"Bride of Zen" Pre Amp

[rajan-]

For some time now, I had the Pre-amp sitting in a show box.

I was ready to order a chassis from DIY audio,

Then I noticed the gift box that came with Wine.

Perfect Size.

Over the weekend, sanded and stained with Jarrah wood colour.
Didnt make it perfect, as I was after a retro look.

Cut holes for connectors and front LED

Mounted all hardware, Torroidal Transformer and Boards

Changed all the temp wiring to good quality wires, Signal in and out are Shielded cables.

Not fitted a volume control yet. Want to get a stepped attenuator.

Until then, I am using my universal motorized Alps volume control.


"Bride of Zen" Pre amplifier:
Class - A Preamplifier from Nelson Pass (https://www.passdiy.com/project/preamplifiers/bride-of-zen)

What I have is a modded design , which is a Cascode version of the BOZ.
(Courtesy, Gareth from Sydney)
I have listened to an original BOZ. This modded version takes the performance higher without taking any strengths of BOZ (IMHO)

I played it directly from my Phone Aux, and connected it to a Schiit Modi Uber (which is a few years old now)

these are driving my Bridged Amp Camp Amps, and Horns, with a volume control in between Pre and Power amps.


Points noted during the final assembly,

1. Grounding
I didnt have the Blue colour Ground wire and was noticing irregular hum, and after some thoughts realised that this is my first wood cabinet, and I cant chassis mount the grounding points. Rigged up the 12Guage ground, and all humming gone.

2. Cables
thi s is a controversial subject.
while I was using this Pre in the shoe Box, I had all kinds of hotch potch wires everywhere, the Signal in and out wire were a single strand cheap wire.
the shielded cables are not any exotic variety, but very decent pro audio Mic cables (4 core). I joined a pair for added copper.
I didnt need to ground the shield , there was no humming, no interferences. so far Happy with this,
Now that I noticed the difference, I will look for some Mil spec Shielded Silver cables and experiment.

.
future plans for this Pre-amp.

1) Add a tube buffer with a bypass & Gain adjustments switchs
This should take care of any harshness coming from streaming audio or old digital recording, and restore any lack of weight
introduce a certain level of tubiness, if I feel like it

2) Stepped Attenuator Volume control

 

[rajan-]

External Motorized Apls Pot Volume control

 

[raghupb]

Like the way you have repurposed the wine box.
Let you preamp age well like wine
Cheers,
Raghu

 

[Kannan]

True spirit of DIY.

 

[reubensm]

very nice, the wine box and its 'contents' look great

 

[rajan-]

Fixed the LED connections.
Didnt get matching blue for the Amp Camp Power amps, got some blue.

And it found its place on the rack.

 

[amrutmhatre90]

Fixed the LED connections.
Didnt get matching blue for the Amp Camp Power amps, got some blue.

And it found its place on the rack.

Is the Pre amp connected to ACA amps?
How did you source the ACA amps? I am in the process of building them.
How are they powered? Using laptop chargers?

 

[rajan-]

Is the Pre amp connected to ACA amps?
How did you source the ACA amps? I am in the process of building them.
How are they powered? Using laptop chargers?

Yes. I use a pair of Amp Camp Amps in Bridged mono (Single ended) mode.

Ordered all the parts from diyaudiostore, and made them myself.

for now, I am using the meanwell power supplies (24V 5A) that came with the DIYAUDIO kit. These are similar to laptop power supplies. a better made brand.

I plan to make a linear power supply soon. was waiting for pre amp to be completed..


So far I have driven Amp Camps with a Firstwatt / Whammy Head Phone amp as well as Cascode version of Bride of Zen Pre amp
I dont (yet) have balanced Pre amps. to connect the Amp Camps in Balanced Mono mode.

Full Range Horn & system build

its been a sometime that I have taken up the courage to build another one after my last system. This will be a 2 channel system including horns, Amps and preamps. My previous set up: incase anyone is interested. https://www.hifivision.com/threads/2-way-speaker-build-with-horns.61352/ Time...

www.hifivision.com

this url has details of my entire system.

 

[Subbu68]

Was oscillating between F5 or Jean Hiraga Super 30. Getting the stuff especially the enclosure, tranny, PSU components and heatsinks is expensive for me. Inspired by your builds my ACA kits (2) are ordered.

Hope they'd land before the long holiday the Abu Dhabi government announced for Eid Al Fitr.

 

[rajan-]

Was oscillating between F5 or Jean Hiraga Super 30. Getting the stuff especially the enclosure, tranny, PSU components and heatsinks is expensive for me. Inspired by your builds my ACA kits (2) are ordered.

