Well, what should I do with the T1RVT

[zulu]

At Last!

http://www.soundclick.com/bands/page_so ... ID=8701924

 

[capnjuan]

Hi Zac and congratulations on your amp, its tone, and your nicely-cooked blues/jazz licks. Did you have the reverb on too? Is that the kind of music for which you'd like to have a more emphatic tremolo? If I found some literature on it, how strong would your interest be in messing with it? Again, congratulations. 8) John

 

[zulu]

Thank you John, wouldn't be using this amp if it weren't for you.
Thanks for listening, too.
The reverb, yes that's all T1 'verb on the guitar, no effects in the mix. I love the reverb on this amp, aside from a bit of a pop when switched with the footswitch, it's so lush, I think I'll be over-using it for a while.

the tremolo, heres a pic of the new caps in the trem circuit, got these in a little bit neater.

This recording was done with the trem strength knob only about 30%, full strength is quite a bit more range. Adjusting the trem strength trim pot is crucial, just a hair too much and it thumps, back it off a hair and not much strength, but I've got it dialed in pretty darn good.

The amp does seem to run hot, after an hour or so the front panel is almost to hot to touch. I'll put a little fan behind it. Have you ever added a cooling fan to an amp circuit?

 

[capnjuan]

Hi Zac; I'm on it .. reply later this evening. J

 

[capnjuan]

Hi Zac; short of refreshing the several resistors in the circuit and as Leo Fender might have said; 'What you have is what you get'. If you're willing to make the effort, I'd suggest changing those resistors out and the two 3?0k trem/bias resistors shown on the standard T1 RVT schematic. I guess I'm saying all you can do is baseline what you have. The pic below is the tremolo oscillator 1/2 of V1 ... pins 1,2, and 3; the other half that's blocked out is the input preamp. That's a 220k / 1watt resistor highlighted.

You can reduce the value thus raise the voltage but that might mean that instead of 30% rotation for max without thump, you get 20% rotation for max without thump. Alternatively increasing that resistor to a higher value would produce less gain but might mean that now you spin to 50% but the tone quality isn't any better. Alternatively, you can replace V1 with a 12AT7 ... the mantra with stepping down is less gain = more headroom ... I mean a 12AT7 has a lower amplification factor ... about 60 v. 100 for a 12AX7 ... the result might be nothing more than you can turn your pot to 50% before thump ... or it might be that you get that rich, organic trem ... that is available on Gibson amps up to 1963 ... there really is nothing finer. Anyway; change out the rest of the passive parts and see what you have. And then maybe try a 12AT7 there I wish I had a good answer for you but I don't.

Make sure you have 0 resistance from the chassis side of that resistor to ground ... cap should be ok but check it anyway. John

 

[capnjuan]

Hi Zac; forgot to mention the heat ... so long as the power tubes aren't 'red-plating' ... glowing red hot ... the amp is running normally. Here's some ideas you might think about.

Backpanel: find a matching but longer screw for the backpanel; take the other three screws out and let the backpanel swing down and away.

Vents: a speaker grill adapted as a vent or top-mounted horizontal vents. Either of these present aesthetic issues or ... cut round 'ear-holes' at the top of the chassis sides and cover them with the kind of safety grill used for pc muffin fans .... ugly ... but ...

Fan: never back-fitted a fan ... they can be electrically and aurally noisy and they have issues: mounting orientation ... as an exhaust fan or a supply fan billowing air against the tube deck? And power: 110VAC off the in-coming power? 6.3VAC off the heater circuit? stepped down DC taken from the primary supply?

?? J

 

[zulu]

Hi cap thanks for the replies.
To clarify on the trem strength, I have full adjustment on the front panel, up to 100%, before thump. The recording of At Last above was using only about %30 of available trem strength. If you heard the full strength, you'd probably tell me it's fine, or

as Leo Fender might have said; 'What you have is what you get'.

Make sure you have 0 resistance from the chassis side of that resistor to ground ... cap should be ok but check it anyway.

Will check, thanks for thinkin' on it.

