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Decware SE84-DIY build thread.


Guest David H

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Guest David H

Dave,

Did you get the EL-84s for this? That is bridgable too. Will you try that with a second one or just biamp?

Bruce

I had anticipated wanting a second amp, so I purchased tubes for both amps up front. I guess I should have mentioned that this amp is bridgeable, and it more than doubles its output into 8 ohms. The reason I suggested bi-amping rather than bridging for the addional power is once this Decware is bridged I dont see how it can be considered (S.E.T.)

I may be wrong but my view on single ended is a simple signal path with a single output section., and by bi-amping I will be using 4 s.e.t. amps instead of a pair of bridged triode amps. I suspect it makes little difference. To answer your question, Yes I will try it both ways.

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Guest David H

Bruce, last night for kicks I bridged the Decware, and hooked up a 6l6 monoblock for the second channel, then I mateched the output with a wattmeter, and gave it a run. Compared to the 6l6, the Decware has much better clarity. In mono operation the Decware has plenty of power for my Conscala's, and doesnt loose any of its charm.

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Guest David H

I have decided to go with this all aluminum chassis to transplant the Decware amp into, I ordered one large enough for a pair of the them.

HiFi DIY Audio amp chassis table top enclosure 20-16164

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Neat job!

There a very nice people at Decware.

As Mike said, this circuit is kind of classic, and no doubt similar to the one I built below. I wasn't happy with the factory wiring layout in the instructions, so rebuilt entirely. Uses two 6BQ5s single-ended and a 12AX7.

I really like your wooden chassis, though! It reminds me of the old bread board Atwater Kent Radios from the very early years.

The little amp shown is now my headphone amplifier, although it sounds huge through the Klipschorns, and in fact was once reviewed with Klipschorns.

Erik

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Guest David H

Neat job! There a very nice people at Decware. As Mike said, this circuit is kind of classic, and no doubt similar to the one I built below.

Erik, no picture shoed up for your amp.

I spoke with Steve Deckert today about upgrades for the SE84c, he suggested using V-Caps in the coupling circuit for best results, and wiring the input jacks directly from the input to the board to eliminate using the board traces.

Although I appreciate Steve's input, I cant see spending $200 for capacitors, when the originals are 50 cents each and sound quite good. I think I will be a little more conservative with the caps and use Sonicaps, Auricaps, or Audiocap Theta's and use the $$$ I saved to replace the volume pots with stepped attenuators, and high quality RCA's.

I also chose to have a pair of 6h x 8w x 16d chassis custom built from www.par-metal.com to house the units individually as mono blocks. This costs a little more, but also allows for better versatility with future applications. I will post pics as things progress.

Here is a pic of a similar chassis from Par-Metal Products I used on the VTA-SP6 preamp project. Here is a link if you would like to see the preamp build. http://forums.klipsch.com/forums/p/114302/1151246.aspx#1151246

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Hi, Dave:

Yeah, I suddenly realized I wasn't on the computer with pictures, but I'll post an outside and inside view, here. I had used this single-ended 6BQ5 amp as our main amp for quite awhile, but was never happy with how the factory-recommended parts placement and point-to-point wiring. So, I rebuilt while at the same time making provision for headphone use. The amp you just built might actually be an outstanding headphone amp, by the way, and you can either install a stereo phone jack or make an adaptor to take the headphone outputs off the binding posts. You would just need a femaile 1/4" phone jack to plug in the headphones -- or mini, whatever size would work. It's how I now use the Moth 2A3 amp I built. It is an incredibly good sounding headphone amp -- if one happens to be interested in headphone listening, that is.

Stevet Deckert is a nice guy. My wife actually talked with him years ago about some project she thought I would be interested in, and he has always been helpful, as well as fair in his pricing for the first little kit amp he offered. Lots of people liked that, and he stuck to it at a time when there was some pretty 'enthusiastic' competition. I still think the original industrial gray version of that amp is one of the neatest kits around.

On the coupling cap issue: What is the value of that -- .1uf - .22uf -- something like that? V-caps have gotten good reviews from everything I've read, and since you know how to solder you have the advantage of being able to experiment. The amp shown below has had a variety of higher-end capacitors in it, the latest of which were quite expensive Jensens I had. I've also used Kimber and others, and all of those, at least with headphones, honestly sounded too bright. Coupling capacitors DO make a difference, and it's always been my contention that one should use what works best for a certain design without respect to cost. I like the Dyna 70 I have with Hovland Musicaps, because the seemingly slightly better HF response sounds right in that amp. The one issue with this is that your amp is built on a PCB, and they can only take so much soldering and desoldering before the solder pads can get damaged and lift off. Then, it's surgery time to get things to work.

Here's my wonderful little ASUSA 6BQ5 amplifier that sounds superb with my wife's.....ahem......Bose headphones. I also use a pair of Senheiser HD 650s, but their higher impedance is much better suited to the 16ohm output Moth si 2A3 I made (the amp was no longer in production -- I bought the parts and schematic).

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Okay. I had posted the wrong amp (a Transcendent T-16 I recently completely overhauled and rewired for a friend) and I had to figure out how to remove the image.

So let's try again for the stereo 6BQ5, very similar, I'm sure to what Mike said above, and may have some elements in common with your own amp. If it were mine, I'd leave the wood! I want to show you a picture of a completely home-built regenerative radio receiver, particularly the wiring and lead dressing, that I commissioned from the father of another forum member. If one can use the word 'exquisite for electronics wiring, and I AM using that word, this is it.

