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Old 29th May 2004, 04:44 PM   #11
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Time for a little Saturday morning fun.

Quote:
Originally posted by SY
Basic rules:

1. Ignore 99% of what "people say."
Should "Ignore 99% of what people say" be ignored?

Quote:
2. Decide if you want the amp to be neutral or to have a sound.
How do you define "neutral sound"? Here's my working definition derived from my experience: the sound of live music is neutral sound, "neutral," here, defined by reference to a given context (a particular concert hall, an outdoor venue, k d lang singing in my living room, etc); the sound of reproduced music, to the extent it deviates at all from the sound of live music, is not neutral sound. The sound of every form of reproduced music I have heard has not been neutral. I deduce that every means of reproduction creating the reproduced music I've heard is the source of the loss of neutrality. Proposition: non-neutrality therefore inheres in reproduction equipment (amps, tts, cds, sacds ...).

Quote:
3. Base your design decisions on the answer to #2.
We're going in circles.
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Old 29th May 2004, 05:17 PM   #12
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Default EACH!!! $100 EACH OPT!!! not the whole amp.

It was the middle of the night but I though I had said it clearly enough, post subject of OPT recomendations or some such and then "budget $100 each so less would be good and more would be pretty much impossible". I agree that the OPT is probalby one of the most influencial parts of the amp so what I am after is a recomendation for a "good" PP OPT for a 2A3 (or 2A3 style(6AS7))amp. I'm not looking for the best as I know it's probalby very possible / easy to spend more than $100 each on an OPT, just a good one for this design so I have a goal to save up for. What I am saying is that I am really terrible at saving money and that at some time I may have$150 - $200 burning a hole in my pocket and be able to say "OK lets get me some iron" but the odds of me being able to say to myself "OK that pair of OPT is going to cost me $275. I need to set this $25 aside and then I can get them" are pretty slim.

Thanks for reading along.

TIA,
Bryan
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Old 29th May 2004, 05:19 PM   #13
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Default a little help from your diy friends

Quote:
Originally posted by NewVintageNut
Now, I am kind of poor compared to most so I canít afford to make mistakes or to buy something only to decide I should have gone a different way and have to buy something else.
Bryan, email me your address and I'll send you some 0.22uF 630VDC teflon caps to get you on your way. For coupling purposes, almost as good as a tran$former!

Tom
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Old 29th May 2004, 05:20 PM   #14
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Default Oh, and as for the "sound" design goal...

I want what every tube lover wants, accurate and neutral but warm and oh so listenable!

