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Post by blackglass on Jul 11, 2016 18:42:20 GMT
I was wondering if anyone has used the Chiara headphone amp as a preamp or has any opinions on the viability of doing so. I have a pair of John Linsley Hood monoblocks and the K1450 phono stage so I thought I might try for all JLH amplification.
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Post by PinkFloyd on Jul 11, 2016 20:38:34 GMT
I was wondering if anyone has used the Chiara headphone amp as a preamp or has any opinions on the viability of doing so. I have a pair of John Linsley Hood monoblocks and the K1450 phono stage so I thought I might try for all JLH amplification. I have used the Chiara as a headphone amp but have never converted it for usage as a pre-amplifier but, yes, it can be done. Your best bet would be to contact Paul Kemble, I believe he has tried it as both a dedicated HPA and a preamp..... he will be able to give you the best report on it's efficacy as a pre amp. His e-mail address is: paulkemble@hotmail.com Best regards, Mike.
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Post by freddypipsqueek on Jul 11, 2016 20:57:21 GMT
The standard unit had variable outputs but I'm not sure what gain it adds. I've decided to park my Cyrus One - I've broken it through upgraditus so many times that I need a simple life. Looking around for a replacement it seems if you are running a line source (CD etc) a passive preamp (10k seem the norm) is the way to go and that should be easy to build with the added option of an input selector.
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Post by freddypipsqueek on Jul 11, 2016 21:07:35 GMT
Just seen you post on DIY section - It would seem a no brainer if you have JLH monoblocks. I have the schematic if you want to work out where the variable out comes from . . .
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Post by PinkFloyd on Jul 11, 2016 23:15:19 GMT
I'm sure Bill Wilson will chip in, he's the expert on all things Chiara / second to none.
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Post by videoguy on Jul 14, 2016 1:12:49 GMT
Hi Black Glass: If you wired your Chiara per the original wiring then there is a pair of outputs to feed an external amplifier. there was no provision made for any amplification at these outputs. The dual opamps only purpose is to provide an audio voltage to drive the output transistor. When used as designed the Chiara's only function is to use the volume control as a passive level control. There is a gain of 2 1/2 in the Chiara, unless modified. Chiara was a great little headphone amp., giving the user a good amount of performance vs. cost.
The SCHA amplifier would be a better choice, as it has a gain of approx. 3 times & it makes an excellent preamp. I have used mine to test Dynaco tube power amplifiers, that I have upgraded for several customers. My SCHA is a further modification beyond the excellent design improvements made by Sandy K. & Will Woodvine. There is one problem; the PCB's for the SCHA are no longer available from Silicon Chip Magazine & the complete parts kits have been discontinued by Jaycar & Altronics several years ago.
I can offer a solution as I have the PCB artwork & can make a couple of boards. The tricky part is there will be no part identifiers on the circuit card. I can provide a part layout & there is one in the SCHA thread in the DIY section. With my upgrade the opamp is changed to an LME49860 dual unit used & the power supply voltage is +-20vdc as opposed to the original +-15vdc. It becomes a great sounding headphone/preamp unit. The LME49860 is at "end of life" by TI. Mouser only had 3 pieces in stock last night; when I checked. I do have a distributor that has some in stock. I have already bought 20 pieces from them & will get another 10; as soon as an ebay item of mine sells. So there are a few available from me at $3.50ea. As opposed to UTSource for $8- ea.
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Post by freddypipsqueek on Jul 14, 2016 12:07:11 GMT
Bill - I assume therefore the 'conventional' Chiarra outputs are passive ?.
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Post by videoguy on Jul 14, 2016 18:58:04 GMT
Yes Freddy You are correct; no amplification.
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Post by freddypipsqueek on Jul 14, 2016 21:19:19 GMT
Bollocks - Just wasted money on a Passive Preamp then !!!!
