Last things first: Here's the schematic.
Note the two different B+ voltages, both derived from a single 48V Hammond power transformer. The 150V is from voltage doubling the transformer output, the 220V is from a voltage tripler. The doubler makes a negative 150V, but the negative rail is my "ground". The tripler is then easily made by simply adding a positive half-wave rectifier to produce roughly +75V. If that's not clear, let me know, I'll draw up the power supply schematic.
The tone control is straight from Merlin Blencowe's preamp design book. It's the "Bandmaster" circuit. I think I prefer the Voight tone control I was using before - the Bandmaster was an experiment to see if I preferred it (I don't). It's easy enough to swap out the tone control circuit to suit your preference.
The 270uF, 330V caps are surplus photoflash caps from disposable cameras. Affordable, low ESR, lots of capacitance for excellent ripple filtering. (With the input shorted and gain and volume at full, all I can hear is hiss, no hum.)
The other part of the "no-hum with shorted input" result comes from using a small thrift-store 8.4 V switching power supply to power the heaters, with a series resistor to drop the voltage to 6.3 V . I did not add any additional filtering for the heater power - it doesn't seem to be necessary. These days, it's simpler and cheaper to power the heaters with DC. With no AC current to create hum, heater wiring becomes very straightforward, no black arts necessary.
Between the gain and master volume controls, a range from squeaky-clean to early classic-rock distortion is available, at any volume, since it's all preamp distortion. Somewhere in between, there are some gain settings that create an interesting bit of compression, which sometimes sounds like a bit of slap-back delay.
I used fairly low voltage (around 25V) ceramic caps for both cathode bypass locations. The 10uF one (from Mouser) is only about the size of a match-head!
-Gnobuddy
Note the two different B+ voltages, both derived from a single 48V Hammond power transformer. The 150V is from voltage doubling the transformer output, the 220V is from a voltage tripler. The doubler makes a negative 150V, but the negative rail is my "ground". The tripler is then easily made by simply adding a positive half-wave rectifier to produce roughly +75V. If that's not clear, let me know, I'll draw up the power supply schematic.
The tone control is straight from Merlin Blencowe's preamp design book. It's the "Bandmaster" circuit. I think I prefer the Voight tone control I was using before - the Bandmaster was an experiment to see if I preferred it (I don't). It's easy enough to swap out the tone control circuit to suit your preference.
The 270uF, 330V caps are surplus photoflash caps from disposable cameras. Affordable, low ESR, lots of capacitance for excellent ripple filtering. (With the input shorted and gain and volume at full, all I can hear is hiss, no hum.)
The other part of the "no-hum with shorted input" result comes from using a small thrift-store 8.4 V switching power supply to power the heaters, with a series resistor to drop the voltage to 6.3 V . I did not add any additional filtering for the heater power - it doesn't seem to be necessary. These days, it's simpler and cheaper to power the heaters with DC. With no AC current to create hum, heater wiring becomes very straightforward, no black arts necessary.
Between the gain and master volume controls, a range from squeaky-clean to early classic-rock distortion is available, at any volume, since it's all preamp distortion. Somewhere in between, there are some gain settings that create an interesting bit of compression, which sometimes sounds like a bit of slap-back delay.
I used fairly low voltage (around 25V) ceramic caps for both cathode bypass locations. The 10uF one (from Mouser) is only about the size of a match-head!
-Gnobuddy
Attachments
From a quick look at the datasheets, the pentode in the 6BL8 is pretty different from the one in the 6JW8. I don't think the bias points will translate directly - but I would love to know what values you end up with!
-Gnobuddy
I understand you very well. If I let myself go, I suffer from the same problem, to the same degree. I've already spent a year and a half working on the power amp and clean channel of this thing!
(Though admittedly, I was drowning in too much work a lot of the time, and did not have much free time since last summer, a year ago.)
Still, if I keep going the same way, I might die of old age before I finish this amp.
So I decided to more or less call an end to the clean channel R&D, and move on to the "drive" channel.Interestingly enough, I found out recently that perfectionism is now classified by mental health professionals as a depressive disorder!
