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Monday, January 3, 2011

Help me to decide which types of projects I should present

Hi!

The first step is done, the blog is online. Now it's time to fill it with content. I already have some projects in mind which I would like to show here. Most of them have been published on various forums. I'd like to put them all up on my blog so everything is documented in one place.

Some of the projects are:

A platform design for single ended power amps. This is a basic architecture which is scalable from simple RC coupled with a basic PSU to sophisitcated, transformercoupled. Employing either all indirectly heated tubes, indirectly heated driver and DHT output tube or all DHT. This concept originated around an amp which originally used a 6CB5A, triode connected but was adapted for various other tubes from 45, 2A3, 300B to 801A.

Next is a full function preamp which I call the Octal preamplifier due to it's use of all Octal tubes. This is a well proven design which has been built a few times and now goes for it's MK2 revision.

Some of you might also have read about my spud amps based on the 6HS5 and 6HV5A beam triodes.

On the preamp front there are also linestage designs using 801A or other DHTs and of course my family of transformer coupled LCR RIAA phonostages using rare tubes like EC8020, WE437A, but also more commonly available types like 6AM4, E810F, D3A. I also have some ideas about different ways to doe the RIAA equalisations. So far only on paper and simulated. But yet to be built. So many projects but so little time.

Expect some of these designs to show up here during the next months. Also in the pipe line is a more long time project. A humongues 160W SE power amp based on 851 transmitting triodes. This project has been dormant for a while but is due to be contnue this year.

But I'd also be interested in what you would like to see. Therefore I added a small poll to the page. Vote for projects you'd like to see. So far I only listed SE options for power amps. I'm more a SE guy. But that doesn't mean I won't do PP. I've done a few PP designs in the past. If there is interest in this topic I will take it up and see what I can do.

Best regards

Thomas

17 comments:

  1. my vote is in, but I can only recommend publishing on topics that you yourself burn for at that given moment.

    this blog should just be a fun form of self-expression, not a drag...

    I am looking forward to what you got for us,

    --ps

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  2. Hi Peter,

    don't worry, I fully agree with you. This should be fun and not a burden. For almost all the topics I've listed, I already have finished designs. So the poll helps me to priotitize, what to publish first.

    Best regards

    Thomas

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  3. Hi Thomas,

    what about on otl-amp ?

    Kind regards,

    Hardy

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  4. Hi Hardy,

    well, I actually *like* transformers. Many of my power amps are transformer coupled between driver and outptu stage. My preamps usually employ output transformers as well. In my opinion the transformer is sonically the best solution to couple the output stage to the loudspeaker. So OTL is a field I'm not really interested in.

    Best regards

    Thomas

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  5. Thomas, I had one vote for other. My "other" is a good amp using sweep tubes in psuedo-triode mode, i.e. screen driven. I have seen a few designs that did not excite me, but a design from you would really interest me.

    I see that a Cheapo SE amp is the most popular. To that I say don't go there - we have plenty of cheap SE amps to choose from, if we talk about the "normal tubes", kt88 and variants, 2A3, etc. For example, I built an inexpensive SE amp using the PC board from www.diytube.com, called "get*set*go" and it sounds very good for what it is.

    Francois

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  6. Hi Francois,

    thanks for the vote. In fact I already have a design based on a sweep tube in triode mode. It is based on the 6CB5A. That amp has been built in various quality levels from inexpensive to quite elaborate using external PSU and all Tango iron. I alread published that circuit in some forums but will also show it here.

    There is quite some interest in inexpensive SE amps, so I certainly will show what I have there. Of course it depends on what you call inexpensive. The foundation of any good amplifier is the iron. A ready of the shelf set of transformers and chokes for a good but inexpensive SE amp will be around 400-500 Euros. That already buys you Lundahl transformes and choke a suitable PSU tranny. So that will be the pricepoint for which I can show a design. With inexpensive tubes like the 6CB5A and moderatly priced passive parts such an amp will cost around 600 Euros to build.

    This might still be considered as not inexpensive enough. Well there is always ways to get things even cheaper but that will require that the builder puts in more time of his own to maybe find suitable parts from old radios, ham gear, etc.

    But I don't want to write too much yet. Stay tuned...

    Thomas

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  7. Hi TM,
    In addition to your approach to LCR phono circuits, it would be interesting to see another category not mentioned... a project or article(s) regarding the use of multitap transformers for volume control.
    Particularly interesting to myself would be your perspective as a designer on how best to incorporate the tvc attenuators into a tube system ... Various approaches so far have been the typical freestanding "transformer preamp" ... Even as a non-expert, I still wonder why we don't see something like an integrated tube amp that consists of selector / tvc / tubed-power all in one. An even shorter-signal-path version of that might include relay selector setup ..

