Thanks WDWC, I'm used to finding ap notes and specs on manufacturers web sites.
I guess Accutronics figures the tanks have been around so long people just copy the designs. (I got an 8AB2A1A1B but in retrospect should have gotten an 8AC2B1A1B as it would have had more output and required less buffer gain.)
I guess Accutronics figures the tanks have been around so long people just copy the designs. (I got an 8AB2A1A1B but in retrospect should have gotten an 8AC2B1A1B as it would have had more output and required less buffer gain.)
Funny, I have that schematic stored on my hard disk. I did copy the tremolo section for my Champ. I called it the 'chop chop suey' but now it's gone because I didn't use it that often (never).
I've never played with the 6BM8 but I know the ECL86. Good tube. I did build a guitar amp with an ECL86 and a 12AX7. The PCL86 is the same tube (much cheaper) but with a 13 volts heater voltage. I prefer the 6V6 so that amp is also gone.
As long as BST (OP) can find it, we're OK.
It's on their web site. Read everything under the "how reverb works" and also under "applications" at
::::::::: Accu Bell Sound Inc :::::::::
Also check here:
Antique Electronic Supply
then click on "spring reverb tanks explained and compared".
I'm working on a spring reverb also
Now one question. Yesterday I set up my Fender RV-5 reverb pedal in stereo. It has a left and right output. I put in two champ-like amps. For clean tones I really like the sound. It is dramatically different. Question: how to do that myself with springs. or any other DIY method.
I think the biggest problem with DIY reverb is getting the springs with the right coefficients that are long enough, then you have to figure out a torsion mechanism to twist the spring. The longest springs I've found that are light enough are only 3" long.
I've got a couple light springs and some piezo transducers, but after studying a bit I believe it won't "float a boat".
I switched from Pentode driver and triode amp to triode driver and pentode amp. Sounds much better, but I still need to tweak the frequency response.
The only way I can get a 6GH8 to operate as a Trem is with a current source in the anode. Otherwise it seems to have insufficient gain. It's not sand in the signal path, so from my understanding it would qualify. It is the only silicon based assistance in the amp so far other than rectifiers.
I've got a couple light springs and some piezo transducers, but after studying a bit I believe it won't "float a boat".
I switched from Pentode driver and triode amp to triode driver and pentode amp. Sounds much better, but I still need to tweak the frequency response.
The only way I can get a 6GH8 to operate as a Trem is with a current source in the anode. Otherwise it seems to have insufficient gain. It's not sand in the signal path, so from my understanding it would qualify. It is the only silicon based assistance in the amp so far other than rectifiers.
That should be fine. I specifically asked about certain uses of silicon IN the signal path early in this game and was told it was OK.
From post #38:
BST's reply in post #39:
The original thought was that if 12AX7's were priced out of range for this game I needed a method of getting 12AX7 gain out of a cheap TV or radio tuner tube. The 12AX7 has a Mu of 100. There are NO dual triodes with a Mu of 100 out there with LARGE numbers in stock anywhere that sell for $5 or less. The resistive loading found in the typical guitar amp gain stage manages to get a gain of 40 to 60 from a 12AX7.
There are lots of cheap TV tuner tubes out there with a Mu of 30 to 35 and a few radio tubes with a Mu of 50 to 60. You can never get a stage gain higher than the Mu of the tube, but you can come real close with a CCS load and a mosfet buffer so the tube sees a near infinite load.
The two 5 tube amps that I have made use odd heater variations of the ECC85 which have a Mu of 50. I used a mosfet buffer for each stage and had too much overall gain. I now have a mosfet buffer only for driving the volume pot and the tone stack. There is still too much gain but it sounds good. These tubes are rather microphonic, so I will be investigating some lower gain TV tuner tubes that are cheaper.
Triode section of a 6GH8 is 46, and the 6KE8 is 40. so with a current source in the anode and light load it should have about as much gain as a 12AX7 stage with normal guitar circuit loading.
On the other hand, I still don't see why the pentode will not oscillate as a tremelo unless I have a current source in the anode.
On the other hand, I still don't see why the pentode will not oscillate as a tremelo unless I have a current source in the anode.
Attachments
Not yet. So far all of the amps that I have built have used series wired heater strings, all running on DC derived from the low B+. In the 3 and 4 tube designs, the only B+. This works well allowing the use of an isolation transformer as the only power transformer. The venerable N-68X will power an amp up to the 10 watt power level for minimum money. For the bigger amps the Triad FD8-120 can be found for just over $20 and works for amps up to $35 watts. Both work on 120 or 240 volts. I like the 20 watt design and I will keep it, and make a case for it. I just can't pass up that cranked EL84 sound without the EL84 price.
The sweep tube version however has been voted off the workbench. I got some Antek toroids and am presently hacking up the board for operation with 6.3 volt parallel heaters. The triodes I am currently using are pin compatible with the 6ES8 and about 20 others. I only have 1 6ES8 in my stash, but I will try it. My first choice is the 6BQ7 / 6BK7 since there are over 10,000 of them in stock at my local (OK 200 miles away) tube store. I have used them before as an LTP in a HiFi amp. I don't know what to use for the output tubes yet. The 50 volt heater sweep tubes are out.
