1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

5881 Tweed Princeton #2

Discussion in 'Shock Brother's DIY Amps' started by jsnwhite619, Mar 26, 2021.

  1. 2L man

    2L man Tele-Meister

    Age:
    61
    Posts:
    391
    Joined:
    Nov 23, 2020
    Location:
    Finland
    I built Princeton based to what I point in the end. It has also a master volume and feedback potentiometer and they do work so I think it is good modification. I did use SS rectifier and for filtering I did use three or four stage RCR where there are series resistors also on negative between capacitors before the ground bus begins. I got inspiration after I read Merlin grounding article. I can’t say does it hum less than other more traditionally filtered amps but I like it.

    Original MV FB Schematic and writing comes searching:


    GAA's Tweed Princeton Clone
     
    Last edited: Apr 13, 2021
    jsnwhite619 likes this.
  2. NTC

    NTC Tele-Holic

    Posts:
    596
    Joined:
    Mar 17, 2003
    Jsnwhite619, which primary impedance did you use? Have you considered one of these:
    https://www.hammfg.com/part/1750B ? These look like they are barely enough for a 6L6 Champ. I have a couple of old (not Hammond sold as improved tweed Princeton) OT's that only have this transformer as a reference.
     
    Huddy likes this.
  3. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    I used the 5k. Someone here built an amp with that OT recently, but I can't remember who - maybe they'll chime in.

    The 125ESE is just massive, bigger than I expected for sure. The DSE is rated for 10 watts and is a pound lighter. I'd suggest looking into it for anyone wanting to follow along here.
     
  4. Huddy

    Huddy Tele-Holic

    Age:
    38
    Posts:
    747
    Joined:
    Nov 5, 2016
    Location:
    Newport News, VA
    Have you tried the Hammond 1750B Vibro-King Reverb Transformer? I know there's been some discussion on it on other threads.
     
  5. Huddy

    Huddy Tele-Holic

    Age:
    38
    Posts:
    747
    Joined:
    Nov 5, 2016
    Location:
    Newport News, VA
    Ha! That's what I get for not refreshing my screen for an hour ;-) @NTC read my mind!
     
    jsnwhite619 likes this.
  6. NTC

    NTC Tele-Holic

    Posts:
    596
    Joined:
    Mar 17, 2003
    I actually have two like this that have been lying around for 20 years. I was going to make a dual Princeton with alternating tremolo, but life happened.
     
  7. Huddy

    Huddy Tele-Holic

    Age:
    38
    Posts:
    747
    Joined:
    Nov 5, 2016
    Location:
    Newport News, VA
    Hey @James Knox - I think this was you that built a Champish amp with the 1750B... how'd it turn out?
     
  8. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    940
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Yeah, me and my Champ Experiments, lol. It sounded good. I might have to revisit The 1750B. The price is great. It has no bell housings so it looks “less finished” if that matters. That amp is long gone by now. I’ve been using Allen Amps OT’s for my 10 Watt Champs and they cost double the amount.

    In context with this thread, I built a 5881 Princeton just like Jason’s #1 and it has become the standard for tone for me. I just love that amp. My favorite.
     
    2L man, Huddy and jsnwhite619 like this.
  9. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Thanks - I'll take that as a complement! Do you favor single coils or humbuckers with it? I absolutely loved the first one with my Telecaster. It was a bear to dial in this one for the hotter pickups.
     
  10. 2L man

    2L man Tele-Meister

    Age:
    61
    Posts:
    391
    Joined:
    Nov 23, 2020
    Location:
    Finland
    I have H1750 on Princeton type circuit and can use 6L6GA and 5881 tubes when cathode resistor is 390 ohms and currents come about 56mA and 58mA. I was skeptical how H1750B perform because it is really small and its power rating of 10W seems way too much. Amp sound very good but it produce only about 6W. Using oscilloscope and signal generator bass frequency has drop quite a lot on 100Hz but I think some of it is because of only 20uF coupling capacitor I installed. OPT seems to saturate as well because there is no sine wave anymore.

    Another issue what I possibly should do is chance something in tonestack because using same input Vpp there come much more highs than bass. Perhaps it is typical because guitar produce quite good balance of frequencies to loudspeaker. I have not scoped this simple amp before.

    If it interests You I post more accurate currents and voltages when get back home tomorrow.
     
  11. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    940
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    I play a Tele and a Les Paul Special with P90s, so Single Coil.
     
    jsnwhite619 likes this.
  12. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    The new JJ 12ay7 finally arrived today. The one I've been using for now was a 5-6 year old EH that has seen a LOT of use. Voltages were a bit higher with the JJ, and I think it sounds better. More gain than the EH had, but still much less fuzz than a 12ax7. It's what I had last time, but I didn't have another JJ on hand until today.

    Btw, building an attenuator box using the 1/4 & 1/10 power mods on Rob's site is 100% worth it to be able to hear what an amp is doing without blowing your ears out. I'm sure what I'm picking up on the SM57 is there, but at full power or on 1/4 power, I can't hear any of the fuzz & farting out I was getting in my demo clips. So, even if it's there, it's not a problem for any kind of live setting.

