[Donald North]

Looking at the ASL's schematic included in the manual, the transformer output also goes the OTL's output coupling capacitor.

 

[kevin gilmore]

Quote:

Originally Posted by Donald North /img/forum/go_quote.gif There have been hi-fi amplifiers of this design, but I don't know of a commercial tube OTL/OCL headphone amp.

The smallest atmasphere. Starts at $3500. Wonderful product.
Add the teflon coupling caps and the resistors for an additional $1600.

Balanced output ONLY!

 

[asmagus]

I have OTL (WBA HPA-03 inside 1x EH Gold 6922 and 2x Tesla Gold Pin E88CC). I use it with AKG 271 mkII, 55 Ohm and just 91 dB, unusual combination but quite good combination.

 

[Omega17TheTrue]

Quote:

Originally Posted by cswann1 /img/forum/go_quote.gif If you are using a 300ohm Sennheiser, the WA2 would be a good choice. If you want to drive a 25ohm Denon the WA6 is the way to go.

That funny, i read the exact opposite somewhere in the forum.

 

[glitch39]

Quote:

Originally Posted by Donald North /img/forum/go_quote.gif This is because OTL amps are usually capacitor coupled on the output. OCL means output capacitorless. To do this with tubes, you need split rail power supplies and/or servos. There have been hi-fi amplifiers of this design, but I don't know of a commercial tube OTL/OCL headphone amp.

I believe the Little Dot Mk VI is OTL/OCL. Balanced and costs $700

 

[Denys]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Is your amp the ASL OTL Mk III? If so, it has BOTH an OTL mode *and* a Transformer-coupled mode. If you haven't tried it yet with the HD800's, you might try it before buying a new amp. With a nice set of tubes, the ASL amp sounds pretty darned good, and the availability of the 2 modes can be quite handy.

I'll do... I have RCA power tube (6BQ5) and a 12AX7 Telefunken tube. Also, all parts inside have been upgraded.

I like the sound.. I will try it and come back to you

Denys

 

[Skylab]

Well, in that case, definitely try the HD800's with the ASL before you decide you need an upgrade. Those are nice tubes, although the Tele 12AX7 might not be the best match with the HD800 - you might want to look for a pair of Mullard CV4004's or some Amperex (Holland) ECC83's which will be a little friendlier with the HD800's treble than the Telefunken.

But with the parts upgraded especially, you might be surprised that the ASL may deliver great sound with the HD800's.

 

[audiosceptic]

I've been experimenting using my Graaf GM 20 OTL amp as a headphone amp through a ASL UHC Signature into a pair of HD 800's. I have very faint hum I have to deal with but otherwise it's a nice alternative to a traditional headphone amp.

 

[Hz_joe]

Quote:

Originally Posted by Donald North /img/forum/go_quote.gif Looking at the ASL's schematic included in the manual, the transformer output also goes the OTL's output coupling capacitor.

No ! Transformer mode not goes coupling. Output transformr also use as Load when work as Choke in OTL Mode.

 

[Denys]

Quote:

Originally Posted by Skylab /img/forum/go_quote.gif Well, in that case, definitely try the HD800's with the ASL before you decide you need an upgrade. Those are nice tubes, although the Tele 12AX7 might not be the best match with the HD800 - you might want to look for a pair of Mullard CV4004's or some Amperex (Holland) ECC83's which will be a little friendlier with the HD800's treble than the Telefunken. But with the parts upgraded especially, you might be surprised that the ASL may deliver great sound with the HD800's.

Hi,

I just bought this tube on Ebay: MULLARD CV4004-M8137 TUBE ~ NOS ECC83-12AX7
Here's what the seller was saying:

Here on auction is a highly coveted Mullard M8137 / CV4004 tube with the box plates.This is brand new never used and the logo print is perfect.See picture. This tube type is a direct drop in replacement for 12ax7,ecc83,7025,6681,B759 and a few others too. The factory etched date code is 641 R4k3, indicating this tube was produced at the Mullard Mitcham factory in the UK. Mitcham and Blackburn were the best factories Mullard had and the factories produced specific tubes respectively. The Mitcham factory was the factory that produced all the CV 'box plate' tube series, the earlier and highly coveted 'D' getter EL84s and other timelessly awesome tubes as well.
The M8137 / CV4004 was produced as a ruggedized version of the 12AX7 / ECC83 tube for high gain ultra quiet application for the UK military. These have not been made for decades and Mullard M8137 / CV4004 box plates are getting hard to find in new condition. They are highly sought after for their tonal characteristics. Most agree this was one of the absolute best ecc83 / 12ax7 tube ever produced, and while many tried to imitate the sound there is only one original. If you have never tried one of these in the middle slot of an old Marshall with 3 preamp tubes, you are surely missing out! Not to mention the glorious tones you'll coax from your old Fender,Vox,Gibson,Supro,Valco,Watkins,Gretch,Hiwat t, or any other premium tube component. Put this tube in any tone slot of any amp and put on your seatbeat! If you have never heard this tube's tone, you'll be truly amazed! This was tested on my Sylvania 220 tester and tested better than new spec for filament, gas,shorts,and overall performance where 90 is considered new spec for 12ax7/ecc83.This tested 96/96.

Got it for $71 USD plus shipping...

Can't wait to receive it... With my ASL and my Senn HD800, I hope it will make a good match !!!

I never paid so much for a tube....

Denys

 

[Skylab]

IMHO, those are very nice tubes!

 

[Condocondor]

Quote:

Originally Posted by Denys /img/forum/go_quote.gif I already own an Antique Sound Lab OTL headphone amp...

Is your amp the ASL OTL Mk III? If so, it has BOTH an OTL mode *and* a Transformer-coupled mode. If you haven't tried it yet with the HD800's, you might try it before buying a new amp. With a nice set of tubes, the ASL amp sounds pretty darned good, and the availability of the 2 modes can be quite handy.

Love this idea.