My favorite amp ever is a mid century tube PA

LPVM

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Messing around with my 1947 Masco MA25P last night.

It's a 25 watt tube PA, all loctal preamp: 2 x 7B4, 7N7 & 7F7. They are a bit unusual.



The power section currently has a pair of RCA 6L6GC black plates in it and the rectifier is a 5U4. It's 2 primary channels are set up with channel one voiced deep and channel two brighter with a bit more gain. They are internally linked so you turn up channel two for the level of crunch you want then bring up channel one to fill in the bottom. The turntable is disconnected but that channel works too but is very low gain. I put a jack in the back of the amp that is connected to that and have plugged an iPod into it and have played along with it but don't really use that for the most part. The last control is a tone control.

I like it best straight in but it's great boosted with pedals as well. Here's a clip of me messing around with it last night straight in with my Les Paul. The amp is set with the volume up just under the halfway mark on the bright channel with the deep channel at about 4. It's running into my Mas110 which is set to load, line out through a delay and reverb pedal then into a MosValve power amp pushing a pair of 212 cabs.

 

Heady Jam Fan

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9,014
You should try a reverb pedal with separate effect and dry output jacks. Run the dry out to the main input you use on this amp, and the effect output to the clean/turntable input.
 

wrathfuldeity

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1,831
I have 3 mid century that I love
Bogen PH10 pp6v6 monoblock...for pedal platform
Bogen VP12 recordplayer with mic se6L6
Newcomb 1612 recordplayer with mic se el84
 
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701
Here is a Precision Electronics PA which I converted to an amp head. Its circuit has been significantly altered from original. These old PAs often have very good iron. Playing starts around 3:00.



 

LPVM

Member
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2,497
Here is a Precision Electronics PA which I converted to an amp head. Its circuit has been significantly altered from original. These old PAs often have very good iron. Playing starts around 3:00.
Normally I zone out when guys are giving the information in the beginning of the videos but your smooth radio guy delivery and the very detailed Soaring Tortoise Electronics Super Special Custom Amp Conversion Shop descriptions were fun and very entertaining. Thanks for posting! :D
 

swiveltung

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14,490
Bill Sundt (formerly of Soldano) modified this 1948 RCA--sounds beautiful.
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I had two of those. That one and the bigger one with 4 x 6V6. Man those old RCA's are very high quality stuff. Warm and fat, great for slide... would be good for a single instrument jazz player too I think. There is also a huge one that is maybe 2 ft long. One just sold on Ebay a week or so ago.
 

donfrantz

Yo! You stealin’ all the cool.
Gold Supporting Member
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1,374
Cool--it's a really fun amp--it is good for slide.
 

cal1024

Member
Messages
318
Messing around with my 1947 Masco MA25P last night.

It's a 25 watt tube PA, all loctal preamp: 2 x 7B4, 7N7 & 7F7. They are a bit unusual.



The power section currently has a pair of RCA 6L6GC black plates in it and the rectifier is a 5U4. It's 2 primary channels are set up with channel one voiced deep and channel two brighter with a bit more gain. They are internally linked so you turn up channel two for the level of crunch you want then bring up channel one to fill in the bottom. The turntable is disconnected but that channel works too but is very low gain. I put a jack in the back of the amp that is connected to that and have plugged an iPod into it and have played along with it but don't really use that for the most part. The last control is a tone control.

I like it best straight in but it's great boosted with pedals as well. Here's a clip of me messing around with it last night straight in with my Les Paul. The amp is set with the volume up just under the halfway mark on the bright channel with the deep channel at about 4. It's running into my Mas110 which is set to load, line out through a delay and reverb pedal then into a MosValve power amp pushing a pair of 212 cabs.

Sounds really good!
 

Sparky6string

Member
Messages
3,609
That does sound great, and your recording situation is sweet too (I can hear the room reverb well). I've come to the realization that my fave is also an old tube PA head- my Newcomb Pathfinder E-10b. I was just cranking mine through an Avatar 1x12 open back with a Celestion Gold, and I also had that sweet room reverb going on and it was addictive. These old things had a thickness to them that is hard to describe. I'm wondering if this is just my bag and I should buy a couple more.
 

LPVM

Member
Messages
2,497
I've come to the realization that my fave is also an old tube PA head- my Newcomb Pathfinder E-10b. These old things had a thickness to them that is hard to describe. I'm wondering if this is just my bag and I should buy a couple more.
I did that. The 2nd one is a '51 Stromberg Carlson and is a completely different animal; 6SJ7 pentode preamp, single ended 6L6 power section and a 5Y3 rectifier.

 
Messages
701
Normally I zone out when guys are giving the information in the beginning of the videos but your smooth radio guy delivery and the very detailed Soaring Tortoise Electronics Super Special Custom Amp Conversion Shop descriptions were fun and very entertaining. Thanks for posting! :D
Why thank you very much. You're welcome. (said in my very smoothest radio guy voice)
 

enorbet

Member
Messages
46
These old PAs often have very good iron. Playing starts around 3:00.
That's a lot of why they sound so good. I was jaw-dropping shocked to hear an ancient Altec Theater Amp (Power Triodes with almost 1000vdc on the plates and HUGE Xformers) blow away a 200 watt Hafler with a Direct-to-Disc Master Recording. For guitar, I replaced a blown Output Tranny on a Blackface Princeton Reverb with one from a Bell Laboratories reference amp and was similarly astounded. There is Nothin' like top notch iron.

On another front I absolutely swear by the Direct-Coupled Cathode Follower post Gain to drive the tone stack as it acts like an awesome simple Limiter causing "bandwidth squeeze" in the tone stack - extremely vocal and dynamically expressive when pushed hard.
 

wrathfuldeity

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Messages
1,831
home and posting pics of my fav...a little recordplayer/pa conversion...but usually run it with an oversized cab




 

sg~guy

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682
-HENRICSON???-

-he's a dude in Scandinavia who modes old tube PA's,... Very,very highly regarded, and about to launch a amp line.
 

Scottone

Member
Messages
1,525
I used to have an MA50 that I modded to have a tweed deluxe inspired pre-amp (but still using the loctal tubes). Sounded pretty damn good.
 

jimbo13

Member
Messages
463
I had Skip Simmons build me a Masco ma25 and it kills. I've owned and still own a ton of tweed, brown and bf amps and the Masco is on par if not better than most of them. Guys on a current thread here are discussing spending their retirement on brown Fenders. I've owned all of the ones they are busting a nut over and don't have the heart to tell them there are better ways to get those tones and then some with these old pa heads.
 




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