I'm tired of anemic guitar amps!

[Chuz Life]

I actually helped a guy at Fluke write some of the technical papers on it. The meter you see in the picture (big, fat, yellow thing) was actually used to troubleshoot a problem in Atlanta and saved the 1996 Olympics in Atlanta to go on in time.


Nah, I just run an old OS on that because it needs to run old software for special testing aps I use that originally came on a 3.5" floppy.

I was only joking about the laptop. I have one similar.

Motorola radio software (older models) was also on floppy disks and will not run on newer machines.

 

[scruffy]

I was probably going to ask for your recommendations on the caps (Brand)

My opinion on caps, the Sprague Atoms are the best, but they're pricey and physically large. They'll "barely" fit in a Fender cap can. I've been using the F&T caps because they're physically smaller. You have to be careful if you have an ultralinear or red knob Twin, the voltages are over 500 volts (plus there's some oddball caps in there). JJ now makes 550 volt caps, you can find them at amplified parts.com

 

[Chuz Life]

My opinion on caps, the Sprague Atoms are the best, but they're pricey and physically large. They'll "barely" fit in a Fender cap can. I've been using the F&T caps because they're physically smaller. You have to be careful if you have an ultralinear or red knob Twin, the voltages are over 500 volts (plus there's some oddball caps in there). JJ now makes 550 volt caps, you can find them at amplified parts.com

I'm going to have to educate myself on the "death cap."

 

[toobfreak]

Back in the late 70's to early 80's there were "DAC's" which radio stations relied on for recorded audio with no tape.

I thought that was a DAC

I thought they always used DATs. But all the DACs I saw were outboard units meant to upgrade inferior internal DACS, but it sounds like what you are talking about also recorded on a SS drive.

 

[Chuz Life]

Public Service Anouncement!

 

[Chuz Life]

I thought they always used DATs. But all the DACs I saw were outboard units meant to upgrade inferior internal DACS, but it sounds like what you are talking about also recorded on a SS drive.

You're right 100% I mixed things up pretty bad.

I never messed around with either one (DAT or DAC) but I was always intrigued.

 

[toobfreak]

I was only joking about the laptop. I have one similar.
Motorola radio software (older models) was also on floppy disks and will not run on newer machines.

If I had to guess, it still runs Win98. I also still run Win XP on my main computer using Parallels virtual machine to run a virtual OS within my OS to run other OSs. I still have some really special and expensive old software which is irreplaceable or at best, would be viciously expensive if bought new.

 

[toobfreak]

I never messed around with either one (DAT or DAC) but I was always intrigued.

DATs were pretty cool for early pro digital recorders but I never bought one.

I played around with a few outboard DACS (and their fancy interconnects) but was never impressed they were really worth the money.

 

[Chuz Life]

I have one of those Transoceanics with a B-17 on its face.

I spent way too much time listening to that damn nuclear time clock!

I'm sure it was a subliminal mind control signal.

 

[scruffy]

They are both 70's silverface with push pull master volume. The better sounding amp has chrome dome PYLE speakers than I doubt were factory.

Those are very good speakers. The chrome domes were their JBL clones.

For tubes, tubes are very subjective. With those speakers I could recommend a preamp tube, an Amperex "Bugle Boy" 12ax7. You'll get great highs out of that.

In general for current production I like JJ's, they're gritty and I like that response. They're not all perfect though, about 20% of them are weird so if you need 5, get 6. The Sovtek's to my ears are a little dark.

The newer cleaner looking amp has (I believe) celestion speakers. The newer one also has mixed tubes for finals due to one falling out and breaking at a gig. Though I can't remember the brands. One is a Sovtech, I think.

The output tubes are important. Each brand has a favorite bias setting. JJ's like 31/32 mA in Twins. Those pull-masters have an odd bias pot arrangement, you may have to tweak a resistor to get the best setting. Recommend schematicheaven.net for the versions.

 

[Chuz Life]

Those are very good speakers. The chrome domes were their JBL clones.

For tubes, tubes are very subjective. With those speakers I could recommend a preamp tube, an Amperex "Bugle Boy" 12ax7. You'll get great highs out of that.

In general for current production I like JJ's, they're gritty and I like that response. They're not all perfect though, about 20% of them are weird so if you need 5, get 6. The Sovtek's to my ears are a little dark.



The output tubes are important. Each brand has a favorite bias setting. JJ's like 31/32 mA in Twins. Those pull-masters have an odd bias pot arrangement, you may have to tweak a resistor to get the best setting. Recommend schematicheaven.net for the versions.