That got my attention, but makes perfect sense when you think about it - if nothing is ever good enough, how can one be happy about anything?A big perfectionistic streak is baked deep into my personality, and it's not going to disappear without a long fight, and maybe not even then. But at least now I know that I shouldn't take it too seriously, and should tell it to go take a nap every now and then!
-Gnobuddy
Good idea. Okay, I can summon up a few reference amps. I have a Fender Princeton Reverb and a Super Champ XD. I also have a little solid-state P.A/acoustic guitar amp (nominally flat frequency fresponse, full range). Maybe those three will serve as baseline amps to keep me straying too far from sanity.
I don't have a good "rawk" amp - but Printer2's mini-5E3 clip might be a usable reference for me, I just have to remember to go back and re-listen to it periodically. There are some nice 18W Marshall clips to be found online, too.
I had a similar experience with the Super Champ XD. It's a hybrid amp with a solid-state mixed analog/DSP preamp, and an actual valve power amp very similar to a Princeton's.
I never really warmed up to the various modelled distortion sounds on the drive channel. The clean channel seems to use the DSP only for voicing and tone/volume/FX, with no added harmonic distortion - the result is an almost perfectly clean amp. A bit blah with most guitars, but it sounds sweet with my (335-inspired) Agile AS-820 semi-hollow guitar.
I had to laugh at that.
I'm less than an hour from the heart of Vancouver and it's cultural sophisticates - but, as it turns out, that is far enough to put me deep into country and bluegrass territory!So that's part of the problem for me, too. Most of my musical friends here are only interested in strumming acoustic guitars, and most will only play in the keys of G major, A major, E major, and D major.
Barre chords? What are those? Minor chords? There are only two of them, E-minor and A-minor. All other minors are unplayable, everyone knows that. I have one musician acquaintance here who plays electrics, but I actually detest his ear-piercing, headache-inducing guitar tone. So he's not the right "test driver" for me, since we have totally different tastes in guitar tone. He uses what may be the worst-sounding guitar amp I've ever heard, a brittle-as-broken-glass solid-state Fender Acoustasonic, which makes babies cry and grown men run away screaming, with their fingers in their ears.
-Gnobuddy
See the thread "Lo budget, good sound" for an example.
JimG
PS. As a retired mental health professional I could go right off topic on the subject of who makes their own tube amps
.My colleagues were very polite about my hobby, but a little worried as one of my clinical specialties was electro-convulsive therapy
I need to modify the above statement to fit my personal issue......If nothing is ever good enough, how can one ever finish a project.
With a serious case of ADD that I have fought ever since childhood and a serious perfectionist streak, I still have serious issues finishing something. I will get something half finished, then figure out a better way, and rip it up to make it 'better". The process repeats until frustration kills the project.
41 years of working as an engineer, surrounded by as many as 1000 other engineers (during the plant's good times) makes for some long design cycles. I finally found a research department where I could go off by myself and build prototypes, since nobody else wanted to do that and I found it rather enjoyable.
Being surrounded by hundreds of electrical engineers most of whom were too young to recognize a tube, except for the guitar players, gets strange reactions. I walked into a meeting one day with a slide showing the schematic of a vacuum tube HP audio oscillator, put it on the screen and asked if anyone recognized the design.......dozens of blank stares. I pointed out the obvious clue, the copyright date, still nothing. One guy who was educated in Cuba in the 70's, did ask if the active devices were tubes.
It is hard to realize that there are plenty of well educated people who don't realize that CD's, IC chips, and iPOD's didn't ALWAYS exist. It is also a wake up call when someone asks who the people are on my Abbey Road T shirt, and stare blankly when I reply that this 8 track tape lived in the tape player for most of my senior year of high school. "1970, I wasn't even born yet!"
It's about 80 miles to Pittsburgh Pennsylvania, but I rarely go there due to the traffic.
I went to the local Symphony last winter when they played behind a travelling 5 piece "classic rock" band playing covers of Moody Blues, ELO, Jethro Tull, and Yes songs. The music director of our church plays violin in that symphony, but he refused to be a part of that show. I thought it was excellent, but the audience was mostly my age or older, except for the few that brought kids and grandkids. I haven't met anyone here yet who plays anything that I am interested in, and my tastes run pretty broad.