As far as the heat, I'll make sure the tubes are not red plating, otherwise I'm probably just being over protective. It's true what you said earlier about increasing my 'sense of ownership' in the amp

Backpanel: find a matching but longer screw for the backpanel; take the other three screws out and let the backpanel swing down and away.

Vents: a speaker grill adapted as a vent or top-mounted horizontal vents. Either of these present aesthetic issues or ... cut round 'ear-holes' at the top of the chassis sides and cover them with the kind of safety grill used for pc muffin fans .... ugly ... but ...

Fan: never back-fitted a fan ... they can be electrically and aurally noisy and they have issues: mounting orientation ... as an exhaust fan or a supply fan billowing air against the tube deck? And power: 110VAC off the in-coming power? 6.3VAC off the heater circuit? stepped down DC taken from the primary supply?

?? J

again, appreciate your brainstorming. Maybe there's a place on the underside of the chassis where it would be helpful to mount some sort of heat sink.

oh, and guess what?

The new tubes are here!!

the tubes are here the tubes are here yay yay the tubes are here!

I'm excited, in case you couldn't tell.
I now have 4 (four) sets of power tubes for the amp!
All different brands, too, for different flavor choices. Yum!
the RCAs that came in the amp, Valvos, Telefunkens, and mmmm...mm...mmm...mmMuuuullllards :!:
spare rectifiers, too.
Infinite thanks to Coastie for the thermionic valves, and also because some of his other posts played a part in inspiring me to DIY.

 

[zulu]

Hey capn here's some stronger tremolo and reverb.

http://www.soundclick.com/bands/page_so ... ID=8711290

disclaimer- these are not meant to be polished recordings, they are 'practice tapes'.

 

[capnjuan]

Hi Zac; well ... that's a good aerospace ( :wink: ) solution with the heatsinks; not exactly factory but it's a better solution that carving up the cabinet or scotch-taping a fan somewhere ... don't forget the compound. I have outted my affection for tweed Gibson amps here many times but with fresh caps, their trems can sound as organic as Neil Young's voice at the end of 'Old Man' at Alice Tully Hall ... like something's breathing ... the amp ... the guitar ... something. I listened to Gone Gone ... unless you want more, that sounds like plenty of trem and a very fine avatar you have there too.

The grounds of the cap and resistor; only mentioned because they look like they're going in different directions; if the amp is working well, they're probably ok ... it's just a visual thing. If you have fresh caps, a healthy speaker and (thanks to Coastie) world-class tubes, you have all that the amp can offer. Like most amps of the day, it does some things well and others not so well and without gutting it and building it back as a Deluxe or something, there aren't a lot of documented mods for it.

Ignoring for the moment all those fine 6GW8s that just walked in the door, it would take about 2 hours to move 4 of the 8 wires on the base of each 6GW8 and you could use 6BM8s. Doing so would warm the amp up some and it would probably break up more easily at lower volumes. But, having done so, you'd have a FrankenGuild and as Merrie put it: 'The closer we are to danger, the farther we are from harm' ... you might like it better and maybe one of your friends might fall in love with its tone but if you put it on eBay ... well ... it's a hard enough model to sell as it is.

Good luck; it's been fun and happy to help with the B-25 if you get interested in it. John

BTW: I have one of Coastie's scratch-built projects here that he lost interest in ... an EL84-driven Vibro Champ (I note I can't get him interested in any of my projects in which I've lost interest :evil: ................... :lol: ) ... he's full-in committed and his work is meticulous. j

 

[zulu]

Like most amps of the day, it does some things well and others not so well and without gutting it and building it back as a Deluxe or something, there aren't a lot of documented mods for it.

I am good with that. It's a clean amp, I like that, with that subliminal tube gravel. If I want more break up, I'll 'Ray Davies' some holes into the speakers :shock:

a very fine avatar you have there too

Thanks, I was going for something a little capnjuanesque

the 6BM8 mod sounds interesting, a rainy someday maybe.

I have outted my affection for FrankenB-25 tweed Gibson organic tremDeluxe amps here many times

I paraphrased your quote a bit, John, but tell me more about this idea!

BTW, I've caught myself looking at amp kits and scratch builds lately, my friend here at work is dying to make a hardwood dove-tail jointed cabinet for 'anything' with his new woodworking tools.

