[Parafeed]

[deleted]

 

[regal]

Great discussion thanks for the advice, my dream is an SET no NFB no cathode follower with a damping factor of 10 with Grados. My personal opinion is the best way to do this is with a transperant SS buffer, at least thats what my gut tells me.

I am real tempted to try a paralled 71a SET + OPT which would give the same output resistance as a 300B but use only .25A of heater current per tube. I just would think that a .25A DHT heater could be made on the cheap without resorting to the expensive Tentlabs. They are doing it with DHT preamps which should be pretty much as sensitive to a poor DHT supply as a headamp. But you are right everyone says use the tentlabs DHT supply for headamps, thats a challenge I would like to see overcome, just in the spirit of DIY. When/if it is I would say a paralell 71A would compete with any of the 300B commercial amps AND be a little more "sensible." You got to admit that a 300B intuitively seems overkill for headphones, my initial reaction was this is "marketing" more than engineering, but thats just an opinion till I prove it.

And thanks for the Broskie link, he is an incredible tube writer/designer.

 

[regal]

Here is the filament supply I think would be suitable for a 71A:

diyAudio



One last word on the BA, yes I am obsessed with Grados and was meaning I have built an amp that is better for Grados than the BA for under a grand, sorry for the assumption. But you have to admit that given the BA schematic you could build it for under a grand, hence it is very likely that it could be matched without the schematic if you know what your doing. Again not knocking the BA just that I am a DIY proponent and my first reaction to a 6sn7 driving a 300B is well not positive.

 

[Parafeed]

[deleted]

 

[luvdunhill]

If Grados are a special case, then many orthos must be an impossible case. Lower impedance than Grados and considerably more inefficient.

Also, anyone find it sorta ironic that a DIY design, that has never been built, and in fact is taken from a speaker amp (presumably only differing in swapping the OPT), which is claimed to be loosely based on the commercial TTVJ 307A is what's chosen to be a "best in breed DIY design" that betters a proposed top of the heap commercial design like the BA?

 

[Parafeed]

[deleted]

 

[dsavitsk]

Quote:

Originally Posted by Parafeed /img/forum/go_quote.gif if you are that concerned about damping factor with your Grado's, choose a 5K:32 transformer and a "sensible" audio tube to use ... Leaving aside winding R, reflected output imp is 5R.

That's the point, of course, is that you can't ignore DCR here. My E-P 5K:32 SE OPTs have a secondary DCR of ~3.2 ohms. Not huge, but using a 1K rp tube, damping factor goes from better than 6 to less than 4. Indeed, with a hypothetical 0 ohm rp tube, damping is DCR limited to 8, which is higher than regal is looking for.


Quote:

Originally Posted by regal /img/forum/go_quote.gif Great discussion thanks for the advice, my dream is an SET no NFB no cathode follower with a damping factor of 10 with Grados. My personal opinion is the best way to do this is with a transperant SS buffer, at least thats what my gut tells me. I am real tempted to try a paralled 71a SET + OPT which would give the same output resistance as a 300B but use only .25A of heater current per tube.

Seems an odd way to go about things -- how about a 6A3 instead? Or, doubling the primary from 5K to 10K?

At any rate, as mentioned, my SE OPTs have a secondary DCR of ~3.2 ohms. You could get dual 32 ohm windings and put them in parallel. Additionally, the autoformers on my L'espressivo 3 have a DCR of ~0.8 ohms on the lowest setting. Of course, this is a 16K:1 stepdown so you'd need a driver tube.

I also have some 8K:32 autoformers that were custom made for me with a "secondary" DCR of less than 1. The amp that uses them (6c45 CCS loaded and led biased with Mundorf Silver/Oil parafeed caps) is really lovely sounding, but I do think the bass may be too tight -- that is, over damped. Nothing screechy on the high end and very good punchyness, but maybe missing a little power.

Quote:

Originally Posted by regal /img/forum/go_quote.gif One last word on the BA, yes I am obsessed with Grados and was meaning I have built an amp that is better for Grados than the BA for under a grand, sorry for the assumption. ... Again not knocking the BA just that I am a DIY proponent and my first reaction to a 6sn7 driving a 300B is well not positive.

Am I the only one who has heard the BA that though it to be really mediocre?

