@indianajo: I have the late model with all transistorized preamps. These have been replaced with opamps. The cutoff frequencies on the low pass are well below the lowest note. Nothing wrong there.
The two bass coupling caps in the amplifier appear to be tantalum and have not been replaced. C369 and C370 in the schematic. If these are much lower in capacity than marked, this would explain poor bass response at the lower end of the spectrum. The lowest frequency on this organ is 32.69 Hz. and it's really weak.
I lost my meter so I'm just going to replace them tomorrow and see what happens. I rolled the bass power tubes with the originals which were working and made no difference. All electros are new. Hammond does not indicate what drawbars are pulled to get maximum power out of the bass section. I do need those lower notes a little louder, however. I can't believe they are so low, by design, at maximum pedal.
Note, your post is the second I did not receive an email notification. I need to check into that.
Thanks.
The two bass coupling caps in the amplifier appear to be tantalum and have not been replaced. C369 and C370 in the schematic. If these are much lower in capacity than marked, this would explain poor bass response at the lower end of the spectrum. The lowest frequency on this organ is 32.69 Hz. and it's really weak.
I lost my meter so I'm just going to replace them tomorrow and see what happens. I rolled the bass power tubes with the originals which were working and made no difference. All electros are new. Hammond does not indicate what drawbars are pulled to get maximum power out of the bass section. I do need those lower notes a little louder, however. I can't believe they are so low, by design, at maximum pedal.
Note, your post is the second I did not receive an email notification. I need to check into that.
Thanks.
It supposedly might be a tough, not to say impossible job to get some B-3 like sounds from a H-100. The H-100 generator produces 96 true sinusoidal tones, even in the lowest octave where the B-3 features complex tonewheels with rich overtones that makes the bass pedal somewhat sound like a fart in a bath tub and much louder than pure sinusoid tones. The great and swell manuals don't have harmonic foldback in the lowest octave, the 16' drawbars actually run down to 32.69 Hz, not to 65.38 Hz as in B-3's. Maybe that's your issue?
Best regards!
Best regards!
It was the coupler caps.
Now the lowest note is loud enough to be useful. The bias divider circuit also serves as the ground reference for these caps and since they were below spec, the roll-off began too early, I presume.
Incidentally, since I had cranked the signal up so much, with all drawbars out and full expression pedal, I now perceive the speaker is just beginning to bottom out. I know what this sounds like from over-driving a 45W Fender Super Reverb. The speakers complained.
I'm not getting the volume with the manuals (for the lowest note), so that must be the roll-off adjustment there. However, the manuals have tapered volume by the octave. This is done with the resistor wires. It might be by design to prevent muddiness. I have to check what I did with the manual opamps. I would like the option of playing a bass line on the manuals.
When comparing this organ to the B3, the Hammond owner's manual says of the extra tone wheels:
"The X-77 [also H-100] Hammond organ incorporates four additional harmonics which are controlled by two additional drawbars [upper manual only]. These harmonics permit the player to substantially enhance the authenticity of string and reed family tones."
Thanks everyone for all the counsel. I learned a lot from this. In retrospect, I should have replaced those caps while there doing all the other ones.
Now the lowest note is loud enough to be useful. The bias divider circuit also serves as the ground reference for these caps and since they were below spec, the roll-off began too early, I presume.
Incidentally, since I had cranked the signal up so much, with all drawbars out and full expression pedal, I now perceive the speaker is just beginning to bottom out. I know what this sounds like from over-driving a 45W Fender Super Reverb. The speakers complained.
I'm not getting the volume with the manuals (for the lowest note), so that must be the roll-off adjustment there. However, the manuals have tapered volume by the octave. This is done with the resistor wires. It might be by design to prevent muddiness. I have to check what I did with the manual opamps. I would like the option of playing a bass line on the manuals.
When comparing this organ to the B3, the Hammond owner's manual says of the extra tone wheels:
"The X-77 [also H-100] Hammond organ incorporates four additional harmonics which are controlled by two additional drawbars [upper manual only]. These harmonics permit the player to substantially enhance the authenticity of string and reed family tones."
Thanks everyone for all the counsel. I learned a lot from this. In retrospect, I should have replaced those caps while there doing all the other ones.
I think your quotation refers to the TWG's highest octave, which is a real one, generated by twelve 256 teeth tonewheels rotating at proper rpm speeds, in comparison to most other Hammonds with only seven 192 teeth tonewheels rotating at the rpm of other wheels that produce a fifth above, e.g. F -> C5, F sharp -> C5 sharp etc.
Best regards!
Best regards!
Yes, and those drawbars need to be used conservatively. The owner's manual gives some guidance.
Some of the tonewheels are "complex". The H even adds more. I tried to view the waveform on the Visual Analyser PC oscilloscope, and all I got was a modulated signal. I did not spend much effort in getting a readable waveform. I was just trying to chart all the frequencies. There must be a huge amount of distortion on them.
At any rate, the technology is impressive for the 1930s. Suzuki bought the name but refused to continue with the tone-wheel generator. The old generator produced frequencies that were always out of tune, along with some bleed between tone-wheels, which gave the organ its characteristic sound.
