Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DummyLoad on July 12, 2014, 01:19:43 am
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have a breadboard of this amp. it has promise.
parallel class A single ended EL34s with a cascaded pair of 5879 driving. B+ is ~ 435V. have a fairly stiff filter that scrubs off the buzz well. it's very quiet on the breadboard.
probably delivering around 18-19W: i have not measured yet.
more along the line of a early princeton with a lot of attitude. simple one knob tone stack and a volume control.
has a smooth distortion and can be very bright if played with a stratocaster on the tail pickup.
both transformers are edcor custom winding that were for another project abandoned long ago. OT is 25W core with 3500Ω to 4Ω it has a UL tap but it is not used here. PT is 660VCT @ 120mA with 6.3VCT @ 4A. the edcor part numbers are on the schematic.
driving a pair of eminence legend 1028 in an old marshall open back cabinet. sounds pretty cool.
EDIT: revised schematic & wiring/mech.
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Ciao Pete
I see that for you it is a fertile period for new schemes
and very good documentation
:thumbsup:
Thanks for sharing
Franco
p.s.: SAMPLE - SAMPLE - SAMPLE !!!
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Hey DL, Neat amp and drawings. I don't know if you have seen this http://el34world.com/Forum/index.php?topic=17260.0 (http://el34world.com/Forum/index.php?topic=17260.0) I haven't proceeded with it yet so your build has good timing.
I was wanting to know if mismatch tubes were a problem in this kind of build, are yours matched??
Is there any +'s to having parallel TUBES that would be much better in a PP circuit
How do you like the edcor's as I was looking at the same for parallel 6L6s.
Like k said. SOUNDS SOUNDS
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Thanks for sharing!
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franco, grazie! i'll try to get some samples up soon.
timbo, you can use unmatched tubes within reason. 10% delta? 20% delta? i wouldn't go beyond 20%. you experiment. it will make more harmonic distortion. you could use a common cathode resistor. just start with a higher value resistor and monitor the dissipation of both tubes as you work down to a lower optimum value. it's a geetar amp, so as far as the higher distortion is concerned, it's maybe a good thing.
the tubes i'm using are well matched, they were matched quartet of svetlanas, however, one died so they are now part of this experiment.
EL34s in this test are dissipating just over 21 watts each. it sounds pretty good, but that fender tone stack is just not what i'd like. i may nix it and switch cathode caps for bass cut instead. to me, it seems like the range is too tinny to too dark and not much in between. even with triodes, this tone stack is "meh!"
edcor are fine products. i'm happy with them. 6-8 weeks to deliver is a bitter pill to swallow and why i don't use them much these days.
good luck with your concept.
--pete
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that fender tone stack is just not what i'd like
Err.... to which Fender TS do you refer ????
if you refer to the Tone Control on your schematic (I call TS those with a a minimum of 2 pot, Treble and a Bass, and Tone Control those with only one pot)
I think the problem is in the pentode, no TS following a pentode are seen if not preceded by a CF (5879 > CF > TS), as far as I can know that depends on the excessive load a TS represent for a pentode
Franco
EDIT: To follow a pentode I'll give a try to this Bass Cut Control
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Really nice drawings. I'm sure the amp will be equally as nice.
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Err.... to which Fender TS do you refer ????
franco, it's the 5E3 deluxe tone stack and i transposed it incorrectly. very much so... my apologies. i'll re-post the schematic when time permits.
changed the bypass caps to take the boom out of it. 4.7uF ist pentode, 2.2uF for second.
--pete
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some progress. worst part of building tube amps is wiring the filaments... anyone else share that sentiment? hope to have it done this weekend.
--pete
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worst part of building tube amps is wiring the filaments... any else share that sentiment?
I do. Thank goodness for transistors! :icon_biggrin:
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worst part of building tube amps is wiring the filaments... any else share that sentiment?
I do. Thank goodness for transistors! :icon_biggrin:
:laugh:
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WHERE............
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finished!