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Post by videoguy on Jul 15, 2016 3:17:03 GMT
Hi Freddy: I understand your frustration that Chiara will not act as a real preamp. The original kits sold for $34.00 AU. That included the PCB, resistors & capacitors + transistors. I had 2 cases on hand & used one to house the unit & power supply & dual JLH circuit. The resistors are 1/4 watt & the capacitors are few but are Panasonic FM series. There is 1ea. dual opamp, 8ea. transistors. please take a look at the SCHA circuit diagram in the DIY section. If you need I could build up the my combination power supply/JLH board & the amplifier PCB & send them to you tested & ready for mounting in a case of your choosing. I offer modifications & manufacture professional transformerless mike preamps. Attachesd is a quote from administrator CJ. "Was the modification worthwhile? Damn right it was! The first thing that hits you is the greater authority, accuracy and tunefulness of the bass registers, it's suddenly there in spades, dynamics are far more impressive. The ever so slightly wayward treble is under more control and there seems a much easier flow to the music, instruments and events have more space. I started to listen particularly in the midrange (the main strength of this amp) to see if anything had been lost. Really nothing that I can tell but it is sweeter toned, voices in particular sound more realistic and intimate. I'd say this modification has taken the SCHA a large step in the direction of the Aclass pre/headamp' (the other more ambitious DIY headphone amplifier featured elsewhere on this forum), showing to a lesser degree many of the same attributes. Even the rather amp-fussy K701s sound great on it now. Another plus I noticed was the massive increase in effect cast over the resistance matching switch. Before this was quite subtle but now it's very obvious in effect, just like on the Aclass. I've been throwing all my favourite testing music at it today and all has been handled with great aplomb. I have not yet found any ifs, buts, maybes or any negative point after the change so far. Not a tweak bringing a subtle gain, more like a blunderbuss upgrade." Read more: rockgrotto.proboards.com/thread/3622/silicon-chip-headphone-amp-tweaks#ixzz4ERV3IVep
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Post by freddypipsqueek on Jul 15, 2016 7:56:21 GMT
Bill. I think I bought the SCHA boards and op amp in the last group buy - about 12/18 months ago ? - but as is often the case with me I just haven't had the time to do anything with them. The need for a preamp was following my Cyrus One going ill and the spontanious purchase of two Anatek MB50 monoblocks - they use a passive so the chiarra may have worked well (?). I check what I have got and put aside for the SCHA 'project' and post again. Cheers, A.
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Post by videoguy on Jul 16, 2016 3:44:38 GMT
Freddy: If my memory serves me correctly, I believe you bought the boards & dual transistors for the AKHA. I headed a group buy & shipped boards & transistors end of last July. That is the top of the line head amp/preamp. I can send you a part list for the AKHA boards, JLH & RG power supply boards, if you like. Can also answer any questions you may have on the build. NOTE: The part lists are for Mouser Electronics in Midland Texas; so you might need to transcode them if you get parts from a euro supplier.
Best Regards Bill
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Post by freddypipsqueek on Jul 16, 2016 18:07:31 GMT
PM sent - Thanks Bill.
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Post by brancolo on Jul 19, 2016 5:14:28 GMT
What are the AKHA and the SCHA?
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Post by videoguy on Jul 20, 2016 4:09:12 GMT
The SCHA is a headphone amplifier kit that was sold by Jaycar & Altronics starting around 2009. It was a design from Silicon Chip Mag. in Australia. Sandy K. & others made many improvements & turned an ordinary circuit into a very good headphone amp. You can find information on both in the DIY section. There is a dedicated thread for the SCHA. I was able to further improve the quality of the circuit by changing the opamp to one that is the same as the one listed but runs on +-22vdc rather than =-15vdc. I then set the regulated power supply for =-20vdc; this realized the full auditory potential of the modded circuit.
The AKHA is the Alex Kethel headphone amp. It is an all discrete component solid state amplifier; having a separate board for each channel & separate power supplies for each. It is for advanced builders & costs fron $225- to $300- USD. I headed a group buy for the PCB's & dual matched transistors, that shipped last summer.
The SCHA is much less expensive & gives you an amp. that will stand up to commercial amps. in the $1000- price class. The kits are no longer available but I have the artwork to make boards as needed & the part list.
