Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: phsyconoodler on August 20, 2012, 02:22:08 pm
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I got an HRDIII in for modding and I played it to get a base idea of the tone before the mods.The schematic is pretty much the same as previous HRD's but it is supposed to have a 'tighter' overdrive and the volume and treble control taper's are different.
Well I plug in my Tele with Custom shop no-caster pickups and the clean channel sucks right off the bat.I mean this amp has no good clean tones in it.Lifeless and thin.
Then I hit the drive button and am greated with a this,raspy drive that gets worse as you turn the drive up more.Nasty,nasty nasty!
So,I've got my work cut out for me.I'm doing the same mods as I normally do as the basic schematic hasn't changed much.The reverb still is metallicy sounding and the mids are too much,not enough bass and generally lifeless harmonics.The drive channel is going to be harder to get sounding better,but I'm going to have at her.
I will keep you posted if the results are worth mentioning.
Deluxe III ? I would NEVER encourage anyone to buy one.Awful at best.IMHO
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Deluxe III ? I would NEVER encourage anyone to buy one.Awful at best.IMHO
3'rd try by Fender and it's worse not better? :w2:
I wonder if the easy access to the medical marijuana stores have a hand in this? I've read that Cali. has more of them than Starbucks coffee shops.
Brad :laugh:
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As near as I can figure,the changes are across the master volume there is a 390pf cap on the old HRD's and the new ones have a 1000pf cap. C11
I don't see anything else at this point.The drive channel sucks with single coils.It may be fine with humbuckers but I don't play humbuckers much and a lot of other people don't either,so what was Fender thinking here?
I might clip that cap entirely and see what it sounds like.I'm still comparing the schematics and most everything looks pretty close except the pot changes on the volume and master.That is a welcome change!
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I think you have your hands full with the HDR III version. I had one about 2 months ago in a post on here i was working on. I just changes out the bad small blue PS caps but did no mods. It also had a bad relay. It sounded ok but nothing like the early HRD. Thin like you said. Why dont amp makers stick with what is already known to be a good design /amp?
Now that i think back i did remove the 390pf master cap on the original HDR. It sounded ok. Later i changed it to 100pf cap
Is that master pot linear on the III version?
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No it's an audio pot on the master and the volume controls now.
I'm going to clip the master cap before I mod this amp to see if it helps the very anemic overdrive channel.
I also note from the schematics that there is a 220k resistor going to ground across the bass pot at R105.
Wonder why it's there?Overall the foray into these HRD's is puzzling at best.
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Clipping that insane high value 1000pf cap will surely smooth out and take the harsh edge off the tone the master (OD) now has.
But you will still need to play with different values for cap C23 to smooth out the OD a little more.
I tried values of .0047 & .0022. / .0022 was still a tad on the thin side so i settled on .0047
Also i tried a .022 on C2 but again it got to thin so i put the .047 back in. This amp does not seem to respond the way most other amps do with cap values we would normally use in fender and marshall amps (among others)
Increasing the first filter cap stage as you said in another thread really made a big difference in getting control of the flabby bass. Believe it or not i could not find another speaker that sounded better than the stock speaker mainly to get a tighter bass and still have that nice stand out note articulation. The stock speaker is pretty decent. That was the 1996 model though. What speaker is in the new version?
I cant imagine the clean channel sounding that bad. Maybe those PS caps are like the small crappy blue ones i found in the 1996 i had /
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ok,here's some more changes:
-R52 from 180k to 240k
-R9 from 220k to 270k
-R44 from 180k to 56k
-C23 from 1.5nf to 560pf
All these and the 100pf cap across the master are what's making this drive so much different than the old HRD's.
I'm going to do the changes in one step changes so I can see what happens on each change.Yeah,it's a lot of work but the end result...Tone....is what it's all about.
As they are now they suck bad! Really bad!
I am positive that the designer/engineer never even listened to this amp and built it solely by mathematics and using a frequency chart program.I can't believe that Fender would make the same mistakes over and over again unless it's all about planned obsolescence and the bottom line.
Does anyone at Fender play guitar? :guitar1
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Brand new design and someone asks you to mod it... Tell the guy to buy a different amp next time.
Just the same, nice job working the mods!
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Well,a setback has occurred. I got the mods done and the clean channel sounds great with excellent reverb,but.......the distortion channel is trebly beyond words.I have to turn down the tone on the guitar almost all the way and then it sounds good.
What the F...? Wonder what's going on here? This amp is becoming a nightmare.I've gone over the schematic and can't nail down anything that would make the distortion sound more trebly than the clean channel cause they share the EQ.
Any insights into this would be welcomed.It's making my head hurt right now!! :BangHead:
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ok,here's some more changes:
-R52 from 180k to 240k
-R9 from 220k to 270k
-R44 from 180k to 56k
-C23 from 1.5nf to 560pf
I've gone over the schematic and can't nail down anything that would make the distortion sound more trebly than the clean channel cause they share the EQ.
You changed the coupling cap, C23 from V1a on the OD side to a smaller value and it's before the tone stack. I guess you did that to get some of the mud out of the OD channel?
Plexi50 said he changed C23 up to .0047 (4.7nF). It's unclear to me what he changed C1 too. Schemo shows 47uF and he shows both 22uF and 0.22uF?
Brad :dontknow:
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Those changes I listed are on the schematics form the old HRD to the new one.THOSE changes.
I didn't change anything in the diastortion channel to make it so bright.There is something amiss but it's eluding me right now. :dontknow:
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I didn't change anything in the diastortion channel to make it so bright.
Then it looks like Fender did. Wouldn't 560pF kinda small for a coupling cap?
Brad
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Not that small.I did try a larger one but it didn't do anything.
