ea*r 660

[SUPERMAGOO]

hello.

someone been working with some vari mu pcc189 project similar to ear 660?

cheers!!

 

[bockaudio]

it's a little more complicated than one tube type. It's not like that tube is a 6386.
What's your question?

 

[ruairioflaherty]

I think Supermagoo is looking for a clone or similar type of project.  I think it's fairly well documented that a lot of the magic in Tim's designs comes from his unique transformers.  That's aside from the fact that they are in current production.....

 

[SUPERMAGOO]

it's a little more complicated than one tube type. It's not like that tube is a 6386.
What's your question?

ear660 use valves or 7es8 pcc189
is a great vari-mu compressor.
These valves are very cheap.
pcc189 costs only 10 bucks.
6386 costs 120 dollars!.
that is why I would like to develop something with that valve.

 

[SUPERMAGOO]

I think Supermagoo is looking for a clone or similar type of project. 

right!

 

[gemini86]

If it's a current production piece, it would not be a project on this forum... That said, there are plenty of other vari-mu projects on here if you look through the META, all of which are great projects.

 

[SUPERMAGOO]

If it's a current production piece, it would not be a project on this forum... That said, there are plenty of other vari-mu projects on here if you look through the META, all of which are great projects.

I appreciate your suggestion.
but I'm in this forum since 2006.
in meta section are not projects about compressors with 3 or more pcc189's.

 

[KrIVIUM2323]

Hello SUPERMAGOO, i'm being lucky to meet some EAR660 in the past (3 of them) and even more lucky to have opportunity's looking inside one of them.

In a manner it is on the 660 overall block schematic: one audio stage, one sidechain amp, one psu. The sidechain is discrete/opamp no tubes in there. Same for PSU. 

The audio stage is based around 4 pcc189 and 2 pcc188. The pcc189 are laid as 6386 in a fairchild 660 but their anode are coupled to cathode of pcc188 through some resistors. I would say it's a cascode combination of the two tube.

PCC189 are paralleled and except for grid resistors it really look like a Fairchild 660. PCC188 are paralleled too. At first i though it was a grounded cathode // pcc189 (vary mu basic design) in a pcc188 grounded grid design but it seems to me it's more in line with a cascode design.

After looking a bit with datasheets it makes sense for high gain and high bandwidth. The main problem for this particular circuit is the output transformer. How to measure it? At that time i could not go to this task with the unit i've seen (didn't know how to do this at that time anyway), but this is something i wish i had!

 

 

[jensenmann]

If you want to make anything like described before fly then you better match the PCC189 very carefully

 

[SUPERMAGOO]

Hello SUPERMAGOO, i'm being lucky to meet some EAR660 in the past (3 of them) and even more lucky to have opportunity's looking inside one of them.

In a manner it is on the 660 overall block schematic: one audio stage, one sidechain amp, one psu. The sidechain is discrete/opamp no tubes in there. Same for PSU. 

The audio stage is based around 4 pcc189 and 2 pcc188. The pcc189 are laid as 6386 in a fairchild 660 but their anode are coupled to cathode of pcc188 through some resistors. I would say it's a cascode combination of the two tube.

PCC189 are paralleled and except for grid resistors it really look like a Fairchild 660. PCC188 are paralleled too. At first i though it was a grounded cathode // pcc189 (vary mu basic design) in a pcc188 grounded grid design but it seems to me it's more in line with a cascode design.

After looking a bit with datasheets it makes sense for high gain and high bandwidth. The main problem for this particular circuit is the output transformer. How to measure it? At that time i could not go to this task with the unit i've seen (didn't know how to do this at that time anyway), but this is something i wish i had!

 

This is the kind of information I wanted to see!

but it is strange. parallel with two different tube types?.


you refer to the transformer of audio path? or a third transformer at the exit of side.chain?

 

[SUPERMAGOO]

If you want to make anything like described before fly then you better match the PCC189 very carefully

that's no problem I have a small curve tracer.
I have a friend who sold me a box with 100 pcc189 to 100 dollars.

and ... let me fly ... divagate...