The symphony will do a "tribute to the beatles" next year, I might go see it.
Concerts & Tickets - Wheeling Symphony Orchestra : Wheeling Symphony Orchestra
Thanks for reminding me. I did read that thread months ago, but forgot which valve you were using.
That might make for an entertaining thread in the off-topic forum (The Lounge).As a retired mental health professional I could go right off topic on the subject of who makes their own tube amps
I would guess all of us on this forum are a few standard deviations away from the population median in many respects.
I must add that I'm doing my best to avoid any involuntary self-inflicted electro-convulsive therapy!
-Gnobuddy
That exact problem has completely killed my song-writing attempts for the last few years. The critical internal editor seems to be the death-knell to any kind of artistic endeavour, even more than to technical endeavours.
However, in the same period, I've written a few parodies - those came quickly and easily. The idea there is to write a bad song, so of course, there's no pressure to make it perfect!
Perhaps we should have a thread on building the worst possible guitar amp? That would get us perfectionistic basket-cases unstuck!
(We would have to declare the Fender Acoustasonic inadmissible, otherwise it would win by a landslide.)
-Gnobuddy
I was wandering the flea market at the Orlando hamfest a few years ago when I spotted a guy with 6 small guitar amps in various states of disassembly or destruction. When he said that I could have them all for $25 I grabbed them. He stated that a friend had experimented on them, or tried to fix them or?????
I was looking at using the cabinets and maybe speakers, so I didn't much care about the solid state electronics. There were two Fenders, both with identical looking sealed cabinets containing a 6 or 8 inch speaker.
One was a G-DEC which stood for Guitar Digital Entertainment Center.....WTF??? It didn't turn on. The Kill-A-Watt showed that it consumed about a watt of power when the switch was on, but no lights AND nobody home. I opened it up to find in addition to the fuse in the rear panel mounted fuseholder, there was a tiny fuse soldered in place on the PC board that was blown. I replaced it with a scrap of wire, and the amp worked. The G-DEC is sorta like the guitar equivalent of a Karaoke machine, but it only had about 15 songs (patterns). Each pattern had digitally synthesized drums, bass, and sometimes chords. There was a key switch to change the key of the song, and a tempo knob. There was another knob for a dozen or so preset (DSP?) effects from mellow to metal for the lead guitar. So, what's not to like......UH, the sound. Feed it anything with a bottom end and the sealed speaker cabinet boomed like a kids Honda......rattling license plate and all. I grew tired of it after the novelty wore off and gave it to a friend. I think he had it for 2 or 3 months.
The other Fender was a small Frontman. Oddly the only issue with it was the fact that someone had disconnected the internal speaker and twisted some speaker wire onto the amp output and then forced the back cover on with the wire pinched between the mating panels. The wire had shorted out, but the amp had not blown. Reconnecting the internal speaker revealed the same crappy sound that the G-DEC had.....without the "entertainment."
So the Acoustasonic was not the only turd in Fender's punchbowl.....Have you seen the Marshall refrigerator and the Bluetooth sound bar? More Chinese stuff polluting a respected brand name.
Out of those 6 amps the only one that I was willing to move 1200 miles was a Crate. The solid state PC board had been the victim of some serious hacking attempts that went really wrong, but there was a decent 10 inch speaker and a reverb tank in a nice looking rather heavy cabinet......worth the $25.
I wouldn't even call what I do songwriting. I just play around with a guitar, a keyboard, a MIDI controller and a DAW......then I play back the results of a few nights worth of messing around.....and delete it. Can't seem to get past that part. Those Youtube videos make it look easy.....yeah right.
I will say that I'm still rather happy with Amp 1.5. I rolled through a bunch of input tubes until I found one that was rather non microphonic, and I plan to keep the amp head away from the speaker cabinet. I will explore the whole "pentode saturator" concept further, but I think that trying to squeeze 50 to 60 db of voltage gain into a single stage WAS the bridge too far.........