I wonder if the relay is wonky and it's bypassing the tone stack somehow.That's really the only reason I can think of why it's so trebly.Wierd to say the least.
He di complain about a popping noise when using the footswitch.............hmm....
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Wouldn't 560pF kinda small for a coupling cap?
That's only half the equation. How big is the resistance? It's all about RC time constant.
Imagine you have a cap with a value of 10. And you have a resistor with a value of 100. (These are make believe numbers to easily make the point. The RC time constant is 1000. Now decrease the cap value by a factor of 10 (cap = 1. If you increase the value of the resistor by a factor of 10 (R = 1000) also, you still have the same time constant.
Look at the input cap value for the PI on this Fender Bassman amp. Pretty small! But the input impedance of that LTP is verrrrry high. Still passes bass notes easily.
http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_AA864.pdf (http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_AA864.pdf)
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Wouldn't 560pF kinda small for a coupling cap?
That's only half the equation. How big is the resistance? It's all about RC time constant.
Ahhh. Schemo is in reply #5.
I wonder if the relay is wonky and it's bypassing the tone stack somehow.That's really the only reason I can think of why it's so trebly.
He did complain about a popping noise when using the footswitch.............hmm....
Trace the signal with a signal tracing amp like Doug has in his lybrary.
Brad :think1:
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Ok,I'm following the signal path in the Deluxe III and it goes into V1 and then it either goes through the volume control and then into the tonestack or if the Drive relay is activated it goes past the volume to the drive control.Then it goes to V2 and then to the rest of the circuit,V2 being the more drive(one triode) then to an opamp (TLO72) then to the Reverb opamp and then to the PI.
Somewhere along the line treble is abundant beyond belief,but it makes no sense to me cause it all goes through the tonestack first in clean or drive modes.So where is this extra treble coming from?
Here's the scenario: clean channel and reverb are great now,but switch that drive on and it gets so thin that your teeth rattle.The treble works cause if you turn it off the tone is great but switch back to clean and it's mud-city.
What am I missing here?What's being bypassed here? Strange days indeed. :help:
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If I'm understanding Sluckey, I'd change R44 from 100K to 1M and see what happens to the OD? It will mess with the clean but at least you will know if it increases the OD's bass?
Brad :think1:
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They ommitted CR16 Diode that is in the newer models for a 100K or 100 ohm i dont remember which one for sure. All else to my memory is the same. I wonder if this is the problem with the OD channels sound/
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I hate this amp!!! :BangHead:
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Any luck yet on finding the solution? :worthy1:
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Not yet,it's going back on the bench today.
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Man that sounds like one of those amps that will make you draw blood before it gives in. I hate those times
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Fixed it! It turns out there was a lifted pad that was making the amp sound shitty right out of the box even before the mods.I poked and prodded til I found it and it sounds great now.
However,the speaker is not as good as the old Eminence's were IMHO.That's after the mods are done.A celestion V30 sounds better in those amps but the best IMHO is a P12N Jensen.
The amp sounds fine now and the clean channel and reverb are excellent.The drive channel likes more mids,so turn up the mid control and it sounds great with my tele.
Still overall not even close to my little bastard jam amp but respectable for a hot rod deluxe.
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When i drop those boards down from the chassis i wind up just re soldering the EQ,Jacks, and any other funny looking thin solder areas. I think a cracked trace would be the worst case making you check every trace for continuity. Glad you found the problem. :worthy1:
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At the expense of sounding dumb, what is a pad? I've been loosely following this thread because I use to have the original USA made 1996 HRD. The clean channel worked great as far a nice tube compression and good tone except the reverb. If you turned the reverb past 2 it sounded bad--so no surffer reverb on that one. I understood there was a mod to fix that(along with a lot of other things) but my main effect was delay, so I naturally ran the reverb low anyway not to get to muddy with the delay. The boost channel was a mess and I could never stand it so I use my pedalboard for distortions. Anyway glad you go it going!
Platefire
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Pads are the little circular copper trace at the end of the long pc traces.It has the hole where the component gets inserted into.They are cheaply built and can only handle so much heat or mechanical movement befor they lift up or separate from the rest of the copper trace.
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I got an HRDIII in for modding and I played it to get a base idea of the tone before the mods.The schematic is pretty much the same as previous HRD's but it is supposed to have a 'tighter' overdrive and the volume and treble control taper's are different.
Well I plug in my Tele with Custom shop no-caster pickups and the clean channel sucks right off the bat.I mean this amp has no good clean tones in it.Lifeless and thin.
Then I hit the drive button and am greated with a this,raspy drive that gets worse as you turn the drive up more.Nasty,nasty nasty!
So,I've got my work cut out for me.I'm doing the same mods as I normally do as the basic schematic hasn't changed much.The reverb still is metallicy sounding and the mids are too much,not enough bass and generally lifeless harmonics.The drive channel is going to be harder to get sounding better,but I'm going to have at her.
I will keep you posted if the results are worth mentioning.
Deluxe III ? I would NEVER encourage anyone to buy one.Awful at best.IMHO
I blv you build dumbles right psychonoodler? SHouldn`t be that hard to inc some of those ideas into this amp, i`ve done this for 13 years, and it sounds absolutely phenominal! Lotsa tweakin, but i`ve arrived! Try lowering preamp voltages first( and regulate) , lower the bypass caps on V1A/B to 4.7, make the last cath cap a 1uf, regulate the screens, if you really want a nice tone now dumbleize the driver.. ;) You @ got it all xcept mysecret secret tweak, but it`
My Best jim@Omegaamps.com
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I probably already know your 'secret tweak'. The next time I have one in for modding I'll try dumblizing it and see what it sounds like.
Don't get me wrong,I've modded a lot of the older HRD's but this newer one is quite a bit different,and it doesn't respond the same way,so it takes a bit of tweaking to get it right.