Bryan
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Old 29th May 2004, 07:11 PM   #15
SY is offline SY  United States
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Quote:
How do you define "neutral sound"?
The output replicating the input. The amp having no audible influence on the sound.
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Old 29th May 2004, 11:43 PM   #16
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Quote:
As for sound quality SE usually outperforms PP, including bass respons and certainly dynamics. But given the same tubes, a PP amp will give more power than SE amp, so it will seem more bass capable and maybe even more dynamic, simply because it has more power. But a 10W SE amp will be more dynamic than a 10W PP amp.
I think this was pretty stupid of me to say. I know I'm right but who am I to tell others what I know is right?
Back to the issue of finding a good but not so expencive amp for our buddy new tube amp builder.
I've built a similar SE amp to that on Svetlana's site, only I used a 12AX7 with a CCS load as gain stage. A single 12AX7 and two 6AS7s for a stereo amp. Now I only used parts I had laying around since this was to be my shop amp, and kinda built it more for fun than sound. It turned out to sound great tho. As for OPT I used some I got from an old college, probably used in PP breadboard circuits with EL84s. The turns ratio was way off for my tubes, so max power was about 3-4W. But at least the bass respons was good. I had full power to 10Hz into 4ohms. These are probably similar to the small PP trannies found at Sowter and are cheap. I also only had 200V rails, since I was using what I had laying around, and this was the closest I got. Even so, this amp could boogie! For chassis I stole the largest kettle from the kitchen. It's one of those large aluminum types. The wife didn't like it, but I still got to sleep in my bed so it wasn't that bad. A class-A amp like this doesn't need a hefty power tranny, 100VA will do fine. So all in all I think it's possible to build a decent tube amp that doesnt cost an arm and a leg as long as you don't need a lot of power. I almost never cranked the volume to clip levels, and found as usual that 2-3 watts go a longer way than most people believe.
Another option is this little SE amp using EL84s I found here:
www.lh-electric.4t.com/bin/ef80_el84.gif
As for the 6AS7s two triodes, they are not well matched, at least I have not seen any that are, but still I find them sounding great, even paralleled.
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Old 30th May 2004, 12:21 AM   #17
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Hi Bryan,
For output transformers try the hammond 125 line like the 125ese. This particular model has several taps so you can run several different types of tubes. There are also cheaper models in the 125 line which will work, it all depends on the output tube you decide on.
These are for single end amps.
Since you do not have much money to work with you may decide to work with a triode connected pentode such as an EL34 or similar tube or maybe as someone suggested a el84, a great tube imo. If you wish to use a true triode then a Sovtek 2a3 or 6b4g would work. Use standard generic parts and do not worry about the boutique parts like fancy coupling caps or fancy input jacks or binding posts, those things do not make an amp, they only make an amp expensive. You need to make a budget and figure out how much power your speakers need and the volume you will listen at. I would (am) suggesting a single end amp since it will be cheaper for you because it uses less parts.
$100.00 is not going to get you very far unless you get stuff used or for free. Of course you could always buy the parts as you can afford them, build one channel first and listen in mono. I think all here would be willing to help you with your questions although I am sure many of us have different opinions

My opinion is that you should build a pp amp, something like this

http://www.worldaudiodesign.com/wadproducts/kecl82.html

click on the schematic link on the right for a pdf of the circuit

Whatever you decide have fun.

Andrew
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Old 30th May 2004, 01:31 AM   #18
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Quote:
I know I'm right but who am I to tell others what I know is right?
You are right in a way regarding bass response, SE amplifiers at least those without feedback have so high output impedance that they give maybe 3dB higher power at the speaker resonance, many people experiences this as stronger bass but actually it is only eveidence of an uneven frequency response. SE amps can be nice to listen to for a while but as time goes by you realise that some things are missing, sounds that are masked by the high distorsion in most SE amps.

Regarding your claim that SE amps have better dynamics, how can you claim that an amplifier that has higher distorsion would have better dynamics, actually the opposite is obviously true.

Regards Hans
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Old 30th May 2004, 04:51 AM   #19
DougL is offline DougL  United States
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Here is an inexpencive PP ampSvetlana Tech note

The output transformers are Hammond 1620 @ $46 ea at Parts Connection. The amp should cost less than $200, depending on parts cost. Will better iron sound better? Absolutely. Will this sound good? I think so. YMMV

Something Similar could be done with EL84 or SV83 and a Hammond 1608. Should cost about the same. 10 to 15 W PP AB1 amp. What you build depends on speaker efficency more than anything.

The small pentodes are easy to drive, inexpencive and make a fun amp.

I would search the forum for power amps, both PP and SE and read what was discussed. Lots of great information on this forum.

Good Luck;

Doug
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Old 30th May 2004, 07:36 PM   #20
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Default Speakers to be driven.

If I ever get the cabinets made I will most likely be driving some Buschhorn MkII with vintage AlNiCo Foster FE-103a or a pair of AlNiCo Coral 4" full range. The other current possibilities are a fantastic sounding pair of Janszen Z-412 HP or some Infinity 2000AXT. I'd say all of these are about 90 - 91 db efficient. Of course most of the time I'm not playing them all that loud anyway so it doesn't matter to much how many watts I have. When I do play them loud it's usually something that's not quite as sound quality critical so I have a big Yamaha 125 x 2 integrated for that. Maybe if I make something around 2 x 10 or so now, like that PP Svetlana, later I can make another 2 x 20 or 30 and bi-amp my Janszen's. That'd probably sound pretty ab-fab.

Thanks,
Bryan
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