Cheap Tube Amplification- the Allied 333/Pioneer SX-34

Discussion in 'Audio Hardware' started by allied333, Feb 3, 2018.

  1. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Tube type amplifiers & tuners costs a lot of money. Not all vintage tube gear sound great either. Then, after purchase the equipment should be rebuilt for reliability & upgraded for better sound than in stock form.

    It makes sense if on a budget to buy a tube receiver. Good condition Fisher 400s, 500s & 800s costs well over $500 now. Same with Scott 340B. Enter the lowly Allied 333 & Pioneer SX-34 receivers. The Allied is the same as the Pioneer as Pioneer built the Allied 333.

    You can buy these receivers on ebay for $150-$200 in good condition. Rare wood cabinets models are about $250 if you can find one.

    I normally replace the old electrolytics, but I will take a chance on old ELNA capacitors. If the stock Elna two can capacitors doe not make AC hum and operate just slightly warmer than room temperature it is not necessary to replace the can capacitors. The receiver has four 20uF & one 40uF capacitors downstream of the power supply. I replace those capacitors. The four 6BM8 share a cathode capacitor of 50uF @ 25 volts. Replace that with an ELNA Silmic II of 220uF @ 50 volts.

    Next, replace all the coupling capacitors with Russian K40Y-9. These are the capacitors that go in-between the tube plate & input grid to the next tube stage. This capacitor replacement will remove the mediocre hazed over sonics with clean & musical sonics. The 6BM8 power tubes produces about 10 watts output per channel. Not the 15 watts of 6BQ5/EL84, but close enough! The 6BM8 are good sounding tubes. Most prefer Matsushita brand. The Matsushita are often advertised as AVO 6BM8 on ebay. Now, remove the Japanese 12AX7s and replace with RCA 12AX7 long plate tubes.

    The Allied 333/Pioneer SX-34 will now play surprisingly good. Have fun.
     
    nick99nack, H8SLKC, bluemooze and 4 others like this.
  2. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    I forgot to mention the voltage doubler capacitors below the chassis, These are two 100uF @ 160 volt capacitors wired in series. Replace these with 220uF @ 250 volt capacitors. Then, add 100uF @ 400 volt capacitor on the doubler high voltage output. No capacitor existed on the HV doubler output in the factory stock circuit. The AC ripple to the power tubes will be reduced from 16 volts to less than 5 volts. The new capacitors slightly cleans up the sound too. And, the new capacitors are smaller fitting in the old capacitors location. Plenty room exists for the new 100uF @ 400 volt capacitor too.
     
  3. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    BTW- the RCA 12AX7 tall plate are musical tubes & good for rock & roll. However, the Telefunken 12AX7 rib plate play a little more clear making it the better pick for classical music.
     
    nick99nack and Rhapsody In Red like this.
  4. TS, thank you very much for this info. I've been wanting to try tube amps and your posts give me a better understanding of what its about.
     
    H8SLKC likes this.
  5. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    It is seriously about using the right tubes and components. The stock Allied 333 is just a whisper of this high performance modified Allied 333.
     
  6. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    One more modification. The tone & loudness controls have capacitors that effect the sound. The stock capacitors are poor sounding ceramic types. Although tone controls do not have the same impact as other tube coupling capacitors, they do play a role in quality sonics. You will need polypropylene type capacitors in the tone & loudness circuit. Voltage rating can be 50 volts or higher. The tone controls have 2x .001uF, 2x .005uF, 2x 300pF & 2x 100pF plus 2x .005uF in loudness circuit. You can use more common .0047uF for .005uF & 330pF for 300pF capacitors. Note that .005uF is sometimes listed as 5000pF and .001uF is 1000pF.

    I went into many details on this Pioneer SX-34/Allied 333 as I have not found an upgrade on the internet (go figure) besides a foolish 6BM8 screen resistor/capacitor mod.
     
    H8SLKC and Rhapsody In Red like this.
  7. BIGGER Dave

    BIGGER Dave Forum Resident

    OP - Maybe ask the Moderators to fix the typo in the title? Should be Allied, not Alled.
     
    H8SLKC likes this.
  8. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Another note-
    Voicing the modified Allied 333/Pioneer SX-34 the Russian K40Y-9 are somewhat more analytical sounding in this amp, but very clear and sweet. The sound needs warming up to be more musical. At the 12AX7 factory stock .1uF capacitor, replace with a Reliable Cap type RT rated at .1uF @ 200 volt. These are available at Michael Percy Audio for $7 each. Do not confuse the low price, the RT is a high quality foil capacitor and outplays many higher-end capacitors costing much more.
     
    H8SLKC and Rhapsody In Red like this.
  9. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    The 47uF @ 63 volt polypropylene 6BM8 cathode bypass capacitor arrived. After installing the capacitor I noticed the bass became much tighter. Not a little, but a significance difference. I just put up with the somewhat flabby bass believing my speakers need a high dampening factor from the amp & my amp has a low dampening factor around 5-10. So, for $12, this is a worthwhile upgrade.
     
    H8SLKC and Rhapsody In Red like this.
  10. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Final upgrade- The RIAA phono section gets a little bright due to the muddy original coupling capacitors being replaced with ultra clear K40Y-9. Replace the RIAA 50pf & 200pF caps with four polypropylene 100pF caps. The phono section will now sound better balanced.

    Also, best output tubes are Siemens 6BM8. Do not use Mullard 6BM8 or even worst 6BM8 Miniwatt made in Australia. Muddy terrible sounding tubes.
     
