Friday, June 26, 2015

Rare Polytone 102

Ok, yeah I'm a tube amp guy but occasionally I come across an old Polytone that I say yes to. I'm not gonna lie to you, I'm not the first guy anyone should take their solid state amp to and 99.9% of solid state amps out there I will simply say 'no' to. Plus it's worthy of my ugly amplifier photo pile!

However these are just really well made amps with a simple enough circuit. Still a pain to get around in but not like a Line 6 or some other digital horror show.

The nice thing about these old Polytone amps is the power supply/amplifier is separate from the preamp. You can just pull the thing out and work it from there.

A few connectors and it pops right out. The worst thing about these Polytone amps is they are filled with fiberglass insulation for vibration dampening:

Digging out the power amp feels like laying insulation in the attic with my dad in the 70's. Remember Carter and the drive to make our homes more energy efficient? Good thing. Fiberglass feels icky on the fingers!

These amps have a fun preamp. They have the strangest tremolo in the history of tremolos. They can go below 40BPM. Not particularly useful unless you have some hipster noise project. I like it. What were they thinking back in the 70's?

This amp boast a single 15" speaker and 2x8" speakers wired through a crossover cap. Interesting design. Big, clean 120 watts of jazz here. And yes, they were designed with the jazz player in mind though I discourage plugging a chorus pedal into one just cause, well, these sound pretty great and like I heard in a music store once: (Jazz player) "Hey man, what's a good chorus pedal here?" (Sax player under his breath) "The broken one".

The owner of this fine beast also owns the Magnatone 2x12 on this page. He uses them together, not loud, but just for a big sound. That's an excellent combo.

So what was the problem with this amp? It had a few issues. Like I said I'm not the best with these solid state amps but I'm persistent. It hummed like a power station and didn't pass audio. First thought was filter caps. Changed them and hum went away but no audio still. About 5 minutes into that 'pssssst!' and the LM391 driver I.C. caught on fire. Had to order one and replace the socket too. Did that and voila, audio. Really, really terrible audio, but audio nonetheless. Checked the power supply, fixed a ground issue but still really poor audio. Logic tells me one side of the power amp isn't working. Sounds a lot like a push pull tube amp with one tube out, common problem with Fender Blues and Hot Rod Deville/ Deluxe amps (resistor failure!). So I pull the power amp again and inspect and my gut was right. One of the driver transistors had 2 broken legs from a previous repair. They were soldered but poorly soldered and came undone. Re-soldered and now it's loud and clean.

Best thing about a project like this is if I see another one soon I'll know what to do better next time. Plus I needed to order parts for this and now I have spares. This was a fun project. I'd work on another one!

I should add that I used to own a single 12" Polytone amp years ago. One of the best upright bass amps I've ever played. Nothing sounded quite right for that instrument in the mix, and it could throw the sound out there and spread it around nicely. My bassist likes to use the bow, long tones. This would heat that amp up quite a bit so twice in about 5 years I needed to re-solder the .3 ohm 10 watt resistors back in place! 2nd time I found a permanent solution but can't quite remember what that was now!


Thursday, June 18, 2015

Telefunken D9A microphone

Not all Telefunken microphones are created equal. This one is about as cheap as they get. It's no U-47 but, I'm a fan of old cheap mics and truthfully, this one doesn't sound half bad. Job was to make it useful, get rid of the old German 3 pin connector and install a proper Neutrik XLR. Nice and easy. I'd use it myself. Crappy mics make my singing sound better!


50's Maestro Viscount. Mmmmm.....

Here is a Gibson produced amp made during the 50's. It's the same amp as a Gibson Explorer amp I once had.

Yeah, these are my favorite Gibson amps. I don't like their product from the 60's but these babies rival the tweed Fenders and can be had much cheaper if your stars are aligned. They aren't as well made of course but, so what? I used to gig with mine. Never gave me trouble. These have a wonderful tremolo as well and produce about 12 watts going into a single gold Jensen 10" speaker. It's a bit like an old Fender tweed Vibrolux with that 10" speaker. Makes me wonder who was spying on who?

What makes these amps cooler to me is these are cathode biased rather than grid biased. I like the compression I get out of these better though the Vibrolux ain't no joke!