Hope this answers your question. Bill Wilson
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Post by brancolo on Jul 20, 2016 19:36:48 GMT
The SCHA is a headphone amplifier kit that was sold by Jaycar & Altronics starting around 2009. Is there a schematic available for this SCHA?
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Post by videoguy on Jul 21, 2016 4:21:09 GMT
Go to the DIY section. Then to the SCHA Zone. The first thread on the page is Silicon Chip Headphone amp. tweaks. The second post on page 1 is the schematic w a detailed description. The kits have not been available for the last 4 yrs. As I mentioned I can make the PCB & provide a part list or build it for you.
I live in Fla. Check for a Personal Message.
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Post by brancolo on Jul 21, 2016 4:50:07 GMT
Go to the DIY section. Then to the SCHA Zone. The first thread on the page is Silicon Chip Headphone amp. tweaks. The second post on page 1 is the schematic w a detailed description. The kits have not been available for the last 4 yrs. As I mentioned I can make the PCB & provide a part list or build it for you. Thank you for your link! After a google search with "studio series headphone ampplifier" key I got this: www.eeweb.com/blog/extreme_circuits/studio-series-stereo-headphone-amplifierI suppose it is the original schematics. Isn't it? I still have a little preference for the JLH Chiara circuit. I live in Italy. I read your PM, thank you.
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Post by videoguy on Jul 22, 2016 4:56:16 GMT
The first amplifier I built was the Chiara; it is a good headphone amp. but the SCHA is far & away the superior amplifier. The schematic I referred you to in the SCHA heading is the improved schematic. In addition to the regulated bi polar power supply; the addition of the JLH ripple eater that is between the P.S. & the amplifier, makes all the difference in the sound quality. The Chiara goes back to 2003 & started on Head-Fi in the U.S. I built mine in early 2004 & it served me well for 6 years, it is a well designed class A British design by the late John Linsley Hood. He also did the early design of the JLH ripple eater circuit. In all honesty Chiara is a dated design; originated sometime in the 1990's. It is also strictly passive as a preamp. I have the schematic for it & can give you better choices for the opamp & output transistors; should you decide to build it.
The posts on the recent builds of Chiara is renewed interest in the circuit by some members of the forum. The web address you referenced was the review I wrote 2 years ago. The point is the SCHA is a much higher quality amp. & is better reproducing the small nuances in recordings. The preferred opamp for the SCHA is T.I. LME49860, they are no longer available but I have a limited stock of them. The final secret to squeezing the maximum quality from the circuit is to use it & operate it on +-20vdc.
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Post by brancolo on Jul 22, 2016 5:44:54 GMT
Interesting post, videoguy. I have to build both the Chiara and the SCHA then make comparison. Where can I find the latets version of power supply schematic for the SCHA?
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Post by brancolo on Jul 24, 2016 7:05:31 GMT
Videoguy, LME49860 are available in quantities here in Italy. For example, from RS-Components: tinyurl.com/jklnw2u; from Farnell: tinyurl.com/hbsh3crOn the Texas Instruments website it is indicate as "active" part. Please, take a look at your PM. Thanks!
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Post by brancolo on Jul 25, 2016 17:31:08 GMT
How to load images on this forum? It seems impossible
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Post by PinkFloyd on Jul 25, 2016 19:23:05 GMT
How to load images on this forum? It seems impossible Hi Brancolo, Welcome to the forum. The forums image attachment is currently full so the best way to show images on the forum is to open a free account with photobucket, upload your photos to photobucket and then link them here. Once you have uploaded your photos to photobucket choose the photo you want to appear here, click on the IMG link and it will turn blue.... you then right click and choose "copy" and then "paste" the link into your post here..... the image will appear here as if by magic All the best, Mike.
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Post by PinkFloyd on Jul 25, 2016 19:24:30 GMT
The result is this:
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Post by PinkFloyd on Jul 25, 2016 19:25:27 GMT
Hope that makes sense? If not, contact me and I will help you out.
Best regards,
Mike.
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