My intention is to take the crappier one of the two and true to get it as close to a blackface sound as I can. There is a guy who I kind of lost touch with that knows all sorts of mods and tricks. I'm hoping he will share some schematics.

 

[toobfreak]

I spent way too much time listening to that damn nuclear time clock!
I'm sure it was a subliminal mind control signal.

Speaking of nuclear clock signals, I had a pretty wild time once in Atlanta under the city near where CNN is trouble shooting a problem and after we found its cause, a guy from Lucent Technologies from New Jersey (the old Bell Labs where the cosmic background was first found and the transistor was developed) he flew in with a Stratum atomic clock, a cesium clock, I want to say Stratum III or IV but I don't remember.

It was a big hulking rack mount clock just barely manageable by one person and he used it as a time reference to confirm the problem where in effect, the input of the clocks used on our end of the master DS0 was chasing the output of the DS0 clock on the other end, failing to capture and lock to the other and the two just kept chasing the other never within the capture range to stabilize.

Fun times.

 

[Chuz Life]

Those are very good speakers. The chrome domes were their JBL clones.

For tubes, tubes are very subjective. With those speakers I could recommend a preamp tube, an Amperex "Bugle Boy" 12ax7. You'll get great highs out of that.

In general for current production I like JJ's, they're gritty and I like that response. They're not all perfect though, about 20% of them are weird so if you need 5, get 6. The Sovtek's to my ears are a little dark.



The output tubes are important. Each brand has a favorite bias setting. JJ's like 31/32 mA in Twins. Those pull-masters have an odd bias pot arrangement, you may have to tweak a resistor to get the best setting. Recommend schematicheaven.net for the versions.

True story about the amp with the Pyle speakers in it. . . when I was 9-10 years old, I was a traffic guard for my school.

My post had a bar on the corner and sometimes I would hear guitar being played in the bar! Lots of reverb and just playing. No singing.

On a dare, sometimes in the summer when both doors were open, we would run in the bar and then out the other door. LOL

Anyway, fast forward, I get out of the Marine Corps and decided I wanted a twin reverb.

I found one for sale in the paper and the younger guy selling it said the amp belonged to his uncle who had passed and said "he used to play at this bar" (same bar) that I was posted at.

I had to have it and still do.

 

[Chuz Life]

Speaking of nuclear clock signals, I had a pretty wild time once in Atlanta under the city near where CNN is trouble shooting a problem and after we found its cause, a guy from Lucent Technologies from New Jersey (the old Bell Labs where the cosmic background was first found and the transistor was developed) he flew in with a Stratum atomic clock, a cesium clock, I want to say Stratum III or IV but I don't remember.

It was a big hulking rack mount clock just barely manageable by one person and he used it as a time reference to confirm the problem where in effect, the input of the clocks used on our end of the master DS0 was chasing the output of the DS0 clock on the other end, failing to capture and lock to the other and the two just kept chasing the other never within the capture range to stabilize.

Fun times.

I love these kinds of stories that show how technology didn't used to be so "off the shelf" as it is more and more these days.

 

[scruffy]

Public Service Anouncement!

The problem is specifically this:

The death cap is BEFORE the mains fuse, in the circuit. If the cap ever goes you'll have a direct short through the power cable and the steel chassis. It'll put 115 vac on your ground. While not definitely fatal, it could sure be a nasty surprise.

If you compare the circuits for the three flavors of silver face twin reverb you'll see they're all the same.

Fender Amp Heaven Schematics - Tweed Blackface Brownface Silverface Bassman Champ Deluxe Princeton Super Vibroverb Reissue

Fender,Schematics, Amps, Amplifiers, Tubes, Valves, Bandmaster, Bandmaster Reverb, Bantam Bass, Bassman, Bronco, Champion, Champ, Vibro Champ, Concert, Deluxe, Deluxe Reverb, Harvard, Kauffman, Musicmaster, Princeton, Princeton Reverb, Pro, Pro Reverb, Quad Reverb, Reverb Unit, Showman, Dual...

schematicheaven.net

Now... you may ask yourself... why did Fender leave it in there? After all, they have a 3 wire line cord, they don't need a cap.

The answer is, because musicians played in old bars with 2-prong wiring, and the first thing they'd do is pull the ground pin out of the plug so it would fit in the 2-prong socket.

Or y'know, the bar owner could have gotten lazy and just not grounded the sockets. Musicians should carry one of those little 10 dollar socket tester gadgets from Home Depot. They'll light up if the ground is missing.

 

[scruffy]

My intention is to take the crappier one of the two and true to get it as close to a blackface sound as I can. There is a guy who I kind of lost touch with that knows all sorts of mods and tricks. I'm hoping he will share some schematics.

