Pauly22
24 posts
Sep 06, 2013
10:57 AM
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Guys, I need your advice.
I have a 1976 Fender Silver Face Princeton Reverb. Very good condition, and...very clean sounding. I like a dirtier sound. I've made the appropriate tube swaps, with marginal difference. I'm learning tongue blocking, which is helping a great deal, but I just don't know if this amp will ever be the crunchy old shoe I'd like it to be.
I tested some vintage amps today in a great shop I found, and there's definitely one there that has the sound I'm seeking.
I don't have the cash laying around to just go and buy the vintage amp.
Do I trade in the Princeton for the vintage amp; or do I keep the Princeton, save my money, and buy the vintage amp later.
Thank you. This is therapy for me.
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Kingley
3104 posts
Sep 06, 2013
11:08 AM
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I agree with Silvertone. Assuming that the amp is working properly and you're using a good Hi-Z mic. If you can't get a dirty sound out of a Princeton it's definitely your technique that's the problem.
Last Edited by Kingley on Sep 06, 2013 11:30 AM
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timeistight
1349 posts
Sep 06, 2013
11:26 AM
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What is the amp who's sound you like?
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LSC
498 posts
Sep 06, 2013
11:52 AM
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I would also ask what amp is the one you're considering?
From personal experience of buying and trading many amps over the years there are few I regret selling and of those regrets none was an amp I wasn't happy with at the time and later thought, "Oh no! It was me. I should have kept it."
A SF Princeton is a fairly cool harp amp, no doubt, but hardly the best thing ever. I had a '63 Vibroverb RI that was pretty damn good for harp after tube and speaker swaps but nothing like as good as the Gibson GA-6 Lancer I bought later let alone either of the Sonny Jr amps I bought. If you can't afford to keep and buy the one you like, dump it but try not to loose money. Then grab the one you like, operative phrase "the one YOU like."
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LSC
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timeistight
1350 posts
Sep 06, 2013
12:17 PM
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A low powered, vintage amp may sound fantastic in a shop, but may not be able to compete with a band as well as your Princeton.
If you trade in the Princeton now and decide to replace it later, it'll probably cost you $1,000. If the new amp is worth more than that, then it's a good deal; if it isn't, you're losing money.
Maybe you don't care. Maybe you'll never miss the Princeton. Maybe you love the new amp so much you'll do anything to get it. That's up to you.
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Pauly22
25 posts
Sep 06, 2013
1:17 PM
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I looked at the following:
1959 Custom Designed Suitcase Amp
1962 Danelectro Corporal Model 132
1963 Gibson Gibsonette
1966 Kay Model 720 Bass Amp
1964 Kay Model 703
1955 Valco Bronson Electric Sound Amplifier
I will say that ALL were more pleasing to me than my Princeton. That said, I'm probably in the market for a smaller practice/studio amp more so than a larger high powered stage amp. I can mic the small amp on stage. I sing as well and wear and in-ear monitor, so I get the harp in the earpiece so that I can hear myself play.
Notwithstanding the question of trading the Princeton, I'm pretty sure I'm looking for a smaller amp now, for tone, and will save for an ADDITIONAL larger amp later, for stage. At that time, I'll be rich and will buy a Sonny Jr. or Mega tone.
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6SN7
361 posts
Sep 06, 2013
1:27 PM
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It sounds like you have made up your own mind regarding the SF Princeton. Personally, I have never been crazy about the SF or BF Princetons as others are. Sell or trade it, go for it, and buy one of the small amps.
Go with your gut.
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Pauly22
26 posts
Sep 06, 2013
1:52 PM
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Yes, 6SN7, I hear you. And I admit, I posted hoping for validation of what my gut is telling me.
It's more a question of whether one gets rid of good equipment, even if it doesn't have the particular sound we'd like it to have.
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Rick Davis
2318 posts
Sep 06, 2013
2:00 PM
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I have owned many amps, and like LSC there are some I regret selling. I think you might regret selling the SF Princeton. If I were you at this point I'd keep it. A 12-watt 2x6V6 amp has a nice unique tone that can be suitable for both recording and gigging. I've heard 70's Princetons with a nice snarl. How long have you had the amp?
(I recently sold two nice small 5-watt amps. If I still had them I'd be offering you a trade for that Princeton.)
