JLH 10 Watt class A amplifier

[philpoole]

Hi AndrewT,
I established earlier Homemodder's referring to The Art of Linear Electronics, I think p97, where JLH suggests a phase splitter can be improved (as it is essentially an emitter follower) by using a Darlington or a CFP. He also suggests other phase splitter arrangements on the next page (one similar to that in the Hiraga- if I recall).
So, a reasonable comment that JLH suggested it could be improved, however, I'm reluctant to change my JLH at the moment (I'm very happy with it as it is - and like the idea of keeping it as true to the original design as possible). Maybe one day I'll consider it for my next, very low powered, amp.

Also, I suppose it could be arguable that transistor choice could affect this stage as well (a good quality, high beta transistor (suitable for driving the output) of today could compare well to a CFP using components from 1969).

[AndrewT]

I did not link the p97/98 info to the ClassA 10W/15W amplifiers, p166 to p168. JLH does not suggest in either location, that these be combined for an improved version.

Yes, it is reasonable to surmise that an improved version could be had and experiment could reveal the truth, but that would be Homemodder's extension to the JLH design, not JLH's suggestion.

[homemodder]

Originally Posted by AndrewT

I did not link the p97/98 info to the ClassA 10W/15W amplifiers, p166 to p168. JLH does not suggest in either location, that these be combined for an improved version.

Yes, it is reasonable to surmise that an improved version could be had and experiment could reveal the truth, but that would be Homemodder's extension to the JLH design, not JLH's suggestion.

No, actually his extension, if you want to learn anything from him you have to read between the lines, read all his published articles and youll notice he only guides you, and with hints on how to improve. With this design he starts just by saying what parameters to look for in the vas transistor, the rest you get the message from his book.

Dont you find it odd that he emphasized the phase splitter circuit so much in his book when its a circuit that vertually had disappeared from usage.

[homemodder]

Originally Posted by Bigun

yeah, but you do live in one of the nicest and warmest countries my friend whereas I appreciate a bit of warmth in the winter.

It gets so hot here during summer your shoes rubber melts on the tar and you need three showers a day, believe me its not so nice, I havent been able to decide which is the worst, cold or the warm weather.

[kimarin]

Originally Posted by jacobthellamer

Cheers Kenneth

2 simple power supplies. Each has a 160VA transformer, bridge rectifier and as much capacitance as could fit in the case/budget.

Case:
Enclosure RE2107H 212x70x257 - Boards | Kits | Components | Modules | Tools

I love that small casing I've built a 96 version in a bigger case. I was looking for a case that was smaller than 19" so I could build 2 monoblocks instead. Maybe this case could do. Did you build the 10w(69) or the 15w(96) version and is it really big enough to cool down the amp?

[jacobthellamer]

Originally Posted by kimarin

I love that small casing I've built a 96 version in a bigger case. I was looking for a case that was smaller than 19" so I could build 2 monoblocks instead. Maybe this case could do. Did you build the 10w(69) or the 15w(96) version and is it really big enough to cool down the amp?

I made the 15W version - It does run hot, I can touch the heatsinks for 10 secs but with discomfort. Even though the external surcace gets quite warm the components on the inside are still quite cool after a couple of hours.

[DJNUBZ]

I just got my 69 jlh working tonight. I am using a standard crc PS and MJ15003 output devices. The sound quality of this amp is impressive but I have 2 small problems. The first is a small hum in one channel, I am sure I just need to double check my connections to fix it. The second is that I love pin point imaging and this amp doesn't currently have it. The amp has cheap chinese input caps, I am guessing this may be part of the problem. Does anyone have a good cap they can recommend for a replacement? I am looking for something under $10. I would also like to know if there is anything else I could do to improve the imaging of this amp.

[chris ma]

Hi ,
I have tried the oil can caps from surplus store and it voice the amp with more tube amp sound.

[philpoole]

I currently have just some wima mkp caps on my inputs. Seems ok. I have some nice polypropylene m-caps I might try, see if I can hear any difference.

[chris ma]

May be a stupid question ,are the speakers connected in phase? The other thing I noticed that may affect the imaging output balance