• Content Count

  • Joined

  • Last visited

Community Reputation

84 Excellent

About pmcuk

  • Rank
  • Birthday 17/12/1946

Personal Info

  • Location
    Kensington, London

Wigwam Info

  • Turn Table
  • Tone Arm & Cartridge
  • SUT / Phono Stage
  • Digital Source 1
    Mac Pro
  • Digital Source 2
    Audient iD4 + mics
  • DAC
  • Pre-Amp
    NE5534 stage x5 gain
  • Power Amp/s
    46 into 300b SE
  • My Speakers
    Mark Audio Alpair 10
  • Headphones
    AKG K701
  • Trade Status
    I am not in the Hi-Fi trade

Recent Profile Visitors

1,440 profile views
  1. pmcuk

    Building a 300b SE amp.

    This is no longer a 300b amp. It's now an EL12n amp. The question is which DHT to drive the EL12n with. The 10Y is brilliant. I've now rigged up a 26 and sound is rather different. Not so sparkly like you get with thoriated filaments. Sound is smooth, A little on the warm side. Good detail though not in 10Y class. It's a relaxing sound. It certainly works. A 10Y is an expensive toy these days, but it lives up to its reputation. That leaves 4P1L as the next likely choice. 26 is quite fat in the midrange. 4P1L is leaner, usually with better bass and high treble. A lighter sound, not as smooth as a 26. I'm wondering about an 01A which is a lovely silvery sound with its thoriated filaments, if it has enough weight as a driver. If it does it would be nice. There's also 2P29L and 30 special (VT-67) which I would expect to be fine but not as good as the others. I have all these.
  2. pmcuk

    Building a 300b SE amp.

    I can't post files at the moment here - PM me and we'll fix up another way of sending files. I have EL12 curves and schematics.
  3. pmcuk

    Building a 300b SE amp.

    Go for it! Get some EL12n and you may be quite surprised at the quality of sound you should get. Contact me if you need to know about filament bias, which is the way to run these DHTs.
  4. pmcuk

    Building a 300b SE amp.

    Unless you need more power, I recommend going with the EL12n. Around €10 each from several European dealers. I know this works well in triode, and I also know that you can make a really good 2 stage amp driving it with any of the DHT valves I mentioned, which are quite affordable except for the 10Y. I'm listening to the results as I write. I can put together a schematic if you're planning to build this way. I have no knowledge of the GU50 and if the mu is less than 18 it wouldn't interest me, I'm afraid. I already have a number of outputs of the 6L6 variety and the mu is too low to drive with a DHT. I've abandoned the 300b for the time being for the same reason. It's the DHT driver that makes the sound come alive. I think you'd need an OPT more like 5K, though I'm using a 3K LL1664 and it sounds fine at my operating point. For 2.6K I'd be using 2 valves in PSE. Anything like an EL84 for instance or a higher mu octal. PSE is going to be one of my next builds, together with a 26 driver stage.
  5. pmcuk

    Building a 300b SE amp.

    Yes - everything is triode connected in my amps. I don't know the mu of the GU50 in triode, but to get enough gain with a DHT driver it needs to be around 18-20 or higher. The EL12n has a mu of 18 in triode which is why it works with just a DHT driver. Possible drivers, all of which can be used in filament bias which is what I use (no bypass cap) are: 10Y - mu=8 26 - mu=8.4, max 7mA 4P1L - mu=12 2P29L - mu=9 12A - mu=8.5, max 8mA 01A - mu=8, max 4mA These are all best used with a plate choke in my experience. The 01A is a wonderful valve but a bit wimpy as a driver. I'm wondering if a pair in parallel would work at 8mA. I need to do some more checking of the schematic - I just built it yesterday!
  6. I don't know what the new amp was that made the difference - maybe it was a valve amp. A valve amp is usually going to be my solution to a sound which lacks emotional engagement. smoothness and warmth. An amp, not a preamp, since I favour feeding the amp straight from the DAC. Needs some consideration since the best valve amps in terms of value are usually pre-owned ones. We've discussed this often here, and members exchange amps.
  7. OK guys, look away if you're of a sensitive disposition or collect Welsh dressers. Here's my present system. It's in several chassis since I change things around constantly. It's a 2-stage amp, driver and output. Each stage has its own PSU with a mesh rectifier and all-polypropylene caps, plus plenty of chokes. Then there are the filament supplies for which I use bench power supplies when I'm experimenting. On the table in front is my latest solution - EL12n output tubes. The input tubes are 10Y now. Previously it was EL12n into 300b but I prefer it this way around. Oops - seems I can't attach the photo. Back to the drawing board - I haven't used up all my attachment space but it's telling me I have.....
  8. pmcuk

    Building a 300b SE amp.