Another stark difference compared with the B3 is 4 drawbars for the bass instead of 2. All of them out will give a growling tone somewhat like a fuzz on a bass guitar. Or a "fart" sound as was mentioned in one of the posts.
Some of the tonewheels are "complex". The H even adds more. I tried to view the waveform on the Visual Analyser PC oscilloscope, and all I got was a modulated signal. I did not spend much effort in getting a readable waveform. I was just trying to chart all the frequencies. There must be a huge amount of distortion on them.
At any rate, the technology is impressive for the 1930s. Suzuki bought the name but refused to continue with the tone-wheel generator. The old generator produced frequencies that were always out of tune, along with some bleed between tone-wheels, which gave the organ its characteristic sound.
Another stark difference compared with the B3 is 4 drawbars for the bass instead of 2. All of them out will give a growling tone somewhat like a fuzz on a bass guitar. Or a "fart" sound as was mentioned in one of the posts.
Watching the Ed Sullivan show, nobody used the bass pedals on a B-3 anyway. Or any of the performances at the white house. Or Steve Winwood.
Thing about the upper drawbars and extra harmonics, you don't have to use them. They shut off at setting 0. I like them for a screaming stop I use a lot, an imitation farfisa sound or maybe that mellotron in "Telstar", but those sounds were never attempted by a B-3. I have some fundamentals, a big hole in the middle, and some 10 and 11.
Having played other organs with wandering RLC oscillators, and being a double reed player who hated playing with amateur orchestras that the strings were always way off tune, I like the tuning of the Hammonds. It is not perfect, but it is pretty good.
You've still got something wrong with your bass notes if they fart. Mine are quite pure on the black drawbars, a nice imitation of a pipe bourdon without any chiff. I'm a friend of SIAGO that puts on a dozen pipe organ concerts a year, so I've heard real pipes recently. Look at the goes into wave form from the TG and the comes outa wave form from the 7591 amp. My 16' sounds pretty pure so I didn't bother.
The brown drawbars mix in some 8' drawbar for a fatter sound, see the wiring in the pedal area. A little octave mixed in makes a more clarinetty sound.
Oh, about your new op amp preamps. Hammond use high frequency roll off to eliminate the key click of a contact closing as a waveform was at maximum from the generator. you've got to emulate that.
Thing about the upper drawbars and extra harmonics, you don't have to use them. They shut off at setting 0. I like them for a screaming stop I use a lot, an imitation farfisa sound or maybe that mellotron in "Telstar", but those sounds were never attempted by a B-3. I have some fundamentals, a big hole in the middle, and some 10 and 11.
Having played other organs with wandering RLC oscillators, and being a double reed player who hated playing with amateur orchestras that the strings were always way off tune, I like the tuning of the Hammonds. It is not perfect, but it is pretty good.
You've still got something wrong with your bass notes if they fart. Mine are quite pure on the black drawbars, a nice imitation of a pipe bourdon without any chiff. I'm a friend of SIAGO that puts on a dozen pipe organ concerts a year, so I've heard real pipes recently. Look at the goes into wave form from the TG and the comes outa wave form from the 7591 amp. My 16' sounds pretty pure so I didn't bother.
The brown drawbars mix in some 8' drawbar for a fatter sound, see the wiring in the pedal area. A little octave mixed in makes a more clarinetty sound.
Oh, about your new op amp preamps. Hammond use high frequency roll off to eliminate the key click of a contact closing as a waveform was at maximum from the generator. you've got to emulate that.
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They are non-invering with gain of 11. 1k straight to ground (no cap), 10k feedback with 120-150p parallel clamp. This is what Rod Elliot called for in his P27 SS guitar amp. It filtered out any RF that may sneak in from the guitar, and also to prevent oscillation. I see higher and lower values for this cap depending on who designs the audio circuit.
For the Hammond, I would not want much roll-off under 15 kHz, since that is all most cone speakers can reproduce anyway. There is no key-click with the 120-150p setup, which means I could probably lower the capacity of the cap.
Anything that produced percussion has been ripped out. If I want closer to that kind of attack, I simply adjust the drawbars on either A or B presets.
Although I have seen bass pedal use only in the churches, it's a nice option to have if you don't have a bass player.
Speaking of the bass, the bias adjustment has a panel mounted-plug on the chassis with three terminals, so readings may be made without flipping the chassis over. I am not sure how to center adjust--at idle or when there is some output?
The only 3 pin connectors I'm aware of on the H100 power amp are the ones going to the speakers.
I think one adjusts the bias on the 7591's to get a symmetric waveform. So one would make a bass note come out with a weight on the keys or something and adjust with scope or by listening.
I like the string bass feature when playing bass to pop/rock songs. Nice envelope.
B3's have a threes and twos attack, or increased volume at start of the waveform. That is third and second harmonic. It is a rocker switch. Many classic B3 players like Earl Grant or Jimmy Smith used it.