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That's the exterior of the amp with the Senheisers, before I decided to try the lower impedance and far less expensive Bose. I'm glad this came up, because it's a very good example of the importance of component matching, and how more expensive is not necessarily always better -- for a given design. The Bose phones with this amp are MUCH better than the HD 650s. Really significantly better, but the overall presentation is not nearly as smooth and 3-dimensionally layered as the Senheisers with the Moth amp.

Anyway, here's the completely redone point-to-point wiring. Not much space to work with in this little thing.

Erik

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Dave:

See those blue rectangular thingies? Those are of course the interstage coupling capacitors. Two at .22uf. They were cheap, and they sounded good, but I took them out for the Jensen oil caps which cost more than the tubes, and I couldn't listen to the amp for long. It was easier to deal with connected to loudspeakers, but with headphones I couldn't stand it.

I happened to have some common orange drop types in the same value, and they were better, but the best overall result was without a doubt the .22uf 630V Solens (that were less expensive than the first blue ones!) These are the same type sold with the Transcendent OTL amp I accidentally posted above -- which, by the way, if you want a good PCB soldering work out, is a good candidate. 22 tubes with nine pins to solder each, and that's just for the installation of the tube sockets! :)

By the way, I have two nearly new Kimber caps in a .22uf value you can have if you would like to try. What do you need, two or four? They are well-made caps for the money; I just didn't care for the way they sounded in this design.

Erik

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Guest David H

Thanks for all the info, a headphone Jack is a good Idea. I also have a pair of the Bose I like them because they are extremely light and comfortable and sound good. I hear what you are saying about the caps, and I certainly do not want any additional mid bloom, already this amp provides plenty of mid, but he highs are nicely rolled. Currrently this amp reveals no harshness and I intend to keep it that way. The caps are .1uf, and are quite adequate, I have .22 kimber caps I could use here, but instead I ordered .1uf Gen1 Sonicaps, these are said to carry bass nicely and exibit mild mids. The Gen2's have moe mids and highs. If I knew for sure the V-Caps as magic as advertised, I would drop the coin for them in a minute. Until then it is the life long "who makes the best cap/ speaker wire/ Dac/ tube/ interconnect/ power cord debate etc.

Although I like the wood chassis, leaving it open is not an option. My prize posession is a Pug named Isabelle. She loves to spend time listening to music with me and often lays near the amp. Having the amp open could have less than desireable effects on a wet pug nose.

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Very cute little pooch!

It sounds like you've got everything you need for that project, Dave.

BTW: In addition to TAS and Stereophile, I also get a couple of audio review magazines from the UK, and the last issue had an interesting piece on the psychological correlates of expense -- the implication being that it can sometimes be possible to fool ourselves into thinking and believing that a component (speaker cable and interconnect in this case) sounded better based on virtue of expense and visual appeal being the main determining factors.

In the end, though, what matters is that he or she is happy with the result, and if higher cost had something to do with it, so be it! :)

I've got several pair of 2A3s that are extremely expensive -- more so than the Sovtek version of the tube, costing many times less and sound outstanding. To me, the cost of the KR and AVVT meshplates was worth it, but they also look really cool, too.

I also have a treasured pair of vintage RCAs that I just don't want to use out of fear of wearing them out. What a silly reason not to use a wonderful sounding tube, right? :)

For another nice and even lower priced stereo tube amp kit, have a look at: www.tubesandmore.com This amp actually got some pretty decent reviews, and for under $200, just as your Decware amp, is a great way to get into audio DIYing.

I totally understand your concern for Isabelle, and I think that's smart to take precautions. She really is a very neat looking girl. The lab in my Avatar had to be put down last December, which was really tough. It was a shock to post again on this forum and see her face looking back. Ok.....enough of that. :)

Have fun with your new amp! I'm curious about how headphones might work. The connections are really easy, as I'm sure you know.

Erik

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Guest David H

I also get a couple of audio review magazines from the UK, and the last issue had an interesting piece on the psychological correlates of expense -- the implication being that it can sometimes be possible to fool ourselves into thinking and believing that a component (speaker cable and interconnect in this case) sounded better based on virtue of expense and visual appeal being the main determining factors. In the end, though, what matters is that he or she is happy with the result, and if higher cost had something to do with it, so be it!

I believe this to be accurate, thanks for sharing.

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Erik,

Good to see you. I haven't been on here much the last year or so, didn't even know you had taken a break.

Sorry to hear about your dog, that can be real tough.

it is kind of weird getting on here and seeing the old names and pics. Apparently ALK is back also.

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Hi, Tom -- thanks I hope things are well with you and your family.

Yeah, it was kind of a shock to see our old Lab Sarah when I logged on again. It was especially hard for my wife. Thanks for the thought on that.

I've just been involved with lots of my own projects, and with school winding down and less papers and tests to grade, it's can be a nice way to relax.

Erik

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Guest David H

SE84 update, Last night, I received and installed the Sonicaps Gen 1, My initial impression, I am very pleased. I am going to give it a listen for a few days, before I get into the details, but seems to have more bass and overall improved detail.

In the mean time, I am still waiting for my second Decwares arrival as well as the custom chassis.

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