    Whatever articles and project you decide to document, thanks. This is how we all learn.

    rgds J.D.

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  8. Hi JD,

    in fact all my preamplifiers use TVCs for volume control. I agree with you, a TVC should be integrated into the preamp together with a driver which is able to properly drive it. I'm not fond of external TVCs even those which claim to be high impedance often sound much better if they are driven with a low impedance source like a transformer coupled line stage. In some of my preamps I use a relais controlled TVC on a PCB. It can be hooked to the 6,3V heater supply to power the relais. A photo of such a volume control can be found here: http://img695.imageshack.us/i/relaistvc.jpg/

    I'll present such a linestage design at some time.

    Best regards

    Thomas

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  9. Hello TM.
    Thank you so much for creating this blog. In addition to your projects, could you also comment from time to time on what speakers would mate well with your amplifiers or what you have found that worked well in regards to speakers selection? I would be interested to learn what sonic priorities are important to you in how you "voice" your components when designing.

    Cheers and thanks again.
    Frank M

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  10. Hi Frank,

    thanks for you comment. Yes I will present some speakers which will work well with my amps. Up to a certain degree I can also match amps to specific speakers in terms of power demand and output impedance.

    I also plan some occasional posts about the music I listen to and also my preferences in terms of sound. Things which matter to me and which I listen for in system. This should help a little to put my comments into perspective.

    Best regards

    Thomas

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  11. Hi Thomas... God will forgive me, BUT... I know you'd be able to infuse in a Class A, solid-state amp, ALL the sonic merits and designing care you put on your tubey handicrafts...
    So, without ANY shame, I ask you what do you think about a "triamp" or a "quadriamp", true Class A solid-state, single chassis "monster", say 15-20W per channell, good for any multi-amping lunatic out there...
    I'm VERY interested in knowing your unfearful point-of-view on the above;-)
    Cheers,
    S.

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  12. Dear S.

    I've read on your blog, that you are currently very happy with solid state power amplification.... you shall be forgiven ;-)
    I think it is best to first clean up the crossover situation. As far as I'm aware you currently use a solid state active crossover. Once this is replaced by a passive solution, you should reavaluate. I'm very sure, with a passive crossover between preamp and power amps, using top quality caps and coils, you will prefer an all tube amplified signal chain. Hard to imagine that you will not be blown away by the sheer details and transparency a SE 801A can provide, especially in the treble. Or the magic midrange of a 45 which will just draw you into the music...
    I'm not against solid state amplification. It is just very unlikely that I will engage in that field, there is still so much to discover with tubes.

    Best regards

    Thomas

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  13. Thomas... you WELL know I didn't forget or abandoned our "Triptycon" project;-))) - only slightly postponed by flood hassles and Franz's TGE project, almost finished...
    At the moment only wished to know your reaction on my innocent;-) quoting S.S., considering we never chatted about it.
    Let's stay (well) tuned...
    S.

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  14. Hi S.

    I know... Let's have a listen once your cross over is done. It's time for a visit in Italy again. I'm curious about your all new and improved GOTORAMA speakers. I will bring some amps. I'm always eager to learn. Who knows, I might even be impressed by your Le Classe A amps and will dive into solid state amplification. Although I think that is quite unlikely ;-)

    Best regards

    Thomas

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  15. BTW, Thomas... while apologizing for solid-state littering in yr. Blog, I was thinking that Tim de Paravicini and others did... also a Solid State can be SE and (almost) zero feedback, don't you;-)

    Seriously: I'd wish you had a listen to the "magic" of your 801/WE437 preamp AND full Hiraga's Class A multiamping...

    It's an incredibly beautiful matching.

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  16. Hi Thomas,

    first of all congratulations to your blog.

    Your name lets me guess you are just into analog playbackequipment. Is that true or are you also engaged in the digiztal world? If so, do you have some ideas for digital projects in mind?

    Best regards

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  17. Hi C.

    Thanks!

    Yes you got that right. I prefer to savor vinyl records and my focus is mainly on analog playback. I did develop several different DACs and they came out very good. However my latest DAC project is not in a state yet to be published. That will be quite a while before you'll see any digital project posted here. First there will be SE amplifiers, phono and linestages.

    Best regards

    Thomas

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