This amp was 100% original. Tubes, footswitch, owners manual, cover. A beauty. It hummed terribly so now it's 90% original. The old filter stick (looks like a stick of dynamite!) dried up. Can't use an amp like that! Sorry collectors, my customer is a really fine player and gentleman from Baltimore. He needs to cut some tracks!

My customer is one lucky guy with great taste too!


1940's-50's Epiphone Zephyr. Oh, my, lawd this thing is awesome!

This was a fun project. I've only seen one before and it was destroyed, painted red and not worth the effort so I sold it. Now I wonder....

An absolutely beautiful amplifier. Very powerful voice and no I don't mean that in the volume way. It's not a rocker. It's like a Gibson Charlie Christian amp but just, fatter sounding. Even at low volume all of my notes are just round. If you buy one you don't want to go on blasting it. this amp is over 60 and has a special Rola field coil speaker. It's in great shape. If you blow that, you will never get a sound that is the same as this. How do I know an amp is really good? I test my amps with my trusty Esquire. One bridge pickup only. If there is a ton of low end then, I'm not craving another pickup. This amp has a lot of low end but isn't 'dark' sounding. It's just even. I'm a big fan of Epiphone guitars in general, and to me they outshine many Gibsons costing much more. This amp is no exception. Great tremolo too!

This amp sounded pretty good to me, customer said he played it and the more he played the quieter it got. It didn't hum but all the electrolytic caps were original. This was the problem! And another tech got in there and replaced all the signal caps with decent foil caps but none of the electrolytics. I think he was just lazy. They are a pain to get to! Most of them are on the opposite side of the tag board:

The main filter can, a dual 40uf 450 volt type I drilled the rivets out from the top and replaced with one of those ones you see in English amps:

I just used a couple of sheet metal screws to hold it in place. That's part of the fun of this job. I would not want to take the whole amp apart to get to this. Best to get creative and not suffer!

One of the coolest things about this amp is how modular it is. There are 4 connectors on it, a 4 pin, couple 5 pins and a 6 pin. They connect the speaker, preamp and choke network. These are designed with the service guy in mind.

I'm also a sucker for octal preamp tubes. This amp uses my favorites: the 6SJ7 pentode and the 6SN7 dual triode. It also uses a couple 6SN7 tubes for the tremolo circuit. You could build one with EF86 tubes and 12AU7 tubes but why? There are so many good NOS octal tubes around and the more modern miniatures are pricey. My favorite amp I built used 6SJ7 tubed going into a pair of 5881. Similar vibe to this amp and I don't worry about blasting it.

I also changed a bunch of load resistors, this reduced some crackly stuff. But overall once the electrolytic caps were changed the amp came alive. One to envy. Oh if I had a studio.....

The ultra simple control panel:

You were meant to sit behind this amp and either use a footswitch for the tremolo or the toggle switch on or off. Super cool. As a sax player I'm always on the wrong side of the horn to hear myself. This has the same concept. Suffer guitar players!!!!

And check it out. Even has the original cover! Amp had some water damage a long time ago that warped a wood panel on the bottom. I don't do woodwork myself but whatevs! It's making music now!

Here is the great Django Reinhardt playing through one. This amp was found in New Jersey, pic was taken in New York. Hmmmmm, just maybe I can fantasize this is the amp? Sure, why not!


Musicman HD-130 2X12 Combo

Here is an ugly one! A Musicman HD-130 head shoved into a Fender Super Twin cabinet with the original all too heavy Super Twin speakers! Easy repair: blown tube. Change it and re-bias. Customer had 3 original Sylvania 6CA7 tubes that were well used and....they tested great and still worked. This was a 'keep it cheap' repair so I put 2 of those in and left 2 of the Electro Harmonix ones in there. They actually were very close to matching. Anyway, amp is making music again! This is one with the solid state phase inverter. Biasing is easy but do not attempt this if you have no experience. These babies contain a lethal 700 volts DC. Stay out of that kitchen and let a pro take care of you.

Other work: I did clean up the cabinet. Re-glued the tolex etc. I get a little OCD about that. Lipstick on a pig? Sure. But the best rock n roll ain't pretty! I love me an ugly amp!


