Request : DIY PASS LAB Power Amp GroupBuy

[captrajesh]

hot you mean:lol:

Though the context here is hot, in the 'mohavra' it is cold.

captain, you seem to have dabbed in different amps in recent times, could you please give a brief overview of which ones you liked better than others

In the past 3 years, I've graduated from my good old Denon PMA 520 and have purchased / assembled the following amps: -

1. CDA 254 power amp fully assembled board from Class D Audio
2. The original My Ref power amp kit from FM Linuxguru
3. Luxman L70V vintage SS integrated amp
4. Technics SU 8022 vintage SS integrated amp
5. Acoustic Portrait tube pre and SS power amp combo.

The class D is a major step up from the Denon. It's mid range is so fluid and smooth that it is kind of addictive. I had sourced a EI core trafo locally and there was distinct lack of LF response. I have now replaced it with 420VA R core transformer and it sounds superb. The downside is, it doesn't match with all of the pre amps that you mate it with. I've mated it with a range of pre amps viz, Nakamichi, NAD 1020, Parasound JC1, AP PM1 and PassDIY B1 buffer pre. The results with the first three pre amps were disastrous. With Nakamichi, it was sounding dull; with NAD it had lumpy bass and with Parasound, it was sounding very thin. It paired well with AP pre and B1.

The original My Ref is a real VFM kit. It was a little harsh initially but later settled down nicely with good neutral presentation. However, it lacked the real low end grunt.

The Luxman was a fantastic piece of equipment. Wonderfully warm sounding with larger than life midrange and solid low end grunt. I wouldn't have gone further had this been functioning reliably. At present, it is with one of our forum members who took it fully knowing the history. I told him to pay me only if he is able to get it repaired. Till date, he hasn't been able to repair it. It is lying with him ever since.

The Technics is a decent sounding amp but is a bit bright. It's sound signature is close to that of a Marantz. I thoroughly serviced it, got the dry soldering repaired, got it repainted. It is lying on the attic at present, awaiting to be delivered to a dear friend as gift.

The Acoustic Portrait combo is the best amps that I've owned till date. The tube brings out all the little nuances of the sound, especially the midrange and the power amp takes over and delivers all of 70 watts sound which is very musical.

I intend to keep my labour of love viz the B1 Buffer and the Class D Power amps in my set up and dispose all else that I have.

 

[mbhangui]

The Acoustic Portrait combo is the best amps that I've owned till date. The tube brings out all the little nuances of the sound, especially the midrange and the power amp takes over and delivers all of 70 watts sound which is very musical.

That was a nice reading. Do you plan to replace the AP combo with something else (DIY, etc) ?

 

[jls001]

For 100 Watts think you will need mono or dual mono

You mean there is a monoblock version?

 

[kroyin]

Separate chassis,separate trafo,separate psu,separate amp board...you end up with monoblocs (or) same chassis,same 240v power supply rest separate you end up with dual mono

 

[captrajesh]

That was a nice reading. Do you plan to replace the AP combo with something else (DIY, etc) ?

Yeah, for present, I intend to pair it with the B1 buffer pre and the Class D power amp that I have.

 

[doors666]

The class D is a major step up from the Denon. It's mid range is so fluid and smooth that it is kind of addictive. I had sourced a EI core trafo locally and there was distinct lack of LF response. I have now replaced it with 420VA R core transformer and it sounds superb. The downside is, it doesn't match with all of the pre amps that you mate it with. I've mated it with a range of pre amps viz, Nakamichi, NAD 1020, Parasound JC1, AP PM1 and PassDIY B1 buffer pre. The results with the first three pre amps were disastrous. With Nakamichi, it was sounding dull; with NAD it had lumpy bass and with Parasound, it was sounding very thin. It paired well with AP pre and B1.

Well, while hunting for an amp, I was looking at the class d audio amps. Something in the specs surprised me, I think its the root cause of your problems with various preamps. The CDA 254 (and 258 and some others) have an input impedance of only 7K, which is very low and would cause issues with most sources/preamps. even my AVR has it at 47k.

 

[captrajesh]

You are absolutely correct. That is why, it can't be matched with all preamps. I've heard that the anomalies have been addressed on the later ones like SDS series (also called Super D) which even have gain control switches.