Quote:

Originally Posted by Parafeed /img/forum/go_quote.gif Ask yourself this question. Why does the Woo, EC and TTVJ DHT amps (which pretty much is the list of commercially available DHT headphone amps) use a *sn7 driver?

That's a lame argument. They use them because that is what the market will accept, and because they are plentiful and cheap. Try marketing a C3m driving a 300B amp commercially, and you'll barely sell any, and when you do sell a few, your customers will throw a fit that they can't "tube roll" or indeed find any replacements at all. Yet the C3m is, by any reasonable measure, a better tube. *sn7 is the least common denominator - it works reasonably well enough and is largely inoffensive.

Quote:

Originally Posted by luvdunhill /img/forum/go_quote.gif If Grados are a special case, then many orthos must be an impossible case. Lower impedance than Grados and considerably more inefficient.

This analogy does not hold up -- damping factor necessary for good sound from a particular speaker has nothing to do with efficiency or impedance. Orthos may be lower Z and lower efficiency, but this does not necessarilly make them more or less of a special case.

I have 1 datapoint on the subject, which is that I spent 2 minutes listening, at a meet, with HE-5's, to music I didn't like, on a solid state amp with output transformers with highish DCR, and it was some of the best sound I've ever heard. I could, however, be totally misremembering.

Quote:

Originally Posted by Parafeed /img/forum/go_quote.gif Regal finds Grados to be a special case. Not everyone. Like loudspeakers? LOL

This isn't a fair argument. Speakers that one drives with 300B amps are designed to be driven by amps that have a high Zout and thus a low damping factor. Regal is arguing that Grados are not like this, and that they are more like standard commercial speakers that pair well with solid state amps. I think he is wrong, but those are the terms of his argument for better or worse.

 

[nikongod]

Nobody liked the idea of a ????:8ohm transformer with a dummy resistor across the headphone in the other thread? Ok, so I followed it up with mockery about global feedback, but eeh.
Quote:

Originally Posted by regal /img/forum/go_quote.gif Great discussion thanks for the advice, my dream is an SET no NFB no cathode follower with a damping factor of 10 with Grados.

Aside from the fact that it uses SS transistors rather than vacuum tubes and achieves a lower output impedance, could you explain how a SS device works better as a ??? (source/emitter) follower than a tube cathode follower?

Could you explain how a ??? follower is not a 100% feedback device regardless of how its made?
Quote:

Originally Posted by dsavitsk /img/forum/go_quote.gif Am I the only one who has heard the BA that though it to be really mediocre?

You may be the only person in this thread who has actually heard it at all.

Asking regal if he had heard the BA in the other thread got an answer that I think would impress a politician. Actually no direct answer from the scope jockey pushing numbers.Link to other thread, seep page 2

Regal:
Have you personally heard the BA amplifier?

 

[Beefy]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif Actually no direct answer from the scope jockey pushing numbers.Link to other thread, seep page 2

Good god, so much hyperbole.

Global NFB unlistenable? Honestly, how ridiculous......

 

[pabbi1]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif You may be the only person in this thread who has actually heard it at all.

My hero. I'd ask if anyone on the thread has heard both the BA AND the TTVJ 307a, or if everyone is talking about how great the schematics sound?

I have heard Pete's personal 307a, and it is the best amp I have ever heard, so, if the BA is that good, then it is a REALLY good amp.

Once again, 'From what I've read...' seems to rule the discussion.

Oh, and without breaking trust, the argument that a headphone amp can't be built from the 307a schematic is rather specious among this group. C'mon...

 

[nikongod]

Quote:

Originally Posted by pabbi1 /img/forum/go_quote.gif My hero. I'd ask if anyone on the thread has heard both the BA AND the TTVJ 307a, or if everyone is talking about how great the schematics sound?

I heard the 307A for sure at canjam

Im not sure if I have actually heard the BA or not so I'l just say I have not. I think the only one at canjam was in the MOT room and I didnt want to take time from someone who may actually buy it.

Quote:

Oh, and without breaking trust, the argument that a headphone amp can't be built from the 307a schematic is rather specious among this group. C'mon...

