http://www.paia.com/prodimages/siabsch.pdf
This looked interesting until I saw the schematic and all those op-amps. Probably an interesting hybrid, but I'm just into tubes for guitar preamp.
I'd like to build their theramin and add some kind of conversion to MIDI perhaps.
This looked interesting until I saw the schematic and all those op-amps. Probably an interesting hybrid, but I'm just into tubes for guitar preamp.
I'd like to build their theramin and add some kind of conversion to MIDI perhaps.
I might like to modify the envelope follower guitar kit and build it into a tube amp. Tap into the preamp just before after the first tube stage where the envelope hasn't been compressed, convert to voltage control, then a nice voltage controlled filter placed after the preamp, for when the preamp adds its own tonalities and distortion.
I don't see your problem?, it's got a valve in there to give the distorted valve sound, the opamps are mostly filtering and buffering (pretty impractical to do anywhere near as well with valves).
The big problem here is the plate supply voltage of 30V (see the inverters driving the diode-capacitor voltage multiplier circuit). I've read about this type of "low-voltage" tube preamp circuit before (also in the "Art Tube Pre"), it doesn't give the same type of distortion as with a 150 to 250V plate supply voltage.
There is that note on the schematic near the output of the multiplier, 30V; 10% tolerance. Doesn't make any sense to me either. I saw an article somewhere once that suggested using the flash supply from an old disposable camera. Something around 200-300V @ 2mA.
@ Printer2, check this thread at MEF: Charge pump for bias/switching supply?
I know you're a member there. Non-members won't see some of the attachments. A voltage octupler is used to make 56V @ ~1mA from 6.3VAC 60Hz.
I know you're a member there. Non-members won't see some of the attachments. A voltage octupler is used to make 56V @ ~1mA from 6.3VAC 60Hz.
Okay, looking again, that 30V 10% surely IS the cap rating. I found a similar circuit (the "inverter" plate supply circuit is the same) on page 25 that says 42V, though the text on page 24 says 45V:
http://www.paia.com/manuals/docs/9305-tubehead-manual.pdf
The open-circuit voltage may well be 75V, but with a CMOS inverter chip driving the voltage multiplier, it's easy to see how it can drop a lot with a few milliamps of loading.
There's more on "starved plate" tube circuit design here:
PAiA: Tube Sound?
Here's a thread that discusses some differences between the lower voltage "starved plate" design and "full" voltage design:
What Should Be The Cut Off For Calling a Circuit "Starved Plate" - Gearslutz.com
http://www.paia.com/manuals/docs/9305-tubehead-manual.pdf
The open-circuit voltage may well be 75V, but with a CMOS inverter chip driving the voltage multiplier, it's easy to see how it can drop a lot with a few milliamps of loading.
There's more on "starved plate" tube circuit design here:
PAiA: Tube Sound?
Here's a thread that discusses some differences between the lower voltage "starved plate" design and "full" voltage design:
What Should Be The Cut Off For Calling a Circuit "Starved Plate" - Gearslutz.com
Yes, I've had a dozen of those "starved plate" devices and it's not at all the tube sound I like. I had a 'blue tube' and a Chandler and several others. I don't find the sound meets my intent of being 'emotive'...going from realy clean to really complex by both how hard I pick and how many strings are involved.
I'm not really big on any power supply sag type of compression and its related distortion either.
Getting the sound I am pursuing involves a tube at that critical first stage of interaction between the coils and grid, then treble pre-emphasis, one or two more stages adjustable for the exact point of distortion generation, then treble de-emphasis. Usually at least 4 single-ended tube stages in a row at a minimum. If I get one stage to go in and out of distortion with my touch just as I prefer, I find it just sounds much better after the output's phase is shifted 90 degrees and repeats the process. I don't really know whether it's the effect on the waveform or the amount of compression, but IMHO blues is all about whatever sounds good, and IMHO it sounds good. I have nothing against op amps and transistors in their appropriate place, like in my accurate reproduction amps. But my guitar preamps are part of my instrument and sound generation. Perhaps the last stage for recovery of the gain lost in the final tone de-emphasis stage could be an op-amp. But I don't find een powered pickups work as well as a tube first stage, and that stage has to add enough gain for my preferred pre-emphasis. Then when the next stages do (or don't) add distortion, there is so ridiculously much treble that I can roll it off and make the treble less obnoxious and what we used to call 'creamy' yet still have plenty of treble content. The way the sound from multiple strings mixes in those treble-boosted distortion stages is incredible, and makes all kinds of interesting beat tones which become more prominent when you filter the excess treble out later. The original guitar sound goes thru pre-emphasis and somewhat matching (well, not exact) de-emphasis, but the disortion generated between only goes thru the final de-emphasis.