 

[capnjuan]

Well ... lots of people start with Champs ... single-ended tone machines ... fun to build and play ... from a kit or from scratch ... if they stay at it, the next stop is usually a Deluxe. As ever, the money is in the transformers ... the chassis, switches, and all the bits and pieces can be bought for the price of the transformers.

Messing with older amps has its limits; you can make them sound as good as their design and parts will allow like you've done .... but ... carve it up and the result which might sound good will be sold as near scrap and, arguably, violates the amp; i.e., if you wanted a twin reverb, you should have bought/built one in the first place.

You probably already know this site but the boyz on Hoffman Amps are the most active scratch and kit builders yucking it up on the web and where you can get very good help ... with a minimum of abuse :wink: Hoffman sells kits and so does Ted Weber who also sells his own transformers, caps, and of course the finest Jensen-style speakers. Time-consuming but rewarding.

Always a big fan of Ray's btw!

 

[zulu]

Thanks for the link John, I hadn't been there before. Lots to read.
The songs you heard, well I have to admit you were listening to my "stinky old speaker wire". Finally changed that last night. Replaced the bulgin connects with 1/4 phone plugs. I had been wondering where to find good speaker wire cut to length, then thought of the local independent car audio shop, where they sold me 6 feet of oxygen free 14 ga 'Stinger" wire for 5 bucks.
Haven't tried any of the new tubes yet. this weekend, hopefully.

Not sure what else to do with this amp, capn, but I'd like to get the thread up to 10 pages! Got any good recipes?

 

[capnjuan]

... Not sure what else to do with this amp, capn, but I'd like to get the thread up to 10 pages! Got any good recipes?

Yup; new speakers. I actually screened through this soon-to-be 10 page thread and didn't find pics/discussion of the subject but if they have 137XXX either on the magnet or the rim, then they are CTS/Chicago Telephone Supply and probably original. Some of the 12" have a plastic cover and square ceramic magnets underneath ... I think the original 8" speakers also had square magnets... like this:

Anyway, next to your fresh power caps, new speakers will provide the highest bang-to-buck impact on the voice of the amp. Whether it's an alnico or a ceramic magnet, modern speakers are much more efficient than older ones in converting signal to sound. Everybody feels differently; keeping the originals in the amp for the sake of its ampness or tugging them out, storing them safely, and trying to find out how good the amp can sound. Some techno break dancing from JuanzAmpz follows:

Alico v. ceramic; Coke v. Pepsi ... it's as simple/difficult as that. In the mid-'60s, the Department of Defense declared cobalt ... the 'co' in alnico to be a strategic resource - no one could buy or sell it except the government - and thereafter, the ceramic speaker rose to prominence. Although ceramic speakers had been around since the late '50s (I have a rareish '59 Jensen C12Q [leading 'P' in Jensenese means alnico magnet] in my GA20T), they didn't come into widespread use until the DoD edict and rise in popularity of higher and higher-powered guitar amplifiers.

It's worth saying that the physics differ in a material (no pun intended) respect; a ceramic-magneted speaker can be made to very high power-handling standards and alnicos can't. 50 watts is about the practical limit of power handling for alnico-magneted speakers; after that, the magnet must become exponentially larger as power handling goes up ... and 20-30 pound magnets ... well ....

Above 50 watts, there's no question about type but below ... now we're into the realm of if it's Tuesday, do .10s strings on a mahogany guitar sound better than .11s on a maple or is a tusq nut better on an addie- or spruce-topped guitar ... Among professional musicians who play at high power/volume and need efficiency, there is no alnico v. ceramic discussion; the answer is ceramic but .. at your fire-breathing +/- 12 watts and if you want fresh speakers, you have a choice to make.

These are broad generalizations ... alnico speakers have somewhat woolly bass especially in open-back cabs, thickish mids, lack a little articulation in the highs, and older/smaller alnico magnets get saturated faster and contribute to distortion ... ceramic speakers have tighter bass, are a little more uniform in low-to-high frequency response, and have more clarity in the highs although at the lower end of the price range, they tend to be ice-picky, sterile, and nasal. Aside from their warmth, alinicos are beloved for their big, fat, rounded mid-range that is characteristic of vintage/roots R&R and good ones (big magnets) have a cathedral-like chime that can't be duplicated in a ceramic speaker.

