what Headphone amp do you have

For anything about cans, and the amplifiers that drive them
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colin.hepburn
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#31

Post by colin.hepburn »

Hi All
Well I must get this H/Amp too its final finished version and cased up to date it has External PSU all psu cap are solen polyps 30H choke shunt alps pot Battery Bias this just leaves one black gate elect at C4 the output which I am thinking of changing to a polyp but as these are expensive in values of 33uf I am considering a 40uf ASC Oil-Filled Polypropylene from parts connexion in place of the black gate would this be a good idea or not http://www.partsconnexion.com/catalog/C ... sFilm.html
Does anyone have experience on these caps?

THE PSU
C LC RC CT RC
0-230volts 50mA mur820 Diode Bridge 30H choke

Hammond TX 229B230 volts 12VA 50mA 20% regulation
First Cap 5.1uf solen 650volts into Hammond choke 157G 30H@595R into 22uF solen 2.2k into 22uf 28mA current sinks 5k into 31uf 2mA current sink


212 volts out @C3
202 colts out @C4
Drive stage 5751Output Stage 12B4A
Output TX Hammond 119DA 600R/8 ohms 30Hz 20 KHz
Headphone impedance 300 ohms
All Caps are solen Polypropylenes
All Resistors are Mills 12 Watt
I have considered adding a second choke and caps and then splitting the psu to each channel would this be to good advantage if anyone wants too re model this psu for better results pleas feel free your help is welcome
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Nick
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#32

Post by Nick »

I have considered adding a second choke and caps and then splitting the psu to each channel would this be to good advantage if anyone wants too re model this psu for better results pleas feel free
Looks good to me, I would be tempted to split after the choke, saving yourself the extra choke. have two sets of RCRC stages, just double the R value in each case.

I have head good things about the ASC, but I haven't tried them myself.
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colin.hepburn
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#33

Post by colin.hepburn »

Nick Wrote:
I have head good things about the ASC, but I haven't tried them myself

Yes I had hear the ASC caps are good in psu,s not so sure if as good in output stages thou… but being oil cap I have a tendency to think they should be good perhaps bypassed with a WD paper in oil as well
Splitting PSU
I had overlooked the current taps as each 12B4a is running @ 15mA and 5751 @ 1mA total both channels 32 mA so would need to drop each side of the split psu current taps down too 15mA and 1mA on each channel correct
Thanks for your advice on this
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Will
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#34

Post by Will »

Colin it looks to me as though the output transformer is tacked on to a existing curcuit, and the output caps should be by something like 2.2uf and the output tx loaded with 300ohms or use a 600-300ohm tx.
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colin.hepburn
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#35

Post by colin.hepburn »

Hi Will
I got this Headphone amp As A kit about two years ago in standard form and have upgraded it The standard kit did not sound that good in my view all mid little bass and tizzy top the upgrades I have done have change this to good affect but I thing theres more out of this amp to come by changing the output cap from black gates to the ASC oil caps? and splitting the psu ?
This Ear+ HD High Definition Headphone Amplifier it’s about halfway down the page http://hollowstate.netfirms.com/
I have posted the design details in PDF form if anyone wants to have a look
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#36

Post by Will »

Yes I get the cap now but you have 8ohm driving 300ohm headphones this could cause some of the all mid little bass and tizz.
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colin.hepburn
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#37

Post by colin.hepburn »

Hi Will
Yes you raze a good point on the output TX? I have had my doubts on this as well I have considered other TXs but cant seen to find a 12:1 600/300ohm TX for headphones do you know of a supplier I have also considered removing the TX and connecting the output directly to the cap making it an OTL have you any thoughts on doing this
Thanks Colin
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#38

Post by Nick »

Where is the 12:1 from? 600R:300R is 1.4:1 (I think).
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colin.hepburn
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#39

Post by colin.hepburn »

Sorry the 12:1 was a reference to the 600/8 ohm TX an email from the designer of this amp at the time as I was thinking of swapping out the 600/8 for the sowter 8650 but according to him the 8650 TX would not work as the 12B4A required a TX of 12:1 http://www.sowter.co.uk/specs/8665.htm
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#40

Post by Nick »

I would have thought the 8665 wired as 4:1 would have been ok.
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#41

Post by Will »

I think the 8665 would be o.k also look at 8403 600:150+150 and in the pro. archive 8356 600:300 but the 8665 would be better if you ever changed phones.
Try it without the tx I built one years ago and 220uf was used with 220ohm headphones.
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#42

Post by colin.hepburn »

Thanks will
for the TX suggestions i don't think it will be the 8665 @£148.85 pair looks like Ill try the 220uf caps OTL style and see how it go's at £148 i may as well build a different amp and compare the two
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colin.hepburn
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#43

Post by colin.hepburn »

OK if I try this otl conversion with a 220uf cap I will need to add a resistor at the output of the cap to single ground what would be best value for this resistor
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#44

Post by Will »

10k and 0.22uf bipass cap.
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colin.hepburn
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#45

Post by colin.hepburn »

Thanks Will
thats what i thought i wish i could do this maths stuff :x know too find tow 10k resistors :?:
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