Synthesis The Dream 2A3 Monoblocks
 

 

Story: Client detect hum noise detect on one of the block. He further explain he already have tried to swap the tubes left to right.

Diagnosis:  Just a loose wire causing grounding hum... its on the house, client came from a long way.

Solution: Re-solder bad contact. Cost less than 1 minute for the whole scheme.

 

 
   
  Victory No.23 300B SET Amp
 
 

Story: Customer is looking for a low-cost but effective upgrade for his 300B SET amp.

Diagnosis:  After we have studied the circuit, we have found at least a few unnecessary parts in the paths, some poor arrangement and false values. The rectify stage is also sub par like many import amps, they might don't care or foreseen the importance of future possible problems. The distortion and hum is also high, which happens to most low cost amps.

Solution: Take out unnecessary parts, recalculate values and parameters, improve the rectifier stage, replace caps at key spot, as well replace with high quality James 300B output transformer.

Distortion figures has been greatly reduced as well hum noise. We are happy to hear feedback from the  customer that he thinks the sound at least improved by 60%, 50% just not high enough to grade the differences. To us, a true high end SET amp must require both good sound and good spec. This is a good example of a true low budget high end SET amp.

BEFORE

 

AFTER

 

 

   
  SOUNDTECH Preamp overhaul with TubedeForce 6922 Tube Pre
 
 

Story: A good friend of us come in with a sad face, due to a DOA preamp he purchase, see if there is anything we can help. And he certainly come to the right place.

Diagnosis:  Obviously, this manufacture has long gone out of business (Sad, because its one of our Canadian label) and does not worth to fix anything on it. So we suggest to put in our preamp to cheer him up so he have a preamp to use. We can still use the case and the transformers, fortunately we have 3-4 copies of this preamp left. This preamp circuit have been designed by us over 20 years ago, originally a project that was custom made for a radio station studio in Germany. Base on one 6922 tube each channel. As of today, we seen this same design used by several high end companies with slice changes, or adding more tubes to this original circuit.

Solution: Scrap out everything in the chassis with remaining the transformers, install our preamp PCB board, replace all in-use RCA connectors with new ones, as well replacing the old volume control with new Alps.

We are so happy to see this good-old preamp PCB board still works brilliantly as of today. The quality of the PCB is unachieved today, perhaps the best quality era has gone.

 

   
  300B SET Integrate Amp
 
 

Story: Customer report of high level of hum and powerless drive, as well seeking for possible upgrade.

Diagnosis:  After we measured the amp, with merely 5 watts and high distortion figures. We just have to turn off our customer.

Solution: This is at a point that we think is not worth to do any work on the amp.

 

   
  Eico 20 Monoblock
 

 

Story: Vintage amp from 56... customer in need of fix and circuit mod to power amp only

Diagnosis: Standard procedures...

Solution:

1/ Remove and replace the defective parts, and up grade to M-caps
2/ Waive off the line amp and phono amp. Used only the "Williamson power amp" section.
3/ Redressing the all ground loop and re-alignments all AC, balance and DC, balance, for achieving the best result

 

   
  Conrad Johnson MV51
 

 

Story: Customer reports constantly burning the El34 output tubes, and tripping the fuses.

Diagnosis: Found: 1. Bias supply circuit problem 2. Tubes socket poor connections 3. Cathode current summing amplifier had lots of wrong measures shown

Solution: This amp has seen service / modification prior, we are just putting back it in right order, along with all new tubes required.

 

   
  Electrohome PA300 Monoblocks
 

 

Customer report alot of hum and poping noise both channel

Diagnosis: 1. Found unbalance 6V6 driving power due to alot of components are getting old 2. Phase slipper had unbalanced output 3. Amp THD+N is more than 5% which is out of spec

Solution: After our service the amp result improvement to 0.3% THD at nominal output. S/N ratio is better than 85 db at rated output.

 

   
  Blue Circle Reference Tube Preamp custom external tube power supply
 
Story: A customer love this preamp so much wanted an external separated tube power supply.

Diagnosis:

Solution:

 

   
  AGAPE Audio USA Kit (2A3)
 
Story: A customer brought in this Agape kit amp that have already running 2A3 and 6SN7, but reported hums no matter how he adjust the hum pot. He is also requesting by passing the twin mono volume pots as power amp.

Diagnosis:  This amp comes in with usual problems of kits assembled by DIYer. The front end this time has been already changed to the better 6SN7, but the circuit isn't complete and some parameters is not too ideal which causes distortion and hum noise.

Solution: After we do a proof-read on the circuit adjusting the values and parameters. Then we completed the 6SN7 circuit, as well by passing the volume pots for the customer. After passing our bench test with super low distortion figures, the amp is making close to 4 healthy watts and the customer whom obsessed with 2A3/300B amp and own this amp ranked this amp top 3 of his best SET amp list.

 

   
  Custom 300 SET Amp
 
Story: A customer bring in one of this 300B amp built by a local tube guru with a pair of very expensive hand wounded output transformers in for a check up. The customer also inquire about the loud background hum thru his speakers.

Diagnosis:  This is a huge amp, that weights nearly 70 lb. But when we open up the chassis, all we saw was a mess of spaghetti that barely makes the amp just to work. We could not believe how much our customer paid for this whole "custom piece of art". This is just so wrong. We certainly feel sorry for our customer and we offered to help in overhaul the whole amplifier from our hearts. The sub par power transformer and choke are also the main cause of the hum, there even vibrations created. The rest of the scheme is also not nice. All parts and components are the worse kind of "NOS" rubbish no one can even imagine of using it, and some looks to be heavily used part from recycle bin. 

Solution: First thing we need to change is the sub par power transformer and choke, with high quality James potted 300B power transformer, as well a James potted choke. Then we reconstruct the amp in the classic circuit this amp suppose to be wired in from scratch, we just have to do that. Anything old remain have to go. This allow us to transform this to a brand new amp, a real hi end SET amp!

At last, we are so glad to see how happy the customer was when he see his "baby" to alive again.

 

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