'59 Bassman Reissue

One of the most sought after amplifiers in the world is the Fender tweed Bassman produced from about 1958-1960. There is a good reason for that. It really is a Swiss Army Knife that can handle just about any gig with the exception of metal, but even Eddie Van Halen enjoyed one of these. Trouble is to find an original you need a bankroll like fast Eddie, they can command prices upwards of $10K in great condition. I remember the first one I ever tried, that was at Mr C's Music in Marlboro, Massachusetts. My dear friend Shawn Clement's pop owned it (remember mom and pop music stores?). It was an ugly example and this would be in 1986. The tweed was removed and the pine box had a walnut stain to it. This was the days before people started re-tweeding, relic weirdness etc. You simply played the things and made them better looking in your eyes. I thought is was really cool looking actually and when I played it, though it had no 'overdrive' channel or reverb, the sound I could produce with my 18 year old fingers got me curious about old amps. It was around the next year (1987) that I went to the NAMM show with the Clement family and Fender introduced the '59 Bassman Re-issue. I'm a lifelong Fender fanatic so this totally caught my eye.

Todays example is one from right around that era. It has the blue Eminence speakers rather than the trashy sounding Jensen Re-issues. True story, I had a totally stock Re-issue Bassman from this era and a Victoria version (all hand wired, very nice amp!) that had my least favorite caps and speakers, the Jensens and those 715P orange drops. I had a bunch of my customers play them and they all preferred the re-issue. When I told them it was just an $800 stock re-issue amp, none of my customers believed me. So yeah, these are really good amps.

This particular one was making no sound at all. Dead. That part of the problem was easy to solve: one of the speakers, which are wired in parallel had shorted out. Zero ohms. Unusual. In 25 years I have maybe seen this once, and that could be my memory inventing stories. So I replaced it with an Eminence alnico. Same great speaker as far as I can tell, and I'm a fan of Eminence speakers in general.

Control panel. Yes, those of you who know amps already know this. This is the amp Jim Marshall copied when he made the even prettier Marshall amplifier. Circuit is nearly identical, layout is nearly the same and they are both lovely amps. Those of you who may find that morally objectionable, nothing is original. Fender merely copied old Western Electric and RCA circuits and elaborated on them. That is the fun of tube amps. Copy then experiment!

This amp was also modded, or, hand-wired. Not the tidiest job but still well done:

I've done these before. I prefer to go the old fiberboard route. More room for cooler capacitors. Curiously these are the same caps that Fender uses in there modern amps. Why go to all the trouble if you're not going to do something different. Still, this is an improvement and the person who owns it is selling it. The next buyer is getting something that would sell for a lot more if it were 'boutique'.

This part I didn't like:

Very well done but no cover for the filter caps. Not that anyone will be reaching up there during a gig while it's on but, man, this is dangerous. Also the 2 main filters are 220@350v in series giving you 110uf. With a tube rectifier you really don't want to go above 50. It can cause a drain on that tube and on the 5V filament winding. Or at least this is what the old RCA manuals say and I trust them.

Using such a large filter in your first stage gives you the benefit of improved low end and overall more headroom, plus it's quiet. However, most folks like a little sag and compression. I changed them to 100uf each giving me 50 total. Hum? Nope. Very quiet.

Also had one noisy preamp tube and after a cleaning and tightening every bolt (many were really loose! Output transformer was barely hanging on!) then it was a wrap! Great sounding amp. If I ever decided to go big againit would either be one of these or a Vox AC30 or a Marshall Bluesbreaker. Either re-issue amps so I can actually play them live without worry or I'll build one myself. I had the honor of re-building Jimmy Vivino's Bassman Re-issue years ago and I heard it became a favorite of his. Allegedly Slash rocked it and fell in love too. That amp I simply took out some funky mods and re-tubed it. These are great amps. If you can find an early one like this even better. If you can pay me or someone else you trust to hand wire it then you have something that is really just as good as a $10,000 original! Why pay more?


Monday, June 1, 2015

Magnatone Custom 260

Nice easy job today. Speakers were blown. Customer had the originals which are in good shape. Also took out a mod someone did a while back that I didn't like. Caused the amp to run too hot, class A land. This amp has a beautiful pair of Marconi 6L6 tubes in it so I'd rather keep those healthy for a longer time. Didn't sacrifice any tone really, these amps sound so damned beautiful as they are.....

Output transformer was replaced a long time ago as well but what is in there is fine.

I really like copper Jensens that this amp came with. Copper is one of my favorite colors. I want this color in all of my amps! Matches my copper Esquire.

Magnatone was a class act. Listen to some earlier Bo Diddley recordings like this one:

Yup. That's a sound right there.....