THAT's how to get the emotive guitar sound I prefer. It's not just tone, and it's not achieved by just adding a plate-starved distortion, generator or a saggy power supply.
And, with slight adjustment to the knobs and via playing technique, I can avoid generating distortion in those intermediate stages, and get a little gain at each stage and achieve a ridiculously beautiful clean treble sound.
Thinking like Nigel Goodwin makes for preamps like this PAiA and it's not bad, it's just not anything special IMHO and not worth my time building as it can't do what I require. I'd rather modify both channels of an Alembic preamp into one really special channel.
I'm not really big on any power supply sag type of compression and its related distortion either.
Getting the sound I am pursuing involves a tube at that critical first stage of interaction between the coils and grid, then treble pre-emphasis, one or two more stages adjustable for the exact point of distortion generation, then treble de-emphasis. Usually at least 4 single-ended tube stages in a row at a minimum. If I get one stage to go in and out of distortion with my touch just as I prefer, I find it just sounds much better after the output's phase is shifted 90 degrees and repeats the process. I don't really know whether it's the effect on the waveform or the amount of compression, but IMHO blues is all about whatever sounds good, and IMHO it sounds good. I have nothing against op amps and transistors in their appropriate place, like in my accurate reproduction amps. But my guitar preamps are part of my instrument and sound generation. Perhaps the last stage for recovery of the gain lost in the final tone de-emphasis stage could be an op-amp. But I don't find een powered pickups work as well as a tube first stage, and that stage has to add enough gain for my preferred pre-emphasis. Then when the next stages do (or don't) add distortion, there is so ridiculously much treble that I can roll it off and make the treble less obnoxious and what we used to call 'creamy' yet still have plenty of treble content. The way the sound from multiple strings mixes in those treble-boosted distortion stages is incredible, and makes all kinds of interesting beat tones which become more prominent when you filter the excess treble out later. The original guitar sound goes thru pre-emphasis and somewhat matching (well, not exact) de-emphasis, but the disortion generated between only goes thru the final de-emphasis.
THAT's how to get the emotive guitar sound I prefer. It's not just tone, and it's not achieved by just adding a plate-starved distortion, generator or a saggy power supply.
And, with slight adjustment to the knobs and via playing technique, I can avoid generating distortion in those intermediate stages, and get a little gain at each stage and achieve a ridiculously beautiful clean treble sound.
Thinking like Nigel Goodwin makes for preamps like this PAiA and it's not bad, it's just not anything special IMHO and not worth my time building as it can't do what I require. I'd rather modify both channels of an Alembic preamp into one really special channel.
I would just find a HV transformer and run the tubes at normal voltages. I tried tubes in the sub 100V range and do not care for it much. Mind you I want to try the 6SJ7 at about 100V to get a 30's - 40's amp sound. I did the back to back low voltage transformer thing, it works well enough for a preamp. As Loudthud says though, there is a bit of voltage drop from the primary resistance and the added turns they put in to get their voltage. Don't be tempted to feed a 6V transformer from a 12V one though, the 6V one seems to loos a lot of voltage and behaves badly a slight mismatch seems to work. I would just run a voltage doubler off the boost transformer. Should get an easy 250V.
I built a stack in a box several years ago and is a nice sounding preamp and the speaker simulators sound great. It doesn't have nearly enough gain but that can be fixed by nodding the gain of the input opamp.
I use mine as a preamp that then goes into a 15 band equalizer then into a dbx compressor/gate then into my diy 2 channel tube amp.
It's the only starved plate tube preamp I have tried that actually sounds like a real tube preamp.
Since then I have built several for friends who love them. You really need to use an equalizer offer as it lacks any tone controls.
Cheers
I use mine as a preamp that then goes into a 15 band equalizer then into a dbx compressor/gate then into my diy 2 channel tube amp.
It's the only starved plate tube preamp I have tried that actually sounds like a real tube preamp.
Since then I have built several for friends who love them. You really need to use an equalizer offer as it lacks any tone controls.
Cheers
I was looking at some Weber kits. I'd like to buy the Fender Twin copy and modify it to suit my tastes, convert both 2-input channels into one 1-input adjustable-gain channel, with a switch to bypass 1 stage. Would need to make my own panel w/ labels...
They sell reverb spring units made by Belton. How do they compare with Accutronics?
They sell reverb spring units made by Belton. How do they compare with Accutronics?
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