
We need to see what the rest of the amp is doing before we can determine if your voltages are ok.
-
I found out what those caps do.They prevent oscillations from the high gain preamp signal.I guess when you put the amp on a scope it can oscillatebadly even at frequencies you can't hear.The caps prevent it and also help define the OD tone too.A larger cap like 500pf is not as defined sounding in overdrive.The seventies D amps had 500pf and later models switched to 270pf or so to help the amp sound more focused.I used 500pf in this build just because I ran out of 270's and I rather like the overdrive.
I'm using Winged C 6L6's in this one.I guess you can play around and tweak it to taste.
-
The SCH files of the D'Lite have been updated and edited. A reverb version has been included given Physconoodler's success with it.
Additional layout designs were added using the terminal strips on the V1 & V2 tubes. As always, CHECK for errors and compare with original schematic and layout. Please PM me with any errors you may find.
http://www.el34world.com/Forum/yabb2/YaBB.pl?num=1193532616
Tubenit
-
heres a shot of the guts. not quite as clean as yours physco!
-
The important thing is you did it!
How is it working?The speaker choice is critical with this amp.A speaker that breaks up too early cannot get all the great tones out of this amp.I am using the Mojo Greyhound speakers and they are fabulous.
This amp is way easier than an AB763 build!
-
I really like the clean on this amp!! the distortion not so much, but i am gonna go back over the power supply, I still think the voltages are way too high for v 1 and 2. at the Y or the resistors feeding 1 and 6 the voltages are about 503 volts. I have a resistor under the board so I am gonna pull it out and see whats doing under there. Thanks for all the help, and I will keep you posted. Oh, I am using a closed back 2x12 cab with 80 watt celestions I think. I hate em. I bought it just to play some shows filling in for my friends band. I need to get my 4x12 cab out here to cali. it has greenbacks on one side and naylors on the other. sounds good.
-
Here's a shot of the amp in it's cabinet.I'm using a Mojo Greyhound speaker.The jury's out until it gets broken in.
-
very nice! how did you attach the chassis to the cab? I can't see any screws on top..
Chris
-
It's just jammed in there and I glued it in. ::)
Just joking! Look at the bolts on the side of the cab.It has a shelf inside the cabinet and the chassis slides in like a drawer and attaches from the sides.I use rivet nuts in the chassis and 1-1/2" bolts with 'v' heads in dress washers.
-
Hey Psyconoodler,
I fired up my *umbolt for the first time and tested the voltages before installing the tubes. Turns out I'm getting 12V at the relays for power. The Heyboer transformer I have has a 5 V winding with no center tap, which I used, but that must be 5v plus and minus from the center, so that's ~10V DC when rectified. D'oh! Questions: Will the 5v relays handle 12v until I have a chance to get some 12volt ones? Or, is there some way I can divide down the voltage easily? (there's not much room left in that chassis!). Any other suggestions?
Kind of dissapointing -- so close but I don't want to run the tubes in it until I know I'm not going to blow up the relays running them at 12v...
Thanks,
Mark
-
You could use a 7805 vr chip and a couple small components. It's about the size of a nickel.
-
With no load from the tubes the voltages will be higher.When you get tubes in the amp everything will settle down nicely.You definitely don't need a centre tap for the 5v winding.If you had one it would double the voltage and fry up one of the diodes on the relays.Remember,the relays use DC voltage which is rectified & doubled at the power supply board by the diodes and caps.The AC voltage you are measuring is not a concern.If the relay volts are too high after installing the tubes,you can use a voltage regulator as Sluckey suggests,but it unlikely you will need it.
By the way,check you E-Mail 8-)
-
Wonder where I could get one locally.... I'm thinking if I have to order anything, maybe I'd just order 2 12v relays and rewire the board. A pain in the neck because of where it's located, but maybe that's the best thing.
The heaters are at 6.3v.... could I tap into the heater supply secondary on the PT somehow? Man... I sure don't want this to be a big kludge.
-
12v,two relays sharing it, means 6v per relay right?The current is the important thing here.Correct me if I'm wrong.If they don't draw over 35ma a piece there should be no problem.I used 5v omron relays on both the last 2 builds and they are 100% fine.
Make sure your relay board is wired properly and the diodes are oriented right.You cannot use the 6.3v heater supply because it's got a ground reference and it will blow the diodes immediately and smoke your supply board.
-
Wonder where I could get one locally
RadioShack
-
I'll re-check my wiring.... And thanks for the warning on the heater. Ouch!
I did notice those 12v relays at Radio Shack. Thanks for the tip.
Mark.
We've got the grandkids coming over any minute, so I may not get to this until tomorrow :(
-
Sluckey's talking about the voltage regulator.The relays will not work if they are 12v.you should be just fine with the 5v relays.
-
12v,two relays sharing it, means 6v per relay right?The current is the important thing here.Correct me if I'm wrong.If they don't draw over 35ma a piece there should be no problem.I used 5v omron relays on both the last 2 builds and they are 100% fine.
I just used the ammeter across the swtiches to short the relays and I'm measuring 52ma on either one. So that's current drawn by the coil. I did check the wiring again and it looks like it's right, but I can check again. The relay power is wired in parallel (i.e. each relay coil is seeing the total relay power supply voltage of 12v). When you say they are "sharing" the 12v, did you mean if they were wired in series with respect to the 12v supply voltage?
Mark.
-
Sluckey's talking about the voltage regulator.The relays will not work if they are 12v.you should be just fine with the 5v relays.
All right. I'll just slap the tubes in there and start testing. Even if the 5v realys werent' happy, what's the worse that could happen? They'd just fail eventually, which won't hurt anything ;)
Mark.
-
All those D'lite owners that have the 5v relays can't be wrong.Two relays draw 52ma or 26ma a piece for a TOTAL of 52ma.
And two relays share the 12v supply.
If the wiring is right you will have no problems.