As far as mfrs go ... this is the Gouda / Swiss / Camembert part of the deal; my personal preference is Weber especially the vintage series. If you are closer to a jazzer than you are to a rocker, I think you'd want ceramic magnets and, in a Weber, that'd be a 12F125S ... and then there's the 8" ... any one of the 8F series would be fine ... of course you'd look good in brown wingtips too ... I mean speakers and their tone is a very subjective thing ... the only other suggestion is that if you can't put some real money into speakers ... wait until you can; they're that important.

 

[zulu]

ugh, just lost another long post. Sigh.

The speakers in there, capn, are :
8"
CTS 137446

12"
Pyle 1098243

 

[zulu]

I enjoyed reading your break dance, I bet it's awesome to see in person, with all the 'poppin' and 'lockin' and 'techie talkin'.
I can picture you doin back-to-head-spins in front of your EL34 powered boombox! "yo yo yo, al ni co"

:lol:

If I could try a blind test and pick out some new speakers, I have no clue what I would choose.

But if I buy a new set of Weber ceramics, (when maybe I would have picked Jensen alnicos had I been able to try them)

Will I still like the new better than what's in there now?

Or did I just ak an impossible question?

 

[Default]

I would guess that the 8" Pyle might be for home consumption? Pyle did make guitar speakers back in the Eighties, my first speaker swap was into a ss Yamaha 2x12 amp.
IIRC, they were high wattage, high efficiency speakers, which coupled to a truly nasty amp and lack of skill, made me the most hated person for a 6 block radius.

 

[capnjuan]

Me at the local 60-and-over competition ...

The easier question first ... new v. old; the only thing guaranteed is that irrespective of type, the amp will sound different; more forward, more detailed, a bigger 'sound stage' as the O'philes would put it, more alive ... these characteristics aren't tone-specific ... they're the effects of a fresh magnet and tighter cone. On the dark side, whatever limitations are inherent in the amp's circuit will be more obvious ... no more hiding behind a limp-as-a-paper-towel cone. Nevertheless and including the effects of self-fulfilling expectations, most people would say the amp sounds 'better'.

Sidebar: whoever was in your amp before used quick-disconnects on the 12" speaker lugs ... approved by Juanzampz.

Down-headed riff: alnico speakers were common in the olden days in part because of the power limitations in 5-25 watt / twin 6V6-6L6 amps ... within the physical and economic range of alnico speakers. Until the early 60s, Jensen alnicos were the kings of commercial tone hill particularly the Jensen Alnico 5 setting aside Fanes, Rolas, Celestions, and Klangfilms that weren't commercially available (cheap enough) for mass use. Thereafter both Fender and Gibson fell out with Jensen; Fender going to Utah and Gibson to CTS who made the especially forgettable ceramic 'Ultrasonic' speakers found in mid-60s Gibsons. So ... you could argue an historic/sonic link between amps designed in the 50s and alnico speakers; that is, for informal play and if that's the sound you want, you pretty much have to have an alnico speaker ... with all of its warts and flaws.

The T1 RVT was built during Guild's 'middling' years; after its knee-high, Ampegish, rear-facing controls era but before the Avnet-era of serious designs intended to compete in the market with Fender and Ampeg. Although the 6BM8 was in production and used for reverb in the T1, Guild self-consciously chosen the drier, cooler 6GW8 with its sharper cut-off properties (less distortion) for output tubes and hung those whopper treble-snuffing, distortion-damping .15uf output coupling caps on it. If you're keeping score that's 7 times larger in uf than early Fender/Gibson ... and further recalling that increased cap value acts like a low pass filter. The tone is still more Ampeg than Gibson ... it's a clean machine breaking up only at high volume.