    A big step forward today. The best 300b amp isn't a 300b amp at all. I've been tormenting myself for months about how to drive a 300b with a DHT or something that sounds as good as a DHT. Well, the answer is a "wrong way around" amplifier where the most gain is in the output tube and it's the input tube that is a DHT. Why did it take me so long to get here? Simply conventional thinking, that your output tube is a 300b or 2a3 or 45 and your input tube is indirectly heated with a mu of 40 and upwards. So I'm now listening to a provisional arrangement which is 10Y with a LL1660/18 interstage just used as a plate choke with a teflon FT-2 cap. This feeds a SE EL12n output stage with a LL1664 OPT (3K). None of this is optimised but it all works. This is one of the best sounding amps I've built in 15 years. It has a real DHT sound since the 10Y dominates. It's very detailed and clean. Just on the right side of bright - it's "clean" rather than warm. The EL12n is very cheap from several European dealers - around €10 each which is a real bargain. You need old-timer Y8A sockets, but they're easily available from the same dealers. I recommend this solution. Next I'm going to try a 26 as driver and maybe a 4P1L. The 10Y isn't cheap so if the 26 or 4P1L sound pretty decent we have a result. A few wammers have 26 preamps already. Gain is enough for my system - speakers are Mark Audio Alpair 10M, sensitivity around 89db. Feeding the amp with a AK4490 DAC with 2v nominal output. So my goal of a 2-stage amp where one of the tubes is a DHT works. No need for a step-up on the input. Very pleased with this.
  9. I've watched all of Vera, Poirot, Marple, Silent Witness, Ruth Rendell and nearly all the series on Ch.4 Walter Presents, which are some of the best series in Europe. Loads more besides. On Midsomer Murders at present. Did all the YouTube stuff I could find like Perry Mason, Nero Wolfe, Homicide: Life on the Street, Maigret in French etc. I'm a proper junkie.
  10. My new provider! Very good prices and plenty of variety!
  11. I have a Mazzer Major which I couldn't live without. I converted into single dosing. Looks very basic but works like a charm with no retention. I had to rewire it inside to bypass the safety cutoff in the hopper. The coffee is caught in a paper cup which fits snugly onto the metal chute. I generally use an Aeropress, though I do have a Gaggia Baby. Sometimes use a Mellitta.
  12. So, music lovers, where do you buy your coffee? I'm excluding instant coffee here - just beans and bags of ground. Can be online coffee dealers, coffee shops, supermarkets or whatever. What are your tips for: - best coffee - best value - decaf for those who drink it
  13. It's a modification of a Leak! My justification is that it sounds much, much better. I could have left it much closer to the original, with 4 x EL84s in triode with no feedback, but you lose a lot of power that way and I couldn't think of any 9 pin valves that offered more power in triode. The first ECC83 is completely unnecessary. The two ECC83 driver valves can be a differential pair or an input valve + concertina, and either way there are better valves to use here than an ECC83. Just a more modern circuit. Morgan Jones has a modded version in his Valve Amplifiers book.
  14. Talking of Leak Stereo 20s, I bought mine with my Dad many years ago. It's been through numerous rebuilds, and when converted to triode outputs with no feedback it sounded better than a Conrad Johnson Premier 4 I had briefly. My current rebuild has 8 x 6S4A triodes as output valves. I modified the chassis slightly, but it still looks like a Leak. Input is an ECC40. I added 4 chokes of 10H, 100mA in parallel pairs underneath and used solid state rectification to keep the capacitors and rectifier out of the top plate. Sounds better than all the previous versions of it, and miles better than the original. I also rewired the OPT according to Morgan Jones' suggestion so it uses all the windings. I actually haven't used the Leak for years - I build my own 300b SE amps.
  15. Calling all valve amp owners...... What's your valve amp and speaker combination, and what do you like most about it? Do you use Single Ended (SE) or Push Pull (PP) amps - any preferences? What do valve amps give you that solid state doesn't? And vice versa. Any other comments and experiences?