Marshall Fridge | Home : Marshall Fridge
https://www.marshallheadphones.com/mh_us_en/speakers
I was looking at using the cabinets and maybe speakers, so I didn't much care about the solid state electronics. There were two Fenders, both with identical looking sealed cabinets containing a 6 or 8 inch speaker.
One was a G-DEC which stood for Guitar Digital Entertainment Center.....WTF??? It didn't turn on. The Kill-A-Watt showed that it consumed about a watt of power when the switch was on, but no lights AND nobody home. I opened it up to find in addition to the fuse in the rear panel mounted fuseholder, there was a tiny fuse soldered in place on the PC board that was blown. I replaced it with a scrap of wire, and the amp worked. The G-DEC is sorta like the guitar equivalent of a Karaoke machine, but it only had about 15 songs (patterns). Each pattern had digitally synthesized drums, bass, and sometimes chords. There was a key switch to change the key of the song, and a tempo knob. There was another knob for a dozen or so preset (DSP?) effects from mellow to metal for the lead guitar. So, what's not to like......UH, the sound. Feed it anything with a bottom end and the sealed speaker cabinet boomed like a kids Honda......rattling license plate and all. I grew tired of it after the novelty wore off and gave it to a friend. I think he had it for 2 or 3 months.
The other Fender was a small Frontman. Oddly the only issue with it was the fact that someone had disconnected the internal speaker and twisted some speaker wire onto the amp output and then forced the back cover on with the wire pinched between the mating panels. The wire had shorted out, but the amp had not blown. Reconnecting the internal speaker revealed the same crappy sound that the G-DEC had.....without the "entertainment."
So the Acoustasonic was not the only turd in Fender's punchbowl.....Have you seen the Marshall refrigerator and the Bluetooth sound bar? More Chinese stuff polluting a respected brand name.
Out of those 6 amps the only one that I was willing to move 1200 miles was a Crate. The solid state PC board had been the victim of some serious hacking attempts that went really wrong, but there was a decent 10 inch speaker and a reverb tank in a nice looking rather heavy cabinet......worth the $25.
I wouldn't even call what I do songwriting. I just play around with a guitar, a keyboard, a MIDI controller and a DAW......then I play back the results of a few nights worth of messing around.....and delete it. Can't seem to get past that part. Those Youtube videos make it look easy.....yeah right.
I will say that I'm still rather happy with Amp 1.5. I rolled through a bunch of input tubes until I found one that was rather non microphonic, and I plan to keep the amp head away from the speaker cabinet. I will explore the whole "pentode saturator" concept further, but I think that trying to squeeze 50 to 60 db of voltage gain into a single stage WAS the bridge too far.........
Marshall Fridge | Home : Marshall Fridge
https://www.marshallheadphones.com/mh_us_en/speakers
A friend's husband had a GDEC. He loved it, but I didn't find the cold, dead-sounding MIDI backing tracks very appealing.
There is also a tiny Squier amp (it comes with those all-in-one guitar+amp starter packages) that sounds utterly dreadful. I think when you shrink an open-back cab down to eight inches by eight inches by four inches, you end up with a huge collection of standing wave resonances in a frequency band where our ears are very sensitive to them. Add in savage bass roll-off from the acoustic short-circuit between front and back of the speaker, and there is nothing left to cover over the awful sonic warts.
In my preamp, I went to some effort to keep the gain of the pentode stage down. The anode load is relatively small, the B+ is low at around 140V, and anode current is around 1.2 mA, not down in the weeds like vintage pentode preamp stages.
All this keeps gain and output impedance in the same in the same ballpark as the typical 12AX7 stage, so I could bolt on a tone-stack without needing a buffer, etc.
On a slightly different topic (but related to the excess gain/ noise/ microphony issue) I did a few back-of-the envelope noise calculations, and it seems as though a JFET might do substantially better than a typical input valve stage when it comes to input noise. Flicker noise is the main issue in both devices, but it seems that some JFETs have much lower flicker noise (in the guitar's frequency range) than a typical small-signal triode or pentode.
Mebbe a JFET clean input stage configured for a fairly low voltage gain, before the signal hits the pentode saturator?
