[ProParadox]

I'm looking at building my own PPA in the near future. Stealing the component list from headsave, I was planning on using the following parts:

Tangent PPA Board
8x Elna Cerafine 470uF 25v power supply caps
Vishay/Dale 1% metal film resistors
6x Panasonic 100uF C4 caps
9x Wima 4.7uF 50v metalized polyester C2/C5 caps
10pF silver mica C6 cap
OPA 637 op-amps L & R channel (socketed)
OPA 627 op-amp G channel (socketed)
12x Intersil HA3-5002-5 buffers (socketed)

From this baseline, what can be improved upon componentry wise? I've read the diamond buffers are an excellent upgrade. The steps powersupply is supposed to be excellent, but i am not sure i want to give up such large amounts of desk space. I'd prefer my PPA to be this size. Give me your input. What component combos will give me the best sound?

 

[gsferrari]

balanced outputs

stepped attenuator

 

[Dreamslacker]

If you bend the leads a little, you could use 100uF/ 16v Elna Silmics or Cerafines for the C4 positions.
Sanyo Oscon SG series of the same value will fit without any problems.

 

[jboehle]

To improve on what you listed:

8x 220uF Black Gate FK caps instead of Elna Cerafines
6x 100uF Black Gate standard instead of Pana 100uF
-or- 6x 100uF Nichicon Muse FG caps

If you have really deep pockets, you could use Vishay S102 resistors instead of the Vishay-Dale 1%. There are also "naked" versions of the S102's available, some company I think in Oklahoma makes them specifically for audio purposes. They are not encased in the package like the S102.

And equally good but different sounding, get 3x AD8610s mounted on DIP adapters so you can swap out and try. Also, there are AP & BP versions of the OPA627/37, the BPs are supposedly higher quality, although I don't think anyone here has ever stated they can hear a difference, though - this is just FYI.

The diamond buffer is a great upgrade. Make sure with Larry first that it will fit into that Lansing case you want to use.

You didn't mention what caps you are using for C3.

You could upgrade the volume pot to a stepped attenuator instead of the Alps Blue. However, you probably wouldn't be able to fit it into that small case.

Also, why not build the STEPS power supply into the same lansing case and stack them on your desk? You wouldn't be giving up any more desk space and you would be gaining a good power supply.

-Jason

 

[ProParadox]

Quote:

Originally posted by jboehle You could upgrade the volume pot to a stepped attenuator instead of the Alps Blue. However, you probably wouldn't be able to fit it into that small case. Also, why not build the STEPS power supply into the same lansing case and stack them on your desk? You wouldn't be giving up any more desk space and you would be gaining a good power supply.

I will likely be using a hammond case, as i like them a bit better. Anyone fit stepped attenuator's in there? I kinda doubt it. I read that the stepped attenuator makes for a slight "click" when changing volume. I heard that it is also difficult to get the correct volume with it.

 

[Pars]

Quote:

Originally posted by ProParadox I will likely be using a hammond case, as i like them a bit better. Anyone fit stepped attenuator's in there? I kinda doubt it. I read that the stepped attenuator makes for a slight "click" when changing volume. I heard that it is also difficult to get the correct volume with it.

For a significant upgrade to the Alps, in the same form factor (size wise) as the Alps, use a TKD pot (Michael Percy or parts connexion). Search for a recent discussion by Morsel investigating stepped attenuators where she stumbles upon the TKD pot (they do also make stepped). I've used the pots and they are really a step up from the Alps. They run about $60 US. Only problem with these is they are solder lug, rather than board mount (although it would appear they could be modded to fit), so you would need to wire it in with short leads.

 

[Voodoochile]

What's your budget?

 

[tigger]

Quote:

Originally posted by ProParadox I'm looking at building my own PPA in the near future. Stealing the component list from headsave, I was planning on using the following parts:

LOL, were you planning to steal the parts in broad daylight, or wait for the cover of nightime?
You could improve on the list by simply dropping the sockets and soldering the buffers and op-amps directly to the board.

 

[LeasingGuy]

Quote:

Originally posted by gsferrari balanced outputs stepped attenuator

A Balanced output PPA? Anyone have one of those? Could It be built in a dual mono configuration? How far can you take the PPA design?

btw, Beautiful work Voodoochile on Seth H's amp. As soon as I recover from the 5 figure check I wrote this morning, I'll be needing one of those myself.

 

[morsel]

I don't recommend soldering ICs directly to the board as it makes it hard to change them out if you blow buffers or want to try different opamps.

The TKD CP2500 pot is discussed in this thread: stepped attenuator rotary switch mechanisms

 

[ProParadox]

Quote:

Originally posted by Voodoochile What's your budget?

As we all know, price to quality ratio runs asymptotically. What would YOU say is the price point of diminishing returns with the PPA?

 

[tangent]

Quote:

i am not sure i want to give up such large amounts of desk space

So put it on the floor. I won't think less of you for it.

Quote:

I don't think anyone here has ever stated they can hear a difference, though

The higher grade of most op-amps is only spec'd for lower offset parameters. As long as the total offset is reasonably low, this shouldn't impact sound quality at all. The high-grade version is for applications that require low offset.

If you use bass boost in your PPA, and your op-amp's low grade has fairly high offset, you might need to go with the high-grade version just to keep the bass boost from making the DC offset at the output of the amp too high. With precision op-amps like the OPA627 and AD8610, this is not an issue.

Quote:

why not build the STEPS power supply into the same lansing case

You'd have to skimp on the filter capacitance and you'd have to do something nonstandard with the heat sink. They won't fit in the thin Lansing.

Quote:

Anyone fit stepped attenuator's in there?

In a Hammond 1455N16? I haven't actually done it, but eyeballing with this DACT CT2 I have here, it looks like it'll fit.

Quote:

I read that the stepped attenuator makes for a slight "click" when changing volume.

Depends on the design of the switch it uses. Only the cheap ones use the kind of switches that make an audible click between steps.

Quote:

I heard that it is also difficult to get the correct volume with it.

Depends on the size of the attenuation steps. If they're 3dB apart, you will probably have a hard time finding a setting you like. If they're 2dB apart, you'll probably be okay. If they're 1dB apart, well, that's just wonderful, but expensive!

 

[Dreamslacker]

Quote:

Originally posted by LeasingGuy A Balanced output PPA? Anyone have one of those? Could It be built in a dual mono configuration? How far can you take the PPA design? btw, Beautiful work Voodoochile on Seth H's amp. As soon as I recover from the 5 figure check I wrote this morning, I'll be needing one of those myself.

I reckon you could build 2 PPA's with stepped attenuators. Each PPA's Left/ Right channel is used for Balanced Hot/ Cold instead. Each PPA housed in it's own box and with it's own psu. And there you have it... Dual-mono, balanced in & output.

 

[Voodoochile]

The Dact CT2 will indeed fit in the thin Lansing case... it's very snug, but makes it.

Also, regarding the steps, 23 seems to be plenty if you are careful with your gain setting. If the gain is so high that you seldom if ever listen above the 12:00 position, then you have cut your steps in half right there.

I try to have my 'comfortably loud' setting at between 2:00 and 3:00, which still gives some headroom for quiet recordings. Of course the 40-step Shallco is super nice to have, but it is about 2.5" share, and 4" deep.

 

[ProParadox]

Quote:

Originally posted by ProParadox As we all know, price to quality ratio runs asymptotically. What would YOU say is the price point of diminishing returns with the PPA?

Bump for this Q!