(http://i2.photobucket.com/albums/y11/pmitchel/zilker-20140829_191937-sm_zpsd0681fe3.jpg)
(http://i2.photobucket.com/albums/y11/pmitchel/zilker-20140829_191916-sm_zps54c45f5d.jpg)
(http://i2.photobucket.com/albums/y11/pmitchel/zilker-20140830_002911-sm_zps9943ffed.jpg)
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As always very nice layout and work Pete!
How do you like the way it sounds and the playing feel?
Brad :icon_biggrin:
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my2c, I use edcor on most all my SE builds n ya 6 weeks! On the other hand, you can't "buy" it sooner, to me that says integrity.
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thank you brad. it plays nice. lots of harmonic content and the breakup is very smooth. if you crank it with hot humbuckers then it can get nasty. the tone is unique, i can't really nail it down so hopefully i'll have some sound clips to post. i'm driving a pair of celestion greenbacks in that cabinet under it. i like them a lot.
shooter, i gave up on edcor for some time when they started quoting 8 weeks and more on some occasions. it's good stuff, just don't like the wait...
--pete
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And the tone stack?
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And the tone stack?
it shaves off highs only. quite nicely. may tweak the the x-over point to a lower freq., but i'm happy with it overall.
last rev. schematic attached and as built in the prototype.
--pete
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>> the tone stack?
> it shaves off highs only.
Looks to me like IF you ever run Volume well down, it should lift treble.
How "big" is this amp, in terms of room-filling? Bigger than a Champ? As big as a 2*6V6 Deluxe?
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>> the tone stack?
> it shaves off highs only.
Looks to me like IF you ever run Volume well down, it should lift treble.
How "big" is this amp, in terms of room-filling? Bigger than a Champ? As big as a 2*6V6 Deluxe?
estimated 18-20W - for a comparison i'd say that it much louder than champ and can get as loud as a deluxe reverb. i'll measure it shortly. i need to dust off the dummy loads anyhow; IF i can find them...
sending you an unrelated PM shortly .
--pete
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Pete,
You really build cool stuff! Nice job.
With respect, Tubenit
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thank you tubenit.
your cabinet work and amps are second to none.
--pete
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Diggin' it. :laugh:
Fargen makes a 2x El34 SE that I have played and it will get in deluxe territory in loudness. Claims 15 watts, but holds together with a nice tight feel.
Great build! :thumbsup:
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Good stuff DL!
It's funny how this place works sometimes......
I was watching your thread and not really getting why anyone would want parallel SE, but didn't want to ask any questons and sound stupid....and not really giving it much thought. (just chalking it up to some 'old pros' "showing off" :wink:)
But then a newbie comes along and asks a question about a par. SE design and it prompts me to use my breadboard for what it was meant for...so then I go back searching for some support, and it leads me right back to this current thread. (that I had been reading, but not reading into) :icon_biggrin:
So anyway,,,I tried it, liked it, and wanted to confirm something I read here:
Fargen makes a 2x El34 SE that I have played and it will get in deluxe territory in loudness. Claims 15 watts, but holds together with a nice tight feel.
Absolutely.....even with a low 300V plate voltage it struck me as being 'just as loud' as my friend's DRRI
So now that I'm all caught up with the rest of the class I'm gonna see where I can push it...
I can report that the use of mixed tubes gave me a favorable result of a "richer", fuller tone by mixing a 5881 with an EL34
Thanks again for sharing!
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The advantage, or reason for building a parallel SE amp.?
I assume it has "unique" tonal qualities and perhaps responds a bit different than a single tube would.?
The post above mine joked about not wanting to ask a dumb question, but I have never been smart enough to avoid dumb questions...so here goes...the power of tubes in parallel...how is that calculated.? Is it a simple additive equation...or is parallel more about current.?
Sorry for the dumb question, but a feel more dumb (or is it dumber.?) not knowing the answer.
Thank You
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> the power of tubes in parallel...
Design a 1-tube amp. Figure the power. Say 5 Watts.
Build two of them. Separate each is 5 Watts, so there's 10 Watts available, at least to two speakers.
Put both OTs in parallel, both speakers in parallel. If the OTs were say 5K:8 each, and the speakers were 8 Ohms each, you now have 2.5K:4 OT and 4 Ohm load. And all 10 Watts will appear in the load.