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-Little Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
Tip Jar
Last Edited by Rick Davis on Sep 06, 2013 2:02 PM
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harpwrench
673 posts
Sep 06, 2013
2:17 PM
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How hot is your mic? Personally I've never liked the 12au7 fad/swap. Combine that with a weak mic and it's worse. JMHO and no flaming here will change my mind so please don't.. Check out the lone wolf harp octave pedal, it will change your amped sound towards what you're after, and can boost a weak mic if that's the case, all for $150.
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Custom Harmonicas
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harpwrench
674 posts
Sep 06, 2013
2:21 PM
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Also your amp is around 40 years old, has it had a cap job in the last decade? This captcha thing sucks!
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Custom Harmonicas
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Barley Nectar
15 posts
Sep 06, 2013
5:15 PM
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I am with harpwrench on this. I have a SF PR w/ pull to boost. I am not a fan of low gain tubes as seems to be the harp craze. 5751 is about as low as I go. Low gain translates to Clean! A good tune up, speaker swap, and a couple of mods will make a PR a kick butt harp amp IMO. The volume difference between a 6 and 12 W amp is imperceveable. Also, the other vintage amps probably all need work too. Everything i find does. Keep the PR...BN
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Rick Davis
2322 posts
Sep 06, 2013
5:18 PM
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I agree with Mr. Nectar and harpwrench -- The 12AU7 sucks too much life out of small amps that are designed for the 12AX7. The 5751 is the way to go.
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-Little Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
Tip Jar
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Greg Heumann
2347 posts
Sep 06, 2013
5:39 PM
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I also agree - when an amp has a single tube-stage preamp, a 12AU7 is too low - 5751 is usually a great choice. When an amp has a 3-tube preamp section like the bigger Fenders - then 12AU is NOT too low in V2 and V3 - but I then like a 12AX7 in V1.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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1847
1052 posts
Sep 06, 2013
6:36 PM
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is'nt it V1 V2 then the phase inverter?
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master po
i get a lot of request when i play my harmonica
"but i play it anyway"
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SuperBee
1410 posts
Sep 06, 2013
7:11 PM
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I would never sell my 78 SFPR if I didn't have to. I run original tube complement, but changed to a weber 10A125-O, and that was a big improvement on original speaker.
Hard to believe you find it too clean. Too bright I could believe.
And a great guitar amp to boot! Bias makes a difference too.
I guess they are all a bit different, but I'd take it off your hands in a flash...even my metal guitarist friends enjoy playing through my SFPR. "Ballsy little amp, Hally"
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1847
1053 posts
Sep 06, 2013
7:53 PM
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harpwrench.. the captcha can be outwitted
if you have a thumb and a forefinger
simply hold down the control key
then press A
then hold the control key..then press C
you have now saved your post
now when the captcha gets you
simply click on where you would type
and hit control V
it takes maybe 3 seconds once you get used to it
'
us old folks didn't have computers growing up
we had harmonicas dag nabbit!
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master po
i get a lot of request when i play my harmonica
"but i play it anyway"
Last Edited by 1847 on Sep 06, 2013 7:54 PM
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Barley Nectar
16 posts
Sep 06, 2013
9:20 PM
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What the heck is a captcha???
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Kingley
3108 posts
Sep 07, 2013
12:37 AM
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If you have a good cupping technique and and simply just use a 12AY7 in V1. You should get a good sound from a Princeton. Only other things are keep the bass up high and the treble rolled off. Personally I also never used the reverb on the Princeton either. Here's a video of a Silverface Princeton and gives an idea what it should sound like.
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arnenym
195 posts
Sep 07, 2013
1:10 AM
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Have you tried a Harp Octave pedal?
It will give you better deep and dirt.
Last Edited by arnenym on Sep 07, 2013 1:13 AM
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Kingley
3110 posts
Sep 07, 2013
1:29 AM
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Personally I'd suggest that you don't throw money into buying gizmos to make your amp sound "better". Throwing money at something is never usually the answer. Firstly I'd look at your playing and mic techniques. Be brutally honest and ask yourself can you get anywhere near the sound you seek acoustically? If you can't then your playing technique needs work. If the answer to that question is yes, then look at your cupping technique. Do you have a good seal on the mic? Then look at your amps valves. Try putting in the stock valve compliment first and see how it sounds. Then try 12AY7 or 5751 in V1 and see how it sounds. Record all of the above and listen back to it with a critical ear, so your not getting a false sense of things. If the answers to playing and mic technique are yes and the valve swaps still don't work, then there's most likely something wrong with the amps circuitry and you need a tech to look at it.