I am getting the urge to stuff 12AX7's and EL34's in the board and crank it up to about 450 volts just to see what happens
Well, then again may be... There are quite a few (perhaps they still do not meet your definition of LARGE number) Russian 6N2P's not to mention Chinese 6N2's around, the Mu is ~100, they go for $1-2 a piece, here is an example from eBay, but there are plenty others as well...
Jaz
It gets worse... If you study an actual spring reverb pane you find the each spring is really two springs in series and each is slightly different, one is slightly softer. They do this in order to create a reflection at the midway transition. Making it even harder to DIY each spring is wound in and opposite direction. So you'd need two springs one softer than the other and one clockwise and one counterclockwise and both "just right" for the desired echo time. I think it it's clear they custom make the springs
But why bother you can buy a Mod Reverb pan from Amazon.com for $18.00
Like everything else the best reason to DIY is to make something you can't buy. Years ago Hammond made complex spring reverbs that had large long "Y" shape springs to simulate the sound of a stone cathedral. No one sells these any more. The best way to build one would be to by a few of those $18 pans on Amazon and disassemble them for parts. Each pan has four transducers and two pairs of springs. I can't think of a cheaper why to get those parts and if you buy two shipping is free. You could be the only guy on the block to have a "Y" or "X" shape stereo spring reverb system
But then again "why bother"? Today the only reason to use springs is to re-create an authentic sound from the past. For any new kind of sound convolution reverb is the way to go.
Couldn't agree more, now days, reverb is much easily done with digital convolution, plus you can tweak it as much as you want... hard to do that with spring reverb inside the amp.
Jaz
Amazon lists the reverb tank, but they don't actually sell it. It "Ships from and sold by AmplifiedParts."
Amplified Parts is just another name for Antique Electronics Supply. AES seems to use at least 3 names that they do business under. It looks like AES and Amplified Parts sell their items for similar prices. They also operate CE Distribution which only sells to qualified businesses. Their prices are lower than the other two but a business license is required. CE sells the same tank for $12.25.
I'm not either since there is only one AES / CE part in my current BOM and that will likely be replaced as soon as I find something better (the OPT). I would like to use some of their $3.95 6L6GC's though. I already have them. I think a $1 sweep tube will work just as good though. There is only one way to find out.
It wasn't too hard to get "qualified" though, I just directed them to my website. That was enough. They sent me a login and password the next day.
Wow! This thread has taken wings since I last checked in, several weeks ago. Had to deal with multiple real-life responsibilities which pretty much precluded tinkering on the bench.
I finally unpacked my Edcor iron which had lain unopened for a while. Two each of the XPWRR014-120 power transformers, XC75-15H-75mA chokes, and GSXE10-4-5K output transformers. The OPTs were chosen to match up to the pair of 4-ohm 8" Peavey Blue Marvel guitar speakers I purchased on sale at PartsExpress.
I still plan on building a very basic variant of a time-proven design -- something along the lines of the simplest Fender Champ or Gibson Les Paul. It will have a 6SJ7G driving a 6EY6, with nothing other than a volume control, and perhaps a 'bright' switch. Still haven't decided whether to use a 5Y3 tube rectifier, or some of the BA159s in my parts stash.
As I've mentioned before, I'm still very green when it comes to electronics. My field of expertise is photochemistry and art conservation, so I'm pretty much out of my league here. I feel like a kid who just got his driver's license, and finds himself in a competition with a bunch of Formula 1 drivers.
All the same, I'm eager to finally start drilling holes and melting solder. Once I get a functional circuit on the breadboard (should be pretty quickly), I'll start tweaking values of caps and resistors until I get one which sounds good with the speaker I've chosen, and the basic pine box to enclose it.
I'm going to build a pair of amps at the same time. That way, any modifications I make to one will be easy to evaluate in comparison to the other, without having to rely on memory or recorded sound clips.
It looks like I'll be building these amps for fun and experience, but come October when all the dust has settled, I'll be building someone else's far-superior design for gifts to my guitar-playing friends.
I finally unpacked my Edcor iron which had lain unopened for a while. Two each of the XPWRR014-120 power transformers, XC75-15H-75mA chokes, and GSXE10-4-5K output transformers. The OPTs were chosen to match up to the pair of 4-ohm 8" Peavey Blue Marvel guitar speakers I purchased on sale at PartsExpress.
I still plan on building a very basic variant of a time-proven design -- something along the lines of the simplest Fender Champ or Gibson Les Paul. It will have a 6SJ7G driving a 6EY6, with nothing other than a volume control, and perhaps a 'bright' switch. Still haven't decided whether to use a 5Y3 tube rectifier, or some of the BA159s in my parts stash.
As I've mentioned before, I'm still very green when it comes to electronics. My field of expertise is photochemistry and art conservation, so I'm pretty much out of my league here. I feel like a kid who just got his driver's license, and finds himself in a competition with a bunch of Formula 1 drivers.
All the same, I'm eager to finally start drilling holes and melting solder. Once I get a functional circuit on the breadboard (should be pretty quickly), I'll start tweaking values of caps and resistors until I get one which sounds good with the speaker I've chosen, and the basic pine box to enclose it.
I'm going to build a pair of amps at the same time. That way, any modifications I make to one will be easy to evaluate in comparison to the other, without having to rely on memory or recorded sound clips.
It looks like I'll be building these amps for fun and experience, but come October when all the dust has settled, I'll be building someone else's far-superior design for gifts to my guitar-playing friends.