I think I might soon have my own battles with microphony, when I start working on the higher-gain channel of my preamp design. The clean channel is triode-pentode (one 6JW8). For the higher gain channel, the plan is to go triode -> triode -> pentode; the first triode shared with the clean channel, the other two stages in a separate 6JW8 bottle. That should make for easy channel switching, since the two channels are virtually independent of each other.
I spent a couple of hours laying out and drilling a lot of holes in a strip of aluminium. Now I have a temporary front panel with enough holes to accommodate all the pots for both channels, so the design / R&D work can begin. (I'm still short of holes for switches!)
-Gnobuddy
There is also a tiny Squier amp (it comes with those all-in-one guitar+amp starter packages) that sounds utterly dreadful. I think when you shrink an open-back cab down to eight inches by eight inches by four inches, you end up with a huge collection of standing wave resonances in a frequency band where our ears are very sensitive to them. Add in savage bass roll-off from the acoustic short-circuit between front and back of the speaker, and there is nothing left to cover over the awful sonic warts.
Perhaps you could get the same sonics (and less unwanted side-effects) with a little bit of clean gain ahead of the pentode, and a bit less gain in the pentode-saturator stage?
In my preamp, I went to some effort to keep the gain of the pentode stage down. The anode load is relatively small, the B+ is low at around 140V, and anode current is around 1.2 mA, not down in the weeds like vintage pentode preamp stages.
All this keeps gain and output impedance in the same in the same ballpark as the typical 12AX7 stage, so I could bolt on a tone-stack without needing a buffer, etc.
On a slightly different topic (but related to the excess gain/ noise/ microphony issue) I did a few back-of-the envelope noise calculations, and it seems as though a JFET might do substantially better than a typical input valve stage when it comes to input noise. Flicker noise is the main issue in both devices, but it seems that some JFETs have much lower flicker noise (in the guitar's frequency range) than a typical small-signal triode or pentode.
Mebbe a JFET clean input stage configured for a fairly low voltage gain, before the signal hits the pentode saturator?
I think I might soon have my own battles with microphony, when I start working on the higher-gain channel of my preamp design. The clean channel is triode-pentode (one 6JW8). For the higher gain channel, the plan is to go triode -> triode -> pentode; the first triode shared with the clean channel, the other two stages in a separate 6JW8 bottle. That should make for easy channel switching, since the two channels are virtually independent of each other.
I spent a couple of hours laying out and drilling a lot of holes in a strip of aluminium. Now I have a temporary front panel with enough holes to accommodate all the pots for both channels, so the design / R&D work can begin. (I'm still short of holes for switches!)
-Gnobuddy
That was my next plan. The breadboard was about halfway wired up when I left on a 15 day road trip. Now that I'm back I see that there is a 6JW8 in the socket. I chose that tube mainly because There is a box full of them and others with the same pinout to roll through the board when its built. I didn't quite remember which one wound up in the socket.
The next experiment will aim for a triode first stage followed by the pentode. Haven't thought much beyond that, and even that may change......I got a couple of really DUMM ideas to test.
Jfets.....I think I have some of those in the modular synth box of parts. I haven't played with jfets in like 30 years or so...and I think my parts are at least that old. Maybe I'll try one or two.
Last edited:
Good choice!
I like some things about this particular tube/valve for audio preamp use, i.e., tube parameters fall in a useful and easy-to-use range. The $1 price is nice too.
The only minor downside (to my ears, I don't have THD measurement capability yet) is that my 6JW8 triode gain stage sounds very, very clean, cleaner than a similar 12AX7 stage. My guess is that this is because the internal anode resistance (ra) is quite low, so that even a reasonably low external anode resistance Ra acts almost like a constant current source, and you get a very linear transfer function.
In other words, if Ra >> ra, one gets very little nonlinear distortion out of a triode, and it's hard to avoid this situation with the 6JW8's triode section, because ra is quite low.
I do like the sounds from the "pentode", though. (It appears to actually be a beam tetrode.)
It's been a while for me too, though I remember tinkering with some JFET audio circuits around 1997.
I know JFETs are nearly extinct now, but from the engineering point of view, they do seem to be the optimal device for a guitar amp input stage. They easily meet the input impedance requirements, and some have very low input noise (including flicker noise) at guitar pickup levels of source resistance.