Hope they'd land before the long holiday the Abu Dhabi government announced for Eid Al Fitr.

I had very similar choices including easy accesa to hiraga boards. . Plus i also considerwd elekit models.

What swung the decision towards the ACA was simple

I had very high efficiency speakers.

Plsus wirh ACA, u can experiment between bridged mono, a balanced mono and parrell mono.


Good choice. Hope it will turn out to your expectations. Interesting to hear a tube owners perspectives on old school solid states.

 

[Subbu68]

Elekit build turned on the sleeping DIYer in me.(most household installation were still my work including PC). Now even more.....

With Klipsch Heresy IIIs or the Ahuja 12FRX ACA shouldn't have any issue i believe.

Plsus wirh ACA, u can experiment between bridged mono, a balanced mono and parrell mono.

Also it would allow me to bi-amp the Heresys if I got a miniDSP?

 

[rajan-]

Also it would allow me to bi-amp the Heresys if I got a miniDSP?

why not.

except that any sort of bridging or Balanced operation is possible at that time ?
you may have use ACA in a simple stereo mode.

Since I do not have a Bi-amp speakers, I never really thought abt it.

 

[Subbu68]

why not.

except that any sort of bridging or Balanced operation is possible at that time ?
you may have use ACA in a simple stereo mode.

Since I do not have a Bi-amp speakers, I never really thought abt it.

Bridging or balanced mode will not be possible while using in bi-amp mode. Still you have 8W of Class A each into the woofer and midrange + tweeter for each channel than just 8W into the whole 3 way network.

 

[rajan-]

before going the DSP / bi-amp route, I am hoping you would indulge in the tube pre-amp feeding Bridged mono ACA.

in any case, there are lots of possible combinations to try and enjoy. having a pair of ACA is much better than just one. there are not many choices for that kind of pedigree / performance at that price range available as a (good looking) kit.

I have read good things abt a better power supply for ACA, than the meanwell brick that comes with the kit. one of these days I need to get around to that.

 

[Subbu68]

before going the DSP / bi-amp route, I am hoping you would indulge in the tube pre-amp feeding Bridged mono ACA.

in any case, there are lots of possible combinations to try and enjoy. having a pair of ACA is much better than just one. there are not many choices for that kind of pedigree / performance at that price range available as a (good looking) kit.

I have read good things abt a better power supply for ACA, than the meanwell brick that comes with the kit. one of these days I need to get around to that.

My tube preamp is Elekit TU-8500 that has no balanced out. So have to look for one.

Meanwell for now. Planning for a proper PS later. When I go to India next, should be able to get the tranny etc. much cheaper than here in UAE.

 

[mbhangui]

My tube preamp is Elekit TU-8500 that has no balanced out. So have to look for one.

You have these interfaces which convert unbalanced to balanced and vice versa. Some of these are called direct injection boxes

https://www.amazon.in/Behringer-DI20-Professional-2-Channel-Splitter/dp/B000CCSWQA/ref=sr_1_10?crid=3AFHWEW0DZ1VE&keywords=behringer+ultra+di&qid=1651043879&sprefix=behringer+ultra+di%2Caps%2C186&sr=8-10

Some of them use high quality audio transfomers some use THAT chips.
Here is another one

Unbalanced to Balanced Converter - Plasma Music Limited

My TCI is an unbalanced to balanced converter with no gain so ideal for situations where the original signal is already +4dBu.

plasmamusic.com

THAT 12xx series of chips boast the best specs and have been widely adopted in the pro-audio world.

Balanced Input/Output Assembly Guide

Safety Precautions, Warranty, and Disclaimer Improper soldering and handling of electricity can cause serious injury and damage to your property. Read and understand the instructions below before beginning your project. Follow the instructions, build carefully, and use the appropriate tools...

www.diyrecordingequipment.com

 

[rajan-]

My tube preamp is Elekit TU-8500 that has no balanced out. So have to look for one.

Meanwell for now. Planning for a proper PS later. When I go to India next, should be able to get the tranny etc. much cheaper than here in UAE.

you can enjoy your elekit TU-8500 with a pair of ACA working in SE mode (Bridged Mono) , with 15W driving your speakers.

if you use ACA in Balanced Bridged mode, you will need balanced out from pre-amps.

this is the flexibility ACA provides.

for bridged mono ACA inputs, you can use Single ended connections.

https://cdn.shopify.com/s/files/1/1006/5046/files/ACA_Monoblock_Operation_RevA.pdf

Take a look at step 16 on the following URL for connection details.

