[dsavitsk]

Quote:

Nope, it's based on the Espressivo or more specifically, Doug's Less-spressivo.

There are several L'espressivo articles which might not by obvious from FA's link.  Try here http://diyaudio.ecp.cc We changed the name for this amp as I have not been able to contact the designer of the original Espressivo to get his blessing for the name, and rather than step on toes, it seemed easier to just change things.
 
Also, the OPTs in this design are custom made and have both 32 and 300R taps.  This is fudgeable to an extent, so any sort of Low Z phones, from 15 to 50R are fine on the low tap.  Similarly, a range is fine on the high tap.  For 600R phones, I made an adapter to put a 600R resistor in || resulting in a 300R load.

 

[nullstring]

Quote:

 

Probably it depends on how loud you like to listen (duh) and what the output of your source is. On an amp with an opamp gain stage where you can basically raise the gain to whatever you like, you tend to run out of output current before anything else.  Here, because the gain is fixed by the tube's mu, and due to the nature of what tubes are available (i.e., there is only so much mu you can get for $2), if you need ear shattering volume, you will run out of gain first.  So, a source with a high output will allow you more swing on the amp's output.  That said, I've used it with Beyer T1's (which are 600 ohm) and a source with less than 1Vrms output, and it is plenty loud for me.  As we get closer to release, I'll post all the gain specs, etc, some of which is in that other thread.
 

Err, I am currently driving 600ohm beyers with a Starving Student Millet Hybrid, and as far as volume goes, it's more than loud enough.
I am not asking about volume.. but more about whether or not this amp will possess the voltage swing that the beyers crave.
 
Obviously you don't compare amp quality by the gain.. 
 

 

[digger945]

I am listening to a pair of Senn HD250 600 ohm, and while I can manage to turn the volume up all the way, it's just barely tolerable for a moment (very loud). For most recordings that I've listened to for the ~2 weeks I've been listening, I never go past half-way on the volume(12 o'clock), and usually much less. This is all just for the 600 ohm Senns. I've used the EAD 7k, Valab, 0404usb, and Gamma 2. It's pretty much the same for them all.
 
 

 

[reiserFS]

That looks fantastic, count me in.

 

[Pars]

My brother is using a prototype of this that I built for him with his K501s and it sounds quite good, and has plenty of gain. I tried it with my K601s as well and ditto.
 
Not sure what differences there are between the production and the prototypes though. His prototype has all of the mods done during the proto stage applied to it.

 

[mik000000]

any updates?

 

[digger945]

There should be some updates coming pretty soon.
 
 

 

[recstar24]

Err, I am currently driving 600ohm beyers with a Starving Student Millet Hybrid, and as far as volume goes, it's more than loud enough.
I am not asking about volume.. but more about whether or not this amp will possess the voltage swing that the beyers crave.
 
Obviously you don't compare amp quality by the gain.. 
 

Short answer, the amp should drive the beyers easily with plenty of room to spare. However, there is a lot of fail unfortunately in your post that probably needs to be addressed by people much smarter than me, but I'll start.

#1 - voltage is the key factor that determines volume. Voltage can be measured in any number of ways but however you measure it it boils down to how loud it eventually gets at the transducer level. To imply that an amp can supply the necessary volume but be short on voltage is a very silly thing as essentially you are talking about the same thing. Also considering headphones need mere millivolts of voltage output makes the statement sound even more funny.

#2 - gain, an amplifiers ability to amplify the signal is all about gain. An amp is supposed to amplify a signal with as minimal distortion as possible. Said amp utilizes any number of active gain stages utilizing tubes transistors or combination of both. these active devices can provide either voltage gain, current gain, or both. To reduce distortion you have to find the right settings for each of those active devices that allows the voltage gain to "compliment" or balance the responding change in current gain and vice versa. Nelson pass does a much better job at explaining this idea of dialing in an amp or load line cancellation that I am explaining but basically it's all about messing with the gain properties of the active devices that has a huge factor on the distortion quality of an amp. I would recommend reading it, it's a straight forward read and will help to understand what goes into designing an amp and how to maximize the performance of a particular topology.

http://www.passlabs.com/pdfs/articles/sweet_spot.pdf

 

[HiGHFLYiN9]

The latest photos look excellent, very much looking forward to the build. 

 

[tomb]

We're getting close.  The custom cases (shown in the pics in my posts) have been in my hands for over a week now and the first batch of PCB's were ordered Monday.  Transformers should be on the way soon, too.

 

[drclaw]

Tom, do you have an idea of what the projected price for the kit will be?

 

[tomb]

 
Quote:

Tom, do you have an idea of what the projected price for the kit will be?

Dsavitsk and I still discussing what to include in the initial offering.  For the first 30, we'll be doing partial kits, only.  There are many reasons for this, but the chief among them is to initially limit sales to those more "savy" with DIY techniques and Bills Of Material.  Even though everything is PCB-mounted, down to the RCA jacks and switches, this amp still runs at 200V+.  Because of that, we felt that partial kits would limit the customer base to those with a bit more experience and are best for the initial run.
 
What constitutes a partial kit is what we're still discussing.  At a minimum, it will be PCB, transformers, and custom case.  The transformers are custom-designed/fabricated, so there is no alternative.  Likewise, the PCB is 14" long, so a case is de-facto custom, whether from us (via Context) or you make one of your own.  So those things are a no-brainer.  There's other stuff needed for the amp that I carry, but is not available at Mouser/Digikey/Allied/Newark/et al, so we're still trying to decide on that.
 
That may all sound a bit exclusive, but remember - Duncan's TDSL shows the following that can be rolled into this amp: 6J6, 6J6-A, 6J6-W, 6J6-WA and -
1216, 5844, 5964, 6030, 6045, 6099, 6101, 6535, 6927, 6CC31, 6J6A, 6MNN3*, CK6101, CV5046, CV8160, CV8231, ECC91, M8081, T2M05
 
Most of those are very cheap tubes - on the order of a few dollars each, not counting matching.
 

 

[jdkJake]

Man, that is a LOT of tube options!

Does the final design accommodate a flexible B+/bias scheme to accommodate such a wide variety or are they really that close in construction/performance?

Looking forward to it. Should be a most interesting build.

 

[Riverback]

Tossing up between this and the MiniMAX.
 
Can't wait!

 

[Oberst Oswald]

Not to tell anybody my life's story but this thread is sort of slow going and I did make it so what the heck...
 
I couldn't hold any longer so I ordered the revised Bottlehead SEX 2.1.  This and a Beta 22 which will be done, if no problems, in a day or two will be for the Denon D-7000's.  The Torpedo looked like it would be a excellent match for the Denon's also but still seems to be in some sort of late prototype stage for some reason.  I'll have to sit this one out for now since in the DIY world the Beta 22 is near or at the peak and I need not look much further for sonic bliss as far as amps go with Denon.  
 
After this I'm entering the tube arena starting with the delivery of the Bijou kit from GJA  and looking for a new set of headphones which I'm very much still undecided.  LCD-2, Senn 800, T1's etc.  Maybe the Torpedo will fit in somehow when its released and people start building and reviewing the amp with their headphones.  This amp building bug I have is hard to kill...