Sorry about the late reply, life got suddenly busy for a few days.
-Gnobuddy
See what happens when someone tries something different. An old thread with Trout modifying the circuit of a Fender Tweed amp. Took it a little further.
What the heck, nothing better to do with my life. If you look real close you can see a 5E3 Deluxe happening, well that is if you look real close and turn your head sideways.
Love these mini four pole toggle switches. In the as shown position the circuit is an octal 5E3. The way I figure it most go through the bright channel anyway and load the channel with the normal channel pot. Really does not matter if the 'Normal' channel has a Pentode or volume pot as a resistive divider. You may loose out loading the bright channel from 500k to 1M, not a great loss. Otherwise you can turn the pot down to zero loading down the other channel. If you want to use the 6SJ7 channel at some time all the power to you.
Now say you want to try something a little different from the 5E3 dirt, how about a James control tone stack going into a pentode? Should give a few more tone options. Have it going into a single ended output, I have a lot of SE OT's. Think the circuit is right but if I missed something...
What the heck, nothing better to do with my life. If you look real close you can see a 5E3 Deluxe happening, well that is if you look real close and turn your head sideways.
Love these mini four pole toggle switches. In the as shown position the circuit is an octal 5E3. The way I figure it most go through the bright channel anyway and load the channel with the normal channel pot. Really does not matter if the 'Normal' channel has a Pentode or volume pot as a resistive divider. You may loose out loading the bright channel from 500k to 1M, not a great loss. Otherwise you can turn the pot down to zero loading down the other channel. If you want to use the 6SJ7 channel at some time all the power to you.
Now say you want to try something a little different from the 5E3 dirt, how about a James control tone stack going into a pentode? Should give a few more tone options. Have it going into a single ended output, I have a lot of SE OT's. Think the circuit is right but if I missed something...
little SE OTs
I too have quite a few little SE OTs from junk R-R recorders.
I made a few Champ amps from them but found I like this circuit better.
EF86 - 6L6 at +250V for B+, puts out @ 6.5W according to DS.
It is a very clean sounding, simple circuit, with much better sound than a Champ IMHO. More powerful too.
If you want dirt, you just need to put your favorite distortion pedal on the input.
I've used a 2.5A 12VDC laptop PS rescued from the trash.
It powers the heaters and an $8 Chinese DC-DC step up board.
A very inexpensive build, that sounds outstanding to me.
I too have quite a few little SE OTs from junk R-R recorders.
I made a few Champ amps from them but found I like this circuit better.
EF86 - 6L6 at +250V for B+, puts out @ 6.5W according to DS.
It is a very clean sounding, simple circuit, with much better sound than a Champ IMHO. More powerful too.
If you want dirt, you just need to put your favorite distortion pedal on the input.
I've used a 2.5A 12VDC laptop PS rescued from the trash.
It powers the heaters and an $8 Chinese DC-DC step up board.
A very inexpensive build, that sounds outstanding to me.
Attachments
The pentode can be switched to be either an input stage, or a second amplification stage? Interesting idea!
How are you liking the James tone control? In LTSpice, I found the passive James circuit simulates rather badly (with very assymmetrical boost/cut behaviour), which has discouraged me from building one.
The passive Baxandall seems to have the same problem, i.e. extremely different boost and cut characteristics.
I've recently tried the Fender Bandmaster tone control circuit (from Merlin Blencowe's book), and wasn't thrilled with it, as the controls are quite interactive.
I also tried a modified version of the Voight tone control circuit from Blencowe's book, and liked that one better. The controls interact less, cut and boost are pretty symmetrical, so it's easier to dial in the tone you want. (I posted my version of the circuit earlier in this thread.)
I think an active Baxandall with an LND150 MOSFET would be a little bit of an improvement over the Voight, but it's a lot of additional complexity for a subtle benefit...may not be worth it.
-Gnobuddy
Last night I read a review for a Rivera 6V6 based all-tube guitar amp which is a bit unusual: it's has one channel designed for an acoustic/electric guitar to plug into, and a second channel intended for an electric guitar to plug into.