Well, while hunting for an amp, I was looking at the class d audio amps. Something in the specs surprised me, I think its the root cause of your problems with various preamps. The CDA 254 (and 258 and some others) have an input impedance of only 7K, which is very low and would cause issues with most sources/preamps. even my AVR has it at 47k.

 

[doors666]

You are absolutely correct. That is why, it can't be matched with all preamps. I've heard that the anomalies have been addressed on the later ones like SDS series (also called Super D) which even have gain control switches.

yeah but that one is a lot more expensive and balanced inputs also. I am gonna drop a mail to them and ask if they have a fix for cda. that kit sure looks interesting.
Edit: Never mind, just saw that the web is littered with this issue.

 

[cmsajith]

Sachu, Any update on the F5 Turbo group buy?

 

[sachu888]

Sachu, Any update on the F5 Turbo group buy?

Hi Sajith,
currently I am at my native place and browsing hfv from mobile,so I couldn't make much progress.I am in regular talk with Om regarding F5 design and various options for cabs.We'll surely do it soon.

Regards
Sachin

 

[GeorgeO]

Once you finalize you should plan group buys for a good cab, as well as the tranny and the heatsinks. Cosmetics are also important, and you should easily be able to negotiate good prices for a bulk quantity. I have heard Anilva's F5 a few times and was very impressed.

 

[Audiodoc]

Yes for the F5 at least assembling is the easiest part, toroids are easily available.

A good hefty chassis to handle the heat and look classy is the most difficult part followed by setting the bias.

 

[doors666]

So far the following members have expressed interest in this thread:

cmsajith
jls001
omishra
sachu888
captrajesh
mbhangui
kroyin (cab, PS)

Me, Nope, I probably will take some common parts like psu, soft start, speaker protection, trafo etc and make some other decent amp. I dont want with this monster, this is like ferrari of all amps, dont want no ferrari either.:lol:

How much power can the 100W version do into a 4 ohm load?
How much power is it supposed to waste?

To move ahead, it might be better to split this group buy into two parts, get all the electronics first and then start thinking about the chassis, heatsinks and trafos. If you guys want to finalize everything first, I am afraid we will be just discussing things for 6 months.

 

[omishra]

How much power can the 100W version do into a 4 ohm load?
How much power is it supposed to waste?

To move ahead, it might be better to split this group buy into two parts, get all the electronics first and then start thinking about the chassis, heatsinks and trafos. If you guys want to finalize everything first, I am afraid we will be just discussing things for 6 months.

no problem, but it will take time because we need our Heatsink sources ready. Then comes parts and PCB. Naturally this is slow mode as it involves running around local market. Got few sources but they are different corner of city. One has excursion so other can only cut it, other one can finsh anodizing while someone else could do tapping only.
So times and energy has to be diverted as time permits. As usual normal business for bread and butter must continue as priority 1.

 

[anm]

doors - Agree with what you said above. We may end up discussing for 6 months.
But on the other hand, we may still end up discussing for next 6 months, while the electronics just sit in the box in our home.

I am mildly interested in the group buy.

 

[sachu888]

doors - Agree with what you said above. We may end up discussing for 6 months.
But on the other hand, we may still end up discussing for next 6 months, while the electronics just sit in the box in our home.

I am mildly interested in the group buy.

I can assure you that this Gb will happen soon.It takes time to select suitable components at reasonable price,designing is another part.we(Om,Quad and myself) have exchanged hundreds of mails regarding pcb designs.It took almost one month to zeroed on big 11mfd Axon caps.Now everyone is enjoying the B1 and we built it at very cheap price too.We may split this GB in two groups
F5 - 50W
F5 - 100W

Regards
Sachin

 

[Audiodoc]

I already have the pass 5 completed PCBs and toroid waiting. I want to jump in for the heat sinks and enclosure.

 

[kroyin]

6 months is good...I intend to use the chassis & psu for F6 which hopefully would be published by then (eta was Feb 12)

 

[captrajesh]

I don't know how but when I opened my Google documents list, I found this google document listed.

It is a Bill of Materials of PassDIY F5 Turbo V2/V3 amp.

 

[sachu888]

Update

Hi,
One of my friend at Audiokarma has sent a mail to the man who first designed the F5T boards,they are good friends.His name is CViller at Diyaudio.I'll update here when he contacts me about the "Gerber files".
Else we will take permission from Nelson and make our own layout for PCBs.
Regards,
Sachin