Valves Unlimited

Valves - 'Wot I've dun wiv em'

This is what I have built so far, this is well out of date, but as I haven't built anything valve based for a very long time, it is not really that out of date, if you get what I mean:-)

This Page will detail current and future Valve projects I am working on. When I have finished I will present full details, so you can build them your selves if you so wish.

Up and coming projects:-

New amp project started, been a long while since I built anything large. Want a new main amp for the Hi-Fi, so building two Monoblocks, using KT88 output valves, rated at 50W RMS, PSU will have all Paper in Oil Caps, all signal caps will be Paper in Oil, and Silvered Mica......This is the major build project of 2005, should have all parts for the amp by end of June, the chassis can't be made yet until I get all the transformers, and work out where they are going to go........

Looking to be a couple of awesome valve monoblocks

Completed Projects, with a short review.


1. Added 13/09/1999:- Valve Power supply:- This PSU is rated at 450-500V dc @ up to 500ma, Heater is 6.3Vac 6A.

The dc is pi filtered using a 40µF 525V cap straight after the 5AU4 tube, this feeds in to a 10H choke rated at 300ma, then there is a 80µF capacitor, this is were the HT output is tapped off for the amp. Off load voltage (No amps connected is about 650V, so might be an idea to up rate the res cap) but with the amps connected, but no signal voltage is reduced to about 480-520V, with the amp connected to a signal input, at half Volume the Voltage is about 420-450V. Overall a valve PSU seems to have made the Amp sound stronger, and not gasping as before, the amp pulls about 245-260ma, so the PSU is more than capable to supply the current needed at higher volumes. There will be a diagram available shortly on the diagrams page.

2. Added 10/06/2000:- A 10W Mono Valve Amp.

This Amp was built just to test out an Idea, which as it happens worked so well here, that I am going to implement the design in to my Main listening amps.

All O/P Iron was from Sowter, and is hand made to order. The basic design is similar to a Mullard 5-10, but I have messed around with the front end, and changed the Phase inverter slightly. The Caps are all HQ Polypropylene, and any electrolytic cap which Mullard specified in the signal paths, have been change to these poly. ones. 

Although this was a basic lash-up, the sound quality is awesome, and really does prove what a difference can be made just by changing some components 

3. Added 28/08/2001:- New o/p trannies on main power amp

Fitted new Output Transformers on the main amp. As the test above proved they would be ideal. They are from Sowter, the difference is out standing.

4. Added 19/12/2001:- Started designing a prototype 10W RMS mono block kit.

Thought that it maybe a good idea to make a reasonably affordable, valve amp kit, in the 'Just getting started' in Valve audio type area. O/P stages fine, as is the phase inverter stage, (again based on the above 10W valve amp) but I changed the I/P stage, I was going the EF86 route, but then thought I'd try a triode I/P stage. Which works, but the gain, is pretty crap, so just messing around to improve the gain of the front end abit.


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