If you're not comfortable with judging these things for yourself, just upload a video or audio file of you playing through the amp and we'll tell you what the most likely problem areas are.
Last Edited by Kingley on Sep 07, 2013 1:30 AM
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SuperBee
1412 posts
Sep 07, 2013
1:41 AM
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It could be the amp. Mine runs original valve complement and plugging in to input 1 with a pretty hot CR I get pretty nice breakup and good volume just shy of 3 on the volume. Like Kingley I steer clear of the reverb. The amp was rather bright before I changed the speaker, but I liked it as a practice amp because it rewarded attention to technique. With the Weber speaker I just like it. Max bass, min treble.
I reckon I'd get it serviced and check the bias. But maybe you've already been there? Did you mention something about low output tubes?
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harpwrench
675 posts
Sep 07, 2013
4:53 AM
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Kingley have you ever tried the Harp Octave? I'm not a pedal guy, but this one is a good piece.
Regardless of how good your acoustic tone is, if the mic is weak the amped tone is not going to be like a strong mic (unless boosted with another device). Or if the amp needs caps, speaker coil is rubbing, etc.
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The best you know is usually only as good as the best you've had.
Custom Harmonicas
Last Edited by harpwrench on Sep 07, 2013 5:01 AM
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Kingley
3112 posts
Sep 07, 2013
5:02 AM
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Harpwrench - No I haven't tried it Joe. I know Randy makes great pedals and I've used his Harp Attack and Harp Delay and both are excellent. I've no doubt the Harp Octave is in the same league.
I just think it's important to rule out some basic possible problems first when trying to diagnose amp issues, before looking into adding more gear to solve the problem.
Last Edited by Kingley on Sep 07, 2013 5:08 AM
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harpwrench
676 posts
Sep 07, 2013
5:29 AM
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I agree totally! Without being there we don't even know if there is a problem, it may just be the push-pull vs. single end sound.
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Custom Harmonicas
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6SN7
362 posts
Sep 07, 2013
5:57 AM
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You know Pauly22, Harpwench has a pretty good suggestion regarding a cap job. My guitar player had a issues with his SF amps for years, always complaining but he never took them in to be serviced. When he finally did it, one had extensive issues and the other it was a bad tube and a bad socket. One cost a bit to fix (200$) the other, 50$. . As I said, go with your gut, but if you are playing with a faulty amp, fix it.
Last Edited by 6SN7 on Sep 07, 2013 6:53 AM
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Pauly22
27 posts
Sep 07, 2013
6:30 AM
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Guys, once again, my gratitude overflows for all the great advice and the time everyone takes to post.
Some answers and a few more questions:
.I'm using a great mic, made by Greg Heumann, with a vintage CM element, so I think I've got that covered.
.My cupping technique is no doubt a work in progress. That said, while I'm on that journey, it would be nice to hear what I'm after every now and again to keep the motivation factor going.
.I'd be satisfied if my sound was like that in the Harpsucker video that Kingley posted. Toward that end, I will bring it in to a tech before trading it in, and likely get a cap job. Also to check the bias. This seems like an inexpensive interim step. I want to make sure the PR sounds like it should before I put it out to pasture.
.I've found two great techs in NYC thanks to your responses. Thank you.
Question - If your looking at the back of the amp, where is V1? I've already bought two 12AU7's and can put them anywhere within the four preamp slots, I believe. Where do you guys recommend I put them to drop feedback the most and increase distortion, if these tubes are capable of doing that?
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Kingley
3113 posts
Sep 07, 2013
6:42 AM
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Ok first things first. There are only two preamp valves not four. The two on the left (looking from the back of the amp) are if my memory serves me correctly the phase inverter and the reverb driver valves. You only need to change the V1 preamp. The V1 is the first valve on the right when you look at the amp from the back. Using 12AU7 valves will just kill the sound of the amp and make it sound flat and dull. Try leaving all the valves as stock and then changing V1 to a 12AY7 or 5751. That will make the amp sound much livelier, retaining it's ability to overdrive easily. Whilst allowing you to get the volume control higher before feedback.
Once you've changed that valve over the sound should get better. After that it's down to playing and mic technique which as you rightly state is a work in progress. Getting the amp checked over by a good amp tech is always a good idea, as they can do some other things to improve the amp even more for harp.
