Boss HM-2 buffer mod

Started by AM, January 28, 2009, 12:18:38 PM

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AM

Hi.
I just got an old Japanese Boss HM-2. When the pedal is in the chain the bypass signal is a bit lower than when the pedal is out of the chain. We are not talking huge differences here but still...I would like to mod it. What can I do so there is no volume drop to the buffered bypassed signal comparing it with the signal when the pedal is out of the chain?
Thanks in advence.

Schemo link:

http://g5nx1q.blu.livefilestore.com/y1paN0XmzYtAtWjEGdDv2i85fYH8F5BQJHdhUezUGGEAU8EOkkdxPk1FDtG_YN-KgPGCIkGbfmG0M8TUzUlPRx0Rg/Boss%20hm-2.gif

AM

Nobody??? Hmm...it seems that it's more difficult than I thought!

Sir H C

If the jFET follower is in the bypass state too (it looks like there is none of the bypass/switching in that schematic) then loss is always there, jFET followers have loss, you could go bipolar and reduce the loss but decrease the input impedance.

cctsim

The transistor Q2 and resistor R9 can be removed to improve the bypass signal. They are not really necessary. 

You need to jumper the open side of C8 to the where the base of Q2 was.

cctsim

Here is the diagram of HM-2 with the extra buffer in the bypass:


xelalien

Quote from: cctsim on February 10, 2009, 02:46:40 PM
The transistor Q2 and resistor R9 can be removed to improve the bypass signal. They are not really necessary. 

You need to jumper the open side of C8 to the where the base of Q2 was.



Quote from: cctsim on February 10, 2009, 02:54:33 PM
Here is the diagram of HM-2 with the extra buffer in the bypass:



is it also applicable to the BOSS FZ-2 Hyper Fuzz? :icon_exclaim:  checking from the schematic:



Q6 and the corresponding 10k resistor can be removed, then jumpering the base to the 1u cap... is this valid?  :icon_question: