[bitsnbytes]

After numerous opamp combinations I finally settled on:

8x opa827 on browndog dual soic to dip8 adapters for I/V section of the Tobby DAC
6x ada4627-1brz on browndog dual soic to dip8 adapters for lpf

Significant improvement over the stock 7x opa2604 in:
- transparency
- musicallity
- subtle sparkling highs
- detail and soundstage

Tested with:
- Tranparrent super ballanced interconnects
- Beyer T90
- Bobby headphone amp with 4x ada4627-1 brz (more detailed and spacious sound)
- 2nd Bobby headphone amp with 4x opa827 (warmer sound)
- squeezebox touch with custom linear PSU

Finnaly arrived in audio Nirwana

Hi Louis/labeelen

Can you elaborate on how you roll for the Tobby and Bobby? Soldering involved?

I'm a noob but am interested in rolling for a different signature.

Also do the sound changes apply to other headphones as well as the Beyers?

Thanks

 

[labeelen]

Hi BitsnBytes,

Rolling opamps does not involve any soldering within either the Bobby or the Tobby, all opamps are socketed and can be swapped.

The new opamps are first solderen on small opamp adaptor boards (single-to-single or single-to-dual) and then placed in the Tobby or Bobby.

I have had excellent results with:
AKG K701
Beyerdynamics T90
Sennheiser HD650 (ballanced)
Philips Fidelio X1 and X2

btw you need some soldering skills.

Regards,
Louis

 

[bitsnbytes]

Thanks Louis

I hope you won't mind if I'll start with your formula on the opa827.

WRT the op amps on adapters are they direction specific? Or the dip8 direction specific to the slots?

Thanks again
JC

 

[labeelen]

JC,

Be aware that Tobby uses dual channel opamps whereas Bobby uses single channel.

This means that using opa827 you'll have to use single to single channel soic to dip adapters for Bobby and dual single soic to dual channel dip for Tobby.

If you Google at "soic single to dual adapter orientation" you will find several pictures of the correct orientation (the round dot on the chip should match the round mark on the adapter)

Regards,

Louis

 

[bitsnbytes]

Thanks Louis
 
I'm really newbie at this, so this really helps.
 
I'll have to head over to the DIY and Opamps sections to brush up, but what you mentioned about the dual channels (Tobby) and single channel (Bobby) explained things a bit.
 
JC

 

[bitsnbytes]

@labeelen
 
Louis, just out of curiousity. For the Tobby, was there a reason for using dual ada4627-1b at the LPF versus going full opa827? was the opa827 too overwhelming if run on all 7?
 
Again, much thanks for your assist.
 
I'll try more "clarity" with the Bobby first with your ada4627-1brz, and maybe try the ada797b.

 

[labeelen]

JC,

Not sure but I think the reason for not going full Opa827 is the fact that I did not have 14pcs available

I did however do listening tests with the following combinations for I/V, LPF:

Opa2604 - Opa2604
Opa2604 - Opa1642
LME49720HA - Opa1642
Opa827 - ADA4627
Opa827 - Opa1642
Opa827 - Opa1641 - ADA4627

I finally settled on the last option, in my setup the final stage ADA4627 is not used as I am running ballanced.
As I liked the last three combinations most my consensus is that Opa827 in I/V has the biggest (positive) impact.
The choice of LPF gives the possibility of adding some nice subtle nuances.

Regards,

Louis

 

[bitsnbytes]

Thanks again Louis

I can see why you split the IV from the LPF. The dual chips in dip 8 over 7 slot will be over $200!

I think I'll try the 4 x dual opamps in the IV as you mentioned that this will affect the sound most and keeping in place the existing opamps on the LPF--instead of going full change in the Tobby. I'm just deciding between getting the OPA827 or the slightly more expensive classic OPA627...or the LME49720HA.

With regards to the Bobby, what would happen if I put DUAL opamps into the 4 sockets? Slight increase in mw output? Or not a good idea?

I'm looking to change the Bobby to OPA627 or OPA827 as well.

BTW this FSA Tobby/Bobby combo deserves more recognition.

 

[labeelen]

Some people have access to free developer samples to keep costs down.

If you can find genuine OPA627 they will be very expensive ... be aware of fake chips that are offered for low prices on ebay.

You mentioned 4 dual opamps for I/V, please be aware that you need 8 single-channel OPA827 soic chips that you solder in pairs on 4 PCB's (single channel soic to dual channel dip8) to create dual opamp equivalents.

You might consider opa1642 for LPF as these are relatively cheap and you only need 3 as they are dual channel each.

Bobby uses single channel DIP8. The pinout of single channel and dual channel is different ... you can/should not put a dual channel chip in a single channel socket!. In short: Not a good idea

Regards,

Louis

 

[bitsnbytes]

Thanks for the tips...
 
Common sense but worth repeating
 
I went with ordering with BrownDog, which actually offers some opamps already on adapters. Saves me from uncertainty, and from burning things up.
 
Although I want to start higher in the chain (Tobby) I'll proceed first with the Bobby amp, mostly because cost is a factor and just to quickly satisfy my curiosity on potential (or psychological?) sound changes.
 
I'll have to take it easy. This rolling looks like a very slippery slope.

 

[Nurgayan]

Hello everybody!
 
For Tobby I am using the following ingredients:

- Low-pass filter is served by discrete operational amplifier from Sonic Imagery Labs / Model944.
  These operational amplifiers operating in Class-A.
 
- In the current-voltage converter ICs are used LME49720HA.
 
Resulting - sound is perfect!
 
Tested with Bobby H-AMP / 4x OPA1611AID and Sennheiser HD650 / ballanced interconnects from ADL by Furutech iHP-35S-XLR

 

[labeelen]

Interesting, thanks for sharing Nurgayan.

I was wondering how you managed to fit those discrete opamps in the Tobby as it is a tight fit.

currently I'm having good results with opa827 (I/V) and opa1641 (lpf) in Tobby.

As I have a few opa1611 lying around I will try them in one of my Bobby's (currently one has 4x opa827 and the other one has 4x ada4627)
Headphones are modified Beyerdynamics T90 with balanced XLR cables.

Regards,

Louis

 

[Nurgayan]

Hi Louis,

I tried to recommended you for the I/V converter op-amps OPA827.
 
The character of the sound has changed, has become more dynamic and stronger.
 
Now I went into "Audio-Nirvana" )
 
In this connection, I like to thank Louis for this positive result!

 

[labeelen]

Thx Nurgayan,

For the past weeks I did some listening to the opa1611 in my Bobby HPA.

It is very good, but I do prefere the opa827 in the Bobby.

I like the warmth, more natural voices and better dynamics of the latter.
(Apparently you experienced the same sound signature of this chip in the Tobby)

Cheers, Louis

 

[labeelen]

Hi Nurgayan,

I have ordered some Muses (02, 8920 and 8820) and Burson V5i opamps to further improve the sound of both the Tobby and Bobby.

After trying several combinations I've settled (for Tobby) on:
OPA827 for I/V
Muses 8920 for LPF
OPA627 for SE

Result is a very tonal rich, detailed and smooth sound.

As soon as I receive the 4x Burson V5i single I will swap all opamps in the Bobby and report my findings.