Last Edited by Kingley on Sep 07, 2013 6:44 AM
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SuperBee
1413 posts
Sep 07, 2013
7:08 AM
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If you are looking in the back, V1 is furthest right. It's originally a 7025, which is basically a hi-spec 12ax7. V4 is the phase inverter iirc. A tube swap might address the feedback issue, but I don't think it will solve the cleanliness issue. And personally, I think 12 au7 is going too far...of course, try it...but I expect you'll just think it sounds wussy
Is it possible the amp has been modified? It's a guitar amp, and guitarists can do weird stuff, like seek more clean headroom from a small amp so they can play louder...
When an amp is this old, all sorts of things could be going on.
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Greg Heumann
2350 posts
Sep 07, 2013
7:42 AM
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I would change the phase inverter to a 12AU. If it is still too feedbacky, change V1 to a 5751. You can google " tube layout" and get the answer to your question.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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Pauly22
28 posts
Sep 07, 2013
8:34 AM
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Thanks guys. I actually just put the 12AU7 in the V1 slot, and the 12AX7 back in the V4 (inverter) slot. I see an improvement. Got from 3 on the volume to 4.5 before I got feedback (with the mic fully open), and heard a bit more tone and crunch. Was then able to back the mic down to half power and turn the amp up to 8 without feedback. Even more crunch and tone.
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Barley Nectar
17 posts
Sep 07, 2013
9:03 AM
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Feedback is a function of amp volume at the mic. To lessen feedback, don't stand in front of the amp, stand beside it. Play in a soft room, carpet, curtians, upholstryed furniture with a bunch of people standing and listening. The best place is outside, if you live in the country. Don't pay any attention to where the volume knob is. It doesn't matter. When you put in a lower gain tube, that is the same as turning the volume knob down. The 12au7 will send LESS signal to the power tubes and REDUCE power tube destortion. The best place to put that 12AU7, is in a drawer, for that amp. This all is a steep learning curve. I went thru the same problems when I started playing amplified. My first amp was/is a Deluxe Reverb. The internet was not available then so I called, Fender, Shure and EV and talked to there engineers. You have a great amp. Give yourself time to learn, and keep it...BN
Last Edited by Barley Nectar on Sep 07, 2013 9:05 AM
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timeistight
1354 posts
Sep 07, 2013
10:02 AM
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"The best place to put that 12AU7, is in a drawer, for that amp."
But which drawer gives the best blues tone, BN? What drawer did Walter use?
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Greg Heumann
2352 posts
Sep 07, 2013
11:07 AM
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@Barley:
"Don't pay any attention to where the volume knob is. It doesn't matter"
Sorry to disagree with you, but your statement is simply not true. There is a BIG difference between gain and volume. If your amp feeds back with the volume knob at 2, it has way too much gain and is very hard to play well.
I have learned this through years of experience. It is real, I can prove it and I can demonstrate it. (And I have a lot of very happy campers who have taken my advice and said so.) I use this analogy all the time, but its the best one I've got so here it goes again. (Excerpted from my "All About Harmonica Microphones, and then some..." doc which you can download here.)
"Imagine if you had a 2000 pound sports car with a 500 HP motor, but the gas pedal only moved 1/4 inch between idle and full throttle. It wouldn’t have any more power than the same car with a “normal” gas pedal; it would just have a hair trigger and be very hard to drive smoothly. That's what playing an amp with too much gain is like. Reducing the amp’s gain is like increasing the travel of the gas pedal, so that maybe there's 6 inches of travel between idle and full throttle. The transition between no feedback and feedback will be “softer” – much less sudden, so you can safely play at a volume that is closer to the feedback threshold – in other words, a little louder. But more importantly, your amp will be much easier to drive."
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
Last Edited by Greg Heumann on Sep 07, 2013 11:10 AM
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Kingley
3114 posts
Sep 07, 2013
11:42 AM
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"Don't pay any attention to where the volume knob is. It doesn't matter"
Greg - I think what Barley means is don't get too hung up on what number the volume dial is set on. Concentrate instead on the sound of the amp. Which is of course very solid advice when learning to dial an amp in. Too many people put too much emphasis on what number that dial can reach before feedback, rather than focusing on the sound of the amp using their ear.
