Rigonda used self-split output stage,. Transformer can't be used in SE, without additional air gap added. Equalizing network in loudness regulator is used to boost lows on low volume. The theory behind it is compliance to Fletcher-Munsen curves, but actually it was the way to extend bass reproduction below roll-off of speakers utilizing power capabilities of the amp when less of power is needed. 4GD-28 speakers were 8" speakers with 60-70 Hz Fs.
You can add a gain control by decoupling R11 with a capacitor in series with a pot, say 100k. This will increase the gain as the value of the pot is decreased. 
i recognised the way the el84s were set up, ive used that a couple of times for triode output stages, but what threw me is a centre tap is usually shown in the middle of the transformer...
Error. Should be a much smaller pot, say 5k max.You can add a gain control by decoupling R11 with a capacitor in series with a pot, say 100k. This will increase the gain as the value of the pot is decreased.
well, single ended is not that bad as well...
125DSE - this is the proposed traf, I find it kind of... expensive. Maybe the most expensive, much more than all the other stuff 🙂
http://www.hammondmfg.com/125SE.htm
Any ideas about the coil laps and gauge?
I thing I could find it out with a bit more investigation, but any hints appreciated
125DSE - this is the proposed traf, I find it kind of... expensive. Maybe the most expensive, much more than all the other stuff 🙂
http://www.hammondmfg.com/125SE.htm
Any ideas about the coil laps and gauge?
I thing I could find it out with a bit more investigation, but any hints appreciated
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or just suggest a reading on power tube amps (and transformer calcs respectively)
I will try to find a local enterprise to build me custom made if I dont find some suitable one
I will try to find a local enterprise to build me custom made if I dont find some suitable one
Not completely sure 🙂 🙂 🙂
but this design is anoying. Maybe it would give me clean bright crunch with a bit of an overdrive with all these feedbacks.
Actually it can pull out 7-10 watts, I ve been looking at the rigonda SE description..
So, I've found the transformers specs. Coils and wire gauge.
Could I find these for the hammond trannies recommendables? (coils and gauge)
Like for example the stuff this pal posted:
Untitled Document
- Building an Output Transformer for a Tube Amp
But it is about 6V6 push-pull, not EL84
London Power's Hammond Transformers: Matching Them Up
So, trying to calculate the coil turns and gauge by Ohms and the transf unit power?
Maybe have to post this in the other section as well.
but this design is anoying. Maybe it would give me clean bright crunch with a bit of an overdrive with all these feedbacks.
Actually it can pull out 7-10 watts, I ve been looking at the rigonda SE description..
So, I've found the transformers specs. Coils and wire gauge.
Could I find these for the hammond trannies recommendables? (coils and gauge)
Like for example the stuff this pal posted:
Untitled Document
- Building an Output Transformer for a Tube Amp
But it is about 6V6 push-pull, not EL84
London Power's Hammond Transformers: Matching Them Up
So, trying to calculate the coil turns and gauge by Ohms and the transf unit power?
Maybe have to post this in the other section as well.
looks like that OPT is a standard EL84 UL PP, i wouldnt get another one, just use that with the same LTP idea, then just rebuild the preamp, it might be an idea to change the 6n2p's for ecc83's / 12ax7's i dont think the bias would change dramatically but it would give you a fair bit more gain
Rigonda transformers:
View image: coils
Looks ok accordingly to the power: (7-10W)
Z1-0,14; Z2-0,64 mm
The guy with 15W fender amp suggests:
Z1-0,16/0,18; Z2-0,7/1.0 mm
View image: coils
Looks ok accordingly to the power: (7-10W)
Z1-0,14; Z2-0,64 mm
The guy with 15W fender amp suggests:
Z1-0,16/0,18; Z2-0,7/1.0 mm
I started playing and changing with dwg app (no calcs yet)
- Loudness pot and chains - cut
- Negative feedback - cut
- Tone chains - cut
- "Gain" in between the preamp tube stages
- 3band EQ before the push-pull
- Push-pull kept "non-symetric" (don't know about this implementation)
- Kept negative feedback to the output valves
Changed:
- View image: r102 gain 3b EQ
Original:
- http://postimage.org/image/10pbycuh0/
Since I plan to use USSR tubes only, Maybe it is a good idea to insert another 6n2p valve and second gain (like ax84high-octane, tiny terror)
What do u think?