    I'd appreciate if you guys could check out the voltages and see what you think. One hang up is that Rob's cell app lists a 5881 as 26W, while the website has it as 23W, which I think the latter is correct. I didn't pay attention to that, and my bias is measuring out to 110% instead of the 95% I thought it was the whole time. I know that most people go over on cathode bias and single ended, but I'd also like some honest opinions on that. I don't want him to have to swap tubes every year. The JJ 12ay7 is the new tube that is in there to stay, so the center column is what I have now.

    dewayne voltage chart.png
     
  13. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Bump
     
  14. Huddy

    Huddy Tele-Holic

    Age:
    38
    Posts:
    747
    Joined:
    Nov 5, 2016
    Location:
    Newport News, VA
    Wish I had the knowledge to competently comment but hopefully one of the several great minds on here fires up the interwebs and grace us for a few.
     
    jsnwhite619 likes this.
  15. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,479
    Joined:
    Dec 30, 2019
    Location:
    california
    Rob's bias calculator lists the 5881WXT as 26W. He also has a 5881 listed as 23W.

    Interesting the B+3 with the JJ 12AY7 is down 13 volts from the other 12A_7 tubes. Just to ease my mind... the wall voltage is checked before measurements are taken?;)

    Most 6V6 handle the 110% PD. I would think the 5881 would be able to as well.

    Was the capability of the 5881 understated like the 12W 6V6?
    How much more can the 5881 be pushed before it red plates?
     
    James Knox likes this.
  16. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    In addition to what I listed above,
    That was an error. I can't go back and edit that post now, but the EH B+3 should have been listed as 300v, so the JJ was 7v higher than that EH. My wall voltage is pretty consistent lately, usually within 1.5v of 121v-122v.

    The website calculator has both of those tubes listed and the different wattage ratings, but the Android app only has a single 5881 listed and says 26W when it is selected.
     
    James Knox likes this.
  17. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,479
    Joined:
    Dec 30, 2019
    Location:
    california
    Yeah, so the voltages look about as expected then.

    For longevity the 5881 cathode resistor could be increased. With 6V6, sometimes the amp sounds different when it is cooled down and sometimes it doesn't. All you can do is try. The recordings sound pretty good right now. Only trying a different resistor will tell you if this amp has a preference for running hot-ish.

    If the 5881 truly should be considered a 26W tube, it is only running 97%PD*. Should this amp run hotter or cooler? hah.
    If you are curious more experimenting is wanted. Where does it red plate? Where does it sound best?

    * This figure is with a guesstimated screen current subtracted from the plate and screen current measurement.
     
    James Knox likes this.
  18. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    JJ lists it as a 23W tube. Wife & kid are out today, so I was able to get out of my crazy loud office/music room and took the amp out into the living room with my dB meter. Had some interesting observations.

    One thing is that testing it in a room with furniture, a couch, bookcases, floor rug, etc., makes a noticeable difference on the meter, not just my perceived loudness: 2-3dB louder in my office than the living room with the meter 12" away.

    But, I also compared tubes & guitars and their different output levels and here's what I have. I plugged my Pro Jr into the C-Rex cabinet and tried it on this calculator. https://myhometheater.homestead.com/splcalculator.html I came out to 17W with it maxed out, the 5881 amp worked out to 10W-11W total output, not clean output. I looked up the specs for the Jensen that comes with the Pro Jr now, and for the Celestion A type in a Blues Jr and added those numbers at the bottom to compare. On paper, this amp with the Cannabis Rex should be louder than a current stock Pro Jr or Blues Jr with their factory speakers. Also, cranked with a Les Paul and through the same speaker, there isn't a whole lot of difference in the tone of the 5881 amp and the Pro Jr. I didn't record the Pro Jr today, but standing in the room and playing them, it would be a coin toss for me to pick one in a blind test.

    So, here are the results in the dB output of the different tubes & guitars, the Jensen & Celestion being hypotheticals if matched with the Pro Jr.

    upload_2021-4-18_15-59-49.png
     
  19. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    I forgot to mention that the 5y3 sounded incredible with the Telecaster. I need to measure the voltage difference, but the 5y3 and Tele was actually my favorite sounding combo of anything. It is really clean with the 5u4 and single coils, but the 5y3 and Tele had more of that old Silvertone vibe to it and everything was saturated sounding, but still more bite & definition than the humbuckers.

    As I'm typing this I just realized that I'm going to have to take the voltage readings for it because the eternal "rectifier doesn't matter" argument for single ended amps. But, there isn't even a ballpark comparison to the tone and and great cleans/no headroom difference from the 5u4 to the 5y3 rectifier change.
     
    Huddy and James Knox like this.
  20. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    36
    Posts:
    3,569
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    5y3 voltages, B+ is 6% less, so well within the +/- 20% typically quoted as "you should be fine". It absolutely changes the character and tone/feel of the amp. With a 5u4, my Telecaster stays relatively clean until halfway up the dial or more, and even then you have to hit it hard. With the 5y3, there is very little headroom at all and everything has "layer" of soft fuzz to it. Completely different sound & breakup than I've ever had with a 6v6 stock Champ/Princeton before, even at lower voltages than this - hitting the 340v B+ of the original schematic.

    Bias measures 93%

    upload_2021-4-19_10-7-29.png
     
    James Knox likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.