Simply put, the Ampeg B15 is a legend of the studio. This plus a Fender Precision Bass plus massive amounts of talent and persistence equals the legendary Motown sound. But, any passive old school bass sounds great on one of these. I've had the pleasure of working on many of these. This week offered a nice journey into 3 versions of this lovely amp.
First a 1963 model:
This one came from MSR studios in New York City. Countless artist probably recorded through this amp including the Stones, Talking Heads, Roberta Flack.....
This was the best of the 3. It's an early cathode bias version. Probably in the 25 watt range. What do I like about it? Punchy, great low mids, clear sound with a nice bit of growl.
This particular amp was sitting neglected for over a decade. It was a hot mess when I got into it. Random wires clipped, some components flopping about and the tag board burnt through where the cathode resistor resides. Typical, that resistor gets hot. Something blew up in this amp and the power transformer was also fried. This is typical too. I replace power transformers in about one of these a year. This year it's been 2 so far. Weak part I suppose. I didn't need to replace any of the Cornel Dublier caps, they are almost always still good. Surprisingly the circuit is dead quiet with all of the original resistors as well. They didn't mess around with making things cheap back then.
After replacing the power transformer and re-capping the power supply it roared back to life. Glad to say it's making music again in another studio. I'm stunned anyone would let this one just sit unused for that long. The tone is simply perfect. Loud enough for a small combo live too. But best suited for studio tracking.
The next one is a 1966 model:
Similar cosmetics, the differences are it's now a printed circuit board rather than the old school tag board. Ampeg did these so well that it's still fun and easy to get around in. It's also fixed/grid bias rather than self/cathode bias. Result is more power, more headroom, more 'clinical' sound. Haven't dug into this one yet but will be re-capping the power supply.
It doesn't hum so why re-cap it? Isn't it best to leave it original?
Short answer: no way. Just do it. Why?
First is safety. This amp is 51 years old. Caps fail. You don't want this happening.
Second is sound. I can always tell and feel the difference. Stronger low end and more even across the range. My clients agree. Most of them spend years listening carefully in the studio and they say the same thing. Amp got 'bigger' sounding.
Right now the amp sounds good, but we're going for great.
Amplified Parts (CE Distribution/Antique electronic Supply) makes brilliant caps for these. The grid bias amps require a 525 volt can and they also have a beautifully made 25uf@800V "firecracker" cap for the first stage.
Here's your can: https://www.amplifiedparts.com/products/capacitor-ce-mfg-525v-404040uf
And your firecracker:
https://www.amplifiedparts.com/products/capacitor-ce-mfg-800v-900v-surge-25-f-electrolytic
The firecracker cap saves a good amount of time on installation. I used to use the Sprague Blue Atom 20@600V cap, but you need to monkey around with stuff to make that work. These come with a wire tie and easy mounting. Takes a whopping 60 seconds to install.
Oh yeah, order this too:
https://www.amplifiedparts.com/products/insulator-4-section-fp-cap
Spend the extra $1.95. It's worth it.
Next photo is one I worked on last winter. It's a 1968 model. Similar 'drip edge' cosmetics to the Fender amps of that year. Pretty much the same amp as the '66 but with a new sexy look. Great amp.
I needed to replace the power transformer on this one as well. Full re-cap of the power supply. Powerful. Great live or studio rig.
The 3 amps above all have the original CTS speakers loaded into them. Still making music!
Last but not least is an early 70's model. These are great live amps and are a bargain:
This one also came from a studio that let it rot away. Didn't take much, power supply re-cap, new preamp tubes (6SL7) which were all dead. I left the signal caps alone in this one as well. 1/2 are the Cornel Dublier green pill types, the preamp is loaded with the turquoise little fish caps. 2 of the input jacks were opening up so with nothing plugged into the amp it squealed like a electric hog. I've seen people re-cap amps and go to all sorts of trouble when all that was needed was a good closed circuit Switchcraft 12 jack.
These late model amps have nice but not really necessary filter switches for 'ultra low' and 'ultra high'. These share the most similar sound to the SVT out of all of these, probably due to the preamp. More of an analytical sound than the amps above, less warm but still plenty of warmth. Not nearly as attractive, which is typical of the 70's designs over the 60's. But, this is the best live amp choice. Lots of power! This particular amp was loaded with an Eminence speaker and is now slated to be a live workhorse.
On all of the grid bias amps above, I installed a bias trimpot. Why not do this? They do tend to run quite hot. And hey, you may save the life of that very expensive power transformer:
http://www.mojotone.com/amp-parts/Transformers_1/Ampeg-B-15-Power-Single-Primary-Transformer
So if you have a serious recording studio, don't go without a real flip top. Even the B12SB amp is a fine choice for your bass tracks. I wouldn't buy a new one, there are so many good old ones around and they can be had for not too much. A late model can sell for less than a grand, middle period between $1.5k-$2k. Early ones can be a lot more but if you have the dough, a good tech or some good skills on the bench, you will not regret it.
JB
First a 1963 model:
This one came from MSR studios in New York City. Countless artist probably recorded through this amp including the Stones, Talking Heads, Roberta Flack.....
This was the best of the 3. It's an early cathode bias version. Probably in the 25 watt range. What do I like about it? Punchy, great low mids, clear sound with a nice bit of growl.