- Loudness pot and chains - cut
- Negative feedback - cut
- Tone chains - cut
- "Gain" in between the preamp tube stages
- 3band EQ before the push-pull
- Push-pull kept "non-symetric" (don't know about this implementation)
- Kept negative feedback to the output valves
Changed:
- View image: r102 gain 3b EQ
Original:
- http://postimage.org/image/10pbycuh0/
Since I plan to use USSR tubes only, Maybe it is a good idea to insert another 6n2p valve and second gain (like ax84high-octane, tiny terror)
What do u think?
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looks good so far, but how does it sound? if you like it keep it, if you add another tube, youl probably need a gain and master volume control, though maybe itd be a good idea to look at the JCM 800 i think most single channel amps follow it. or at least from what ive seen,
Not started yet.
Working on the combo cabinet 🙂 got some cheap 12'' chinese wide-range speaker, 30watts.
Actually, first I would like to start easy. Not removing the original chains.
How to add midtone chain to the existing bass, treble? How to calc it?
Then try adding some gain knob at the stage 2 cathode.
What if I add a master volume just before the push-pull?
Will it stay more sensitive and bright at low volume than if it is at the very input?
Here all sugesstions:
- View image: r102 3band EQ gain old ask
If it gets more sensitive with some clean bright crunch, I will use it for a while, as it it, plus some boss stomp box overdrive.
Working on the combo cabinet 🙂 got some cheap 12'' chinese wide-range speaker, 30watts.
How to calculate the resistor and decoupling cap?You can add a gain control by decoupling R11 with a capacitor in series with a pot, say 100k.//changed to 5kmax. This will increase the gain as the value of the pot is decreased.
Actually, first I would like to start easy. Not removing the original chains.
How to add midtone chain to the existing bass, treble? How to calc it?
Then try adding some gain knob at the stage 2 cathode.
What if I add a master volume just before the push-pull?
Will it stay more sensitive and bright at low volume than if it is at the very input?
Here all sugesstions:
- View image: r102 3band EQ gain old ask
If it gets more sensitive with some clean bright crunch, I will use it for a while, as it it, plus some boss stomp box overdrive.
ok sorry for being late, im on holiday in america for 5 weeks 🙂 as for resistor and coupling cap, corner frequency can be found using 1/(2(pi)xRxF)=C if youve kept the circuit as it is on the original diagram, then i would add a mid control to the cathode of the second triode stage using a capacitor (220n maybe) and an inductor (baybe 500mH) (im not completely sure of values, i cant remember the inductor frequency equation) with a vasriable resistor between them and ground. this will give you a mid boost, an ideal frequency for mid is about 1.5-2k and these are the best frequencies for distortion, (ignore the scooped mids stuff, i cant believe how many amps had the typical bass 10 mid 0 treble 10 setting in the local guitar centre today...) i wouldnt bother with what you have circled in red unless you want a bias control with the buiggest effect on low frequencies and with a 5k pot, im not sure how effective it will be.
seems that the gain control does nothing..
btw, the original circuit was working pretty well, listening music through it, but now it gives very low output.
I am starting over, with a vox ac 15 heritage schematics.
The penthode chanel only. It sounds just great!!
Not sure about the power supply.
I measured it, according to the schematics it should be 270 volts on the OT mid tap, but it reads around 340... With the valves on..
btw, the original circuit was working pretty well, listening music through it, but now it gives very low output.
I am starting over, with a vox ac 15 heritage schematics.
The penthode chanel only. It sounds just great!!
Not sure about the power supply.
I measured it, according to the schematics it should be 270 volts on the OT mid tap, but it reads around 340... With the valves on..
really? are you sure the gain pot is grounded and wired properly? no shorts and the pot works? as for the power supply 340 sounds like it should be fine, what is the current draw and what value filter caps are in there?
Havent measured the current draw yet. (kind of аfraid to do that..)
there are 2 x 50 uf caps and one of 10 uf - power supply
probably wouldnt need more than a 47uF reservoir cap, or are the 50uFs in series? the amp is cathode biased right? just measure the voltage at the cathode, and use ohms law to find power tube current, then just measure the voltage drop accross the 1st resistor to the rest of the PSU and use ohms law to find current there, for a PP 15 watt amp 30mA on the EL84 and 1mA per preamp tube sounds about right.
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