Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: rzenc on February 28, 2012, 07:03:25 am
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I finished this amp and had sometime to test it...
First EL84 based amp build.
After reading so much about high volt EL84 x lo volt EL84 I decided to try the lo volt path..
Results:
Amp sounds very articulated and touch response is awesome....From clean to mean...
Still need some tweaking to improve tone (adjust bass response) , but so far it's cutting thru the mix with wrath!!!
Had the chance to test it with WGS Invader (2x12") and Eminence Cannabis Hex (4x12")
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Can you tell us more about the amp... it seems interesting.
What plate voltages have you got?
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That is one beautiful amp build inside and out.
Are those speak-on connectors? And are you using one for the AC power cord?
Is the 3'rd piece of iron a choke? The 1 that's furthest from the PT? It looks like the center iron says OT? If so that's 1 big choke, so I take it that this amp's B+ is choke feed?
Brad :thumbsup:
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Can you tell us more about the amp... it seems interesting.
It's a simple amp, topology:
Input - gain stage - jamestonestack - gain stage - gain stage - Concertina P.I. - output power tubes and cathode biased.
What plate voltages have you got?
B+1= 298V (O.T.C.T.)
B+2= 290V (G2)
B+3= 267V (P.I.)
B+4= 251V
B+5= 241V
Are those speak-on connectors?
Yes. I quit P10 for a long time ago on speaker connectors..
And are you using one for the AC power cord?
No, It's Neutrik PowerCon - Kind of Speak-On for AC plugs...
Is the 3'rd piece of iron a choke?
Yep, 20H @ 97R @ 200mA's.
... so that's 1 big choke
Hellyeah!! I guess it's pumping out around 20W honest... amazing heavy for a small amp
...so I take it that this amp's B+ is choke feed?
Nope, it's cap input. Choke sits between O.T.C.T. and G2 node.
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Why did you go for such a big choke? Sound/feel/noise?
Brad :icon_biggrin:
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Why did you go for such a big choke? Sound/feel/noise?
I tried a resistor in place of a choke..lame bass response..did not sound right to my ears...
Decided to add a choke instead, had a 5H laying around...did not improve performance, indeed it turned out worse..hum issues and too much saggy - not on a good way
Had a 10H right to me..tought.. :think1: Let's try.. hum got better...amp started sounding faster, became more touch responsive, less saggy...could this be the path?? :dontknow:
Well, there's one way to find out for sure..let's order a 20H big badass choke....
The amp, as it's now, it pretty noiseless...I mean no hum, no hiss, no freaking noise/garbage riding behind the notes...Noisefloor is suberb....Even with gain maxed and guitar pots running wild....
Waiting a WGS Reaper55Hz to install on the red 1x12" pictured together with Klein Baphomet...
it wans't supposed to be a pair, however the owner of KB decided to take the red 1x12" together.. :icon_biggrin:
I will make some more tweaks and post the updated schem
Best Regards
R.
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Ditto to all that. Per my recent threads re my Traynor Bassmate EL84: dropped plate voltage from 410 to your numbers, using 1st a bucking tranny, then a power resistor after the SS rectifier. Great tone improvement. I agree that a choke further betters tone. (There's an awfully lot of iron in this little amp now!) Also need to further tweak tone for less treble. Arguably, that might call for more bass. But I think the bass is OK; it's just too bright. But will keep this in mind when fiddling with it.
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Also need to further tweak tone for less treble.
I'm exactly on this process right now...
Arguably, that might call for more bass. But I think the bass is OK; it's just too bright.
Mine needed more bass..solved it...
it's just too bright
Is it really a EL84 thing?
Althought I believe the tubes are singing beautiful, it seems to be really bright...but by any means far from the over-o-volt EL84 amps that I heard...
Best Regards
R.
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I don't think it's an el84 thing with bright tone. The Traynor Guitarmate does not have a brightness issue. Also I've tried el84's in my Hot Rod Deluxe, using Yellowjackets. No brightness issue there either.
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To bright? Did you bypass the gain stages plate
resistor with a 1000pf cap right before the phase inverter?
I take it that this is a Orange amp clone of sorts with a little
bit more gain. From the looks of you iron you could have
Built at least a 100 watt amp nice work BTW.
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I take it that this is a Orange amp clone of sorts with a little
bit more gain. From the looks of you iron you could have
Built at least a 100 watt amp nice work BTW.
Long story short: A customer bought an Orange Dual Terror…3 weeks later he calls me telling it’s not working and if I could check it out…
Warranty was still on so I advised him to go for it…1 week later customer returns telling they said he was on his on…
So the odyssey starts…
El cheapo impedance switch lost contact and burn O.T. – ordered a Mercury Axion ORDT (O.T. on the pics) and switch;
Stock tubes were noise – changed tubes;
Modded some bypass caps and coupling caps as well…Customer was finally happy…
2 months later a got a call from customer telling me the amp wasn’t working anymore…Got the amp and there was no fuse holder anymore…
he could not explain why it happened…so I installed another fuse holder and fuses blows.. narrowed to a burned winding on P.T….
Man… Customer was mad due to lack of support from manufacture r.. asked me to do whatever I wanted with it…
So…it started its life again as a Blues Express A5h.. changed tone stack from FMV topology to James . .changed from fixed to cathode bias…
changed V1 ECC83 to 12AY7…tried DC cathodyne.. it’s almost finished….I think..Swapped many tubes between V1 & V2
To bright? Did you bypass the gain stages plate
resistor with a 1000pf cap right before the phase inverter?
Yes I did…but I think it’s too much high bleeding @ one point only…it does not sound natural to my ears…
I tend to go with less on each stage…and get nice results IMO…last tweak was to add a 10pF @ V2 grid-plate gain stage…
Me and some guitar friends will test it tomorrow night... Hope to have nice reports back
Best regards
R.
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Dang, nice work. Like the painted end bells on the trannies too. As soon as I get better at making the insides pretty I gotta start on the outsides!
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Dang, nice work. Like the painted end bells on the trannies too. As soon as I get better at making the insides pretty I gotta start on the outsides!
Thanks John!!! :icon_biggrin:
Yesterday we tested the beast and got nice comments about it...could try 5 different guitars on it thru 3 different cabs and altought it showed each guitars characteristics amazinly, it really impressed us by it's strong personality! Could be named 70's Time Machine as well :l2:........Coupled to Gibson LP R9 + 2x12" WGS Invaders we could see mustaches growing fast!!
P.S.: pictured in the cage now...
Best Regards
R.