Realistically you parallel the 1-tube loads for 2 tubes, then find an OT of that primary value. The secondary can be whatever you like (and can find).
But to repeat: building a 2-tube SE amp is "stupid". For the cost of one phase-spitter, you can build a push-pull amp of equal or greater power with a very significantly lighter and cheaper OT, and lower THD.
So it is hard to find monster SE OTs. (OTOH, Hammond makes a 75W job.) (OTOOH, the cost and weight of that part will absorb all of your gig-pay and most of your back-strength.)
I agree it is a fun thing to try. I had a 13W 6550 rig going, but life changed. I think DL and friend had a bigger rig once, but life changed. Which may be telling us something....
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But to repeat: building a 2-tube SE amp is "stupid".
respectfully disagree. from my perspective, i prefer the sound of SE MUCH more in lower wattage amps, and i like amps in the 15-20W range for around the house and practice. that statement has more meaning in relation to engineering efficiency rather than tonal preference, e.g. you're counting Watts/lb, without consideration of what the listener likes.
i guess i am "stupid".
later,
--pete
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> the power of tubes in parallel...
Design a 1-tube amp. Figure the power. Say 5 Watts.
Build two of them. Separate each is 5 Watts, so there's 10 Watts available, at least to two speakers.
Put both OTs in parallel, both speakers in parallel. If the OTs were say 5K:8 each, and the speakers were 8 Ohms each, you now have 2.5K:4 OT and 4 Ohm load. And all 10 Watts will appear in the load.
Realistically you parallel the 1-tube loads for 2 tubes, then find an OT of that primary value. The secondary can be whatever you like (and can find).
But to repeat: building a 2-tube SE amp is "stupid". For the cost of one phase-spitter, you can build a push-pull amp of equal or greater power with a very significantly lighter and cheaper OT, and lower THD.
So it is hard to find monster SE OTs. (OTOH, Hammond makes a 75W job.) (OTOOH, the cost and weight of that part will absorb all of your gig-pay and most of your back-strength.)
I agree it is a fun thing to try. I had a 13W 6550 rig going, but life changed. I think DL and friend had a bigger rig once, but life changed. Which may be telling us something....
Geez...OK...Got it.
Interesting.
And having the word "stupid" in quotes was not lost on me.....I understood your meaning/intent. :smiley:
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i prefer the sound of SE MUCH more in lower wattage amps,
Different strokes... but you seem to be in the minority, there are just not that many popular SE low-wattage amps, may be 10% of the market? So cost per watt aside, based on market share, more players still seem to prefer the PP amps, even at low-wattage.
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I don't know what it is about the SE sound, but I love it too. Both of mine are just 1-tube/5-watters (roughly) but eventually I'll get around to building a SE with more umph. Might even steal Dummy's schematic. :icon_biggrin: Now if I'd just stop being stupid and messing with old VTVMs. I mean, who needs 'em?? :laugh:
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I agree it is a fun thing to try. I had a 13W 6550 rig going, but life changed. I think DL and friend had a bigger rig once, but life changed. Which may be telling us something....
i prefer the sound of SE MUCH more in lower wattage amps,
Different strokes... but you seem to be in the minority, there are just not that many popular SE low-wattage amps, may be 10% of the market? So cost per watt aside, based on market share, more players still seem to prefer the PP amps, even at low-wattage.
I don't know what it is about the SE sound, but I love it too.
There is something to it...
Remember, I'm still pretty easily excitable,,and anything that generates some decent distortion gets me going...
Initially, I tried a beefed up Plexi preamp into one EL34 and did notice a lack of clarity at highest gain settings (compared to PP)
But by adding the paralleled 5881 to the equation, it 'seemed' to fill out and be able to handle the squared off signal better.....still not 'as clear' as PP but more acceptable than just pushing a single tube.
Some of the magic is found by being able to push the big bottles into overdrive at a lower/non-ear splitting volume.
i guess i am "stupid".
:l2:
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meh! DEAD FOR > 120DAYS!
K - i updated the drawings. please use the schematic if there are any discrepancies.
--pete
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Many Many Thanks Pete
Franco