You need an OTL

[Gordon Steadman]

My wife and I have just spent a very pleasant day with Firebottle and his wife, even though they had to stomach my cooking.

They live about three hours drive from us. As we both use Quad esl57s, he thought it would be interesting to compare my Leak Stereo 20 with his own OTL valve amp.

I was amazed when I saw it as it looks absolutely fantastic, sort of Dansette like with 50s American car overtones.

We listened to the Leak with some familiar music and as usual, I was immediately transferred to musical heaven. Then we plugged his OTL in and heaven just went a bit higher.

Anyone who likes the basic sound of the Leak but wishes to upgrade needs to hear this. Everything is tighter and more extended. We put Bach's 3rd Brandenburg on and I just sat there rocking about and tapping my feet, impossible not to get hooked into the music. Same with Take 5, same with Stevie Ray Vaughan, same with almost anything.

What a shame most of you lot are over there and we are over here. It would be worth a trip though if he could be persuaded to make you one!@!

[Ali Tait]

Aye, OTL's can be very nice. Huge sound staging too!

[Jonboy]

What a shame most of you lot are over there and we are over here. It would be worth a trip though if he could be persuaded to make you one!@!

I have a place in the Vendee so not so far for me to blag a listen :D

[DSJR]

I liked my pre-regulated model Croft OTL BUT, I understand they can't swing current and this may be a huge negative if anything but a high impedance speaker is going to be used. I admit Mr Firebottle may have other things to say about his amp - please?

Get the speakers right, and the sound is like the finest cut crystal - so light and delicate and the incredibly simple circuit in mine was a joy to behold.

[Firebottle]

You'll make my head swell with the praise Gordon, stop it.

A very enjoyable day was had by Firebottle and wife, and the food was superb:)

It was great for me to pin a 'sound' onto the British legend that is the Leak stereo 20. Very good I thought it was too.
I did have a sneaky feeling that Gordon liked the OTL as soon as it was in circuit:D Then there was more when the Firebottle all triode phono pre was inserted into the chain.
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Jonboy, when you are in the area you would be very welcome to blag a listen, let me know what you like or bring some music with you.
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David, you are absolutely right, the partnering speakers are absolutely the key to getting the best from an OTL. IMHO the only speaker for an OTL is the ESL57 but that's possibly a bit blinkered for most people.
If you have an easy speaker load, i.e. no dips in impedance and preferably a higher than average impedance then OTLs are happy.

I'm sure you know this but for others you can't expect rock concert volume levels from a typical OTL, unless you have huge numbers of output valves and an air conditioner to get rid of the heat.

The circuit of mine is simple, as shown in this thread http://theartofsound.net/forum/showthread.php?t=20955&page=5

I'm sorry I haven't invented anything different, with one pair of output valves per channel and biasing to prolong the valve life you will only achieve about 6W into 57s.

:cool:Alan

[DSJR]

My OTL was fine with ES14's and also ATC 20's if the volume was kept low, but into some large very limited edition Celef's I bought from hifi dave, the amp kept popping supply line fuses, one quiet Saturday evening having an internal firework display when I forgot the half-hourly fuse check..... Had I the nous and not been tempted by ATC's, I should have got Glenn to do the regulator circuit to mine he did for subsequent batches of OTL's.

Old big Tannoys should be fine I think since they used to me 10 ohms or so minimum IIRC.

[Alex_UK]

This is fantastic to read - AoS is all about the hifi community and reading about a get together across the channel makes it all worthwhile! :) Glad you guys had a good day, and great to see the global expansion of the AoS bakeoff creeping worldwide one continent at a time! :lol:

[Jonboy]

Jonboy, when you are in the area you would be very welcome to blag a listen, let me know what you like or bring some music with you.






Cheers Alan, i have a mate who's into hifi as well who lives just over in the Deux Sevres, looks like you are somewhere around a 3 hour drive from us as well, hopefully back over in a few months

[Firebottle]

OK Jonboy, give me a call nearer the time.
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David, without the luxury of a circuit I think Glenn was possibly trying to get a bit much from his OTL. What are the output valves and the output supply voltages?

:cool:Alan