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  1. prelius

    EL84 Amp with a twist...

    It's been more than 10 years since I've built this amp and it is still alive and kicking!!! After the mods it ended up in a setup of a friend in NYC. Over the years, I also built a a few toys for him, including a line and phono stage preamp, as well as a couple of power amps (GU50 and KT88 SE)...
  2. prelius

    Iron placement question

    I've had some hum trouble with placing a DC choke underneath a PT, just like in your pic. Aluminum (.063 chassis, 5052). Ended up moving a choke off the center of the PT. That solved the hum issue. YMMV... Cheers, Paul
  3. prelius

    Source for small value/low voltage electrolytic caps???

    Folks. Working on recapping ElectorVoice EV-1144A amp (a small cute SS amp, which I got because I've never owned an EV SS amp)... And would like to replace 5uF 15v electrolytic cap, all 10 of them... Since I don't typically work on SS gear, I do not keep low voltage caps in stock. Looked...
  4. prelius

    Dynaco SCA-35 Repackage Idea?

    Buzz I'd build shield walls inside the enclosure out of .025 or .04 aluminum plates (size them to fit inside your enclosure). One from back to front, between PT and OPTs. This will block off the PSU and 12V module Another one from back to front, between the input module and OPT. This will shield...
  5. prelius

    New Product Idea - Suggestions Wanted

    I would also add Bluetooth input, purely for practical purposes. I had to add BT to my preamp after a few months of complaints and nagging from my younger part of the family (kids and their friends) who wanted to use our main system, but never could find/be bothered with cords, connectors, etc...
  6. prelius

    Help with Edcor Transformers

    I've had the same issue with Edcor trannies a few years back... They told me the same thing, and said it has no impact on performance, and that the laminations were still isolated. I tried to clean them up with 000 steel wool, did not help much. I ended up just removing the bells, and spray...
  7. prelius

    ElectroVoice DIY manuals sought...

    Folks, I recently realized I've accumulated a few EV drivers over the years, and now would like to make something out of them... With that, I am looking for two EV KD manuals: KD7 DIY manual (Baronet), and KD9 DIY Manual (Marquis). Baronet is a smaller version of the Aristoctrats, and also...
  8. prelius

    Ideas for a 47 SE amp in pentode mode.

    47 is a predecessor to 42/6F6, so in theory, any schematics for 42/6F6 should work. If you want to stick with 2.5V heaters, a 27 will work well for a triode connected 47. For a pentode output section, a 24 should do the trick... If you are willing to go with 6.3v heater tube in the driver...
  9. prelius

    Current Analog Room Setup 45 SET with Arcturus Blue Glass 37-A Tubes

    Very spiffy looking amp! All you need now is a globe 80... Cheers, Paul
  10. prelius

    Show us your flea-watts amps!

    Stephe, I just started the project, and I have quite a few things to try before having a final schematics. I'd be happy to post what I am working with, but I'd rather do it in a separate thread in order not to crowd this thread with the discussion of a particular amp... At this point, there...
  11. prelius

    Show us your flea-watts amps!

    Had some downtime this past week, so I put this spud together: 6AG7 wired in triode mode. Puts out about 1W. Works very well with both 300 Ohms Senh's and 32 Ohm Grado's. Can drive my Cornwalls too.. :-)
  12. prelius

    300B output transformers

    I would also look for James 6123H. 2.5K, 3K, 5K PRI. No longer produced, but still can be found. I wish I bought more of them back when they were widely available... Cheers, Paul.
  13. prelius

    Help diagnosing noise in a Marantz 7 circuit

    To me it sounds like oscillation with external interference mixed in.. I would check all grounding for the treble, bass and loudness compensator pots; if you have shielded wire to/from these pots, make sure they are properly grounded too; check the all the solder joints on tubes 3 (both...
  14. prelius

    6V6GT build thread - my first build

    This issue can be easily fixed. Look at the pins from underneath. Eash of them has a notch, which supposed to prevent the pin from coming out of the hole. Sometimes, during stamping process, it is not pushed out enough. Just take a flat head screwdriver and pry the notch a bit outwards. Easy...
  15. prelius

    Kegger/blueglow kt88 project

    Robnec, There are some people who have built parallel SEP per Kegger's schematics. I did not for the following reasons. I have high efficiency speakers (Cornwalls, KG3.2 and EV Aristocrats), so I don't need 20W output. And if I needed more than my SEP can deliver (which is sometimes the case...
  16. prelius

    KT88 SE Abdellah (modified by Alex Gendrano) + AK..

    Thank you, David Below is a description of my PSU. The latest version delivers: B+ 400V@200mA; 6.3V@5A AC; +12V@1A DC for VU indicators, remote volume/source switch control, etc. The B+ rectifier is SS, and I use 5V/3A winding with a SS voltage doubler to get 12V. On the PSU chassis, I have a...
  17. prelius

    Kt88/kt120 build

    It would be barely enough for KT88. Consider, for example, BlueGlow amp with KT88. The output is biased at 82mA, input tubes around 2mA. So you have 84mA per channel, or 168mA for the entire amp. Your tranny is rated 180mA, so you have less than 10% headroom. While it will be OK for KT88, it...
  18. prelius

    Using a LCR meter to measure output transformer impedance

    Can this test be performed in-circuit?
  19. prelius

    KT88 SE Abdellah (modified by Alex Gendrano) + AK..

    Thank you Bob! Below is a link to Amazon for a multiple connector kit that I bought... https://www.amazon.com/gp/product/B07F5B5LLX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I do see the benefits of building the PSU as a separate unit. As I mentioned in the original post, I have no hum...
  20. prelius

    KT88 SE Abdellah (modified by Alex Gendrano) + AK..

    There are good chassis makers, but the the business of custom chassis (or anything custom) is not cheap or inexpensive. One of my lifelong friends owned a small metal shop. He made several custom chassis for me, and we discussed this topic. The process of actual chassis making is not that...
  21. prelius

    KT88 SE Abdellah (modified by Alex Gendrano) + AK..

    Just wanted to show my new version of the amp... This is a "baby" KT88, mostly because I did not have Edcor CXEs on hand, so I used GXSE, on which I replaced the bells. As you can see, there are two separate chassis: one for PSU, and one for the amp. The amp is SS rectified, in a CLC-LC-CL...
  22. prelius

    Different ways to implement local FB in SE amp

    Recently, I came across an interesting schematics for EL84 SE amp. Schematics is attached. Two things that attracted my attention: 1. Fixed bias for power tube - typically EL84 SE has cathode bias, and the datasheets do not recommend running EL84 with fixed bias. Typically (as far as I can...
  23. prelius

    Blueglow 2020 Amp Build Ideas

    Mark, Love your videos... You've covered a lot about SE amps, so building another one (mid or hi FI), will be a repeat of the previous topic, albeit with some differences, like using a pentode as a driver (WE91A comes to mind), but nevertheless... I think a PP amp build video would be...
  24. prelius

    Kegger/blueglow kt88 project

    Agree with Kevin, picture A is a proper way of stabilizing screen voltage. I don't think you need 100 Ohm resistor there. Voltage regulation in UL mode makes no sense (as in pic B)... UL mode is a type of feedback, which by its nature provides variable voltage applied to the screen. By...
  25. prelius

    Looking for a recommendation on electric pianos

    Folks, My teenage daughter showed an interest in playing the piano again. She had played the instrument for 6 years, and then decided to take a two year break. But at the end of last school year she said she wanted to play again... Having learnt albeit an inexpensive (as in free piano), but...
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