Amp Camp Amp V1.8 Change Information

ACA V1.8

guides.diyaudio.com

this way you can enjoy 2nd harmonics with ACA operating in SE mode.

this is what I do now. I do not have balanced pre-amps now.

You have these interfaces which convert unbalanced to balanced and vice versa. Some of these are called direct injection boxes

https://www.amazon.in/Behringer-DI20-Professional-2-Channel-Splitter/dp/B000CCSWQA/ref=sr_1_10?crid=3AFHWEW0DZ1VE&keywords=behringer+ultra+di&qid=1651043879&sprefix=behringer+ultra+di%2Caps%2C186&sr=8-10

Some of them use high quality audio transfomers some use THAT chips.
Here is another one

Unbalanced to Balanced Converter - Plasma Music Limited

My TCI is an unbalanced to balanced converter with no gain so ideal for situations where the original signal is already +4dBu.

plasmamusic.com

THAT 12xx series of chips boast the best specs and have been widely adopted in the pro-audio world.

Balanced Input/Output Assembly Guide

Safety Precautions, Warranty, and Disclaimer Improper soldering and handling of electricity can cause serious injury and damage to your property. Read and understand the instructions below before beginning your project. Follow the instructions, build carefully, and use the appropriate tools...

www.diyrecordingequipment.com

any personal experience with plasma TCI ?

I was considering something like this for some time.

Since TCI does not add any gain, to fully enjoy balanced level pre outs from unbalanced RCA, either we can use a high gain preamp or add an extra gain stage (I am thinking a tube gain/buffer stage like Decware zkit 4 https://www.decware.com/newsite/diy/decware/ZKIT4.html

its possible to add a Pot to tube output stage to find ideal gain or use it like a buffer.

Unbalanced preamp out > Tube gain stage > TCI > Balanced inputs on Power amp.

 

[mbhangui]

any personal experience with plasma TCI ?

No. I have not

I was considering something like this for some time.

Since TCI does not add any gain, to fully enjoy balanced level pre outs from unbalanced RCA, either we can use a high gain preamp or add an extra gain stage (I am thinking a tube gain/buffer stage like Decware zkit 4 https://www.decware.com/newsite/diy/decware/ZKIT4.html

its possible to add a Pot to tube output stage to find ideal gain or use it like a buffer.

Unbalanced preamp out > Tube gain stage > TCI > Balanced inputs on Power amp.

It should work. What I have is a DBX 231s graphic equalizer which allows me to convert between balanced and unbalanced. It has both unbalanced and balanced input and outputs and they can be used interchangeable. The DBX also has a gain stage.

so my chain is like this

DAC output (balanced out) --> DBX 231s balanced in --> dbx 231s unbalanced out --> PASS B1 buffer preamp --> AMP.

 

[rajan-]

No. I have not

It should work. What I have is a DBX 231s graphic equalizer which allows me to convert between balanced and unbalanced. It has both unbalanced and balanced input and outputs and they can be used interchangeable. The DBX also has a gain stage.

so my chain is like this

DAC output (balanced out) --> DBX 231s balanced in --> dbx 231s unbalanced out --> PASS B1 buffer preamp --> AMP.

thanks for sharing your set up.
can I ask what Amp ? and speaker with this chain ?

also, what were the considerations for selecting DBX231 ? its not common to see pro gear in home setups that often.

now how abt a tascam DA3000 in the chain ? lol
full h/w solution. and a pretty decent DAC as well. Bonus, you can make good ( ideal for portable) recordings from pretty much any kind of source.

 

[mbhangui]

thanks for sharing your set up.
can I ask what Amp ? and speaker with this chain ?

4 amps. The outpt of the DBX actually goes to a DIY passive preamp through which I can select one of the amps below

1) Cadence VA 1 tube amp connected to Cadence Arista Electrostats. These electrostats are actually made by Siltech but manufactured here in pune. https://www.stereophile.com/news/102907siltech/index.html. The low frequency driver is from Thiel.
2) Yamaha Rx 667 AVR -- Connected to Polk Rti A9, Polk CSI A6, Polk surround speakers
3) DIY Mauro Pensa Rev C Amp - connected to the same electrostats (I manually change the speaker wires)
4) Allo class D amp. - connected to the same electrostats above (I manually change the speaker wires)

Mostly I use 1 or 2 for music. Sometimes I use 3 or 4
I;m in the process of building a speaker selector box. so fhat I don't have to manually change the speaker wires

also, what were the considerations for selecting DBX231 ?

It was a blind buy. It was listed in the sale section and I noticed that it has a gain stage with a switchable boost/cut ranges of ±6 or ±12 dB. Prior to this I was using a DIY preamp based on Rod Elliot's design with the circuit descibed here.