Tube Technology Unisys

TJ · 6th September 2001, 01:10 PM

I like to modify my current amplifier TT Unisys to TT Unisys Signature ! Can someone help me what the different between this two amp and any circuit/component changes on this two amplifier ? Thank you very much!

ste · 7th September 2001, 10:42 AM

I think it's basically a matter of output transformers. TT may be willing to supply the upgraded ones. They're easy enough to fit.
However, as an owner of a Unysis power for a while now, I would say that you're much better off doing the following:
-add valve regulated power supply
-convert to triode mode
-new old tubes, esp. for input (Tele, Mullard)
Ste

TJ · 10th September 2001, 02:28 PM

ste
I have received a email from TT , i have been told that my amp is not possible to bring the unit up to full Signature specfication ! uh ! I'll try other way ! Thank for your advice !
TJ

ste · 16th September 2001, 08:07 PM

forgot to say: disable the overall feedback in triode mode. Sounds much better.
please post to tell us how you get on.

TJ · 20th September 2001, 10:33 PM

ste, how to disable overall feedback ? did you meant no feedback ?

ste · 21st September 2001, 09:29 AM

Yeah, I meant the feedback circuit from the o/p trans. Simply disconnect. This is best done if you triode strap the el84s, as no-feedback UL operation is likely to produce too much distortion. And the downside of triode mode is, of course, loss of power and theis brings into play factors such as speaker efficiency, room size etc. This wasn't a problem for me. In fact I use the amp with just four el84s (one p/p pair per channel). This reduces power to about 7W, but it does mean you can use better valves for the money. As it happens, the Unisys was my first valve amplifier, bought with Insurance money. Having since got into the technical side, it's pretty obvious that the Unisys is designed as a kind of valve/transistor compromise, and a lot of money goes into build quality (for the export market apparently). Component quality is nothing special. Everything I've done has got the sound back to a more trad valve sound. I much prefer it now, but if I had to start again I'd probably sell it and buy something else or build from scratch.

TJ · 25th September 2001, 01:21 AM

ste..
I'll try to disconnect the feedback ! But honestly i haven't know an amp (tube amp) with no NFB ! Can u till me were can i find some info about this ? And i agree with you that my amp TT Unisis it look very high class but inside using a lot of cheap stuff ! Dull circuit board design ,cheap component and ugly soldering ! this is why i want to upgrade it . But it is good to talk to you at least i learnt something !
cheers

ste · 25th September 2001, 08:51 AM

I think there's some stuff on negative feedback on http://www.audionote.co.uk. But eliminating it is an easy mod and easily reversible.
Ste

7th September 2001, 10:42 AM	#2
ste diyAudio Member Join Date: Sep 2001	unysis I think it's basically a matter of output transformers. TT may be willing to supply the upgraded ones. They're easy enough to fit. However, as an owner of a Unysis power for a while now, I would say that you're much better off doing the following: -add valve regulated power supply -convert to triode mode -new old tubes, esp. for input (Tele, Mullard) Ste

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6th September 2001, 01:10 PM	#1
TJ diyAudio Member Join Date: Sep 2001 Location: UK	I like to modify my current amplifier TT Unisys to TT Unisys Signature ! Can someone help me what the different between this two amp and any circuit/component changes on this two amplifier ? Thank you very much!

10th September 2001, 02:28 PM	#3
TJ diyAudio Member Join Date: Sep 2001 Location: UK	ste I have received a email from TT , i have been told that my amp is not possible to bring the unit up to full Signature specfication ! uh ! I'll try other way ! Thank for your advice ! TJ

16th September 2001, 08:07 PM	#4
ste diyAudio Member Join Date: Sep 2001	forgot to say: disable the overall feedback in triode mode. Sounds much better. please post to tell us how you get on.

20th September 2001, 10:33 PM	#5
TJ diyAudio Member Join Date: Sep 2001 Location: UK	ste, how to disable overall feedback ? did you meant no feedback ?

21st September 2001, 09:29 AM	#6
ste diyAudio Member Join Date: Sep 2001	Yeah, I meant the feedback circuit from the o/p trans. Simply disconnect. This is best done if you triode strap the el84s, as no-feedback UL operation is likely to produce too much distortion. And the downside of triode mode is, of course, loss of power and theis brings into play factors such as speaker efficiency, room size etc. This wasn't a problem for me. In fact I use the amp with just four el84s (one p/p pair per channel). This reduces power to about 7W, but it does mean you can use better valves for the money. As it happens, the Unisys was my first valve amplifier, bought with Insurance money. Having since got into the technical side, it's pretty obvious that the Unisys is designed as a kind of valve/transistor compromise, and a lot of money goes into build quality (for the export market apparently). Component quality is nothing special. Everything I've done has got the sound back to a more trad valve sound. I much prefer it now, but if I had to start again I'd probably sell it and buy something else or build from scratch.

25th September 2001, 01:21 AM	#7
TJ diyAudio Member Join Date: Sep 2001 Location: UK	ste.. I'll try to disconnect the feedback ! But honestly i haven't know an amp (tube amp) with no NFB ! Can u till me were can i find some info about this ? And i agree with you that my amp TT Unisis it look very high class but inside using a lot of cheap stuff ! Dull circuit board design ,cheap component and ugly soldering ! this is why i want to upgrade it . But it is good to talk to you at least i learnt something ! cheers

25th September 2001, 08:51 AM	#8
ste diyAudio Member Join Date: Sep 2001	I think there's some stuff on negative feedback on http://www.audionote.co.uk. But eliminating it is an easy mod and easily reversible. Ste