So ... the question is; do you enhance the intended design properties of the as-sold amp with a ceramic speaker (bearing in mind that there was no other commercial option at the time ... that is, they might have chosen alnico had it been in the market) or do you try and tip the electronics/tone away from 'original' and put an alnico speaker in it. I suggested the Weber ceramic mostly because I thought it more consistent with the amp's design and as a nod towards your highly expressive cerebral jazzish play.

If you want an alnico speaker, buy a Weber; a company that has made its name 'forging' the signature tone of original Jensen speakers - nobody does it better. The new Jensen speakers ... in a word ... no. Like I said, if I couldn't afford a top-notch Weber, I'd wait until I could. All that said, you might PM default who posted above; I know he used to have a pair of vintage re-coned Jensen P12Rs ... do not know if he still has them but there's some chance he might let one go for less than a Weber or in the range of a new Jensen. That would be a way to get a taste of alnico with going too far out of pocket. As far as the 8" goes, if your amp is wired like the schematic (and there's some chance it isn't) ... unlike most amps that turn reverb off by just grounding the can output, the T1 uses the reverb amp for dry signal sound reinforcement when the reverb is switched off.

The amp taps the line just ahead of the phase inverter and feeds a dry signal to a switch; the other switch input is the reverbed signal from the 12" speaker / can / 12AX7; that circuit is 'always on'. The switch's output feeds the 6BM8's driver side and then the power out half of the 6BM8/OT/8" speaker. So ... that speaker is always working ... either handling a dry signal in parallel with the 12" speaker or handling just reverb and I think as between alnico and ceramic I think this is a pick em' thing; I don't know whether you'd get a noticeable difference between the two types but I'd say that whatever you choose for a 12", get the other type for the 8" reverb. I had a Gibson GA30 with a Jensen P12N and a Celestion G8L (ceramic) that default laid on me ... couldn't have been happier with the combination ... of course ... that's according to my tone preferences.

As a final note; I have that C12Q/ceramic in my GA20T because I've fooled with the circuit to get it to break up early. To tame some of the wildness, I put a ceramic speaker in partly because I got a good price on it and partly so the magnet would be less prone to saturation and thereby not contribute any further to the amp's already moderately-distorted output but my rock and roll fantasy is rhythm-playing (Stoly-sipping) front-man ... so ... your music may vary ... :wink:

 

[zulu]

wow, thanks John, nice moves.

The easier question first ... new v. old; the only thing guaranteed is that irrespective of type, the amp will sound different; more forward, more detailed, a bigger 'sound stage' as the O'philes would put it, more alive ... these characteristics aren't tone-specific ... they're the effects of a fresh magnet and tighter cone. On the dark side, whatever limitations are inherent in the amp's circuit will be more obvious ... no more hiding behind a limp-as-a-paper-towel cone. Nevertheless and including the effects of self-fulfilling expectations, most people would say the amp sounds 'better'.

excellent answer. Let the speaker GAS begin!

Sidebar: whoever was in your amp before used quick-disconnects on the 12" speaker lugs ... approved by Juanzampz.

Glad to hear it, as these are the new wires in Zaczamp:

 

[zulu]

if your amp is wired like the schematic... the T1 uses the reverb amp for dry signal sound reinforcement when the reverb is switched off

Yes I can confirm the 8" speaker has an (almost) dry signal when the reverb's switched off.

I'd say that whatever you choose for a 12", get the other type for the 8" reverb.

8)

With the general design of the circuit being more on the clean side, I agree it makes sense to go with speakers that will stay clean longer.

I suggested the Weber ceramic mostly because I thought it more consistent with the amp's design and as a nod towards your highly expressive cerebral jazzish play

Don't know if I've had a nicer compliment, certainly not in the form of a speaker suggestion. Thanks man!

 

[zulu]

I would guess that the 8" Pyle might be for home consumption? Pyle did make guitar speakers back in the Eighties, my first speaker swap was into a ss Yamaha 2x12 amp.
IIRC, they were high wattage, high efficiency speakers, which coupled to a truly nasty amp and lack of skill, made me the most hated person for a 6 block radius.

:lol:
one of those amps where the best listening position is directly facing the amp, at a distance of one mile.

btw the 8" is the CTS, the 12" is the Pyle.

Glad you popped in Default!