The main thing is to get rid of that awful pull boost!

Lemme see... blackface "sound". If you have the ultralinear version silverface, there's not much you can do about the voltages. They're going to be higher, they sound better that way, I would just leave them. The blackface has a choke while the ultralinear doesn't, you don't need a choke.

There's two quickie tone stack mods you could try (maybe use the disconnected pull switch on the master). First is, switch in a .0022 uf cap across the 250 pf treble cap. Second is, change the midrange control from 10k to 250k (make sure it's audio taper).

 

[scruffy]

These mods ^^^ work very well with darker tones. They can give you an ultra-fat rhythm guitar sound.

The ultralinears are meant to remain clean. In my experience the best thing to do with them is go for tonal range. A good thing to do is add a vari-tone circuit, for which you need a $10 coil you can get at DigiKey. The circuit is like a BC Rich guitar, or a Gibson GA-80 amp, it's just a notch filter.

 

[scruffy]

A couple of thoughts - as long as you have two of these - if it were me, I'd keep the good sounding one in original condition and use the other one as a modding platform. I'm going to guess you have the ultralinear version, it was most popular and very successful. This one:

https://schematicheaven.net/fenderamps/twin_reverb_sf_135_schem.pdf

If it's the one I think it is, it'll have a bunch of white wiring that looks a little messy. First thing is, disconnect all the wires to the pull boost, there's 4 of them, on the schematic the first half of the switch is to the right of v1b, it's across a 1 meg resistor. The other half of the switch is at the bottom left in the reverb circuit, coming off the top side of the reverb transformer. I would snip the wires on the other side.

Then, you have two channels - do you use them both? I never use the clean channel, just the reverb. So I disconnect the other side of the .047 capacitor coming off the plate of v1b, at the junction of the 220k resistor, and feed it into the input at v2a. Then I futz with the input jacks on the reverb channel, so when nothing is connected there and the guitar is plugged into the clean channel, the signal goes all the way through V1 and then through V2. This way v1 becomes kind of like a Dumblator. But if the guitar is plugged into the reverb channel instead, it's still the normal reverb channel.

This mod will give you way more gain than you need, and this is where the midrange mods really shine, because in high gain mode the first tone stack in v1 determines your gain character, and you'd like lots of mids and very little at the edges, that'll give you good responsiveness without bumblebees or ice picks. Then you still have the second tone stack for your overall sound.

 

[Chuz Life]

A couple of thoughts - as long as you have two of these - if it were me, I'd keep the good sounding one in original condition and use the other one as a modding platform. I'm going to guess you have the ultralinear version, it was most popular and very successful. This one:

https://schematicheaven.net/fenderamps/twin_reverb_sf_135_schem.pdf

If it's the one I think it is, it'll have a bunch of white wiring that looks a little messy. First thing is, disconnect all the wires to the pull boost, there's 4 of them, on the schematic the first half of the switch is to the right of v1b, it's across a 1 meg resistor. The other half of the switch is at the bottom left in the reverb circuit, coming off the top side of the reverb transformer. I would snip the wires on the other side.

Then, you have two channels - do you use them both? I never use the clean channel, just the reverb. So I disconnect the other side of the .047 capacitor coming off the plate of v1b, at the junction of the 220k resistor, and feed it into the input at v2a. Then I futz with the input jacks on the reverb channel, so when nothing is connected there and the guitar is plugged into the clean channel, the signal goes all the way through V1 and then through V2. This way v1 becomes kind of like a Dumblator. But if the guitar is plugged into the reverb channel instead, it's still the normal reverb channel.

This mod will give you way more gain than you need, and this is where the midrange mods really shine, because in high gain mode the first tone stack in v1 determines your gain character, and you'd like lots of mids and very little at the edges, that'll give you good responsiveness without bumblebees or ice picks. Then you still have the second tone stack for your overall sound.

Here are three examples of the tone I would really like to have. Check out the (guitar parts)







And also have the tone of SRV when I want it.

 

[scruffy]

Here are three examples of the tone I would really like to have. Check out the (guitar parts)

And also have the tone of SRV when I want it.

Okay, the first two are definitely doable with Twins. The third one is punchy, it has a lot of pick attack. I suspect there was a pedal involved, on that one. SRV is difficult to achieve with a single amp, as close as "I" get is the Dumblator concept with the gain set just on the edge of breakup. SRV used one of the Dumble's with the switchable Twin-T filters for midrange control, if you're feeling ambitious you could try that. He also used 15" speakers though, I think that was a big factor in his sound.