If you're familiar with synthesis, a note volume has ADSR for attack, decay, sustain, release. A B3 and H100 have attack + decay at the beginning of the note. H100 has sustain (harp). The envelope of the H100 attack is not that far off the B3 envelope, but H100 provided mistures of harmonics instead of the pure twos and threes of the B3. I find the guitar and banjo attacks rather annoying. Guitar can have a harmonic deleted to make twos, banjo can have several harmonics deleted to make threes. Rewiring in the tab box. I didn't do it, I'm going to install more drawbars to make the attack waveform harmonics controllable with drawbars, with op amp mixers instead of the mixing transformer.
I find the glock percussion particularly attractive as an electric piano sub. I put ceramic 10 uf timing caps in the envelope circuit instead of wound electrolytic, and it made the attack particularly aggressive. I put some high harmonics on the glock percussion tab and make a very convincing fender/rhodes stop, IMHO.
What I hate about real synthesizers, is that I bought one, one of the last made in USA, and the ***-**** disk drive froze up in four years. Not compatible with PCAT drives. The Hammond attack and sustain circuits should last 100 years if I use ceramic or film caps instead of the wimpy electrolytics they shipped it with. Also the H100 attack is programmable with a soldering iron, instead of having a software package that sits there with a blank screen like everything I've bought since Intel 8008 assembly language compiler.
I think one adjusts the bias on the 7591's to get a symmetric waveform. So one would make a bass note come out with a weight on the keys or something and adjust with scope or by listening.
I like the string bass feature when playing bass to pop/rock songs. Nice envelope.
B3's have a threes and twos attack, or increased volume at start of the waveform. That is third and second harmonic. It is a rocker switch. Many classic B3 players like Earl Grant or Jimmy Smith used it.
If you're familiar with synthesis, a note volume has ADSR for attack, decay, sustain, release. A B3 and H100 have attack + decay at the beginning of the note. H100 has sustain (harp). The envelope of the H100 attack is not that far off the B3 envelope, but H100 provided mistures of harmonics instead of the pure twos and threes of the B3. I find the guitar and banjo attacks rather annoying. Guitar can have a harmonic deleted to make twos, banjo can have several harmonics deleted to make threes. Rewiring in the tab box. I didn't do it, I'm going to install more drawbars to make the attack waveform harmonics controllable with drawbars, with op amp mixers instead of the mixing transformer.
I find the glock percussion particularly attractive as an electric piano sub. I put ceramic 10 uf timing caps in the envelope circuit instead of wound electrolytic, and it made the attack particularly aggressive. I put some high harmonics on the glock percussion tab and make a very convincing fender/rhodes stop, IMHO.
What I hate about real synthesizers, is that I bought one, one of the last made in USA, and the ***-**** disk drive froze up in four years. Not compatible with PCAT drives. The Hammond attack and sustain circuits should last 100 years if I use ceramic or film caps instead of the wimpy electrolytics they shipped it with. Also the H100 attack is programmable with a soldering iron, instead of having a software package that sits there with a blank screen like everything I've bought since Intel 8008 assembly language compiler.
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The center pin is ground, the other two go to pin 5 of each 7591. It is located on the right side looking from the back of the unit, near the spring reverb unit.
I would not adjust it by listening, while it may sound good, if there is offset, it would magnetize the iron in the OT over time. I did center waveform on scope since it seemed like the best way, since it would eliminate tolerances in the resistors and tube mismatch. I set the scope for DC remove because the only place DC can come from is the test equipment.
Thanks for the comments on tone adjustments and synths.
None of my units have that bias set connector. I have 3 early units with vacuum tube percussion and one extra amp I received from Bob H.
Pin 5 of the 7591 is the cathode, so in push pull circuits you generally try to equalize the cathode currents of the two sides. Based on my dynaco ST70 experience, they were shooting for 10 ma at idle for 6CA7, which is a slightly higher power tube than 7591. With one adjustment for both tubes, all you can do is equalize them, which stops DC current flow through the transformer. at idle anyway.
Pin 5 of the 7591 is the cathode, so in push pull circuits you generally try to equalize the cathode currents of the two sides. Based on my dynaco ST70 experience, they were shooting for 10 ma at idle for 6CA7, which is a slightly higher power tube than 7591. With one adjustment for both tubes, all you can do is equalize them, which stops DC current flow through the transformer. at idle anyway.
I asked about this adjustment before, but I forgot about it. The schematic says it's a bias adjustment but DF96 says it's for balance to eliminate DC, which is where the 5 pin is connected to the 10 ohm resistor, which continues on the outside connector--one for each tube. I don't know too much about output tubes but as I understand it, the -24V being present means they are self-biasing, as most use the term.
Mine is a very late unit. In fact, there is a stud-mounted device on the chassis that looks like a diode, but I suspect it is a high-current zener for regulation. The schematic I posted and the service manuals available do not accurately represent the amp in question. For instance, there are booster caps on the 7199 bass driver tube that are not shown in the schematic.
Hammond Organ 7591 Bias Adjustment
Mine is a very late unit. In fact, there is a stud-mounted device on the chassis that looks like a diode, but I suspect it is a high-current zener for regulation. The schematic I posted and the service manuals available do not accurately represent the amp in question. For instance, there are booster caps on the 7199 bass driver tube that are not shown in the schematic.
Hammond Organ 7591 Bias Adjustment
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