Last Edited by Kingley on Sep 07, 2013 11:44 AM
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Greg Heumann
2353 posts
Sep 07, 2013
12:29 PM
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@Kingley - think you SHOULD care about what number the amp is on. It really, truly does matter. When the amp feeds back with the volume knob set very low, it is JUST LIKE the gas pedal that doesn't move very far. Idle is idle, full throttle is full throttle, but the amp wants to leap from idle to full and is hard to manage in between. It is very hard for the player to manage their dynamics, which takes away a degree of expression. The number the volume control is 100% analogous to the pedal travel. If the "sweep" between idle and full throttle (in our case, feedback) is from 1 to 8, the amp is much more controllable. Instead of feedback LEAPING out of the amp, it swells. Not only can you play closer to the feedback threshold (which gives you more useful volume), you can MUCH more easily control feedback through mic technique and a volume control.
NOBODY sounds good if they're getting feedback! NOBODY sounds good if they can't be heard.
I PROMISE. It really truly does matter. The higher you can set your amp's volume knob without feedback (as long as you CAN turn it up loud enough to get feedback) the more harp friendly it is.
I demonstrated this at Hill Country Harmonica last year, literally by changing tubes in the same amp. The audience could clearly hear the difference.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
Last Edited by Greg Heumann on Sep 07, 2013 12:31 PM
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shbamac
354 posts
Sep 07, 2013
12:33 PM
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Jimi sounded good with feedback...
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Kingley
3116 posts
Sep 07, 2013
12:39 PM
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Greg -Your misunderstanding what I mean. The point is that everybody should learn to use their ears and not their eyes. Yes the number makes a difference to the sound as does swapping valves. But....here's the simple fact. When it comes to setting an amp up for a room the only real way to do it, is to use your ears, Not by looking at the volume control and thinking things like "oh it's only on 4. it needs to be on 5.5 or else I won't sound good". All rooms are different and have different needs tonally and volume wise. If a player really wants to learn to dial in their amp they must learn to use their ears. They cannot simply rely on where the dials are. That's my point. I also believe that's what Barley was trying to get at.
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Pauly22
29 posts
Sep 07, 2013
1:24 PM
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Dave Barrett has an interesting take on this, I think. The lower the gain on the preamp tubes, the more they have the opportunity to...heat up...I suppose, and get closer to saturation. Saturation causes distortion.
Don't know if there's valid science there.
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5F6H
1663 posts
Sep 07, 2013
4:58 PM
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@Pauly 22 "Dave Barrett has an interesting take on this, I think. The lower the gain on the preamp tubes, the more they have the opportunity to...heat up...I suppose, and get closer to saturation. Saturation causes distortion. Don't know if there's valid science there."
Words like "heat" & "saturation" are not particularly relevant in a technical sense, I think what Dave is trying to convey is that, in some cases, you may get to push the amp hard, more easily.
Yes, there is more heat with a low gain tube, but this heat is dissipated by the plate resistor...which may take the heat, or burn up & die.
Tubes in saturation make no sound, then they burn up & die.
The lower gain the preamp tube, the more current it draws. This pulls down the plate voltage & gain, softening and warming tone (less hard edges, sometimes not enough "edge" is left) and allows a bigger signal swing (harp mics put out a bigger signal than guitars normally) before fuzzy/buzzy disortion sets in.
The way the Princeton Reverb is wired, there's no guarantee that preamp tube swaps will work in the same way they do in a bassman/SJ for instance, but try a 12AY7 or 5751 in the slot farthest from the power tubes.
To change the sweep on the pot, without changing the tone of the amp requires adding a resistor to the volume pot. Changing preamp tubes changes the sweep but also tone & response. The "science" is: What sounds good & works without burning anything up is "good".
The amps you mention as alternatives all sound like very different beasts (low gain, cathode biased) to your Princeton (higher gain, fixed bias). But the Princeton has good resale value & is loud for its weight & size. Keep it serviced, try rebiasing, maybe try a single 6L6 (rebiased) instead of 2x6V6. But I'd hang onto it and save for the other amp in addition.
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Last Edited by 5F6H on Sep 07, 2013 5:00 PM
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SuperBee
1414 posts
Sep 07, 2013
5:23 PM
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I wish this forum had a capacity to "like" posts.