    H8SLKC likes this.
  11. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    After all the mods, the tone has changed and especially so after the tone control mods. The RCA 12AX7 black plate now outperform the Telefunken 12AX7 on all type of music. This Allied 333 will perform a little more clear vs modified Fishers. But, Fisher 400/500/800 are killer if you can afford Fisher at $1000-1200 after upgrades.

    Note- if you get a squeal when switching the input selector, replace the capacitors in the multiplexer. 2x .05uF, 10uF @ 50 volts, .02uF, 2500pF, 300pF, 150pF, 5x 200pF, 1000pF, 470pF & 100pF. Use polypropylene type at 400 volts (less that 10uF @ 50 voltelectrolytic ).

    I am done, no more mods or posts.
     
    Last edited: Mar 20, 2018
    Rhapsody In Red and H8SLKC like this.
  12. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    I noticed heavy bass on rap music at higher volumes causes a high voltage drop on these bass notes. It causes a little distortion and the tuning eye tube really blinks. I changed the power supply doubler caps to 680uF and 220uF on voltage doubler output in the HV power supply. The high voltage now holds up much better and distortion during heavy bass is gone. I happened to have these 680uF @ 400 volt caps in stock. I would use 2x 1000uF @ 200 volt capacitors not to exceed 30mm x 40mm in size. I would also use a 400 volt 220uF on the voltage doubler output.
     
    Last edited: Apr 16, 2018
  13. Zensound

    Zensound Forum Resident

    How much would these upgrades cost for technician to do these?
    I would like to get a vintage tube set up with a sweet sound but am not able to do any technical work and am budget minded.
     
  14. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Less the better tubes, about $100 in parts + labor for rebuilding & upgrades. It is imperative to use Russian K40y-9 audio coupling capacitors in the rebuild. The stock tubes supplied with this Allied 333 are rather good. They are Matsushita brand and long lasting. The best tubes are Siemens 6BM8. The Siemens are rare, but many RCA label Siemens 6BM8 are available. Other tubes that can be upgraded are 12AX7s. I use RCA 12AX7 black plate. I would upgrade the 12AX7s first for largest impact on sound.

    One issue with this receiver is the rather low 12 watts per channel. But many receivers did use eEL-84 tubes at 15 watts per channel. If listening at louder levels, I would use 95dB sensitive speakers. 86dB efficient speakers is somewhat loud, but not 'party loud'.
     
    Last edited: Apr 17, 2018
  15. Zensound

    Zensound Forum Resident

    Thanks for the info!
    I heard a buddy's Scott amp the other night and enjoyed it a great deal; especially, on analog vinyl albums such as ZZ Top's Dequello.
    Started researching them and found that they have gone up in price too much for me, so to have some alternative options besides Scott and Fisher is appreciated.
     
  16. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Rebuilding is a lot of money. Try a new Asian built amplifier on ebay. You will need a separate phono amp with those Asian amps though. I will take a look on ebay and see if anything looks appealing.
     
  17. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Last edited: Apr 17, 2018
  18. Zensound

    Zensound Forum Resident

    Thanks so much; I will look into these. I know the Chinese stuff sometimes gets a bad rap on the forum but your opinions are well respected here.
     
  19. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    I am not so sure about the Music Angel, but the Yaqin construction rivals any USA made amp at twice the price.
     
    apesfan likes this.
  20. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    So, how good is this modified & upgraded Allied 333? The FM tuner is exceptional. Detail on FM can hear CDs vs playing a record with the minute record noise. The amp section is as good (clear) as Fisher 400/500/800 receivers with upgrades. Just produces 12 watts vs the 30 watts per channel of Fishers. Needs 93-96dB speakers is only issue with lower power. Same for push-pull EL84 amps/receivers.
     
  21. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    The capacitance increase to 1000uF capacitors in the high voltage voltage doubler stresses the UF4007 diodes to far. Mine failed after a few days. Parallel three UF4007 diodes in each leg of the voltage doubler. I tried higher current but slower switching 1N5408, but the slower switching diode times produced a little 'hash' reducing quality sound. The smooth sound of the UF4007 was gone with the 1n5408 diodes.
     
  22. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Just a Note- RCA label Siemens 6BM8 are also becoming scares on ebay vs two months ago. A good sounding 6BM8 brand are Matsushita 6BM8. USA tube dealers only have a few various brand 6BM8s left in stock and no matching quads available. There are always quads of Russian Svetlana 6BM8/ECL82 available, but not sure on the sonic quality.
     
  23. warp2600

    warp2600 Forum Resident

    Location:
    Budapest, Hungary
    There is a Pioneer LX35 tube receiver (1965) for sale around where I live but I haven't found any info about it on the Internet. Do you happen to know that one? Differences between that and the SX34?
     
  24. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    I cannot find anything on LX35. Possibly sales in Japan (no USA import) with a few showing up at military PX stores in Asia during the '60s Vietnam war.
     
    warp2600 likes this.
  25. allied333

    allied333 Forum Resident Thread Starter

    Location:
    Fenton, MI
    Well, I faced off my Allied 333 (Pioneer SX34) against a rebuilt Scott 272 amplifier. The Scott was rebuilt using same K40Y-9 coupling caps & 12AX7 tubes for the same sonic signature. As unbelievable as it is, the Allied 333 was a little better sounding vs the high dollar Scott amp. I think it is using only one 12AX7 amp stage per channel for phono & preamp in the Allied 333 vs three 12AX7 stages per channel in the Scott making the difference. A times, less is more.

    The Scott is a 40 watts per channel amp vs the Allied 12 watts per channel. If you do not need the power this 'lowly' Allied 333 is a very serious sounding receiver after the fore-mentioned mods I performed! But, the Scott is a serious good sounding amp too.
     

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