This particular amp was sitting neglected for over a decade. It was a hot mess when I got into it. Random wires clipped, some components flopping about and the tag board burnt through where the cathode resistor resides. Typical, that resistor gets hot. Something blew up in this amp and the power transformer was also fried. This is typical too. I replace power transformers in about one of these a year. This year it's been 2 so far. Weak part I suppose. I didn't need to replace any of the Cornel Dublier caps, they are almost always still good. Surprisingly the circuit is dead quiet with all of the original resistors as well. They didn't mess around with making things cheap back then.
After replacing the power transformer and re-capping the power supply it roared back to life. Glad to say it's making music again in another studio. I'm stunned anyone would let this one just sit unused for that long. The tone is simply perfect. Loud enough for a small combo live too. But best suited for studio tracking.
The next one is a 1966 model:
Similar cosmetics, the differences are it's now a printed circuit board rather than the old school tag board. Ampeg did these so well that it's still fun and easy to get around in. It's also fixed/grid bias rather than self/cathode bias. Result is more power, more headroom, more 'clinical' sound. Haven't dug into this one yet but will be re-capping the power supply.
It doesn't hum so why re-cap it? Isn't it best to leave it original?
Short answer: no way. Just do it. Why?
First is safety. This amp is 51 years old. Caps fail. You don't want this happening.
Second is sound. I can always tell and feel the difference. Stronger low end and more even across the range. My clients agree. Most of them spend years listening carefully in the studio and they say the same thing. Amp got 'bigger' sounding.
Right now the amp sounds good, but we're going for great.
Amplified Parts (CE Distribution/Antique electronic Supply) makes brilliant caps for these. The grid bias amps require a 525 volt can and they also have a beautifully made 25uf@800V "firecracker" cap for the first stage.
Here's your can: https://www.amplifiedparts.com/products/capacitor-ce-mfg-525v-404040uf
And your firecracker:
https://www.amplifiedparts.com/products/capacitor-ce-mfg-800v-900v-surge-25-f-electrolytic
The firecracker cap saves a good amount of time on installation. I used to use the Sprague Blue Atom 20@600V cap, but you need to monkey around with stuff to make that work. These come with a wire tie and easy mounting. Takes a whopping 60 seconds to install.
Oh yeah, order this too:
https://www.amplifiedparts.com/products/insulator-4-section-fp-cap
Spend the extra $1.95. It's worth it.
Next photo is one I worked on last winter. It's a 1968 model. Similar 'drip edge' cosmetics to the Fender amps of that year. Pretty much the same amp as the '66 but with a new sexy look. Great amp.
The 3 amps above all have the original CTS speakers loaded into them. Still making music!
Last but not least is an early 70's model. These are great live amps and are a bargain:
This one also came from a studio that let it rot away. Didn't take much, power supply re-cap, new preamp tubes (6SL7) which were all dead. I left the signal caps alone in this one as well. 1/2 are the Cornel Dublier green pill types, the preamp is loaded with the turquoise little fish caps. 2 of the input jacks were opening up so with nothing plugged into the amp it squealed like a electric hog. I've seen people re-cap amps and go to all sorts of trouble when all that was needed was a good closed circuit Switchcraft 12 jack.
These late model amps have nice but not really necessary filter switches for 'ultra low' and 'ultra high'. These share the most similar sound to the SVT out of all of these, probably due to the preamp. More of an analytical sound than the amps above, less warm but still plenty of warmth. Not nearly as attractive, which is typical of the 70's designs over the 60's. But, this is the best live amp choice. Lots of power! This particular amp was loaded with an Eminence speaker and is now slated to be a live workhorse.
On all of the grid bias amps above, I installed a bias trimpot. Why not do this? They do tend to run quite hot. And hey, you may save the life of that very expensive power transformer:
http://www.mojotone.com/amp-parts/Transformers_1/Ampeg-B-15-Power-Single-Primary-Transformer
So if you have a serious recording studio, don't go without a real flip top. Even the B12SB amp is a fine choice for your bass tracks. I wouldn't buy a new one, there are so many good old ones around and they can be had for not too much. A late model can sell for less than a grand, middle period between $1.5k-$2k. Early ones can be a lot more but if you have the dough, a good tech or some good skills on the bench, you will not regret it.
JB
Do you consider/worry about the higher line voltage today when re=capping these amps? I'm wondering if that is also an issue with the cathode biased amps.
ReplyDeleteI don't. Fortunately CE Manufacturing makes 525 volt cans and I've never had a problem. I do think it's very important to check the bias and run these rather conservatively as to not stress the tubes or transformers too much.
ReplyDeleteIt's not a bad idea to try a 300 ohm cathode resistor on the early models. These do tend to run quite hot.
I should mention too, the new power transformers are meant for 120v line as well so in the end it eliminates the concern for the old 110v part.
Thanks for asking! Very good question. J
I should mention though, the CE cans are expensive and over the last decade and a half I've had only 2 that went bad. I'm extra careful about juicing them up. I use a variac and usually a solid state substitute rectifier. I'll let it sit at 30 volts for a few hours before cranking it to 60. I usually let it sit overnight around there before bringing it up to 120. I monitor it as well. A bit excessive it may seem but if it helps me from potentially ruining an expensive part, it's worth it. J
ReplyDeleteI should mention that I plan to use the original transformers if I can. I toyed with the idea of a different rectifier but dismissed it as it brings in many other variables to worry about and I don't know all the specs on these old parts.
ReplyDelete