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Greg Heumann
2354 posts
Sep 07, 2013
10:46 PM
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@Kingley - I agree with what you said. I don't however think it IS what Barley meant when he said "When you put in a lower gain tube, that is the same as turning the volume knob down." That is the statement I claim is false and I stand by that claim.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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Barley Nectar
18 posts
Sep 08, 2013
12:08 AM
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OK, When I put in a lower gain tube, the amp gets quieter. You can not disput this. When I put a higher gain tube in, the amp gets louder. My reply to the OP was simplified because he does not understand tube amp basics. With the origional tube complement in a PR, that amp is not going to be too sensitive at 2 on the knob. I routinly roll back V in order to spread my usable range on my mic V pot. Yes, play on the edge. The OP has a Princeton, not a Twin. It should be very controlable and tonefull. Due to inexperence, maybe the 12AU will help temporareally, but in my opinion, that tube will nuter that amp and make it lifeless and dull. The OP is better off to strugle a little and figure how to make his amp work to its to it's fullest capicaty. BTW, some of you guys know me as Goose from the Weber and Lone Wolf forums. You guys taught me a lot now I'm trying to help someone else understand how there amp works. This thread will, no doubt be advantageous if the OP does further research in an attempt to figure out what the heck it is that we are talking about. That's how I learned, and I'm still learning...Rock on...Goose
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5F6H
1664 posts
Sep 08, 2013
1:25 AM
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Nice to see you here Goose.
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Greg Heumann
2355 posts
Sep 08, 2013
9:37 AM
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Hi, Goose
Glad to have you here. When you put in a lower gain tube, the amp gets quieter - until you raise the volume knob to compensate. As long as you can get to the feedback point, you're getting max volume from the amp with EITHER tube. The DIFFERENCE is GAIN. And that makes a real difference in the playability of the amp. If you can accept that then we don't disagree - I agree with you on the other points.
In my experience, in a single tube pre-amp amp (like a a Kalamazoo or Champ or VHT6) going to a 12AU is way too much drop. In a 2-tube preamp like the OP's amp, 1 12AU (preferably NOT in V1) is probably OK, but I don't know - don't have such an amp here to play with. In a 3-tube preamp (Bassman, et al) 2 12AU's are OK.
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***************************************************
/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
Last Edited by Greg Heumann on Sep 08, 2013 9:38 AM
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Rick Davis
2325 posts
Sep 08, 2013
10:12 AM
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A 12AU7 tube produces only 19% of the gain of a 12AX7 tube. If you swap out the 12AX7 tube for a 12AU7 your 5 watt amps just became a 1 watt amp. Your power tube may still have the potential to make 5 watts, but it can't with the reduced signal it is receiving.
Using the sports car analogy, you still have the big motor but it isn't making 500HP any more. There is a kink in the fuel line.
I like the 12AU7 in the secondary gain stage in my Bassman, with 5751 tubes in the other two sockets. There is nothing wrong with the 12AU7 tube at all except that it reduces gain (and ultimate output) too much in small amps.
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-Little Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
Tip Jar
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Kingley
3117 posts
Sep 08, 2013
11:11 AM
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Putting a 12AU7 in V3 (the phase inverter?) of a Bassman can make it sound very nice. In a Princeton though it just kills any decent sound from the amp and makes it sound like a neutered cat. The only tube I'd swap in a Princeton is V1. My personal choice is a 12AY7. A 5751 is also a good choice. A 12AU7 is too low on gain and just makes the amp really sound like crap.
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tmf714
1949 posts
Sep 08, 2013
11:39 AM
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"Putting a 12AU7 in V3 (the phase inverter?) of a Bassman can make it sound very nice."
Agreed-as long as you change out the 1w flameproof plate resistors with 2w carbon film.
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Barley Nectar
19 posts
Sep 08, 2013
11:50 AM
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Hi Greg, it is cool being here with all these great players.
As long as you can get to the feedback point, you're getting max volume from the amp with EITHER tube.
Yes, I agree compleatly. BUT, the FB point changes with any change in the amps inviorment, body position, mic, cup and soforth. In technicle terms, gain is not the same as volume. But changes in gain do result in changes in volume at a given knob setting, as you pointed out. Lovein it...BN
Last Edited by Barley Nectar on Sep 08, 2013 12:34 PM
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Rick Davis
2328 posts
Sep 08, 2013
11:57 AM
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A final word from me about the 12AU7 tubes. They draw a lot more current than 12AX7 tubes, so circuits designed for the 12AX7 may not be suitable for the 12AU7. You need to beef up the plate load resistors. They can burn out and cause a really nasty hum. It is rare but it happens. It is a cheap fix for your local amp tech.
And Pauly... Keep the SFPR, dude. It will take you far.
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-Little Rick Davis
The Blues Harp Amps Blog
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