Im sure that it could be done, what I thought was weird was how I perceived the justification/motivation behind the project:
I saw the other thread in the DIY forum as saying "The commercial product is inherently flawed, Im going to out-do it using a totally different amp that im going to call the same thing" particularly after the thread before it linked above.

i dont totally agree with the comment towards not listening to the schematic (these threads are all bleeding into one!). If you have never liked a specific topology in the past, is it worth the effort to put together whatever flavor it has this month? I would try to find a friend who liked that topology to build it for himself and then listen to his... Maybe my opinion would be changed, maybe not but its key to listen to new stuff. OTOH, if you always like a certain topology and someone posts up a nominally different idea its worth nearly any effort to try it out.

I listened to a bijou at canjam too. It was quite nice. I still dont like cathodines though

At the risk of telling you to "listen to the schematic" (although maybe for the better, as you should have some solid head-time with the sound of the topology) the push-pull 307A is a fairly similar topology to the raven headphone amp with just a couple subtle tweaks. No SS CCS's, Its AC coupled rather than DC coupled, and the way the PS cap is put in there is pretty slick. If you like the way the raven sounds in general it could be a neat project.

 

[pabbi1]

Damn sore subject that Raven...

Yes, I agree - build a topology to see what it sounds like, especially if no one else has one. From what we heard of it, one afternoon, for about an hour, it sounded really good. Now, to hear it again...

 

[Paul J.]

I don't know if anybody is still lurking around looking for general discussion of the original topic, but I figured I throw in some thoughts. I'm a dedicated DIY'er. Sources are the only part of my system that weren't scratch built, and they are a modified CD player and a heavily reworked turntable. I started with cables, then a chip amp, then a few speakers, a tube amp and finally the sources. Now, I sell raw speaker drivers to the DIY crowd, mostly as an attempt to break even financially on the hobby.

I used to think that DIY always gave you more for your money. Now, I realize that if you are looking for something with mass market appeal that is neither too expensive or special, there are great bargains in commercial products. I'm not sure you can build a better 2 way bookshelf speaker for $500 than you can buy, at least without considerable effort. You certainly can't build an HT receiver. And a little tripath amp? No way. Not unless you want fancy parts or an input selector. If you want a basic pentode push pull tube amp, in the classic fashion (Mullard 5-20), there is no way you can build something better and cheaper than the Chinese (Melody/Onix SP3 for example).

Even if you are looking for something unique, the internet has created access to little enthusiast builders the can give you incredible deals. AV123 is a large example. GR Research is a smaller one. Don Allen and many others build tube amps for little more $$ than you probably could. Many of us like to think are projects are cheap, but have you ever costed out every nut and bolt in a tube amp?

But, if you want something unique, interesting, or extreme in any way, then DIY has a big advantage. What if you want a 3 watt push pull triode amp with mosfet constant current sources, no electrolytic caps, a choke input filter, very little feedback and teflon coupling caps? Mine weighs 34lbs and takes up two chassis. It would probably cost several thousand dollars to reproduce commercially. I spent about $500 after sourcing a bunch of nearly free parts (including transformers, chassis and motor run caps salvaged from several sources).

My last big speakers will 12 cu ft. (each!) pipe horns that weighed close to a couple of hundred pounds a piece. They'd probably have to sell for $10K to make a profit. My next speakers will be high efficiency open baffles with 15" woofers (my fullrangers, of course), biamplified with a little dual mono SE amps on top and a digital signal processor driving aforementioned tube amp on the bottom. With creative parts sourcing, I get it all together, including the tube preamp and SE amps, for around $400. I can't imagine selling such a setup commercially for less than a few grand.

Now, that's not to say that DIY only makes sense for extreme efforts. Its just that the value you get depends a great deal on what sort of thing you are building. If enough folks want it that they sell it as something akin to a commodity (an HT receiver, 2 way bookshelves) you can still build something, but you should do it because you want to, not to save $$. Even DIY two way kits have some big advantages over commercial gear, and may make sense. But, If you are looking for something unique, as most of us here probably are, DIY can be hugely rewarding.

Just my two (or three) cents.

Paul

 

[luvdunhill]

I just assumed everyone here had heard the amps in question. The only one I haven't heard is the theoretical amp based on Pete's 307A speaker amp.

 

[Parafeed]

[deleted]