What is equivalent to a John Hardy M1 in DIY?

[canidoit]

Are there any DIY kits that are equivalent to the John Hardy M1 or something in the nice clean sound?

 

[baadc0de]

I'm doing this:
http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=94

to be like this:
http://www.jensen-transformers.com/as/as083.pdf

I guess that's close enough

 

[dmp]

I don't think the M1 is dual 990s?
I built a two channel 990 based preamp using Jensen JT16 inputs and JT11BM outputs with Mitsos 312/990 boards. You can build these with the servo, exactly like an M1.
I used a 12 step Grayhill for the gain in 5dB steps up to 70 dB.
This preamp is phenomenal in my opinion.

 

[baadc0de]

I don't think the M1 is dual 990s?
I built a two channel 990 based preamp using Jensen JT16 inputs and JT11BM outputs with Mitsos 312/990 boards. You can build these with the servo, exactly like an M1.
I used a 12 step Grayhill for the gain in 5dB steps up to 70 dB.
This preamp is phenomenal in my opinion.

Yes, my bad it's the JH Twin Servo, which he also makes (and I think costs quite a bit more). Whether or not it's worth it is up to the builder.. I still haven't finished mine.

 

[mitsos]

I too built a couple of those Mitsos boards!  ;D

The 990 is an awesome (sounding) amp, the M1 circuit is just built around that (and the transformers of course).  Not sure how the twin servo is, I've always wanted to build one but no time yet.  I built my M1s with the group buy Altrans (I'm still sitting on a couple of jensens but no cases to put the preamps in), and one with an OEP 1:2 but that got changed to the altran as well. Not that it sounded bad,  it worked, I just wanted to have both channels in the box identical.

You can build something very similar using a regular 312 board, any of them. Buy some 990C's from John Hardy, a 1:2 mci input trafo with the same footprint as the PCB.  Altran 3982 was the group buy one, any cinemag or jensen with the same ratio and footprint should work fine, and use a CMOB-2H or 2L for output (bifilar 600:600 output same size as the 2503, so a bit smaller than the jensen, but no huge difference. It will fit the PCB.  In fact JH was going to use that size trafo in his 500 series M1, which I'm not sure when is coming out).

You might want to do a slight mod to bias it properly, using a couple of high value resistors from the power rails to the inputs, I'm sure JH can give you more exact details, but it may not be 100% necessary.

You don't need the servo on the output, the bias is more important, you could keep the output cap, or build a more elaborate bias circuit like on JH's schemo (the same I used) and use it to dial out the DC.

I would recommend you use a low value rev log pot for gain, or better, use the custom dual pot JH uses and switch gangs for Hi/Lo gain, or dont'deal with it at all and just use a rotary switch.

 

[dmp]

I built my M1s with the group buy Altrans (I'm still sitting on a couple of jensens but no cases to put the preamps in),

I'm sitting on some of the altrans but haven't built them up yet. Have you compared the altrans to the Jensens?

 

[micaddict]

http://www.seventhcircleaudio.com/J99/J99R36/j99_about.htm

 

[Dan Kennedy]

The Great River MP-2 project isn't far away from the Hardy sound.

I would imagine Ptownkid still has boards.

 

[okgb]

I've never actually used a Hardy  , but I Love my G.R. MP-2
Solid , smooth and nothing to criticise 
Also don't have any dual stage [ or servo ] types with an input & output stage
[ well the neve type versions if that counts ]
the servo is a way of not using  [ needing  ] caps particularly the output cap
not sure if is similar to the hardy , but almost never use the gain more than 1/2 way up
on the Great River , and sometimes need to pad input for Perc and overheads
As mentioned Mitso's version is hardy like in implementation

What other dual stage's are out there ?

 

[Biasrocks]

I will second the recommendation for Dan's MP. I have four here and love the clean, large, present sound.

Actually, the version I have is a 4 channel prototype that Dan built way back when before offering it up as a commercial product. He was gracious enough to sell it to me and a 2 channel prototype of his NV type.

If you can, buy his products, he's a top notch guy and his products are second to none.  8)

Regards,
Mark