 

[SUPERMAGOO]

 

[SUPERMAGOO]

http://www.mif.pg.gda.pl/homepages/frank/sheets/030/e/ECC88.pdf

 

[KrIVIUM2323]

If you want to make anything like described before fly then you better match the PCC189 very carefully

Yes this is an other problem with this kind of circuit.But it is true with every kind of dual triode design especially with varimu using // triodes.

In the pictures Supermagoo, the two big bottles are input and output transformers, the small one is the sidechain out transformer. The board with lm348 is the sidechain amp.
I was refering about the output transformer for audio path but... the small one is curious for me too...

but it is strange. parallel with two different tube types?.

Yes it's strange! I will try to explain it better: it's a cascode design so imagine you have two tube in cascode combination one lower (grounded cathode) and one upper (grounded grid). For the 'lower' tube you have 4 PCC189 parraleled, for the 'upper' one you have two pcc88 in common grid schem but the two sections of each tube are paralleled here too.

The picture you show use ECC189 and ECC88! It must be an earlyer version than the one i've seen. Appart from the heater they're the same that PCC189 and PCC88. T d P must have choose to switch ref because of difficulty of sourcing ECC as they are audiophile pricey items...

It's not so strange to have 2 different kind of tube because pcc189 is a varimu version of pcc88. So basically data are nearly the same between the two ref... Choosing a cascode configuration give the opportunity to have a massive amount of gain in the circuit which could not be possible with just a common cathode stage (a la 660) with this tubes reference (pcc189). Parralleling the tubes in the two sections of cascode help to keeping noise floor lower. I suspect the psu to be 'special' too (some kind of noiseless regulation) but my skills are poor so it's just suspicious... 

Supermagoo could you clean your pm box? I tried to send you a message yesterday and it's full.

 

[SUPERMAGOO]

You were right. had the message box completely full!
try now

 

[SUPERMAGOO]

If you want to make anything like described before fly then you better match the PCC189 very carefully

Yes this is an other problem with this kind of circuit.But it is true with every kind of dual triode design especially with varimu using // triodes.

In the pictures Supermagoo, the two big bottles are input and output transformers, the small one is the sidechain out transformer. The board with lm348 is the sidechain amp.
I was refering about the output transformer for audio path but... the small one is curious for me too...

the sidechain will be interconnected with polypropylene capacitors?

there are many!

 

[mjk]

If you want to make anything like described before fly then you better match the PCC189 very carefully

Yes this is an other problem with this kind of circuit.But it is true with every kind of dual triode design especially with varimu using // triodes.

In the pictures Supermagoo, the two big bottles are input and output transformers, the small one is the sidechain out transformer. The board with lm348 is the sidechain amp.
I was refering about the output transformer for audio path but... the small one is curious for me too...

the sidechain will be interconnected with polypropylene capacitors?

there are many!

Timing capacitors, connected in various parallel combinations to yield the 2,4,8,20 or equivalent series of cap values?

Perhaps the PCC189 has a more desirable characteristic in this service when the plate voltage is held relatively constant by the cascode. The ECC88 plates will need some well defined load resistance to set the end-to-end gain to a reasonable value (For example, the Fairchild 670 is +7 dB with no compression) .

 

[SUPERMAGOO]

If you want to make anything like described before fly then you better match the PCC189 very carefully

Yes this is an other problem with this kind of circuit.But it is true with every kind of dual triode design especially with varimu using // triodes.

In the pictures Supermagoo, the two big bottles are input and output transformers, the small one is the sidechain out transformer. The board with lm348 is the sidechain amp.
I was refering about the output transformer for audio path but... the small one is curious for me too...

the sidechain will be interconnected with polypropylene capacitors?

there are many!

Timing capacitors, connected in various parallel combinations to yield the 2,4,8,20 series of cap values?

for time constant?

but need to find fourth transformer...  :

 

[SUPERMAGOO]

Yes it's strange! I will try to explain it better: it's a cascode design so imagine you have two tube in cascode combination one lower (grounded cathode) and one upper (grounded grid). For the 'lower' tube you have 4 PCC189 parraleled, for the 'upper' one you have two pcc88 in common grid schem but the two sections of each tube are paralleled here too.

you say so?

 

[pucho812]

I got 660 schematics if anyone is interested