Kevin Gilmore

[KatieandDad]

I have recently purchased the following Unbalanced to Balanced Convertor boards but the vendor now tells me that he has lost the parts list.

Can anyone help ?

K.G-dynahibal KG Kevin Gilmore Unbalanced to balanced preamplifier PCB | eBay

 

[chris719]

Might find something here, not sure:

DIY RESOURCES - Kevin Gilmore DYNAMIC HEADPHONE AMPLIFIERS and POWER SUPPLIES

I linked the Wayback Machine archive because the current site seems to have adware or something it tries to push.

Looks like it's not on that page, but maybe someone on head-fi knows.

 

[KatieandDad]

Most of the components are named on the boards. Its the semiconductors which are a mystery.

 

[KatieandDad]

I'm trying to search for a quad transistor array with 2 x NPN and 2 x PNP but I'm drawing a complete blank.

 

[soundchaser]

It's likely these; not sure where you'd get them:

THAT Corporation 300-series Low-Noise Matched Transistor Array ICs

Likely the THAT 340.

 

[scott wurcer]

I'm trying to search for a quad transistor array with 2 x NPN and 2 x PNP but I'm drawing a complete blank.

Sorry for an OT but this is my new buddy, Hermes

 

[rayma]

This may help.
https://www.innerfidelity.com/images/HeadAmp_GSXmk2_Schematic_PureClassADynamicHeadphoneAmp.jpg

 

[aparatusonitus]

 

[randytsuch]

Best place I know of to go look for info, and ask questions
Do It Yourself - www.Head-Case.org

 

[Bonsai]

Sorry for an OT but this is my new buddy, Hermes

Awesome!

 

[Pars]

Take a look at this thread.
Balanced to unbalanced board - Do It Yourself - www.Head-Case.org

There is a BOM for the SMD version, but not for the thru-hole.
The ebay vendor that ripped these boards off (though Kevin doesn't seem to mind) should be able to supply a board to support their "product". The BOM would have been a spreadsheet. How do you lose it?

 

[KatieandDad]

Thank you for that, it answers all my questions.

The THAT340s are available from Farnell.

 

[KatieandDad]

Take a look at this thread.
Balanced to unbalanced board - Do It Yourself - www.Head-Case.org

There is a BOM for the SMD version, but not for the thru-hole.
The ebay vendor that ripped these boards off (though Kevin doesn't seem to mind) should be able to supply a board to support their "product". The BOM would have been a spreadsheet. How do you lose it?

He reckons his Hard Drive failed.

 

[sgrossklass]

*his backup strategy

 

[Pars]

Maybe look in his sent messages (to customers)?

 

[KatieandDad]

I managed to get most of the semiconductors from Farnell, the THAT340s, OPA445s and the MPSA06s. I had to get the MPSA56s from a UK seller on E-Bay.

Hopefully they will all be genuine parts.

 

[KatieandDad]

Any and idea what the power rails are for this?

I'm guessing at +/- 20VDC but that seems an unusual voltage.

 

[Nisbeth]

+/- 20V nominal, but the original specs from Kevin were +/- 16-20V (IIRC) so there should be some room to adapt to what you need.

 

[KatieandDad]

Is it really necessary to use E96 resistors in this design ?

I have seen two boards that use different resistor values in the same positions.

50K could surely be 49.5K.

3K0 - I can't find them

5K0 - I can't find them

700R - I can't find them

 

[Nisbeth]

Probably not. The "right" values are:

50k = 49k9
3k0 = 3k01
5k0 = 4k99
700R = 698R

Depending on where the resistors are located you can probably get away with a few percent off (value + tolerance). Because it is a differential circuit, in some places the matching between sides is probably a lot more important than the absolute value.