The speaker complement is also a bit unusual for a valve guitar amp, in that it includes a (liquid-cooled, for high power handling) dome tweeter.
Sweetwater is selling the amp in question: Rivera Sedona Lite 25 - 25W 1x10" Acoustic and Electric Combo | Sweetwater.com
The Rivera is most definitely not a $100 amp, but I think the two-in-one concept is interesting - and I'm sure one of us could build something along these general lines for much less money. The Rivera is $1800, maybe we could do it for $180? That would fit the original concept of this thread well.
I have actually been planning to build something similar for a friend with a physical handicap; it's hard enough for him to deal with one guitar amp, much less two, plus a small P.A. for his vocals. So I've been thinking about a three-in-one acoustic guitar, vocal PA, electric guitar amp for him. For him, it has to be relatively small and light, so solid-state is almost unavoidable.
But I think many of us play both acoustic and electric guitar, and a dual-purpose valve guitar amp that can handle both would be a nice thing to have. I know I would appreciate only having to buy one speaker, build one cab, and carry one amp to jams. Not to mention one amp taking up less room in our little apartment.
I have also been thinking about using a tweeter (or small midrange driver) in an electric guitar amp for a very different reason: a typical big guitar speaker is absurdly directional at high frequencies, so the guitar tone varies dramatically off-axis.
Crossing over to a smaller driver (midrange or tweeter) and then rolling off high treble above 5 or 6 KHz with an additional low-pass filter in the crossover network - would avoid that problem.
The hard part is finding a suitable small midrange/tweeter that has enough sensitivity to match a typical guitar speaker, and which will go down low enough to crossover at 1 KHz or so. (Rivera actually has their tweeter custom-built for them!)
Maybe there is a relatively small paging/public-address speaker out there that is sensitive enough for the job? Anyone know of a suitable affordable candidate?
-Gnobuddy
The speaker complement is also a bit unusual for a valve guitar amp, in that it includes a (liquid-cooled, for high power handling) dome tweeter.
Sweetwater is selling the amp in question: Rivera Sedona Lite 25 - 25W 1x10" Acoustic and Electric Combo | Sweetwater.com
The Rivera is most definitely not a $100 amp, but I think the two-in-one concept is interesting - and I'm sure one of us could build something along these general lines for much less money. The Rivera is $1800, maybe we could do it for $180? That would fit the original concept of this thread well.
I have actually been planning to build something similar for a friend with a physical handicap; it's hard enough for him to deal with one guitar amp, much less two, plus a small P.A. for his vocals. So I've been thinking about a three-in-one acoustic guitar, vocal PA, electric guitar amp for him. For him, it has to be relatively small and light, so solid-state is almost unavoidable.
But I think many of us play both acoustic and electric guitar, and a dual-purpose valve guitar amp that can handle both would be a nice thing to have. I know I would appreciate only having to buy one speaker, build one cab, and carry one amp to jams. Not to mention one amp taking up less room in our little apartment.
I have also been thinking about using a tweeter (or small midrange driver) in an electric guitar amp for a very different reason: a typical big guitar speaker is absurdly directional at high frequencies, so the guitar tone varies dramatically off-axis.
Crossing over to a smaller driver (midrange or tweeter) and then rolling off high treble above 5 or 6 KHz with an additional low-pass filter in the crossover network - would avoid that problem.
The hard part is finding a suitable small midrange/tweeter that has enough sensitivity to match a typical guitar speaker, and which will go down low enough to crossover at 1 KHz or so. (Rivera actually has their tweeter custom-built for them!)
Maybe there is a relatively small paging/public-address speaker out there that is sensitive enough for the job? Anyone know of a suitable affordable candidate?
-Gnobuddy
There are some nice low-midrange 6.5-inch speakers on the market, for instance
18 Sound 6ND410
Monacor SP6-100/PA
Last edited:
Tweeter and electric guitar are not compatible, at least to my liking..
Given the huge attack in the highs of an E guitar not using a tweeter is a way to spare the player becoming progressively deaf, most guitar players i know have audition problems, myself as KBoard player i was always carefull to be far from the guitarist amp or from the crash cymbals...